Microstructure and phase stability study of NbMoZrTi light refractory high entropy alloy

Light Refractory High Entropy Alloys (LRHEAs) with good high temperature phase stability are important for overcoming material failures in high temperature environments. In this work, NbMoZrTi LRHEAs were designed and prepared using the vacuum arc melting technique. The microstructure and mechanical properties of NbMoZrTi LRHEAs were investigated before and after annealing at different temperatures (600 degrees C, 800 degrees C and 1000 degrees C). The results show that both cast and annealed NbMoZrTi LRHEAs have a single-phase BCC structure and exhibit excellent high-temperature phase stability. The microhardness of the alloy reaches up to 591.18 HV 0.2 after prolonged annealing at 600 degrees C, while the residual stresses are gradually released and the hardness decreases with increasing annealing temperature. Compression test results show that as the annealing temperature increases, the yield strength of the alloy increases and then decreases, the yield strength of the specimen annealed at 600 degrees C is the highest (1538 MPa), the ultimate compressive strength is the highest (2193 MPa), the high hardness and high strength are mainly attributed to the solid solution strengthening effect of the alloys. As the increase in annealing temperature further eliminates the internal stresses in the alloy, the plastic strain first decreases and then increases to 27.6 % in the annealed specimen at 1000 degrees C. This paper demonstrates the excellent high-temperature phase stability of NbMoZrTi LRHEA through the study of NbMoZrTi LRHEAs with different annealing temperatures, and proposes the technical applications of NbMoZrTi LRHEAs in the high- temperature fields of aerospace and nuclear energy.