Microstructure, mechanical properties and corrosion resistance of laser direct energy deposited AlMo0.25FeCoCrNi2.1 high-entropy alloy: adjusted by annealing heat treatment

Abstract

A novel AlMo0.25FeCoCrNi2.1 high-entropy alloy (HEA) was additively manufactured using laser direct energy deposition (LDED) process. The microstructure, mechanical properties and corrosion resistance of the prepared alloy were investigated and adjusted by annealing heat treatment. The results showed that inadequate melting and diffusion of Mo powders cause the nonuniform Mo concentration and finally result in the microstructure diversity in the banded layer. Fine lamellar eutectic structures composed of Mo-rich σ phase and body-centered cubic (BCC) phase form within Mo supersaturated FCC phases. The annealing heat treatment promotes the precipitation and coarsening of needle-like B2 phases within the incipient FCC phases and granular σ phases at phase boundaries between FCC and BCC/B2, synergistically improving the toughness of this alloy with slight deterioration of ultimate tensile strength. The corrosion resistance of the alloy is notably improved by a 2-hour annealing heat treatment. These results contribute to rapidly designing/manufacturing/adjusting novel HEAs by LDED process.