Process window for highly efficient laser-based powder bed fusion of AlSi10Mg with reduced pore formation

Abstract

The process window for highly efficient laser-based powder bed fusion (LPBF), ensuring the production of parts with low porosity, was determined by analyzing cross-sections of samples that were generated with laser powers varying between 10.8 W and 1754 W, laser beam diameters varying between 35 µm and 200 µm, and velocities of the moving laser beam ranging between 0.7 m/s and 1.3 m/s. With these parameters, the process alters between different modes that are referred to as simple heating, heat conduction melting (HCM), key-bowl melting (KBM), and deeppenetration melting (DPM). It was found that the optimum process window for a highly efficient LPBF process, generating AlSi10Mg parts with low porosity, is determined by the ratio PL /db of the incident laser power PL and the beam diameter db of the beam on the surface of the bead, and ranges between PL /db = 2000 W/mm and PL /db = 5200 W/mm, showing process efficiencies of about 7–8%. This optimum process window is centered around the range PL /db = 3000–3500 W/mm, in which the process is characterized by KBM, which is an intermediate process mode between HCM and DPM. Processes with PL /db < 2000 W/mm partially failed, and lead to balling and a lack of fusion, whereas processes with PL /db > 5200 W/mm showed a process efficiency below 5% and pore ratios exceeding 10%.