Investigation on the decomposition of Al₂O₃ using an electrochemical method

When the chemical potential of dissolved oxygen in a Fe-Al-O alloy is above the super-saturation level, Al₂O₃ inclusions will be precipitated; electrochemical reaction analysis can provide explanations of the kinetic and thermodynamic mechanisms in the formation and decomposition of Al₂O₃. In this study, an external potential was supplied to the electrochemical system consisting of electrodes and a MgO-stabilized ZrO₂ electrolyte in order to control interfacial oxygen levels and oxide inclusions in Fe-Al-O alloys of 30, 70, 170, 560 and 1 500 ppm Al at 1 823 K. Critical levels of interfacial oxygen concentration were kinematically determined by concentration overvoltage using the Tafel relationship and the Nernst equation. From these experiments, the formation of Al₂O ₃ requires interfacial and crystallization energy. Also energy for decomposition of Al₂O₃ should be needed the energy to break Al-O bonding and to dissociate into the Fe melt. The results of the formation and decomposition of Al₂O₃ at the interface between the Fe-Al-O alloy and solid electrolyte are indicated in scanning electron microscope (SEM) images and through electroprobe microscope analyzer (EPMA) analysis.