Most of the complex components applied in the aerospace field need to add support structures in the selective laser melting process, and the block support structure is the most widely used one. To determine the reasonable support spacing and the post-processing allowance of the overhang surface, the influence of support spacing on the relative density, surface morphology, microstructure and hardness of the selective laser melted AlSi10Mg material is studied, and the influence mechanism of the support structure on the formability of the material is revealed through numerical simulation. The results show that the average relative density of the samples varied from 96.7% to 97.3%. When the support spacing is less than 1 mm, the roughness of the lower surface of the samples maintained to be about 0.28 mm after the support is removed. The start few layers of the samples can be divided into the defect area, transition area, and dense area. When the support spacing was less than 1 mm, the thickness of the defect area is maintained to be about 456 μm. The network Si phase in the defect area is coarse and sparse, with a microhardness of 90 HV0.1, while in the dense area, the network Si phase is fine and dense, with a microhardness of 115 HV0.1. The support structure can effectively prevent the molten metal from invading the lower layer powder, and maintain the normal shape of the molten pool (the maximum length is 190 μm, and the maximum width is 100 μm), which is conducive to the full melting of the metal powder in the molten channel to ensure the formability of the material. In laser additive manufacturing of aluminum alloy complex components, setting the optimal support spacing to 1 mm can reduce material waste and processing time. If the machining allowance is set to 456 μm for the overhang surface of the complex component, the defect area can be removed in post-processing to ensure the dimensional accuracy and performance of the component, and precise laser forming can then be realized.
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