Special whole-process mobility responses of edge dislocation in CoCrNi with short-range ordering

The plastic response of metals is directly associated with the dislocation evolution in them. In multi-principal element alloys (MPEAs), the properties of dislocation can differ markedly from those in conventional metals. In this study, the influences of multi-principal element (MPE) composition and short-range ordering (SRO) on the relation between applied shear stress and the slip velocity of edge dislocation in MPEA CoCrNi are investigated by using the hybrid molecular dynamics and Monte Carlo simulations. In addition, the effects of MPE and SRO on dislocation core configurations, defect energies, and Peierls forces are also studied systematically. The results show that the whole-process relation between applied shear stress and dislocation slip velocity (i.e., the velocity-stress relation or mobility law) includes subsonic, first transonic, and second transonic regimes. The subsonic regime can be further divided into the linear and nonlinear relativistic effect stage. With increasing the degree of SRO, the velocity-stress relation for edge dislocations in CoCrNi changes remarkably in all three regimes. Coupled with the MPE effect, temperature can also influence such dislocation velocity-stress relation significantly. In addition, SRO can increase the stacking fault energy (SFE) of CoCrNi and thus reduce the static equilibrium dislocation width significantly. Furthermore, the Gaussian distribution of Peierls force in CoCrNi becomes narrower with increasing the degree of SRO. Overall, by changing the SFE, dislocation core structure, and Peierls force, SRO affects the whole-process dislocation velocity-stress relation of CoCrNi remarkably. These results facilitate the development of a comprehensive dislocation mobility law for MPEAs.