A crystal plasticity-based reversible phase transformation model for Ti49Zr20Hf15Al10Nb6 high-entropy alloy

Abstract

The high-entropy alloys (HEAs) primarily composed of elements such as Ti, Zr, Hf, and Nb generally exhibit a B2-type crystal structure, contributing to their enhanced strength. However, the limited ability of the B2 lattice structure to accommodate plastic deformation leads to poor plasticity in this type of alloys. The deformation-induced martensitic transformation (DIMT) occurring in the B2 lattice can effectively alleviate the poor plasticity associated with these alloys. Our work focuses on the previously reported Ti49Zr20Hf15Al10Nb6 high-entropy alloy with DIMT mechanism, employing an improved elastic visco-plastic self-consistent (EVPSC) model to predict and analyze the macro- and micro-mechanical responses during uniaxial tension and cyclic loading that includes loading, unloading, and reloading. The model results elucidate the stress-strain behavior and volume fraction evolution of the β parent phase and ${\alpha }^{″}$${\alpha }^{″}$ martensite phase during tension and cyclic loading, while quantitatively assessing the contributions of transformation and dislocation mechanisms to plastic deformation. Additionally, it explores the influence of back stress—a topic that is rarely addressed—on the reverse process of martensitic transformation and recoverable strain in this high-entropy alloy at the microstructural level. This model serves as a theoretical analysis tool for HEAs that incorporate reversible phase transformation (RPT) mechanism, facilitating the understanding of the evolutionary processes governing mechanical behavior at the microstructural level and thereby guiding the enhancement of toughness in B2 lattice HEAs.