In this study, a low-cost refractory high-entropy alloy (RHEA) with obvious macroscopic tensile ductility was designed. The evolution of the microstructures and fundamental mechanical properties with the TiZr concentration in arc-melted (TiZr)x(NbTaV)1−x (x = 0.4, 0.6, and 0.8) high-entropy alloys (HEAs) were investigated. The alloys (TiZr)0.4(NbTaV)0.6 and (TiZr)0.6(NbTaV)0.4 had a single body-centered cubic solid solution phase. Two phases were confirmed in the as-cast (TiZr)0.8(NbTaV)0.2 alloy using X-ray diffraction and scanning electron microscopy. All three alloys had dendritic structures with severe element segregation. (TiZr)0.4(NbTaV)0.6 had a high yield strength of 1300 MPa with a compressive fracture strain of 16%. (TiZr)0.8(NbTaV)0.2 showed exceptional compressive plasticity but a low yield strength. (TiZr)0.6(NbTaV)0.4 had a relatively uniform yield strength and compressive fracture plasticity (950 MPa and 35%). In addition, (TiZr)0.8(NbTaV)0.2 also had a tensile ductility of 7% at room temperature.

The NbTaHfTiZrV0.5 is a refractory multi-principal-element alloy with high strength and good ductility at room temperature. It is important for possible high-temperature applications to investigate the deformation mechanism of the NbTaHfTiZrV0.5 alloy at different temperatures using tensile tests. In this investigation, the tensile tests were conducted at room temperature to 1273 K on sheet materials fabricated by cold rolling combined with annealing treatments. At 473 K, the NbTaHfTiZrV0.5 alloy exhibited a high tensile ductility (12%). At a testing temperature range of 673~873 K, the ductility was reduced, but the yield strength remained above 800 MPa, which is rare in most other alloys. The TEM investigations revealed that a dislocation slip controlled the plastic deformation, and the degree of deformation was closely related to the dislocation density. The true stress–strain curves of the alloy under different deformation conditions were obtained by tensile deformation at different deformation temperatures (673~873 K) and strain rates (0.001~0.0005 s−1). Experimental results were utilized to construct the parameters of a constitutive model based on a traditional mathematical model to predict the flow behavior at high temperatures. The excellent high-temperature mechanical properties of the NbTaHfTiZrV0.5 alloy will enable it to be used in several engineering applications.