Abstract: Selective laser melting (SLM) was used to prepare TiN/AlSi10Mg alloy composites. In order to further improve the mechanical properties of the specimen and eliminate the residual stress in the forming process, different heat treatment processes (aging, stress relief annealing, T6) were selected for microstructure regulation. The results show that the average hardness of the formed specimens is 136.2 HV0.2, the tensile strength is 397.7 MPa, the elongation is 12.5%, and the microstructure is composed of primary α-Al matrix decorated with brilliant white eutectic Si networks. After T6 treatment on the SLM specimens, the continuous Al-Si eutectic structure disintegrates at 520 ℃ and 2 h, and the discrete Si particles undergo Ostwald ripening, the elongation (11.0%) is similar to that of the formed specimen, and the tensile strength decreases to 239.1 MPa. After stress relief annealing treatment at 250 ℃ for 2 h, a small number of mesh Si boundaries are spheroidized, and the tensile strength and elongation decrease (344.9 MPa, 8.8%). After aging at 160 ℃ for 6 h, the fine a-Al/Si eutectic structure formed during SLM forming is basically retained, while the residual stress is reduced by 78.9%, and at the same time, the precipitations of nanoscale Si phase and Mg₂Si strengthening phase are promoted, the optimal mechanical properties are obtained with the hardness of 143.5 HV0.2, tensile strength of 408.7 MPa, and elongation of 15.3%. It is shown that an appropriate aging treatment can be used to obtain the best comprehensive mechanical properties, and also significantly reduce the residual stress.

Key words: additive manufacturing, selective laser melting, TiN/AlSi10Mg alloy composites, heat treatment, mechanical properties