Thermal-fluid modeling and simulation of Ti-6Al-4V alloy filaments during shaping in the hot-end of material extrusion additive manufacturing

Continuous progress in material extrusion additive manufacturing is motivated by the need to produce functional parts at a low cost for medical, aerospace, and automotive applications. A significant innovation is impregnating a polymeric melt with metal powder (particle) to produce a filament that will be 3D printed using a low-cost desktop printer. The presence of metal particles affects the complex flow dynamic and temperature profile during processing through the hot-end of the 3D nozzle. The current study employs numerical simulation to analyze the effect of powder content on the outlet flow field during the melting of polymer-filled metal filament material extrusion additive manufacturing. Titanium 64-5 filament was experimentally measured to obtain thermophysical properties and another Titanium 64-5 filament thermophysical properties were empirically determined. Each filament was simulated using a finite element method to obtain temperature, viscosity, and shear rate data. A detailed discussion of the implementation of the thermal-fluid model was presented. The results obtained indicate that the two types of filaments' sensitivity to the feeding rates differ at a certain region of the extrusion regime. Also, further simulation was performed to investigate the response of the flow fields with the powder contents. The temperature and viscosity results obtained at the nozzle outlet indicate that at a high powder content, the printing of the polymer-filled metal filament can be performed at a high extrusion rate with possible extrudate shape stability. The thermal-fluid model and simulation can be used for selecting process parameters for any new binder-metal particle formulation.