Effect of Hf Substitution on Mechanical Properties of TiNbTaZr Medium Entropy Alloy by First Principle Calculation

In order to explore the mechanism of mechanical properties of TiNbTaZr after non-Ti elements are replaced by Hf from the perspective of electronic structure. Analyzing the structural characteristics of TiNbTaZr, TiHfNbZr, TiNbHfZr, and TiNbTaHf medium entropy alloys by solid solution characteristic parameters. Establishing the corresponding structural models and dealing with the first-principles calculations. By analyzing the binding energy and formation enthalpy, it is determined that these four alloys are metastable & beta;-Ti alloys of disordered solid solution, and the thermodynamic stability of the structure is confirmed by phonon spectrum. The elastic constants, Poisson's ratio, and hardness of these four alloys show that the strength of Hf-containing alloys is improved and the ductility is slightly reduced compared with TiNbTaZr. From the analysis of population and density of states, it is concluded that the reason for the above phenomenon is that Hf will cause the improvement of bonding stability and covalency of alloy materials, thus promoting the improvement of theoretical strength of alloys. TiNbHfZr exhibits excellent properties of high strength and low elastic modulus and has good ductility.