The origin of unique nanoindentation response of nanocrystalline CoCrFeMnNi high entropy alloy under deformation: role of dislocation evolution

BR Zhang and AX Li and KW Kang and JS Zhang and MK Xu and D Huang and SK Liu and YT Jiang and G Li, PHYSICA B-CONDENSED MATTER, 710, 417238 (2025).

DOI: 10.1016/j.physb.2025.417238

We used molecular dynamics simulations to investigate the nanoindentation response mechanisms of nanocrystalline CoCrFeMnNi high entropy alloys, focusing on the role of boundaries and dislocation evolution under external forces. We simulate the actual working environment of deformation in high entropy alloys through stretch processing. The deformed nanocrystalline samples exhibit distinct periodic fluctuations, which are different from those observed in single crystal high entropy alloys. After stretch processing, preformed dislocation nucleation sites lead to a faster dislocation nucleation response, resulting in rapid dislocation accumulation. Twin boundaries alter the direction of dislocation emission and aiding the dislocation emission process. A unique response mechanism is observed during nanoindentation, where two competing mechanisms-rapid dislocation nucleation and accumulation, and dislocation emission mediated by twin boundaries are identified. Meanwhile, the surface strength under extreme conditions does not decrease with increasing strain. It enhances the understanding of the mechanical properties of nanocrystalline high entropy alloys under deformation.

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