Chapter 11 - Thermal behavior of molten pool and its heat and mass transfer mechanisms during laser powder bed fusion additive manufacturing of metallic materials

Abstract

A mesoscopic model was established to investigate the thermodynamic mechanisms, heat/mass transfer phenomena, and densification behavior of metallic materials during laser powder bed fusion (LPBF) of aluminum-based composites using a finite volume method The influence of the applied laser linear energy density (LED) and different protective atmospheres on heat and mass transfer, molten pool dimensions, particle rearrangement, and resultant densification behavior in the molten pool of LPBF-processed metallic materials was discussed. It showed that the Marangoni convection became more vigorous with an increase of LED, playing a crucial role in intensifying the convective heat transfer, changing the molten pool geometry, enhancing the Marangoni force, and lowering the friction force, which was beneficial to the sufficient rearrangement of reinforcing particles. The temperature of laser-powder interaction zone, the molten pool dimensions, and liquid lifetime had a positive correlation with an increase in laser power or a decrease in scan speed. The motion direction of evaporation material driven by different protective atmospheres played a crucial role in the formation of the terminally solidified surface morphology of the LPBF-processed parts.