EXPERIMENTAL-DETERMINATION AND COMPUTATION OF PHASE-DIAGRAMS FROM THEIR THERMODYNAMIC FUNCTIONS

Most methods of determination of phase diagrams are based on the observation of the variation versus temperature, of a given property of alloys of defined compositions. These methods, such as thermal analysis of e.m.f. determination, enable by direct measurements the vertical crossing (in a parallel direction to the temperature axis] of phase boundaries. The aim of this paper is to describe the method by which partial and integral enthalpies of formation of allays vs. molar fraction are measured at a constant temperature; the phase boundaries are then obtained by the horizontal crossing of the phase diagram. In this paper, the systems concerned are mainly metal-semimetal alloys. In addition to the experimental phase diagram, the enthalpies of formation of the different phases of the system are simultaneously obtained with respect to composition and temperature. Combined with the values of the free enthalpies of formation obtained by a potential method, these results allow the computation of equilibrium diagrams. Lastly, the comparison of computed and experimental results enables the checking of the consistency of all the experimental informations. © 1979.