【作者】 陈祥；

【导师】 危仁杰； 杨湘杰；

【作者基本信息】 南昌大学 ， 材料加工工程， 2006， 硕士

【摘要】 镁在地球上储量丰富，具有比重小、比强度和比刚度大、导电导热性能好、铸造性能、机械加工性能和阻尼性能好及可以回收利用等优点，在航空航天、汽车、机械、电子、兵工等领域正得到日益广泛的应用，被誉为二十一世纪的“绿色”工程材料。但是，镁合金性质活泼，生成的氧化膜比较疏松，在使用环境中极易受到腐蚀破坏，耐蚀性差己经成为进一步扩大镁合金应用的主要障碍。 本文系统地研究了压铸AZ91D镁合金和挤压态AZ31B镁合金磷酸盐、锡酸盐化学转化膜的腐蚀性能和膜的形成机理。探索了镁合金表面形成磷酸盐、锡酸盐化学转化膜的新的溶液体系；确定了适用于镁合金的磷酸盐、锡酸盐化学转化膜和后继涂膜的最佳工艺条件。 在镁合金磷酸盐、锡酸盐化学处理工艺的研究过程中，采用正交试验法对磷酸盐、锡酸盐处理溶液的种类、浓度、处理温度和操作时间进行了研究。对生成的化学转化膜进行了各种性能检测。导电性能检测表明磷酸盐化学转化膜导电性很弱，而锡酸盐转化膜层导电性能良好，电磁屏蔽作用优良。采用扫描电镜（SEM）、X射线光电子能谱（XRD）对膜层的表面形貌、厚度、结构和相组成进行了研究，由结果可知磷酸盐、锡酸盐化学转化膜厚度分别为10～40μm和3～5μm；镁合金磷酸盐化学转化膜，呈现非晶态结构特征，它的相组成主要是Mg、Al₁₂Mg₁₇和无定形相；锡酸盐转化膜的相组成主要是Mg、Al₁₂Mg₁₇、MgSnO₃^*3H₂O，呈晶态结构特征。 使用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，实验结果表明化学转化膜层可以大大提高涂膜的附着力。用盐雾试验和恒定湿热试验检测了化学转化膜和后继涂层的耐蚀性能，结果表明膜层和涂层可以大大增强镁合金基体的抗腐蚀能力，提高了镁合金的防护性能。 综合各类试验结果，本文提出了AZ91D、AZ31B镁合金零件磷酸盐、锡酸盐化学转化膜的耐蚀特性和成膜机理。化学转化膜成膜过程分为晶核的形成和晶粒的长大两个阶段；观察表明，膜的内应力可导致膜表面产生网络状显微裂纹，但不影响膜的耐蚀性。并分析了化学成膜的影响因素—处理液成分、浓度、PH值、操作温度和处理时间对化学转化膜质量的影响。同时对已有的试验事实给予更多还原

【Abstract】 Magnesium alloys have a number of desirable features, including low density, high strength-to-weight ratio, good conducts electricity and heat capability, excellent cast capability, good machinability, damping characteristics and reusing, and its use in a variety of applications, particularly in aerospace, automobile, mechanical, electronics components, military industry. Magnesium alloys are recognized as the green materials in 21st century. However, Magnesium is very active and is susceptible to corrosion when exposed in practical application environment because of the oxidation coating is very loosen. The limited use of magnesium alloys in engineering applications results mainly from its poor corrosion resistance.A new phosphate/stannate conversion coating system for the corrosion protection of die-casting AZ91D and extruded AZ31B magnesium alloys was studied in this dissertation. This study presented an investigation of corrosion property and forming mechanism of the phosphate/stannate conversion coating formed on die-casting AZ91D and extruded AZ31B magnesium alloys. During the study of chemical surface modification process, the best technological conditions for the formation of phosphate/stannate conversion coating and subsequence coatings were settled.During the study of phosphate/stannate surface modification process, using mutual trials, the kinds of phosphate/stannate solution, the concentrations of the components in the solution, temperature and operate time were studied. The conversion coatings were checked by many kinds of methods. The phosphate conversion coating conducts little or no electricity, while stannate conversion coating conducts electricity is good, and possess excellent Electro Magnetic Interference. The thickness, surface look, structure and the phase constitution of conversion film were studied by scanning electron microscopy (SEM) and XRD. The results showed that the更多还原