Serrated plastic flow in slowly-deforming complex concentrated alloys: universal signatures of dislocation avalanches

TL;DR

This study uses atomistic simulations to analyze dislocation avalanches in complex concentrated alloys, revealing universal, scale-free signatures of collective dislocation dynamics during slow deformation.

Contribution

It provides the first microstructural and topological characterization of dislocation avalanches in HEAs/MEAs, highlighting universal critical scaling behaviors.

Findings

Stress serrations correlate with slip patterns in alloys.

Dislocation avalanches exhibit scale-free, critical scaling features.

Universal signatures of dislocation avalanches are identified.

Abstract

Under plastic flow, multi-element high/medium-entropy alloys (HEAs/MEAs) commonly exhibit complex intermittent and collective dislocation dynamics owing to inherent lattice distortion and atomic-level chemical complexities. Using atomistic simulations, we report on an avalanche study of slowly-driven model face-centered cubic (fcc) NiCoCrFeMn and NiCoCr chemically complex alloys aiming for microstructural/topological characterization of associated dislocation avalanches. The results of our avalanche simulations reveal a close correspondence between the observed serration features in the stress response of the deforming HEA/MEA and the incurred slip patterns within the bulk crystal. We show that such correlations become quite pronounced within the rate-independent (quasi-static) regime exhibiting scale-free statistics and critical scaling features as universal signatures of dislocation avalanches.