Effect of layer thickness on the microstructure and machinability of AlSi7Mg processed by laser powder bed fusion

This study examines the influence of laser powder bed fusion (LPBF) layer thickness on the machinability of AlSi7Mg aluminum alloy. Samples fabricated with layer thicknesses of 20, 25, and 30 µm were heat-treated and then turned under fixed cutting parameters. The machinability was assessed in terms of cutting forces, surface roughness, and surface defects. Results showed that decreasing the layer thickness increased cutting forces and surface roughness, with the samples produced with a 20 µm layer thickness exhibiting the poorest machinability. The explanation of the lower machinability with decreasing layer thickness was associated with the microstructural and mechanical features characterizing the samples. At lower layer thickness, the microstructure is more anisotropic and ductile, leading to higher cutting forces and rougher surfaces. Contrarily, at greater layer thicknesses, the more uniform and less tough microstructure results in lower cutting forces and smoother surfaces. The presence of different Fe-rich intermetallics at different layer thicknesses also influences the morphology of the defects found on the machined surfaces. The findings highlight the importance of optimizing layer thickness to enhance the machinability of LPBF AlSi7Mg parts.