Dynamics of molten droplet/pool fusion in additive manufacturing

This mini-review first clarifies a very basic process of the fusion-solidification between molten droplet/pool in additive manufacturing (AM) from its technical principle and various experimental observations on the material defects, such as porosity, separation and splashing, erosion and surface concave, and balling effects. Then, the dynamical similarities between the droplet/pool coalescence at normal temperature and the molten droplet/pool fusion at high temperature are illustrated to reveal the fusion-solidification-induced mechanism of material defects, where the droplet/pool fusion phenomena in the early stage have significant influences on the solidification of molten pool in the late stage for the AM process. Finally, some thoughts on the modeling of the fusion-solidification process between molten droplet/pool are stated by referring to the droplet-pool dynamics, which is benefit to the Eulerian-Lagrangian simulation on the prediction of AM process, so as to change the traditional trial-and-error methodology and improve the manufacturing technique.