Ta-Nb-Mo-W refractory high-entropy alloys: anomalous ordering behavior and its intriguing electronic origin

TL;DR

This study uses electronic-structure calculations to uncover complex chemical ordering behaviors in Ta-Nb-Mo-W refractory high-entropy alloys, linking electronic features to ordering tendencies and phase segregation.

Contribution

It introduces a thermodynamic linear-response approach to explain the anomalous ordering and electronic origins in refractory high-entropy alloys, revealing the role of Fermi-surface features.

Findings

Identified long-range chemical interactions causing competing short-range order.

Linked electronic structure features near the Fermi surface to ordering behavior.

Demonstrated crossover from complex SRO to spinodal segregation.

Abstract

From electronic-structure-based thermodynamic linear-response, we establish chemical ordering behavior in complex solid solutions versus how Gibbs' space is traversed -- applying it on prototype refractory A2 Ta-Nb-Mo-W high-entropy alloys. Near ideal stoichiometry, this alloy has anomalous, intricate chemical ordering tendencies, with long-ranged chemical interactions that produce competing short-range order (SRO) with a crossover to spinodal segregation. This atypical SRO arises from canonical band behavior that, with alloying, create features near the Fermi-surface (well-defined even with disorder) that change to simple commensurate SRO with (un)filling of these states. Our results reveal how complexity and competing electronic effects control ordering in these alloys.