Mechanistic Transition from Screw to Edge Dislocation Glide Enhances High-Temperature Strength in Refractory Complex Concentrated Alloys

TL;DR

This study reveals a transition from screw to edge dislocation glide in refractory alloys, driven by atomic size mismatch, which significantly enhances high-temperature strength, challenging traditional understanding of deformation mechanisms.

Contribution

It uncovers the mechanistic transition from screw to edge dislocation control in refractory alloys, linking atomic size effects to high-temperature strength improvements.

Findings

Edge dislocation control increases with V content.

Atomic misfit raises edge dislocation glide barriers.

Strength significantly improves at high temperatures.

Abstract

The strength of body-centered cubic materials is traditionally known to be governed by screw dislocations. However, recent findings reveal that in certain refractory complex concentrated alloys, edge dislocations can instead control strength. This work integrates high-temperature mechanical testing, in-situ neutron scattering during heating and tension, scanning transmission electron microscopy, and molecular dynamics simulations to uncover the mechanism behind this behavior. In the Nb-Ta-Ti-V system, increasing the V content, due to its smaller atomic size, induces substantial atomic misfit that raises the glide barrier for edge dislocations relative to screw dislocations. This effect drives a gradual transition from screw to edge dislocation-controlled deformation, leading to markedly enhanced strength at elevated temperatures.