Effect of Ti on the structure and mechanical properties of Ti_xVNbMo (x=0.5, 1.0, 1.5, 2.0) refractory high-entropy alloys: A combined first principles and experimental study

The effect of Ti content on the Ti_xVNbMo (x = 0.5, 1.0, 1.5, 2.0) refractory high-entropy alloys (RHEAs) was systematically studied by combining experimental and theoretical calculations, focusing on phase composition, microstructure and mechanical properties. All the Ti_xVNbMo RHEAs have a BCC single-phase solid solution structure, and the lattice constant increases with the increase of Ti content. Thermodynamic and kinetic stability are confirmed through analyses of enthalpy of formation, cohesive energy, and phonon spectrum. With the increase of Ti content, the hardness, yield strength and elastic modulus gradually decrease, and all alloys are anisotropic. Ti2.0 alloy exhibits the best plasticity, while Ti0.5 alloy has the highest specific yield strength. The main strengthening mechanism of Ti_xVNbMo RHEAs is solid solution strengthening. The electronic structure of Ti_xVNbMo RHEAs was analyzed by COHP, and the results showed that the higher the Ti content, the weaker the internal bonding force, which leads to a decrease in compressive strength. Overall, this study provides insights into the microstructure and mechanical behavior of the Ti_xVNbMo RHEAs from multiple scales, which is crucial for their potential applications.