研究了正/负向电流密度、频率和正/负向占空比对铝合金微弧氧化陶瓷层生长的影响,采用扫描电子显微镜(SEM)和X射线衍射仪(XRD),分析了不同氧化时间陶瓷层表面和截面形貌、成分和相组成,讨论了陶瓷层的生长过程.研究表明,正/负向电流密度相同时,随电流密度的增加膜层厚度增大;而当正向电流密度相同时,负向电流密度增加有利于膜层的生长;成膜速率随脉冲频率和负向占空比增加,均呈现先增大后减小的趋势;陶瓷层总厚度随氧化时间接近于线性增长,致密层占总膜层的比例先快速增加,其后略微下降.SEM结果显示,随氧化时间延长,样品表面膜厚度趋于均匀,界面处氧化膜变得比较平坦.陶瓷层主要由α-Al_2O_3和γ-Al_2O_3相组成,随氧化时间的延长,γ-Al_2O_3相在陶瓷层中的相对含量逐渐减少.而α-Al_2O_3相的含量逐渐提高.
Effect of technological parameters, such as anodic current density(Ia)/ cathodic current density (Ic), frequency, cathodic duty ratio, on the formation process of micro-arc oxidation films on 2A12 aluminum alloy are studied and the microstructure, morphologies, composition and phase constituents under different oxidation time were studied by scanning electron microscope (SEM) and X-ray diffraction (XRD). The results show that film thickness increases with the current density and the increasing of Ic is beneficial to the film growth. With frequency and cathodic duty ratio, the film thickness increases firstly then decreases. The thickness of total film increases linearly and the growth speed towards outer space is faster than that towards substrate with the oxidation time. The results of SEM show that many crater-mouth like traces formed by the plasma discharge are observed on the coatings surface, and the thickness on the cross section become same and the film/substrate interface even with MAO time. The results of XRD reveal that the content of γ-Al_2O_3 in the ceramic coatings decreases, and the content of α-Al_2O_3 increases with oxidation time.
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