Atomic-level defect formation mechanism in high-entropy alloys

With the aid of atomistic simulations, we found that in solid solution alloys the soft spots detected by the the spatial distributions of low frequency vibration modes served as precursors of atomic level rearrangement. In high-entropy alloys, the successive defect growth has a chain-like manner which relied on the coupling of local shear transformations and vortex like atomic motion. This mechanism resembles the reported nucleation mechanism of shear transformation zone in metallic glasses, which is different from the dislocation slip induced planer fault growth in dilute solution alloy. In addition to the distinct defect formation mechanism, the extremely short correlation length of mechanical heterogeneity in high-entropy alloys also suppressed the synchronized motions of the dislocation line. This effect impeded the long-ranged dislocation slip and contributed to strong strain hardening ability. Our study reveals the critical defect formation mechanism at the atomic level and provides the theoretical description of various signature mechanical properties of high-entropy alloys.