Dynamic interactions between low-angle grain boundary and stacking fault tetrahedron in Ni-Fe solid solution alloys

Abstract

A stacking fault tetrahedron (SFT) is a very common kind of defects in face-centered cubic (FCC) metals under irradiation environment. The migrating GB can heal the SFT through dislocation reactions. To explore the healing mechanisms and conditions required, the low-angle GB interactions with an SFT in pure Ni and Ni-Fe bicrystals were investigated using molecular dynamics (MD) simulations. Ni-Fe bicrystals have higher healing efficiency on SFT than pure Ni due to their more diverse dislocation reactions. The addition of Fe atom can reduce the stacking fault energy (SFE), so that most of stair-rod dislocations (SRDs) of SFT in Ni-Fe bicrystals can be transformed into Shockley partial dislocations (SPDs) through the energetically unfavorable reactions. As a result, the vacancies of SFT are redistributed and some of them are carried away by migrating GBs. In pure Ni, however, only a small part of SRDs can undergo the energetically unfavorable reactions, and the SPDs generated would spontaneously be transformed back to SRDs after the GB-SFT interaction. The healing efficiency on SFT can be gradually enhanced with the increasing Fe atom concentration and elevated temperature. • Dislocation reactions of low-angle GB and SFT in Ni-Fe are more diverse than in Ni. • Stair-rod dislocations of SFT can be converted into Shockley partial dislocations. • The vacancies of SFT are redistributed and carried away by migrating GB in Ni-Fe. • The SFT absorbed by low-angle GB is regenerated after GB-SFT interaction in Ni. • The healing efficiency on SFT can be enhanced with increasing Fe atom concentration.