Tailoring the mechanical potential of a PBF-LB/Med Al-Si-Cu alloy through heat treatment customization

Al-Si and Al-Cu alloys are widely employed in laser-based powder bed fusion of metals (PBF-LB/M) and are well known for the fine cellular microstructures and high solute supersaturation achieved through rapid solidification, which contribute to their outstanding properties. However, most post-processing studies have focused on AlSi10Mg or Al–Si–Cu alloys containing Cu levels within the solubility limit of the Al matrix, while the directaging behavior of high-Cu compositions, such as AlSi10Cu8Mg, remains largely unexplored. In particular, the interaction between precipitation-related strengthening and the stability of the Al–Si–Cu-rich cellular network has not been systematically clarified. In this study, gas-atomized AlSi10Cu8Mg was processed by PBF-LB/M and directly aged from the as-built condition. The research was conducted in four successive stages. First, gasatomized AlSi10Cu8Mg powders were processed by PBF-LB/M and the bulk samples were characterized in the as-built condition. Second, differential scanning calorimetry was used to identify the main transformation ranges and guide the selection of the aging temperatures. Third, the specimens were directly aged at 140–180 ◦C to promote controlled precipitation while preserving the cellular network, or at 250–350 ◦C to accelerate microstructural coarsening and network fragmentation. Finally, the phase constitution, microstructure, near-surface residual stress, hardness, and tensile response at room temperature and 200 ◦C were evaluated and correlated with the applied thermal conditions. The as-built alloy exhibited high strength but limited ductility. Aging at 160 ◦C promoted a moderate hardening response, with peak hardness after 10 h. The heat treatment at 160 ◦C for 24 h effectively preserved the as-built yield strength while reducing elongation by about 18 %. In contrast, the heat treatment at 250 ◦C for 4 h markedly improved ductility, increasing room-temperature elongation by approximately 50 %, although with a little reduction in yield strength. This treatment also enhanced the hightemperature tensile response, with elongation reaching 2.60 % at 200 ◦C, and reduced the near-surface residual stress by approximately 50 % compared with the as-built condition. These results demonstrate that the strength–ductility balance is governed by the interplay between precipitation-related processes and the preservation or fragmentation of the cellular network