第一原理計算を用いたFe-Cr-Niオーステナイト合金中への水素固溶特性の検討; 平均および局所水素濃度に与えるCr・Ni原子の影響

The Characteristics of hydrogen solution in Fe-Cr-Ni austenitic alloys investigated by first-principles calculation; The Roles of Cr and Ni atoms on average and local hydrogen concentration

森山 潤一郎*; 高桑 脩*; 山口 正剛   ; 小川 祐平*; 津崎 兼彰*

Moriyama, Junichiro*; Takakuwa, Osamu*; Yamaguchi, Masatake; Ogawa, Yuhei*; Tsuzaki, Kaneaki*

Fe-Cr-Niを基本成分とする一部のオーステナイト系ステンレス鋼)では、固溶水素濃度の上昇に伴って水素が寸法効果では説明することが難しいほどの高い固溶強化能を発揮する。同現象の理解にはFe-Cr-Ni系における平均固溶水素濃度に加えて、局所水素濃度の把握が必要であり、平均固溶水素濃度はCr・Ni量に依存することから、これらの置換型原子と水素原子との相互作用が着目すべき重要因子であると考えられる。本研究では第一原理計算を用いて、Cr・Ni原子と水素原子との相互作用を定量化し、平均的な固溶水素濃度(占有率)とその分布への影響を評価した。

In some austenitic stainless steels (Fe-Cr-Ni basic composition), hydrogen exhibits a high solution strengthening capacity with increasing solid solution hydrogen concentration that is difficult to explain by dimensional effects. In order to understand this phenomenon, it is necessary to understand the local hydrogen concentration in addition to the average solid solution hydrogen concentration in the Fe-Cr-Ni system. Since the average solid solution hydrogen concentration depends on the amount of Cr and Ni, the interaction between these substitutional atoms and hydrogen atoms is considered to be an important factor to focus on. In this study, first-principles calculations were used to quantify the interaction between Cr and Ni atoms and hydrogen atoms, and to evaluate the average solid-solution hydrogen concentration (occupancy) and its effect on the distribution.