Ab initio modeling of the energy landscape for screw dislocations in body-centered cubic high-entropy alloys

TL;DR

This study uses ab initio methods to explore how chemical short-range order affects dislocation core properties in bcc high-entropy alloys, revealing impacts on their energy landscape and potential mechanical behavior.

Contribution

It provides the first detailed ab initio analysis of dislocation core energy distributions in bcc high-entropy alloys considering chemical short-range order effects.

Findings

Dislocation core energies are higher in RHEAs than in pure bcc metals.

Chemical short-range order narrows the distribution of core energies.

SRO influences the heterogeneity of dislocation energy landscapes.

Abstract

In traditional body-centered cubic (bcc) metals, the core properties of screw dislocations play a critical role in plastic deformation at low temperatures. Recently, much attention has been focused on refractory high-entropy alloys (RHEAs), which also possess bcc crystal structures. However, unlike face-centered cubic high-entropy alloys (HEAs), there have been far fewer investigations on bcc HEAs, specifically on the possible effects of chemical short-range order (SRO) in these multiple principal element alloys on dislocation mobility. Here, using density functional theory, we investigate the distribution of dislocation core properties in MoNbTaW RHEAs alloys, and how they are influenced by SRO. The average values of the core energies in the RHEA are found to be larger than those in the corresponding pure constituent bcc metals, and are relatively insensitive to the degree of SRO. However, the presence of SRO is shown to have a large effect on narrowing the distribution of dislocation core energies and decreasing the spatial heterogeneity of dislocation core energies in the RHEA. It is argued that the consequences for the mechanical behavior of HEAs is a change in the energy landscape of the dislocations which would likely heterogeneously inhibit their motion.