Atomistic simulations of dislocation behaviors in Cr-Mn-Fe-Co-Ni high-entropy alloys with different Cr/Ni ratio

Abstract

Pronounced compositional fluctuations in CrMnFeCoNi high-entropy alloys (HEAs) lead to variations of the stacking-fault energy (SFE), which dominates the dislocation behavior and mechanical properties. However, studies on the underlying dislocation behaviors and deformation mechanisms as a function of composition (Cr/Ni ratio) within CrMnFeCoNi HEAs are largely lacking, which hinders further understanding of the composition-structure-property relationships for the rational design of HEAs. Atomistic simulations were employed in this study to investigate the core structures and dynamic behaviors of a/2<110> edge dislocations in non-equiatomic CrMnFeCoNi HEA, as well as its plasticity mechanisms. The results show that the core structure of a/2<110> edge dislocations is planar after energy minimization, but with significant variations in the separation distance between two partial dislocations along the dislocation line owing to the complex local composition. The effects of the Cr/Ni ratio on the dislocation-solute interactions during dislocation gliding were calculated and discussed. Additionally, snapshots of dislocation motion under shear stress were analyzed. The observations indicate that the strengthening of the non-equiatomic CrMnFeCoNi HEA with increasing Cr concentration is not contributed by the expected solute/dislocation interactions, but the observed events of edge extended dislocation climbing through jog nucleation. The unusual but reasonable dislocation climbing phenomenon and the resultant strengthening observed in this study open extraordinary opportunities for obtaining outstanding mechanical properties in non-equiatomic CrMnFeCoNi HEAs by tailoring the compositional variations.