FIRST SUPPLEMENTAL INDENTURE

Exhibit 4.2

ALLEGHENY TECHNOLOGIES INCORPORATED

and

THE BANK OF NEW YORK MELLON,
as Trustee

FIRST SUPPLEMENTAL INDENTURE

DATED AS OF JUNE 1, 2009

TO THE INDENTURE

DATED AS OF JUNE 1, 2009

$350,000,000 principal amount of 9.375% Senior Notes due 2019

Table of Contents

FIRST SUPPLEMENTAL INDENTURE

     FIRST SUPPLEMENTAL INDENTURE, dated as of June 1, 2009 (the “ Supplemental Indenture ”), to the Base Indenture (defined below) between Allegheny Technologies Incorporated, a corporation duly organized and existing under the laws of Delaware (herein called the “ Company ”), and The Bank of New York Mellon, a New York banking corporation, as Trustee under the Indenture (herein called the “ Trustee ”).

RECITALS

          WHEREAS, the Company has heretofore executed and delivered to the Trustee an Indenture, dated as of June 1, 2009 (the “ Base Indenture ”), providing for the issuance from time to time of its Securities (as defined in the Base Indenture), to be issued in one or more series as therein provided;

          WHEREAS, Sections 2.01, 3.01 and 9.01 of the Base Indenture provide that the Company, when authorized by an Establishment Action (as defined in the Base Indenture), and the Trustee may, without the consent of the Holders (as defined in the Base Indenture) of Securities, enter into one or more supplemental indentures, in form satisfactory to the Trustee, to establish the form or terms of Securities of any series permitted by the Base Indenture;

          WHEREAS, pursuant to the terms of the Base Indenture, the Company desires to provide for the establishment of a new series of its Securities to be known as its 9.375% Senior Notes due 2019 (the “ Notes ”), the form and substance of such Notes and the terms, provisions and conditions thereof to be set forth as provided in the Base Indenture and this Supplemental Indenture (together, the “ Indenture ”);

          WHEREAS, the Company has duly authorized the creation and issuance of such Notes under the Base Indenture, and has duly authorized the execution and delivery of this Supplemental Indenture to modify the Base Indenture and to provide certain additional provisions as hereinafter described; and

          WHEREAS, the Company has requested that the Trustee execute and deliver this Supplemental Indenture, and all requirements necessary to make this Supplemental Indenture a valid instrument in accordance with its terms, and to make the Notes, when executed by the Company and authenticated and delivered by the Trustee, the valid and legally binding obligations of the Company, and all acts and things necessary have been done and performed to make this Supplemental Indenture enforceable in accordance with its terms, and the execution and delivery of this Supplemental Indenture has been duly authorized in all respects.

W I T N E S S E T H:

          NOW, THEREFORE, for and in consideration of the premises contained herein, each party agrees for the benefit of each other party and for the equal and ratable benefit of the Holders of the Notes, as follows:

ARTICLE I

DEFINITIONS

          SECTION 1.01. Capitalized Terms. Capitalized terms used but not defined in this Supplemental Indenture shall have the meanings ascribed to them in the Base Indenture.

          SECTION 1.02. References. References in this Supplemental Indenture to article and section numbers shall be deemed to be references to article and section numbers of this Supplemental Indenture unless otherwise specified.

          SECTION 1.03. Definitions. For purposes of this Supplemental Indenture, the following terms have the meanings ascribed to them as follows:

          “ Attributable Debt ” in respect of a Sale and Leaseback Transaction means, as of any particular time, the present value (discounted at the rate of interest implicit in the terms of the lease involved in such Sale and Leaseback Transaction, as determined by the Company in good faith) of the obligation of the lessee thereunder for net rental payments (excluding, however, any amounts required to be paid by the lessee, whether or not designated as rent or additional rent, on account of maintenance and repairs, services, insurance, taxes, assessments, water rates or similar charges and any amounts required to be paid by the lessee thereunder contingent upon monetary inflation or the amount of sales, maintenance and repairs, insurance, taxes, assessments, water rates or similar charges) during the remaining term of that lease (including any period for which that lease has been extended or may, at the option of the lessor, be extended).

          “ Base Indenture ” has the meaning provided in the recitals.

          “ Change of Control ” has the meaning provided in Section 4.02.

          “ Change of Control Repurchase Event ” has the meaning provided in Section 4.02.

          “ Comparable Treasury Issue ” has the meaning provided in Section 4.01.

          “ Comparable Treasury Price ” has the meaning provided in Section 4.01.

          “ Consolidated Net Tangible Assets ” means the total of all the assets appearing on the consolidated balance sheet of the Company and its Subsidiaries, less the following: (A) current liabilities; (B) intangible assets such as goodwill, trademarks, trade names, patents and unamortized debt discount and expense; and (C) appropriate adjustments on account of minority interests of other Persons holding stock in any Subsidiary of the Company.

          “ Debt ” means indebtedness for money borrowed.

          “ Depositary ” has the meaning provided in Section 2.03.

          “ Domestic Subsidiary ” means a Subsidiary formed under the laws of, or conducting its principal operations within, the United States or any State or territory thereof.

          “ Guarantee ” means any obligation, contingent or otherwise, of any Person directly or indirectly guaranteeing any Debt or other obligation of any other Person and, without limiting the generality of the foregoing, any obligation, direct or indirect, contingent or otherwise, of such Person (i) to purchase or pay (or advance or supply funds for the purchase or payment of) such Debt or other obligation of such other Person (whether arising by virtue of partnership arrangements, or by agreement to keep-well, to purchase assets, goods, securities or services, to take-or-pay, or to maintain financial statement conditions or otherwise) or (ii) entered into for purposes of assuring in any other manner the obligee of such Debt or other obligation of the payment thereof or to protect such obligee against loss in respect thereof, in whole or in part; provided that the term “Guarantee” does not include endorsements for collection or deposit in the ordinary course of business. The term “Guarantee” used as a verb has a corresponding meaning.

          “ Independent Investment Banker ” has the meaning provided in Section 4.01.

          “ Indenture ” has the meaning provided in the recitals.

          “ Interest Payment Date ” has the meaning provided in Section 2.04.

          “ Investment Grade ” has the meaning provided in Section 4.02.

          “ Lien ” means any mortgage, pledge, lien, encumbrance, charge or security interest of any kind, excluding certain liens relating to taxes, easements and similar liens arising in the ordinary course of business.

          “ Moody’s ” has the meaning provided in Section 4.02.

          “ Notes ” has the meaning provided in the recitals.

          “ Primary Treasury Dealer ” has the meaning provided in Section 4.01.

          “ Principal Property ” means any manufacturing plant or other similar facility owned by the Company or any Domestic Subsidiary, the book value of the real property, plant and equipment of which (as shown, without deduction of any depreciation reserves, on the books of the owner or owners) is not less than two percent of Consolidated Net Tangible Assets except (A) any such plant or facility which the Board of Directors determines is not of material importance to the total business conducted, or assets owned, by the Company and its Domestic Subsidiaries as an entirety or (B) any portion of any such plant or facility which the Board of Directors determines not to be of material importance to the use or operation thereof.

          “ Purchase Price ” has the meaning provided in Section 4.02.

          “ Rating Agency ” has the meaning provided in Section 4.02.

          “ Rating Category ” has the meaning provided in Section 4.02.

          “ Rating Date ” has the meaning provided in Section 4.02.

          “ Ratings Event ” has the meaning provided in Section 4.02.

          “ Redemption Date ” has the meaning provided in Section 4.02.

          “ Reference Treasury Dealer ” has the meaning provided in Section 4.01.

          “ Reference Treasury Dealer Quotations ” has the meaning provided in Section 4.01.

          “ Regular Record Date ” has the meaning provided in Section 2.04.

          “ Remaining Life ” has the meaning provided in Section 4.01.

          “ S&P ” has the meaning provided in Section 4.02.

          “ Sale and Leaseback Transaction ” means any arrangement with any Person providing for the leasing to the Company or any Domestic Subsidiary of any Principal Property or portion thereof (except for temporary leases for a term, including any renewal thereof, of not more than 36 months and except for leases between the Company and a Subsidiary or between Subsidiaries), which Principal Property (or portion thereof) has been or is to be sold or transferred by the Company or such Domestic Subsidiary to such Person.

          “ Subsidiary ” means with respect to any Person, any corporation, association or other business entity of which more than 50% of the outstanding voting stock is owned, directly or indirectly, by such Person and one or more Subsidiaries of such Person (or combination thereof). Unless otherwise specified, “Subsidiary” means a Subsidiary of the Company.

          “ Supplemental Indenture ” has the meaning provided in the preamble.

          “ Treasury Rate ” has the meaning provided in Section 4.01.

          “ Voting Stock ” has the meaning provided in Section 4.02.

ARTICLE II

GENERAL TERMS AND CONDITIONS OF THE NOTES

          SECTION 2.01. Designation and Principal Amount. The Notes are hereby authorized and are designated the 9.375% Senior Notes due 2019, initially limited in aggregate principal amount to $350,000,000. The Notes issued on the date hereof pursuant to the terms of this Indenture shall be in an aggregate principal amount of $350,000,000, which amount shall be set forth in the Company Order for the authentication and delivery of the Notes pursuant to Section 3.03 of the Base Indenture. In addition, the Company may issue, from time to time in accordance with the provisions of this Indenture, additional Notes having the same terms and conditions as the Notes issued on the date hereof in all respects (except for the payment of interest accruing prior to the issue date of such additional Notes), so that such additional Notes

shall be consolidated and form a single series with the Notes issued on the date hereof and shall be governed by the terms of the Indenture.

          SECTION 2.02. Maturity. The principal amount of the Notes shall be due and payable on June 1, 2019.

          SECTION 2.03. Form and Payment. The Notes shall be issued in substantially the form set forth on Exhibit A hereto and shall have the terms set forth in such form and shall initially be Global Securities for purposes of the Base Indenture. The Notes shall be issued in fully registered book-entry form without coupons in denominations of $2,000 and integral multiples of $1,000 in excess thereof.

          The Depositary in respect of the Notes represented by Global Securities shall be The Depository Trust Company. The Global Securities representing the Notes shall be deposited with, or on behalf of, the Depositary and shall be registered in the name of its nominee, Cede & Co. Except as otherwise set forth in Section 3.05 of the Base Indenture, the Global Securities may be transferred, in whole and not in part, only to another nominee of the Depositary or to a successor of the Depositary or its nominee.

          The Trustee shall act as Paying Agent for the Notes. The Company may choose to pay interest by mailing checks or making wire transfers. All money paid by the Company to any Paying Agent that remains unclaimed at the end of two years after the amount is due to Holders shall be repaid to the Company, subject to any applicable abandoned property laws. After such two-year period, Holders may look only to the Company for payment and not to the Trustee, any other Paying Agent or anyone else. The Company may also arrange for additional payment offices, and may cancel or change these offices, including any use of the Trustee’s Corporate Trust Office. The Company may appoint and change the Paying Agent without prior notice to the Holders.

          SECTION 2.04. Interest. Interest on the Notes shall accrue at the rate of 9.375% per annum. Interest on the Notes shall accrue from June 1, 2009 or the most recent Interest Payment Date to which interest was paid or duly provided for. Interest on the Notes shall be payable semiannually in arrears on June 1 and December 1, commencing on December 1, 2009 (each an “ Interest Payment Date ”), to the Holders in whose names the Notes are registered at the close of business on the May 15 and November 15 immediately preceding such Interest Payment Date (each a “ Regular Record Date ”). Interest on the Notes shall be computed on the basis of a 360-day year comprised of twelve 30-day months.

          SECTION 2.05. No Sinking Fund . The provisions of Article XII of the Base Indenture shall not be applicable to the Notes.

ARTICLE III

ADDITIONAL COVENANTS

          In addition to the covenants set forth in Article X of the Base Indenture, the Company also covenants and agrees for the benefit of Notes, but not Securities of any other series, as follows:

          SECTION 3.01. Limitation on Liens. The Company shall not, and will not permit any of its Domestic Subsidiaries, directly or indirectly, to issue, assume or guarantee any Debt if that Debt is secured by any Lien upon any Principal Property (or portion thereof) of the Company or of any Domestic Subsidiary of the Company or any shares of stock or Debt of any of its Domestic Subsidiaries, whether owned on June 1, 2009 or thereafter acquired, without effectively securing the Notes equally and ratably with that Debt, so long as such Debt is so secured. The foregoing restriction does not apply to:

     (i) Liens on any property acquired, constructed or improved by the Company or any Domestic Subsidiary of the Company after June 1, 2009, which are created or assumed contemporaneously with or within three years after its acquisition, or completion of construction or improvement (or within six months thereafter pursuant to a firm commitment for financing arrangements entered into within that three-year period) to secure or provide for the payment of the Purchase Price or cost thereof, or Liens existing on any property at the time of its acquisition;

     (ii) Liens existing on any property, shares of stock or indebtedness acquired from a Person merged with or into the Company or a Domestic Subsidiary of the Company after June 1, 2009;

     (iii) with respect to any corporation that becomes a Domestic Subsidiary of the Company after June 1, 2009, Liens on property of, or shares of stock or indebtedness issued by, any such corporation existing at the time it becomes a Domestic Subsidiary and not incurred in connection with or in anticipation of such corporation becoming a Domestic Subsidiary;

     (iv) Liens to secure Debt of a Domestic Subsidiary owed to the Company or Debt of one of the Domestic Subsidiaries of the Company owed to another Domestic Subsidiary of the Company;

     (v) Liens in favor of governmental bodies to secure partial, progress, advance or other payments pursuant to any contract or statute;

     (vi) any Lien existing on June 1, 2009; or

     (vii) Liens for the sole purpose of extending, renewing or replacing Debt, in whole or in part, secured by any Lien referred to in the foregoing clauses (i) to (vi), inclusive; provided , however , that the principal amount of Debt secured by that Lien shall not exceed the principal amount of Debt so secured at the time of such extension, renewal or

replacement, and that such extension, renewal or replacement shall be limited to the property that secured the Lien so extended, renewed or replaced (plus improvements on such property).

          The limitation on Liens described in this Section 3.01 shall not apply to the issuance, assumption or guarantee by the Company or any Domestic Subsidiary of the Company of Debt secured by a Lien which would otherwise be subject to the foregoing restrictions up to an aggregate amount which, together with all other Debt of the Company and of the Domestic Subsidiaries of the Company secured by Liens (not including Liens permitted under the foregoing exceptions) and the Attributable Debt with respect to Sale and Leaseback Transactions existing at that time (other than Sale and Leaseback Tran