Investigation on structural stability of as-cast Al0.5CrCuFeMnTi high entropy alloy

Abstract

To reveal the bonding effect of alloying elements in high entropy alloys and the source of structural stability of alloys, an as-cast Al0·5CrCuFeMnTi high entropy alloy was synthesized by arc melting under argon protection. The results show that the as-cast alloy is composed of a hexagonal close-packed (HCP) and a body-centered cubic (BCC) structure, and there is a distinct phase interface with a disordered arrangement of atoms between the dendritic (DR) and interdendritic (ID) regions. The calibrated (002), (110), and (112) crystal faces determined through high-resolution transmission electron microscopy confirm that DR phase has the HCP structure, while the ID phase forms solid solutions with the BCC structure by calibrated (110), (01-1), and (12-1) crystal faces. The results from first principles calculations show that the structural stability of the alloy is improved by the strong covalent bonding between Fe and Al, Cr, Fe, Ti atoms in the DR region, and between Al and Cu, Mn atoms in the ID region. The calculated results of solid solution parameters show that the atomic size difference and the mixing enthalpy of this alloy satisfy the criteria for stable solid solutions.