Thermodynamic properties and phase equilibria of Sn–Bi–Zn ternary alloys

Abstract

Sn–Bi–Zn alloys are promising Pb-free solders. In this study, their thermodynamic properties and phase equilibrium relationships are determined both experimentally and theoretically. Various Sn–Bi–Zn alloys are prepared, equilibrated at 160 °C, and the equilibrium phases are examined. No ternary compound is found. The isothermal section at 160 °C is proposed based on the ternary phase equilibria data and the phase diagrams of the constituent binary systems. Activities of Sn and Zn of Sn–Zn, Sn–Bi and Sn–Bi–Zn alloys are determined using the electromotive force method. The thermodynamic properties and phase equilibria information determined in this study and those available in the literatures are evaluated. The thermodynamic models of Sn–Bi–Zn phases are assessed, and the isothermal sections, isoplethal section, and liquidus projection of the Sn–Bi–Zn system are calculated using the calculation of phase diagram (CALPHAD) approach. The calculated thermodynamic properties and phase diagrams are consistent with the experimental values.