In Situ Ageing with the Platform Preheating of AlSi10Mg Alloy Manufactured by Laser Powder-Bed Fusion Process

AlSi10Mg alloy is mainly produced by laser fusion on a powder bed. It offers a good compromise between easy processing and good mechanical properties. These properties depend on the manufacturing parameters, including the preheating temperature, as this alloy hardens by precipitation. This study explored the effect of preheating to 170 °C on the mechanical properties and microstructure of this alloy as a function of the manufacturing time. The mechanical properties were characterized by tensile, hardness and impact strength tests as a function of the sample height. An anisotropic behavior was confirmed: the horizontal orientation showed higher deformation and fracture energies. In addition, a gradient of properties appeared as a function of the distance from the platform; the closer the sample was to the platform, the higher its fracture energy and the lower its hardness. The hardness values followed the same evolution as a function of the distance to the platform as that of the hardness curve after ageing post-treatment. It was therefore shown that the preheating of the platform generated in situ ageing with respect to the manufacturing height: a hardness peak was obtained at a certain distance from the plateau (40 mm—10 h of remaining manufacturing time) and over-aging near the plateau was induced by long exposure times at 170 °C.