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The effects of addition of small amounts of copper (Cu) and indium (In) on the microstructure and thermal and mechanical properties of Sn-Zn eutectic alloy have been investigated. Cu and In were added in varying amounts to Sn-14.9 at.%Zn alloy by replacing an equal amount of Sn. Addition of Cu changed the eutectic composition, leading to the appearance of primary phases followed by the formation of intermetallic compounds (IMC) CuZn₅ and Cu₅Zn₈. However, addition of indium (In) did not lead to formation of any new IMCs. With addition of Cu or In to the binary eutectic, the eutectic microstructure coarsened (the eutectic spacing increased). Addition of 1.919 at.% indium decreased the Sn-Zn eutectic temperature from 198.8°C to 192.0°C. On the other hand, addition of Cu did not affect the eutectic temperature as much as In addition did. The mushy (or pasty) range (the temperature range between the …