Aluminum Deoxidation Equilibrium in Molten Fe-Co Alloys

Abstract

Aluminum deoxidation equilibrium of molten Fe-Co alloy was experimentally measured using a chemical equilibrium method and numerically assessed using a sub-regular solution model based on Darken’s quadratic formalism and a Redlich-Kister type polynomial at 1873 K. It was found that the degree of oxygen content reduction by Al-deoxidation decreased with increasing cobalt concentration in the alloy, peaking at around 40 to 60 mass% Co, and then improved with further increase in cobalt concentration. The following binary interaction parameters between cobalt and aluminum were derived in this study:

⁰Ω_Co-Al = −387360 [J⁄mol], ¹Ω_Co-Al = 309420 [J⁄mol]

It was also found that the above binary interaction parameters can accurately determine Al-deoxidation equilibrium of pure liquid cobalt. Finally, the critical point at which Al₂O₃ and CoO∙Al₂O₃ coexist throughout the whole composition range of the alloy was also estimated from the experimental results in this study.