PHASE EQUILIBRIA IN CU–AL–CR–O SYSTEM LIQUID METAL

Abstract

A thermodynamic analysis of phase equilibria in a Cu–Al–Cr–O system was performed. The study involved thermodynamic modeling of the liquidus surface of the Cu2O–Al2O3–Cr2O3 oxide phase diagram. To describe the thermodynamic activity of the molten oxide, an approximation of the sub-regular ionic solutions theory was used with the energy parameters determined in the modeling process. Melting characteristics of CuCrO2 were also evaluated during calculations. Calculation results were used to determine the coordinates of invariant equilibria points in the Cu2O–Al2O3–Cr2O3 ternary oxide system. The study also involved thermodynamic modeling of interactions in the Cu–Al–Cr–O system in the conditions of a copper-based metal melt. The temperature function of the reaction equilibrium constant was determined for the formation of solid CuCrO2 from the components of the Cu–Al–Cr–O molten metal system. The temperature function was obtained for the first order (Wagner’s) interaction parameter of Cr and O dissolved in liquid copper. The results of thermodynamic modeling for the Cu–Al–Cr–O system are represented as the surface of components solubility in metal, which allows us to relate the quantitative changes in the molten metal concentration to the qualitative changes in the composition of resulting reaction products. As a result of modeling, it was found that the given considerable concentrations of Al and Cr in the Cu–Al–Cr–O molten copper system form the |Al2O3, Cr2O3|ss solid solution particles as primary reaction products. The results of the study may be used to improve the chromium bronze smelting process.