Pseudoelastic Deformation in Refractory (MoW) 85 Zr 7.5(TaTi) 7.5 High-Entropy Alloy

Abstract

Phase diagrams supported by density functional theory methods can be crucial for designing high-entropy alloys (HEAs). We present phase and property analysis of refractory quinary (MoW)_xZr_y(TaTi)_1-x-y HEAs from combined Calculation of Phase Diagram (CALPHAD) and density-functional theory results, supplemented by molecular dynamics (MD) simulations. Our analysis indicates a Mo-W-rich region of this quinary system has a stable single-phase body-centered-cubic (bcc). The (MoW)₈₅Zr_7.5(TaTi)_7.5 was down-selected based on temperature-dependent CALPHAD phase diagram analysis and MD predicted elastic behavior that reveals twinning-assisted pseudoelastic behavior in this refractory HEA. While mostly unexplored in bcc crystals, twinning is a fundamental deformation mechanism that competes against dislocation slip in crystalline solids. This alloy shows identical cyclic deformation characteristics during uniaxial <100> loading, i.e., the pseudoelasticity is isotropic in loading direction. Additionally, a temperature increase from 77 to 1,500 K enhances the elastic strain recovery in load-unload cycles, offering possibly control to tune the pseudoelastic behavior.