Heat treatment induced microstructural evolution and strength enhancement of Al–Cr–Fe–Ni–V high-entropy alloy fabricated by laser powder bed fusion

Herein, different heat treatment protocols are adopted to further improve the mechanical properties of the Al–Cr–Fe–Ni–V high-entropy alloy (HEA) fabricated by laser powder bed fusion (LPBF) additive manufacturing (AM). The initial LPBF-processed HEA rendered a combination of high strength (ultimate tensile strength (UTS) of 810.93 MPa) and ductility (fracture elongation (FE) of 35.43%), which could be attributed to the hierarchical microstructure with fine grains, cellular dislocation structure, and L1₂ nano-precipitation. When the annealing temperature is increased from 573 K to 1473 K, the cellular dislocation structure is disappeared, and both L1₂ and B2 phases are progressively precipitated in the FCC matrix. Simultaneously, the tensile strength dramatically increased at the expense of ductility reduced and LPBF-processed HEA demonstrated a high UTS of 1192.84 MPa and FE of 15.32% after annealing at 1173 K. The results reveal that precipitation strengthening plays a significant role in improving the mechanical properties of LPBF-processed HEAs during annealing. For instance, L1₂ and B2 precipitates hindered the dislocation movement and, in turn, enhanced the pinning force of boundary migration. Moreover, the highly coherent and low misfit FCC-L1₂ interfaces minimized the strain accumulation due to the dislocation shear and, thereby, prevented the crack initiation.