2013 Volume 53 Issue 3 Pages 434-440
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 1500 ppm Al at 1823 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 Al2O3 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 electro-probe microscope analyzer (EPMA) analysis.