Microstructure and tribological properties of TiZrV_0.5Nb_0.5Al_x refractory high entropy alloys at elevated temperature

A series of TiZrV_0.5Nb_0.5Al_x refractory high entropy alloys were prepared by arc-metling, aiming to solve the problems of high density, poor oxidation and wear resistance of refractory high entropy alloys at elevated temperature. The microstructure, mechanical and tribological properties were investigated. The results indicate that the increase in Al addition could promote precipitation of Laves phase in the BCC matrix, thus regulation the mechanical properties. The tribology behavior is strongly dependent on the temperature. Below 400 °C, the wear mechanism is dominated by mechanical wear. In this case, the TiZrV_0.5Nb_0.5Al_0.25 alloy with high strength and good ductility at the same time, exhibits optimal wear resistance. When the temperature increases above to 600 °C, the coefficient of friction and the corresponding wear rate dramatically decrease with Al addition, which could be attributed to the preformed formation of dense and stable oxide glazed-layer before wear. Accordingly, the main wear mechanism changes from mechanical wear to oxidation wear. This study provides an effective strategy for improving wear resistance and oxidation resistance of refractory high entropy alloys in a wide temperature range.