Phase composition and solid solution strengthening effect in TiZrNbMoV high-entropy alloys

TiZrNbMo_xV_y high-entropy alloys (HEAs) with x=0-2, y=1 and y=0.3, respectively, were designed and prepared by copper mold casting technology. The phase composition and stability of these HEAs were investigated. It is shown that the HEAs with low content of V are composed of only one type of bcc solid solution phase (SSP), and demonstrate excellent phase stability at 1273K. The high content of V and Mo results in the formation of two types of bcc SSPs and the decrease of phase stability in the HEAs. Based on the previously proposed criteria, the formation ability of solid solution phase for this kind of HEAs was comprehensively evaluated. The compressive mechanical properties of the as-cast and annealed HEAs were measured. It has been found that Mo plays a strong solid solution strengthening effect on this kind of HEAs. Especially, TiZrNbMo_0.3V_0.3 has the yield strength and plastic strain of 1312MPa and >50%, respectively, and still maintains the excellent plastic deformation ability even after annealed at 1273K for 72h. The strengthening effect in this kind of HEAs is considered to be due to the shear modulus mismatch. The solubility limit of HEAs is correspondent to shear modulus mismatch of 29.