An Atomistic modeling of He bubble stability at grain boundaries in alpha-Fe

Suzudo, Tomoaki   ; Tsuru, Tomohito   ; Yamaguchi, Masatake   ; Kaburaki, Hideo

He bubbles at grain boundaries (GBs) may lead materials to serious embrittlement, but the mechanism of the nucleation of such bubbles is not well-understood. In the present paper, we analyzed the stability of various He-vacancy clusters, which are precursors of He bubbles, at several kinds of grain boundaries of alpha-Fe using a set of empirical potentials. We found that the dissociation energy of vacancy from He-vacancy clusters at GBs is generally less than that for the intragranular counterparts, and that the He-to-vacancy ratio in equilibrium for various GB cases becomes larger in comparison with the intragranular case. The results obtained here are useful for kinetic models of He bubble nucleation.