The shear softening and dislocation glide competition due to the shear-induced short-range order degeneration in CoCrNi medium-entropy alloy

Abstract

The short-range order (SRO) in multi-principal element alloys (MPEAs) is an intriguing topic in advanced alloy research. The crucial question related to this topic lies in the effect of the local chemical fluctuations on the deformation behavior of MPEAs. In this study, the large-scale molecular dynamics (MD) simulation is used to investigate the dislocation glide behavior and mechanical performance of CoCrNi medium-entropy alloy (MEA) with respect to the SRO and lattice distortion (LD) effects. The slip plane softening and dislocation glide competition are found in the models with SRO. The change of energy barrier caused by SRO degeneration is the dominant reason for the slip plane softening, while the combination of dislocation pinning and slip plane softening leads to the dislocation glide competition, which is the primary mechanism for the shear localization in the CoCrNi MEA with SRO. Moreover, the dislocation glide competition compensates for the strength loss induced by slip plane softening. The results provide a new proposition for the conflicting simulation and experimental results on the topic of the SRO effect in MPEAs.