Strain-induced topological transition from planar to filamentous grain boundary oxidation in austenitic stainless steel

Strain-induced topological transition from planar to filamentous grain boundary oxidation in austenitic stainless steel | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Strain-induced topological transition from planar to filamentous grain boundary oxidation in austenitic stainless steel Semanti Mukhopadhyay, Tingkun Liu, Matthew Olszta, Hyoju Park, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8673645/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract In pressurized water (PWR) nuclear reactors, intergranular oxidation of structural materials in the primary‑coolant circuit is accelerated by plastic deformation along random high‑angle grain boundaries (RHAGBs), providing a precursor state for intergranular stress corrosion cracking (IGSCC). However, because IGSCC initiation is inherently stochastic, conventional macroscopic strain measures are ineffective for identifying which oxidized RHAGBs will eventually crack. This limitation motivates a focused search for mechanistic signatures that distinguish vulnerable boundaries from benign ones. Here, we evaluate RHAGB oxidation morphology as a potential mechanistic signature by comparing solution‑annealed (SA) and cold‑tensile‑strained (CTS) Fe–18Cr–14Ni exposed to simulated PWR primary‑water environments. Electron microscopy reveals a deformation-driven transition in RHAGB oxidation morphology, from continuous oxides in SA to complex 3D morphologies in CTS comprising Cr-enriched filaments advancing ahead of the oxidation front. We propose a “Leading Filament” mechanism to explain this transition, where short-circuit transport enables high-aspect-ratio, stress-concentrating filaments. While macroscopic strain controls oxidation depth, boundary-specific strain heterogeneity likely governs filament morphology, offering a mechanistic signature relevant to the boundary-to-boundary variability in IGSCC initiation. Physical sciences/Engineering Physical sciences/Materials science Intergranular Oxidation DIGM PWR Pipe Diffusion GND Austenitic Stainless Steel Grain Boundary Microstructural Characterization STEM Full Text Additional Declarations No competing interests reported. Supplementary Files SupplementaryInfo.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 08 Mar, 2026 Reviews received at journal 04 Mar, 2026 Reviews received at journal 27 Feb, 2026 Reviewers agreed at journal 07 Feb, 2026 Reviewers agreed at journal 04 Feb, 2026 Reviewers invited by journal 03 Feb, 2026 Editor assigned by journal 02 Feb, 2026 Submission checks completed at journal 02 Feb, 2026 First submitted to journal 22 Jan, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8673645","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":585932352,"identity":"3aeab378-35ea-4fd7-90a2-f281dbf2c97e","order_by":0,"name":"Semanti Mukhopadhyay","email":"","orcid":"","institution":"Pacific Northwest National Laboratory","correspondingAuthor":false,"prefix":"","firstName":"Semanti","middleName":"","lastName":"Mukhopadhyay","suffix":""},{"id":585932353,"identity":"894a9bdf-a5e1-4f64-b669-8063760da4f6","order_by":1,"name":"Tingkun Liu","email":"","orcid":"","institution":"Pacific Northwest National 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Degradation","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"NPJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Intergranular Oxidation, DIGM, PWR, Pipe Diffusion, GND, Austenitic Stainless Steel, Grain Boundary, Microstructural Characterization, STEM","lastPublishedDoi":"10.21203/rs.3.rs-8673645/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8673645/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn pressurized water (PWR) nuclear reactors, intergranular oxidation of structural materials in the primary‑coolant circuit is accelerated by plastic deformation along random high‑angle grain boundaries (RHAGBs), providing a precursor state for intergranular stress corrosion cracking (IGSCC). However, because IGSCC initiation is inherently stochastic, conventional macroscopic strain measures are ineffective for identifying which oxidized RHAGBs will eventually crack. This limitation motivates a focused search for mechanistic signatures that distinguish vulnerable boundaries from benign ones. Here, we evaluate RHAGB oxidation morphology as a potential mechanistic signature by comparing solution‑annealed (SA) and cold‑tensile‑strained (CTS) Fe\u0026ndash;18Cr\u0026ndash;14Ni exposed to simulated PWR primary‑water environments. Electron microscopy reveals a deformation-driven transition in RHAGB oxidation morphology, from continuous oxides in SA to complex 3D morphologies in CTS comprising Cr-enriched filaments advancing ahead of the oxidation front. We propose a \u0026ldquo;Leading Filament\u0026rdquo; mechanism to explain this transition, where short-circuit transport enables high-aspect-ratio, stress-concentrating filaments. 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