BCC+L21 dual-phase Cu40Al20Ti20V20 near-eutectic high-entropy alloy with a combination of strength and plasticity

Abstract

To pursue a combination of strength and plasticity, a near-eutectic high-entropy alloy Cu40Al20Ti20V20 was developed by using a stoichiometric ratio of the L21 Cu2AlTi ordered phase. The results showed that a soft-hard alternating BCC (α)+L21 (β) dual-phase structure was realized. The as-cast alloy was composed of BCC (αp) dendrites, and a lamellar and rod-like BCC+L21 Cu2AlTi (α + β) eutectic structure with a small amount of FCC Cu-rich phase embedded within. Due to the soft-hard dual-phase structure and large number of phase interfaces of the eutectic, the as-cast alloy possessed a high yield strength of 1300 MPa and plasticity of 6.3%. Annealing facilitated the precipitation of a substantial number of L21 nanoparticles (βII) in the dendrites and the diffusion of Cu atoms from the Cu-rich phase to the matrix. The desolation transformation of βII and the Cu diffusion during annealing increased the formation of excess L21 hard-phase to ~50 vol%. Many micro-pores were also formed, which facilitated crack initiation and deteriorated the strength and plasticity of the homogenized alloy.