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 AI 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 second-order 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. aA 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.