First-principles prediction of high-entropy-alloy stability

TL;DR

This paper uses first-principles calculations to predict the phase stability of high-entropy alloys, demonstrating that configurational entropy stabilizes a single BCC phase at high temperatures, with complex intermetallics forming at lower temperatures.

Contribution

It introduces a computational approach to predict phase stability in high-entropy alloys, validated by experimental formation of a single BCC phase.

Findings

Configurational entropy stabilizes a single BCC phase from 1700K to melting.

Complex intermetallic phases are favored at lower temperatures.

Experimental confirmation of phase transformation at lower temperatures.

Abstract

High entropy alloys (HEAs) are multicomponent compounds whose high configurational entropy allows them to solidify into a single phase, with a simple crystal lattice structure. Some HEA's exhibit desirable properties, such as high specific strength, ductility, and corrosion resistance, while challenging the scientist to make confident predictions in the face of multiple competing phases. We demonstrate phase stability in the multicomponent alloy system of Cr-Mo-Nb-V, for which some of its binary subsystems are subject to phase separation and complex intermetallic-phase formation. Our first-principles calculation of free energy predicts that the configurational entropy stabilizes a single body-centered cubic (BCC) phase from T = 1,700K up to melting, while precipitation of a complex intermetallic is favored at lower temperatures. We form the compound experimentally and confirm that it forms as a single BCC phase from the melt, but that it transforms reversibly at lower temperatures.