High mechanical and tribological performance and mechanisms of TiZrHfNbAlx refractory high-entropy alloys

Abstract

In this work, a series of TiZrHfNbAl_x (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) refractory high-entropy alloys (RHEAs) are synthesized by vacuum arc-melting techniques, and the effect of Al concentration on microstructure and wear properties were investigated. All alloys exhibit a single BCC structure. Interestingly, when x reaches 0.8, a new ordered BCC phase appears. As the increase in Al content, the hardness increased from 245 HV to 447 HV and the compressive yield strength (CYS) increased from 572 MPa to 1468 MPa for TiZrHfNb and TiZrHfNbAl_1.0 RHEAs, respectively. Meanwhile, the addition of Al significantly enhances the wear resistance of the RHEAs, the wear volume of TiZrHfNbAl_1.0 alloy decreased by 37.5 % in contrast with TiZrHfNb alloy. The above excellent performance of the TiZrHfNbAl_1.0 alloy was attributed to the synergistic effect of solid solution strengthening, ordered phase strengthening and a transformation of the wear mechanism.