High-Temperature Mechanical Properties of NbTaHfTiZrV Refractory High-Entropy Alloys.

The NbTaHfTiZrV 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 NbTaHfTiZrV 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 NbTaHfTiZrV alloy exhibited a high tensile ductility (12%). At a testing temperature range of 673873 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 (673873 K) and strain rates (0.001~0.0005 s). 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 NbTaHfTiZrV alloy will enable it to be used in several engineering applications.