Study On Optimization Of Micro-arc Oxidation Processing Of Aluminum Cast Alloy

In order to investigate the effect of substrate composition and electrolyte on micro-arc oxidation processing and formation of ceramic layers, surface of different aluminum alloys (LY12, ZL104, ZL108, YL112) was modified by micro-arc oxidation. During processing, the concentration and composition of electrolyte were adjusted to lower the current density and raise the ceramic layer growth velocity on aluminum cast alloy. Thus, the energy consumption of micro-arc oxidation was reduced through optimizing the composition of the electrolyte. The phase structure and distribution of the micro-arc oxidation ceramic layer, which were prepared on the aluminum cast alloy in the different electrolytes, were analyzed by the XRD. The microstructure of micro-arc oxidation ceramic layers was characterized by SEM. The result shows that the current density and the energy consumption can be lowered by adding sodium citrate and ammonium oxalate with appropriate content in the sodium silicate electrolyte system. XRD analysis shows that the ceramic layer is mainly composed ofγ-Al₂O₃, including large amount of SiO₂ metastable phase. Silicon exists in phosphoric acid salt electrolyte system with the form of SiO₂ and in the sodium silicate electrolyte system with the form of 3Al₂O₃-2SiO₂. A little Cu₂O and CuAl₄O₂ were found in the two electrolyte systems.