【作者】 陈同环；

【导师】 马颖；

【作者基本信息】 兰州理工大学 ， 材料加工工程， 2008， 硕士

【摘要】 镁合金具有密度低、比强度大、能量衰减系数大、优良的电磁屏蔽特性以及辅助散热功能等性能,已成为有色金属材料中最具有开发和应用前景的金属结构材料之一,但是镁合金耐腐蚀性差的弱点严重影响着镁合金的广泛应用,因此对镁合金进行表面改性具有明确的应用背景和实际意义。本论文提出的微弧氧化着色技术,意图在制取镁合金表面防护膜的同时,也能获得良好的装饰性,实现镁合金微弧着色膜颜色的多样化。本文首先研究了,在以硅酸盐体系为基础溶液添加KMnO₄和络合剂的溶液中,在镁合金表面制备微弧氧化着色膜的工艺条件,包括电流密度、反应时间、溶液浓度、着色盐和络合剂配比对微弧氧化着色膜的影响。通过实验找出了能制得性能优异膜层的条件。并借助SEM,XRD等方法,观察了陶瓷层的形貌、结构,并测定了陶瓷层的相组成。对不同实验条件下制备的陶瓷膜的厚度、耐腐蚀性等性能进行了测试分析。结果表明,经电子探针检测后发现显色的元素主要是Mn元素,而经过XRD检测可以进一步确认显色的物相主要是Mn₂O₃;考察溶液浓度、反应时间、电流密度三个参数对颜色的影响,发现溶液浓度对颜色的改变影响最大。着色盐浓度过高或过低对膜层颜色和表面质量都不好,因此选用中等浓度组溶液为宜。保持相同电流密度和溶液浓度,随处理时间的延长,试样的厚度在增大;而在相同着色盐浓度、相同处理时间条件下,电流密度大的试样膜层厚度的增长趋势要大于电流密度小的试样。其次,在电解着色的过程中,将在添加KMnO₄的电解液中进行微弧氧化着色过的试样,放置在硫酸镍溶液中,通过改变反应时间和改变电解液浓度,观察膜层相组成、形貌、厚度等的变化。试样在处理的过程中由于放置于阴极,对于膜层起到了加载负脉冲的作用,因此会使膜层有消融的现象;在电解液中也不宜处理时间过长,否则容易导致表面部分氧化膜脱落;在电解着色的过程中,延长电解时间或者提高硫酸镍含量,都会使膜层里镍的含量提高。经过电解着色的试样耐蚀性有所提高。最后,将在硅酸盐基础电解液进行微弧氧化的试样放置在硫酸镍溶液中,通过改变反应时间和改变电解液浓度,观察膜层相组成、形貌、厚度等的变化。在电解液中处理时间过长也会引起表面膜层的部分氧化膜的剥落。通过在硫酸镍溶液中电解着色试样的耐蚀性有所提高,但总的来说先进行微弧氧化着色再进行电解着色的试样耐蚀性好。更多还原

【Abstract】 Magnesium alloys is low density, high strength/weight ratio, large coefficient of energy attenuation, excellent electromagnetic shield and capability of emitting heat and so on. Therefore it becomes one of the most important metal in the way of its development and application. However, corrosion resistance of magnesium alloys is very poor, which mainly effects its wide application in the field of automotive and electro-mmunication. This thesis is to use MAO coloring to obtain the good corrosive resistance and colouring ceramic coating on magnesium alloys.Firstly, how the processing parameter including current density、treating time、colourant’s concentration、thepropotion of potassium permanganate and complexing agent effect on magnesium alloy cecamic coating by the micro-arc oxidation colouring in sodium silicate solution which is added potassium permanganate and complexing agent has been investigated. The condition being able to make the outstanding colouring ceramic coatings by the experiment have been found out.Draw support from method such as SEM and XRD, morphology, microstructure and phase composition of colouring ceramic coatings were observed. Thickness and corrosion-resistance of colouring ceramic coatings in different experiment condition were tested and analysed. The results show that, The element discovering a coloration by TEM testing is Mn element mainly; but being able to affirm the coloration thing further by that XRD checks is Mn₂O₃; Colourant’s concentration influence coating’s colour most in sodium silicate solution. Both too high and too low colourant’s concentration is disadvantageous for the quality of colouring ceramic coatings, so selecting and using the medium colourant’s concentration solution will be suitable. Keep identical current density and colourant’s concentration, the samples thickness is enhancing by prolonging treatment time; But under identical concentration of potassium permanganate and treatment time condition, the more current density of colouring ceramic coatings, the thickness increase trend is more quick.Secondly, in the electrolytic colouring process, the coloring samples with micro-arc oxidation were placed in nickel sulfate solution. With changing reaction time and colourant’s concentration, the changes of phase composition, morphology and thickness for colouring ceramic coatings were observed. Because the samples were assigned as cathode, the effect of loading undershoot has been on the colouring ceramic coatings, and the ablation phenomenon of the colouring ceramic coatings can be observed; the treated-time was not too long in electrolyte, otherwise, it can result in the colouring ceramic coatings of surface exfoliated, during the electrolytic colouring process, prolonging the electrolytic process or improving nickel sulfate content, that both can improve the content of nickel in the coating. In the electrolytic colouring process, prolonging the electrolytic process or improving nickel sulfate content, that both can improve the content of nickel in the coating. The coloring samples’ corrosion-resistance have been improved with electrolytic colouring.Lastly, in the electrolytic colouring process, the coloring samples with micro-arc oxidation were placed in nickel sulfate solution. With changing reaction time and colourant’s concentration, the changes of phase composition, morphology and thickness for film layer were observed. The treated-time was too long in electrolyte can result in the oxide film of surface exfoliated. The coloring samples’ corrosion-resistance have been improved with electrolytic colouring. On the whole, The coloring samples’ corrosion-resistance is great by the micro-arc oxidation colouring first and then electrolytic colouring treated.更多还原