Effect of Different Heat Treatments on the Evolution of Novel Al-Si-Cu-Ni-Fe-Re Alloy Fabricated by Selective Laser Melting

In this study, Cu and Ni are successfully added to additively manufactured Al-Si alloy by the mixing process to improve the strength and ductility of the alloy. The effects of different heat treatments on the microstructural evolution and bending properties of selective laser-melted Al-Si-Cu-Ni-Fe-Re alloy are systematically investigated to optimize the mechanical properties. Nearly complete dense samples are initially additively manufactured with optimized parameters. The samples display a particular fiber network microstructure in which Cu-rich and Ni-rich phases distribute in an interwoven mesh around the eutectic silicon. After substrate plate heating (SPH) treatment, the network becomes denser, and the bending strength increases by 44.99 ± 1 MPa to 811.11 ± 29 MPa, despite the hardness decreases. Comparatively, solution aging (SQA) treatment results in the fiber network structures transforming into second-phase particles, which leads to a decline in bending strength and a significantly higher degree of ductility. Finally, the mechanisms of changes in microstructure and morphology, as well as mechanical properties after heat treatment, are discussed.