Reducing the energy density in Selective Laser Melting of an Al-Si-Mg-Cu alloy through an improved spreading process of the powder bed

Abstract

The Selective Laser Melting of aluminum alloys usually demands extremely high energy densities compared to the relatively low melting temperature of the material. This is attributed to the high reflectivity that reduces the energy effectively transferred to the material and the high thermal conductivity that dissipates the adsorbed heat. Reducing the energy consumption of manufacturing processes is one of the main research streams of the last years and is where the scope of this paper lies. The key assumption of this paper is that the energy efficiency of the process can be enhanced by increasing the packing factor of the powder bed, which leads to higher energy adsorption. A discrete element method model is developed to study the spreading of the powders and to determine the layer thickness and the spreading speed to maximize the packing factor. These parameters are used and the selective laser melting process is carried out by adopting three different energy densities, lower than the ones usually implemented. For each energy density, four different laser powers are adopted to better investigate the beam-matter interaction. Densification, roughness, microstructure, and microhardness are measured to assess the effectiveness of the process.