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

Abstract Development of He bubbles at grain boundaries (GBs) may lead materials to serious embrittlement, but the nucleation mechanism 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 GBs of α-Fe using a set of empirical potentials. The results clearly indicated the preferred nucleation of He bubbles at GBs. We also found that the dissociation energy of vacancies 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 invaluable in establishing a kinetic model of He bubble nucleation at GBs.