Effect of solidification condition and strain rate on tensile properties and fracture behavior of Sn-58Bi solder

The tensile property and fracture behavior of the Sn-58Bi lead free solder solidified in water, air and furnace, respectively, are studied at different strain rate of 0.001, 0.002, 0.004 s^–1. Results shown the eutectic structure of water cooling and air cooling Sn-58Bi solders is finer, in particular, the eutectic structure of air cooling solder is more uniform, while the eutectic structure of furnace cooling solder is coarse with serious microstructural segregation. The tensile strength of the solder becomes larger and the percentage elongation after fracture is smaller with increase of strain rate. Because of the accumulation of hard and brittle rich Bi which becomes from microstructural segregation in the Sn-58Bi solders, the tensile strength of furnace cooling solder is the maximum, however, its percentage elongation after fracture is the minimum, the fracture surface appears to be a typical brittle mode. The uniform eutectic structure can significantly improve the percentage elongation after fracture of the water cooling and air cooling Sn-58Bi solders, especially the percentage elongation after fracture of air cooling solder is maximum due to the best homogeneous eutectic organization, the fracture surface of air cooling solder is a brittle-ductility mixed fracture mode.