Oxide Matrix Composite by Directional Oxidation of a Commercial Aluminum‐Magnesium Alloy

Oxidation rates of a commercial Al‐Mg alloy, Al‐5083, were investigated to understand the synthesis of an oxide‐based composite. In some experiments, the oxide layer was grown with several platinum wires embedded in the matrix to facilitate transport of electrons. The oxidation rate was not controlled by the rate of transport of the electrons and positive holes through the ceramic oxide layer. In the initial phase of the composite growth, an incubation period was observed due to formation of MgO on the alloy surface. At 1273 K or higher, the incubation period was followed by a period of sustained oxidation after MgO was converted to a spinel layer. It is demonstrated that, after the initial incubation period, the rate of oxidation is influenced by the rate of transport of ions through the oxidematrix composite.