A combinatorial evaluation of TiZrV_0.5Nb_0.5Si_x refractory high entropy alloys: Microstructure, mechanical properties, wear and oxidation behaviors

In this work, TiZrV_0.5Nb_0.5Si_x (x = 0.1, 0.2, 0.3) refractory high entropy alloys was used as a candidate system to comprehensively evaluate the relationship between microstructure, mechanical properties and elevated temperatures service performance. With the increasing Si addition, there is a transition from a single-phase BCC to a dual-phase comprising BCC and silicide phases in the microstructure, accompanied with an increasing microhardness/strength. Meanwhile, both wear and oxidation resistance over a wide temperature range were simultaneously improved. The formation of strong silicide phase has a significant effect on inhibiting the cracking of the oxide layer and hindering the volatilization of oxides, which makes the Si-containing refractory high entropy alloys have excellent oxidation resistance at high temperature. Moreover, the improvement of wear resistance could be attributed to the synergistic effect of mechanical properties and oxidation resistance. At medium and low temperatures, the adhesion wear was restrained by the enhanced microhardness and softening-resistance. The formation of dense glaze layer at elevated temperatures enables a low coefficient of friction and a low wear rate. The present results offer considerable insights into the design of refractory high entropy alloys for service in harsh environments.