Short-range order in the CoCrFeMnNi high-entropy alloy from cluster expansion

TL;DR

This study examines the short-range order and phase stability of the CoCrFeMnNi high-entropy alloy, revealing dominant Cr-Cr repulsive interactions and multiple temperature-dependent ordering instabilities.

Contribution

It introduces a cluster expansion approach combined with eigen-decomposition analysis to elucidate the alloy's ordering behavior and phase stability.

Findings

Cr-Cr repulsive interactions dominate ordering behavior

Identification of two lower-temperature instabilities: collective ordering and Fe-rich clustering

Emergence of ordered local environments influences phase transitions

Abstract

We investigate the short-range order (SRO) and phase stability of the equiatomic CoCrFeMnNi high-entropy alloy using cluster expansion supplemented by an eigen-decomposition analysis of the SRO parameters. Our results reveal that the primary ordering behavior is determined by strong Cr-Cr repulsive interactions, complemented by attractive heteroatomic Cr-$X$ pairs in the first nearest-neighbor shell. This chemical affinity is consistent with the emergence of ordered local environments and appears to be a major contributor to the primary order-disorder transition. At lower temperatures, the spectral SRO analysis suggests two additional lower-temperature instabilities: a collective ordering instability and an Fe-rich local clustering instability.