采用自制的恒流非对称方波电源用微弧氧化法在AZ91D镁合金表面制备了耐腐蚀陶瓷膜,通过微观分析手段对微弧氧化膜的截面特征、元素成分分布及表面膜的相组成进行了分析,研究了微弧氧化工艺参数对膜层表面形貌、微观结构与组成等的影响.结果表明,提高电流密度会造成组织疏松微孔孔径增大;硅酸盐溶液中微弧氧化制得的陶瓷膜优于铝酸盐溶液.而且电解液中的离子可参与成膜反应,硅酸盐溶液体系镁合金微弧氧化陶瓷层主要由MgO和Mg_2SiO_4相组成,铝酸盐溶液体系微弧氧化膜层主要由MgAl_2O_4相组成.
A crossion-resistance ceramic coating was prepared on AZ91D magnesium alloy by micro-arc oxidation method with an asymmetric ac power supply. Silicate-based and aluminate-based electrolyte were adopted in the micro-arc oxidation process, and it shows that the coating formed in silicate solution is more continuous and compact than that formed in aluminates solution. In order to understand the effect of processing parameters upon the micro characteristics of the formed ceramic coating, many micro-analytical methods of SEM, EDS and XRD were used to study the morphology and microstructure of the ceramic coating. It was found that the coating consists of two layers, i.e., loose layer and compact layer, and the elevated current density will lead to the increment of micropore size in loose layer. The compositions and phase structures varied with the electrolyte components, and it was also known that the micro-arc oxidation coating prepared in silicate solution is composed of MgO and Mg_2SiO_4, while the coating prepared in aluminate is mainly composed of MgAl_2O_4.
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