Establishing Aluminum-Oxygen (Al-O) Equilibria in Liquid Iron at 1873 K: An Experimental Study and Thermodynamic Analysis

Aluminium-oxygen (Al-O) equilibrium was established at 1873 K over a range of aluminium concentrations, with a primary focus on higher aluminium contents. The experiments were conducted in a purified, deoxidized argon atmosphere, where Fe-Al alloy was melted in an alumina crucible and equilibrated for two hours at 1873 K. The measurement of actual equilibrium dissolved oxygen content has always been a challenge. Therefore, to distinguish between total and dissolved oxygen content, two advanced techniques were employed: (i) a two-stage heating method using inert gas fusion absorptiometry, and (ii) Scanning Electron Microscopy-Automated Inclusion Analysis (SEM–AIA). The Al–O equilibrium was separately determined for both total and dissolved oxygen contents. Thermodynamic analysis was performed using higher-order interaction parameter formalisms, namely, the Wagner Interaction Parameter Formalism (WIPF) truncated at the second order, Darken’s quadratic formalism, and the newly proposed formalism by the same authors, Cubic formalism. Among these, the Cubic formalism showed better agreement with the experimental data.

Keywords: Al-O equilibria, Dissolved and Total oxygen, Cubic formalism.