Abstract: Four kinds of Al-Si alloys containing 0.5%,5.0%,9.0% and 12.0% Si respectively，were treated by means of the micro arc oxidation (MAO) for 15 min.Then,the MAO layers were investigated in terms of formation process,characteristics and energy consumption,and were characterized by means of SEM,EDS and XRD.The results show that (1) under the MAO treatment at constant current，as the Si content increases,the ascent rate of positive voltage,the striking voltage and the positive voltage during discharge stage,the average growth rate of the layer decease while the pores of discharge channels and the waiting time before spark discharges increase; (2) however,under the MAO treatment at constant voltage,the Si content has a weaker effect on the MAO of Al-Si al- loys，and as the Si content increases,the positive and negative current densities of the alloys both increase and the layers have a gradually-decreasing growth rate but with a similar surface morphology; (3) the layers on Al-Si alloys obtained through the two MAO modes at constant current and constant voltage are both composed of γ-Al₂O₃,α-Al₂O₃ and mullite,and the Al₂O₃ content in the alloys decreases with the increase of the Si content; and (4) the spe- cific energy consumption of the layers obtained through the same MAO mode increases with the Si content.Besides,both the characteristics and energy consumption of the layers on the same alloys through different MAO modes are quite different.

Key words: micro arc oxidation, Al-Si alloys, constant current, constant voltage, energy consumption