Slip-band-driven dynamic recrystallization mediated strain hardening in HfNbTaTiZr refractory high entropy alloy

Abstract

Refractory high-entropy alloys (RHEAs) exhibit outstanding strength at room temperature, but their high-temperature applications are hindered by severe strain-softening. Here, we report slip-band-driven dynamic recrystallization to enhance the high-temperature strain hardening of HfNbTaTiZr RHEA. By introducing partial lattice defects through hot forging, we increase the nucleation sites for dynamic recrystallization during subsequent thermomechanical deformation, thus suppressing the strain-softening behavior. We reveal that the high-temperature deformation is governed by the formation of heterogeneous bimodal grains along slip bands, which effectively constrain dislocation motion and improve strength, while microbands prevent premature failure. The fracture mode also changes from ductile to mixed to cleavage-dominated with increasing temperature. Our results demonstrate a simple and effective method for overcoming high-temperature strain-softening for BCC high entropy alloys.