Microstructure and mechanical properties of refractory high-entropy alloys of NbTaZrMo_x system

Herein, we describe a study where thermodynamic phase diagram calculations were used to design a material whose composition would afford high strength and plasticity. To this end, several NbTaZrMox (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) refractory high entropy alloys (RHEAs) were prepared using a vacuum arc melting process. The experimental results showed that the NbTaZrMox RHEAs was mainly composed of Ta, Mo, Nb-rich BCC1 phase and Zr-rich BCC2 phase, and the microstructure is typical dendrite state. With the increase of Mo content, the hardness and room temperature yield strength of the alloy improved. The room temperature compressive yield strength of the Mo0.8 alloy was 1569 MPa, which was about 1.8 times greater than the equimolar NbTaZr alloy, while room temperature plasticity was maintained at 20 %. The excellent strength of the alloy was mainly the result of the effect of solid solution strengthening.