Effects of Ti addition on the microstructure, mechanical properties and electrical resistivity of eutectic Sn58Bi alloy

Abstract Titanium (Ti)-added tin-58 wt% bismuth (Sn58Bi) solder alloys were synthesized in this study. The microstructural evolution and mechanical property change of the eutectic Sn58Bi and Ti added Sn58Bi alloys were studied before and after thermal aging. Ti added Sn58Bi alloys exhibit a considerably refined microstructure compared with the eutectic Sn58Bi alloy because of the presence of the Ti 2 Sn 3 and Ti 6 Sn 5 intermetallic compounds (IMCs). The formation history of these Ti-Sn IMCs was studied based on a thermodynamic calculation. After thermal aging, the yield strength (YS) and ultimate tensile strength (UTS) of the eutectic Sn58Bi decreased, while the Ti added Sn58Bi alloys maintained the highest YS and UTS. Notably, the superior elongation of 0.5 wt% Ti added sample compared with that of the eutectic Sn58Bi alloy was obtained after 1008 h aging. The fracture morphology of the Ti added Sn58Bi alloys almost unchanged during aging due to the stable microstructure. In addition, the electrical resistivities of the eutectic Sn58Bi were tested, while the resistivities decreased in the Ti added Sn58Bi alloys at room temperature.