A new design concept for prevention of hydrogen-induced mechanical degradation: viewpoints of metastability and high entropy
© 2018 The Authors. "How crack growth is prevented" is key to improve both fatigue and monotonic fracture resistances under an influence of hydrogen. Specifically, the key points for the crack growth resistance are hydrogen diffusivity and local ductility. For instance, type 304 austenitic...
| Main Authors: | , , , , |
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| Other Authors: | |
| Format: | Article |
| Language: | English |
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Elsevier BV
2021
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| Online Access: | https://hdl.handle.net/1721.1/135053 |
| _version_ | 1811093924584882176 |
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| author | Koyama, Motomichi Eguchi, Takeshi Ichii, Kenshiro Tasan, Cemal Cem Tsuzaki, Kaneaki |
| author2 | Massachusetts Institute of Technology. Department of Materials Science and Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Materials Science and Engineering Koyama, Motomichi Eguchi, Takeshi Ichii, Kenshiro Tasan, Cemal Cem Tsuzaki, Kaneaki |
| author_sort | Koyama, Motomichi |
| collection | MIT |
| description | © 2018 The Authors. "How crack growth is prevented" is key to improve both fatigue and monotonic fracture resistances under an influence of hydrogen. Specifically, the key points for the crack growth resistance are hydrogen diffusivity and local ductility. For instance, type 304 austenitic steels show high hydrogen embrittlement susceptibility because of the high hydrogen diffusivity of bcc (α) martensite. In contrast, metastability in specific austenitic steels enables fcc (γ) to hcp (ϵ) martensitic transformation, which decreases hydrogen diffusivity and increases strength simultaneously. As a result, even if hydrogen-assisted cracking occurs during monotonic tensile deformation, the ϵ-martensite acts to arrest micro-damage evolution when the amount of ϵ-martensite is limited. Thus, the formation of ϵ-martensite can decrease hydrogen embrittlement susceptibility in austenitic steels. However, a considerable amount of ϵ-martensite is required when we attempt to have drastic improvements of work hardening capability and strength level with respect to transformation-induced plasticity effect. Since the hcp structure contains a less number of slip systems than fcc and bcc, the less stress accommodation capacity often causes brittle-like failure when the ϵ-martensite fraction is large. Therefore, ductility of ϵ-martensite is another key when we maximize the positive effect of ϵ-martensitic transformation. In fact, ϵ-martensite in a high entropy alloy was recently found to be extraordinary ductile. Consequently, the metastable high entropy alloys showed low fatigue crack growth rates in a hydrogen atmosphere compared with conventional metastable austenitic steels with α-martensitic transformation. We here present effects of metastability to ϵ-phase and configurational entropy on hydrogen-induced mechanical degradation including monotonic tension properties and fatigue crack growth resistance. |
| first_indexed | 2024-09-23T15:52:52Z |
| format | Article |
| id | mit-1721.1/135053 |
| institution | Massachusetts Institute of Technology |
| language | English |
| last_indexed | 2024-09-23T15:52:52Z |
| publishDate | 2021 |
| publisher | Elsevier BV |
| record_format | dspace |
| spelling | mit-1721.1/1350532023-02-22T20:11:27Z A new design concept for prevention of hydrogen-induced mechanical degradation: viewpoints of metastability and high entropy Koyama, Motomichi Eguchi, Takeshi Ichii, Kenshiro Tasan, Cemal Cem Tsuzaki, Kaneaki Massachusetts Institute of Technology. Department of Materials Science and Engineering © 2018 The Authors. "How crack growth is prevented" is key to improve both fatigue and monotonic fracture resistances under an influence of hydrogen. Specifically, the key points for the crack growth resistance are hydrogen diffusivity and local ductility. For instance, type 304 austenitic steels show high hydrogen embrittlement susceptibility because of the high hydrogen diffusivity of bcc (α) martensite. In contrast, metastability in specific austenitic steels enables fcc (γ) to hcp (ϵ) martensitic transformation, which decreases hydrogen diffusivity and increases strength simultaneously. As a result, even if hydrogen-assisted cracking occurs during monotonic tensile deformation, the ϵ-martensite acts to arrest micro-damage evolution when the amount of ϵ-martensite is limited. Thus, the formation of ϵ-martensite can decrease hydrogen embrittlement susceptibility in austenitic steels. However, a considerable amount of ϵ-martensite is required when we attempt to have drastic improvements of work hardening capability and strength level with respect to transformation-induced plasticity effect. Since the hcp structure contains a less number of slip systems than fcc and bcc, the less stress accommodation capacity often causes brittle-like failure when the ϵ-martensite fraction is large. Therefore, ductility of ϵ-martensite is another key when we maximize the positive effect of ϵ-martensitic transformation. In fact, ϵ-martensite in a high entropy alloy was recently found to be extraordinary ductile. Consequently, the metastable high entropy alloys showed low fatigue crack growth rates in a hydrogen atmosphere compared with conventional metastable austenitic steels with α-martensitic transformation. We here present effects of metastability to ϵ-phase and configurational entropy on hydrogen-induced mechanical degradation including monotonic tension properties and fatigue crack growth resistance. 2021-10-27T20:10:31Z 2021-10-27T20:10:31Z 2018 2019-09-24T15:04:55Z Article http://purl.org/eprint/type/JournalArticle https://hdl.handle.net/1721.1/135053 en 10.1016/J.PROSTR.2018.12.049 Procedia Structural Integrity Creative Commons Attribution-NonCommercial-NoDerivs License http://creativecommons.org/licenses/by-nc-nd/4.0/ application/pdf Elsevier BV Elsevier |
| spellingShingle | Koyama, Motomichi Eguchi, Takeshi Ichii, Kenshiro Tasan, Cemal Cem Tsuzaki, Kaneaki A new design concept for prevention of hydrogen-induced mechanical degradation: viewpoints of metastability and high entropy |
| title | A new design concept for prevention of hydrogen-induced mechanical degradation: viewpoints of metastability and high entropy |
| title_full | A new design concept for prevention of hydrogen-induced mechanical degradation: viewpoints of metastability and high entropy |
| title_fullStr | A new design concept for prevention of hydrogen-induced mechanical degradation: viewpoints of metastability and high entropy |
| title_full_unstemmed | A new design concept for prevention of hydrogen-induced mechanical degradation: viewpoints of metastability and high entropy |
| title_short | A new design concept for prevention of hydrogen-induced mechanical degradation: viewpoints of metastability and high entropy |
| title_sort | new design concept for prevention of hydrogen induced mechanical degradation viewpoints of metastability and high entropy |
| url | https://hdl.handle.net/1721.1/135053 |
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