The effects of annealing on severely cold-rolled equiatomic HfNbTiZr high entropy alloy

In this study, the effects of annealing on mechanical properties and phase evolution of 80% cold-rolled equiatomic HfNbTiZr high entropy alloy (HEA) are studied. A single BCC-phase solid solution is identified in the as cold-rolled and the recrystallized state at above 700 degrees C, and its hardness increases as the annealing temperature increases. However, the HEA still follows the Hall-Petch equation according to tensile tests. When the HfNbTiZr HEA is annealed at 450 degrees C, hardness would increase, while the hardening effect on 550 degrees C annealed specimens is not so pronounced. The age hardening effect is mainly associated with the formation of HCP precipitates.