<SEC-DOCUMENT>0001193125-25-217804.txt : 20250925
<SEC-HEADER>0001193125-25-217804.hdr.sgml : 20250925
<ACCEPTANCE-DATETIME>20250925165848
ACCESSION NUMBER:		0001193125-25-217804
CONFORMED SUBMISSION TYPE:	8-K
PUBLIC DOCUMENT COUNT:		12
CONFORMED PERIOD OF REPORT:	20250919
ITEM INFORMATION:		Entry into a Material Definitive Agreement
ITEM INFORMATION:		Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant
ITEM INFORMATION:		Financial Statements and Exhibits
FILED AS OF DATE:		20250925
DATE AS OF CHANGE:		20250925

FILER:

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ATI INC
		CENTRAL INDEX KEY:			0001018963
		STANDARD INDUSTRIAL CLASSIFICATION:	STEEL PIPE & TUBES [3317]
		ORGANIZATION NAME:           	04 Manufacturing
		EIN:				251792394
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1228

	FILING VALUES:
		FORM TYPE:		8-K
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-12001
		FILM NUMBER:		251344499

	BUSINESS ADDRESS:	
		STREET 1:		2021 MCKINNEY AVENUE
		CITY:			DALLAS
		STATE:			TX
		ZIP:			75201
		BUSINESS PHONE:		4123942800

	MAIL ADDRESS:	
		STREET 1:		2021 MCKINNEY AVENUE
		CITY:			DALLAS
		STATE:			TX
		ZIP:			75201

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ALLEGHENY TECHNOLOGIES INC
		DATE OF NAME CHANGE:	19991213

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ALLEGHENY TELEDYNE INC
		DATE OF NAME CHANGE:	19960716
</SEC-HEADER>
<DOCUMENT>
<TYPE>8-K
<SEQUENCE>1
<FILENAME>d911457d8k.htm
<DESCRIPTION>8-K
<TEXT>
<XBRL>
<?xml version='1.0' encoding='ASCII'?>
<html xmlns:dei="http://xbrl.sec.gov/dei/2025" xmlns:us-types="http://fasb.org/us-types/2025" xmlns:nonnum="http://www.xbrl.org/dtr/type/non-numeric" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:ati="http://www.atimetals.com/20250919" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:utr="http://www.xbrl.org/2009/utr" xmlns:iso4217="http://www.xbrl.org/2003/iso4217" xmlns:ix="http://www.xbrl.org/2013/inlineXBRL" xmlns:ixt="http://www.xbrl.org/inlineXBRL/transformation/2015-02-26" xmlns:ixt-sec="http://www.sec.gov/inlineXBRL/transformation/2015-08-31" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:xbrldi="http://xbrl.org/2006/xbrldi" xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>8-K</title>
<meta http-equiv="Content-Type" content="text/html"/>
</head>
   <body><div style="display:none"> <ix:header> <ix:hidden> <ix:nonNumeric id="Hidden_dei_EntityRegistrantName" name="dei:EntityRegistrantName" contextRef="duration_2025-09-19_to_2025-09-19">ATI INC</ix:nonNumeric> <ix:nonNumeric name="dei:AmendmentFlag" contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-247">false</ix:nonNumeric> <ix:nonNumeric id="Hidden_dei_EntityCentralIndexKey" name="dei:EntityCentralIndexKey" contextRef="duration_2025-09-19_to_2025-09-19">0001018963</ix:nonNumeric> </ix:hidden> <ix:references> <link:schemaRef xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:link="http://www.xbrl.org/2003/linkbase" xlink:type="simple" xlink:href="ati-20250919.xsd" xlink:arcrole="http://www.xbrl.org/2003/linkbase"/> </ix:references> <ix:resources> <xbrli:context id="duration_2025-09-19_to_2025-09-19"> <xbrli:entity> <xbrli:identifier scheme="http://www.sec.gov/CIK">0001018963</xbrli:identifier> </xbrli:entity> <xbrli:period> <xbrli:startDate>2025-09-19</xbrli:startDate> <xbrli:endDate>2025-09-19</xbrli:endDate> </xbrli:period> </xbrli:context> </ix:resources> </ix:header> </div> <div style="text-align:center"> <div style="width:8.5in;text-align:left;margin-left: auto;margin-right: auto"> <div style="line-height:1.0pt;margin-top:0pt;margin-bottom:0pt;border-bottom:1px solid #000000">&#160;</div> <div style="line-height:3.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000">&#160;</div> <p style="margin-top:8pt; margin-bottom:0pt; font-size:18pt; font-family:Times New Roman;font-weight:bold;text-align:center">UNITED STATES</p> <p style="margin-top:0pt; margin-bottom:0pt; font-size:18pt; font-family:Times New Roman;font-weight:bold;text-align:center">SECURITIES AND EXCHANGE COMMISSION</p> <p style="margin-top:0pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman;font-weight:bold;text-align:center">Washington, DC 20549</p> <p style="font-size:10pt;margin-top:0pt;margin-bottom:0pt">&#160;</p> <div style="text-align:center"> <div style="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%;text-align:center;margin-left: auto;margin-right: auto">&#160;</div></div> <p style="margin-top:10pt; margin-bottom:0pt; font-size:18pt; font-family:Times New Roman;font-weight:bold;text-align:center">FORM <span style="white-space:nowrap"><ix:nonNumeric name="dei:DocumentType" contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-258">8-K</ix:nonNumeric></span></p> <p style="font-size:10pt;margin-top:0pt;margin-bottom:0pt">&#160;</p> <div style="text-align:center"> <div style="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%;text-align:center;margin-left: auto;margin-right: auto">&#160;</div></div> <p style="margin-top:10pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman;font-weight:bold;text-align:center">CURRENT REPORT</p> <p style="margin-top:0pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman;font-weight:bold;text-align:center">Pursuant to Section&#160;13 or 15(d)</p> <p style="margin-top:0pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman;font-weight:bold;text-align:center">of the Securities Exchange Act of 1934</p> <p style="margin-top:10pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman;font-weight:bold;text-align:center">Date of Report (Date of earliest event reported): September 25, 2025 (<ix:nonNumeric name="dei:DocumentPeriodEndDate" contextRef="duration_2025-09-19_to_2025-09-19" format="ixt:datemonthdayyearen" id="ixv-259">September 19, 2025</ix:nonNumeric>)</p> <p style="font-size:10pt;margin-top:0pt;margin-bottom:0pt">&#160;</p> <div style="text-align:center"> <div style="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%;text-align:center;margin-left: auto;margin-right: auto">&#160;</div></div> <p style="margin-top:10pt; margin-bottom:0pt; font-size:24pt; font-family:Times New Roman;font-weight:bold;text-align:center"> <span style=" -sec-ix-hidden:Hidden_dei_EntityRegistrantName">ATI Inc.</span> </p> <p style="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman;font-weight:bold;text-align:center">(Exact name of registrant as specified in its charter)</p> <p style="font-size:10pt;margin-top:0pt;margin-bottom:0pt">&#160;</p> <div style="text-align:center"> <div style="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%;text-align:center;margin-left: auto;margin-right: auto">&#160;</div></div> <p style="font-size:10pt;margin-top:0pt;margin-bottom:0pt">&#160;</p>
<table cellspacing="0" cellpadding="0" style="border-collapse:collapse; font-family:Times New Roman; font-size:8pt;width:100%;border-spacing:0;margin:0 auto">
<tr>
<td style="width:34%"/>
<td style="vertical-align:bottom"/>
<td style="width:32%"/>
<td style="vertical-align:bottom;width:1%"/>
<td style="width:32%"/></tr>
<tr style="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<td style="vertical-align:top;text-align:center"><span style="font-weight:bold"><ix:nonNumeric name="dei:EntityIncorporationStateCountryCode" contextRef="duration_2025-09-19_to_2025-09-19" format="ixt-sec:stateprovnameen" id="ixv-260">Delaware</ix:nonNumeric></span></td>
<td style="vertical-align:bottom">&#160;</td>
<td style="vertical-align:top;text-align:center"><span style="font-weight:bold"><span style="white-space:nowrap"><ix:nonNumeric name="dei:EntityFileNumber" contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-261">1-12001</ix:nonNumeric></span></span></td>
<td style="vertical-align:bottom">&#160;</td>
<td style="vertical-align:top;text-align:center"><span style="font-weight:bold"><span style="white-space:nowrap"><ix:nonNumeric name="dei:EntityTaxIdentificationNumber" contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-262">25-1792394</ix:nonNumeric></span></span></td></tr>
<tr style="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<td style="vertical-align:top;text-align:center"><span style="font-weight:bold">(State or other jurisdiction<br/>of incorporation)</span></td>
<td style="vertical-align:bottom">&#160;</td>
<td style="vertical-align:top;text-align:center"> <p style="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman;font-weight:bold;text-align:center">(Commission</p> <p style="margin-top:0pt; margin-bottom:1pt; font-size:8pt; font-family:Times New Roman;font-weight:bold;text-align:center">File Number)</p></td>
<td style="vertical-align:bottom">&#160;</td>
<td style="vertical-align:top;text-align:center"><span style="font-weight:bold">(IRS Employer<br/>Identification No.)</span></td></tr></table> <p style="font-size:10pt;margin-top:0pt;margin-bottom:0pt">&#160;</p>
<table cellspacing="0" cellpadding="0" style="border-collapse:collapse; font-family:Times New Roman; font-size:10pt;width:100%;border-spacing:0;margin:0 auto">
<tr>
<td style="width:50%"/>
<td style="vertical-align:bottom;width:1%"/>
<td style="width:48%"/></tr>
<tr style="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<td style="vertical-align:bottom;text-align:center"><span style="font-weight:bold"><ix:nonNumeric name="dei:EntityAddressAddressLine1" contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-263">2021 McKinney Avenue</ix:nonNumeric>, <ix:nonNumeric name="dei:EntityAddressCityOrTown" contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-264">Dallas</ix:nonNumeric>, <ix:nonNumeric name="dei:EntityAddressStateOrProvince" contextRef="duration_2025-09-19_to_2025-09-19" format="ixt-sec:stateprovnameen" id="ixv-265">Texas</ix:nonNumeric></span></td>
<td style="vertical-align:bottom">&#160;</td>
<td style="vertical-align:bottom;white-space:nowrap;text-align:center"><span style="font-weight:bold"><ix:nonNumeric name="dei:EntityAddressPostalZipCode" contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-266">75201</ix:nonNumeric></span></td></tr>
<tr style="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<td style="vertical-align:top;text-align:center"><span style="font-weight:bold">(Address of principal executive offices)</span></td>
<td style="vertical-align:bottom">&#160;</td>
<td style="vertical-align:top;text-align:center"><span style="font-weight:bold">(Zip Code)</span></td></tr></table> <p style="margin-top:10pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman;font-weight:bold;text-align:center">Registrant&#8217;s telephone number, including area code <ix:nonNumeric name="dei:CityAreaCode" contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-267">(800)</ix:nonNumeric> <ix:nonNumeric name="dei:LocalPhoneNumber" contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-268">289-7545</ix:nonNumeric></p> <p style="margin-top:10pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman;font-weight:bold;text-align:center">N/A</p> <p style="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman;font-weight:bold;text-align:center">(Former name or former address, if changed since last report).</p> <p style="font-size:10pt;margin-top:0pt;margin-bottom:0pt">&#160;</p> <div style="text-align:center"> <div style="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%;text-align:center;margin-left: auto;margin-right: auto">&#160;</div></div> <p style="margin-top:10pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Check the appropriate box below if the Form <span style="white-space:nowrap">8-K</span> filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (<span style="font-style:italic">see</span> General Instruction A.2. below):</p> <p style="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&#160;</p>
<table style="border-collapse:collapse; font-family:Times New Roman; font-size:10pt;border-spacing:0;width:100%" cellpadding="0" cellspacing="0">
<tr style="page-break-inside:avoid">
<td style="width:4%">&#160;</td>
<td style="width:5%;vertical-align:top;text-align:left"><ix:nonNumeric name="dei:WrittenCommunications" contextRef="duration_2025-09-19_to_2025-09-19" format="ixt-sec:boolballotbox" id="ixv-269">&#9744;</ix:nonNumeric></td>
<td style="vertical-align:top;text-align:left"> <p style=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman;text-align:left">Written communication pursuant to Rule 425 under the Securities Act (17 CFR 230.425)</p></td></tr></table> <p style="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&#160;</p>
<table style="border-collapse:collapse; font-family:Times New Roman; font-size:10pt;border-spacing:0;width:100%" cellpadding="0" cellspacing="0">
<tr style="page-break-inside:avoid">
<td style="width:4%">&#160;</td>
<td style="width:5%;vertical-align:top;text-align:left"><ix:nonNumeric name="dei:SolicitingMaterial" contextRef="duration_2025-09-19_to_2025-09-19" format="ixt-sec:boolballotbox" id="ixv-270">&#9744;</ix:nonNumeric></td>
<td style="vertical-align:top;text-align:left"> <p style=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman;text-align:left">Soliciting material pursuant to Rule <span style="white-space:nowrap">14a-12</span> under the Exchange Act (17 CFR <span style="white-space:nowrap">240.14a-12)</span></p></td></tr></table> <p style="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&#160;</p>
<table style="border-collapse:collapse; font-family:Times New Roman; font-size:10pt;border-spacing:0;width:100%" cellpadding="0" cellspacing="0">
<tr style="page-break-inside:avoid">
<td style="width:4%">&#160;</td>
<td style="width:5%;vertical-align:top;text-align:left"><ix:nonNumeric name="dei:PreCommencementTenderOffer" contextRef="duration_2025-09-19_to_2025-09-19" format="ixt-sec:boolballotbox" id="ixv-271">&#9744;</ix:nonNumeric></td>
<td style="vertical-align:top;text-align:left"> <p style=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman;text-align:left"><span style="white-space:nowrap">Pre-commencement</span> communication pursuant to Rule <span style="white-space:nowrap">14d-2(b)</span> under the Exchange Act (17 CFR <span style="white-space:nowrap">240.14d-2(b))</span></p></td></tr></table> <p style="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&#160;</p>
<table style="border-collapse:collapse; font-family:Times New Roman; font-size:10pt;border-spacing:0;width:100%" cellpadding="0" cellspacing="0">
<tr style="page-break-inside:avoid">
<td style="width:4%">&#160;</td>
<td style="width:5%;vertical-align:top;text-align:left"><ix:nonNumeric name="dei:PreCommencementIssuerTenderOffer" contextRef="duration_2025-09-19_to_2025-09-19" format="ixt-sec:boolballotbox" id="ixv-272">&#9744;</ix:nonNumeric></td>
<td style="vertical-align:top;text-align:left"> <p style=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman;text-align:left"><span style="white-space:nowrap">Pre-commencement</span> communication pursuant to Rule <span style="white-space:nowrap">13e-4(c)</span> under the Exchange Act (17 CFR <span style="white-space:nowrap">240.13e-4(c))</span></p></td></tr></table> <p style="margin-top:10pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Securities registered pursuant to Section&#160;12(b) of the Act:</p> <p style="font-size:10pt;margin-top:0pt;margin-bottom:0pt">&#160;</p>
<table cellspacing="0" cellpadding="0" style="border-collapse:collapse; font-family:Times New Roman; font-size:8pt;width:100%;border-spacing:0;margin:0 auto">
<tr>
<td style="width:34%"/>
<td style="vertical-align:bottom"/>
<td style="width:32%"/>
<td style="vertical-align:bottom;width:1%"/>
<td style="width:32%"/></tr>
<tr style="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<td style="border-bottom:1.00pt solid #000000;vertical-align:bottom;white-space:nowrap;text-align:center"> <p style="margin-top:0pt; margin-bottom:1pt; font-size:8pt; font-family:Times New Roman;font-weight:bold;text-align:center">Title of each class</p></td>
<td style="vertical-align:bottom">&#160;</td>
<td style="border-bottom:1.00pt solid #000000;vertical-align:bottom;text-align:center"> <p style="margin-top:0pt; margin-bottom:1pt; font-size:8pt; font-family:Times New Roman;font-weight:bold;text-align:center">Trading<br/>Symbol(s)</p></td>
<td style="vertical-align:bottom">&#160;</td>
<td style="border-bottom:1.00pt solid #000000;vertical-align:bottom;text-align:center"> <p style="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman;font-weight:bold;text-align:center">Name of each exchange</p> <p style="margin-top:0pt; margin-bottom:1pt; font-size:8pt; font-family:Times New Roman;font-weight:bold;text-align:center">on which registered</p></td></tr>
<tr style="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<td style="vertical-align:top;text-align:center"><ix:nonNumeric name="dei:Security12bTitle" contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-273">Common Stock, par value $0.10 per share</ix:nonNumeric></td>
<td style="vertical-align:bottom">&#160;</td>
<td style="vertical-align:top;text-align:center"><ix:nonNumeric name="dei:TradingSymbol" contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-274">ATI</ix:nonNumeric></td>
<td style="vertical-align:bottom">&#160;</td>
<td style="vertical-align:top;text-align:center"><ix:nonNumeric name="dei:SecurityExchangeName" contextRef="duration_2025-09-19_to_2025-09-19" format="ixt-sec:exchnameen" id="ixv-275">New York Stock Exchange</ix:nonNumeric></td></tr></table> <p style="margin-top:10pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR &#167;230.405) or Rule <span style="white-space:nowrap">12b-2</span> of the Securities Exchange Act of 1934 (17 CFR <span style="white-space:nowrap">&#167;240.12b-2).</span></p> <p style="margin-top:10pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman;text-align:right">Emerging growth company&#8194;<ix:nonNumeric name="dei:EntityEmergingGrowthCompany" contextRef="duration_2025-09-19_to_2025-09-19" format="ixt-sec:boolballotbox" id="ixv-276">&#9744;</ix:nonNumeric></p> <p style="margin-top:10pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section&#160;13(a) of the Exchange Act.&#8194;&#9744;</p> <p style="font-size:10pt;margin-top:0pt;margin-bottom:0pt">&#160;</p> <div style="line-height:1.0pt;margin-top:0pt;margin-bottom:0pt;border-bottom:1px solid #000000">&#160;</div> <div style="line-height:3.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000">&#160;</div></div></div>

<p style="margin-top:1em; margin-bottom:0em; page-break-before:always"> </p>
<hr style="color:#999999;height:3px;width:100%;clear:both"/>

<div style="text-align:center"><div style="width:8.5in;text-align:left;margin-left: auto;margin-right: auto">

<table style="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt;border-spacing:0;width:100%" cellpadding="0" cellspacing="0">
<tr style="page-break-inside:avoid">
<td style="width:11%;vertical-align:top;text-align:left"><span style="font-weight:bold">Item&#8201;1.01</span></td>
<td style="vertical-align:top;text-align:left"> <p style=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman;font-weight:bold;text-align:left">Entry into a Material Definitive Agreement. </p></td></tr></table> <p style="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">On September&#160;19, 2025, ATI Specialty Materials, LLC (the &#8220;Company&#8221;), an indirect wholly-owned subsidiary of ATI Inc. (&#8220;ATI&#8221;), entered into a three-year,&#160;$125&#160;million accounts receivable securitization facility (the &#8220;Facility&#8221;) pursuant to (i)&#160;a First Tier Purchase and Sale Agreement (the &#8220;First Tier Agreement&#8221;) among the Company, as Servicer and as the Originator, and ATI Securitization Holdings LLC, a bankruptcy-remote special purpose entity that is a direct wholly-owned subsidiary of the Company (&#8220;Holdings&#8221;), as Buyer, (ii)&#160;a Second Tier Purchase and Sale and Agreement (the &#8220;Second Tier Agreement&#8221;) among the Company, as Servicer, Holdings, as Seller, and ATI Securitization LLC, a bankruptcy-remote special purpose entity that is a direct wholly-owned subsidiary of Holdings (the &#8220;SPE&#8221;), and (iii)&#160;a Receivables Purchase and Financing Agreement (the &#8220;Receivables Purchase and Financing Agreement&#8221; and, together with the First Tier Agreement and the Second Tier Agreement, the &#8220;Agreements&#8221;) among the SPE, the Company, as Servicer (the &#8220;Servicer&#8221;), the purchaser/lenders that are parties thereto from time to time (collectively, the &#8220;Purchaser/Lenders&#8221;), and PNC Bank, National Association, as Administrative Agent (the &#8220;Administrative Agent&#8221;), and PNC Capital Markets LLC, as Structuring Agent. </p> <p style="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Under the Agreements, the Originator has sold or contributed, and will continue to sell or contribute on an ongoing basis, certain of its receivables, to Holdings which, in turn, has sold or contributed, and will continue to sell or contribute, all such receivables to the SPE. The SPE may borrow and incur indebtedness from, and/or sell receivables to, the Purchaser/Lenders in an amount not to exceed $125&#160;million in the aggregate. </p> <p style="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Amounts outstanding under the Receivables Purchase and Financing Agreement accrue interest based on either the forward-looking term rate based on the secured overnight financing rate as administered by the Federal Reserve Bank of New York (&#8220;SOFR Rate&#8221;) for a <span style="white-space:nowrap">one-month</span> period or the daily SOFR Rate for a period of one month as of the date of incurrence, as selected by the SPE. The Agreements include customary fees, conditions, representations and warranties, indemnification provisions, covenants and events of default. Receivables in the Facility are subject to certain criteria, limits and reserves. </p> <p style="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">As of September&#160;25, 2025, approximately $80&#160;million of loans and/or investments were outstanding under the Facility. The Facility has a three-year term. </p> <p style="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Certain of the Secured Parties and their affiliates have provided and may, from time to time, continue to provide investment banking, financial advisory, lending and/or commercial banking services to ATI, the Company and their affiliates, for which they have received, and may in the future receive, customary compensation and reimbursement of expenses. </p> <p style="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&#160;</p>
<table style="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt;border-spacing:0;width:100%" cellpadding="0" cellspacing="0">
<tr style="page-break-inside:avoid">
<td style="width:11%;vertical-align:top;text-align:left"><span style="font-weight:bold">Item&#8201;2.03</span></td>
<td style="vertical-align:top;text-align:left"> <p style=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman;font-weight:bold;text-align:left">Creation of a Direct Financial Obligation or an Obligation under <span style="white-space:nowrap">an&#160;Off-Balance&#160;Sheet</span> </p></td></tr></table> <p style="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman;font-weight:bold">Arrangement of a Registrant. </p> <p style="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The disclosure set forth in Item 1.01 of this Current Report is incorporated by reference into this Item 2.03. </p> <p style="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&#160;</p>
<table style="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt;border-spacing:0;width:100%" cellpadding="0" cellspacing="0">
<tr style="page-break-inside:avoid">
<td style="width:11%;vertical-align:top;text-align:left"><span style="font-weight:bold">Item&#8201;9.01.</span></td>
<td style="vertical-align:top;text-align:left"> <p style=" margin-top:0pt ; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman;font-weight:bold;text-align:left">Exhibit </p></td></tr></table> <p style="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&#160;</p>
<table cellspacing="0" cellpadding="0" style="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt;width:100%;border-spacing:0;margin:0 auto">


<tr>

<td/>

<td style="vertical-align:bottom;width:2%"/>
<td style="width:3%"/>

<td style="vertical-align:bottom;width:1%"/>
<td style="width:92%"/></tr>


<tr style="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<td style="vertical-align:top;white-space:nowrap">(d)</td>
<td style="vertical-align:bottom">&#160;&#160;</td>
<td style="vertical-align:top;white-space:nowrap">104</td>
<td style="vertical-align:bottom">&#160;&#160;</td>
<td style="vertical-align:top;white-space:nowrap">Cover Page Interactive Data File</td></tr>
</table> <p style="font-size:18pt; margin-top:0pt; margin-bottom:0pt">&#160;</p>
</div></div>



<p style="margin-top:1em; margin-bottom:0em; page-break-before:always"> </p>
<hr style="color:#999999;height:3px;width:100%;clear:both"/>

<div style="text-align:center"><div style="width:8.5in;text-align:left;margin-left: auto;margin-right: auto">
 <p style="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman;font-weight:bold;text-align:center"><span style="text-decoration:underline">SIGNATURE </span></p> <p style="margin-top:12pt; margin-bottom:0pt; text-indent:9%; font-size:10pt; font-family:Times New Roman">Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. </p> <p style="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&#160;</p><div>
<table cellspacing="0" cellpadding="0" style="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt;width:40%;border-spacing:0;margin-left:auto">


<tr>

<td style="width:7%"/>

<td style="vertical-align:bottom;width:1%"/>
<td style="width:92%"/></tr>


<tr style="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<td style="vertical-align:top" colspan="3">ATI Inc.</td></tr>
<tr style="font-size:1pt">
<td style="height:12pt"/>
<td style="height:12pt" colspan="2"/></tr>
<tr style="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<td style="vertical-align:top">By:</td>
<td style="vertical-align:bottom">&#160;</td>
<td style="vertical-align:bottom;white-space:nowrap"> <p style="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">/s/ Donald P. Newman</p></td></tr>
<tr style="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<td style="vertical-align:bottom"/>
<td style="vertical-align:bottom">&#160;</td>
<td style="vertical-align:bottom">Donald P. Newman</td></tr>
<tr style="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<td style="vertical-align:bottom"/>
<td style="vertical-align:bottom">&#160;</td>
<td style="vertical-align:bottom;white-space:nowrap">Executive Vice President, Finance and Chief Financial Officer</td></tr>
</table></div> <p style="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Dated: September&#160;25, 2025 </p>
</div></div>

</body></html>
</XBRL>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-101.SCH
<SEQUENCE>2
<FILENAME>ati-20250919.xsd
<DESCRIPTION>XBRL TAXONOMY EXTENSION SCHEMA
<TEXT>
<XBRL>
<?xml version="1.0" encoding="us-ascii"?>
<!-- DFIN - https://www.dfinsolutions.com/ -->
<!-- CTU Version: Release 2512 Build:20250722.1 -->
<!-- Creation date: 9/26/2025 12:20:16 AM Eastern Time -->
<!-- Copyright (c) 2025 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
<xsd:schema
  xmlns:nonnum="http://www.xbrl.org/dtr/type/non-numeric"
  xmlns:num="http://www.xbrl.org/dtr/type/numeric"
  xmlns:us-types="http://fasb.org/us-types/2025"
  xmlns:ati="http://www.atimetals.com/20250919"
  xmlns:dei="http://xbrl.sec.gov/dei/2025"
  xmlns:xbrli="http://www.xbrl.org/2003/instance"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:xlink="http://www.w3.org/1999/xlink"
  xmlns:xbrldt="http://xbrl.org/2005/xbrldt"
  attributeFormDefault="unqualified"
  elementFormDefault="qualified"
  targetNamespace="http://www.atimetals.com/20250919"
  xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <xsd:import schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" namespace="http://www.xbrl.org/2003/instance" />
    <xsd:import schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" namespace="http://www.xbrl.org/2003/linkbase" />
    <xsd:import schemaLocation="https://xbrl.sec.gov/dei/2025/dei-2025.xsd" namespace="http://xbrl.sec.gov/dei/2025" />
    <xsd:import schemaLocation="http://www.xbrl.org/dtr/type/numeric-2009-12-16.xsd" namespace="http://www.xbrl.org/dtr/type/numeric" />
    <xsd:import schemaLocation="http://www.xbrl.org/dtr/type/nonNumeric-2009-12-16.xsd" namespace="http://www.xbrl.org/dtr/type/non-numeric" />
    <xsd:import schemaLocation="https://xbrl.sec.gov/naics/2025/naics-2025.xsd" namespace="http://xbrl.sec.gov/naics/2025" />
    <xsd:import schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" namespace="http://xbrl.org/2005/xbrldt" />
  <xsd:annotation>
    <xsd:appinfo>
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="ati-20250919_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:title="Label Links, all" xlink:type="simple" />
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="ati-20250919_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:title="Presentation Links, all" xlink:type="simple" />
      <link:roleType roleURI="http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation" id="Role_DocumentDocumentAndEntityInformation">
        <link:definition>100000 - Document - Document and Entity Information</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
    </xsd:appinfo>
  </xsd:annotation>
</xsd:schema>
</XBRL>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-101.LAB
<SEQUENCE>3
<FILENAME>ati-20250919_lab.xml
<DESCRIPTION>XBRL TAXONOMY EXTENSION LABEL LINKBASE
<TEXT>
<XBRL>
<?xml version="1.0" encoding="us-ascii" standalone="yes"?>
<!-- DFIN - https://www.dfinsolutions.com/ -->
<!-- CTU Version: Release 2512 Build:20250722.1 -->
<!-- Creation date: 9/26/2025 12:20:16 AM Eastern Time -->
<!-- Copyright (c) 2025 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
<link:linkbase
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:xlink="http://www.w3.org/1999/xlink"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:labelLink xlink:role="http://www.xbrl.org/2003/role/link" xlink:type="extended">
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CoverAbstract" xlink:type="locator" xlink:label="dei_CoverAbstract" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_CoverAbstract" xlink:to="dei_CoverAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_CoverAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Cover [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_CoverAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cover [Abstract]</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName" xlink:type="locator" xlink:label="dei_EntityRegistrantName" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityRegistrantName" xlink:to="dei_EntityRegistrantName_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityRegistrantName_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Registrant Name</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_EntityRegistrantName_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Registrant Name</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag" xlink:type="locator" xlink:label="dei_AmendmentFlag" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_AmendmentFlag" xlink:to="dei_AmendmentFlag_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_AmendmentFlag_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Amendment Flag</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_AmendmentFlag_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amendment Flag</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey" xlink:type="locator" xlink:label="dei_EntityCentralIndexKey" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityCentralIndexKey" xlink:to="dei_EntityCentralIndexKey_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Central Index Key</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Central Index Key</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentType" xlink:type="locator" xlink:label="dei_DocumentType" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentType" xlink:to="dei_DocumentType_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_DocumentType_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Document Type</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_DocumentType_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Type</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentPeriodEndDate" xlink:type="locator" xlink:label="dei_DocumentPeriodEndDate" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentPeriodEndDate" xlink:to="dei_DocumentPeriodEndDate_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Document Period End Date</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Period End Date</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityIncorporationStateCountryCode" xlink:type="locator" xlink:label="dei_EntityIncorporationStateCountryCode" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityIncorporationStateCountryCode" xlink:to="dei_EntityIncorporationStateCountryCode_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityIncorporationStateCountryCode_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Incorporation State Country Code</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_EntityIncorporationStateCountryCode_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Incorporation State Country Code</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFileNumber" xlink:type="locator" xlink:label="dei_EntityFileNumber" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityFileNumber" xlink:to="dei_EntityFileNumber_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityFileNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity File Number</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_EntityFileNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity File Number</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityTaxIdentificationNumber" xlink:type="locator" xlink:label="dei_EntityTaxIdentificationNumber" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityTaxIdentificationNumber" xlink:to="dei_EntityTaxIdentificationNumber_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityTaxIdentificationNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Tax Identification Number</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_EntityTaxIdentificationNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Tax Identification Number</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine1" xlink:type="locator" xlink:label="dei_EntityAddressAddressLine1" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressAddressLine1" xlink:to="dei_EntityAddressAddressLine1_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, Address Line One</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Address Line One</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressCityOrTown" xlink:type="locator" xlink:label="dei_EntityAddressCityOrTown" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressCityOrTown" xlink:to="dei_EntityAddressCityOrTown_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, City or Town</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, City or Town</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressStateOrProvince" xlink:type="locator" xlink:label="dei_EntityAddressStateOrProvince" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressStateOrProvince" xlink:to="dei_EntityAddressStateOrProvince_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, State or Province</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, State or Province</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressPostalZipCode" xlink:type="locator" xlink:label="dei_EntityAddressPostalZipCode" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressPostalZipCode" xlink:to="dei_EntityAddressPostalZipCode_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, Postal Zip Code</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Postal Zip Code</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CityAreaCode" xlink:type="locator" xlink:label="dei_CityAreaCode" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_CityAreaCode" xlink:to="dei_CityAreaCode_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_CityAreaCode_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">City Area Code</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_CityAreaCode_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">City Area Code</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LocalPhoneNumber" xlink:type="locator" xlink:label="dei_LocalPhoneNumber" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_LocalPhoneNumber" xlink:to="dei_LocalPhoneNumber_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_LocalPhoneNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Local Phone Number</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_LocalPhoneNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Local Phone Number</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_WrittenCommunications" xlink:type="locator" xlink:label="dei_WrittenCommunications" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_WrittenCommunications" xlink:to="dei_WrittenCommunications_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_WrittenCommunications_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Written Communications</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_WrittenCommunications_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Written Communications</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SolicitingMaterial" xlink:type="locator" xlink:label="dei_SolicitingMaterial" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_SolicitingMaterial" xlink:to="dei_SolicitingMaterial_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_SolicitingMaterial_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Soliciting Material</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_SolicitingMaterial_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Soliciting Material</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementTenderOffer" xlink:type="locator" xlink:label="dei_PreCommencementTenderOffer" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_PreCommencementTenderOffer" xlink:to="dei_PreCommencementTenderOffer_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_PreCommencementTenderOffer_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Pre Commencement Tender Offer</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_PreCommencementTenderOffer_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pre Commencement Tender Offer</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementIssuerTenderOffer" xlink:type="locator" xlink:label="dei_PreCommencementIssuerTenderOffer" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_PreCommencementIssuerTenderOffer" xlink:to="dei_PreCommencementIssuerTenderOffer_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_PreCommencementIssuerTenderOffer_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Pre Commencement Issuer Tender Offer</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_PreCommencementIssuerTenderOffer_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pre Commencement Issuer Tender Offer</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_Security12bTitle" xlink:type="locator" xlink:label="dei_Security12bTitle" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_Security12bTitle" xlink:to="dei_Security12bTitle_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_Security12bTitle_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Security 12b Title</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_Security12bTitle_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Security 12b Title</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_TradingSymbol" xlink:type="locator" xlink:label="dei_TradingSymbol" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_TradingSymbol" xlink:to="dei_TradingSymbol_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_TradingSymbol_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Trading Symbol</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_TradingSymbol_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Trading Symbol</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SecurityExchangeName" xlink:type="locator" xlink:label="dei_SecurityExchangeName" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_SecurityExchangeName" xlink:to="dei_SecurityExchangeName_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_SecurityExchangeName_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Security Exchange Name</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_SecurityExchangeName_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Security Exchange Name</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany" xlink:type="locator" xlink:label="dei_EntityEmergingGrowthCompany" />
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityEmergingGrowthCompany" xlink:to="dei_EntityEmergingGrowthCompany_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityEmergingGrowthCompany_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Emerging Growth Company</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_EntityEmergingGrowthCompany_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Emerging Growth Company</link:label>
  </link:labelLink>
</link:linkbase>
</XBRL>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-101.PRE
<SEQUENCE>4
<FILENAME>ati-20250919_pre.xml
<DESCRIPTION>XBRL TAXONOMY EXTENSION PRESENTATION LINKBASE
<TEXT>
<XBRL>
<?xml version="1.0" encoding="us-ascii" standalone="yes"?>
<!-- DFIN - https://www.dfinsolutions.com/ -->
<!-- CTU Version: Release 2512 Build:20250722.1 -->
<!-- Creation date: 9/26/2025 12:20:16 AM Eastern Time -->
<!-- Copyright (c) 2025 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
<link:linkbase
    xmlns:link="http://www.xbrl.org/2003/linkbase"
    xmlns:xlink="http://www.w3.org/1999/xlink"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:xbrldt="http://xbrl.org/2005/xbrldt"
    xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:roleRef roleURI="http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation" xlink:href="ati-20250919.xsd#Role_DocumentDocumentAndEntityInformation" xlink:type="simple" />
  <link:presentationLink xlink:type="extended" xlink:role="http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation">
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CoverAbstract" xlink:type="locator" xlink:label="dei_CoverAbstract" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName" xlink:type="locator" xlink:label="dei_EntityRegistrantName" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityRegistrantName" order="22.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag" xlink:type="locator" xlink:label="dei_AmendmentFlag" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_AmendmentFlag" order="23.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey" xlink:type="locator" xlink:label="dei_EntityCentralIndexKey" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityCentralIndexKey" order="24.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentType" xlink:type="locator" xlink:label="dei_DocumentType" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_DocumentType" order="26.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentPeriodEndDate" xlink:type="locator" xlink:label="dei_DocumentPeriodEndDate" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_DocumentPeriodEndDate" order="27.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityIncorporationStateCountryCode" xlink:type="locator" xlink:label="dei_EntityIncorporationStateCountryCode" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityIncorporationStateCountryCode" order="28.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFileNumber" xlink:type="locator" xlink:label="dei_EntityFileNumber" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityFileNumber" order="29.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityTaxIdentificationNumber" xlink:type="locator" xlink:label="dei_EntityTaxIdentificationNumber" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityTaxIdentificationNumber" order="30.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine1" xlink:type="locator" xlink:label="dei_EntityAddressAddressLine1" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityAddressAddressLine1" order="31.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressCityOrTown" xlink:type="locator" xlink:label="dei_EntityAddressCityOrTown" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityAddressCityOrTown" order="32.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressStateOrProvince" xlink:type="locator" xlink:label="dei_EntityAddressStateOrProvince" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityAddressStateOrProvince" order="33.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressPostalZipCode" xlink:type="locator" xlink:label="dei_EntityAddressPostalZipCode" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityAddressPostalZipCode" order="34.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CityAreaCode" xlink:type="locator" xlink:label="dei_CityAreaCode" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_CityAreaCode" order="35.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LocalPhoneNumber" xlink:type="locator" xlink:label="dei_LocalPhoneNumber" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_LocalPhoneNumber" order="36.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_WrittenCommunications" xlink:type="locator" xlink:label="dei_WrittenCommunications" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_WrittenCommunications" order="37.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SolicitingMaterial" xlink:type="locator" xlink:label="dei_SolicitingMaterial" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_SolicitingMaterial" order="38.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementTenderOffer" xlink:type="locator" xlink:label="dei_PreCommencementTenderOffer" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_PreCommencementTenderOffer" order="39.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementIssuerTenderOffer" xlink:type="locator" xlink:label="dei_PreCommencementIssuerTenderOffer" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_PreCommencementIssuerTenderOffer" order="40.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_Security12bTitle" xlink:type="locator" xlink:label="dei_Security12bTitle" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_Security12bTitle" order="41.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_TradingSymbol" xlink:type="locator" xlink:label="dei_TradingSymbol" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_TradingSymbol" order="42.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SecurityExchangeName" xlink:type="locator" xlink:label="dei_SecurityExchangeName" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_SecurityExchangeName" order="43.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany" xlink:type="locator" xlink:label="dei_EntityEmergingGrowthCompany" />
    <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityEmergingGrowthCompany" order="44.001" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
  </link:presentationLink>
</link:linkbase>
</XBRL>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>XML
<SEQUENCE>6
<FILENAME>R1.htm
<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="include/report.css">
<script type="text/javascript" src="Show.js">/* Do Not Remove This Comment */</script><script type="text/javascript">
							function toggleNextSibling (e) {
							if (e.nextSibling.style.display=='none') {
							e.nextSibling.style.display='block';
							} else { e.nextSibling.style.display='none'; }
							}</script>
</head>
<body>
<span style="display: none;">v3.25.2</span><table class="report" border="0" cellspacing="2" id="id2">
<tr>
<th class="tl" colspan="1" rowspan="1"><div style="width: 200px;"><strong>Document and Entity Information<br></strong></div></th>
<th class="th"><div>Sep. 19, 2025</div></th>
</tr>
<tr class="re">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_CoverAbstract', window );"><strong>Cover [Abstract]</strong></a></td>
<td class="text">&#160;<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_EntityRegistrantName', window );">Entity Registrant Name</a></td>
<td class="text">ATI INC<span></span>
</td>
</tr>
<tr class="re">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_AmendmentFlag', window );">Amendment Flag</a></td>
<td class="text">false<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_EntityCentralIndexKey', window );">Entity Central Index Key</a></td>
<td class="text">0001018963<span></span>
</td>
</tr>
<tr class="re">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_DocumentType', window );">Document Type</a></td>
<td class="text">8-K<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_DocumentPeriodEndDate', window );">Document Period End Date</a></td>
<td class="text">Sep. 19,  2025<span></span>
</td>
</tr>
<tr class="re">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_EntityIncorporationStateCountryCode', window );">Entity Incorporation State Country Code</a></td>
<td class="text">DE<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_EntityFileNumber', window );">Entity File Number</a></td>
<td class="text">1-12001<span></span>
</td>
</tr>
<tr class="re">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_EntityTaxIdentificationNumber', window );">Entity Tax Identification Number</a></td>
<td class="text">25-1792394<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_EntityAddressAddressLine1', window );">Entity Address, Address Line One</a></td>
<td class="text">2021 McKinney Avenue<span></span>
</td>
</tr>
<tr class="re">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_EntityAddressCityOrTown', window );">Entity Address, City or Town</a></td>
<td class="text">Dallas<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_EntityAddressStateOrProvince', window );">Entity Address, State or Province</a></td>
<td class="text">TX<span></span>
</td>
</tr>
<tr class="re">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_EntityAddressPostalZipCode', window );">Entity Address, Postal Zip Code</a></td>
<td class="text">75201<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_CityAreaCode', window );">City Area Code</a></td>
<td class="text">(800)<span></span>
</td>
</tr>
<tr class="re">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_LocalPhoneNumber', window );">Local Phone Number</a></td>
<td class="text">289-7545<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_WrittenCommunications', window );">Written Communications</a></td>
<td class="text">false<span></span>
</td>
</tr>
<tr class="re">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_SolicitingMaterial', window );">Soliciting Material</a></td>
<td class="text">false<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_PreCommencementTenderOffer', window );">Pre Commencement Tender Offer</a></td>
<td class="text">false<span></span>
</td>
</tr>
<tr class="re">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_PreCommencementIssuerTenderOffer', window );">Pre Commencement Issuer Tender Offer</a></td>
<td class="text">false<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_Security12bTitle', window );">Security 12b Title</a></td>
<td class="text">Common Stock, par value $0.10 per share<span></span>
</td>
</tr>
<tr class="re">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_TradingSymbol', window );">Trading Symbol</a></td>
<td class="text">ATI<span></span>
</td>
</tr>
<tr class="ro">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_SecurityExchangeName', window );">Security Exchange Name</a></td>
<td class="text">NYSE<span></span>
</td>
</tr>
<tr class="re">
<td class="pl" style="border-bottom: 0px;" valign="top"><a class="a" href="javascript:void(0);" onclick="Show.showAR( this, 'defref_dei_EntityEmergingGrowthCompany', window );">Entity Emerging Growth Company</a></td>
<td class="text">false<span></span>
</td>
</tr>
</table>
<div style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_AmendmentFlag">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Boolean flag that is true when the XBRL content amends previously-filed or accepted submission.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_AmendmentFlag</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:booleanItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_CityAreaCode">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Area code of city</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_CityAreaCode</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:normalizedStringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_CoverAbstract">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Cover page.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_CoverAbstract</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:stringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_DocumentPeriodEndDate">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>For the EDGAR submission types of Form 8-K: the date of the report, the date of the earliest event reported; for the EDGAR submission types of Form N-1A: the filing date; for all other submission types: the end of the reporting or transition period. The format of the date is YYYY-MM-DD.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_DocumentPeriodEndDate</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:dateItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_DocumentType">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_DocumentType</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>dei:submissionTypeItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_EntityAddressAddressLine1">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Address Line 1 such as Attn, Building Name, Street Name</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_EntityAddressAddressLine1</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:normalizedStringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_EntityAddressCityOrTown">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Name of the City or Town</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_EntityAddressCityOrTown</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:normalizedStringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_EntityAddressPostalZipCode">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Code for the postal or zip code</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_EntityAddressPostalZipCode</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:normalizedStringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_EntityAddressStateOrProvince">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Name of the state or province.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_EntityAddressStateOrProvince</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>dei:stateOrProvinceItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_EntityCentralIndexKey">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/presentationRef<br> -Publisher SEC<br> -Name Exchange Act<br> -Number 240<br> -Section 12<br> -Subsection b-2<br></p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_EntityCentralIndexKey</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>dei:centralIndexKeyItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_EntityEmergingGrowthCompany">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Indicate if registrant meets the emerging growth company criteria.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/presentationRef<br> -Publisher SEC<br> -Name Exchange Act<br> -Number 240<br> -Section 12<br> -Subsection b-2<br></p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_EntityEmergingGrowthCompany</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:booleanItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_EntityFileNumber">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Commission file number. The field allows up to 17 characters. The prefix may contain 1-3 digits, the sequence number may contain 1-8 digits, the optional suffix may contain 1-4 characters, and the fields are separated with a hyphen.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_EntityFileNumber</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>dei:fileNumberItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_EntityIncorporationStateCountryCode">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Two-character EDGAR code representing the state or country of incorporation.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_EntityIncorporationStateCountryCode</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>dei:edgarStateCountryItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_EntityRegistrantName">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/presentationRef<br> -Publisher SEC<br> -Name Exchange Act<br> -Number 240<br> -Section 12<br> -Subsection b-2<br></p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_EntityRegistrantName</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:normalizedStringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_EntityTaxIdentificationNumber">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/presentationRef<br> -Publisher SEC<br> -Name Exchange Act<br> -Number 240<br> -Section 12<br> -Subsection b-2<br></p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_EntityTaxIdentificationNumber</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>dei:employerIdItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_LocalPhoneNumber">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Local phone number for entity.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_LocalPhoneNumber</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:normalizedStringItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_PreCommencementIssuerTenderOffer">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/presentationRef<br> -Publisher SEC<br> -Name Exchange Act<br> -Number 240<br> -Section 13e<br> -Subsection 4c<br></p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_PreCommencementIssuerTenderOffer</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:booleanItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_PreCommencementTenderOffer">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/presentationRef<br> -Publisher SEC<br> -Name Exchange Act<br> -Number 240<br> -Section 14d<br> -Subsection 2b<br></p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_PreCommencementTenderOffer</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:booleanItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_Security12bTitle">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Title of a 12(b) registered security.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/presentationRef<br> -Publisher SEC<br> -Name Exchange Act<br> -Number 240<br> -Section 12<br> -Subsection b<br></p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_Security12bTitle</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>dei:securityTitleItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_SecurityExchangeName">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Name of the Exchange on which a security is registered.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/presentationRef<br> -Publisher SEC<br> -Name Exchange Act<br> -Number 240<br> -Section 12<br> -Subsection d1-1<br></p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_SecurityExchangeName</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>dei:edgarExchangeCodeItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_SolicitingMaterial">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as soliciting material pursuant to Rule 14a-12 under the Exchange Act.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/presentationRef<br> -Publisher SEC<br> -Name Exchange Act<br> -Number 240<br> -Section 14a<br> -Subsection 12<br></p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_SolicitingMaterial</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:booleanItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_TradingSymbol">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Trading symbol of an instrument as listed on an exchange.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>No definition available.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_TradingSymbol</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>dei:tradingSymbolItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
<table border="0" cellpadding="0" cellspacing="0" class="authRefData" style="display: none;" id="defref_dei_WrittenCommunications">
<tr><td class="hide"><a style="color: white;" href="javascript:void(0);" onclick="Show.hideAR();">X</a></td></tr>
<tr><td><div class="body" style="padding: 2px;">
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">- Definition</a><div><p>Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as written communications pursuant to Rule 425 under the Securities Act.</p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ References</a><div style="display: none;"><p>Reference 1: http://www.xbrl.org/2003/role/presentationRef<br> -Publisher SEC<br> -Name Securities Act<br> -Number 230<br> -Section 425<br></p></div>
<a href="javascript:void(0);" onclick="Show.toggleNext( this );">+ Details</a><div style="display: none;"><table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><strong> Name:</strong></td>
<td style="white-space:nowrap;">dei_WrittenCommunications</td>
</tr>
<tr>
<td style="padding-right: 4px;white-space:nowrap;"><strong> Namespace Prefix:</strong></td>
<td>dei_</td>
</tr>
<tr>
<td><strong> Data Type:</strong></td>
<td>xbrli:booleanItemType</td>
</tr>
<tr>
<td><strong> Balance Type:</strong></td>
<td>na</td>
</tr>
<tr>
<td><strong> Period Type:</strong></td>
<td>duration</td>
</tr>
</table></div>
</div></td></tr>
</table>
</div>
</body>
</html>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>XML
<SEQUENCE>7
<FILENAME>Show.js
<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
// Edgar(tm) Renderer was created by staff of the U.S. Securities and Exchange Commission.  Data and content created by government employees within the scope of their employment are not subject to domestic copyright protection. 17 U.S.C. 105.
var Show={};Show.LastAR=null,Show.showAR=function(a,r,w){if(Show.LastAR)Show.hideAR();var e=a;while(e&&e.nodeName!='TABLE')e=e.nextSibling;if(!e||e.nodeName!='TABLE'){var ref=((window)?w.document:document).getElementById(r);if(ref){e=ref.cloneNode(!0);
e.removeAttribute('id');a.parentNode.appendChild(e)}}
if(e)e.style.display='block';Show.LastAR=e};Show.hideAR=function(){Show.LastAR.style.display='none'};Show.toggleNext=function(a){var e=a;while(e.nodeName!='DIV')e=e.nextSibling;if(!e.style){}else if(!e.style.display){}else{var d,p_;if(e.style.display=='none'){d='block';p='-'}else{d='none';p='+'}
e.style.display=d;if(a.textContent){a.textContent=p+a.textContent.substring(1)}else{a.innerText=p+a.innerText.substring(1)}}}
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>XML
<SEQUENCE>8
<FILENAME>report.css
<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
/* Updated 2009-11-04 */
/* v2.2.0.24 */

/* DefRef Styles */
.report table.authRefData{
	background-color: #def;
	border: 2px solid #2F4497;
	font-size: 1em;
	position: absolute;
}

.report table.authRefData a {
	display: block;
	font-weight: bold;
}

.report table.authRefData p {
	margin-top: 0px;
}

.report table.authRefData .hide {
	background-color: #2F4497;
	padding: 1px 3px 0px 0px;
	text-align: right;
}

.report table.authRefData .hide a:hover {
	background-color: #2F4497;
}

.report table.authRefData .body {
	height: 150px;
	overflow: auto;
	width: 400px;
}

.report table.authRefData table{
	font-size: 1em;
}

/* Report Styles */
.pl a, .pl a:visited {
	color: black;
	text-decoration: none;
}

/* table */
.report {
	background-color: white;
	border: 2px solid #acf;
	clear: both;
	color: black;
	font: normal 8pt Helvetica, Arial, san-serif;
	margin-bottom: 2em;
}

.report hr {
	border: 1px solid #acf;
}

/* Top labels */
.report th {
	background-color: #acf;
	color: black;
	font-weight: bold;
	text-align: center;
}

.report th.void	{
	background-color: transparent;
	color: #000000;
	font: bold 10pt Helvetica, Arial, san-serif;
	text-align: left;
}

.report .pl {
	text-align: left;
	vertical-align: top;
	white-space: normal;
	width: 200px;
	white-space: normal; /* word-wrap: break-word; */
}

.report td.pl a.a {
	cursor: pointer;
	display: block;
	width: 200px;
	overflow: hidden;
}

.report td.pl div.a {
	width: 200px;
}

.report td.pl a:hover {
	background-color: #ffc;
}

/* Header rows... */
.report tr.rh {
	background-color: #acf;
	color: black;
	font-weight: bold;
}

/* Calendars... */
.report .rc {
	background-color: #f0f0f0;
}

/* Even rows... */
.report .re, .report .reu {
	background-color: #def;
}

.report .reu td {
	border-bottom: 1px solid black;
}

/* Odd rows... */
.report .ro, .report .rou {
	background-color: white;
}

.report .rou td {
	border-bottom: 1px solid black;
}

.report .rou table td, .report .reu table td {
	border-bottom: 0px solid black;
}

/* styles for footnote marker */
.report .fn {
	white-space: nowrap;
}

/* styles for numeric types */
.report .num, .report .nump {
	text-align: right;
	white-space: nowrap;
}

.report .nump {
	padding-left: 2em;
}

.report .nump {
	padding: 0px 0.4em 0px 2em;
}

/* styles for text types */
.report .text {
	text-align: left;
	white-space: normal;
}

.report .text .big {
	margin-bottom: 1em;
	width: 17em;
}

.report .text .more {
	display: none;
}

.report .text .note {
	font-style: italic;
	font-weight: bold;
}

.report .text .small {
	width: 10em;
}

.report sup {
	font-style: italic;
}

.report .outerFootnotes {
	font-size: 1em;
}
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>XML
<SEQUENCE>10
<FILENAME>FilingSummary.xml
<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
<XML>
<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.25.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>1</ContextCount>
  <ElementCount>22</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>0</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>0</UnitCount>
  <MyReports>
    <Report instance="d911457d8k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>100000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>ati-20250919.xsd</File>
    <File>ati-20250919_lab.xml</File>
    <File>ati-20250919_pre.xml</File>
    <File doctype="8-K" isOnlyDei="true" original="d911457d8k.htm">d911457d8k.htm</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="22">http://xbrl.sec.gov/dei/2025</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>false</HasCalculationLinkbase>
</FilingSummary>
</XML>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>JSON
<SEQUENCE>13
<FILENAME>MetaLinks.json
<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
{
 "version": "2.2",
 "instance": {
  "d911457d8k.htm": {
   "nsprefix": "ati",
   "nsuri": "http://www.atimetals.com/20250919",
   "dts": {
    "schema": {
     "local": [
      "ati-20250919.xsd"
     ],
     "remote": [
      "http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd",
      "http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd",
      "http://www.xbrl.org/2003/xl-2003-12-31.xsd",
      "http://www.xbrl.org/2003/xlink-2003-12-31.xsd",
      "http://www.xbrl.org/2005/xbrldt-2005.xsd",
      "http://www.xbrl.org/dtr/type/nonNumeric-2009-12-16.xsd",
      "http://www.xbrl.org/dtr/type/numeric-2009-12-16.xsd",
      "https://www.xbrl.org/dtr/type/2024-01-31/types.xsd",
      "https://xbrl.sec.gov/dei/2025/dei-2025.xsd",
      "https://xbrl.sec.gov/naics/2025/naics-2025.xsd"
     ]
    },
    "labelLink": {
     "local": [
      "ati-20250919_lab.xml"
     ]
    },
    "presentationLink": {
     "local": [
      "ati-20250919_pre.xml"
     ]
    },
    "inline": {
     "local": [
      "d911457d8k.htm"
     ]
    }
   },
   "keyStandard": 22,
   "keyCustom": 0,
   "axisStandard": 0,
   "axisCustom": 0,
   "memberStandard": 0,
   "memberCustom": 0,
   "hidden": {
    "total": 3,
    "http://xbrl.sec.gov/dei/2025": 3
   },
   "contextCount": 1,
   "entityCount": 1,
   "segmentCount": 0,
   "elementCount": 23,
   "unitCount": 0,
   "baseTaxonomies": {
    "http://xbrl.sec.gov/dei/2025": 22
   },
   "report": {
    "R1": {
     "role": "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation",
     "longName": "100000 - Document - Document and Entity Information",
     "shortName": "Document and Entity Information",
     "isDefault": "true",
     "groupType": "document",
     "subGroupType": "",
     "menuCat": "Cover",
     "order": "1",
     "firstAnchor": {
      "contextRef": "duration_2025-09-19_to_2025-09-19",
      "name": "dei:DocumentType",
      "unitRef": null,
      "xsiNil": "false",
      "lang": "en-US",
      "decimals": null,
      "ancestors": [
       "span",
       "p",
       "div",
       "div",
       "body",
       "html"
      ],
      "reportCount": 1,
      "baseRef": "d911457d8k.htm",
      "first": true,
      "unique": true
     },
     "uniqueAnchor": {
      "contextRef": "duration_2025-09-19_to_2025-09-19",
      "name": "dei:DocumentType",
      "unitRef": null,
      "xsiNil": "false",
      "lang": "en-US",
      "decimals": null,
      "ancestors": [
       "span",
       "p",
       "div",
       "div",
       "body",
       "html"
      ],
      "reportCount": 1,
      "baseRef": "d911457d8k.htm",
      "first": true,
      "unique": true
     }
    }
   },
   "tag": {
    "dei_AmendmentFlag": {
     "xbrltype": "booleanItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "AmendmentFlag",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Amendment Flag",
        "terseLabel": "Amendment Flag",
        "documentation": "Boolean flag that is true when the XBRL content amends previously-filed or accepted submission."
       }
      }
     },
     "auth_ref": []
    },
    "dei_CityAreaCode": {
     "xbrltype": "normalizedStringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "CityAreaCode",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "City Area Code",
        "terseLabel": "City Area Code",
        "documentation": "Area code of city"
       }
      }
     },
     "auth_ref": []
    },
    "dei_CoverAbstract": {
     "xbrltype": "stringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "CoverAbstract",
     "lang": {
      "en-us": {
       "role": {
        "label": "Cover [Abstract]",
        "terseLabel": "Cover [Abstract]",
        "documentation": "Cover page."
       }
      }
     },
     "auth_ref": []
    },
    "dei_DocumentPeriodEndDate": {
     "xbrltype": "dateItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "DocumentPeriodEndDate",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Document Period End Date",
        "terseLabel": "Document Period End Date",
        "documentation": "For the EDGAR submission types of Form 8-K: the date of the report, the date of the earliest event reported; for the EDGAR submission types of Form N-1A: the filing date; for all other submission types: the end of the reporting or transition period. The format of the date is YYYY-MM-DD."
       }
      }
     },
     "auth_ref": []
    },
    "dei_DocumentType": {
     "xbrltype": "submissionTypeItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "DocumentType",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Document Type",
        "terseLabel": "Document Type",
        "documentation": "The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'."
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntityAddressAddressLine1": {
     "xbrltype": "normalizedStringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityAddressAddressLine1",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Entity Address, Address Line One",
        "terseLabel": "Entity Address, Address Line One",
        "documentation": "Address Line 1 such as Attn, Building Name, Street Name"
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntityAddressCityOrTown": {
     "xbrltype": "normalizedStringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityAddressCityOrTown",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Entity Address, City or Town",
        "terseLabel": "Entity Address, City or Town",
        "documentation": "Name of the City or Town"
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntityAddressPostalZipCode": {
     "xbrltype": "normalizedStringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityAddressPostalZipCode",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Entity Address, Postal Zip Code",
        "terseLabel": "Entity Address, Postal Zip Code",
        "documentation": "Code for the postal or zip code"
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntityAddressStateOrProvince": {
     "xbrltype": "stateOrProvinceItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityAddressStateOrProvince",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Entity Address, State or Province",
        "terseLabel": "Entity Address, State or Province",
        "documentation": "Name of the state or province."
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntityCentralIndexKey": {
     "xbrltype": "centralIndexKeyItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityCentralIndexKey",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Entity Central Index Key",
        "terseLabel": "Entity Central Index Key",
        "documentation": "A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK."
       }
      }
     },
     "auth_ref": [
      "r1"
     ]
    },
    "dei_EntityEmergingGrowthCompany": {
     "xbrltype": "booleanItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityEmergingGrowthCompany",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Entity Emerging Growth Company",
        "terseLabel": "Entity Emerging Growth Company",
        "documentation": "Indicate if registrant meets the emerging growth company criteria."
       }
      }
     },
     "auth_ref": [
      "r1"
     ]
    },
    "dei_EntityFileNumber": {
     "xbrltype": "fileNumberItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityFileNumber",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Entity File Number",
        "terseLabel": "Entity File Number",
        "documentation": "Commission file number. The field allows up to 17 characters. The prefix may contain 1-3 digits, the sequence number may contain 1-8 digits, the optional suffix may contain 1-4 characters, and the fields are separated with a hyphen."
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntityIncorporationStateCountryCode": {
     "xbrltype": "edgarStateCountryItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityIncorporationStateCountryCode",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Entity Incorporation State Country Code",
        "terseLabel": "Entity Incorporation State Country Code",
        "documentation": "Two-character EDGAR code representing the state or country of incorporation."
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntityRegistrantName": {
     "xbrltype": "normalizedStringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityRegistrantName",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Entity Registrant Name",
        "terseLabel": "Entity Registrant Name",
        "documentation": "The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC."
       }
      }
     },
     "auth_ref": [
      "r1"
     ]
    },
    "dei_EntityTaxIdentificationNumber": {
     "xbrltype": "employerIdItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "EntityTaxIdentificationNumber",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Entity Tax Identification Number",
        "terseLabel": "Entity Tax Identification Number",
        "documentation": "The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS."
       }
      }
     },
     "auth_ref": [
      "r1"
     ]
    },
    "dei_LocalPhoneNumber": {
     "xbrltype": "normalizedStringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "LocalPhoneNumber",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Local Phone Number",
        "terseLabel": "Local Phone Number",
        "documentation": "Local phone number for entity."
       }
      }
     },
     "auth_ref": []
    },
    "dei_PreCommencementIssuerTenderOffer": {
     "xbrltype": "booleanItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "PreCommencementIssuerTenderOffer",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Pre Commencement Issuer Tender Offer",
        "terseLabel": "Pre Commencement Issuer Tender Offer",
        "documentation": "Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act."
       }
      }
     },
     "auth_ref": [
      "r3"
     ]
    },
    "dei_PreCommencementTenderOffer": {
     "xbrltype": "booleanItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "PreCommencementTenderOffer",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Pre Commencement Tender Offer",
        "terseLabel": "Pre Commencement Tender Offer",
        "documentation": "Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act."
       }
      }
     },
     "auth_ref": [
      "r5"
     ]
    },
    "dei_Security12bTitle": {
     "xbrltype": "securityTitleItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "Security12bTitle",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Security 12b Title",
        "terseLabel": "Security 12b Title",
        "documentation": "Title of a 12(b) registered security."
       }
      }
     },
     "auth_ref": [
      "r0"
     ]
    },
    "dei_SecurityExchangeName": {
     "xbrltype": "edgarExchangeCodeItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "SecurityExchangeName",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Security Exchange Name",
        "terseLabel": "Security Exchange Name",
        "documentation": "Name of the Exchange on which a security is registered."
       }
      }
     },
     "auth_ref": [
      "r2"
     ]
    },
    "dei_SolicitingMaterial": {
     "xbrltype": "booleanItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "SolicitingMaterial",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Soliciting Material",
        "terseLabel": "Soliciting Material",
        "documentation": "Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as soliciting material pursuant to Rule 14a-12 under the Exchange Act."
       }
      }
     },
     "auth_ref": [
      "r4"
     ]
    },
    "dei_TradingSymbol": {
     "xbrltype": "tradingSymbolItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "TradingSymbol",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Trading Symbol",
        "terseLabel": "Trading Symbol",
        "documentation": "Trading symbol of an instrument as listed on an exchange."
       }
      }
     },
     "auth_ref": []
    },
    "dei_WrittenCommunications": {
     "xbrltype": "booleanItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2025",
     "localname": "WrittenCommunications",
     "presentation": [
      "http://www.atimetals.com//20250919/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "lang": {
      "en-us": {
       "role": {
        "label": "Written Communications",
        "terseLabel": "Written Communications",
        "documentation": "Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as written communications pursuant to Rule 425 under the Securities Act."
       }
      }
     },
     "auth_ref": [
      "r6"
     ]
    }
   }
  }
 },
 "std_ref": {
  "r0": {
   "role": "http://www.xbrl.org/2003/role/presentationRef",
   "Publisher": "SEC",
   "Name": "Exchange Act",
   "Number": "240",
   "Section": "12",
   "Subsection": "b"
  },
  "r1": {
   "role": "http://www.xbrl.org/2003/role/presentationRef",
   "Publisher": "SEC",
   "Name": "Exchange Act",
   "Number": "240",
   "Section": "12",
   "Subsection": "b-2"
  },
  "r2": {
   "role": "http://www.xbrl.org/2003/role/presentationRef",
   "Publisher": "SEC",
   "Name": "Exchange Act",
   "Number": "240",
   "Section": "12",
   "Subsection": "d1-1"
  },
  "r3": {
   "role": "http://www.xbrl.org/2003/role/presentationRef",
   "Publisher": "SEC",
   "Name": "Exchange Act",
   "Number": "240",
   "Section": "13e",
   "Subsection": "4c"
  },
  "r4": {
   "role": "http://www.xbrl.org/2003/role/presentationRef",
   "Publisher": "SEC",
   "Name": "Exchange Act",
   "Number": "240",
   "Section": "14a",
   "Subsection": "12"
  },
  "r5": {
   "role": "http://www.xbrl.org/2003/role/presentationRef",
   "Publisher": "SEC",
   "Name": "Exchange Act",
   "Number": "240",
   "Section": "14d",
   "Subsection": "2b"
  },
  "r6": {
   "role": "http://www.xbrl.org/2003/role/presentationRef",
   "Publisher": "SEC",
   "Name": "Securities Act",
   "Number": "230",
   "Section": "425"
  }
 }
}
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>ZIP
<SEQUENCE>14
<FILENAME>0001193125-25-217804-xbrl.zip
<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
begin 644 0001193125-25-217804-xbrl.zip
M4$L#!!0    ( %>'.5M/D9D&.0,  $L+   0    871I+3(P,C4P.3$Y+GAS
M9+U6WV_;-A!^+]#_X::G#9A$2T%26(A39$L#!$BSPDV'O16T=':(4:1&4DG\
MW_=(2;;LQ)Z3#,M+*-Y]=]_]I$\_/E82[M%8H=4D2I-1!*@*70JUF$2-C;DM
MA(@^GKU_=_I3',/%Y=4-Q'#G7&USQAX>'I)R+I35LG%DP2:%KAC$<:__^^TW
M^+.UGL,4)7*+D!VG&?S6"%GFV2@['GW(LB0=@@QR;PU*[C"',<M.F%>$-"-
MGI[ ^6?XQ*U#H^!65#C$ZGIIQ.+.P<_%+Q!0%UHIE!*7<"D45X7@$K[VA'^%
M*U4D<"XE3#W,$DN+YA[+I+/Z:,O<%G=8\??O "A=RN:*3#;5)/)YZ-+P.#,R
MT6;!2F>86];(2"DF+32BB ;0?\<]P5 =O,2N@'-N9P'42T)^!@C*WX87^J[0
M<=D6*&1]G(X'@!+7@$#)8I$L]#TCP;9Q+Q?/!Y&-1D>,^L%1GG$ D4+]O0?A
MQ3-JC:&3)Y"'HP!(Q^,Q"](M2J7;C*"S?LQ:8=#FSADQ:QQ>:E-=X)PWDE"-
M^J?A4LP%ED&+^K1"Y39T-C4<-PMT-[Q"6_,"7Y9KZJCG B.N*?OK\_77T&S1
MF0< A/X35:V-@[8-KW41QF-//OU7W)<A]E=QFL5':4+&(E#/TMY10V!O)M)7
M]U5$5JUQ,!&[JX7](?:'7=Z?;_Q79V![HGW\8Q]_>G)0_$\VPG_ 1*N;MY(9
MK+77UT1Q4;1;JST>7I<U\DV]V:\%GX?]CK?W2.<U^.1*:1<<#9GPNA9JKKLK
MNO1-G/>=/,4YA/V5<U,8+7'_EF.UT34:)VC+KX>A-7!G<#Z)R'_<KYGODL\2
M6C.]QA/[F]/EQ8P@**_7['JL$\Z#K[T8O)Q>2RY7IGTW3")+:9>#Z?Q_HZT-
MOC1:@EA:[J%HNX/^,M!Z<>S>SRUI@#]\FU[M>1Y6[P-S_%$K72U;EA>Z:/P;
MU/\_5^4G1=R65]18I@J\(A#TD$Q)_?M!ZBN6/<\2Z;>;"-V;COP?_;3K+0R/
M7)70FH.!O5.V;63;?F.Q_$.=A7/!9='(5=8[<*>Q#[A=K\.1:V:[<=UM7[%^
MBMGV&'<WPW%OK]IU0Y\_ %!+ P04    " !7ASE;G0N$=U\&  "]0P  %
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MV1E-^C:+1-;LE0;#*R8YAJ<B/-%/S)OR^"BY8S#M5K BB )5BR ULVD)T#7
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M1?(N&O,1 7EY<U-_XU"ET!'&-4SAOD@7K/>I$N&MRT"Q#J2%(*GD#'K;)HK
M/]$)*?KG2JV8=!\ B\[S&(-R@_9AV(DG'(D2[;8&(RW7ZGRTY*AR2AK9<MS>
ML&"E]U.;X6@VY7%4^Q[';EY76YLR VB_[K2ML6I1;6HR<=#JD,B[[VE:Z7=K
M1].@:3=0I](W'[>]WBQF6'L+_BBI(T3MK:/EH@N<%B$B,C-E2*6=J6RAT2*2
M=;NE63=/U\&M=LN:?!K1GMOQ^FDU@N4Q%.OHKA[U6II7H/DT8GM]6]?4FLU3
MO+YWNF!RKJ?FH\3[^%9O1I:^:/@AL!*)3E_AJ[:%>T/=7^.KD"5B/7MA+"\$
M:27(2A&]QM>B#<N+?'6]%$]<Z"/S=R>R4SS]ZPOZS']02P,$%     @ 5X<Y
M6RB!Y..R!   ?"H  !0   !A=&DM,C R-3 Y,3E?<')E+GAM;-6:78_B-A2&
M[U?:_^"F-ZW4$ ([LP4-LZ+,3(4Z7P*VK7JS,LD!K#HVLLT _[[' 5<$PA2F
MVRKF@@_'[_'K\SB.8W+U:95Q\@)*,RDZ05RK!P1$(E,FIIU@H4.J$\8"H@T5
M*>520"=8@PX^7;]_=_5-&)*;N_XC"<G,F+EN1]%RN:RE$R:TY N#(74MD5E$
MPM#5[XT^DU\WS;7) #A0#:1Q$3?(3PO&TW:CWKBH?VPT:O&N2 &UT4A*#;1)
M*VI<1K8BB1LH:,>7I/M ;JDVH 09L0QVM7*^5FPZ,^2[Y'N2JVZD$, YK,D=
M$U0DC'(R=(9_('V1U$B7<S*P,HTN-:@72&O;J)R)/]OV;6R]D_?O"+XPC4+G
MI9W )F.;B]58\9I44[1;;T9.%.QJ5@>B93.7Q*U6*\J/%NMK5E8;&XBCWQ_N
MA\D,,AHB D26[#6%;E+SMWK7W$6T.>CJ:];6>:1[F>2Y/Z%;Y&@-^RMTU4);
M%,:-L!G75CH-KFV3FZPJR6$ $V(_/P_ZA3;110:&\LV0ROG76W$K,G0EA<S6
MD15%-S)99"",^^R*]%889M9],9$JR[L2D#RK[9F"22? HM %LWZ^'6"<+^?$
M,>LYGA::97,. 8EV^C-7.':$R6O?8T%! "L#(H74A;'^_ZL>7V^P;L>N3 H9
M<"=OSDQ#4IO*ER@%EK=HO^3YR7.#/[[T),X7W;$VBB:FF -N!XM4KI#3,?!.
M4"**OJ:A37<',&4VO#"/-(-3?95KB_9V*7954HA,5>*BXM<#A,738%LCFE.%
M\<)DAC.>4T^4S$I3M6U-ON97JA14)\!I$V>!@,P5DPJK84E %AHMR;DU3[D]
M!A-0"M+[31*.FLV=XHRJ(:_YE9EU<:BF=KC><3H]%=:>J+J4]HPZ/$UO\&R&
M60][H"COXRRU^@76YYU3!^+JXCIBV&'[X TV=PT881I/I5745!=2T:=C<^D=
MFV= KWB)3F]P,7LNI#UQ]6GM&7;8/GJ#S:VE$JGF4N6Y'6**H2<7.%VL>S(]
M<ZWQ#Z&JB_0D^P[PCYX!OF,<'A?9&-1Y-'=U54>WZ]5Q:GG&:417_133P"9L
M<U_Z%FA'@U2=X%'C6YS-NF<XNVF*2=;;#[Q%AO@\E*4!JHZQU+1#&/N)L(=?
MG]1(+L6; .[*/<&W:]G!\^<&O-"5_#K^I)Z5?&%VT_ M! ]B>(+QP+=CZ=O=
M^K8_SU(;RO]@\_.7IN41/.&XY]I1].?FW<XG707T'&Y%375)%7TZ-A?>L+'_
M@O#GF11GWB0<ZJK+Z-"KX^3/)LMOZ,^ Z,DL6XCM&EF?"NN(N+K$CAAVV/S9
M9!E*SA)FF)@^X,58,6OM-&9ERNH"*W/K:/FS8_*LP XYP-52OB%K_\543Y/)
MZ=/B:Q&J2^\UUXZB/_LI>[WI:[T ]>]9EL3QAFB)]RW7#_YLK PA65B+<6,\
M8H:?O)0\U%67VZ%7Q\F?W9.1HO8IJ^$Z&\N3+W=[HNH2VC/J\/BS/^*&V.TJ
MF5$QA7,>*BG75A=6N5_'S+=]D-L,U!3'WL]*+LT,Y_<Y%6<^NW D1'4)OFK;
M@?P?MD*NHH/4W&.!?6QR<\2^V8< L>0O4$L#!!0    ( %>'.5LHZ80/D!(
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M_DR4/W'9EXS#U="E$^1]EJF12SZN8F\FP]_<<9AG?D.7.\/XA#M?,K_IIK]
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M4P!6"BP):5,W0=7TU-,A<8=X&0HQ2D\;EGID-,$4MIE\YK:N#G'P&=OO07^
M)?.%S.K7FC3IG?T&S C"K) ZT(ETJ/<D@Z%O3W*2#038865HB;L;"@#=7'4"
M\U/C:I+5%$O &A,M6CA!?D6^!A.LL#OD4^P!O ) 7X ^O:NY*$R.VQ2'V1@M
MX6O798M1N$_,Q>1);>VAD10:!_$U15@KYF*51MB-<6I@W_,QMLG <'ULS@*[
M]TP@HMTI72TUAW_U5*'C/TN9+$E $K]5<P@&N\\NYOXT"YB74V1AXS#<FBRX
M^EQ%&8) 7(\1OXY'<#,,A+@KQ8#@E6THT?KO0TPHHZ/WS-Q)"N:'>-I;,VV:
M1 ]W=?(5."1+[C37 %M<*26 /_!)[^'*&8"N1^\VU/<O"32OP^PJ=3K$.B_0
MO/*)^9%@ XIT?1<PKJ9C;$<6N/JE?9B-/^+3D2F%LR\TE?;KP1MTB/;4P2KR
M3@ ^OMG@"'2V?LN]0%-%@6RF>Q)4Z1[\V1.XU0Y5'!8!-O IUS5U/*7J$0 Q
ME3.=#L,HA "J@"[;0@,=X94*=(YM*E_(3X:7\^31_ !L3P@X8Q /Z<FY!UH&
M#2+KP((>%GLC/^J5"["&7BL]I\'E#"?B;@ C($)@YJ)8B8UM!NIFUASBUK$:
ML@<DZH'U?GLVN1H8>RP"7\=<2,;IP=I&^@ULNP32<.T4@$K"V\8<Y!#&X]0)
MA 4C".MRKA!/.!JZ#HC4(6C4&[MIEP ?P9?TT)&+HD08HGL#I]!00K4'TC%U
MG3?,T166+08D ;%%+8!L&&>:(HO8OK]ID1;,%"L]#%;IZ@2(@/A+7R0195C"
M6%>8_3D4L$SBV<-9HSY=@K7M>CCN(+363GAYAF9"?2.;UB$J"KC#O<7\.Y7G
ML#R>$3M0P YHQ[H,I0R5O@[%X;=D0R '=#>%C4:8J,2XGF-?Y)R!-_U4;5K<
MBO,\,\"[;T;I2STTV [KTL %K99DD)"9(U=-:WFPL/]"LPM"$&D%&\PYNJE9
MXO(!#Z>6AF#J'01 ;^B%AQW=49(UA<ICCF5>0-B?SHMI 8:AKJ &JZ@HN >;
M\ UQ1L"9"^0JPI$A:(PQ5(!)-UJ+Q]NCI#[5WW'R$/CP(;38H6_!@;.[6$@-
MJ%$ .HA;G*O!+J!BL[-6/9O2X>& !-JT:P?(RB;S0@XPI) P'7H1^F,0@VU=
M92!UGW 84<8/T5H?_,>4]S(7\JR647,R VT3LQ.CZR/;@]8BY.YN +8J;L\F
M) \S7<Q31H@,3_-!!\(4HQWQ/&J,'>8P>8(ZYUN6_'SD*9)YBE*^>/P#YRGJ
M@+?HZP1*KDT$<Q/+Q7WB\P6,19,OC*Y9:<YHF$.][W9S7ZF+M_2:%^T^8W[R
M*IQM<R#;8 :T--JK7BQ)&'E%R>EE^G$O"1E4V0Y7MBL4J@+%?%0A8-)!12#O
M$<R.&>4)D6==VW0_NBI+?Z,2W2-@C'M\$:O)H^A1>A[DW@]=\5:ZH@)4R__
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M_Y1/[;]02P$"% ,4    " !7ASE;3Y&9!CD#  !+"P  $
M@ $     871I+3(P,C4P.3$Y+GAS9%!+ 0(4 Q0    ( %>'.5N="X1W7P8
M +U#   4              "  6<#  !A=&DM,C R-3 Y,3E?;&%B+GAM;%!+
M 0(4 Q0    ( %>'.5LH@>3CL@0  'PJ   4              "  ?@)  !A
M=&DM,C R-3 Y,3E?<')E+GAM;%!+ 0(4 Q0    ( %>'.5LHZ80/D!(  "IK
M   .              "  =P.  !D.3$Q-#4W9#AK+FAT;5!+!08     !  $
+ /X   "8(0     !

end
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>XML
<SEQUENCE>15
<FILENAME>d911457d8k_htm.xml
<DESCRIPTION>IDEA: XBRL DOCUMENT
<TEXT>
<XML>
<?xml version="1.0" encoding="utf-8"?>
<xbrl
  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2025"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="ati-20250919.xsd" xlink:type="simple"/>
    <context id="duration_2025-09-19_to_2025-09-19">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001018963</identifier>
        </entity>
        <period>
            <startDate>2025-09-19</startDate>
            <endDate>2025-09-19</endDate>
        </period>
    </context>
    <dei:EntityRegistrantName
      contextRef="duration_2025-09-19_to_2025-09-19"
      id="Hidden_dei_EntityRegistrantName">ATI INC</dei:EntityRegistrantName>
    <dei:AmendmentFlag contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-247">false</dei:AmendmentFlag>
    <dei:EntityCentralIndexKey
      contextRef="duration_2025-09-19_to_2025-09-19"
      id="Hidden_dei_EntityCentralIndexKey">0001018963</dei:EntityCentralIndexKey>
    <dei:DocumentType contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-258">8-K</dei:DocumentType>
    <dei:DocumentPeriodEndDate contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-259">2025-09-19</dei:DocumentPeriodEndDate>
    <dei:EntityIncorporationStateCountryCode contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-260">DE</dei:EntityIncorporationStateCountryCode>
    <dei:EntityFileNumber contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-261">1-12001</dei:EntityFileNumber>
    <dei:EntityTaxIdentificationNumber contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-262">25-1792394</dei:EntityTaxIdentificationNumber>
    <dei:EntityAddressAddressLine1 contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-263">2021 McKinney Avenue</dei:EntityAddressAddressLine1>
    <dei:EntityAddressCityOrTown contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-264">Dallas</dei:EntityAddressCityOrTown>
    <dei:EntityAddressStateOrProvince contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-265">TX</dei:EntityAddressStateOrProvince>
    <dei:EntityAddressPostalZipCode contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-266">75201</dei:EntityAddressPostalZipCode>
    <dei:CityAreaCode contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-267">(800)</dei:CityAreaCode>
    <dei:LocalPhoneNumber contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-268">289-7545</dei:LocalPhoneNumber>
    <dei:WrittenCommunications contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-269">false</dei:WrittenCommunications>
    <dei:SolicitingMaterial contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-270">false</dei:SolicitingMaterial>
    <dei:PreCommencementTenderOffer contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-271">false</dei:PreCommencementTenderOffer>
    <dei:PreCommencementIssuerTenderOffer contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-272">false</dei:PreCommencementIssuerTenderOffer>
    <dei:Security12bTitle contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-273">Common Stock, par value $0.10 per share</dei:Security12bTitle>
    <dei:TradingSymbol contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-274">ATI</dei:TradingSymbol>
    <dei:SecurityExchangeName contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-275">NYSE</dei:SecurityExchangeName>
    <dei:EntityEmergingGrowthCompany contextRef="duration_2025-09-19_to_2025-09-19" id="ixv-276">false</dei:EntityEmergingGrowthCompany>
</xbrl>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
