The micro-arc oxidation (MAO) behaviors of in-situ TiB2/A201 composite

The Micro-arc oxidation (MAO) treatment on the in-situ TiB2/A201 composites was performed using the aluminate-based electrolyte, and the corresponding MAO behavior was discussed in this work. In connection with the film thickness-time curve, the voltage-time for the MAO process on the TiB2/A201 composite can be divided into two periods, namely the initial period (Stage I and II) and linear growth period (Stage III and IV). The phase and morphologies evolutions of the composite experienced these stages have been characterized by X-Ray diffraction, scanning electron microscopy and Micro-Raman spectroscopy. It is found the TiB2 particles have played a dual role in the MAO process. Firstly, the external current can leak through conductive TiB2 particles in the initial period. However, this leaking way has been quickly cut off by the oxidation of TiB2 to TiO2. Secondly, the TiB2 particles beneath the metal-oxide interface can impede MAO film from growing inward. Nevertheless, these TiB2 particles should be oxidized and then melted gradually, and finally dissolved into the oxide film.