纳米Al_(2)O_(3)添加剂对VW75稀土镁合金微弧氧化膜层的影响  

Micro-Arc Oxidation Coatings Formed on VW75 Mg Alloy with Al_(2)O_(3) Nano-Additive

作　　者：梁锡炳 李兴刚 张奎 马鸣龙 蒋全通 刘小稻 Liang Xibing;Li Xinggang;Zhang Kui;Ma Minglong;Jiang Quantong;Liu Xiaodao(State Key Laboratory of Nonferrous Metals and Processes,GRIM AT Engineering Institute Co.,Ltd.,Beijing 100088,China;Key Laboratory of Marine Environmental Corrosion and Bio-fouling,Institute of Oceanology,Chinese Academy of Sciences(IOCAS),Qingdao 266071,China;Nanjing Yunhai Special Metals Co.,Ltd.,Nanjing 211200,China)

机构地区：[1]有研工程技术研究院有限公司有色金属材料制备加工国家重点实验室,北京100088 [2]中国科学院海洋研究所海洋环境腐蚀与生物污损重点实验室,山东青岛266071 [3]南京云海特种金属股份有限公司,江苏南京211200

出　　处：《稀有金属》2021年第7期812-820,共9页Chinese Journal of Rare Metals

基　　金：国家重点基础研究计划项目(2013CB632202);山东省重点研发计划项目(2017GGX20139)资助。

摘　　要：为提高VW75稀土镁合金表面耐蚀性,采用手动恒压法对合金进行了微弧氧化(MAO)。基础电解液为硅酸盐碱性电解液(Na_(2)SiO_(3)-NaOH),通过添加纳米氧化铝(α-Al_(2)O_(3))对电解液进行改性,优化原始微弧氧化层。利用数字式涂层测厚仪和带能谱的扫描电子显微镜(SEM)表征膜层厚度及表面微观组织特征,同时测试了合金在3.5%NaCl溶液中的阻抗及动电位极化。结果表明:基础电解液中制备陶瓷层,微观表面有明显"火山状"凸起分布,粗糙度较大,存在"自封孔"现象,膜层厚度可达21.45μm;添加纳米氧化铝后,"火山状"凸起减少,粗糙度降低,纳米氧化铝对孔隙"自封孔"有促进作用,膜层厚度达到22.68μm。正交试验分析发现,电压对膜层厚度及耐蚀性影响最大、氧化时间的影响最小。通过电化学测试得到,在电压为300 V、纳米氧化铝浓度为2 g·L^(-1)、氧化时间为10 min时,膜层极化电阻较大,有较好的耐腐蚀性能,腐蚀电流密度为4.86×10^(-11)A·cm^(-2),相比于未添加纳米氧化铝制备的膜层,腐蚀电流密度降低两个数量级。As the third largest metal structure material after steel and aluminum alloy,magnesium alloy has been used in automotive,electronic equipment,aerospace and other fields.Magnesium alloys meet the requirements of lightweight structure in the rapidly developing manufacturing industry at the present stage.However,the corrosion resistance of magnesium alloys itself is poor,and corrosion is easy to occur without surface protection,resulting in economic losses.Micro-arc oxidation(MAO),as a surface treatment technology developed from anodic oxidation,can surface treat the alloy with higher voltage and current density to form a porous ceramic film on the surface of the metal and its alloy,which is metallurgically combined with the matrix.At the present stage,the surface micro-arc oxidation treatment of aluminum alloy and magnesium alloy AZ series is mostly studied,and the rare earth magnesium alloy is rarely studied.VW75 rare earth alloy has good heat treatment strengthening effect(solid solution strengthening,aging strengthening),good high temperature property(heat resistance,thermal barrier property),the alloy can be used for a long time in the range of 200~250℃,and at 300℃can be used for a short time without damage.As a structural material,it has good structural mechanical properties,but in neutral or acid environment,its corrosion resistance is poor,thus corrosion is easy to occur.As an important addition element in the design of magnesium alloys,rare earth can improve the corrosion resistance of magnesium alloys from the intrinsic characteristics of the alloy.However,VW75 magnesium alloy without surface protection treatment should not be directly used in actual working conditions.Combining with the development trend of surface protection technology of magnesium alloy at present stage,a green environmental protection ceramic layer with certain protective effect was prepared on the surface of VW75 magnesium alloy by micro-arc oxidation technology.Scanning electron microscope,optical microscope,coating thickness tes

关 键 词：VW75稀土镁合金 微弧氧化 纳米Al_(2)O_(3)添加剂 耐腐蚀性能 

分 类 号：TG146.22[一般工业技术—材料科学与工程]