Entropy-induced transition on grain-boundary migration in multi-principal element alloys

In-depth understanding of grain boundaries (GBs) in multi-principal element alloys (MPEAs) is considered significant for designing MPEAs by GB engineering. This work explores the nanoscale GB structure and migration mechanism in MPEAs using atomic simulations. The GB-roughening transformation is observed as the mixing entropy increases, and the effect of entropy is confirmed by thermodynamic analysis. The entropy-induced transition of GB migration is proved: 1) the “concentrated shuffling mechanism” controls the migration of ordered GBs in low-entropy systems, leading to the obviously stepwise migration; 2) the “dispersed shuffling mechanism” dominates the migration of disordered GBs in high-entropy systems, resulting in the continuous migration manner. [Display omitted]