Effect of MgO on Liquidus Temperatures in the ZnO-“FeO”-Al₂O₃-CaO-SiO₂-MgO System in Equilibrium with Metallic Iron

The phase equilibria in the ZnO-“FeO”-Al₂O₃-CaO-SiO₂-MgO system have been determined experimentally in equilibrium with metallic iron. Synthetic slags were equilibrated at a high temperature, quenched, and then the compositions of the phases in equilibrium were measured using electron probe X-ray microanalysis. Pseudoternary sections of the form ZnO-“FeO”-(Al₂O₃ + CaO + SiO₂) for CaO/SiO₂ = 0.71, (CaO + SiO₂)/Al₂O₃ = 5 and fixed MgO concentrations of 2, 4, and 6 wt pct have been constructed. Wustite (Fe²⁺,Mg,Zn)O and spinel (Fe²⁺,Mg,Zn)O·(Al,Fe³⁺)₂O₃ are the major primary phases in the temperature and composition ranges investigated. The liquidus temperatures are increased by 140 K in the wustite primary phase field and by 70 K in the spinel primary phase field with the addition of 6 wt pct MgO in the slag. The partitioning of MgO and ZnO between the solid and liquid phases has been discussed.