An as-cast Ti-V-Cr-Al light-weight medium entropy alloy with outstanding tensile properties

Light-weight (LW) high/medium entropy alloys have gained much attention due to the high specific strength, but they usually suffer from poor ductility, especially in the tensile tests at the as-cast state. In this study, the mechanical properties of a series of Ti-V-Cr-Al medium entropy alloys, with Ti and V maintaining equiatomic ratio, are investigated. An outstanding strength-ductility relationship is achieved in a (TiV)₉₁Cr_4.5Al_4.5 alloy, with a relatively low density of 5.1 g/cm³, a high specific yield strength of 160 MPa/(g/cm³), and a high tensile fracture elongation over 30%, even at its as-cast state. The tensile deformation is dominantly through the typical nucleation, planar migration, and entanglement of dislocations. Secondary phase formation and chemical inhomogeneity in this alloy are both insignificant. The frustration of dislocation motions are mainly attributed to the solid solution strengthening, which also enhances the work-hardening, delays the occurrence of necking, and benefits the overall ductility. The outstanding specific strength-ductility combination of this LW-alloy at the as-cast state makes it promising for potential engineering applications.