Investigation of layer-by-layer laser remelting to improve surface quality, microstructure, and mechanical properties of laser powder bed fused AlSi10Mg alloy

Abstract

Laser Powder Bed Fusion (LPBF) is an innovative additive manufacturing technology. But it is also limited by the defects and surface quality. In this work, the layer-by-layer laser remelting (LR) method is applied to LPBF AlSi10Mg to improve the surface quality and mechanical performance. To account for the physical mechanism of the laser remelting, a three-dimension multi-physics coupled transient model is established. The numerical results indicate that the molten pool during the LR process is significantly expanded. The larger molten pool plays a great role in removing the defects. Moreover, the temperature gradient and cooling rate are simultaneously increased during the LR process, which has a considerable impact on the microstructure transformation. The densification, surface quality, including roughness, wettability, and residual stress, microstructure, and mechanical property are investigated after LR treatment based on experiments. The experimental results show that after LR treatment, the densification can be up to 99.4%. The surface hydrophilicity is limited due to roughness reduction. The average grain size of top and side surface can be decreased by 6.74% and 28.79% due to the increasement of cooling rate. The average microhardness and ductility can be improved due to grain refinement and defect elimination.

Keywords

• Additive manufacturing
• Layer-by-layer laser remelting
• Molten pool
• Grain refinement