Tailoring surface quality through mass and momentum transfer modeling using a volume of fluid method in selective laser melting of TiC/AlSi10Mg powder

Abstract

A selective laser melting (SLM) physical model of coupled radiation transfer and thermal diffusion is proposed, which provides a local temperature field. A strong difference in thermal conductivity between the powder bed and dense material is taken into account. Both thermo-capillary force and recoil pressure induced by the material evaporation, which are the major driving forces for the melt flow, are incorporated in the formulation. The effect of the laser energy input per unit length (LEPUL) on the temperature distribution, melt pool dynamics, surface tension and resultant surface morphology has been investigated. It shows that the surface tension plays a crucial role in the formation of the terminally solidified surface morphology of the SLM-processed part. The higher surface tension of the lower temperature metal near the edge of the melt pool and the thermal-capillary force induced by the surface temperature gradient tend to pull the molten metal away from the center of the melt pool. For a relatively high LEPUL of 750J/m, the molten material in the center of the melt pool has a tendency to flow towards the rear part, resulting in the stack of molten material and the attendant formation of a poor surface quality. For an optimized processing condition, LEPUL=500J/m, a complete spreading of the molten material driven by the surface tension is obtained, leading to the formation of a fine and flat melt pool surface. The surface quality and morphology are experimentally acquired, which are in a good agreement with the results predicted by simulation.