UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Emerging growth company ☐ FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Quarterly Period Ended September 30, 2020 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Transition Period From to Commission File Number 1-12001 ALLEGHENY TECHNOLOGIES INCORPORATED (Exact name of registrant as specified in its charter) Delaware 25-17 ...