Multiphysics modeling of flow characteristics and particulate migration behavior of titanium matrix composites by laser directed energy deposition

Incorporating ceramic particles into titanium alloys during the laser directed energy deposition (DED) process has been shown to significantly enhance the mechanical properties. However, particulate migration behavior within the melt pool and the influence of ceramic particles on the flow characteristics remain unclear. Here, we developed a model for multiphysics simulations to investigate the interaction mechanisms between molten pool and unmelted ceramic particles of TiC/Ti6Al4V titanium matrix composites. This model employs a coupling of computational fluid dynamics and the discrete element method (CFD–DEM). The effectiveness of our model was verified by comparing the transverse sections and high-speed photographs of the molten pool by conducting DED experiments. The simulation findings suggest that the concentration of TiC reinforcing particles greatly influences both the temperature distributions and velocity fields. Increasing the content of TiC resulted in faster absorption of laser energy, ultimately leading to an increase in peak temperature. Additionally, the augmentation of TiC content resulted in elevated molten viscosity, which impeded Marangoni flow. Meanwhile, the migration of TiC particles is mainly influenced by Marangoni convection. TiC ceramic particles were predominantly distributed within the upper and lower regions of the deposition layer, and the particle distribution is closely related to the position of particles entering the molten pool. These findings offer valuable insights into the multiphase dynamics of metal matrix composites during the additive manufacturing process employing DED technology.