Investigation of the Thermomechanical and Tribological Behaviors of a Non-equimolar Hf_0.5Nb_0.5Ta_0.5Ti_1.5Zr Refractory High Entropy Alloy

Mechanical, physical, thermodynamic and wear resistance properties of a non-equimolar and complex Hf_0.5Nb_0.5Ta_0.5Ti_1.5Zr refractory HEA, were studied. Various thermodynamic parameters like mixing enthalpy (ΔH_mix), a unitless variable (Ω), and configurational or mixing entropy (ΔS_mix) were investigated to characterize this multi-component alloy. The collective behavior of the constituent components was studied, and the nature of the solution was predicted. These calculated parameters confirm the forming of a solid solution, leading to a body center cubic (BCC) microstructure predicted by the valence electron configuration (VEC), which is confirmed by XRD analysis. The sluggish diffusion causes dendritic growth in the structure, a general characteristic of these HEAs. Further, wear behavior was analyzed and observed ploughing with plastic deformation, both dominating the wear mechanism confirmed by the field emission scanning electron microscopy and energy-dispersive x-ray spectroscopy analysis.