Laser welding was used to conduct autogenous welding of AlSi10Mg alloy fabricated by laser selective melting (SLM) technology and lap welding of the as-cast cover plate and SLM plate with similar composition. After welding, the weld was treated by three heat treatment processes (T5 single aging +T6 solution aging + annealing), and the microstructure as well as mechanical properties of the weld in each heat treatment state was analyzed. The results show that the microstructure of overlapped SLM welds is finer than that of autogenous welds, and the properties of overlapped SLM welds are better and more sensitive to heat treatment. After annealing and T5 single aging treatment, the dendritic structure with acicular eutectic silicon as network distribution at the edge of α-Al matrix of typical weld microstructure does not change, and the grain is coarsened to a certain extent. After solid solution treatment in T6 state, the Si network breaks, spheroidize and grows, and the eutectic Si distribution is more uniform, the number of pores in the weld increases and the volume of pores increases. After single aging treatment, the weld microhardness is increased, while annealing and solid solution treatment will reduce the weld microhardness.
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