Parametric analysis of thermal behavior during selective laser melting additive manufacturing of aluminum alloy powder

摘要

Simulation of temperature fields during selective laser melting (SLM) additive manufacturing of AlSilOMg powder was performed using the finite element method (FEM). The effects of laser power and scan speed on the SLM thermal behavior were investigated. It showed that the cooling rate of the molten pool elevated slightly from 2.13 × 10~6 ℃/s to 2.97 × 10~6 ℃/s as the laser power increased from 150W to 300W, but it enhanced significantly from 1.25 × 10~6℃/s to 6.17 × 10~6℃/s as the scan speed increased from 100 mm/s to 400 mm/s. The combination of a low laser power (200 W) and a high scan speed (400 mm/s) yielded a low temperature (1059 ℃) and an extremely short liquid lifetime (0.19 ms), resulting in the poor wettability and occurrence of micropores in SLM-produced parts. The temperature gradient along the depth direction of the molten pool increased considerably from 10.6 ℃/μm to 21.7 ℃/μm as the laser power elevated from 150 W to 300 W, while it decreased slightly from 14.9 ℃/μm to 13.5 ℃/μm as the scan speed increased from 100 mm/s to 400 mm/s. The proper molten pool width (111.4 μm) and depth (67.5 μm) were obtained for a successful SLM process using the laser power of 250 W and scan speed of 200 mm/s. SLM of AlSi10Mg powder was also experimentally performed using different laser processing conditions and the microstructures of the SLM-fabricated samples were investigated to verify the reliability of the physical model. A sound metallurgical bonding between the neighboring fully dense layers was achieved at laser power of 250 W and scan speed of 200 mm/s, due to the larger molten pool depth (67.5 μm) as relative to the layer thickness (50 μm).