Effect of Element Ti on Microstructure, Properties, and Thermal Stability of NbTaMoWTix Refractory High-Entropy Alloys

Abstract:

The effect of element Ti on the microstructures and mechanical properties of as-cast and annealed NbTaMoWTi_x (x=0, 1, 1.5, 2) refractory high-entropy alloys (RHEAs) was investigated. Results show that after Ti addition, the as-cast alloys maintain their original single body-centered cubic (bcc) structure. As for the mechanical properties, compared with those without Ti addition, the strength and ductility of NbTaMoWTi_x alloys increase by 93% and 215%, respectively. Furthermore, the NbTaMoWTi_x alloys exhibit outstanding thermal stability. After annealing at 1400 °C, they still maintain the single bcc structure, and their mechanical properties are even slightly improved. However, annealing leads to a significant deterioration in the mechanical properties of high-Ti-content alloys (NbTaMoWTi_1.5 and NbTaMoWTi₂), owing to the formation of Ti-rich acicular phases.