Preparation of a novel high-entropy alloy AlNbTiVZr with excellent strength and ductility: The effect of Zr composition on microstructure and properties

Abstract

Light-weight refractory high-entropy alloys with low density and good ductility are widely used in various engineering fields. Despite their potential, achieving an optimal strength-ductility balance in these lightweight alloys remains an emerging field of study. In this study, Al_0.8Nb_0.5Ti₂V₂Zr_x (x = 0, 0.3, 0.6, and 0.9) alloys were prepared by vacuum arc melting. A comprehensive evaluation of their microstructure, density, hardness, and compressive behavior at both room and 873 K temperatures was conducted. The introduction of Zr transforms the alloy phase structure from body-centered cubic (BCC) to BCC + C14-Laves. The areal fraction of the C14-Laves phase increased from 0 % to 32.47 % with increasing Zr content from x = 0 to 0.9, respectively. Furthermore, the Zr content had an obvious effect on the mechanical properties of the alloys. The compressive strength and hardness of the alloys improved, but the ductility simultaneously decreased, with increasing Zr content. The yield strengths of the alloys with x = 0, 0.3, 0.6, and 0.9 reached 971, 1216, 1483, and 1714 MPa, respectively, at room temperature, and 946, 1287, 1319, and 1469 MPa, respectively, at 873 K. In addition, the alloys maintained their deformation resistance and good ductility at 873 K. In particular, the Al_0.8Nb_0.5Ti₂V₂Zr_0.3 exhibited a good balance between strength and ductility at room and 873 K temperatures due to the strengthening effect of a granular secondary phase. Upon comparison with other reported high-entropy alloys, the Al_0.8Nb_0.5Ti₂V₂Zr_x series showcased superior specific yield strength and ductility.