锆盐体系AZ91D镁合金微弧氧化制备自封闭膜层研究

发布时间：2018-03-24 14:04

本文选题：AZ91D镁合金　切入点：微弧氧化　出处：《长安大学》2015年硕士论文

【摘要】：传统微弧氧化电解液体系在镁合金表面制备的微弧氧化膜表面均匀分布大量“火山锥”状微孔。这些微孔是膜层的薄弱区,腐蚀介质可穿过微孔对合金基体产生腐蚀。为了提高膜层耐蚀性,本文利用自封闭型锆盐体系电解液在AZ91D镁合金表面制备出自封闭型陶瓷膜,封闭物质和膜层成分均匀一致,实现了膜层生长和微孔封闭一次性完成,从而提高膜层的耐蚀性。本文通过扫描电子显微镜(SEM)、X-射线衍射分析(XRD)探索氟化物、锆盐一和锆盐二浓度对微弧氧化膜层的影响。结果表明:自封闭型陶瓷膜主要相组成为MgF2、ZrO2以及Mg2Zr5O12;氟化物有利于降低起弧电压,促进膜层生长;锆盐一添加量为10g/L时孔隙率达到最小值2.1%;锆盐二可以增加单位面积弧点密度,降低处理时间,显著降低膜层孔隙率,且随着其浓度增加,膜层孔隙率降低至最小值2%左右后趋于稳定。实验得出氟化物、锆盐一和锆盐二的最佳浓度分别为15g/L,10g/L,30mL/L。采用控制处理电压和处理时间,建立了处理电压与孔隙率和膜厚、处理时间与孔隙率和膜厚的关系。结合各时期微孔封闭形态SEM照片和EDS元素图谱探讨微孔封闭过程,推断微孔封闭分为三个阶段:微孔形成及胶体、离子吸附阶段、颗粒状烧结物填充阶段、缝隙烧结“焊合”阶段。对不同工艺制备微弧氧化膜层在3.5%氯化钠溶液中腐蚀行为的研究,发现膜层的耐蚀性与孔隙率、膜厚关系密切。采用自然时效耐候试验,点滴腐蚀测试,CuCl2溶液全浸泡加速腐蚀测试和电化学测试分析,对AZ91D镁合金原始样和自封孔型电解液、未封孔型电解液处理的试样的耐蚀性进行测试,结果表明:封闭型微弧氧化膜层耐蚀性明显优于未封闭型膜层,微孔封闭对提高膜层耐蚀性效果显著。
[Abstract]:A large number of "volcanic cone" micropores are uniformly distributed on the surface of magnesium alloy surface prepared by traditional microarc oxidation electrolyte system. In order to improve the corrosion resistance of the film, the self-sealing zirconium salt electrolyte was used to prepare the self-sealing ceramic film on the surface of AZ91D magnesium alloy. In order to improve the corrosion resistance of the film, the growth of the film and the sealing of the micropore can be completed in one time. In this paper, the fluorides were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The effect of zirconium salt and zirconium salt concentration on the micro-arc oxide film is studied. The results show that the self-sealing ceramic films are mainly composed of MgF2ZrO2 and Mg2Zr5O12.The fluoride can reduce the arc starting voltage and promote the film growth. Zirconium salt can increase the density of arc point per unit area, decrease the treatment time, decrease the porosity of film layer, and increase the concentration of zirconium salt with the increase of the concentration of zirconium salt, and the porosity of film layer can reach the minimum value of 2.1 when the addition amount of zirconium salt is 10g/L. The optimum concentration of fluoride, zirconium salt 1 and zirconium salt 2 is 15 g / L ~ 10 g / L ~ (10) g / L ~ (-1) / L ~ (30) mL 路L ~ (-1) 路L ~ (-1), respectively. The treatment voltage, porosity and film thickness are established by controlling the treatment voltage and treatment time. The relationship between the processing time and the porosity and membrane thickness. The micropore sealing process was discussed by SEM photographs and EDS elemental atlas. The micropore sealing was divided into three stages: micropore formation and colloid, ion adsorption. The corrosion behavior of micro-arc oxide film prepared by different processes in 3.5% sodium chloride solution was studied. The corrosion resistance and porosity of the film were found. The film thickness is closely related. By using natural aging weathering test, droplet corrosion test, full immersion accelerated corrosion test and electrochemical test analysis of AZ91D magnesium alloy, the original sample and self-sealing pore electrolyte of AZ91D magnesium alloy are studied. The corrosion resistance of the samples treated with unsealed electrolyte is tested. The results show that the corrosion resistance of the closed micro-arc oxide film is obviously better than that of the unsealed film, and the effect of micropore sealing on improving the corrosion resistance of the film is remarkable.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG174.4

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