Elimination of droplet rebound off soluble substrate in metal droplet deposition

This letter presents a method and its mechanism of using Ag coating to inhibit rebound of Al droplets over soluble substrates. Experiments show that Ag coating can eliminate droplet rebound, which makes it possible to print complex parts with high-quality inner surface. Further investigation reveals that Ag coating suppresses the rebound of Al droplets through strong chemical interaction between liquid Al and Ag layer, which results in fast Ag dissolution in liquid Al and formation of a dendritic network of Al-Ag intermetallic compounds (IMCs) on their interface. XRD and EDS observation indicates that the IMCs caused by Ag atom diffusion and precipitation are mainly composed of Ag2Al intermetallics and α-Al solid solutions. It is found that the thickness of the IMCs layer increases as the substrate temperature is raised. The temperature increase of the substrate will slow down the droplet cooling process, which allows more thorough chemical reaction.