Multi-material model for mesoscopic analysis of porosity evolution during laser powder-bed fusing TiNbTa powder mixture

Abstract

The three-dimension mesoscopic model for laser powder-bed fusion (LPBF) of multi-elements Ti25Nb10Ta alloy has been established by coupling the discrete element method and finite element method to study the powder flow behavior, thermodynamics within pool and porosity evolution. The influence of applied laser power on porosity evolution of titanium alloy has been investigated to further control the porosity defects during LPBF of ternary powder particles. The results reveal that a homogeneous distribution and spreading of ternary powder particles is obtained through decreasing the dimension of powder particles (Nb and Ta) with a high physical density to increase the adhesive force to neighbouring ones. Due to the application of a low laser power, the molten liquid with a high viscosity and the Nb powder particles without dissolution caused by a low energy input result in a limited spreading ability of liquid, thereby leading to the formation of porosity defects. However, as the laser power exceeds 280 W, the high temperature decreases the viscosity of liquid and meanwhile facilitates the dissolution and diffusion of Nb powder particles, which leads to the disturbance of liquid and hence strengths the spreading ability of liquid. In this regime, the porosity defects of ultimate part are nearly eliminated.