Enthalpies of mixing of liquid Bi–Cu and Bi–Cu–Sn alloys relevant for lead-free soldering

Partial and integral enthalpies of mixing of liquid ternary Bi–Cu–Sn alloys at 800 °C were determined along nine sections in a large composition range. Additionally, binary alloys of the constituent binary system Bi–Cu were investigated at 800 and 1000 °C. Measurements were carried out using a Calvet-type microcalorimeter and a drop calorimetric technique. The binary data were evaluated by means of a standard Redlich–Kister polynomial fit whereas ternary data were fitted on the basis of an extended Redlich–Kister–Muggianu model for substitutional solutions.