Microstructure Recrystallization and Mechanical Properties of a Cold-Rolled TiNbZrTaHf Refractory High-Entropy Alloy

The equiatomic TiNbZrTaHf alloy was successfully rolled at room temperature with the reduction of similar to 85%. The microstructure and tensile properties were investigated after cold working and annealing. It was determined that the recrystallization temperature of the TiNbZrTaHf alloy between 850 and 900 degrees C. Complete recrystallization and normal grain growth occurred, the high stability of single phase was maintained after annealing at 1000, 1200, and 1400 degrees C. But the precipitated phase appeared after long term annealing, as seen after 500 h at 1000 degrees C. After cold working, the tensile strength and the elongation of TiNbZrTaHf were 1137 MPa and 25.1%, respectively. The annealed alloy has a high tensile strength (sigma(b) = 863 MPa) and ductility (epsilon(e) = 28.5%). Moreover, the oxidation of TiNbZrTaHf alloy at elevated temperatures has a significant impact on its mechanical properties. The poor oxidation resistance of TiNbZrTaHf can accelerate tensile failure by inducing fractures at grain boundaries.