Modulating grain boundary-mediated plasticity of high-entropy alloys via chemo-mechanical coupling

Abstract

Intrinsic chemical disorder and the subsequent interfacial roughening have posed formidable challenges in elucidating the grain boundary (GB)-mediated plasticity in high-entropy alloys (HEAs). Here using a self-propelling atomistic algorithm to probe the complex energy landscape of the CoCrFeMnNi HEAs, in conjunction with location-specific perturbations across GBs exposed to different environments, we investigate atomic-reconfiguration ensembles near GBs and their sensitivities to various chemo-mechanical conditions. Two distinct modes, collective and random, are discovered, and their partitions are dictated by multiple factors, including the activation energy window, external mechanical loading, and local compositions. Remarkably, Fe disproportionately promotes the collective events and facilitates the slip activities near GBs, while Cr atoms suppress the emission of partial dislocations from GBs. These findings imply promising solutions – via synergistic combination of microalloying, heat treatment, and mechanical loading – to selectively trigger desired plasticity modes at needed deformation stage, and hence to achieve an enhanced tunability of HEAs’ mechanical behaviors.