Functionally graded reaction layers produced by directed metal oxidation process

The directed metal oxidation process has been attempted for the fabrication of a functionally graded layer on the Al–Mg/Al2O3 powder compact. It was found that the reaction of the Al–Mg/Al203 at 900°C under air atmosphere leads to the formation of reaction layers with varying ceramic phase contents. Two different types of reaction layers were observed, depending on the Mg contents: ceramic/channel/composite or channel/ceramic/channel/composite arrangements from the sample surface. The microstructural development of the reaction layers at various reaction stages was investigated and the mechanism of the reaction layers was discussed on the basis of MgO phase formation on the surface of the reaction layer.