Process Window for Highly Efficient Laser-Based Powder Bed Fusion of AlSi10Mg with Reduced Pore Formation

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 deep-penetration 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 P(L)/d(b) of the incident laser power P(L) and the beam diameter d(b) of the beam on the surface of the bead, and ranges between P(L)/d(b) = 2000 W/mm and P(L)/d(b) = 5200 W/mm, showing process efficiencies of about 7–8%. This optimum process window is centered around the range P(L)/d(b) = 3000–3500 W/mm, in which the process is characterized by KBM, which is an intermediate process mode between HCM and DPM. Processes with P(L)/d(b) < 2000 W/mm partially failed, and lead to balling and a lack of fusion, whereas processes with P(L)/d(b) > 5200 W/mm showed a process efficiency below 5% and pore ratios exceeding 10%.