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The binary aluminum-calcium phase equilibria were investigated using X-ray diffraction methods, metallography, energy-dispersive X-ray and differential thermal analyses, and the diffusion couple technique. The complete phase diagram has been determined. Two new binary compounds AlCa and Al3Ca8were found in addition to the established Al4Ca and Al2Ca phases. The crystal structure of Al3Ca8compound was determined by X-ray powder diffraction methods.

Drop solution calorimetry was performed to determine the enthalpies of formation of the binary Al2Ca and Al3Ca8phases and the partial enthalpy of mixing at infinite dilution of calcium in liquid aluminum. A consistent thermodynamic model of the Al–Ca system was constructed for the four stoichiometric compounds Al4Ca, Al2Ca, AlCa and Al3Ca8and for the liquid phase with a sub-subregular solution model. Optimization of the thermodynamic parameters using the Calphad method was done by incorporating all available experimental data on phase equilibria, enthalpies of formation and mixing and the activity coefficients in the liquid. A consistent description of the phase diagram and thermodynamic properties is presented which is well supported by the experimental data. The Ca-rich part of the phase diagram differs substantially from previous reports, mainly because of the two newly discovered phases AlCa and Al3Ca8.

The major tools used in applying computational thermodynamics to various problems in materials science are briefly presented and several practical examples are given as illustrations. Solutions to industrial problems, pertaining to the processing of and microstructure development in several different materials, are shown with answers given in graphical form. Solutions to kinetic problems linked with diffusion are also treated. The last section is devoted to the problem of interfacing between thermodynamic computations and applications oriented software.

The binary Al–Gd and the ternary Al–Gd–Mg systems were calculated using the Calphad method. It is demonstrated that previous interpretation of ternary liquidus temperatures below 700 °C must be related to other phase equilibria. The actual ternary liquidus temperatures are much higher, up to some 600 °C above the previous interpretation in literature. They are widely governed by the high-melting compounds Al2Gd and Al3Gd with liquidus surfaces stretching far into the ternary system. A small number of key experiments in this work confirmed the calculated liquidus temperature and the phase relations. The available experimental data in literature fit excellently with the calculation in the binary Al–Gd system. In the ternary Al–Gd–Mg system, which is shown in several sections of the phase diagram, a good agreement can be observed too, considering the necessary reinterpretation of the liquidus temperatures suggested by Rokhlin et al. Ternary solubilities were not found experimentally. The ternary compound Al4GdMg (τ) forms in a ternary peritectic reaction at 761 °C.