Effect of Nb Content on Microstructure and Mechanical Properties of Mo0.25V0.25Ti1.5Zr0.5Nbx High-Entropy Alloys

High-entropy alloys (HEAs) have significant application prospects as promising candidate materials for nuclear industry due to their excellent mechanical properties, corrosion resistance and irradiation resistance. In this work, the Mo_0.25V_0.25Ti_1.5Zr_0.5Nb_x (x = 0, 0.25, 0.5, 0.75 and 1.0) HEAs were designed and fabricated. The alloys were prepared by vacuum arc melting, and all the ingots were annealed at 1200 °C for 24 h. The microstructures, crystal structures, hardness and mechanical properties of Mo_0.25V_0.25Ti_1.5Zr_0.5Nb_x HEAs were investigated. The as-cast alloys are composed of single BCC phase. Moreover, the single BCC phase is retained after annealing at 1200 °C for 24 h. The compressive and microhardness tests show that the strength and hardness of the alloys decrease gradually with the increase of Nb content, while the plasticity increases and the fracture mode of the alloy changes from brittle fracture to ductile fracture, which is mainly owing to the decrease of grain size. The addition of Nb significantly improves the plasticity of the Mo_0.25V_0.25Ti_1.5Zr_0.5Nb_x alloys. In particular, Nb1.0 alloy can reach 28.32 % strain without fracture, which exhibits promising potential in industrial application.