Microstructural characteristics and vibration fracture properties of Sn-Ag-Cu-TM (TM=Co, Ni, and Zn) alloys

This study investigated microstructure thermal behavior, and mechanical properties of Sn-3.3Ag-0.5Cu alloys (SAC) with the addition of transition metals (TM, Ni, Co, and Zn). Results show that alloying with TM elements was able to reduce the degree of undercooling and strengthen SAC alloys. Among these elements, only Zn can raise the ductility. CoSn and Cu-Ni-Sn intermetallics appeared, respectively, in the Co-containing and Ni-containing samples while coarse Sn dendrites and a large area of eutectic phases could be observed in the specimens with Zn. These microstructural changes led to an inferior vibration fracture resistance under resonant vibration with a constant pull force.