Dislocation Dynamics Analysis of CrCoNi using Micropillar Compression and Molecular Dynamics Simulation

High- and medium-entropy alloys have garnered significant interest in recent years due to their exceptional mechanical properties. In this study, we investigate the deformation mechanisms of CrCoNi single crystals through micropillar compression experiments, focusing on dislocation nucleation and propagation and their influence on strength and ductility. Additionally, molecular dynamics simulations were employed to elucidate the sources and spatial distribution of dislocations within the pillars.

Our results reveal that the alloy’s low stacking fault energy and high shear modulus result in a narrow dissociation width of Shockley partials. These partial dislocations form at very low strains (~0.05%), and as deformation progresses, dislocation forests develop, contributing to strain hardening. The observed jagged dislocation patterns indicate a non-uniform Peierls barrier, suggesting heterogeneous slip behavior. Notably, no deformation twinning was observed in our experiments; instead, plasticity was accommodated solely by slip band formation.

These findings provide new insights into the fundamental deformation mechanisms of CrCoNi medium-entropy alloys, shedding light on their exceptional mechanical properties and guiding the development of next-generation structural materials.