AN INVESTIGATION OF PHASE-EQUILIBRIA OF THE BI-SB-SN SYSTEM

The liquidus surface and invariant reactions involving the liquid phase are calculated to determine the solidification behavior of Bi-Sb-Sn alloys. Only two U-type invariant reactions Liq. + Sb2Sn2 = SbSn + (Sn) at 517.9K and Liq. + SbSn = (Sn) + (Sb) at 411.8K are found. Thermodynamic calculation does not predict the presence of a ternary eutectic reaction in this system. The calculated solidification behavior of ternary alloys are found to be consistent with the experimental data as determined by differential scanning calorimetry. An isothermal section of the Bi-Sb-Sn system at 398K is also established. The equilibrium composition of the solid phases are determined by analytical electron microscopy. In contrast to an earlier report, the Bi-content in the SbSn phase is found to be about 5 wt.%.