阴极电流密度对LY12铝合金微弧氧化膜致密性的影响

采用双极性脉冲电源，在一定的阳极电流密度 (j_a) 下，通过改变制备过程中阴极电流密度 (j_c) 的大小，在LY12铝合金表面制备微弧氧化膜。采用SEM，EIS和中性盐雾实验研究微弧氧化膜的表面微观形貌、致密性以及实际服役性能的变化，进而分析j_c对LY12铝合金微弧氧化膜致密性的影响。结果表明：施加适当的j_c可以制备致密性较好的氧化膜；当j_c较低或较高时，微等离子体在基体表面放电火花分布不均，无法获得致密性氧化膜；当j_a=5 A/dm²，j_a∶j_c=1∶1时，获得的LY12铝合金微弧氧化膜的致密性最佳。

Effect of Cathodic Current Density on Compactness of Micro Arc Oxidation Film on LY12 Al Alloy

A micro arc oxidation (MAO) ceramic film on LY12 Al alloy was prepared by using bipolar pulsed power supply with changing cathodic current density (j_c) while keeping a constant anodic current density (j_a). The morphology, barrier property and practical service performance of the film were studied by scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS) and neutral salt spray test. Then, the effect of j_c on the film compactness was analyzed. Experimental results showed that the j_c value was a key factor responsible to the film compactness. The film prepared by an appropriate j_c value exhibited a good compactness, however, by a value above or below which the compactness of the films became worse due to that the electro-sparks ununiformly distributed throughout the Al alloy surface. When j_a=5 A/dm² and j_a∶j_c=1∶1, the MAO film on LY12 alloy showed the best compactness and protection performance.