Phase equilibria and solidification of ternary Sn–Bi–Ag alloys

The Sn–Bi–Ag system is an important ternary system for electronic products, and this study investigates its phase equilibria and solidification behavior. Sn–Bi–Ag alloys were prepared and equilibrated at 210 °C and 400 °C, and their equilibrium phases were determined. Thermodynamic descriptions of the ternary Sn–Bi–Ag system are developed from the results determined in this study and those available in the literature. Isothermal sections and liquidus projection are then calculated using the determined Sn–Bi–Ag thermodynamic descriptions. Solidified microstructures of three Sn–Bi–Ag alloys are examined. It is found that the solidification paths cut through the monovariant line, instead of following the monovariant line as expected.