2020 Fiscal Year Annual Research Report
Determination of the dominant defects of hydrogen embrittlement in iron-based materials through the development of in-situ measurement methods of atomic vacancies
| Project/Area Number |
18K13980
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| Research Institution | Chiba University |
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Principal Investigator |
Chiari Luca 千葉大学, 大学院工学研究院, 助教 (20794572)
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| Project Period (FY) |
2018-04-01 – 2021-03-31
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| Keywords | hydrogen embrittlement / defect / vacancy / hydrogen / iron / stainless steel / positron annihilation |
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| Outline of Annual Research Achievements |
In the final year, the surface-processing effect on the behavior of hydrogen-induced defects in pure iron was investigated to elucidated its role in the hydrogen embrittlement. The formation of large vacancy clusters in the bulk highlighted the increased interaction between hydrogen and coarse surfaces. The defect dynamics in hydrogen-charged pure iron by room temperature aging was studied using a high-flux positron beam but no time change was observed. The dominant defects of the hydrogen embrittlement in austenitic stainless steel SUS316 were detected and identified. The formation of high-density vacancies in local strain fields induced by hydrogen was found to be the factor leading to the embrittlement.
In this project, the dominant defects of hydrogen embrittlement in pure iron and austenitic stainless steels were detected and identified. Through the development of novel approaches for the detection of hydrogen-induced vacancies, i.e. freezing the state of defects and positron lifetime measurements in-situ and using a positron beam, the presence of previously undetected vacancies was revealed and their nature identified. Their role in driving the embrittlement process was clarified. These results contribute to the elucidation of the mechanism of hydrogen embrittlement, which has not been elucidated academically for many decades and is also industrially important in terms of developing steel materials for the era of a hydrogen-based society.
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