Effects of V content on the microstructure and mechanical properties of Nb₃₁Ti_37-xZr₂₆Al₆V_x refractory medium-entropy alloys

Most refractory complex concentrated alloys (CCAs) exhibit limited plasticity and high density, which greatly limits their large-scale applications. To address these issues, a series of Nb₃₁Ti_37-xZr₂₆Al₆V_x (x = 3, 5, 7, 9, and 11 at. %) refractory medium-entropy alloys (RMEAs) were designed and prepared in this work with the help of phase diagram calculation software. The synergistic effects of V and Ti on the microstructure, mechanical properties, and strengthening mechanisms of Nb₃₁Ti_37-xZr₂₆Al₆V_x RMEAs are investigated in detail. Compared with the reported CCAs with limited plasticity and high density, our alloys with a single BCC structure offer excellent compressive plasticity greater than 50% at room temperature and a lower density less than 6.4 g/cm³. Alloys have higher yield strength at room temperature with the increasing content of V. The high yield strength of alloys primarily originates from the inherent yield strength of the alloy's components and the solution strengthening resulting from the lattice distortion. The alloys studied in this work provide evidence that the high-strength RMEAs with excellent plasticity can be obtained through careful composition design.