Effect of Al2O3 and Cr2O3 on Liquidus Temperatures in the Cristobalite and Tridymite Primary Phase Fields of the MgO-"FeO"-SiO2 System in Equilibrium with Metallic Iron

The effects of alumina and chromite impurities on the liquidus temperatures in the cristobalite/tridymite (SiO2) primary phase fields in the MgO-“FeO”-SiO2 system in equilibrium with metallic iron have been investigated experimentally. Using high temperature equilibration and quenching followed by electron probe X-ray microanalysis (EPMA), liquidus isotherms have been determined in the temperatures range 1673 to 1898 K. The results are presented in the form of pseudo-ternary sections of the MgO-“FeO”-SiO2 system at 2, 3 and 5 wt% Al2O3, 2 wt% Cr2O3, and 2 wt% Cr2O3+2 wt% Al2O3. The study enables the liquidus to be described for a range of SiO2/MgO and MgO/FeO ratios. It was found that liquidus temperatures in the cristobalite and tridymite primary phase fields, decrease significantly with the addition of Al2O3 and Cr2O3.