Development of MoNbVTax refractory high entropy alloy with high strength at elevated temperature

Due to a monolithic body-centered cubic solid solution structure, refractory high-entropy alloys (HEA) always exhibit high strength and good softening resistance at both ambient and elevated temperatures. However, high density and low plasticity at ambient temperature limit their widespread applications as one kind of potential structural materials. The present study investigated the microstructure and mechanical properties of MoNbVTa x HEA with various Ta conent at both ambient and elevated temperatures. The sample of MoNbVTa x (x = 0, 0.3, 0.5, 0.7, 1) all shows a monolithic BCC solid solution phase with a dendritic microstructure. The micro-segregation of constituent elements was caused by the non-equilibrium solidification. The alloys exhibit superior high temperature performance at 1000 °C and 1200 °C, with a certain degree of plasticity at ambient temperature. The MoNbVTa 0.5 alloy possesses both excellent high temperature performance ( σ 0.2 =697 MPa, ε p = 35.4% at 1200 °C) and relatively low density (∼9.65 g/cm 3 ), which is attributed to the solid solution strengthening effects and excellent thermal stability of constituent phase. Compared with commercial superalloys, the present MoNbVTa HEAs possess the advantages of high temperature performance, making it a potential engineering material for structural application. • The microstructure and mechanical properties at both ambient and elevated temperatures of MoNbVTa x HEAs are investigated. • The degree of elemental micro-segregation can be quantitatively analyzed, more severe with more Ta. • All MoNbVTa x alloys exhibit excellent strengths and plasticity at ambient temperature and elevated temperatures. • MoNbVTa 0.5 shows the best high temperature mechanical property, yielding at near 700 MPa at 1200 °C. • The yield strength of different alloys could be described by the solid solution strengthening mechanism.