FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * Sims John D   2. Issuer Name and Ticker or Trading Symbol ALLEGHENY TECHNOLOGIES INC [ATI] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) EVP, HPMC Segment (Last) (First) (Middle) 1000 SIX PPG PLACE 3. Date of Earliest Transaction (Month/Day/Year) 02/27/2019 (Street) PITTSBURGH, PA 15222 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock, par value $0.10 per share 02/27/2019   A   19,740 (1) A $ 29.255 (2) 134,372.2071 D   Common Stock, par value $0.10 per share 02/27/2019   F   2,823 (3) D $ 29.255 (2) 131,549.2071 D   Common Stock, par value $0.10 per share 02/28/2019   M   23,678 (4) A $ 28.92 (5) 155,227.2071 D   Common Stock, par value $0.10 per share 02/28/2019   F   10,260 (6) D $ 28.92 (5) 144,697.2071 D

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Sims John D 1000 SIX PPG PLACE PITTSBURGH, PA 15222			EVP, HPMC Segment

Signatures

/s/ Elliot S. Davis, Attorney-in-Fact for John D. Sims		03/01/2019
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Award of restricted stock units granted on February 27, 2019, which are settled in shares of stock upon vesting. The award vests in three equal annual installments on each of the first three anniversaries of the grant date.
(2)	Represents the average of the high and low trading prices for one share of the Issuer's common stock on the New York Stock Exchange on February 27, 2019.
(3)	Shares withheld for payment of taxes on performance/restricted stock granted in 2014 that vested on February 27, 2019.
(4)	Settlement of performance-vested restricted stock units that were granted in 2016, the vesting of which was contingent upon the Issuer's achievement of specified performance criteria during the period from January 1, 2016 through December 31, 2018 (the "2016-2018 PSUs"). The Issuer's partial achievement of such performance criteria was certified, and a corresponding portion of the shares underlying the 2016-2018 PSUs became payable, as of February 28, 2019.
(5)	Represents the average of the high and low trading prices for one share of the Issuer's common stock on the New York Stock Exchange on February 28, 2019.
(6)	Shares withheld for payment of taxes in connection with the February 28, 2019 settlement of the 2016-2018 PSUs.

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