Research on the multiscale microstructure evolution and mechanical properties of LPBF-fabricated AlSi10Mg aluminum alloy after solution and aging treatment

Abstract Currently, there are few reports on the correlation between eutectic Si precipitation and mechanical properties of laser powder bed fusion (LPBF) fabricated AlSi10Mg alloy after solution and aging treatment. Therefore, this study quantitatively investigates the evolution of precipitated Si and changes in dimple size through multiscale characterization to systematically examine the microstructure and mechanical properties of LPBF-produced AlSi10Mg alloy. The results demonstrate that in terms of microstructure, the as-deposited samples exhibit typical fish-scale melt pool morphology with internal microstructure primarily consisting of Al matrix and network-like eutectic Si structure. After solution and aging heat treatment, with increasing temperature and holding time, the melt pool boundaries become indistinct while the network-like eutectic Si structure fragments and spheroidizes, gradually transforming into larger Si particles with maximum average area reaching 4.892 μm 2 . Regarding mechanical properties, the as-deposited samples show the highest tensile strength (476.36 MPa), yield strength (295.46 MPa) and hardness (132.78 HV), but the lowest elongation (9.21%). After solution and aging treatment, both tensile and yield strengths decrease by approximately 50% compared to the as-deposited state. At 500 °C, as holding time increases from 2 h to 6 h, the tensile and yield strengths first increase then decrease in a stepwise manner with no significant overall variation, while at 550 °C they gradually decrease with increasing holding time, again without notable overall change. The hardness shows severe degradation, dropping from initial 122.30 ± 10.5 HV to minimum 70.2 ± 0.1 HV. Fractographic analysis reveals that dimple size progressively increases with higher treatment temperature and longer duration, reaching maximum size of approximately 48 μm 2 and average size of 9.483 μm 2 at 550 °C/6 h condition. This study employs multiscale characterization from microscopic to macroscopic levels to quantitatively evaluate the effects of solution and aging treatment on microstructure and properties of LPBF-fabricated AlSi10Mg alloy, providing scientific basis for process parameter optimization.