Deoxidation Equilibria among Mg, Al and O in Liquid Iron in the Presence of MgO·Al₂O₃ Spinel

Abstract

The deoxidation equilibria among Mg, Al and O in liquid iron in the presence of MgO·Al₂O₃ spinel was studied at 1 873 K by adding Al and Mg alloys into liquid iron in MgO and Al₂O₃ crucibles. From the experimental results, the equilibrium constant, K_Mg, for the reaction, MgO (s)=Mg+O, and the first- and secondorder interaction parameters including cross-product terms between Mg and O have been determined. Using these thermodynamic parameters, the relations between a_Mg vs. a_O, a_Mg vs. a_Al in liquid iron could be well represented with respective oxide activities in MgO·Al₂O₃ spinel. A stability diagram for MgO, MgO·Al₂O₃ and Al₂O₃ phases was constructed at 1 873 K as a function of dissolved Mg, Al and O contents in liquid iron to examine the condition for the formation of MgO·Al₂O₃ spinel during the deoxidation process.