Microstructure and mechanical properties of Sn-9Zn-xAl and Sn-9Zn-xCu lead-free solder alloys

This study investigates microstructures and mechanical properties of the alloys obtained by adding Cu (0.7 % and 0.9 %) and Al (0.7 % and 0.9 %) to lead-free Sn-9Zn eutectic soldering alloy produced by investment casting method. The results show that Cu₅Zn₈ phase has formed in the structure of Cu added alloys and the Al₂O₃ phase has formed due to addition of Al. It was found that small and round-shaped Al₂O₃ phase increased the tensile strength of the new alloy compared to the eutectic alloy. In addition, it was observed that the microhardness of Cu added alloys was lower than that of Sn-9Zn eutectic alloy, but the microhardness of alloys containing Al was higher compared to the other eutectic Sn-9Zn alloy.