First-principles study on the decohesion of grain boundary by hydrogen trapping in Aluminum and other metals

Yamaguchi, Masatake   ; Ebihara, Kenichi   ; Itakura, Mitsuhiro  ; Kadoyoshi, Tomoko*; Suzudo, Tomoaki   ; Kaburaki, Hideo

Generally speaking, the reduction of surface energy by hydrogen trapping is not considered as a key factor in the mechanism of hydrogen embrittlement of metals. This is because it is not known how much hydrogen atoms can be trapped at grain boundaries of metals and how much the cohesive energy (work of fracture) of the grain boundary can be reduced by the hydrogen trapping. From first-principles, we calculated the cohesive energy of bcc Fe 3(111) and fcc Al(Cu) 5(012) symmetrical tilt grain boundaries with varying the trapping density of hydrogen. We found that the cohesive energy of Fe, Al and Cu grain boundaries can be significantly reduced by the hydrogen trapping; it indicates that the reduction of surface energy can cause the hydrogen embrittlement in all Fe, Al, and Cu grain boundaries.