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

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, KMg, 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 aMg vs. aO, aMg vs. aAl 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.