The Effects of various segregated solutes on the embrittlement of bcc Fe grain boundaries by the first-principles calculation

bcc鉄の粒界脆化における種々の偏析原子の効果に関する第一原理計算

山口 正剛   ; 西山 裕孝 ; 志賀 基之   ; 蕪木 英雄; 松澤 寛*

Yamaguchi, Masatake; Nishiyama, Yutaka; Shiga, Motoyuki; Kaburaki, Hideo; Matsuzawa, Hiroshi*

原子炉圧力容器材料に含まれる種々の溶質原子(C, Si, P, S, Mn, Cr, Cu, Mo等)の偏析によるbcc鉄粒界の脆化の機構を調べるため、第一原理計算を行った。計算では、bcc鉄の3(111)対称傾角粒界を用いて、種々の溶質原子に対する脆化機構,脆化の割合を求めた。また、この結果から種々の溶質原子の脆化機構に与える相対的な強さ及び粒界への偏析エネルギーを評価した。

First-principles method is applied to assess the embrittlement mechanism of bcc iron (Fe) grain boundaries due to the segregation of various solutes (C, Si, P, S, Mn, Cr, Cu, Mo, etc.) that are contained, for example, in the nuclear reactor pressure vessel steel. The simulation is performed for the bcc Fe 3(111) symmetrical tilt grain boundary to evaluate the effects of solute segregation on the strength of the interface separation, in particular, focusing on the mechanism and degree of embrittlement. We discuss the relative effects of these solutes on the embrittlement mechanism and segregation energy.