The Hierarchical Potential Energy Landscape of Screw Dislocation Motion in Refractory High-entropy Alloys

TL;DR

This paper constructs a hierarchical potential energy landscape for screw dislocation motion in refractory high-entropy alloys, revealing how local ordering influences dislocation dynamics and mechanical properties.

Contribution

It introduces a detailed hierarchical energy landscape model for dislocation motion in HEAs and explores how chemical short-range order modifies this landscape and deformation mechanisms.

Findings

Hierarchical, multilevel energy landscape with nested basins in HEAs.

Chemical short-range order smooths the energy landscape and shifts deformation mechanisms.

Disorder-roughened landscape causes barrier-hopping processes similar to metallic glasses.

Abstract

High-entropy alloys (HEAs) with concentrated solid solutions are conceived to possess a rugged atomic and energy landscape in which dislocation motion necessarily proceeds to accommodate mechanical deformation. Fundamental questions remain as to how rough the energy landscape is and to what extent it can be influenced by the local ordering of their constituent elements. Here, we construct and report the potential energy landscape (PEL) governing screw dislocation motion in refractory HEAs that reveals a hierarchical and multilevel structure with a collection of small basins nested in large metabasin. This striking feature pertaining to HEAs exerts a trapping force and back stress on saddle point activations, retarding dislocation movement. By introducing chemical short-range order, the energy landscape is smoothed but skewed to different degrees that shifts the rate-liming process from kink-glide to kink-pair nucleation. The chemical disorder-roughened PEL in HEAs, analogous to structural disorder induced in metallic glasses, signifies the role of various barrier-hopping processes underlying the extraordinary mechanical behaviors of the two distinct groups of materials.