为了解电压在镁合金微弧氧化中的作用, 本工作在双极性脉冲电源的恒流加载方式下, 通过考察电压对氧化时间、膜层厚度及表面形貌的影响, 研究电压对微弧氧化机理的影响。结果发现, 当负电压为零, 占空比20%和30%时, 电压低于380V时所需的氧化时间要短于电压高于380 V时的氧化时间。当占空比30%, 负电压为零和40 V时, 电压低于340 V的氧化时间和膜层增长速率都小于电压高于340 V的; 电压低于340 V时的膜层表面形貌优于340 V以上膜层。可见, 微弧氧化过程中存在一个临界电压, 微弧氧化过程分成两种情况, 两种情况的微弧氧化机理不尽相同。

For making clear the role of voltage in micro-arc oxidation of magnesium alloys, experiments were carried out in the bipolar pulse output mode and under constant current load to investigate the influence of voltage on oxidation time, film thickness and surface morphology. The results indicated that when the negative voltage was zero and duty cycle was 20% and 30% respectively, the oxidation time at 380 V was less than that above 380 V. When the negative voltage was 0 V and 40 V, the oxidation time and film thickness at 340 V were greater than those of above 340 V, but the surface morphology below 340 V was letter than above 340 V. It is clearly seen that there is a critical voltage in micro-arc oxidation process and it would separate the micro-arc oxidation process into two stages, i.e., pre-and post-oxidation. In both phases, the micro-arc oxidation mechanisms are different.