Improvement of Mechanical Properties of Zn-Added Sn58Bi Alloy by Zn Segregation on the Sn-Bi Phase Boundaries During Thermal Aging

摘要

A comparative study of the microstructure and the mechanical properties of 0.5 and 1 wt.% zinc (Zn)-functionalized Sn58Bi alloys and eutectic Sn58Bi alloy was conducted both before and after solid-state thermal aging. Cross-sectional microstructure observation and tensile tests were performed on bulk solder alloys. The fracture surfaces were observed after the tensile tests. The results indicated that much finer microstructures were obtained in the Zn-added samples compared to the eutectic Sn58Bi before and after aging since the Sn–Bi phase boundary segregation of Zn occurred during aging, and the movement of the diffusion entities (Sn and Bi atoms) through the boundaries was obstructed. The fine microstructure was responsible for the ultimate tensile strength and elongation improvement obtained in the Zn-added samples.