Abstract: Refractory high-entropy alloys (RHEAs) are potential materials for high-temperature structural applications due to their excellent high-temperature performance. However, the early onset of plastic instability in RHEAs is a critical issue to be addressed. In this study, a novel Zr₃₅Ti₃₀Nb₂₀Al₁₀V₅ RHEA was subjected to 95% cold rolling and annealing, achieving outstanding mechanical properties. Notably, the cold-rolled alloy exhibited the highest reported tensile strength (∼2.0 GPa) among RHEAs with a moderate ductility of ∼8.5%. Moreover, Additionally, the subsequent annealing process enabled the alloy to achieve an outstanding combination of yield strength (1.1 GPa) and fracture elongation (20%). The cold-rolled alloy has a heterogeneous lamella structure with high-density dislocation cells and dislocation pile-ups, and lattice distortion in the locally chemically ordered structure. The high work hardening behavior originates from the heterogeneous deformation-induced (HDI) hardening, which makes the HDI stress and hardening rate increase with increasing strain. In the annealed alloy, lattice distortion increases significantly with increasing strain, promoting dislocation cross-slip. The dislocation pile-ups and interactions facilitate the transition of microbands, and the relatively stable work-hardening behavior of the alloy is mainly attributed to the microband-induced plasticity effect. This study provides novel insights into the design and optimization of highly formable RHEAs with excellent mechanical properties.

Key words: Refractory high-entropy alloy, Severe plastic deformation, Heterogeneous structure, Heterogeneous deformation-induced hardening, Microband-induced plasticity