Effect of thermal-fluidic transport on the temperature distribution and the melt pool in laser powder bed fusion of Ti6Al4V

Abstract

The thermal-fluidic transport affects the temperature distribution and melt pool size in laser powder bed fusion due to its large temperature gradient. A finite element model is established to predict the temperature and melt pool size with considering the thermal-fluidic transport effect. The enthalpy-porosity method is adopted to determine the solid-liquid interface with considering the momentum dissipation during the solidification of the melt pool. A parabolic optical penetration depth (POPD) volumetric heat source model is deduced based on the cylinder heat source model satisfying energy conservation. In the proposed model, the material properties are dependent on the temperature and the powder porosity. The proposed model is validated by comparing to published experimental data of melt pool size. Based on the validated finite element model, the thermal-fluidic transport effects on the temperature distribution and the melt pool are discussed. Results show that in terms of the melt pool width, the prediction accuracy of the surface heat source model is slightly higher than that of POPD volumetric heat source model. In terms of the melt pool depth, surface heat source model is appropriate for the low energy density, while POPD volumetric heat source model is suited for the medium energy density. The thermal-fluidic transport effect increases the melt pool width and length under the surface heat source model, and its effect on the melt pool depth is not obvious. While the thermal-fluidic transport effect decreases the melt pool length under POPD volumetric heat source model, and its effect of the melt pool width and depth is not significant.