Design Strength-Ductility Synergy of Metastable High-Entropy Alloys by Tailoring Unstable Fault Energies

TL;DR

This paper introduces a novel design strategy for metastable high-entropy alloys using unstable fault energies, which more accurately predicts deformation mechanisms and enhances strength-ductility synergy compared to traditional methods.

Contribution

The study proposes unstable fault energies as a new design metric for metastable HEAs, validated by discovering seven new alloys with improved TRIP/TWIP properties.

Findings

Unstable fault energies outperform ISFE in predicting deformation mechanisms.

Seven new metastable HEAs with TRIP/TWIP were experimentally validated.

UMFE/UTFE criterion accurately predicts deformation in all studied cases.

Abstract

Metastable alloys with transformation/twinning-induced plasticity (TRIP/TWIP) can overcome the strength-ductility trade-off in structural materials. Originated from the development of traditional alloys, the intrinsic stacking fault energy (ISFE) has been relied to tailor TRIP/TWIP in high-entropy alloys (HEA), but with limited quantitative success. Herein, we demonstrate a new strategy for designing metastable HEAs and validate its effectiveness by discovering seven new alloys with experimentally observed metastability for TRIP/TWIP. We propose unstable fault energies as the more effective design metric and attribute the deformation mechanism of metastable face-centered cubic alloys to UMFE (unstable martensite fault energy)/UTFE (unstable twin fault energy) rather than ISFE. Among the studied HEAs and steels, the traditional ISFE criterion fails in more than half of the cases, while the UMFE/UTFE criterion accurately predicts the deformation mechanisms in all cases. The UMFE/UTFE criterion provides a new paradigm for developing metastable alloys with TRIP/TWIP for enhanced strength-ductility synergy.