Prospectus Filed Pursuant to Rule 424(b)(3) (424b3)

Filed Pursuant to Rule 424(b)(3)
Registration No. 333-204209

The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities, and we are not soliciting an offer to buy these securities, in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION

PRELIMINARY PROSPECTUS SUPPLEMENT DATED NOVEMBER 7, 2017

P R E L I M I N A R Y P R O S P E C T U S S U P P L E M E N T

(To Prospectus Dated May 15, 2015)

17,000,000 Shares

LOGO

Allegheny Technologies Incorporated

Common Stock

We are offering 17,000,000 shares of our common stock, par value $0.10 per share (“common stock”). We have granted the underwriter the option to purchase up to 2,550,000 additional shares of common stock from us. See the section of this prospectus supplement entitled “Underwriting” beginning on page S-25 of this prospectus supplement.

We intend to use the net proceeds of this offering to redeem our 9.375% Senior Notes due 2019 (the “2019 Notes”) and for general corporate purposes.

Our common stock, par value $0.10 per share, is listed on the New York Stock Exchange under the trading symbol “ATI.” The last reported sale price of our common stock on the New York Stock Exchange on November 6, 2017 was $25.84 per share.

Investing in shares of common stock involves certain risks. See “ Risk Factors ” beginning on page S-9 of this prospectus supplement and the reports we file with the Securities and Exchange Commission pursuant to the Securities Exchange Act of 1934 incorporated by reference in this prospectus supplement and the accompanying prospectus to read about factors you should consider before making an investment in the shares of common stock.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the shares of common stock or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

Public offering
price

Underwriting
discount(1)

Proceeds, before
expenses, to us

Per share

Total

(1)	We refer you to “Underwriting” beginning on page S-25 of this prospectus supplement for additional information regarding total underwriting compensation.

The underwriter expects to deliver the shares to purchasers on or about November , 2017.

Sole Bookrunning Manager

Goldman Sachs & Co. LLC

November , 2017

Table of Contents


Prospectus Supplement
	Page
About This Prospectus Supplement		S-ii
Where You Can Find More Information		S-iii
Forward-Looking Statements		S-v
Summary		S-1
Risk Factors		S-9


Use of Proceeds			S-14
Common Stock Price Range and Dividend Policy			S-15
Capitalization			S-17
Description of Common Stock			S-19
Material United States Federal Income Tax Considerations			S-20
Underwriting			S-25
Legal Matters			S-32
Experts			S-32



Prospectus
About this Prospectus			i
Where You Can Find More Information			ii
Summary			1
Risk Factors			2
Forward-Looking Statements			2
Consolidated Ratios of Earnings to Fixed Charges			3
Use of Proceeds			3
Description of Debt Securities			4


Description of Other Securities			12
Description of Capital Stock			13
Plan of Distribution			17
Legal Matters			19
Experts			19

ABOUT THIS PROSPECTUS SUPPLEMENT

This document is in two parts. The first part is this prospectus supplement, which describes certain matters relating to us and this offering. The second part, the accompanying prospectus dated May 15, 2015, gives more general information about securities we may offer from time to time, some of which may not apply to the shares of common stock offered by this prospectus supplement and the accompanying prospectus. For information about our common stock, see “Description of Common Stock” in this prospectus supplement and “Description of Capital Stock — Common Stock” in the accompanying prospectus.

We are responsible for the information contained and incorporated by reference into this prospectus supplement and the accompanying prospectus and in any related free writing prospectus we prepare or authorize. We have not authorized anyone to give you any other information, and we take no responsibility for any other information that others may give you. We are not, and the underwriter is not, making an offer of our common stock in any jurisdiction where the offer or sale is not permitted. You should not assume that the information contained in this prospectus supplement, the accompanying prospectus or the documents incorporated by reference into this prospectus supplement or the accompanying prospectus is accurate as of any date other than their respective dates. Our business, financial condition, results of operations and prospects may have changed since those dates.

Before you invest in our common stock, you should carefully read this prospectus supplement and the accompanying prospectus. You should also read the documents we have referred you to under “Where You Can Find More Information” for information about us. The shelf registration statement described in the accompanying prospectus, including the exhibits thereto, can be read at the Securities and Exchange Commission’s (the “SEC”) web site or at the SEC’s Public Reference Room as described under “Where You Can Find More Information.”

If the information set forth in this prospectus supplement varies in any way from the information set forth in the accompanying prospectus, you should rely on the information contained in this prospectus supplement. If the information set forth in this prospectus supplement varies in any way from the information set forth in a document we have incorporated by reference, you should rely on the information in the more recent document.

Unless indicated otherwise, or the context otherwise requires, references in this document to “Allegheny Technologies,” “ATI,” “the Company,” “we,” “us” and “our” are to Allegheny Technologies Incorporated and its consolidated subsidiaries, and references to “dollars” and “$” are to United States dollars.

This prospectus supplement and accompanying prospectus include registered trademarks, trade names and service marks of the Company and its subsidiaries.

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WHERE YOU CAN FIND MORE INFORMATION

Available Information

We file reports, proxy statements and other information with the SEC. These reports, proxy statements and other information that we file with the SEC can be read and copied at the SEC’s Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 to obtain further information on the operation of the Public Reference Room. The SEC maintains a web site that contains reports, proxy and information statements and other information regarding issuers that file electronically with the SEC, including us. The SEC’s web site is http://www.sec.gov. In addition, our common stock is listed on the New York Stock Exchange, and our reports and other information can be inspected at the offices of the New York Stock Exchange, 20 Broad Street, New York, New York 10005. Our web site is www.atimetals.com. Information contained on our web site is not part of, and should not be construed as being incorporated by reference into, this prospectus supplement and the accompanying prospectus.

Incorporation by Reference

The SEC allows us to “incorporate by reference” information that we file with it. This means that we can disclose important information to you by referring you to other documents. Any information we incorporate in this manner is considered part of this prospectus supplement and the accompanying prospectus except to the extent updated and superseded by information contained in this prospectus supplement and the accompanying prospectus. Some information that we file with the SEC after the date of this prospectus supplement and until we sell all of the securities covered by this prospectus supplement will automatically update and supersede the information contained in this prospectus supplement and the accompanying prospectus.

We incorporate by reference the following documents that we have filed with the SEC and any filings that we make with the SEC in the future under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), until we sell all of the securities covered by this prospectus supplement, including between the date of this prospectus supplement and the date on which the offering of the securities under this prospectus supplement is terminated, except as noted in the paragraph below:


Our SEC Filings (File No. 1-12001)		Period for or Date of Filing

Annual Report on Form 10-K		Year Ended December 31, 2016
Quarterly Reports on Form 10-Q		Quarters Ended March 31, 2017, June 30, 2017 and September 30, 2017
Current Reports on Form 8-K		May 15, 2017, June 27, 2017, October 27, 2017, November 2, 2017 and November 7, 2017
Registration Statement on Form 8-A		July 30, 1996

Pursuant to General Instruction B of Form 8-K, any information submitted under Item 2.02, Results of Operations and Financial Condition, or Item 7.01, Regulation FD Disclosure, of Form 8-K is not deemed to be “filed” for the purpose of Section 18 of the Exchange Act, and we are not subject to the liabilities of Section 18 with respect to information deemed furnished (and not filed) in accordance with SEC rules, including information submitted under Item 2.02 or Item 7.01 of Form 8-K. We are not incorporating by reference any information deemed furnished (and not filed) in accordance with SEC rules, including information submitted under Item 2.02 or Item 7.01 of Form 8-K, into any filing

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under the Securities Act of 1933, as amended (the “Securities Act”), or the Exchange Act or into this prospectus supplement or the accompanying prospectus.

Statements contained in this prospectus supplement or the accompanying prospectus as to the contents of any contract, agreement or other document referred to in this prospectus supplement or the accompanying prospectus do not purport to be complete, and where reference is made to the particular provisions of that contract, agreement or other document, those references are qualified in all respects by reference to all of the provisions contained in that contract or other document. For a more complete understanding and description of each such contract, agreement or other document, we urge you to read the documents contained in the exhibits to the registration statement of which the accompanying prospectus is a part.

Any statement contained in a document incorporated by reference, or deemed to be incorporated by reference, into this prospectus supplement and the accompanying prospectus will be deemed to be modified or superseded for purposes of this prospectus supplement and the accompanying prospectus to the extent that a statement contained herein, therein or in any other subsequently filed document which also is incorporated by reference into this prospectus supplement and the accompanying prospectus modifies or supersedes that statement. Any such statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this prospectus supplement and the accompanying prospectus.

We will provide without charge, upon written or oral request, a copy of any or all of the documents that are incorporated by reference into this prospectus supplement and the accompanying prospectus and a copy of any or all other contracts, agreements or documents which are referred to in this prospectus supplement or the accompanying prospectus. Requests should be directed to: Allegheny Technologies Incorporated, 1000 Six PPG Place, Pittsburgh, PA 15222-5479, Attention: Corporate Secretary; telephone number: (412) 394-2800. You also may review a copy of the registration statement, its exhibits and the documents that are incorporated by reference into this prospectus supplement and the accompanying prospectus at the SEC’s Public Reference Room in Washington, D.C., as well as through the SEC’s web site.

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FORWARD-LOOKING STATEMENTS

You should carefully review the information contained in or incorporated by reference into this prospectus supplement and the accompanying prospectus. In this prospectus supplement and the accompanying prospectus, statements that are not reported financial results or other historical information are “forward-looking statements.” Forward-looking statements give current expectations or forecasts of future events and are not guarantees of future performance. They are based on our management’s expectations that involve a number of business risks and uncertainties, any of which could cause actual results to differ materially from those expressed in or implied by the forward-looking statements.

You can identify these forward-looking statements by the fact that they do not relate strictly to historic or current facts. They use words such as “anticipates,” “believes,” “estimates,” “expects,” “would,” “should,” “will,” “will likely result,” “forecast,” “outlook,” “projects,” and similar expressions in connection with any discussion of future operating or financial performance.

We cannot guarantee that any forward-looking statements will be realized, although we believe that we have been prudent in our plans and assumptions. Achievement of future results is subject to risks, uncertainties and assumptions that may prove to be inaccurate. Among others, the factors discussed in the “Risk Factors” section of our Annual Report on Form 10-K for our fiscal year ended December 31, 2016, as updated by the section entitled “Part II – Item 1A Risk Factors” in our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2017, June 30, 2017, and September 30, 2017 or under “Risk Factors” in this prospectus supplement could cause actual results to differ from those in forward-looking statements included in or incorporated by reference into this prospectus supplement and the accompanying prospectus or that we otherwise make. Important factors that could cause actual results to differ materially from those in the forward-looking statements include: (a) material adverse changes in economic or industry conditions generally, including global supply and demand conditions and prices for our specialty metals; (b) material adverse changes in the markets we serve; (c) our inability to achieve the level of cost savings, productivity improvements, synergies, growth or other benefits anticipated by management from strategic investments and the integration of acquired businesses; (d) volatility in the price and availability of the raw materials that are critical to the manufacture of our products; (e) declines in the value of our defined benefit pension plan assets or unfavorable changes in laws or regulations that govern pension plan funding; (f) labor disputes or work stoppages; (g) equipment outages and (h) other risk factors summarized in our Annual Report on Form 10-K for the year ended December 31, 2016, as updated by the section entitled “Part II – Item 1A Risk Factors” in our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2017, June 30, 2017, and September 30, 2017, and in other reports filed with the Securities and Exchange Commission. Should known or unknown risks or uncertainties materialize, or should underlying assumptions prove to be inaccurate, actual results could vary materially from those anticipated, estimated or projected. You should bear this in mind as you consider any forward-looking statements.

We undertake no obligation to publicly update forward-looking statements, whether as a result of new information, future events or otherwise, except as may be required by law. You are advised, however, to consider any additional disclosures that we may make on related subjects in future filings with the SEC. You should understand that it is not possible to predict or identify all factors that could cause our actual results to differ. Consequently, you should not consider any list of factors to be a complete set of all potential risks or uncertainties.

S-v

SUMMARY

This summary highlights information about us and the common stock being offered by this prospectus supplement and the accompanying prospectus. This summary is not complete and may not contain all of the information that you should consider prior to investing in our common stock. For a more complete understanding of our company, we encourage you to read this entire document, including the information incorporated by reference into this document.

Our Company

We are a global manufacturer of technically advanced specialty materials and complex components. Approximately 50% of our sales are to the aerospace & defense market, particularly jet engines, and we have a strong presence in the oil & gas, electrical energy, medical, automotive and other industrial markets. We are a market leader in manufacturing differentiated products that require our unique manufacturing and precision machining capabilities as well as our innovative new product development competence. Our capabilities range from alloy development through final production of highly engineered finished components. We are a leader in producing powders for use in next-generation jet engine forgings and 3D-printed aerospace products.

Our strategic vision is to be an aligned and integrated specialty materials and components company. Our strategies target the products and global growth markets that require and value our technical and manufacturing capability leadership. These differentiated products serve key global markets including aerospace & defense, oil & gas, electrical energy, medical and automotive, and sales to these key global markets represented approximately 80% of our total sales in both the year ended December 31, 2016 and the nine months ended September 30, 2017.

We operate in two business segments: High Performance Materials & Components (“HPMC”), and Flat Rolled Products (“FRP”). Our HPMC segment produces, converts and distributes a wide range of high performance materials, including titanium and titanium-based alloys, nickel- and cobalt-based alloys and superalloys, zirconium and related alloys including hafnium and niobium, advanced powder alloys and other specialty materials, in long product forms such as ingot, billet, bar, rod, wire, shapes and rectangles, and seamless tubes, plus precision forgings, castings, components and machined parts. These products are designed for the high performance requirements of major end markets such as aerospace & defense, oil & gas, electrical energy and medical. We are integrated across these alloy systems in melt, remelt, mill product forging, finishing, investment casting and machining processes. Most of the products in this segment are sold directly to end-use customers, and a significant portion of our HPMC segment products are sold under multi-year agreements.

Approximately 75% of our HPMC segment’s sales in both the year ended December 31, 2016 and the nine months ended September 30, 2017 were to the aerospace & defense market, led by products for commercial aerospace jet engines. Through acquisitions, alloy development, internal growth strategies and long-term supply agreements on current and next-generation aero-engines and airframes, we are well positioned with a fully qualified asset base to meet the expected multi-year growth in demand from the commercial aerospace market. Our HPMC segment’s isothermal and hot-die forge press utilization continues to improve to meet aerospace demand growth, including new market share gains.

Our FRP segment produces, converts and distributes stainless steel, nickel-based alloys, specialty alloys and titanium and titanium-based alloys, in a variety of product forms including plate,

S-1

sheet, engineered strip and Precision Rolled Strip ^® products. The major end markets for our flat-rolled products are oil & gas, automotive, aerospace & defense, food processing equipment and appliances, construction and mining, electronics, communication equipment and computers. We expect sales in the oil & gas end market to recover in the next several years. The operations in this segment are ATI Flat Rolled Products and the Chinese joint venture company known as Shanghai STAL Precision Stainless Steel Company Limited (“STAL”), in which we hold a 60% interest. Segment results also include our 50% interest in the industrial titanium joint venture known as Uniti LLC.

Additionally, on November 2, 2017, we announced our definitive agreement with the vertically-integrated, multi-national stainless steel producer, Tsingshan Holding Group Co., Ltd. (“Tsingshan”), to form a new, 50-50 joint venture, Allegheny & Tsingshan Stainless, for the manufacture and sale of 60 inch-wide flat-rolled stainless steel products in North America. ATI’s FRP segment will hot-roll stainless steel slab produced by Tsingshan into coils on our Hot Rolling and Processing Facility (“HRPF”) under a conversion agreement with the new joint venture, which then will finish the coils into stainless steel sheet using our previously-idled Direct Roll Anneal and Pickle (“DRAP”) facility in Midland, Pennsylvania, the ownership of which will be transferred to the new joint venture in connection with its formation. Beginning in 2018, FRP segment results will also include the results of our 50% interest in Allegheny & Tsingshan Stainless, as well as conversion services to the joint venture utilizing our innovative, low-cost HRPF, assuming formation of the new joint venture as planned, which remains subject to customary closing conditions, including regulatory and anti-trust clearances.

Our common stock is quoted on the New York Stock Exchange under the symbol “ATI.”

Our Strengths

We believe that we are well-positioned for long-term growth, profitability and cash flow generation as a result of numerous factors, including:

Leading Diversified Specialty Materials and Components Producer . We are a world leader in the manufacture of both high-value and commodity specialty materials and component products and have one of the most diversified product offerings in the specialty metals industry. We believe that our size, market position and technical and manufacturing capabilities, including operating the HRPF, which is one of the world’s most powerful hot-rolling mills for steel and specialty metals, enable us to more effectively serve the needs of our customers, further improve our cost structure through economies of scale, and position us to profitably grow our business on a long-term basis.

Diverse End Markets . Our differentiated products serve key global markets, including aerospace and defense, oil & gas, electrical energy, medical and automotive. In the aerospace industry, we are a world leader in the production of premium titanium alloys, nickel-based and cobalt-based alloys and superalloys, and vacuum-melted specialty alloys used in the manufacture of components for both commercial and military jet engines, as well as replacement parts for those engines. We also produce titanium alloys, vacuum-melted specialty alloys, and high-strength stainless alloys for use in commercial and military airframes, airframe components and missiles. Both of our business segments produce specialty materials that are widely used in the oil & gas industry including chemical & hydrocarbon processing. Our specialty materials are also widely used in the automotive and global electrical power generation industries, as well as in various medical device products.

High Value-Added Product Offering and Strong Competitive Position . Our specialty materials are produced in a wide range of alloys and product forms and are selected for use in

S-2

applications that demand materials having exceptional hardness, toughness, strength, resistance to heat, corrosion or abrasion, or a combination of these characteristics. We have continued our strategic focus on high-value, differentiated products, which accounted for approximately 85% and 83% of our sales in the year ended December 31, 2016 and the nine months ended September 30, 2017, respectively.

Close, Long Standing Relationships with Blue-Chip Customers . We believe that our focus on providing high quality products to our customers has led to long standing relationships with many of the industry leaders in the end markets we serve. We believe that we have an excellent reputation with our customers for providing high quality products and customer service, as well as for timely delivery. In the past several years, we have entered into long-term agreements (“LTAs”) with certain of our customers for our specialty materials, in the form of mill products and components, to reduce their supply uncertainty, including several LTAs with aerospace market original equipment manufacturers. These LTAs are for our specialty materials mill products, forgings and investment castings required for both next-generation and legacy aircraft platforms. Our aerospace customers include, among others, The Boeing Company, Airbus S.A.S. (an Airbus Group company), Bombardier Aerospace (a division of Bombardier Inc.), and Embraer (Empresa Brasileira de Aeronáutica S.A.) for airframes, and GE Aviation (a division of General Electric Company), Rolls-Royce plc, Pratt & Whitney (a division of United Technologies Corporation), Snecma (SAFRAN Group) and various joint ventures that manufacture jet engines.

Experienced, Committed Management Team . Our business is managed by an experienced team of executive officers led by Richard J. Harshman, our Chairman, President and Chief Executive Officer. Our management team includes many other experienced officers in key functional areas, including technical, operations, sales, marketing, accounting, finance and legal. Our executive officers and other members of our management team are committed to growing our business, reducing costs, and pursuing other initiatives to deliver sustained growth in earnings and cash flow generation.

Business Strategy

We intend to build upon our competitive strengths to continue our growth through the execution of our focused business strategy.

Capitalize on Future Growth in Our Key End Markets . We define the key markets in which we operate as the aerospace and defense, oil & gas, electrical energy, automotive and medical industries. Our participation in the aerospace and defense industry has expanded significantly in recent years, from approximately 25% of our sales in 2010 to over 50% in 2016, as we believe we are a strategic supplier to the airframe and engine original equipment manufacturers with deep product and technological knowledge. We have LTAs that secure significant growth on both legacy and next-generation models. The commercial aerospace market is transitioning to the next generation of single aisle and large twin aisle aircrafts, and next-generation jet engines. New airframe designs contain a larger percentage of titanium alloys, and the jet engines that power them use newer nickel-based alloys and titanium-based alloys, in both cases for improved performance and more economical operating costs, compared to legacy airframe and engine designs. Approximately 40% of our HPMC segment’s sales to the jet engine market for the nine months ended September 30, 2017 were products for next-generation commercial jet engines.

Continuously Seek to Innovate and Develop . We maintain our commitment to develop innovative alloys to better serve the needs of our end market users. ATI’s 718Plus ^® nickel-based superalloy, Rene 65 near-powder superalloy (developed with GE), and our powder alloys have won

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significant share in the current and next-generation engines for the aerospace and defense market. Additionally, both of our business segments produce specialty materials that are widely used in to the oil & gas industry. Our specialty materials, including titanium and titanium alloys, nickel-based alloys, zirconium alloys, stainless and duplex alloys and other specialty alloys, have the strength and wear corrosion-resistant properties necessary for difficult environments.

Maintain Emphasis on Continuous Operational Improvement . We have made significant operational progress in qualifying and fully integrating long-term strategic capital projects that we believe will position us to grow our high-value product offerings, including most recently the ongoing qualifications at our new nickel-alloy powder production facility in Bakers, North Carolina. Additionally, our recent rightsizing and restructuring initiatives are showing positive impacts in improving future financial performance in both the HPMC and FRP business segments. Our 2016 actions in the HPMC segment included restructuring our titanium operations to improve cost competitiveness, which involved, among other measures, the indefinite idling of the Rowley, Utah titanium sponge production facility. In our FRP segment, our focus on value, not volume, including the exit from the grain-oriented electrical steel market has had a positive impact on that business, as we focus on the products and global markets that value our technical leadership and manufacturing capability.

Expand Our Global Presence . Approximately 41% of our sales in both the year ended December 31, 2016 and the nine months ended September 30, 2017 came from markets outside the United States in which we believe we have attractive growth prospects. Additionally, we believe that at least 50% of our sales in the these periods were driven by global markets when we consider exports of our customers. Our HPMC segment has manufacturing capabilities for melting, remelting, forging and finishing nickel-based alloys and specialty alloys in the United Kingdom, and manufacturing capabilities for precision forging and machining in Poland, primarily serving the construction, transportation and aerospace and oil & gas markets. Within our FRP segment, our STAL joint venture in the People’s Republic of China produces Precision Rolled Strip ^® products, which enables us to offer these products more effectively to markets in China and other Asian countries. Our Uniti LLC joint venture allows us to offer titanium products to industrial markets more effectively worldwide, and our recently-announced joint venture with multi-national producer Tsingshan is expected to be a cost-competitive supplier of commodity stainless products for the North American market.

Preserve Liquidity Position and Engage in Proactive Liability Management . We seek to maintain a conservative balance sheet and believe that we have sufficient liquidity to fully support our daily operations. As of September 30, 2017, we had approximately $125 million of cash and cash equivalents, and we have available liquidity of approximately $280 million under our existing senior secured credit facility (the “Credit Facility”). After giving effect to this offering and the application of the proceeds from this offering as described under the caption “Use of Proceeds”, we will have no significant debt maturities until 2021. In 2016, we issued $287.5 million aggregate principal amount of six-year convertible senior notes and subsequently contributed $250.0 million to the ATI Pension Plan, our U.S. qualified defined benefit pension plan. From 2014 to 2016, we made several significant changes to our retirement benefit programs, including a 2016 labor agreement with a majority of employees represented by the USW, which includes important changes to retirement benefit programs, including a freeze to new entrants to the ATI Pension Plan and the elimination of retiree medical benefits for new employees. Additionally, we implemented a hard freeze to all future pension benefit accruals to the ATI Pension Plan for all non-represented employees at the end of 2014. In 2016, we

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divested approximately 3,700 retirees from the ATI Pension Plan through an annuity buyout. We believe that these benefit changes and liability management actions will favorably impact our results of operations in future years.

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The Offering

The following summary is provided solely for your convenience and is not intended to be complete. You should read the full text and more specific details contained elsewhere in this prospectus supplement and the accompanying prospectus. For purposes of this “offering summary,” references to “Allegheny Technologies Incorporated,” “we,” “our” and “us” refer only to Allegheny Technologies Incorporated and not its subsidiaries. For a more detailed description of our common stock, see “Description of Common Stock” in this prospectus supplement and “Description of Capital Stock — Common Stock” in the accompanying prospectus.

Issuer

Allegheny Technologies Incorporated, a Delaware corporation

Securities Offered

17,000,000 shares of common stock

Offering Price

per share

Common stock outstanding after the offering

125,863,099 shares (or 128,413,099 shares if the underwriter exercises its option to purchase additional shares in full).

Underwriter’s option

We have granted the underwriter a 30-day option to purchase up to an additional 2,550,000 shares of common stock at the public offering price, less the underwriting discounts and commissions.

Use of Proceeds

We intend to use the net proceeds from this offering to redeem the 2019 Notes, including the payment of the associated redemption premium, and for general corporate purposes. See “Use of Proceeds.”

Trading Symbol for Our Common Stock

Our common stock is listed on the New York Stock Exchange, or NYSE, under the symbol “ATI.”

Risk Factors

You should carefully consider the information set forth in the section entitled “Risk Factors” and the other information included or incorporated by reference into this prospectus supplement and the accompanying prospectus in deciding whether to purchase the notes.

Transfer Agent and Registrar

Computershare Investor Services

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Summary Consolidated Financial Data

We derived the summary consolidated financial data shown below as of December 31, 2014, 2015 and 2016 and for each of the years then ended from our audited consolidated financial statements. We derived the summary consolidated financial data as of September 30, 2017 and 2016 and for each of the nine month periods then ended from our unaudited consolidated financial statements. The unaudited financial statements from which we derived this data were prepared on the same basis as the audited consolidated financial data and include all adjustments, consisting only of normal recurring adjustments, necessary to present fairly our results of operations and financial condition as of the periods presented. The results of operations for interim periods are not necessarily indicative of the operating results for any future period. You should read the following financial information in conjunction with “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and our consolidated financial statements and the related notes in our Annual Report on Form 10-K for the fiscal year ended December 31, 2016 and our Quarterly Report on Form 10-Q for the fiscal quarter ended September 30, 2017, which are incorporated by reference into this prospectus supplement and the accompanying prospectus.


	Year Ended December 31,						Nine Months Ended September 30,
	2014		2015		2016		2016		2017
	(In millions except per share amounts)
							(Unaudited)
Statement of income data:
Sales	$	4,223.4	$	3,719.6	$	3,134.6	$	2,338.5	$	2,615.2
Cost of sales		3,844.8		3,659.3		2,972.1		2,273.3		2,296.8

Gross profit		378.6		60.3		162.5		65.2		318.4
Income (loss) from continuing operations		10.2		(365.9)		(627.1)		(640.8)		(84.9)
Income (loss) from discontinued operations, net of tax		(0.6)		—		—		—		—

Net income (loss)		9.6		(365.9)		(627.1)		(640.8)		(84.9)
Less: Net income attributable to noncontrolling interests		12.2		12.0		13.8		10.0		8.7

Net loss attributable to ATI	$	(2.6)	$	(377.9)	$	(640.9)		(650.8)	$	(93.6)


Basic net income (loss) attributable to ATI per common share:
Continuing operations per common share	$	(0.02)	$	(3.53)	$	(5.97)	$	(6.07)	$	(0.87)
Discontinued operations per common share		(0.01)		—		—		—		—

Total	$	(0.03)	$	(3.53)	$	(5.97)	$	(6.07)	$	(0.87)

Weighted average shares used in computing net income (loss) attributable to ATI per common share, basic		107.1		107.3		107.3		107.3		107.7

Diluted net income (loss) attributable to ATI per common share:
Continuing operations per common share	$	(0.02)	$	(3.53)	$	(5.97)	$	(6.07)	$	(0.87)
Discontinued operations per common share		(0.01)		—		—		—		—

Total	$	(0.03)	$	(3.53)	$	(5.97)	$	(6.07)	$	(0.87)

Weighted average shares used in computing net income (loss) attributable to ATI per common share, diluted		107.1		107.3		107.3		107.3		107.7

Other data:
EBITDA (unaudited) (1)	$	287.0	$	(177.9)	$	(439.7)	$	(483.8)	$	136.0
Adjusted EBITDA (unaudited) (1)	$	262.0	$	3.2	$	31.6	$	(12.5)	$	250.4

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(1)

We define EBITDA as income (loss) from continuing operations before interest and income taxes, plus depreciation and amortization. We define Adjusted EBITDA as EBITDA excluding significant non-cash charges or credits, including goodwill impairment charges, restructuring charges including long-lived asset impairments, and OPEB/pension curtailment and settlement gains and losses. EBITDA and Adjusted EBITDA are not measures of financial performance under U.S. generally accepted accounting principles. EBITDA and Adjusted EBITDA are not calculated in the same manner by all companies and, accordingly, are not necessarily comparable to similarly titled measures of other companies and may not be an appropriate measure of performance relative to other companies. We have presented EBITDA and Adjusted EBITDA in this prospectus supplement solely as a supplemental disclosure because we believe it allows for a more complete analysis of our results of operations. We believe that EBITDA and Adjusted EBITDA are useful to investors because these measures are commonly used to analyze companies on the basis of operating performance, leverage and liquidity. Furthermore, analogous measures are used by industry analysts to evaluate operating performance. EBITDA and Adjusted EBITDA are not intended to be measures of free cash flow for management’s discretionary use, as they do not consider certain cash requirements such as interest payments, tax payments and capital expenditures. EBITDA and Adjusted EBITDA are not intended to represent, and should not be considered more meaningful than, or as an alternatives to, a measure of operating performance as determined in accordance with U.S. generally accepted accounting principles. The definitions of EBITDA and Adjusted EBITDA will differ from the amounts calculated under the definition of Consolidated EBITDA that is contained in the Credit Facility. We do not intend to provide EBITDA or Adjusted EBITDA information for future periods in earnings press releases, filings with the SEC or in response to inquiries. EBITDA and Adjusted EBITDA are calculated as follows:


	Year Ended December 31,						Nine Months Ended September 30,
	2014		2015		2016		2016		2017
	(Dollars in Millions)
	(Unaudited)
Income (loss) from continuing operations before interest and income taxes	$	110.2	$	(367.8)	$	(610.0)	$	(614.0)	$	15.3
Depreciation and amortization		176.8		189.9		170.3		130.2		120.7

EBITDA	$	287.0	$	(177.9)	$	(439.7)	$	(483.8)	$	136.0

Impairment of goodwill ^(a)		—		126.6		—		—		114.4
Restructuring charges ^(b)		—		54.5		471.3		471.3		—
OPEB/pension curtailment gain ^(c)		(25.0)		—		—		—		—

Adjusted EBITDA	$	262.0	$	3.2	$	31.6	$	(12.5)	$	250.4

(a)

Goodwill impairment for the year ended December 31, 2015 was $126.6 million for the Flat Rolled Products business in the FRP segment, as disclosed in Note 6 to our audited consolidated financial statements in the 2016 Annual Report on Form 10-K. In the nine months ended September 30, 2017, goodwill impairment was $114.4 million for the Cast Products business in the HPMC segment, as disclosed in Note 4 to our unaudited consolidated financial statements in the Third Quarter 2017 Quarterly Report on Form 10-Q.

(b)

Restructuring charges for the year ended December 31, 2015 were $54.5 million for long-lived asset impairments in the FRP segment, including the Midland, PA standard stainless melt shop and sheet finishing operations, and the grain-oriented electrical steel operations including the Bagdad, PA facility, as disclosed in Note 17 to our audited consolidated financial statements in the 2016 Annual Report on Form 10-K. Restructuring charges for nine months ended September 30, 2016 and the year ended December 31, 2016 were $471.3 million for long-lived asset impairment of the Rowley, UT titanium sponge production facility of the HPMC segment, as disclosed in Note 17 to our audited consolidated financial statements in the 2016 Annual Report on Form 10-K.

(c)

OPEB/pension curtailment gain of $(25.0) million for 2014 relates to the elimination of all Company-provided salaried retiree life insurance benefits and all remaining Company-provided salaried retiree medical benefits, as disclosed in Note 12 to our audited consolidated financial statements in the 2016 Annual Report on Form 10-K.

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RISK FACTORS

Investing in our common stock involves risks. You should carefully read and consider the risks described below as well as the risks described in the sections entitled “Item 1. Business” and “Item 1A. Risk Factors” in our Annual Report on Form 10-K for the year ended December 31, 2016, as updated by the section entitled “Part II – Item 1A Risk Factors” in our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2017, June 30, 2017 and September 30, 2017, which are incorporated by reference into this prospectus supplement and the accompanying prospectus. You should also carefully read and consider the other information contained in or incorporated by reference into this prospectus supplement and the accompanying prospectus, including risks described above in “Forward-Looking Statements,” before making a decision to invest our common stock. Each of these risks could materially and adversely affect our business, financial condition, results of operations, liquidity and prospects, and could result in a partial or complete loss of your investment.

Risks Relating to this Offering

The market price of our common stock may continue to be volatile and will be affected by factors beyond our control, which could affect the short-term value of your investment.

The market price of our common stock has been and may continue to be subject to significant fluctuations due not only to general stock market conditions but also to changes in sentiment in the market regarding our operations, business prospects, liquidity or this offering. During the period from January 1, 2016 to October 31, 2017, our common stock has fluctuated from a high of $25.62 per share to a low of $7.08 per share. The market price of our common stock will likely continue to fluctuate in response to, among other things, the factors discussed under “Item 1. Business” and “Item 1A. Risk Factors” in our Annual Report on Form 10-K for the year ended December 31, 2016 as updated by “Part II – Item 1A Risk Factors” in our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2017, June 30, 2017 and September 30, 2017, which is incorporated by reference into this prospectus supplement and the accompanying prospectus.

Our substantial indebtedness could adversely affect our business, financial condition or results of operations and prevent us from fulfilling our obligations under our outstanding indebtedness.

We currently have and, after this offering, will continue to have a significant amount of indebtedness. As of September 30, 2017, after giving effect to this offering and the application of the proceeds from this offering as described under the caption “Use of Proceeds”, our total consolidated indebtedness would have been approximately $1.6 billion (excluding accounts payable, accrued expenses, other liabilities and unfunded commitments). This substantial level of indebtedness increases the risk that we may be unable to generate enough cash to pay amounts due in respect of our indebtedness.

Our substantial indebtedness could have important consequences to you and significant effects on our business. For example, it could:

•

make it more difficult for us to satisfy our obligations with respect to our outstanding indebtedness;

•

increase our vulnerability to general adverse economic and industry conditions;

•

require us to dedicate a substantial portion of our cash flow from operations to payments on our indebtedness, thereby reducing the availability of our cash flow to fund working capital, capital expenditures, our strategic growth initiatives and development efforts and other general corporate purposes;

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•

limit our flexibility in planning for, or reacting to, changes in our business and the industry in which we operate;

•

restrict us from exploiting business opportunities;

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place us at a competitive disadvantage compared to our competitors that have less indebtedness; and

•

limit our ability to borrow additional funds for working capital, capital expenditures, acquisitions, debt service requirements, execution of our business strategy or other general corporate purposes.

In addition, the agreements that govern our current indebtedness contain, and the agreements that may govern any future indebtedness that we may incur may contain, financial and other restrictive covenants that will limit our ability to engage in activities that may be in our long-term best interests. Our failure to comply with those covenants could result in an event of default that, if not cured or waived, could result in the acceleration of all of our debt.

Despite our substantial current indebtedness, we and our subsidiaries may still be able to incur substantially more indebtedness. This could further exacerbate the risks associated with our substantial leverage.

We and our subsidiaries may be able to incur substantial additional indebtedness in the future, including pursuant to a capital markets transaction such as a notes offering, as well as additional secured indebtedness, each of which would have priority in a liquidation, dissolution or winding up over our shares of common stock. Adding new indebtedness to current debt levels could make it more difficult for us to satisfy our obligations to holders of our indebtedness.

Rights of any future preferred stockholders may dilute the voting power or reduce the value of our common shares.

Our Restated Certificate of Incorporation authorizes us to issue, without the approval of our stockholders, one or more classes or series of preferred shares having such designation, powers, preferences and relative, participating, optional and other special rights, including preferences over our common shares respecting dividends and voting rights, as our board of directors generally may determine. The terms of one or more classes or series of preferred shares could dilute the voting power or reduce the value of our common shares. For example, we could grant holders of preferred shares the right to veto specified transactions on the happening of specified events. Similarly, the repurchase or redemption rights or liquidation preferences we could assign to holders of preferred shares could affect the residual value of the common shares. As of the date of this prospectus supplement, we do not have any outstanding shares of preferred stock.

All of our debt obligations, and any future indebtedness we may incur, will have priority over our shares with respect to payment in the event of a liquidation, dissolution or winding up.

In any liquidation, dissolution or winding up of the Company, our shares of common stock would rank below all debt claims against us. In addition, any convertible or exchangeable securities or other equity securities (including preferred shares) that we may issue in the future may have rights, preferences and privileges more favorable than those of our shares of common stock. Our share capital includes 50,000,000 authorized (but currently unissued) shares of preferred stock. As a result, holders of shares of our common stock will not be entitled to receive any payment or other distribution of assets upon the liquidation or dissolution until after our obligations to our debt holders and holders of equity securities that rank senior to shares of our common stock have been satisfied.

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Sales of a substantial amount of shares of our common stock in the public market, particularly sales by our directors, executive officers and significant stockholders, or the perception that these sales could occur, could cause the market price of our common stock to decline and may make it more difficult for you to sell your common stock at a time and price that you deem appropriate.

As of September 30, 2017, after giving effect to this offering (without giving effect to any additional shares issuable if the underwriter’s option to purchase additional shares is exercised), there would have been 125,863,099 shares of our common stock outstanding, which will be freely transferable without restriction or further registration under the federal securities laws, except for any shares held by our affiliates, sales of which will may limited by Rule 144 under the Securities Act.

We and our executive officers and directors have entered into lock-up agreements with the underwriter under which we and they have agreed, subject to specific exceptions, not to sell, contract to sell or otherwise dispose of any of our common shares or securities that are convertible or exchange for our common shares or entering into any arrangement that transfers the economic consequences of ownership of our common shares without the permission of Goldman Sachs & Co. LLC for a period of 90 days following the date of this prospectus. We refer to such period as the lock-up period. When the lock-up period expires, we and our securityholders subject to a lock-up agreement will be able to sell our shares in the public market. In addition, Goldman Sachs & Co. LLC may, in its sole discretion, release all or some portion of the shares subject to lock-up agreements at any time and for any reason. Sales of a substantial number of such shares upon expiration of the lock-up agreements, the perception that such sales may occur, or early release of these agreements, could cause our market price to fall or make it more difficult for you to sell your common stock at a time and price that you deem appropriate.

We may issue additional shares of our common stock or instruments convertible into our common stock, including in connection with conversions of notes, and thereby materially and adversely affect the price of our common stock.

Subject to lock-up provisions described under “Underwriting,” we are not restricted from issuing additional shares of our common stock or other instruments convertible into our common stock. See “Underwriting.” We cannot predict the size of future issuances or the effect, if any, that they may have on the market price for our common stock. If we issue additional shares of our common stock or instruments convertible into our common stock, it may materially and adversely affect the price of our common stock. Furthermore, the conversion of some or all of our existing convertible notes may dilute the ownership interests of existing stockholders, and any sales in the public market of shares of our common stock issuable upon any such conversion could adversely affect prevailing market prices of our common stock. In addition, the anticipated issuance and sale of substantial amounts of common stock or the anticipated conversion or exercise of securities into shares of our common stock could depress the price of our common stock.

If securities analysts or industry analysts publish negative research or reports, or do not publish reports about our business, our share price and trading volume could decline.

The trading market for our common shares is influenced by the research and reports that industry or securities analysts publish about us, our business and our industry. If one or more analysts adversely change their recommendation regarding our shares or our competitors’ stock, our share price would likely decline. If one or more analysts cease coverage of us or fail to regularly publish reports on us, we could lose visibility in the financial markets, which in turn could cause our share price or trading volume to decline.

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Provisions in our corporate documents and Delaware law could have the effect of delaying, deferring or preventing a change in control of us, even if that change may be considered beneficial by some of our stockholders.

The existence of some provisions of our Restated Certificate of Incorporation, our Third Amended and Restated Bylaws and Delaware law could have the effect of delaying, deferring or preventing a change in control of us that a stockholder may consider favorable. These provisions are more fully described under “Description of Capital Stock” in the accompanying prospectus.

We believe these provisions protect our stockholders from coercive or otherwise unfair takeover tactics by requiring potential acquirors to negotiate with our board of directors and by providing our board of directors with more time to assess any acquisition proposal, and are not intended to make our company immune from takeovers. However, these provisions apply even if the offer may be considered beneficial by some stockholders and could delay, defer or prevent an acquisition that our board of directors determines is not in the best interests of our company and our stockholders.

Our actual operating results may differ significantly from our guidance.

From time to time, we release guidance regarding our future performance. This guidance, which consists of forward-looking statements, is prepared by our management and is qualified by, and subject to, the assumptions and the other information included in or incorporated by reference into this prospectus supplement and the accompanying prospectus and included in our Annual Report on Form 10-K for the year ended December 31, 2016, as updated by the section entitled “Part II – Item 1A Risk Factors” in our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2017, June 30, 2017, and September 30, 2017, as well as the factors described under “Forward-Looking Statements” in this prospectus supplement. Neither our independent registered public accounting firm nor any other independent or outside party compiles or examines the guidance, and, accordingly, no such person expresses any opinion or any other form of assurance with respect thereto.

Guidance is based upon a number of assumptions and estimates that, while presented with numerical specificity, are inherently subject to business, economic and competitive uncertainties and contingencies, many of which are beyond our control and are based upon specific assumptions with respect to future business decisions, some of which will change. The principal reason that we release this data is to provide a basis for our management to discuss our business outlook with analysts and investors. We do not accept any responsibility for any projections or reports published by any such persons.

Guidance is necessarily speculative in nature, and it can be expected that some or all of the assumptions of the guidance furnished by us will not materialize or will vary significantly from actual results. Accordingly, our guidance is only an estimate of what management believes is realizable as of the date of release. Actual results will vary from the guidance. Investors should also recognize that the reliability of any forecasted financial data diminishes the farther in the future that the data is forecast. In light of the foregoing, investors are urged to put the guidance in context and not to place undue reliance on it.

Any failure to successfully implement our operating strategy or the occurrence of any of the events or circumstances set forth in, or incorporated by reference into, this prospectus supplement could result in actual operating results being different than the guidance, and such differences may be adverse and material.

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As a new investor, you will experience immediate and substantial dilution in the net tangible book value of your shares.

The offering price of our common stock in this offering is considerably more than the net tangible book value per share of our outstanding common stock. Accordingly, investors purchasing shares of our common stock in this offering will pay a price per share that substantially exceeds the book value of our assets after subtracting liabilities. In addition, to the extent that we issue additional shares in the future pursuant to stock options or otherwise, you may experience further dilution.

S-13

USE OF PROCEEDS

We estimate that the net proceeds from this offering will be approximately $ million (or approximately $ million if the underwriter exercises its option to purchase additional shares in this offering in full), after deducting the underwriting discounts and commissions and estimated offering expenses payable by us. We intend to use the net proceeds from this offering to fund a redemption of all of the outstanding 2019 Notes, which were issued in 2009 and of which $350.0 million aggregate principal amount is outstanding as of the date of this prospectus supplement, in accordance with the terms of the indenture governing the 2019 Notes.

We may redeem the 2019 Notes, at our option, at any time in whole, or from time to time in part, at a price equal to the greater of (i) 100% of the principal amount of the 2019 Notes to be redeemed, plus accrued interest to the date of redemption; or (ii) the sum of the present values of the remaining scheduled payments of principal and interest on the 2019 Notes to be redeemed, exclusive of interest accrued to the date of redemption, discounted to the date of redemption on a semiannual basis (assuming a 360-day year consisting of twelve 30-day months) at the applicable U.S. Treasury rate plus 50 basis points, plus accrued interest to the date of redemption. The 2019 Notes mature on June 1, 2019, and interest on the 2019 Notes accrues at a rate of 9.375%, payable semi-annually on June 1 and December 1 of each year, resulting in a redemption premium of approximately $40.0 million in connection with our intended redemption of all of the outstanding 2019 Notes. The pre-tax annual cash interest expense on the 2019 Notes is approximately $32.8 million. The indenture governing the 2019 Notes more fully describes the terms of the 2019 Notes. That indenture is an exhibit to our Annual Report on Form 10-K for our fiscal year ended December 31, 2016, which is incorporated by reference into this prospectus supplement and the accompanying prospectus.

Any net proceeds from this offering that are not used to fund a redemption of all of the outstanding 2019 Notes will be used for general corporate purposes.

Until the net proceeds from this offering are applied as described above, we may invest proceeds in short-term, investment grade interest-bearing securities or in obligations of, or guaranteed by, the U.S. government.

Affiliates of Goldman Sachs & Co. LLC are holders of the 2019 Notes, and accordingly, may receive a portion of the net proceeds of this offering. See the section entitled “Underwriting” below.

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COMMON STOCK PRICE RANGE AND DIVIDEND POLICY

Our common stock is listed on the New York Stock Exchange under the symbol “ATI.” The following table sets forth, for the periods indicated, the high and low sales prices per share of our common stock as reported on the NYSE and the dividends declared per share of our common stock.


	Price Range of Common Stock				Cash Dividend Per Share
	High		Low		Cash Dividend Per Share
2015
First Quarter		$35.10		$27.12	$	0.18
Second Quarter		$37.76		$29.05	$	0.18
Third Quarter		$31.02		$13.66	$	0.18
Fourth Quarter		$19.10		$10.15	$	0.08

2016
First Quarter		$18.38		$7.08	$	0.08
Second Quarter		$18.03		$10.93	$	0.08
Third Quarter		$18.67		$12.27	$	0.08
Fourth Quarter		$19.20		$13.15		—

2017
First Quarter		$23.69		$15.61		—
Second Quarter		$20.11		$14.54		—
Third Quarter		$24.00		$16.51		—
Fourth Quarter (through November 6, 2017)		$26.59		$22.72		—

The last reported sale price of our common stock on the New York Stock Exchange on November 6, 2017 was $25.84 per share. As of October 31, 2017, there were 108,863,099 shares of our common stock outstanding, held by approximately 3,364 registered holders.

The payment of dividends, if any, and the amount of such dividends depends upon matters deemed relevant by our Board of Directors on a quarterly basis, such as our results of operations, financial condition, cash requirements, future prospects, any limitations imposed by law, credit agreements or debt securities and other factors deemed relevant and appropriate. Under the Credit Facility, there is no limit on dividend declarations or payments provided that the undrawn availability, after giving effect to a particular dividend payment, is at least the greater of $100 million and 25% of the sum of the maximum revolving advance amount under the Credit Facility and the outstanding principal amount under the term loan component of the Credit Facility (the “Term Loan”), and no event of default under the Credit Facility has occurred and is continuing or would result from paying the dividend. In addition, there is no limit on dividend declarations or payments if the undrawn availability is less than the greater of $100.0 million and 25% of the sum of the maximum revolving advance amount under the Credit Facility and the outstanding principal amount under the Term Loan, but more than the greater of $60.0 million and 15% of the sum of the maximum revolving advance amount under the Credit Facility and the outstanding principal amount under the Term Loan, if (i) no event of default has occurred and is continuing or would result from paying the dividend, (ii) we demonstrate to the administrative agent that, prior to and after giving effect to the payment of the

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dividend (A) the undrawn availability, as measured both at the time of the dividend payment and as an average for the 60 consecutive day period immediately preceding the dividend payment, is at least the greater of $60.0 million and 15% of the sum of the maximum revolving advance amount under the Credit Facility and the outstanding principal amount under the Term Loan, and (B) we demonstrate that prior to and after such dividend payment, the fixed charge coverage ratio is at least 1.00:1.00, as calculated in accordance with the terms of the Credit Facility.

While we historically paid cash dividends on our common stock on a quarterly basis, effective with the fourth quarter of 2016, our Board of Directors decided to suspend the quarterly dividend. No assurance can be given that we will resume the payment dividends on our common stock in a manner and amount consistent with our historic practices, or at all, in the future.

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CAPITALIZATION

The following table sets forth our consolidated capitalization as of September 30, 2017:

•

on an actual basis; and

•

on an as-adjusted basis to reflect the issuance of common stock pursuant to this offering (assuming no exercise of the underwriter’s option to purchase additional shares of our common stock) and the application of the net proceeds therefrom, as described under the caption “Use of Proceeds.”

This table should be read in conjunction with our historical consolidated financial statements, including the related notes, which are incorporated by reference into this prospectus supplement and the accompanying prospectus, as well as any related free writing prospectus.


	As of September 30, 2017
	Actual			As Adjusted
	(Dollars in millions)
Cash and cash equivalents	$	124.9		$

Total debt (including current portion of long-term debt):
Revolving credit facility ⁽¹⁾	$	25.0		$	25.0
Term loan		100.0			100.0
4.75% Convertible Senior Notes due 2022		287.5			287.5
9.375% Senior Notes due 2019		350.0			—
5.95% Senior Notes due 2021		500.0			500.0
5.875% Senior Notes due 2023 ^(a)		500.0			500.0
Allegheny Ludlum 6.95% Debentures due 2025		150.0			150.0
Other debt		16.8			16.8
Debt issuance costs		(15.2	)		(13.8	)

Total debt		1,914.1			1,565.5

(a) bearing interest at 7.875% effective February 15, 2016

Stockholders’ equity:
Preferred stock, par value $0.10; 50,000,000 shares authorized; issued – none	$	—		$	—
Common stock, par value $0.10; 500,000,000 shares authorized; 109,695,171 shares issued and 108,863,099 shares outstanding (actual); 126,695,171 shares issued and 125,863,099 shares outstanding (as adjusted)		11.0			12.7
Additional paid-in-capital		1,196.4
Retained earnings ⁽²⁾		1,182.6			1,141.2
Treasury stock, at cost; 832,072 shares		(25.9	)		(25.9	)
Accumulated other comprehensive loss, net of tax		(1,016.3	)		(1,016.3	)

Total ATI stockholders’ equity		1,347.8
Noncontrolling interests		99.7			99.7
Total stockholders’ equity		1,447.5

Total ATI capitalization	$	3,261.9		$

(1)	Our revolving credit facility provides for aggregate borrowings of up to $400 million. Borrowing availability under the facility is reduced on a dollar-for-dollar basis by the amount of any outstanding letters of credit under the facility.

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As of September 30, 2017, we had $25.0 million of outstanding borrowings under the facility, and approximately $42.0 million of letters of credit were outstanding under the facility.

(2)	The as-adjusted amount reflects an adjustment to retained earnings as a result of the payment of the applicable redemption premium in connection with the redemption of all of the outstanding 2019 Notes, which we expect to be approximately $40.0 million. See “Use of Proceeds.”

The number of shares of our common stock in the table above excludes:

•

an aggregate of 3,619,435 shares of our common stock reserved for issuance in connection with our outstanding stock-settled equity awards;

•

an additional 5,422,744 shares of our common stock available for future grants under our equity compensation plans;

•

shares of common stock issuable in connection with conversion of our outstanding 4.75% Convertible Senior Notes due 2022.

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DESCRIPTION OF COMMON STOCK

Please read the information discussed under the heading “Description of Capital Stock — Common Stock” beginning on page 13 of the accompanying prospectus. As of September 30, 2017, we had 108,863,099 shares of common stock issued and outstanding and had reserved approximately 9,042,179 million additional shares of common stock for issuance under our equity compensation plans.

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MATERIAL UNITED STATES FEDERAL INCOME TAX CONSIDERATIONS

The following is a summary of material U.S. federal income tax consequences relating to the ownership and disposition of shares of our common stock, as of the date hereof. This summary deals only with shares of our common stock that are held as capital assets within the meaning of Section 1221 of the Internal Revenue Code of 1986, as amended, or the “Code” (generally, property held for investment). This summary does not discuss any U.S. federal tax consequences other than those relating to income taxes (such as estate or gift tax consequences) and does not discuss any state, local or non-U.S. tax consequences. In addition, this summary does not discuss all aspects of U.S. federal income taxation that may be relevant to the ownership or disposition of our common stock by prospective investors in light of their particular circumstances. Except to the extent discussed below, this summary does not address all of the tax consequences that may be relevant to certain types of investors subject to special treatment under U.S. federal income tax laws, such as:

•

dealers in securities or currencies, brokers, financial institutions, controlled foreign corporations, passive foreign investment companies, regulated investment companies, real estate investment trusts, retirement plans, certain former citizens or long-term residents of the United States, tax-exempt entities, traders in securities that elect to use a mark-to-market method of accounting for their securities holdings or insurance companies;

•

U.S. Holders (as defined below) of shares of our common stock whose “functional currency” is not the U.S. dollar;

•

persons holding shares of our common stock as part of a hedging, integrated, constructive sale, or conversion transaction or a straddle;

•

entities or arrangements that are treated as partnerships for U.S. federal income tax purposes; or

•

persons liable for alternative minimum tax.

The discussion below is based upon the provisions of the Code, applicable U.S. Treasury regulations promulgated thereunder, and administrative rulings and judicial decisions as of the date hereof. Those authorities may be subject to different interpretations and may be changed, perhaps retroactively, so as to result in U.S. federal income tax consequences different from those discussed below.

If an entity or arrangement treated as a partnership for U.S. federal income tax purposes holds shares of our common stock, the tax treatment of a partner in the partnership will generally depend upon the status of the partner and the activities of the partnership. If you are an equity holder in a partnership that holds shares of our common stock, you should consult your tax advisor as to the particular U.S. federal income tax consequences applicable to you.

If you are considering the purchase of shares of our common stock, you should consult your own tax advisors concerning the U.S. federal tax consequences, including estate tax consequences, to you and any consequences arising under the laws of any state, local, non-U.S. or other taxing jurisdiction. Each prospective investor should seek advice based on its particular circumstances from an independent tax advisor.

For purposes of this summary, a “U.S. Holder” means a beneficial owner of a share of our common stock that is:

•

an individual who is a citizen or resident of the United States;

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•

a corporation (or any other entity treated as a corporation for U.S. federal income tax purposes) created or organized in or under the laws of the United States or any state thereof or the District of Columbia;

•

an estate the income of which is subject to U.S. federal income taxation regardless of its source; or

•

a trust if (i) it is subject to the primary supervision of a court within the United States and one or more U.S. persons have the authority to control all substantial decisions of the trust or (ii) it has a valid election in effect under applicable U.S. Treasury regulations to be treated as a U.S. person.

Consequences to U.S. Holders

The following is a summary of material U.S. federal income tax consequences that will apply to a U.S. Holder of shares of our common stock.

Distributions

If we make a distribution in respect of our common stock, the distribution will be treated as a dividend to the extent it is paid from our current or accumulated earnings and profits, as determined under U.S. federal income tax principles. If the distribution exceeds current and accumulated earnings and profits, the excess will be treated as a nontaxable return of capital that reduces the holder’s adjusted tax basis in the common stock. Any remaining excess will be treated as capital gain. A holder’s adjusted tax basis in our common stock will generally be the amount the holder paid for it, subject to certain adjustments.

If a U.S. Holder is an individual, dividends received by such holder may be subject to a reduced maximum tax rate provided certain holding period and other requirements are met. If a U.S. Holder is a U.S. corporation, it may be able to claim the deduction allowed to U.S. corporations in respect of dividends received from other U.S. corporations equal to a portion of any dividends received, subject to generally applicable limitations on that deduction. U.S. Holders should consult their tax advisors regarding the holding period requirements that must be satisfied in order to qualify for the dividends-received deduction and the reduced maximum tax rate on dividends.

Sale, Exchange or Other Taxable Disposition of Common Stock

A U.S. Holder will generally recognize capital gain or loss on a sale, exchange or other taxable disposition of our common stock. The U.S. Holder’s gain or loss will equal the difference between the amount realized by the U.S. Holder and the U.S. Holder’s adjusted tax basis in the stock. The amount realized by the U.S. Holder will include the amount of any cash and the fair market value of any other property received for the stock. Gain or loss recognized by a U.S. Holder on a sale or exchange of stock will be long-term capital gain or loss if the U.S. Holder’s holding period in the stock is more than one year at the time of the sale, exchange or other taxable disposition. Long-term capital gains of non-corporate taxpayers currently are eligible for reduced rates of taxation. The deductibility of capital losses is subject to certain limitations.

Additional Tax on Net Investment Income

Non-corporate U.S. persons are generally subject to a 3.8% tax on the lesser of (1) the U.S. person’s “net investment income” for the relevant taxable year and (2) the excess of the U.S. person’s modified adjusted gross income for the taxable year over a certain threshold (which in the case of individuals will be between $125,000 and $250,000, depending on the individual’s tax return filing status). A U.S. Holder’s net investment income will generally include any income or gain recognized

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by such holder with respect to our common stock, unless such income or gain is derived in the ordinary course of the conduct of such U.S. Holder’s trade or business (other than a trade or business that consists of certain passive or trading activities). Non-corporate U.S. persons should consult their tax advisors on the applicability of this additional tax to income and gains in respect of their investment in our common stock.

Information Reporting and Backup Withholding

We or our paying agent must report annually to U.S. Holders and the Internal Revenue Service, or the “IRS,” amounts paid to such holders on or with respect to our common stock during each calendar year, the amount of proceeds from the sale of our common stock and the amount of tax, if any, withheld from such payments. A U.S. Holder will be subject to backup withholding on dividends paid on our common stock and proceeds from the sale of our common stock at the applicable rate if the U.S. Holder is not otherwise exempt and (i) the holder fails to provide us or our paying agent with a correct taxpayer identification number, (ii) we or our paying agent are notified by the IRS that the holder provided an incorrect taxpayer identification number, (iii) we or our paying agent are notified by the IRS that the holder failed to properly report payments of interest or dividends or (iv) the holder fails to certify under penalty of perjury that it has provided a correct taxpayer identification number and has not been notified by the IRS that it is subject to backup withholding. A U.S. Holder generally may establish that it is exempt from or otherwise not subject to backup withholding by providing a properly completed IRS Form W-9 to us or our paying agent. Any amounts withheld under the backup withholding rules will generally be allowed as a refund or a credit against a U.S. Holder’s U.S. federal income tax liability, provided the required information is properly furnished to the IRS on a timely basis.

Consequences to Non-U.S. Holders

The following is a summary of the material U.S. federal income tax consequences that will apply to a Non-U.S. Holder of shares of our common stock. The term “Non-U.S. Holder” means a beneficial owner of shares of our common stock that is an individual, corporation, estate or trust for U.S. federal income tax purposes and is not a U.S. Holder.

Distributions

Distributions on our common stock will constitute dividends to the extent described above in “— Consequences to U.S. Holders — Distributions.” Any dividends paid to Non-U.S. Holders with respect to the shares of our common stock will generally be subject to U.S. withholding tax at a 30% rate or such lower rate as specified by an applicable income tax treaty. To receive the benefit of a reduced treaty rate, a Non-U.S. Holder must furnish to us or our paying agent a valid IRS Form W-8BEN, W-BEN-E, or other applicable or successor form, certifying such holder’s qualification for the reduced rate. This certification must be provided to us or our paying agent prior to the payment of dividends and must be updated periodically. If a Non-U.S. Holder is eligible for a reduced rate of U.S. withholding tax pursuant to an income tax treaty but fails to timely provide the required certification, the holder may obtain a refund or credit of any excess amounts withheld by timely filing an appropriate claim for such refund or credit with the IRS.

Dividends that are effectively connected with a Non-U.S. Holder’s conduct of a trade or business within the United States (and, where an applicable income tax treaty so requires, are attributable to such Non-U.S. Holder’s permanent establishment in the United States) are generally not subject to U.S. withholding tax, provided the Non-U.S. Holder furnishes to us or our paying agent a properly executed IRS Form W-8ECI (or applicable successor form) prior to the payment of dividends. Instead, dividends that are effectively connected with a Non-U.S. Holder’s conduct of a U.S. trade or

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business (and, where an applicable income tax treaty so requires, are attributable to such Non-U.S. Holder’s permanent establishment in the United States), are subject to U.S. federal income tax on a net income basis at applicable graduated individual or corporate rates. Any such effectively connected dividends received by a foreign corporation may, under certain circumstances, be subject to an additional branch profits tax at a 30% rate or such lower rate as specified by an applicable income tax treaty. Non-U.S. Holders should consult their tax advisors regarding the potential application of tax treaties and their eligibility for income tax treaty benefits.

Sale, Exchange or Other Taxable Disposition of Common Stock

Subject to the discussions below under “— Information Reporting and Backup Withholding” and “— Foreign Account Tax Compliance Act,” any gain realized by a Non-U.S. Holder upon the sale, exchange or other taxable disposition of shares of our common stock generally will not be subject to U.S. federal income tax unless:

•

that gain is effectively connected with such Non-U.S. Holder’s conduct of a trade or business in the United States (and, where an applicable income tax treaty so requires, is attributable to such Non-U.S. Holder’s permanent establishment in the United States);

•

the Non-U.S. Holder is an individual who is present in the United States for 183 days or more in the taxable year of that disposition, and certain other conditions are met; or

•

we are or have been a “United States real property holding corporation” for U.S. federal income tax purposes at any time within the shorter of the five-year period ending on the date of disposition or the period that such Non-U.S. Holder held shares of our common stock and either our common stock was not regularly traded on an established securities market at any time during the calendar year in which the disposition occurs, or the Non-U.S. Holder owns or owned (actually or constructively) more than five percent of the total fair market value of shares of our common stock at any time during the five-year period ending on the date of disposition. We do not believe that we are, and do not anticipate that we will become, a “U.S. real property holding corporation” for U.S. federal income tax purposes.

A Non-U.S. Holder described in the first bullet point above will generally be subject to U.S. federal income tax on the net gain derived from the sale under regular graduated U.S. federal income tax rates or such lower rate as specified by an applicable income tax treaty. A Non-U.S. Holder that is a foreign corporation may, in addition, be subject to a branch profits tax at a 30% rate or a lower rate specified by an applicable income tax treaty. An individual Non-U.S. Holder described in the second bullet point above will generally be subject to a flat 30% U.S. federal income tax on the gain derived from the sale, which may be offset by U.S. source capital losses. If a Non-U.S. Holder is eligible for the benefits of an income tax treaty between the United States and its country of residence, any gain described in the second bullet point will be subject to U.S. federal income tax in the manner specified by the income tax treaty and generally will only be subject to such tax if such gain is attributable to a permanent establishment maintained by the Non-U.S. Holder in the United States. To claim the benefit of any applicable income tax treaty, a Non-U.S. Holder must properly submit an IRS Form W-8BEN, W-8BEN-E or other applicable or successor form. Non-U.S. Holders should consult their tax advisors regarding the potential application of income tax treaties and their eligibility for income tax treaty benefits.

Information Reporting and Backup Withholding

We must report annually to the IRS the amount of dividends or other distributions we pay to Non-U.S. Holders on shares of our common stock and the amount of tax we withhold on these

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distributions. These information reporting requirements apply even if no withholding is required. Copies of the information returns reporting such distributions and any withholding may also be made available to the tax authorities in the country in which the Non-U.S. Holder resides under the provisions of an applicable income tax treaty or other agreement. A Non-U.S. Holder generally will not be subject to backup withholding (but may be subject to other withholding as described above) on dividends the Non-U.S. Holder receives on shares of our common stock provided that we do not have actual knowledge or reason to know that the holder is a U.S. person, as defined under the Code, and we have received from the holder a properly completed IRS Form W-8BEN, W-8BEN-E or other applicable or successor form, or the holder otherwise establishes an exemption.

Information reporting and backup withholding generally are not required with respect to the amount of any proceeds from the sale of shares of our common stock outside the United States through a foreign office of a foreign broker that does not have certain specified connections to the United States. However, if a Non-U.S. Holder sells shares of our common stock through a U.S. broker or the U.S. office of a foreign broker, the broker will be required to report the amount of proceeds paid to the Non-U.S. Holder to the IRS and also backup withhold on that amount unless the Non-U.S. Holder provides to the broker a properly completed IRS Form W-8BEN, W-8BEN-E or other applicable or successor form or otherwise establishes an exemption, and the broker does not have actual knowledge or reason to know that the holder is a U.S. person, as defined under the Code.

Any amounts withheld under the backup withholding rules will generally be allowed as a refund or a credit against a Non-U.S. Holder’s U.S. federal income tax liability provided the required information is properly furnished to the IRS on a timely basis.

Foreign Account Tax Compliance Act

Sections 1471 through 1474 of the Code, Treasury regulations promulgated thereunder and applicable administrative guidance (collectively, “FATCA”) impose a 30% withholding tax on payments of dividends on, and after December 31, 2018, gross proceeds from the sale or other disposition of, our common stock made to (i) a “foreign financial institution,” as defined under such rules, unless such institution enters into an agreement with the Department of Treasury to, among other things, collect and provide to it substantial information regarding such institution’s U.S. financial account holders, including certain account holders that are foreign entities with U.S. owners or, in the case of a foreign financial institution in a jurisdiction that has entered into an intergovernmental agreement with the United States, such institution complies with the requirements of such agreement and (ii) a “non-financial foreign entity,” as defined under such rules, unless such entity provides the paying agent with a certification that it does not have any substantial U.S. owners or a certification identifying the direct and indirect substantial U.S. owners of the entity, unless in each case, an exemption applies.

Holders are encouraged to consult with their own tax advisors regarding the possible implications of these rules for their investment in our common stock.

The foregoing discussion of material U.S. federal income tax considerations is for general information purposes only and is not tax or legal advice. You should consult your own tax advisor as to the particular tax consequences to you of owning and disposing of our common stock, including the applicability and effect of any U.S. federal, state or local or non-U.S. tax laws, and of any changes or proposed changes in applicable law.

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UNDERWRITING

Goldman Sachs & Co. LLC is acting as sole bookrunning manager of the offering. Subject to the terms and conditions stated in the underwriting agreement dated the date of this prospectus supplement, the underwriter named below has agreed to purchase, and we have agreed to sell to the underwriter, the number of shares of common stock set forth opposite the underwriter’s name.


Underwriter	Number of Shares
Goldman Sachs & Co. LLC
Total		17,000,000

The underwriting agreement provides that the obligations of the underwriter to purchase the shares included in this offering are subject to approval of legal matters by counsel and to other conditions. The underwriter is obligated to purchase all the shares if they purchase any of the shares. The offering of the shares by the underwriter is subject to receipt and acceptance and subject to the underwriter’s right to reject any order in whole or in part.

If all the shares are not sold at the initial offering price, the underwriter may change the offering price and the other selling terms. Sales of shares made outside of the United States may be made by affiliates of the underwriter.

We have granted to the underwriter an option, exercisable for 30 days from the date of this prospectus supplement to purchase up to 2,550,000 shares from the Company. To the extent the option is exercised, the underwriter must purchase an additional number of shares approximately proportionate to the underwriter’s initial purchase commitment. Any shares issued or sold under the option will be issued and sold on substantially the same terms and conditions as the other shares that are the subject of this offering.

We have agreed that we will not (i) offer, sell, contract to sell, pledge or otherwise dispose of, directly or indirectly, or file with the Securities and Exchange Commission a registration statement under the Securities Act relating to, any shares of our common stock or securities convertible into or exchangeable or exercisable for any shares of our common stock, or publicly disclose the intention to make any offer, sale, pledge, disposition or filing, or (ii) enter into any swap or other arrangement that transfers all or a portion of the economic consequences associated with the ownership of any shares of common stock (regardless of whether any of these transactions are to be settled by the delivery of shares of common stock, or such other securities, in cash or otherwise), in each case without the prior written consent of Goldman Sachs & Co. LLC for a period of 90 days after the date of this prospectus supplement.

The following table shows the per share and total underwriting discounts and commissions that we are to pay to the underwriter in connection with this offering. Such amounts are shown assuming both no exercise and full exercise of the underwriter’s option to purchase 2,550,000 additional shares.


	Paid by ATI
	No Exercise	Full exercise
Per Share	$	$
Total	$	$

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We estimate that our total expenses for this offering will be approximately $400,000.

In connection with the offering, the underwriter may purchase and sell shares in the open market. Purchases and sales in the open market may include short sales, purchases to cover short positions, which may include purchases pursuant to the underwriter’s option to purchase additional shares, and stabilizing purchases.

•

Short sales involve sales by the underwriter of a greater number of shares than it is required to purchase in the offering.

•

“Covered” short sales are sales of shares in an amount up to the number of shares represented by the underwriter’s option to purchase additional shares.

•

“Naked” short sales are sales of shares in an amount in excess of the number of shares represented by the underwriter’s option to purchase additional shares.

•

Covering transactions involve purchases of shares either pursuant to the underwriter’s option to purchase additional shares or in the open market in order to cover short positions.

•

To close a naked short position, the underwriter must purchase shares in the open market. A naked short position is more likely to be created if the underwriter is concerned that there may be downward pressure on the price of the shares in the open market after pricing that could adversely affect investors who purchase in the offering.

•

To close a covered short position, the underwriter must purchase shares in the open market or must exercise its option to purchase additional shares. In determining the source of shares to close the covered short position, the underwriter will consider, among other things, the price of shares available for purchase in the open market as compared to the price at which it may purchase shares by exercising its option to purchase additional shares.

•

Stabilizing transactions involve bids to purchase shares so long as the stabilizing bids do not exceed a specified maximum.

Purchases to cover short positions and stabilizing purchases, as well as other purchases by the underwriter for its own account, may have the effect of preventing or retarding a decline in the market price of the shares. They may also cause the price of the shares to be higher than the price that would otherwise exist in the open market in the absence of these transactions. The underwriter may conduct these transactions on the NYSE, in the over-the-counter market or otherwise. If the underwriter commences any of these transactions, it may discontinue them at any time without notice.

In connection with this offering, the underwriter (or its affiliates) may, for its own account, enter into derivative transactions relating to the shares at the same time as the offer and sale of the shares or in secondary market transactions. Such transactions may be entered into with the company’s affiliates. As a result of such transactions, the underwriter may hold long or short positions in such shares or derivatives. These transactions may comprise a substantial portion of the offering and no

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disclosure will be made of any such positions. In addition, the underwriter (or its affiliates) may have purchased shares and been allocated the shares for asset management and/or proprietary purposes and not with a view to distribution.

The underwriter has advised us that, pursuant to Regulation M of the Securities Act of 1933, it may also engage in other activities that stabilize, maintain or otherwise affect the price of the shares, including the imposition of penalty bids. This means that if the representative of the underwriter purchases shares in the open market in stabilizing transactions or to cover short sales, the representative can require the underwriter that sold those shares as part of this offering to repay the underwriting discount received by them.

The underwriter is a full service financial institution engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, principal investment, hedging, financing and brokerage activities. The underwriter or its affiliates have performed commercial banking, investment banking and advisory services for us from time to time for which they have received customary fees and reimbursement of expenses. The underwriter may, from time to time, engage in transactions with and perform services for us in the ordinary course of their business for which they may receive customary fees and reimbursement of expenses. In addition, affiliates of Goldman Sachs & Co. LLC are holders of the 2019 Notes. We may use a portion of the net proceeds from the offering to redeem the 2019 Notes, and as a result of such redemption, such affiliates of the underwriter will receive a portion of the proceeds of this offering.

In addition, in the ordinary course of their business activities, the underwriter and its affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers. Such investments and securities activities may involve securities and/or instruments of ours or our affiliates. The underwriter or its affiliates routinely hedge, and the underwriter or its affiliates may hedge, its credit exposure to us consistent with its customary risk management policies. Typically, the underwriter and its affiliates would hedge such exposure by entering into transactions which consist of either the purchase of credit default swaps or the creation of short positions in our securities, including potentially the shares offered hereby. Any such short positions could adversely affect future trading prices of the shares offered hereby. The underwriter and its affiliates may also make investment recommendations and/or publish or express independent research views in respect of such securities or financial instruments and may hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

We have agreed to indemnify the underwriter against certain liabilities, including liabilities under the Securities Act, or to contribute to payments the underwriter may be required to make because of any of those liabilities.

A prospectus in electronic format may be made available on the web sites maintained by the underwriter, or selling group members, if any, participating in the offering. The underwriter may agree to allocate a number of shares to selling group members for sale to their online brokerage account holders. Internet distributions will be allocated by the representative to selling group members that may make internet distributions on the same basis as other allocations.

Other than in the United States, no action has been taken by us or the underwriter that would permit a public offering of the securities offered by this prospectus in any jurisdiction where action for

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that purpose is required. The securities offered by this prospectus may not be offered or sold, directly or indirectly, nor may this prospectus or any other offering material or advertisements in connection with the offer and sale of any such securities be distributed or published in any jurisdiction, except under circumstances that will result in compliance with the applicable rules and regulations of that jurisdiction. Persons into whose possession this prospectus comes are advised to inform themselves about and to observe any restrictions relating to the offering and the distribution of this prospectus. This prospectus does not constitute an offer to sell or a solicitation of an offer to buy any securities offered by this prospectus in any jurisdiction in which such an offer or a solicitation is unlawful.

Notice to Prospective Investors in the European Economic Area

In relation to each member state of the European Economic Area that has implemented the Prospectus Directive (each, a “Relevant Member State”), with effect from and including the date on which the Prospectus Directive is implemented in that Relevant Member State, an offer of shares described in this prospectus supplement may not be made to the public in that Relevant Member State other than:

•

to any legal entity which is a qualified investor as defined in the Prospectus Directive;

•

to fewer than 100 or, if the Relevant Member State has implemented the relevant provision of the 2010 PD Amending Directive, 150 natural or legal persons (other than qualified investors as defined in the Prospectus Directive), as permitted under the Prospectus Directive, subject to obtaining the prior consent of the relevant dealer or dealers nominated by us for any such offer; or

•

in any other circumstances falling within Article 3(2) of the Prospectus Directive,

provided that no such offer of securities shall require us or the underwriter to publish a prospectus pursuant to Article 3 of the Prospectus Directive.

For purposes of this provision, the expression an “offer of securities to the public” in any relevant member state means the communication in any form and by any means of sufficient information on the terms of the offer and the securities to be offered so as to enable an investor to decide to purchase or subscribe for the securities, as the expression may be varied in that member state by any measure implementing the Prospectus Directive in that member state, and the expression “Prospectus Directive” means Directive 2003/71/EC (and amendments thereto, including the 2010 PD Amending Directive, to the extent implemented in the relevant member state) and includes any relevant implementing measure in each relevant member state. The expression 2010 PD Amending Directive means Directive 2010/73/EU.

The sellers of the shares have not authorized and do not authorize the making of any offer of shares through any financial intermediary on their behalf, other than offers made by the underwriter with a view to the final placement of the shares as contemplated in this prospectus supplement. Accordingly, no purchaser of the shares, other than the underwriter, is authorized to make any further offer of the shares on behalf of the sellers or the underwriter.

Notice to Prospective Investors in Canada

The shares may be sold only to purchasers purchasing, or deemed to be purchasing, as principal that are accredited investors, as defined in National Instrument 45-106 Prospectus

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Exemptions or subsection 73.3(1) of the Securities Act (Ontario), and are permitted clients, as defined in National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the shares must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this prospectus supplement (including any amendment thereto) contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser’s province or territory. The purchaser should refer to any applicable provisions of the securities legislation of the purchaser’s province or territory for particulars of these rights or consult with a legal advisor.

Pursuant to section 3A.3 of National Instrument 33-105 Underwriting Conflicts (NI 33-105), the underwriter is not required to comply with the disclosure requirements of NI 33-105 regarding underwriter conflicts of interest in connection with this offering.

Notice to Prospective Investors in the United Kingdom

This prospectus supplement and the accompanying prospectus are only being distributed to, and is only directed at, persons in the United Kingdom that are qualified investors within the meaning of Article 2(1)(e) of the Prospectus Directive that are also (i) investment professionals falling within Article 19(5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005 (the “Order”) or (ii) high net worth entities, and other persons to whom it may lawfully be communicated, falling within Article 49(2)(a) to (d) of the Order (each such person being referred to as a “relevant person”). This prospectus supplement and its contents are confidential and should not be distributed, published or reproduced (in whole or in part) or disclosed by recipients to any other persons in the United Kingdom. Any person in the United Kingdom that is not a relevant person should not act or rely on this document or any of its contents.

Notice to Prospective Investors in France

Neither this prospectus supplement nor any other offering material relating to the shares described in this prospectus supplement has been submitted to the clearance procedures of the Autorité des Marchés Financiers or of the competent authority of another member state of the European Economic Area and notified to the Autorité des Marchés Financiers. The shares have not been offered or sold and will not be offered or sold, directly or indirectly, to the public in France. Neither this prospectus supplement nor any other offering material relating to the shares has been or will be:

•

released, issued, distributed or caused to be released, issued or distributed to the public in France; or

•

used in connection with any offer for subscription or sale of the shares to the public in France.

Such offers , sales and distributions will be made in France only:

•

to qualified investors (investisseurs qualifiés) and/or to a restricted circle of investors (cercle restreint d’investisseurs), in each case investing for their own account, all as defined in, and in accordance with, articles L.411-2, D.411-1, D.411-2, D.734-1, D.744-1, D.754-1 and D.764-1 of the French Code monétaire et financier;

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•

to investment services providers authorized to engage in portfolio management on behalf of third parties; or

•

in a transaction that, in accordance with article L.411-2-II-1° -or-2° -or 3° of the French Code monétaire et financier and article 211-2 of the General Regulations ( Règlement Général ) of the Autorité des Marchés Financiers , does not constitute a public offer ( appel public à l’épargne ).

The shares may be resold directly or indirectly, only in compliance with articles L.411-1, L.411-2, L.412-1 and L.621-8 through L.621-8-3 of the French Code monétaire et financier .

Notice to Prospective Investors in Hong Kong

The shares may not be offered or sold in Hong Kong by means of any document other than (i) in circumstances which do not constitute an offer to the public within the meaning of the Companies Ordinance (Cap. 32, Laws of Hong Kong), or (ii) to “professional investors” within the meaning of the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) and any rules made thereunder, or (iii) in other circumstances which do not result in the document being a “prospectus” within the meaning of the Companies Ordinance (Cap. 32, Laws of Hong Kong) and no advertisement, invitation or document relating to the shares may be issued or may be in the possession of any person for the purpose of issue (in each case whether in Hong Kong or elsewhere), which is directed at, or the contents of which are likely to be accessed or read by, the public in Hong Kong (except if permitted to do so under the laws of Hong Kong) other than with respect to shares which are or are intended to be disposed of only to persons outside Hong Kong or only to “professional investors” within the meaning of the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) and any rules made thereunder.

Notice to Prospective Investors in Japan

The shares offered in this prospectus supplement have not been and will not be registered under the Financial Instruments and Exchange Law of Japan, and the shares have not been offered or sold and will not be offered or sold, directly or indirectly, in Japan or to or for the account of any resident of Japan (including any corporation or other entity organized under the laws of Japan), except (i) pursuant to an exemption from the registration requirements of the Financial Instruments and Exchange Law and (ii) in compliance with any other applicable requirements of Japanese law.

Notice to Prospective Investors in Singapore

This prospectus supplement has not been registered as a prospectus with the Monetary Authority of Singapore. Accordingly, this prospectus supplement and any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of the shares may not be circulated or distributed, nor may the shares be offered or sold, or be made the subject of an invitation for subscription or purchase, whether directly or indirectly, to persons in Singapore other than (i) to an institutional investor under Section 274 of the Securities and Futures Act, Chapter 289 of Singapore (the “SFA”), (ii) to a relevant person pursuant to Section 275(1), or any person pursuant to Section 275(1A), and in accordance with the conditions specified in Section 275 of the SFA or (iii) otherwise pursuant to, and in accordance with the conditions of, any other applicable provision of the SFA, in each case subject to compliance with conditions set forth in the SFA.

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Where the shares are subscribed or purchased under Section 275 of the SFA by a relevant person which is:

•

a corporation (which is not an accredited investor (as defined in Section 4A of the SFA)) the sole business of which is to hold investments and the entire share capital of which is owned by one or more individuals, each of whom is an accredited investor; or

•

a trust (where the trustee is not an accredited investor) whose sole purpose is to hold investments and each beneficiary of the trust is an individual who is an accredited investor, shares,

debentures and units of shares and debentures of that corporation or the beneficiaries’ rights and interest (howsoever described) in that trust shall not be transferred within six months after that corporation or that trust has acquired the shares pursuant to an offer made under Section 275 of the SFA except:

•

to an institutional investor (for corporations, under Section 274 of the SFA) or to a relevant person defined in Section 275(2) of the SFA, or to any person pursuant to an offer that is made on terms that such shares, debentures and units of shares and debentures of that corporation or such rights and interest in that trust are acquired at a consideration of not less than S$200,000 (or its equivalent in a foreign currency) for each transaction, whether such amount is to be paid for in cash or by exchange of securities or other assets, and further for corporations, in accordance with the conditions specified in Section 275 of the SFA;

•

where no consideration is or will be given for the transfer; or

•

where the transfer is by operation of law.

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LEGAL MATTERS

The validity of the shares of common stock offered hereby will be passed upon for us by K&L Gates LLP, Pittsburgh, Pennsylvania. The underwriter has been represented in connection with this offering by Cravath, Swaine & Moore LLP, New York, New York.

EXPERTS

The consolidated financial statements of Allegheny Technologies Incorporated appearing in Allegheny Technologies Incorporated’s Annual Report (Form 10-K) for the year ended December 31, 2016 and the effectiveness of Allegheny Technologies Incorporated’s internal control over financial reporting as of December 31, 2016 have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their reports thereon, included therein, and incorporated herein by reference. Such consolidated financial statements are incorporated herein by reference in reliance upon such reports given on the authority of such firm as experts in accounting and auditing.

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PROSPECTUS

LOGO

Allegheny Technologies Incorporated

Debt Securities

Preferred Stock

Common Stock

Warrants

Purchase Contracts

Purchase Units

Depositary Shares

We may, from time to time, offer to sell, in one or more series, senior or subordinated debt securities, preferred stock, common stock, warrants, purchase contracts, purchase units or depositary shares, or any combination of these securities. The debt securities, preferred stock, warrants and purchase contracts may be convertible into or exercisable or exchangeable for our common or preferred stock or other securities or debt or equity securities of one or more other entities.

Our common stock is listed on the New York Stock Exchange and trades under the ticker symbol “ATI.” If we decide to seek a listing of any securities offered by this prospectus, we will disclose the exchange or market on which the securities will be listed or where we have made an application for listing in one or more supplements to this prospectus.

This prospectus describes some of the general terms that may apply to these securities. The specific terms of any securities to be offered, and the specific manner in which they may be offered, will be described in one or more supplements to this prospectus. This prospectus may not be used to sell securities unless it is accompanied by a prospectus supplement that contains a description of those securities.

We may offer and sell these securities to or through one or more underwriters, dealers or agents, or directly to other purchasers, on a continuous or delayed basis. If any offering involves underwriters, dealers or agents, arrangements with them will be described in a prospectus supplement relating to that offering.

We urge you to carefully read the information included or incorporated by reference in this prospectus and any prospectus supplement for a discussion of factors you should consider before deciding to invest in any securities offered by this prospectus, including the information under “ Risk Factors ” on page 2 of this prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this Prospectus is May 15, 2015.

TABLE OF CONTENTS


ABOUT THIS PROSPECTUS			i
WHERE YOU CAN FIND MORE INFORMATION			ii
SUMMARY			1
RISK FACTORS			2
FORWARD-LOOKING STATEMENTS			2
CONSOLIDATED RATIOS OF EARNINGS TO FIXED CHARGES			3
USE OF PROCEEDS			3
DESCRIPTION OF DEBT SECURITIES			4
DESCRIPTION OF OTHER SECURITIES			12
DESCRIPTION OF CAPITAL STOCK			13
PLAN OF DISTRIBUTION			17
LEGAL MATTERS			19
EXPERTS			19

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we have filed with the Securities and Exchange Commission (the “SEC”), using an automatic shelf registration process. By using a shelf registration statement, we may sell, from time to time, in one or more offerings, any combination of the securities described in this prospectus. This prospectus does not contain all of the information in that registration statement. For further information about our business and the securities that may be offered under this prospectus, you should refer to the registration statement and its exhibits. The exhibits to the registration statement contain the full text of certain contracts and other important documents that we have summarized in this prospectus. Since the summaries in this prospectus may not contain all the information that you may find important in deciding whether to purchase the securities we may offer, you should review the full text of these contracts and documents. These summaries are qualified in all respects by reference to all of the provisions contained in the applicable contract or document. The registration statement and its exhibits can be obtained from the SEC as indicated under the heading “Where You Can Find More Information.”

This prospectus only provides you with a general description of the securities we may offer. Each time we sell securities, we will provide a prospectus supplement that contains specific information about the terms of those securities. The prospectus supplement may also add, update or change information contained in this prospectus. You should read this prospectus and any applicable prospectus supplement together with the additional information described below under the heading “Where You Can Find More Information.”

You should rely only on the information contained or incorporated by reference in this prospectus and any applicable prospectus supplement. We have not authorized anyone to provide you with different information. We are not making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should not assume that the information in this prospectus, any prospectus supplement or any document incorporated herein by reference is accurate as of any date other than the date of the applicable document. Our business, financial condition, results of operations and prospects may have changed since that date.

WHERE YOU CAN FIND MORE INFORMATION

Available Information

We file reports, proxy statements and other information with the SEC. These reports, proxy statements and other information that we file with the SEC can be read and copied at the SEC’s Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 to obtain further information on the operation of the Public Reference Room. The SEC maintains an internet site that contains reports, proxy and information statements and other information regarding issuers that file electronically with the SEC, including us. The SEC’s internet address is http://www.sec.gov. In addition, our common stock is listed on the New York Stock Exchange, and our reports and other information can be inspected at the offices of the New York Stock Exchange, 20 Broad Street, New York, New York 10005. Our Internet website is www.atimetals.com. Information contained on our website is not part of, and should not be construed as being incorporated by reference into, this prospectus.

Incorporation by Reference

The SEC allows us to “incorporate by reference” information that we file with it. This means that we can disclose important information to you by referring you to other documents. Any information we incorporate in this manner is considered part of this prospectus except to the extent updated and superseded by information contained in this prospectus. Some information that we file with the SEC after the date of this prospectus and until we sell all of the securities covered by this prospectus will automatically update and supersede the information contained in this prospectus.

We incorporate by reference the following documents that we have filed with the SEC and any filings that we make with the SEC in the future under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), until we sell all of the securities covered by this prospectus, including between the date of this prospectus and the date on which the offering of the securities under this prospectus is terminated, except as noted in the paragraph below:


Our SEC Filings (File No. 1-12001)		Period for or Date of Filing
Annual Report on Form 10-K		Year Ended December 31, 2014
Quarterly Report on Form 10-Q		Quarter Ended March 31, 2015
Current Reports on Form 8-K		March 3 and May 7, 2015
Registration Statement on Form 8-A		July 30, 1996

Pursuant to General Instruction B of Form 8-K, any information submitted under Item 2.02, Results of Operations and Financial Condition, or Item 7.01, Regulation FD Disclosure, of Form 8-K is not deemed to be “filed” for the purpose of Section 18 of the Exchange Act, and we are not subject to the liabilities of Section 18 with respect to information submitted under Item 2.02 or Item 7.01 of Form 8-K. We are not incorporating by reference any information submitted under Item 2.02 or Item 7.01 of Form 8-K into any filing under the Securities Act of 1933, as amended (the “Securities Act”), or the Exchange Act or into this prospectus.

Statements contained in prospectus as to the contents of any contract, agreement or other document referred to in this prospectus do not purport to be complete, and where reference is made to the particular provisions of that contract, agreement or other document, those references are qualified in all respects by reference to all of the provisions contained in that contract or other document. For a more complete understanding and description of each such contract, agreement or other document, we urge you to read the documents filed as exhibits to the registration statement of which the accompanying prospectus is a part.

Any statement contained in a document incorporated by reference, or deemed to be incorporated by reference, into this prospectus will be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained herein, therein or in any other subsequently filed document which also is

incorporated by reference in this prospectus modifies or supersedes that statement. Any such statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this prospectus.

We will provide without charge, upon written or oral request, a copy of any or all of the documents that are incorporated by reference into this prospectus and a copy of any or all other contracts, agreements or documents which are referred to in this prospectus. Requests should be directed to: Allegheny Technologies Incorporated, 1000 Six PPG Place, Pittsburgh, PA 15222-5479, Attention: Corporate Secretary; telephone number: (412) 394-2800. You also may review a copy of the registration statement and its exhibits at the SEC’s Public Reference Room in Washington, D.C., as well as through the SEC’s internet site.

iii

SUMMARY

This summary highlights selected information contained elsewhere in this prospectus and the documents incorporated by reference in this prospectus. Because the following is only a summary, it does not contain all of the information that may be important to you. You should carefully read this prospectus, any accompanying prospectus supplement and the documents incorporated by reference in this prospectus and any accompanying prospectus supplement before deciding whether to invest in any of our securities. References to the “Company”, “we”, “our” and “us” and similar terms means Allegheny Technologies Incorporated and its subsidiaries, unless the context otherwise requires.

Allegheny Technologies Incorporated

We are one of the largest and most diversified specialty materials and components producers in the world. Our high-value products include titanium and titanium alloys, nickel-based alloys and specialty steels, precision forgings, castings and machined components, zirconium and related alloys, precision and engineered stainless steel strip, and grain-oriented electrical steel. Our standard products include specialty stainless sheet, stainless steel sheet, and stainless steel plate. Our specialty materials are produced in a wide range of alloys and product forms and are selected for use in applications that demand materials having exceptional hardness, toughness, strength, resistance to heat, corrosion or abrasion, or a combination of these characteristics. We are a fully integrated supplier from raw material (for titanium sponge) and melt (for other specialty alloy systems) through highly engineered finished components. Our common stock is quoted on the New York Stock Exchange under the symbol “ATI.”

Our principal executive offices are located at 1000 Six PPG Place, Pittsburgh, PA 15222, and our telephone number is (412) 394-2800.

RISK FACTORS

Investing in our securities involves risks. Before deciding to purchase any of our securities, you should carefully consider the discussion of risks and uncertainties under the heading “Risk Factors” contained in our Annual Report on Form 10-K for the fiscal year ended December 31, 2014, which is incorporated by reference in this prospectus, and under similar headings in our subsequently filed quarterly reports on Form 10-Q and annual reports on Form 10-K, as well as the other risks and uncertainties described in any applicable prospectus supplement and in the other documents incorporated by reference in this prospectus. See the information under the heading “Where You Can Find More Information” for information on how to obtain copies of documents incorporated by reference in this prospectus. The risks and uncertainties we discuss in the documents incorporated by reference in this prospectus are those we currently believe may materially affect our company. Additional risks and uncertainties not presently known to us or that we currently believe are immaterial also may materially and adversely affect our business, financial condition and results of operations.

FORWARD-LOOKING STATEMENTS

You should carefully review the information contained in or incorporated by reference into this prospectus. In this prospectus, statements that are not reported financial results or other historical information are “forward-looking statements.” Forward-looking statements give current expectations or forecasts of future events and are not guarantees of future performance. They are based on our management’s expectations that involve a number of business risks and uncertainties, any of which could cause actual results to differ materially from those expressed in or implied by the forward-looking statements.

CONSOLIDATED RATIOS OF EARNINGS TO FIXED CHARGES

The following table sets forth the ratio of our earnings to fixed charges for the periods indicated:

Year Ended December 31,

Three
Months
Ended
March 31,
2015

2010

2011

2012

2013

2014

Ratio of earnings to fixed charges

2.2x

3.6x

2.8x

—

(1)

—

(1)

1.6x

(1)	For the year ended December 31, 2013 and 2014, fixed charges exceeded earnings by $192.8 million and $7.1 million, respectively.

For purposes of calculating the ratio of earnings to fixed charges, “earnings” represents income (loss) from continuing operations before income tax provision and cumulative effect of change in accounting principle, plus (income) loss recognized on less than fifty percent owned persons, plus fixed charges, less capitalized interest, less noncontrolling interest in the income of subsidiaries with fixed charges. “Fixed charges” consists of interest expense, the portion of rents deemed to be interest, capitalized interest and amortization of debt expense.

USE OF PROCEEDS

We intend to use the net proceeds from the sale of the securities for general corporate purposes unless otherwise indicated in the applicable prospectus supplement relating to a specific issuance of securities. Our general corporate purposes include, but are not limited to, repayment, redemption or refinancing of debt, capital expenditures, investments in or loans to subsidiaries and joint ventures, funding of possible acquisitions, working capital, contributions to one or more of our pension plans, satisfaction of other obligations and repurchase of our outstanding equity securities. Pending any such use, the net proceeds from the sale of the securities may be invested in short-term, investment grade, interest-bearing instruments. We will include a more detailed description of the use of proceeds of any specific offering under this prospectus in the applicable prospectus supplement relating to that offering.

DESCRIPTION OF DEBT SECURITIES

The following is a general description of the debt securities that we may offer from time to time under this prospectus. The particular terms of the debt securities offered under this prospectus and the extent, if any, to which the general provisions described below may apply will be described in the applicable prospectus supplement. Although our securities include securities denominated in U.S. dollars, we may choose to issue securities in any other currency, including the euro.

The debt securities will be either senior debt securities or subordinated debt securities. We will issue the senior debt securities under an indenture, dated June 1, 2009, between Allegheny Technologies Incorporated and The Bank of New York Mellon, as trustee (the “Senior Indenture”). The Senior Indenture is an exhibit to the registration statement of which this prospectus is a part. We will issue the subordinated debt securities under a subordinated indenture between us and The Bank of New York Mellon, as trustee (the “Subordinated Indenture”), a form of which is as an exhibit to the registration statement of which this prospectus is a part. The Senior Indenture and the Subordinated Indenture sometimes are collectively referred to in this prospectus as the indentures, and The Bank of New York Mellon, as trustee under the Senior Indenture or the Subordinated Indenture, as the case may be, sometimes is referred to in this prospectus as the trustee.

The following description is only a summary of the material provisions of the indentures. We urge you to read the appropriate indenture, along with any applicable supplement to the appropriate indenture, because they, and not this description, define your rights as holders of the applicable debt securities. See the information under the heading “Where You Can Find More Information” for information on how to obtain a copy of the appropriate indenture and any applicable supplement to that indenture. The following description also is subject to and qualified by reference to the description of the particular terms of the debt securities, the relevant indenture and any applicable supplement to that indenture, as described in the applicable prospectus supplement, including definitions used in the relevant indenture and any applicable supplement to that indenture. The particular terms of the debt securities that we may offer under this prospectus, the relevant indenture and any applicable supplement to that indenture may vary from the terms described below.

General

The senior debt securities will be unsubordinated obligations, will rank equally with all other unsubordinated debt obligations of ours and, unless otherwise indicated in the applicable prospectus supplement, will be unsecured. The subordinated debt securities will be subordinate in right of payment to any senior debt securities. A description of certain additional terms of the subordinated debt securities is provided below under “— Subordinated Debt Securities.” The specific terms of any subordinated debt securities will be provided in the applicable prospectus supplement. For a complete understanding of the provisions pertaining to the subordinated debt securities, you should refer to the form of the Subordinated Indenture which is an exhibit to the registration statement of which this prospectus is a part. Unless we elect or are required to secure the debt securities, the debt securities will be effectively subordinated to any of our existing and future secured debt to the extent of the assets securing that debt.

Our primary sources of funding for our payment obligations under the debt securities will be revenues from our operations and investments and cash distributions from our subsidiaries. Our subsidiaries are separate and distinct legal entities and have no obligation whatsoever to pay any amounts due on debt securities issued by us or to make funds available to us. Our subsidiaries’ ability to pay dividends or make other payments or advances to us will depend upon their operating results and will be subject to applicable laws and contractual restrictions. The Senior Indenture does not, and the Subordinated Indenture will not, restrict our subsidiaries from entering into agreements that prohibit or limit their ability to pay dividends or make other payments or advances to us.

To the extent that we must rely on cash from our subsidiaries to pay amounts due on the debt securities, the debt securities will be effectively subordinated to all of our subsidiaries’ liabilities, including their trade payables. This means that our subsidiaries may be required to pay all of their creditors in full before their assets

are available to us. Even if we are recognized as a creditor of our subsidiaries, our claims would be effectively subordinated to any security interests in their assets and also could be subordinated to some or all other claims on their assets and earnings.

In addition to the debt securities that we may offer pursuant to this prospectus, we may issue other debt securities in public or private offerings from time to time. These other debt securities may be issued under other indentures or documentation that are not described in this prospectus, and those debt securities may contain provisions materially different from the provisions applicable to one or more issues of debt securities offered pursuant to this prospectus.

Terms

The Senior Indenture does not, and the Subordinated Indenture will not, limit the principal amount of debt, including unsecured debt, or other securities that we or our subsidiaries may issue.

We may issue notes or bonds in traditional paper form, or we may issue a global security. The debt securities of any series may be issued in definitive form or, if provided in the applicable prospectus supplement, may be represented in whole or in part by a global security or securities, registered in the name of a depositary designated by us. Each debt security represented by a global security is referred to in this prospectus as a “book-entry security.”

Debt securities may be issued from time to time pursuant to this prospectus and will be offered on terms determined by market conditions at the time of sale. Debt securities may be issued in one or more series with the same or various maturities and may be sold at par, a premium or an original issue discount. Debt securities sold at an original issue discount may bear no interest or interest at a rate that is below market rates. Unless otherwise provided in the applicable prospectus supplement, debt securities denominated in U.S. dollars will be issued in denominations of $2,000 and integral multiples of $1,000 in excess thereof.

Please refer to the applicable prospectus supplement for the specific terms of the debt securities offered, including the following:

•

Designation of an aggregate principal amount, purchase price and denomination;

•

Date of maturity;

•

If other than U.S. currency, the currency in which the debt securities may be purchased and the currency in which principal, premium, if any, and interest will be paid;

•

The interest rate or rates and the method of calculating interest (unless we specify a different method, interest will be calculated based on a 360-day year consisting of 12 30-day months);

•

The date or dates from which the interest will accrue, the payment dates on which any premium and interest will be payable or the manner of determination of the payment dates and the record dates for the determination of holders to whom interest is payable;

•

The place or places where principal, premium, if any, and interest will be payable;

•

Any redemption or sinking fund provisions or other repayment or repurchase obligations;

•

Any index used to determine the amount of principal, premium, if any, and interest to be paid with respect to the debt securities;

•

The application, if any, of defeasance provisions to the debt securities;

•

If other than the entire principal amount, the portion of the debt securities that would be payable upon acceleration of the maturity thereof;

•

Whether the debt securities will be issued in whole or in part in the form of one or more global securities and, in such case, the depositary for the global securities;

•

Whether the debt securities may be converted into or exercised or exchanged for our common stock, preferred stock, warrants, other securities, purchase contracts or purchase units and the terms of such conversion, exercise or exchange, if any;

•

Any covenants applicable to the debt securities;

•

Any events of default applicable to the debt securities;

•

Any changes to the events of default described in this prospectus;

•

The terms of subordination, if applicable;

•

The terms of conversion, if applicable; and

•

Any other specific material terms, including any additions to the terms described in this prospectus and any terms that may be required by or advisable under applicable law.

Except with respect to book-entry securities, debt securities may be presented for exchange or registration of transfer, in the manner, at the places and subject to the restrictions set forth in the debt securities and the applicable prospectus supplement. Such services will be provided without charge, other than any tax or other governmental charge payable in connection therewith, but subject to the limitations provided in the indentures.

Merger, Consolidation or Sale of Assets

Pursuant to the indentures, the Company will not, in a single transaction or through a series of related transactions, consolidate or merge with or into any other person, or, directly or indirectly, sell or convey all or substantially all of its properties and assets to another person or group of affiliated persons, except that the Company may consolidate or merge with, or sell or convey substantially all of its assets to another person if (i) the Company is the continuing person or the successor person (if other than the Company) is organized and existing under the laws of the United States of America, any State thereof or the District of Columbia and such person expressly assumes all obligations of the Company under the indenture, including payment of the principal and interest on the debt securities, and the performance and observance of all of the covenants and conditions of the indenture to be performed by the Company and (ii) there is no default under the indenture. Upon such a succession, the Company will be relieved from any further obligations under the indenture.

Events of Default

Except as otherwise set forth in the applicable prospectus supplement, an event of default shall occur with respect to any series of debt securities when:

•

We default in paying principal or premium, if any, on any of the debt securities of such series when due;

•

We default in paying interest on any of the debt securities of such series when due and such default continues for 30 days;

•

We default in making deposits into any sinking fund payment with respect to any of the debt securities of such series when due and such default continues for 30 days;

•

We fail to perform any other covenant or warranty in the debt securities of such series or in the applicable indenture, and such failure continues for a period of 90 days after notice of such failure as provided in that indenture;

•

Certain events of bankruptcy, insolvency or reorganization involving us occur; or

•

Any other event of default specified in the applicable prospectus supplement occurs with respect to debt securities of that series.

We will be required annually to deliver to the trustee an officers’ certificate stating whether or not the officers signing such certificate have any knowledge of any default in the performance by us of our obligations under the applicable indenture.

If an event of default shall occur and be continuing with respect to any series (other than an event of default described in the fifth bullet point of the first paragraph above under “— Events of Default”), the trustee or the holders of not less than 25% in principal amount of the debt securities of such series then outstanding (or, if any debt securities of that series are original issue discount securities, the portion of the principal amount of such securities as may be specified by the terms thereof) may declare the debt securities of such series to be immediately due and payable. If an event of default described in the fifth bullet point of the first paragraph above under “— Events of Default” occurs with respect to any series of debt securities, the principal amount of all debt securities of that series (or, if any debt securities of that series are original issue discount securities, the portion of the principal amount of such securities as may be specified by the terms thereof) will automatically become due and payable without any declaration by the trustee or the holders. The trustee is required to give holders of the debt securities of any series written notice of a default with respect to such series as and to the extent provided by the Trust Indenture Act of 1939, as amended. As used in this paragraph, a “default” means an event described in the first paragraph above under “— Events of Default” without including any applicable grace period.

If at any time after the debt securities of such series have been declared due and payable, and before any judgment or decree for the moneys due has been obtained or entered, we pay or deposit with the trustee amounts sufficient to pay all matured installments of interest upon the debt securities of such series and the principal of all debt securities of such series which shall have become due, otherwise than by acceleration, together with interest on such principal and, to the extent legally enforceable, on such overdue installments of interest and all other amounts due under the applicable indenture shall have been paid, and any and all defaults with respect to such series under that indenture shall have been remedied, then the holders of a majority in aggregate principal amount of the debt securities of such series then outstanding, by written notice to us and the trustee, may rescind and annul the declaration that the debt securities of such series are due and payable.

In addition, the holders of a majority in aggregate principal amount of the debt securities of such series may waive any past default and its consequences with respect to such series, except a default in the payment of the principal of or any premium or interest on any debt securities of such series or a default in the performance of a covenant that cannot be modified under the applicable indenture without the consent of the holder of each affected debt security.

The trustee is under no obligation to exercise any of the rights or powers under the indentures at the request, order or direction of any of the holders of debt securities, unless such holders shall have offered to the trustee security or indemnity satisfactory to the trustee. Subject to such provisions for the indemnification of the trustee and certain limitations contained in the indentures, the holders of a majority in aggregate principal amount of the debt securities of each series at the time outstanding shall have the right to direct the time, method and place of conducting any proceeding for any remedy available to the trustee, or exercising any trust or power conferred on the trustee, with respect to the debt securities of such series.

No holder of debt securities of any series will have any right to institute any proceeding, judicial or otherwise, with respect to the applicable indenture, for the appointment of a receiver or trustee or for any other remedy under the indenture, unless:

•

The holder has previously given written notice to the trustee of a continuing event of default with respect to the debt securities of that series; and

•

The holders of at least 25% in principal amount of the outstanding debt securities of that series have made a written request to the trustee, and offered reasonable indemnity satisfactory to the trustee, to institute proceedings as trustee, the trustee has failed to institute the proceedings within 60 days after its receipt of such notice and the trustee has not received from the holders of a majority in principal amount of the debt securities of that series a direction inconsistent with that request.

Notwithstanding the foregoing, the holder of any debt security issued under indentures will have an absolute and unconditional right to receive payment of the principal of and any premium and, subject to the provisions of the applicable indenture regarding the payment of default interest, interest on that debt security on the due dates expressed in that security and to institute suit for the enforcement of payment.

Modification of the Indentures

The Senior Indenture contains, and the Subordinated Indenture will contain, provisions permitting us and the trustee to modify that indenture or enter into or modify any supplemental indenture without the consent of the holders of the debt securities for any of the following purposes:

•

To evidence the succession of another corporation to us in accordance with “— Merger, Consolidation or Sale of Assets”;

•

To add to our covenants further covenants for the benefit or protection of the holders of any or all series of debt securities or to surrender any right or power conferred upon us by that indenture;

•

To add any additional events of default with respect to all or any series of debt securities;

•

To add to or change any of the provisions of that indenture to facilitate the issuance of debt securities in bearer form with or without coupons, or to permit or facilitate the issuance of debt securities in uncertificated form;

•

To add to, change or eliminate any of the provisions of that indenture in respect of one or more series of debt securities thereunder, under certain conditions designed to protect the rights of any existing holder of those debt securities;

•

To secure all or any series of debt securities;

•

To establish the forms or terms of the debt securities of any series;

•

To evidence the appointment of a successor trustee and to add to or change provisions of that indenture necessary to provide for or facilitate the administration of the trusts under that indenture by more than one trustee; and

•

To cure any ambiguity, to correct or supplement any provision of that indenture which may be defective or inconsistent with another provision of that indenture or to change any other provisions with respect to matters or questions arising under that indenture, provided that any such action shall not adversely affect the interests of the holders of any series of debt securities.

We and the trustee may otherwise modify each indenture or any supplemental indenture with the consent of the holders of not less than a majority in aggregate principal amount of each series of debt securities affected thereby at the time outstanding, except that no such modifications shall:

•

Change the fixed maturity of any debt securities or any installment of principal, interest or premium on any debt securities, or reduce the principal amount thereof or reduce the rate of interest or premium payable upon redemption, or reduce the amount of principal of an original issue discount debt security or any other debt security that would be due and payable upon a declaration of acceleration of the maturity thereof, or change the currency in which the debt securities are payable or impair the right to institute suit for the enforcement of any payment after the stated maturity thereof or the redemption date, if applicable, or adversely affect any right of the holder of any debt security to require us to repay or repurchase that security, without the consent of the holder of each debt security so affected;

•

Reduce the percentage of debt securities of any series, the consent of the holders of which is required for any waiver or supplemental indenture, without the consent of the holders of all debt securities affected thereby then outstanding;

•

Modify the provisions of that indenture relating to the waiver of past defaults or the waiver or certain covenants or the provisions described above, except to increase any percentage set forth in those

provisions or to provide that other provisions of that indenture may not be modified without the consent of the holder of each debt security affected thereby, without the consent of the holder of each debt security affected thereby;

•

Change any obligation of ours to maintain an office or agency;

•

Change any obligation of ours to pay additional amounts;

•

Adversely affect any right of repayment or repurchase at the option of the holder; or

•

Reduce or postpone any sinking fund or similar provision.

With respect to any vote of holders of a series of debt securities, we generally will be entitled to set any date as a record date for the purpose of determining the holders of outstanding debt securities that are entitled to vote or take other action under the applicable indenture.

Satisfaction and Discharge, Defeasance and Covenant Defeasance

Except as otherwise specified in the applicable prospectus supplement, each indenture shall be satisfied and discharged if (i) we shall deliver to the trustee all debt securities then outstanding for cancellation or (ii) all debt securities not delivered to the trustee for cancellation shall have become due and payable, are to become due and payable within one year or are to be called for redemption within one year and we shall deposit an amount sufficient to pay the principal, premium, if any, and interest to the date of maturity, redemption or deposit (in the case of debt securities that have become due and payable), provided that in either case we shall have paid all other sums payable under that indenture.

The Senior Indenture provides, and the Subordinated Indenture will provide, if such provision is made applicable to the debt securities of a series, that we may elect either (A) to defease and be discharged from any and all obligations with respect to any debt security of such series, or “defeasance,” or (B) to be released from our obligations with respect to such debt security under certain of the covenants and events of default under that indenture together with additional covenants that may be included for a particular series and that certain events of default shall not be events of default under that indenture with respect to such series (“covenant defeasance”), upon the deposit with the trustee (or other qualifying trustee), in trust for such purpose, of money or certain U.S. government obligations which through the payment of principal and interest in accordance with their terms will provide money, in an amount sufficient to pay the principal of (and premium, if any) and interest on such debt security, on the scheduled due dates.

In the case of defeasance or covenant defeasance, the holders of such debt securities will be entitled to receive payments in respect of such debt securities solely from such trust. Such a trust may only be established if, among other things, we have delivered to the trustee an opinion of counsel (as specified in the indentures) to the effect that the holders of the debt securities affected thereby will not recognize income, gain or loss for Federal income tax purposes as a result of such defeasance or covenant defeasance and will be subject to Federal income tax on the same amounts, in the same manner and at the same times as would have been the case if such defeasance or covenant defeasance had not occurred. Such opinion of counsel, in the case of defeasance under clause (A) above, must refer to and be based upon a ruling of the Internal Revenue Service or a change in applicable Federal income tax law occurring after the date of the applicable indenture.

Record Dates

The Senior Indenture provides, and the Subordinated Indenture will provide, that in certain circumstances we may establish a record date for determining the holders of outstanding debt securities of a series entitled to join in the giving of notice or the taking of other action under the applicable indenture by the holders of the debt securities of such series.

Subordinated Debt Securities

Subordinated debt securities will be subordinate, in right of payment, to all senior debt. Senior debt means, with respect to us, the principal, premium, if any, interest, fees, charges, expenses, reimbursement obligations, guarantees and other amounts owing on the following:

•

All indebtedness of ours, whether outstanding on the date of issuance or thereafter created, incurred or assumed, which is for money borrowed, or evidenced by a note or similar instrument given in connection with the acquisition of any business, properties or assets, including securities;

•

Any indebtedness of others of the kinds described in the preceding clause for the payment of which we are responsible or liable (directly or indirectly, contingently or otherwise) as guarantor or otherwise; and

•

Amendments, renewals, extensions and refundings of any indebtedness described above, unless in any instrument or instruments evidencing or securing such indebtedness or pursuant to which the same is outstanding, or in any such amendment, renewal, extension or refunding, it provides that such indebtedness is not senior or prior in right of payment to the subordinated debt securities.

Upon any distribution of our assets upon our dissolution, winding up, liquidation or reorganization, the payment of the principal, premium, if any, and interest, if any, on the subordinated debt securities will be subordinated, to the extent provided in the Subordinated Indenture, in right of payment to the prior payment in full of all of our senior debt. Our obligation to make payment of the principal, premium, if any, and interest, if any, on the subordinated debt securities will not otherwise be affected. In addition, no payment on account of principal and premium, if any, sinking fund or interest, if any, may be made on the subordinated debt securities at any time unless full payment of all amounts due in respect of the principal and premium, if any, sinking fund and interest, if any, on our senior debt has been made or duly provided for in money or money’s worth.

Notwithstanding the foregoing, unless all of our senior debt has been paid in full, in the event that any payment or distribution made by us is received by the trustee or the holders of any of the subordinated debt securities, such payment or distribution must be paid over to the holders of our senior debt or a person acting on their behalf, to be applied toward the payment of all of our senior debt remaining unpaid until all the senior debt has been paid in full. Subject to the payment in full of all of our senior debt, the rights of the holders of our subordinated debt securities will be subrogated to the rights of the holders of our senior debt.

By reason of this subordination, in the event of a distribution of our assets upon our insolvency, certain of our general creditors may recover more, ratably, than holders of our subordinated debt securities.

Governing Law

The laws of the State of New York governs the Senior Indenture, will govern the Subordinated Indenture and will govern the debt securities issued under the indentures.

“Street Name” and Other Indirect Holders

Investors who hold securities in accounts at banks or brokers generally will not be recognized by us as legal holders of debt securities. This is called holding in “street name.” Instead, we would recognize only the bank or broker, or the financial institution that the bank or broker uses to hold its securities. These intermediary banks, brokers and other financial institutions pass along principal, interest and other payments on the debt securities, either because they agree to do so in their customer agreements or because they are legally required to do so. If you hold debt securities in “street name,” you should check with your own institution to find out, among other things:

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How it handles payments and notices;

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Whether it imposes fees or charges;

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How it would handle voting if applicable;

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Whether and how you can instruct it to send you debt securities registered in your own name so you can be a direct holder as described below; and

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If applicable, how it would pursue rights under your debt securities if there were a default or other event triggering the need for holders to act to protect their interests.

Our obligations, as well as the obligations of the trustee under the indentures and those of any third parties employed by us or the trustee under either of the indentures, run only to persons who are registered as holders of debt securities issued under the applicable indenture. As noted above, we do not have obligations to you if you hold in “street name” or other indirect means, either because you choose to hold debt securities in that manner or because the debt securities are issued in the form of global securities as described below. For example, once we make payment to the registered holder, we have no further responsibility for the payment even if that holder is legally required to pass the payment along to you as a “street name” customer but does not do so.

Book-Entry Securities

The following description of book-entry securities will apply to any series of debt securities issued in whole or in part in the form of one or more global securities except as otherwise described in the applicable prospectus supplement.

Book-entry securities of like tenor and having the same date will be represented by one or more global securities deposited with and registered in the name of a depositary that is a clearing agent registered under the Exchange Act. Beneficial interests in book-entry securities will be limited to institutions that have accounts with the depositary, or “participants,” or persons that may hold interests through participants.

Ownership of beneficial interests by participants will only be evidenced by, and the transfer of that ownership interest will only be effected through, records maintained by the depositary. Ownership of beneficial interests by persons that hold through participants will only be evidenced by, and the transfer of that ownership interest within such participant will only be effected through, records maintained by the participants. The laws of some jurisdictions require that certain purchasers of securities take physical delivery of such securities in definitive form. Such laws may impair the ability to transfer beneficial interests in a global security.

Payment of principal of and any premium and interest on book-entry securities represented by a global security registered in the name of or held by a depositary will be made to the depositary, as the registered owner of the global security. Neither we, the trustee nor any agent of ours or the trustee will have any responsibility or liability for any aspect of the depositary’s records or any participant’s records relating to or payments made on account of beneficial ownership interests in a global security or for maintaining, supervising or reviewing any of the depositary’s records or any participant’s records relating to the beneficial ownership interests. Payments by participants to owners of beneficial interests in a global security held through such participants will be governed by the depositary’s procedures, as is now the case with securities held for the accounts of customers registered in “street name,” and will be the sole responsibility of such participants.

A global security representing a book-entry security will be exchangeable for definitive debt securities in registered form, of like tenor and of an equal aggregate principal amount registered in the name of, or is transferable in whole or in part to, a person other than the depositary for that global security, only if:

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The depositary notifies us that it is unwilling or unable to continue as depositary for that global security and we do not appoint a successor depositary within 90 days after receiving that notice;

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At any time the depositary ceases to be a clearing agency registered under the Exchange Act and we do not appoint a successor depositary within 90 days after becoming aware that the depositary has ceased to be registered as a clearing agency;

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We in our sole discretion determine that that the global security is so transferable or will be exchangeable for definitive securities in registered form and, in each case, notify the trustee of our decision;

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An event of default with respect to the debt securities of that series has occurred and is continuing; or

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Other circumstances exist that have been specified in the terms of the debt securities of that series.

Any global security that is exchangeable pursuant to the preceding sentence shall be registered in the name or names of such person or persons as the depositary shall instruct the trustee. It is expected that such instructions may be based upon directions received by the depositary from its participants with respect to ownership of beneficial interests in such global security.

Except as provided above, owners of beneficial interests in a global security will not be entitled to receive physical delivery of debt securities in definitive form and will not be considered the holders thereof for any purpose under the indentures, and no global security shall be exchangeable, except for a security registered in the name of the depositary. This means each person owning a beneficial interest in such global security must rely on the procedures of the depositary and, if such person is not a participant, on the procedures of the participant through which such person owns its interest, to exercise any rights of a holder under the indentures. We understand that under existing industry practices, if we request any action of holders or an owner of a beneficial interest in such global security desires to give or take any action that a holder is entitled to give or take under the indentures, the depositary would authorize the participants holding the relevant beneficial interests to give or take such action, and such participants would authorize beneficial owners owning through such participant to give or take such action or would otherwise act upon the instructions of beneficial owners owning through them.

DESCRIPTION OF OTHER SECURITIES

We will set forth in the applicable prospectus supplement a description of any warrants, purchase contracts, purchase units or depositary shares that may be offered pursuant to this prospectus.

DESCRIPTION OF CAPITAL STOCK

Common Stock

We may issue, either separately or together with other securities, including as a part of purchase units, shares of our common stock. Shares of common stock issued as part of purchase units may be attached to or separate from any other securities part of those purchase units. Under our Restated Certificate of Incorporation, we are authorized to issue up to 500,000,000 shares of our common stock. As of May 1, 2015, we had 109,215,499 shares of common stock issued and outstanding and had reserved approximately 5.6 million additional shares of common stock for issuance under our stock compensation plans.

A prospectus supplement relating to an offering of common stock or other securities convertible or exchangeable for, or exercisable into, common stock, or the settlement of which may result in the issuance of common stock, will describe the relevant terms of the offering, including the number of shares offered, any initial offering price and market price and dividend information, as well as, if applicable, information on other related securities.

The following summary is not complete and is not intended to give full effect to provisions of statutory or common law. You should refer to the applicable provisions of the following:

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The Delaware General Corporation Law, as it may be amended from time to time;

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Our Restated Certificate of Incorporation, as it may be amended or further restated from time to time; and

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Our Amended and Restated Bylaws, as they may be further amended or restated from time to time.

Dividends. The holders of our common stock are entitled to receive dividends when, as and if declared by our board of directors, out of funds legally available for their payment subject to the rights of holders of our preferred stock.

Voting Rights. The holders of our common stock are entitled to one vote per share on all matters submitted to a vote of stockholders.

Rights upon Liquidation. In the event of our voluntary or involuntary liquidation, dissolution or winding up, the holders of common stock will be entitled to share equally in any of our assets available for distribution after the payment in full of all debts and distributions and after the holders of all series of our outstanding preferred stock have received their liquidation preferences in full.

Miscellaneous. The outstanding shares of common stock are fully paid and nonassessable. The holders of common stock are not entitled to preemptive or redemption rights. Shares of common stock are not convertible into shares of any other class of capital stock. Computershare Investor Services is the transfer agent and registrar for the common stock.

Preferred Stock

We may elect to issue shares of our preferred stock from time to time, as described in the applicable prospectus supplement. We may issue shares of preferred stock separately or as a part of purchase units, and any such shares issued as part of purchase units may be attached to or separate from any other securities part of those purchase units. Shares of our preferred stock may have dividend, redemption, voting and liquidation rights taking priority over our common stock, and shares of our preferred stock may be convertible into our common stock.

Our Board of Directors is authorized, subject to any limitations prescribed by law, to provide for the issuance of shares of preferred stock in one or more series. In addition, our Board of Directors is authorized to establish from time to time the number of shares to be included in each series of preferred stock and to fix the

designation, powers (including but not limited to voting powers, if any), preferences and rights of the shares of each series of preferred stock and any qualifications, limitations or restrictions of each series of preferred stock. The number of authorized shares of preferred stock may be increased or decreased (but not below the number of shares thereof then outstanding) by the affirmative vote of the holders of a majority of the outstanding common stock, without a vote of the holders of the preferred stock, or of any series of preferred stock, unless a vote of any such holders is required pursuant to the terms of any preferred stock.

Our Restated Certificate of Incorporation authorizes our Board of Directors without further stockholder action, to provide for the issuance of up to 50,000,000 shares of preferred stock, in one or more series. As of the date of this prospectus, no shares of preferred stock have been issued, and 50,000,000 shares of preferred stock are available for issuance. We have 6,000,000 shares of preferred stock designated as Series A Junior Participating Preferred Stock in connection with our prior rights agreement, leaving 44,000,000 shares of preferred stock remaining available for designation as of the date of this prospectus.

The particular terms of any series of preferred stock being offered by us under this prospectus will be described in the prospectus supplement relating to that series of preferred stock. Those terms may include:

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The title and liquidation preference per share of the preferred stock;

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The number of shares offered;

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The purchase price of the preferred stock;

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The dividend rate (or method of calculation), the dates on which dividends will be paid and the date from which dividends will begin to accumulate;

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Any redemption or sinking fund provisions of the preferred stock;

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Any conversion provisions of the preferred stock;

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The voting rights, if any, of the preferred stock; and

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Any additional dividend, liquidation, redemption, sinking fund and other rights, preferences, privileges, limitations and restrictions of the preferred stock.

If the terms of any series of preferred stock being offered differ from the terms set forth in this prospectus, the definitive terms will be disclosed in the applicable prospectus supplement. The summary in this prospectus is not complete. You should refer to the applicable Certificate of Amendment to our Restated Certificate of Incorporation or certificate of designations, as the case may be, establishing a particular series of preferred stock, in either case which will be filed with the Secretary of State of the State of Delaware and the SEC in connection with an offering of preferred stock.

The preferred stock will, when issued, be fully paid and nonassessable.

Dividend Rights. The preferred stock will be preferred over our common stock as to payment of dividends. Before any dividends or distributions (other than dividends or distributions payable in common stock) on our common stock will be declared and set apart for payment or paid, the holders of shares of each series of preferred stock will be entitled to receive dividends when, as and if declared by our board of directors. We will pay those dividends either in cash, shares of common stock or preferred stock or otherwise, at the rate and on the date or dates set forth in the applicable prospectus supplement. With respect to each series of preferred stock, the dividends on each share of the series will be cumulative from the date of issue of the share unless another date is set forth in the applicable prospectus supplement relating to the series. Accruals of dividends will not bear interest.

Rights upon Liquidation. The preferred stock will be preferred over our common stock as to assets so that the holders of each series of preferred stock will be entitled to be paid, upon our voluntary or involuntary liquidation, dissolution or winding up and before any distribution is made to the holders of common stock, the

amount set forth in the applicable prospectus supplement. However, in this case the holders of preferred stock will not be entitled to any other or further payment. If upon any liquidation, dissolution or winding up our net assets are insufficient to permit the payment in full of the respective amounts to which the holders of all outstanding preferred stock are entitled, our entire remaining net assets will be distributed among the holders of each series of preferred stock in amounts proportional to the full amounts to which the holders of each series are entitled.

Redemption. All shares of any series of preferred stock will be redeemable to the extent set forth in the prospectus supplement relating to the series. All shares of any series of preferred stock will be convertible into shares of our common stock or into shares of any other series of our preferred stock to the extent set forth in the applicable prospectus supplement.

Voting Rights. Except as indicated in the applicable prospectus supplement, the holders of preferred stock will be entitled to one vote for each share of preferred stock held by them on all matters properly presented to stockholders. The holders of common stock and the holders of all series of preferred stock will vote together as one class.

Additional Series of Preferred Stock. In the event of a proposed merger or tender offer, proxy contest or other attempt to gain control of us and not approved by our board of directors, it would be possible for the board to authorize the issuance of one or more series of preferred stock with voting rights or other rights and preferences which would impede the success of the proposed merger, tender offer, proxy contest or other attempt to gain control of us. This authority may be limited by applicable law, our Restated Certificate of Incorporation, as it may amended or further restated from time to time, and the applicable rules of the stock exchanges upon which the common stock is listed. The consent of our stockholders would not be required for any such issuance of preferred stock.

Special Charter Provisions. Our Restated Certificate of Incorporation provides that:

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Our Board of Directors is classified into three classes;

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In addition to the requirements of law and the other provisions of our Restated Certificate of Incorporation, the affirmative vote of at least two-thirds of the outstanding shares of our common stock is required for the adoption or authorization of any of the following events unless the event has been approved at a meeting of our Board of Directors by the vote of more than two-thirds of the incumbent members of our Board of Directors:

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Any merger or consolidation of us with or into any other corporation;

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Any sale, lease, exchange, transfer or other disposition, but excluding a mortgage or any other security device, of all or substantially all of our assets;

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Any merger or consolidation of a Significant Shareholder (as defined in our Restated Certificate of Incorporation) with or into us or a direct or indirect subsidiary of ours;

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Any sale, lease, exchange, transfer or other disposition to us or to a direct or indirect subsidiary of ours of any of our common stock held by a Significant Shareholder or any other assets of a Significant Shareholder which, if included with all other dispositions consummated during the same fiscal year of ours by the same Significant Shareholder, would result in dispositions of assets having an aggregate fair value in excess of five percent of our total consolidated assets as shown on our certified balance sheet as of the end of the fiscal year preceding the proposed disposition;

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Any reclassification of our common stock, or any re-capitalization involving our common stock, consummated within five years after a Significant Shareholder becomes a Significant Shareholder, whereby the number of outstanding shares of common stock is reduced or any of those shares are converted into or exchanged for cash or other securities;

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Any dissolution; and

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Any agreement, contract or other arrangement providing for any of these transactions but notwithstanding anything not including any merger pursuant to the Delaware General Corporation Law, as amended from time to time, which does not require a vote of our stockholders for approval;

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Our stockholders may not alter, amend, supplement or repeal, or adopt any provision inconsistent with the purpose or intent of, certain provisions contained in our Restated Certificate of Incorporation other than by the affirmative vote of 75% of the combined voting power of all of our outstanding voting securities entitled to vote generally in an election of directors, voting together as a single class;

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Our stockholders may not adopt, amend or repeal our Amended and Restated Bylaws other than by the affirmative vote of 75% of the combined voting power of all of our outstanding voting securities entitled to vote generally in an election of directors, voting together as a single class;

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Any action required or permitted to be taken by our stockholders must be effected at a duly called annual or special meeting of stockholders and may not be effected by the written consent of the stockholders; and

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Special meetings of the stockholders may be called at any time by a majority of our directors, our Chairman of the Board or our Chief Executive Officer and may not be called by any other person or persons or in any other manner.

PLAN OF DISTRIBUTION

We may sell the securities in one or more of the following ways:

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To underwriters, whether or not part of a syndicate, for public offering and sale by them;

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Directly to purchasers in negotiated sales or in competitively bid transactions;

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Through agents;

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Through dealers; or

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Through a combination of any of the above methods of sale.

Offers to purchase securities may be solicited directly by us or by agents designated by us from time to time. Any agent, who may be deemed to be an underwriter, as that term is defined in the Securities Act, involved in the offer and sale of the securities will be named, and any commissions payable by us to that agent will be provided, in an applicable prospectus supplement. We and our agents may sell the securities at:

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A fixed price or prices, which may be changed;

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Market prices prevailing at the time of sale;

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Prices related to such prevailing market prices; or

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Negotiated prices.

Underwriters, dealers and agents participating in the distribution of the securities may be deemed to be underwriters, and any discounts and commissions received by them and any profit realized by them on resale of the securities may be deemed to be underwriting discounts and commissions under the Securities Act. Underwriters, dealers and agents may be entitled, under agreements with us, to indemnification against and contribution toward certain civil liabilities, including liabilities under the Securities Act, and to reimbursement by us for certain expenses. Unless otherwise described in an applicable prospectus supplement, the obligations of the underwriters to purchase offered securities will be subject to conditions, and the underwriters must purchase all of the offered securities if any are purchased.

If an underwriter or underwriters are used in the offer or sale of securities, we will execute an underwriting agreement with the underwriters at the time of sale of the securities to the underwriters, and the names of the underwriters and the principal terms of our agreements with the underwriters will be provided in an applicable prospectus supplement.

The securities subject to the underwriting agreement may be acquired by the underwriters for their own account and may be resold by them from time to time in one or more transactions, including negotiated transactions, at a fixed offering price or at varying prices determined at the time of sale. Underwriters may be deemed to have received compensation from us in the form of underwriting discounts or commissions and may also receive commissions from the purchasers of these securities for whom they may act as agent. Underwriters may sell these securities to or through dealers. These dealers may receive compensation in the form of discounts, concessions or commissions from the underwriters and commissions from the purchasers for whom they may act as agent. Any initial offering price and any discounts or concessions allowed or re-allowed or paid to dealers may be changed from time to time.

In connection with underwritten offerings of the securities, the underwriters may engage in over-allotment, stabilizing transactions, covering transactions and penalty bids in accordance with Regulation M under the Exchange Act, as follows:

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Over-allotment transactions that involve sales in excess of the offering size, which create a short position for the underwriters;

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Stabilizing transactions that permit bids to purchase the underlying security so long as the stabilizing bids do not exceed a specified maximum;

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Covering transactions that involve purchases of the securities in the open market after the distribution has been completed in order to cover short positions; and

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Penalty bids that permit the underwriters to reclaim a selling concession from a broker/dealer when the securities originally sold by that broker-dealer are repurchased in a covering transaction to cover short positions.

These stabilizing transactions, covering transactions and penalty bids may cause the price of the securities to be higher than it otherwise would be in the absence of these transactions. If these transactions occur, they may be discontinued at any time.

If indicated in an applicable prospectus supplement, we will authorize dealers acting as agents for us to solicit offers by certain institutions to purchase securities from us at the public offering price set forth in the prospectus supplement under delayed delivery contracts providing for payment and delivery on the date or dates stated in the prospectus supplement. The identity of any such agents, the terms of such delayed delivery contracts and the commissions payable by us to these agents will be set forth in an applicable prospectus supplement.

If indicated in an applicable prospectus supplement, we may sell shares of our common stock under a newly established direct stock purchase and dividend reinvestment plan. The terms of any such plan will be set forth in the applicable prospectus supplement.

Each underwriter, dealer and agent participating in the distribution of any of the securities that are issuable in bearer form will agree that it will not offer, sell or deliver, directly or indirectly, securities in bearer form in the United States or to U.S. persons, other than qualifying financial institutions, during the restricted period, as defined in U.S. Treasury Regulations Section 1.163-5(c)(2)(i)(D)(7).

Except for shares of our common stock or as otherwise described in an applicable prospectus supplement, all of the securities will be a new issue of securities with no established trading market. Any underwriters to whom or agents through whom the securities are sold by us for public offering and sale may make a market in the securities, but such underwriters or agents will not be obligated to do so and may discontinue any market making at any time without notice. No assurance can be given as to the liquidity of the trading market for any such securities.

Certain of the underwriters, dealers or agents and their associates may be customers of, engage in transactions with and perform services for us and our subsidiaries in the ordinary course of business.

LEGAL MATTERS

Unless otherwise indicated in the applicable prospectus supplement, the validity of the securities offered by us will be passed upon for us by Elliot S. Davis, Senior Vice President, General Counsel, Chief Compliance Officer and Corporate Secretary of Allegheny Technologies Incorporated, or by K&L Gates LLP, Pittsburgh, Pennsylvania. Mr. Davis is paid a salary by Allegheny Technologies Incorporated, is a participant in various employee benefit plans offered to its employees and beneficially owns, or has rights to acquire, an aggregate of less than one percent of the shares of our outstanding common stock.

EXPERTS

The consolidated financial statements of Allegheny Technologies Incorporated and Subsidiaries appearing in Allegheny Technologies Incorporated’s Annual Report (Form 10-K) for the year ended December 31, 2014, and the effectiveness of Allegheny Technologies Incorporated and Subsidiaries’ internal control over financial reporting as of December 31, 2014, have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their reports thereon, included therein, and incorporated herein by reference. Such consolidated financial statements are, and audited consolidated financial statements to be included in subsequently filed documents will be, incorporated herein in reliance upon the reports of Ernst & Young LLP pertaining to such consolidated financial statements and the effectiveness of our internal control over financial reporting as of the respective dates (to the extent covered by consents filed with the Securities and Exchange Commission) given on the authority of such firm as experts in accounting and auditing.

17,000,000 Shares

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Allegheny Technologies Incorporated

Common Stock

P R E L I M I N A R Y P R O S P EC T U S S U P P L E M E N T

November , 2017

Goldman Sachs & Co. LLC

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