Lightweight Ti-Zr-Nb-Al-V refractory high-entropy alloys with superior strength-ductility synergy and corrosion resistance

Refractory high-entropy alloys (RHEAs) are regarded as promising candidates of the next generation superalloys, mainly benefitting from the high strength at high temperatures. However, they are not competitive in lightweight, room-temperature ductility, and corrosion resistance compared with other superalloys. In this work, novel Ti1.6ZrNbAl0.4-xVx (x = 0, 0.2, 0.4) lightweight RHEAs (LRHEAs) were fabricated and systematically investigated. The substitution of V for Al promoted strength-ductility synergy and ameliorated the corrosion resistance of the current LRHEAs. More specifically, an increase in V content caused a phase transformation from a BCC + B2 dual phase structure to a single BCC phase structure and a reduction of grain sizes. Mechanical tests demonstrated that the Ti1.6ZrNbAl0.2V0.2 LRHEA possesses a high yield strength of ~806 MPa and a moderate tensile ductility of ~13.2%, which is attributed to synergetic strengthening from grain refinement and solid solution strengthening induced by V addition. In addition to the homogenous phase structure and fine grain sizes, excellent anti-corrosion properties of Ti1.6ZrNbAl0.2V0.2 LRHEA were also attributed to the doping effect of V, leading to the formation of a high content of corrosion-protective products. Our findings provide a new paradigm for achieving such outstanding combinations in LRHEAs.