镁锂合金论文：Mg-12Li-2Al-2Zn合金表面防腐工艺的研究.doc

镁锂合金论文：Mg-12Li-2Al-2Zn合金表面防腐工艺的研究【中文摘要】镁锂合金是最轻的金属结构材料,具有良好的延展性,在3C等行业应用前景广阔,开展其表面防腐研究有利于其推广应用。本文通过光学显微镜(OM)、扫描电子显微镜/能谱分析仪(SEM/EDS)、X射线衍射仪(XRD)、显微硬度计及恒电位仪等分析测试方法,首先探讨了三种预处理工艺对Mg-12Li-2A1-2Zn合金表面磷化膜及化学镀镍层质量的影响,由此确定合金试样的最佳预处理工艺。以此最佳试样预处理工艺为基础,分别研究了各工艺参数对Mg-12Li-2A1-2Zn合金表面磷酸盐转化膜、高锰酸盐-磷酸盐转化膜及镀镍层厚度、形貌、耐腐蚀性能的影响,并通过正交实验确定了各实验方案的最佳工艺。实验结果表明：Mg-12Li-2A1-2Zn合金的最佳预处理方案为本实验配方2#；表面磷化膜的制备及膜质量受工艺参数的影响：磷酸盐转化膜受处理温度影响大,而高锰酸盐-磷酸盐转化膜则受处理时间影响更为突出。试样表面磷酸盐处理(PH=1.5)的最佳工艺参数为化学液温度80,处理时间20 min；磷酸盐-高锰酸盐处理(PH=3)的最佳工艺参数为化学液温度70,处理时间30 min；磷酸盐和高锰酸盐-磷酸盐转化膜均为显微网状裂纹形貌特征,前者呈灰白色,后者呈红棕色；磷酸盐转化膜主要由Mg3(PO4)2和BaHPO4组成；高锰酸盐-磷酸盐转化膜的相组成是BaHPO4和Mn02。综合合金表面膜层形貌、致密性、厚度及极化曲线,磷酸盐-高锰酸盐转化膜的耐腐性优于磷酸盐转化膜的耐腐性；化学镀液的PH值、温度和施镀时间是影响合金表面镀镍层组织和性能的关键因素。本实验条件下,镁锂合金化学镀镍的最佳工艺参数为pH=70.2、温度T=802、施镀时间t=50min。在此工艺下,所获Mg-12Li-2A1-2Zn合金表面化学镀层具良好结合力,厚度1315m,显微硬度达435Hv；合金表面镀镍层由许多致密胞状物组成,并具有Ni-P非晶态结构；在最佳工艺条件下,镁锂合金试样分别经磷酸盐、磷酸盐-高锰酸盐处理或化学镀镍,均能获得表面平整致密的化学转化膜或镀镍层,从而提高合金的耐腐蚀性。通过分析比较,镁锂合金表面镀镍层的耐腐蚀性明显优于磷酸盐或磷酸盐-高锰酸盐转化膜。【英文摘要】The magnesium-lithium alloy is the lightest structure material, has been widely applied on the 3C and many other fields because of its excellent ductility, it is useful for its promoted application with carring out its superficial anti-corrosion research.First studied the effect of three kinds of pretreatment process on the surface parkerising coating and the chemical plating nickel layer quality of the Mg-12Li-2Al-2Zn alloy,then the optimal pretreatment process is determinded by using OM, SEM/EDS, XRD, micro-hardness tester and potentiostat.Take the optimal pretreatment process as the foundation, studied the effect of various process parameters on phosphate conversion coating, permanganate-phosphate conversion coatings and nickel plating by thickness, the appearance and the anti-corrosive performance.The optimal process of each testing plan was determined by the orthogonal experiments.The research shows that the optimal pretreatment process of Mg-12Li-2Al-2Zn alloy is formula 2; The preparation of phosphate coating surface and the coating quality affected by the process parameters, the phosphate coating greatly affected by the process temperature, but the permanganate-phosphate coating affected by the process time to be more prominent.The optimal process parameter of phosphate conversion (pH=1.5) is T=80, t=20min and the optimal process of permanganate-phosphate conversion(pH=3) is T=70,t=30min under this experimental conditions;The coating of the phosphate and the permanganate-phosphate conversion coating are characterized by microscopic morphology of the crack network, the former assumes the iron grey and the latter assumes the reddish brown.The phosphate conversion coating is mainly composed by Mg3(PO4)2 and BaHPO4 and the permanganate-phosphate conversion coating is mainly composed by BaHPO4 and MnO2. The corrosion resistance of the permanganate-phosphate conversion coating are better than the phosphate conversion coating by surface coating appearance, compactness, thickness and polarization curve.The effects of PH value, temperature, time on the electroless nickel-plating on Mg-12Li-2Al-2Zn alloy were investigated. The results show that the optimal process parameter of electroless nickel-plating is pH=70.2,T=802and t=50min.In the technical parameter,the hardness of the coating was about 435Hv and the thickness was about 13-15m;The coating is Ni-P amorphous state, composed by many compact alveolar;Under the optimal process condition, the magnesium-lithium alloy surfacing can obtain compact chemistry conversion coating or the nickel plating, thus improves corrosion resistance through phosphate, permanganate-phosphate or chemistry nickel plating. The corrosion resistance of the magnesium-lithium alloy surface nickel plating surpasses the permanganate-phosphate conversion coating or the phosphate conversion coating.through analysis comparison.【关键词】镁锂合金 磷酸盐 化学转化膜 化学镀镍 显微组织 耐腐蚀性【英文关键词】magnesium-lithium alloy phosphate chemical conversion electroless nickel plating microstructure corrosion resistance【目录】Mg-12Li-2Al-2Zn合金表面防腐工艺的研究摘要3-4ABSTRACT4-5第1章 绪论9-251.1 镁锂合金概论9-141.1.1 镁锂合金的特点9-111.1.2 镁锂合金的发展及研究现状11-141.2 镁锂合金的腐蚀14-171.2.1 合金元素对镁锂合金耐腐蚀性的影响16-171.2.2 环境对镁锂合金腐蚀的影响171.3 镁锂合金的表面防护17-241.3.1 镁锂合金表面化学镀18-201.3.2 镁锂合金表面化学转化膜处理20-211.3.3 镁锂合金表面有机-无机杂化涂层21-221.3.4 镁锂合金表面阳极氧化221.3.5 镁锂合金表面微弧氧化22-241.4 本文研究意义及研究内容24-251.4.1 研究意义241.4.2 研究内容24-25第2章 实验方法25-292.1 实验工艺流程252.2 实验材料25-262.2.1 合金试样的制备25-262.2.2 化学实验药品262.3 分析测试方法26-292.3.1 化学层的显微组织观察26-272.3.2 化学层的相结构分析272.3.3 化学层的耐蚀性分析27-282.3.4 显微硬度的测定28-29第3章 Mg-12Li-2Al-2Zn合金预处理的研究29-373.1 引言293.2 预处理工艺29-313.2.1 预处理工艺路线29-303.2.2 三种预处理方案30-313.3 预处理后的表面化学转化膜工艺和镀镍工艺31-323.4 预处理对合金表面磷化膜质量的影响32-343.4.1 预处理对磷化膜组织形貌的影响32-333.4.2 预处理对磷化膜耐腐蚀的影响33-343.5 预处理对合金表面化学镀镍层的影响34-363.5.1 预处理对化学镀镍层组织形貌的影响343.5.2 预处理对化学镀镍层耐腐蚀的影响34-363.6 本章小结36-37第4章 Mg-12Li-2Al-2Zn合金磷化膜的研究37-504.1 实验设计37-384.1.1 磷化处理液及工艺过程37-384.1.2 正交实验设计384.2 合金表面磷酸盐转化膜的研究38-434.2.1 工艺参数对磷酸盐转化膜层厚度的影响38-394.2.2 不同处理温度下的磷酸盐转化膜层形貌39-414.2.3 磷酸盐转化膜的耐腐蚀性能414.2.4 磷酸盐转化膜的构成41-434.3 合金表面高锰酸盐-磷酸盐转化膜的研究43-484.3.1 工艺参数对合金表面膜层厚度的影响43-444.3.2 不同处理温度下的高锰酸盐-磷酸盐转化膜的形貌44-464.3.3 高锰酸盐-磷酸盐转化膜的耐腐蚀性能464.3.4 高锰酸盐-磷酸盐转化膜的构成46-484.4 两种磷化膜的极化曲线分析484.5 本章小结48-50第5章 Mg-12Li-2Al-2Zn合金化学镀镍的工艺研究50-605.1 实验设计与过程50-515.1.1 实验方案505.1.2 化学镀镍过程50-