Effect of Al and Nb on microstructure and mechanical properties of novel Al-Mo-Nb-Ti-V-Zr lightweight refractory high-entropy alloys

Refractory high-entropy alloys (RHEAs) are a new family of metallic alloys which have been intensively studied in the last decade. Indeed, RHEAs likely have the potential of overcoming the high-temperature performances of conventional Ni-based superalloys. Nevertheless, up to date, their high density and poor room temperature ductility still compromise their industrial uptake. In this study, novel RHEAs compositions are investigated to provide insights on the development of strong and ductile lightweight RHEAs. Specifically, Al x MoNb y TiVZr alloys (with x = 0, 0.25, 0.5, 0.75, 1 and y = 1, 2) have been produced and characterized. These alloys have been designed to probe the possibility of reducing the density of RHEAs by increasing the Al content. At the same time, the content of Nb was also increased in the attempt to counterbalance the embrittlement effect related to Al addition. • Novel Al x MoNb y TiVZr lightweight RHEAs (x = 0 ÷ 1 and y = 1, 2) were studied. • Increasing Al content reduced the ductility at room temperature. • Increasing Nb content enhanced the yield strength at 800 °C. • MoNb 2 TiVZr alloy exhibited the highest fracture strain of 15 % at room temperature.