Microcalorimetry and thermochemistry of alloys

High temperature microcalorimetry is a very fruitful technique for increasing our knowledge of the thermochemistry of multicomponent alloys. As a good example, calorimetric results obtained for the Al + Bi + Ga system have been selected. Using a Calvet microcalorimeter and the indirect drop method, enthalpies of formation were measured over the entire concentration range between 725 and 1170 K and several points of the phase diagram were deduced from these calorimetric results. By means of a computer program, the Al + Bi + Ga equilibrium phase diagram was calculated and thus a thermodynamic description can be predicted. Making use of some simplifying hypotheses, the results indicate a satisfactory agreement between the experimental and the calculated liquid miscibility gap.