Nowadays the majority of aluminium alloys used for selective laser melting (SLM) is based on the Al-Si system, especially alloys containing 7 to 12 wt% Si and Mg-content < 1 wt%. Silicone has beneficial influence on the melt viscosity during casting and AM-processing and prevents the formation of cracks. After SLM these alloys are forming an eutectic Si-network which provides the main part of the strength improvement.
This study focuses on the development of new AlSiMg alloys for the selective laser melting process and the subsequent heat treatment process to adjust the mechanical properties in a wide range of strength and ductility. In contrast to alloys with higher Si- and lower Mg-content the strengthening by Mg2Si precipitates is more likely.
Different alloys with varying magnesium (1.5 to 5 wt%) and a reduced silicon content were selected, based on expected processing behavior and resulting mechanical properties. These alloys were gas atomized to produce fine powders with a particle size distribution of 20 to 63 µm. For all alloys process parameters for the selective laser melting process were determined to achieve almost full density. To address a wide range of automotive applications two independent heat treatment procedures were developed. One facing applications requiring high strength combined with medium ductility and one for applications requiring high ductility with lower demands on strength. The different conditions were characterized by tensile tests, bending tests according to VDA 238-100 and microstructural analysis.