Phase transformations of HfNbTaTiZr high-entropy alloy at intermediate temperatures

The strong and ductile single-phase body-centered-cubic (BCC) HfNbTaTiZr refractory high-entropy alloy (RHEA) is a potential structural material for high-temperature applications. However, the BCC phase stability in the intermediate temperature range (500–900 °C) needs to be better understood to make this alloy applicable to industry. In the present work, the phase decomposition of the HfNbTaTiZr RHEA is examined at different temperatures (500–1000 °C). Additionally, the formation of BCC Ta-Nb-rich and hexagonal-close-packed (HCP) Hf-Zr-rich precipitates are studied as a function of annealing time at 700 °C using a combination of atom probe tomography, transmission electron microscopy, and X-ray diffraction. We found that these BCC and HCP precipitates have preferred orientations with the BCC matrix.