About this Abstract |
| Meeting |
2026 TMS Annual Meeting & Exhibition
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| Symposium
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Steels in Extreme Conditions
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| Presentation Title |
Influence of Prior Austenite Grain Boundary Misorientation on Hydrogen-Induced Crack Propagation in a Medium Carbon Martensitic Steel |
| Author(s) |
Ji Hoon Kim, Goro Miyamoto, Akinobu Shibata, Tomohiko Hojo, Motomichi Koyama, Yongjie Zhang, Tadashi Furuhara |
| On-Site Speaker (Planned) |
Ji Hoon Kim |
| Abstract Scope |
This study examines how the misorientation of prior austenite grains () influences hydrogen-induced intergranular cracking along prior austenite grain boundaries (PAGBs) in a tempered martensitic medium-carbon steel (SCM435). Electron backscatter diffraction (EBSD) combined with prior austenite orientation reconstruction was used to compare the misorientation of martensite () and austenite () between fractured PAGBs and all observed boundaries. The results reveal that segments with low martensite misorientation ( < 10°) at PAGBs effectively suppress intergranular cracking. Such low-misorientation segments preferentially develop when the prior austenite grain misorientation is either below 10° (L-PAGB) or above 45° (H-PAGB), depending on specific transformation conditions.
To clarify the formation conditions of low-misorientation martensite along H-PAGBs, an interrupted quenching experiment was conducted to capture the early stage of martensitic transformation. The observations indicate that martensite variants tend to form with the Kurdjumov–Sachs (KS) orientation relationship not only to their parent austenite grain but also to the adjacent grain across the boundary. This so-called “double KS OR” condition is frequently achieved during the early stages of transformation, emphasizing the critical role of variant selection in mitigating hydrogen-induced intergranular fracture in tempered martensitic steels. |
| Proceedings Inclusion? |
Planned: |