Impact of Vanadium and Zirconium Contents on Properties of Novel Lightweight Ti3ZryNbVx Refractory High-Entropy Alloys

This research explores the physical properties of refractory high-entropy alloys Ti3ZryNbVx (0.5 ≤ x ≤ 3.5; 1 ≤ y ≤ 2), utilizing the first-principles exact muffin-tin orbitals method, in addition to the coherent potential approximation. We examine the atomic size difference (δ), the valence electron concentration (VEC) and the total energy of the body-centered cubic (bcc), the face-centered cubic (fcc) and the hexagonal close-packed (hcp) lattices, revealing a disordered solid solution with a bcc lattice as the stable phase of these alloys. The stability of the bcc Ti3ZryNbVx alloys increases with the addition of vanadium, and slightly decreases with increasing Zr concentration. All the investigated RHEAs have densities less than 6.2 g/cm3. Adding V to the Ti-Zr-Nb-V system reduces the volume and slightly enhances the density of the studied alloys. Our results show that increasing V content increases the tetragonal shear modulus C′, which assures that V enhances the mechanical stability of the bcc phase, and also increases the elastic moduli. Moreover, all the examined alloys are ductile. Vickers hardness and bond strength increase as V concentration increases. In contrast, decreasing Zr content reduces the density and increases the hardness and the bond strength of the present RHEAs, potentially resulting in systems with desirable mechanical properties and lower densities. These findings provide theoretical insights into the behavior of RHEAs, and emphasize the necessity for additional experimental investigations.