Numerical Investigation on Molten Pool Dynamics During Multi-laser Array Powder Bed Fusion Process

摘要

Multi-laser powder bed fusion (MLPBF) has become the most promising technology for rapid manufacturing of large metal parts. As a branch of MLPBF, multi-laser array powder bed fusion (MLA-PBF) has gradually attracted the attention of the industry, because of its advantages such as significantly speeding up production efficiency and low technical implementation difficulty. However, there is currently a lack of simulation studies based on the mesoscopic scale to describe the dynamic behavior of the MLA-PBF molten pool. The MLA-PBF spreading powder process was calculated herein based on the open source DEM framework Yade, the MLA-PBF molten pool dynamics was described based on the open source CFD framework OpenFOAM, and a multi-laser heat source model for real-time tracking of changes in the metal-phase and gas-phase interface was proposed. Aiming at the single-line mode of MLA-PBF, it was found that the dual-laser forming with low-front and high-rear could be used to preheat and pre-sinter the metal particles that were about to enter the molten pool, which was beneficial to reduce the pore defect in the solidified track, and a moderate laser beam space should be used. Aiming at the multi-line mode of MLA-PBF, it could form a molten pool with a significantly larger width and length than in the case of a single-laser beam, which was beneficial to eliminate pore defect in the formed zone, obtain a flat solidified track surface, and improve forming efficiency. When the laser power was low or the laser beam space was large, a large number of pores were prone to appear in the formed zone. As the laser power increased or the laser beam space decreased, when the laser energy was sufficient to melt the metal particles located in the lower part of the powder bed, a smooth surface of the solidified track and fewer pore defect would be obtained. This paper is expected to provide theoretical support for deepening the application of MLA-PBF in metal additive manufacturing.