The origin of jerky dislocation motion in high-entropy alloys

TL;DR

This paper investigates the origin of jerky dislocation motion in high-entropy alloys, revealing that local fluctuations in Peierls friction cause pinning and affect dislocation mobility, with insights from experiments and simulations.

Contribution

It uncovers the microscopic origin of dislocation pinning in HEAs, linking local Peierls friction fluctuations to dislocation dynamics, which was previously debated.

Findings

Jerky dislocation motion observed experimentally in HEAs.

Local Peierls friction fluctuations cause pinning points.

Dislocation mobility correlates with high local Peierls friction density.

Abstract

Dislocations in single-phase concentrated random alloys, including high- entropy alloys (HEAs), repeatedly encounter pinning during glide, resulting in jerky dislocation motion. While solute-dislocation interaction is well understood in conventional alloys, the origin of individual pinning points in concentrated random alloys is a matter of debate. In this work, we investigate the origin of dislocation pinning in the CoCrFeMnNi HEA. In- situ transmission electron microscopy studies reveal wavy dislocation lines and a jagged glide motion under external loading, even though no segregation or clustering is found around Shockley partial dislocations. Atomistic simulations reproduce the jerky dislocation motion and link the repeated pinning to local fluctuations in the Peierls friction. We demonstrate that the density of high local Peierls friction is proportional to the critical stress required for dislocation glide and the dislocation mobility.