应用脉冲微弧氧化电源，研究频比（脉冲电源单个周期内正脉冲频率与负脉冲频率的比值）对AZ91D镁合金在碱性硅酸盐溶液中微弧氧化的影响。频比改变微弧氧化过程中的能量分布，当频比为1时，所制备膜层更厚和致密。提高频比，膜层表面更加多孔，膜层减薄，这主要是由于单个负向周期中，频比增加，负向脉冲作用时间延长。增加频比，两个正向脉冲间隔缩短，易形成更多放电通道并在膜层表面形成更多微孔。微弧氧化膜层表面的火山口形状的熔融结构主要是由于负向脉冲导致的冷却和溶解作用。改变频比，由于微弧氧化膜层的截面微观结构没有显著变化，因此频比对膜层的保护性能影响较弱，但是氧化样品较未氧化样品的耐蚀性能有显著提高。%AZ91D magnesium alloy was anodized in alkaline silicate solution using a micro-arc oxidation (MAO) pulse power source under different frequency ratio (FR), which is the ratio of the positive frequency to the negative frequency. The FR changes the distribution of energy density during the MAO process, and then remarkably influences the thickness, morphology and uniformity of the MAO coating. Uniform and thick coating was obtained at FR: 1, and then becomes more porous and thinner with increasing FR due to longer cathodic process in one negative half cycle. The decrease of the interval between two positive pulses with increasing FR results in more discharge channels and more micro-pores on the MAO coating. Many craterlets were formed on the MAO coating because of the dissolution of oxide caused by the lengthened negative half- cycle. Increasing FR, the inner structure of the MAO coating is not obviouslychanged, hence the protectiveness of the anodic coating is not seriously influenced, but the corossion resistance is improved by FR,.
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