Abstract
The constitution of Al and O at 1873 K at the coexisting point, at which the Fe-Al-O system was in equilibrium with both of FeO·Al2O3 and α-Al2O3, was investigated, and the measured Al and O contents were found to be 0.072 mass% O and 0.0018 mass% Al. The O content of this point agrees well with other measured values. The Al content of this point is two orders of magnitude larger than the activity of Al but agrees fairly well with the Al content predicted by an associated solution model and that measured by Novokhatskiy et al. This result reveals that the equilibrium curve (E.C.), which indicates the Al and O contents in liquid Fe in equilibrium with α-Al2O3, is a concave curve in the low Al region that extends to the coexisting point. However, the E.C. calculated using the interaction parameters and deoxidation constant K is almost a straight line. This discrepancy indicates that the use of the interaction parameters reported for this system is probably inappropriate in the concave E.C. region. The interaction parameters and thermodynamics of this system should be reexamined.
