Thermodynamic Simulation of Phase Equilibria with Oxide Systems Containing Rare-Earth Metals. Report 1. Phase Diagrams of Oxide Systems with La2O3

Abstract

State diagrams of a number of oxide systems with La2O3 as an independent component were defined on the basis of the literature and the theory of subregular solution. Binary and ternary oxide diagrams conjugated with the domain of existence of metal dis-melts were considered: FeO–La2O3, Al2O3–La2O3, CaO–La2O3, MgO–La2O3, Cr2O3–La2O3, FeO–Cr2O3–La2O3, FeO–Al2O3–La2O3, FeO–CaO–La2O3, FeO–MgO–La2O3. Energy parameters of the theory of subregular solutions applied to the oxide melts of the described above systems were defined. Heats and entropy of fusion for the aluminates and lanthanum chromites were calculated. The constants for the power-equilibrium processes for the formation of compounds of the components of the oxide melt were estimated. The coordinates of the lines and the liquidus surface for the phase diagrams of FeO–La2O3, FeO–Cr2O3–La2O3, FeO–Al2O3–La2O3, FeO–CaO–La2O3, FeO–MgO–La2O3 were defined. Data for these diagrams were obtained for the first time.

On the data obtained the solubility surface (SSCM) of lanthanum in liquid oxygen-containing iron was constructed. The SSCM shows that lanthanum deoxidizing ability is somewhat higher than an aluminum one.

The thermodynamic data obtained can be used to get information about the SSCM structure for the conditions of complex deoxidation of steel by highly active elements in combination with lanthanum.