A novel stress-induced martensitic transformation in a single-phase refractory high-entropy alloy

High-entropy alloys (HEAs) provide a new perspective to design metastable alloys with the stress-induced martensitic transformation (SIMT) for overcoming the strength-ductility trade-off. Here, we report a novel SIMT, orthorhombic to hexagonal close-packed martensite, in a single orthorhombic refractory HEA (Ti₁₆Zr₃₅Hf₃₅Ta₁₄ RHEA), showing a good yield strength-ductility matching. The analysis of the elastic distortion energy (∆E_els) of Ti₁₆Zr₃₅Hf₃₅Ta₁₄ and several other RHEAs reveals that severe lattice distortion is a key factor which causes this SIMT. Combined the “d-electron alloy design” approach with the ∆E_els, the phase configuration and SIMT path in RHEAs can be well predicted. Our work brings new insights between the lattice distortion and SIMT of RHEAs, benefiting the metastable alloy development.