The influence of heat treatments on the microstructures and mechanical properties of the selective laser melting manufactured AlSi10Mg alloy modified with Sc was systematically investigated. The results showed that the addition of Sc element introduced primary Al3Sc, which increased the heterogeneous nucleation during the solidification of AlSi10Mg alloy, and then the ultrafine network eutectic structure was obtained, and hence the tensile strength was improved significantly (nearly 23 %). During the heat treatment process, the network eutectic structure transformed from continuous to discontinuous, and the grain refinement was weakened with an increasing heating temperature, both of which affected the mechanical properties of the Sc modified AlSi10Mg alloy. The tensile strength decreased from 438 ± 10 MPa for the Sc-modified alloy to 208 ± 6 MPa, while the fracture strain significantly increased from 6 ± 0.2 % to 30.2 ± 1.2 % when the Sc-modified alloy was heat-treated at 325 °C for 12 h. It has been found that the desirable microstructure and mechanical properties of SLM Sc-modified AlSi10Mg alloy can be realized by controlling the heat treatment process parameters.
