Setup and Experiment for the Fusion of Molten and Solidified Micro-droplets in a Simulated Micro-gravity Environment

Uniform droplet-based manufacturing is promising in on-orbit metal additive manufacturing due to its advantages of no requiring specially prepared raw materials and delicate energy beam sources in printing process. However, the feasibility of the fusion among micro metal droplets in a micro-gravity environment ($\mu$G-MDF) should be first verified. To address this issue, a novel uniform droplets fusion setup was designed and established to test the fusion between uniform molten and solidified tin-lead droplets in free falling process. The fusion process was successfully recorded and droplet samples fused under simulated micro-gravity were obtained. The obtained samples demonstrated that the spherical droplets can be formed after impact and fusion. The morphology of the fused droplets was neat, illustrating that droplets can withstand larger collision speeds without splashing. A good fusion situation between molten and solidified droplets was achieved, laying the foundation for conducting uniform aluminum micro-droplets fusion experiments in the drop tube.