Effect of Sb and Zn Addition on the Microstructures and Tensile Properties of Sn-Bi-Based Alloys.

The tensile behavior of Sn-Bi-Cu and Sn-Bi-Ni alloys has been widely investigated. Reportedly, the addition of small amounts of a third element can refine the microstructures of the eutectic Sn-58mass% Bi solder and improve its ductility. However, the superplasticity mechanism of Sn-based alloys has not been clearly established. Therefore, in this study, the effects of Sb and Zn addition on the microstructures and tensile properties of Sn-Bi-based alloys were investigated. The alloys were subjected to tensile tests under various strain rates and temperatures. We found that Zn- and Sb-added Sn-Bi-based alloys demonstrated superplastic deformation at high temperatures and low strain rates. Sb addition significantly affected the elongation of the Sn-Bi-Sb alloys because the metal dissolves in both the primary Sn phase and the eutectic Sn-Bi matrix. The segregation of Zn and formation of needle-like Zn particles at the eutectic Sn-Bi phase boundary affected the superplastic deformation of the alloys. The deformation of the Sn-40Bi-based alloys at high temperatures and low strain rates led to dynamic recovery, dynamic recrystallization, and/or grain boundary slip because of the accumulation of voids.