Effect of Al on the microstructure, mechanical properties, and wear resistance of TiVZrNbAl_x alloys

In this study, the microstructure, mechanical, and tribological properties of (Ti₄₂V₂₈Zr₁₅Nb₁₅)_100-xAl_x lightweight refractory high-entropy alloys (LRHEAs) were systematically investigated. The results show that the single BCC solid solution structure of LHEAs is maintained after the addition of Al elements, and no other phases are formed. The addition of Al elements to the alloys can be reduce density, improve properties, and enhance wear resistance. While the hardness of the alloy increased from about ~ 352 HV to ~ 430 HV, the tensile ductility decreased significantly. The main reason for the increase in hardness is the strong bonding between aluminum atoms and other atoms. On the other hand, the severe impairment of the tensile properties may be due to the decrease in GNDs. Although the addition of Al helps to reduce the coefficient of friction, the wear rate of the alloy increases.