Order-Disorder Competitive Cooperation in Equiatomic 3d-Transition-Metal Quaternary Alloys: Phase Stability and Electronic Structure

TL;DR

This study uses high-throughput first-principles calculations to analyze phase stability and electronic structure in equiatomic quaternary high-entropy alloys, highlighting the roles of valence electron concentration, temperature, and magnetic configurations.

Contribution

It provides new insights into the factors influencing phase stability in HEAs, emphasizing the importance of VEC, temperature, and magnetic ordering in determining stable structures.

Findings

Ordered phases are more stable than random solid solutions at finite temperatures.

High VEC D0$_{22}$ phases can be more stable than L1$_2$ phases.

Magnetic configurations with antiferromagnetic and ferromagnetic atoms contribute to phase stability.

Abstract

We use high-throughput first-principles sampling to investigate competitive factors that determine the crystal structure of high-entropy alloys (HEAs) and the energetics dependence of the stable phase on the atomic configuration of fully ordered L1$_2$, D0$_{22}$, and random solid solution (RSS) phases of equiatomic quaternary alloys comprising four of the six constituent elements (Cr, Mn, Fe, Co, Ni, and Cu). Considering the configurational entropy, we demonstrate that valence electron concentration (VEC) and temperature are crucial to determine the phase stability of HEAs at finite temperatures, wherein the ordered phases are energetically more favorable than RSS phases. Some D0$_{22}$ phases with high VEC are energetically more stable than L1$_2$ phases, though both phases are metastable. Further, we explore magnetic configurations to identify the origin of the enthalpy term. The calculations reveal that ordered phases comprising antiferromagnetic atoms surrounded by ferromagnetic atoms are energetically stable. The quantitative structure--property relationship is also discussed.