【作者】 金华兰；

【导师】 危仁杰；

【作者基本信息】 南昌大学 ， 材料加工工程， 2005， 硕士

【摘要】 由于镁合金具有比重小、比强度和比刚度大、铸造性能、机械加工性能和阻尼性能好等优点,在航空航天、汽车、机械等领域正得到日益广泛的应用,在日用品和便携式通信器材中也有良好的应用发展趋势。但是,镁合金性质活泼,在使用环境中极易受到腐蚀,这一直是阻碍其进一步开发使用的一个主要因素。磷酸盐作为镁合金表面处理的一种方法,由于集经济、无污染、膜层均匀、耐蚀等多种性能于一身,一直吸引着人们的注意力,但目前这一工艺还不够成熟和完善,膜层的防护作用不能满足要求。因此,本文围绕着镁合金的预处理、磷酸盐化学转化成膜以及涂膜进行了研究,并对化学转化膜层和涂膜的性能以及转化膜层的生长机理进行了探讨。 在镁合金磷酸盐化学处理工艺的研究中,采用正交试验的方法来确定磷酸盐处理液的成份以及处理温度和时间。采用扫描电镜(SEM)、X射线光电子能谱(XRD)对膜层的厚度和相组成进行研究,结果表明转化膜厚度大概80-110um,膜层的相组成主要为Mg、MgO和一些无定形相。 采用SWG型杠杆式万能强度试验机检测试样的抗拉强度来考察涂膜的附着力,实验结果表明化学膜层可以大大提高涂膜的附着力。采用恒温恒湿箱、盐雾试验箱、扫描电镜来研究化学转化膜和涂膜的耐蚀性能,发现膜层可以大大的提高镁合金的耐盐雾和湿热性能。综合各类试验结果,本文提出了ZM5镁合金磷酸盐化学转化膜的成膜机理和耐蚀机理,并对已有的试验事实给予了合理的解释。 本文不仅从理论上研究了在ZM5镁合金表面生成磷酸盐化学转化膜的形成过程,课题的研究成果还将拓宽磷酸盐表面改性处理在镁合金中的实际应用。更多还原

【Abstract】 Magnesium alloys have a number of desirable features, including low density, high strength-to-weight ratio, excellent casting capability, good machinability and damping characteristics, and they are now increasingly used in aerospace industry, automobile industry, mechanical engineering, commodities and portable communication equipment. However, poor corrosion resistance has often prevented them from further exploitation. Phosphate technique, one of the surface treatments of magnesium alloys, has attracted much attention due to the possession of a combination of properties, such as economical, non-contaminative, film uniformity, and good corrosion resistance. But, this process is now far from completeness. Therefore, this paper is aimed at providing a systematic study of all aspects concerning phosphate surface technique on magnesium alloys, including the pretreatment process, phosphate chemical film forming process, and coating process. Moreover, the capability of chemical conversion film and coating, and the formation mechanism of chemical conversion film have been studied.During the study of phosphate surface modification process, orthogonal test is used to determine the type of phosphate solutions, the concentration of each solution, treating temperatures and treating times. The thickness and the phase composition of conversion film have been studied by SEM (Scanning Electron Microscopy) and XRD (X-ray Diffraction). The results show that the thickness is about 80-110um and the phase composition is mainly Mg and MgO, and some amorphous phases.The adhesive force of coating is tested by lever-type multi-functional strength testing machine. Results showed that chemical conversion film could greatly improve the adhesive force of coating. The results from the study of corrosion resistance of chemical conversion film and coating by using the constant temperature and humidity box, salt spray test box and SEM (Scanning Electron Microscopy) show that films could strengthen the capability of corrosion resistance of magnesium alloys. An analytical and reasonable explanation to the formation and anti-corrosion mechanismsof phosphate chemical conversion film for ZM5 is put forward accordingly.This paper not only has studied the formation mechanisms of phosphate chemical conversion film for one kind of magnesium alloy (ZM5) theoretically but also will widen the application of phosphate surface modification technique for magnesium alloys practically.更多还原