Experimental investigation and thermodynamic calculation of the Co–Sn–Bi ternary system

Phase relations of the Co–Sn–Bi ternary system have been studied experimentally for the whole composition range at 250 and 450 °C by means of scanning electron microscopy (SEM) coupled with wave dispersive spectrometer (WDS) and x-ray diffraction (XRD). Five three-phase regions have been confirmed in this system at 250 °C, and three three-phase regions exist in 450 °C. No ternary compound can be observed at these two temperatures. Moreover, Bi has almost no solubility in the binary compounds αCo3Sn2, CoSn, CoSn2 and CoSn3. The primary solidification phases were also distinguished. Based on the experimental results, the thermodynamic calculations for Co–Bi and Co–Sn–Bi system were conducted by using the CALPHAD technique. A set of self-consistent thermodynamic parameters for the Co–Sn–Bi ternary system was obtained, and the experiment results are in good agreement with the calculated results.