AZ91D镁合金低压封孔微弧氧化陶瓷膜的制备及耐蚀性的研究

发布时间：2018-04-24 02:36

本文选题：AZ91D镁合金 + 微弧氧化　；参考：《长安大学》2017年硕士论文

【摘要】：微弧氧化能够显著提高镁合金的耐蚀性,但传统的微弧氧化所获得的陶瓷膜具有多孔结构,腐蚀性介质很容易沿着微孔穿透陶瓷膜渗入基体,结果导致陶瓷膜的耐蚀性降低。为进一步提高陶瓷膜的耐蚀性,对在较高微弧氧化处理电压形成的陶瓷膜,进行降低电压的封孔处理。本文在锆盐体系电解液中,通过调节封孔电压和封孔时间对陶瓷膜上的微孔进行封闭,实现陶瓷膜生长和微孔封闭一次性完成,进而减少腐蚀性介质通过微孔进入陶瓷膜,提高陶瓷膜的耐蚀性。此外,针对实验中的封孔过程机理进行了讨论。采用扫描电子显微镜观察陶瓷膜的微观形貌,探索了封孔电压和封孔时间对陶瓷膜表面和截面形貌的影响,分别建立了封孔电压和封孔时间与陶瓷膜厚度、孔径和孔隙率的关系。结果表明:经过低压封孔处理后,陶瓷膜表面微孔数目减少、孔径和孔隙率降低,陶瓷膜的厚度变化不大;不同的封孔电压和封孔时间所获得的陶瓷膜的表面和截面形貌、微孔形态与结构不同;当封孔电压160V,封孔时间5-8min时,陶瓷膜表面几乎观察不到微孔,封孔效果十分显著。采用X-射线衍射仪对不同封孔电压和封孔时间下的陶瓷膜相成分分析。结果表明:封孔电压和封孔时间对陶瓷膜的相组成没有影响,主要由MgF2、ZrO2、MgO和Mg2Zr5O12相组成。说明低压封孔过程中的封孔物质与陶瓷膜的成膜成分一致。采用点滴腐蚀实验、5%NaCl浸泡实验和极化曲线测试,对低压封孔处理前后的试样进行耐蚀性测试。结果表明:微弧氧化过程中形成的陶瓷膜微孔结构是腐蚀介质的主要通道,通过对陶瓷膜上的微孔进行封闭处理可以显著提高陶瓷膜的耐蚀性,此外,耐蚀性与微孔形态与结构及孔隙率具有极大的相关性,通过调整封孔电压和封孔时间可以实现对封孔的调控,从而改善耐蚀性能。
[Abstract]:Micro-arc oxidation can improve the corrosion resistance of magnesium alloy significantly, but the ceramic film obtained by traditional micro-arc oxidation has porous structure, and the corrosive medium can easily penetrate the ceramic film along the micropore into the substrate, resulting in the decrease of the corrosion resistance of the ceramic film. In order to further improve the corrosion resistance of ceramic film, the ceramic film formed at a higher voltage of micro-arc oxidation was sealed with a lower voltage. In the electrolyte of zirconium salt system, by adjusting the pore sealing voltage and sealing time, the ceramic membrane growth and micropore sealing can be achieved at one time, thus reducing the corrosive medium entering the ceramic membrane through micropores. Improve the corrosion resistance of ceramic film. In addition, the mechanism of sealing process is discussed. The micro-morphology of ceramic film was observed by scanning electron microscope (SEM). The effects of sealing voltage and sealing time on the surface and cross-section morphology of ceramic film were investigated. The sealing voltage and sealing time and the thickness of ceramic film were established respectively. The relationship between pore size and porosity. The results show that the number of micropores on ceramic membrane surface decreases, the pore size and porosity decrease, and the thickness of ceramic membrane changes little after low pressure sealing treatment, and the surface and cross-section morphology of ceramic membrane are obtained by different sealing voltage and sealing time. When the sealing voltage is 160 V and the sealing time is 5-8min, the micropores can hardly be observed on the surface of the ceramic membrane, and the sealing effect is very remarkable. The phase composition of ceramic film under different sealing voltage and sealing time was analyzed by X ray diffractometer. The results show that the phase composition of the ceramic film is not affected by the sealing voltage and the pore sealing time, and is mainly composed of MgF2ZrO2MgO and Mg2Zr5O12 phases. The results show that the sealing material in the process of low pressure sealing is consistent with the composition of ceramic film. The corrosion resistance of samples before and after low pressure sealing was tested by drop corrosion test and polarization curve test. The results show that the micropore structure of ceramic film formed in the process of micro-arc oxidation is the main channel of corrosion medium, and the corrosion resistance of ceramic film can be significantly improved by sealing the micropores on the ceramic film. The corrosion resistance is closely related to the morphology, structure and porosity of the micropores. By adjusting the sealing voltage and sealing time, the corrosion resistance of the pores can be improved by adjusting the sealing voltage and sealing time.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.45

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