Influence of the laser beam focus on the mechanical properties and microstructure of AlSi10Mg processed by L-PBF

Over the last decade, Additive technologies have become one of the most interesting manufacturing techniques within the industry, particularly for metal techniques. Starting from the CAD file, Additive Manufacturing machines allow to produce any geometric shape without the usage of tools. Generally, the process is slower than convectional techniques, but it strongly depends on the geometrical complexity. What makes this process interesting are the many advantages it has, such as the reduction of components, the number of assemblies and the free design approach. There are several techniques available on the market for the fabrication of metal parts. The two main techniques are: Powder Bed Fusion (PBF) and Direct Energy Deposition (DED). Many parameters influence the building process and sometimes they can get in conflict to each other. The aim of this analysis is to evaluate the effect of laser beam focus variation on the microstructure and mechanical properties of parts made of AlSi10Mg and produced by the Laser-PBF technique. The AlSi10Mg alloy is often used in the Additive Manufacturing field as it presents good casting characteristics, a narrow cooling range and good specific strength. The main fields of usage for this alloy are the automotive and aeronautical industry. Three different laser spot sizes were analysed, coinciding with the conditions of -1.5, 0, +1.5 mm focusing distance. Nine samples were produced for each laser spot condition, 3 cubes for the microstructure characterisation and 6 samples for the tensile tests. Porosity, SEM microscope and melt pool analysis were carried out for the cubic samples. The tensile specimens were used for the tensile tests and characterisation of the fracture surfaces.