COMPUTER-ASSISTED ANALYSIS AND CALCULATION OF PHASE-DIAGRAMS OF THE FE-CR-O, FE-NI-O AND CR-NI-O SYSTEMS

Available thermodynamic and phase equilibrium data for the FeCrO, FeNiO and CrNiO systems are assessed and equations for the free energies of the phases as functions of composition and temperature are derived. With these mathematical expressions and with a computer program written for the purpose, phase diagram sections at constant temperature, or at constant log pO, or at constant Pco Pco or pH PH ratios can be calculated at all compositions and over a wide range of temperature and oxygen potential. The representation and analysis of the phase equilibria are greatly facilitated through the use of isothermal log PO-composition phase diagrams which are discussed in some detail. Structural models for the spinel phases are examined. © 1979.