Effects of small additions of Ag, Al, and Ga on the structure and properties of the Sn–9Zn eutectic alloy

The effects of a third elements, i.e., Ag, Al, and Ga, on melting temperature, microstructures, and mechanical properties of the Sn–9Zn lead-free solders were investigated. The results indicate that Ga is uniformly distributed in the Sn-matrix, Al is detected in the grain boundaries and Zn-rich phases, and Ag combines with Zn to form an Ag–Zn compound. The adding of 0.5 wt% Ag, results in decreasing the UTS and ductility. By the addition of Al the UTS and elongation of the Sn–9Zn–0.45Al alloy can be decreased due to the Al element precipitated in the grain boundaries. The Sn–9Zn–0.5Ga alloys have very good UTS and elongation, which are better than both those of the Sn–9Zn–0.5Ag and Sn–9Zn–0.45Al alloys.