Alloying Effect on Elastic and Mechanical Properties of Refractory Medium-Entropy Alloys from First-Principles Calculations

There is still a challenge to rapidly and accuratelyacquire thecomposition dependence of mechanical properties of multi-principalelement alloys due to their huge composition space and complex electronicstructures. Aiming to straightforwardly tune the mechanical propertiesthrough alloying, we systematically calculate the elastic and mechanicalproperties for four selected body-centered-cubic (bcc) Ti-Nb-M(M = Zr, Mo, Sn, Ta) refractory medium-entropy alloys (RMEAs) usinga first-principles method. It is shown that the elastic stabilityof the bcc RMEAs can be significantly (weakly) improved with the increasein Nb, Mo, and Ta (Sn) content, but it is insensitive to Zr. The elasticstability, elastic modulus, hardness, and strength generally enhance,whereas Pugh's ratio and Zener anisotropy (A (Z)) decrease with the increase in valence electron concentration.Additionally, there is a correlation between the magnitude of the A (Z) and the shape of the single-crystal Young'smodulus (E ([hkl])). Thelargest (smallest) E ([hkl]) appears in the () direction. Particularly,themost isotropic Ti60Nb20Mo20 has thehighest hardness and strength among all the Ti-Nb-Malloys. Moreover, the change of elastic properties induced by alloyingis related to the change of density of states. This work sheds deeplight on the design of high-performance Ti-based multi-principal elementalloys.