Design of oxygen-doped TiZrHfNbTa refractory high entropy alloys with enhanced strength and ductility

Refractory high entropy alloys (RHEAs) are considered promising materials for high-temperature applications due to their thermal stability and high-temperature mechanical properties. However, most RHEAs have high density (>10 g/cm(3)) and exhibit limited ductility at low temperatures and softening at high temperatures. In this study, we show that oxygen-doping can be used as a new alloy design strategy for tailoring the mechanical behavior of the TiZrHfNbTa alloy: a novel low-density (7.98 g/cm(3)) ductile RHEA. Even though the material is a single-phase BCC with some oxides at room temperature, secondary BCC and HCP nano-lamellar structures start to form above 600 degrees C in addition to the nanotwins which are shown to be stable up to 1000 degrees C. This alloy shows superior strength and compressive ductility due to the nanoengineered microstructure. The present study sheds light on tailoring the strength-ductility balance in RHEAs by controlling the microstructure of novel RHEAs at the nanoscale via oxygen-doping. (c) 2022 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).