Dispersion of reinforcing micro-particles in the powder bed fusion additive manufacturing of metal matrix composites

Abstract

Understanding the complex multi-phase interactions are vital for defects reduction in additive manufacturing (AM) of metal matrix composites. In this study, we propose a high-fidelity model to reveal the dynamics of molten pool and reinforcing solid particles during the AM process, using the resolved Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) with bi-directional momentum and energy exchange. Our model is validated against the electron beam melting (EBM) experiments of tungsten-copper composites fabricated with elemental powder blends. The results demonstrate that the interface effect, including the dynamic wetting phenomena and Laplace pressure, play significant roles in the dynamics of reinforcing solid particles. On the other hand, the existence of reinforcing solid particles in the molten pool changes the molten pool size and alters the flow field during the melting process. Although the interface effect causes tungsten particle agglomeration at single track surface, the layer-wise deposition scheme with proper layer thickness eliminates the cluster and promotes the uniform tungsten distribution in the densified bulk sample, which shows the capability of AM to achieve spontaneous dispersion of reinforcing solid particles in the metal matrix. This work provides unprecedented details about the multi-phase dynamics in metal matrix composite AM process.