Effect of nano Al2O3 additions on the interfacial behavior and mechanical properties of eutectic Sn-9Zn solder on low temperature wetting and soldering of 6061 aluminum alloys

In this study, an addition of Al2O3 nano-particles with a content in the range of 0-1 wt% to Sn-9Zn eutectic solder, were examined in order to understand the effects of Al2O3 additions as the particulate reinforcement to the melting point, wettability, microstructure, interface morphology and hardness as well as mechanical properties of soldering 6061 aluminum alloys. Here, an approach to prepare a composite solder by adding Al2O3 nano-particles to the molten Sn-9Zn solder alloy was developed. In the soldered joint using Sn-9Zn solders, there is a solution layer of Al8ZnSn4 located at the interface. Due to the addition of Al2O3 nano-particles, the scallop-shaped solid solution layer was changed into a flat layer, and its thickness was reduced. In the microstructure of the composite solder containing 1 wt% Al2O3 nano-particles, the fine acicular-shaped Sn-Zn eutectic structure and Al2O3 nano-particles were found to be distributed in the β-Sn matrix. These changes in the interfaces and the microstructure, leading to the improvement of wettability, mechanical properties and hardness of the composite solder.