Mesoscopic simulation of heat transfer and fluid flow in laser powder bed additive manufacturing

Laser-powder bed fusion (L-PBF) additive manufacturing involves complex physics such as heat transfer and molten metal flow, which have a significant influence on the final build quality. In this study, transport phenomena based modeling is used to provide a quantitative understanding of complex molten pool transients. In particular, a three dimensional (3D), transient numerical model is developed for L-PBF additive manufacturing by solving the governing partial differential equations of mass, momentum and energy conservation. The individual powder particles are resolved using the volume of fluid method (VOF) method with a fine mesh size of 3 μm (thus at meso-scale). The powder particle arrangement including particle size distribution and packing density are taken into account in placement of individual particles calculated using discrete element method. Moreover, the model considers Marangoni shear stress, an important driving force for molten metal flow. The numerical model is used to quantitatively study the effect of laser power, scanning speed, and powder size distribution on the bead geometry and formation of balling defect.