Effect of annealing on the microstructure and mechanical properties of AlCrFeNiV high-entropy alloy fabricated by selective laser melting

This study systematically investigates the microstructural evolution and its effect on the mechanical properties of an Al_0.5Cr_0.9FeNi_2.5V_0.2 high-entropy alloy (HEA) fabricated by selective laser melting (SLM), examining both the as-built and annealed states. The results indicated that the SLM-built alloy possesses a hierarchically heterogeneous microstructure, mainly comprising columnar grains, dislocation-based substructures, and minor L1₂ precipitates. The SLM-built alloy exhibits good strength with a maximum ultimate tensile strength of 850 MPa and excellent ductility with an average elongation of 43.8%. Annealing induces the gradual disappearance of dislocation-based substructures, the coarsening of L1₂ precipitates, and the precipitation of BCC/B2 phases. The segregated BCC Cr-V-enriched precipitates or zones thermodynamically destabilize the Cr-depleted matrix, which promotes the precipitation and growth of the L1₂ phase in annealed samples. Specifically, the distinct rapid growth of L1₂ precipitates can be ascribed to a synergistic interplay between dislocation-assisted fast diffusion and the inherent sluggish lattice diffusion of HEAs. However, annealing at an excessively high temperature causes the precipitation of a large amount of the brittle B2 phase, leading to reduced ductility. Notably, the alloy annealed at 700 °C demonstrates an exceptional strength-ductility synergy, achieving an ultimate tensile strength of 1019 MPa and an elongation of 28.3%. These findings offer an effective strategy for tailoring the microstructure and mechanical properties of SLM-built alloys and hold substantial potential for engineering applications in the manufacturing of complex components using such alloys via SLM.