On the martensitic transformation in Fe$_{x}$Mn$_{80-x}$Co$_{10}$Cr$_{10}$ high-entropy alloy

TL;DR

This study uses computational and experimental methods to understand and predict the martensitic transformation in Fe-Mn-Co-Cr high-entropy alloys, linking phase stability to alloy composition and electronic structure.

Contribution

It provides a combined theoretical and experimental analysis of phase transformations in Fe-Mn-based HEAs, offering insights into controlling TRIP/TWIP effects through alloy design.

Findings

Martensitic transformation correlates with fcc-hcp energy difference.

Chemical short-range order influences phase stability.

Experimental validation confirms theoretical predictions.

Abstract

High-entropy alloys (HEAs), and even medium-entropy alloys (MEAs), are an intriguing class of materials in that structure and property relations can be controlled via alloying and chemical disorder over wide ranges in the composition space. Employing density-functional theory combined with the coherent-potential approximation to average over all chemical configurations, we tune free energies between face-centered-cubic (fcc) and hexagonal-close-packed (hcp) phases in Fe$_{x}$Mn$_{80-x}$Co$_{10}$Cr$_{10}$ systems.~Within Fe-Mn-based alloys, we show that the martensitic transformation and chemical short-range order directly correlate with the fcc-hcp energy difference and stacking-fault energies, which are in quantitative agreement with recent experiments on a $x$=40~at.\% polycrystalline HEA/MEA. Our predictions are further confirmed by single-crystal measurements on a$x$=40at.\% using transmission-electron microscopy, selective-area diffraction, and electron-backscattered-diffraction mapping. The results herein offer an understanding of transformation-induced/twinning-induced plasticity (TRIP/TWIP) in this class of HEAs and a design guide for controlling the physics behind the TRIP effect at the electronic level.