Dislocation reaction-based formation mechanism of stacking fault tetrahedra in FCC high-entropy alloy

In conventional FCC metals and alloys, the formation mechanisms of stacking fault tetrahedron (SFT) based on the vacancy cluster and Frank loop have been widely accepted; however, the dislocation reaction-based for-mation mechanism of SFT without Frank loop and vacancy cluster remains controversial. In this work, we studied the formation of the SFTs in CoCrFeNiCu high-entropy alloy (HEA) bicrystals and their single-crystal counterparts subjected to shear deformation using molecular dynamics (MD) simulations. The migration and thickening of grain boundaries, and the nucleation and glide of dislocations from the grain boundaries are the predominant carriers of deformation, which are the prerequisite for the formation of SFT. We observed two types of dislocation reaction-based formation mechanisms, where there is no vacancy aggregation and Frank loop participation. The formation of SFT originates from the growth of the bottom face of the pyramid in the bicrystal HEA, while in the single-crystal HEA, SFT nucleates at its vertex, and extends towards its bottom.

Automated summary

In this study, the formation mechanisms of stacking fault tetrahedron (SFT) in high-entropy alloys were investigated using molecular dynamics simulations. The migration and thickening of grain boundaries, as well as the nucleation and glide of dislocations from the grain boundaries, were found to be the main causes of deformation, leading to the formation of SFT. Two types of dislocation reaction-based mechanisms were observed, without the involvement of vacancy aggregation or Frank loops.