Experimental and thermodynamic modeling study of phase equilibria in the Al2O3-CrO-Cr2O3-SiO2 system

Experimental investigation and thermodynamic modeling of the phase equilibria in the Al 2 O 3 -CrO-Cr 2 O 3 -SiO 2 system has been undertaken to characterize the behavior of alumina-chromia refractories and their reactions with silicate slags at variable oxygen partial pressures. Phase equilibria data at 1290-1730 °C were obtained through equilibration of synthetic mixtures in sealed silica ampoules, Al 2 O 3 crucibles, on Ir wires, Pt-Ir or Re foils, followed by rapid quenching, and electron probe X-ray microanalysis. Phase equilibria and liquidus isotherms of the Al 2 O 3 -“CrO”-SiO 2 system in equilibrium with Cr-Si metal and Al 2 O 3 -CrO-Cr 2 O 3 -SiO 2 in equilibrium with gas of fixed p(O 2 ) – CO-CO 2 mixtures or air – were measured in the tridymite/cristobalite SiO 2 , corundum (Al,Cr) 2 O 3 , mullite (Al,Cr) 6+x Si 2-x O 13-0.5x and spinel (Al,Cr) 3 O 4+x phase fields. New data were used for developing a self-consistent set of thermodynamic parameters for all phases to describe the behavior of Al-Cr refractories in industrial primary nonferrous smelting and recycling slags.