Orientation-dependent transformation-induced plasticity in refractory high entropy alloys

Refractory high-entropy alloys (RHEAs) are promising candidates to replace Ni-based superalloys in high-temperature applications. Among them, the HfNbTaTiZr RHEA forms a BCC solid solution and demonstrates an excellent balance of strength and ductility under both tension and compression. Classical molecular dynamics simulations were used to uncover orientation-dependent transformation-induced plasticity in single crystal HfNbTaTiZr, where strain along and leads to the BCC || FCC and BCC || HCP transformations following the Bain and the Burgers pathways, respectively. Metastable BCC HfNb 0.2 Ta 0.2 TiZr transforms to HCP regardless of which axis uniaxial strain is applied. The HCP phase exhibits superior mechanical properties, thereby enhancing the effect of metastability engineering as a means of overcoming the strength ductility trade-off. Compression-twins occur in HfNb 0.2 Ta 0.2 TiZr strained along , while straining along or results in severe strain softening into a compressive state. These findings provide valuable guidance for optimizing composition and tailoring texture in RHEAs.