Ti-Zr-V-Nb-Al BCC high-entropy alloy with outstanding uniform ductility achieved by grain refinement

The lack of sufficient uniform deformation ability of body-centered cubic (BCC) high-entropy alloys (HEAs) is the obstacle to their applications as structural materials. Here we present a grain refinement strategy to achieve excellent uniform ductility of a BCC non-equal atomic ratio Ti-Zr-V-Nb-Al (TZ) alloy. The uniform elongation and yield strength of the fine-grained TZ alloy with a grain size of 15 µm are as high as ~12% and 840 MPa, respectively. The outstanding uniform deformability of the fine-grained TZ alloys is due to the frequent cross-slip events and abundant dislocation tangles. Grain refinement can increase the probability of dislocation entanglement, thereby promoting a rise in the work-hardening rate. The good plasticity and high work-hardening rate can improve the uniform deformation ability. Our results will give new insights into enhancing uniform ductility while maintaining high strength in the BCC HEAs.