微弧氧化及封孔处理对AlSi12Cu铝合金性能的影响

发布时间：2018-05-08 06:15

本文选题：AlSi12Cu合金 + 微弧氧化　；参考：《南京理工大学》2017年硕士论文

【摘要】：AlSi12Cu合金属于铸造铝合金系列,具有低密度、良好的加工性能、一定的强度和耐蚀性等特点,广泛应用于汽车、航空航天、海洋运输及家用工具等领域。但其硬度低,耐磨性差。在一些介质中AlSi12Cu合金的耐腐蚀性也不能满足要求,从而限制了其应用范围。为了提高AlSi12Cu合金的耐磨和耐蚀性能,本文采用微弧氧化(Micro-arc oxidation,MAO)技术在其表面制备氧化铝涂层,利用正交实验设计方法对微弧氧化工艺的电流密度、氧化时间和频率三个参数进行优化研究,采用扫描电子显微镜(SEM)及其附带的能谱仪(EDS)、X射线衍射(XRD)仪分别对膜层的表面形貌、元素含量和物相组成进行分析,并对膜层的耐蚀性和耐磨性能进行了分析评价。为了进一步提高膜层的耐腐蚀性能,对微弧氧化后的试样进行封孔处理,研究了封孔处理方法对其耐蚀性能性能的影响。通过系统研究,得到了如下的主要结果:通过正交实验确定了微弧氧化处理的最佳工艺条件:电流密度为30 A/dm2,电源频率为600 Hz以及氧化时间为20 min。在最佳工艺参数条件下进行微弧氧化获得的膜层厚度为15μm左右,主要由α-Al2O3、γ-Al203、θ-Al2O3和A1组成,膜层与铝合金基体之间结合牢固。AlSi12Cu合金经微弧氧化处理后,耐磨性明显提高,摩擦系数由铝合金基体的0.64减小为0.37;经微弧氧化的铝合金材料在盐雾腐蚀240小时后,还未出现表面腐蚀现象,而在洗衣粉溶液中的腐蚀速率则较铝合金基体降低了 25倍,说明微弧氧化处理使AlSi12Cu合金得耐腐蚀性能也得到了显著改善。利用硅酸钠和硬脂酸封孔剂对微弧氧化膜层进行封孔处理。结果表明,两种封孔方法都能有效将微弧氧化膜层上的微孔及一定数量的大孔封堵,并使膜层的耐蚀性进一步提高。其中,用硬脂酸进行封孔处理效果更好。在3.5%NaCl溶液中的电化学腐蚀实验结果表明,微弧氧化铝合金经硬脂酸封孔处理后,腐蚀电流密度较铝合金基体降低了100倍,腐蚀电位正移了 285 mV。
[Abstract]:AlSi12Cu alloy is a kind of cast aluminum alloy series, with low density, good processing performance, certain strength and corrosion resistance and so on. It is widely used in automobile, aerospace, marine transportation and household tools and so on. But its hardness is low, wear resistance is poor. In some media, the corrosion resistance of AlSi12Cu alloy can not meet the requirements, thus limiting its application range. In order to improve the wear resistance and corrosion resistance of AlSi12Cu alloy, alumina coating was prepared on the surface by micro-arc oxidation (Micro-arc oxidation) technique. The current density of micro-arc oxidation process was studied by orthogonal design method. Three parameters of oxidation time and frequency were optimized. The surface morphology, element content and phase composition of the film were analyzed by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS / X ray diffractometer). The corrosion resistance and wear resistance of the film were analyzed and evaluated. In order to further improve the corrosion resistance of the film, the pore sealing treatment was carried out on the samples after micro-arc oxidation, and the effect of the sealing treatment method on the corrosion resistance of the samples was studied. The main results are as follows: the optimum process conditions of micro-arc oxidation are determined by orthogonal experiment: current density is 30A / dm ~ 2, power frequency is 600 Hz and oxidation time is 20 min. The thickness of the film obtained by microarc oxidation under the optimum technological parameters is about 15 渭 m. The film is mainly composed of 伪 -Al _ 2O _ 3, 纬 -Al _ 2O _ 3, 胃 -Al _ 2O _ 3 and Al _ 1. The wear resistance of the film is obviously improved by micro-arc oxidation. The friction coefficient of aluminum alloy decreased from 0.64 to 0.37, and the corrosion rate in washing powder solution was 25 times lower than that in aluminum alloy matrix after 240 hours of salt spray corrosion. The results show that the corrosion resistance of AlSi12Cu alloy is improved remarkably by micro-arc oxidation treatment. The microarc oxide film was sealed by sodium silicate and stearic acid. The results show that both of the two sealing methods can effectively block the micropores and a certain number of macropores in the micro-arc oxide film, and further improve the corrosion resistance of the film. The sealing effect of stearic acid is better than that of stearic acid. The experimental results of electrochemical corrosion in 3.5%NaCl solution show that the corrosion current density of micro-arc oxidation aluminum alloy treated by stearic acid sealing is 100 times lower than that of aluminum alloy substrate, and the corrosion potential is 285mV.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.451

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