著者

小林 直弘 小山 元道 小林 憲司 北條 智彦 秋山 英二

出版者

公益社団法人 日本金属学会

雑誌

日本金属学会誌 (ISSN:00214876)

巻号頁・発行日

vol.85, no.2, pp.49-58, 2021-02-01 (Released:2021-01-25)

参考文献数

35

被引用文献数

6 5

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The grain size effects on the hydrogen embrittlement susceptibility of pure Ni and Ni-20Cr alloy were investigated. The hydrogen embrittlement susceptibility was evaluated by tensile testing under electrochemical hydrogen charging. Relative elongation, defined as the elongation under hydrogen charging divided by elongation in air, increased with increasing grain size in pure Ni (the grain size was in the range of 11-22 µm). In contrast, the relative elongation of Ni-20Cr alloy increased with decreasing grain size from 13 to 1.8 µm. Correspondingly, intergranular fracture was suppressed by grain coarsening in pure Ni and grain refinement in the Ni-20Cr alloy. In addition, the intergranular fracture surface in pure Ni showed curved slip lines, and in the Ni-20Cr alloy showed straight line marks. These fractographic features imply that the mechanisms of the hydrogen-assisted intergranular crack growth were different in pure Ni and Ni-20Cr alloy and this can be attributed to the difference in stacking fault energy.

著者

小山 元道 澤口 孝宏 津﨑 兼彰

出版者

一般社団法人 日本鉄鋼協会

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.104, no.4, pp.187-200, 2018 (Released:2018-03-31)

参考文献数

86

被引用文献数

6

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This paper presents an overview of the recent works on dynamic strain aging (DSA) of Fe-Mn-C austenitic steels including Hadfield and twinning-induced plasticity (TWIP) steels. First, a model of the DSA mechanism and its controlling factors are briefly explained in terms of Mn-C coupling and dislocation separation. Then, we introduce the effects of DSA on mechanical properties such as work hardening capability, uniform elongation, post-uniform elongation, and fatigue strength. Specifically, we note the pinning effect on extended dislocation for the work hardening, the Poretvin-Le Chatelier banding effect on damage evolution for the elongation, and the crack tip hardening/softening effect on crack resistance for the fatigue strength. We believe that this overview will help in designing advanced high-strength steels with superior ductility and fatigue resistance.

著者

小山 元道 秋山 英二 津﨑 兼彰

出版者

一般社団法人 日本鉄鋼協会

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.100, no.9, pp.1132-1139, 2014 (Released:2014-08-31)

参考文献数

36

被引用文献数

4

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Al effects on strain aging and resistance against hydrogen embrittlement were examined in Fe-18Mn-0.6C-based twinning-induced plasticity steels deformed at different strain rates. The Fe-18Mn-0.6C steel showed hydrogen-induced fracture when it had been pre-deformed at a strain rate of 1.7×10–6 s–1. The hydrogen-induced fracture was suppressed by increasing strain rate and increasing Al content. From the viewpoint of material strengthening by strain aging, we found two important factors improving the resistance to the hydrogen embrittlement; (1) suppression of dynamic strain aging by increasing strain rate and Al content, and (2) suppression of static strain aging under loading by the Al addition.