Melt Pool Analysis and Mesoscale Simulation of Laser Powder Bed Fusion Process (L-PBF) with Ti-6Al-4V Powder Particles

The laser powder bed fusion (L-PBF) process is accompanied by rapid melting and solidification that results in intense thermocapillary convection within the melt pool. Open-source particle simulation software was utilized to generate a single layer of spherical powder particles of variable diameter. Considering the importance of particle size and the particle size distribution (PSD) in the L-PBF process, three distinct categories of PSD were generated with identical settings. A three-dimensional (3D) thermofluid model was developed in this study, incorporating the generated layer of powder particles of nonuniform size over a thick substrate. A moving volumetric heat source was applied to melt a single track in the powder layer using a user-defined function in FLUENT software. Temperature-dependent material properties including variable surface tension were considered in the computation. The numerical model was used to simulate Ti-6Al-4V powder particles to observe the melt pool flow dynamics. Presence of particles of smaller diameter in the powder mix supported consistent and continuous melt pool flow, while any kind of void enhanced fluid convection in the downward direction, causing a temporal increase in melt pool depth.