Microstructure evolution and mechanical properties of a novel CrNbTiZrAlx (0.25 ≤ x ≤ 1.25) eutectic refractory high-entropy alloy

In present study, microstructure evolution and mechanical properties in the CrNbTiZr refractory high entropy alloy upon Al addition were investigated. With an increase of Al content, the microstructure changes from hypoeutectic with primary BCC-phase dendrites to hypereutectic with primary Laves-phase dendrites. As Al content increases, the density decreases steadily from 6.57 g cm(-3) to 5.85 g cm(-3). The CrNbTiZrAl0.75 alloys at the eutectic composition exhibited low strength and poor ductility. The microstructure formation is explained by atomic size difference (delta) and parameter Delta chi(A). The delta >= 5.295% and Delta chi(A) >= 7.058 criterion is proposed to better predict the microstructure formation of the coexistence of (BCC + Laves) phases. (C) 2020 Elsevier B.V. All rights reserved.