These investigations were carried out at 1823 K (1550 ☌) in argon atmosphere for times ranging between 15 minutes and 3 hours. For the liquid phase, the Modified Quasichemical Model in the Pair Approximation for short-range ordering was used.Ī sessile-drop study was carried out on Al2O3-10 pct C refractory substrates in contact with molten iron to investigate possible chemical reactions in the system and to determine the influence of carbon and the role, if any, played by the presence of molten iron that can act both as a reducing agent and as a metallic solvent. In this way, the data are rendered self-consistent, discrepancies among the data are identified, and extrapolations and interpolations can be performed. Optimization was performed to obtain the parameters of one set of model equations for the different solid and liquid phases to best reproduce all the experimental data simultaneously. The new vapor pressure of calcium over pure solid and liquid was used as a new reference to model the thermodynamic properties of the intermediate stoichiometric Ca−Si compounds together with other thermodynamic and phase diagram data found in the literature (liquidus temperatures, heat capacities, pressures of Ca, and heats of reaction). In a first step, the thermodynamic properties of Ca(g) were obtained from experimental vapor pressure data over pure Ca.
All available phase equilibria and thermodynamic data for the Ca−Si system were collected and critically evaluated.
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