Twin boundary migration and reactions with stacking fault tetrahedron in Cu and CoCrCuFeNi high-entropy alloy

Abstract

FCC high-entropy alloys (HEAs) have great application potential because of their excellent mechanical properties, in which twin boundary (TB) and stacking fault tetrahedron (SFT) are two kinds of primary defects. In this work, the mechanical responses of a twinned CoCrCuFeNi HEA and twinned Cu counterpart under shear deformation were investigated using molecular dynamics simulations to explore the interactions between TB and SFT and their effects on the mechanical properties of the materials. It was found that the primary carrier of plastic deformation in both twinned CoCrCuFeNi HEA and Cu are shear coupled TB migrations assisted by the glide of partial dislocations. Increasing the size of SFT leads to lower mechanical performances. Moreover, the mechanical properties of the CoCrCuFeNi HEA, including shear modulus and critical shear stress for TB migration, were found to be dependent insignificantly on temperature (100 K–700 K). After the interaction between TB and SFT, a flip-over SFT or SFT-like structure in CoCrCuFeNi HEA, and a rhombic SFT or double-sided SF in Cu are finally formed.