【摘要】 镁合金具有质轻,比强度和比模量高,加工性、减震性和抗冲击性好,环保易回收和电磁屏蔽性能良好等优点,在军事、航空、汽车、电子通讯等领域具有广泛的应用。但镁合金极易发生腐蚀,因此,镁合金在使用前必须进行有效的表面防护处理。在诸多的表面处理方法中,镁合金表面镀覆铝层不仅具有良好的耐腐蚀性和耐摩擦磨损性,还可保持镁合金的金属属性,同时具有轻质、易回收等优点,一直是研究和关注的热点。镁合金表面镀覆铝层的方法主要有:喷涂法、液体扩散法、渗铝法、高能束熔覆法和沉积法。沉积法又包括溅射沉积、物理/化学气相沉积、电沉积。其中电沉积法因其设备简单、操作方便、成本低廉,且镀层的厚度和质量可控,引起了研究者们的广泛关注。电沉积铝技术主要包括前处理工艺、电解液种类、电沉积工艺参数、镀后处理工艺和镀层性能等几个方面。镁合金电沉积铝前处理工艺十分关键,主要包括机械打磨、碱性除油、酸性浸蚀、活化处理和预沉积金属底层。电沉积铝电解液分为有机溶剂、离子液体和无机熔盐三类。其中,有机溶剂易挥发,现在已很少使用;离子液体绿色环保,但成本高;无机熔盐成本低,但沉积温度高,对仪器设备要求较高。电沉积工艺参数与常规水溶液相似,主要包括电流密度、电沉积温度、搅拌速率、添加剂和水含量。需要特别注意的是水含量,水汽的引入将严重影响镀层质量甚至无法电沉积铝。电沉积铝镀层与基体结合力不好是目前存在的主要问题之一,因此镀后处理工艺非常重要,镀后处理包括热处理和阳极氧化处理。热处理可在镀层与界面处形成冶金结合,显著提高镀层结合力;阳极氧化可进一步提高镀层耐腐蚀性和硬度。另外,合金化是提高镀层综合性能的有效方法之一。本文针对镁合金表面电沉积铝镀层技术,从镁合金前处理、电解液类型、电沉积铝工艺参数和镀层后处理与性能四个方面的研究现状进行了阐述,并在文献综述的基础上,结合本课题组在铝镀层方面的研究经验,对镁合金表面电沉积铝的技术难点进行了分析,并对未来的发展方向进行了展望。更多还原

【Abstract】 Magnesium alloys are widely used in various fields such as military,aerospace,automobile,and electronic communication,owing to their desirable properties,including light weight,high specific strength and specific modulus,good workability,high shock resistance and impact resistance,environmental protection and recyclability,and excellent electromagnetic shielding property. However,the poor corrosion resistance of Mg alloys seriously limits their wider applications. Thus,surface protection treatment must be adopted to magnesium alloys.The aluminum coating deposition on the surface of the magnesium alloys is considered to be the most ideal one among the many surface treatment methods,which has aroused widespread attention by virtue of its improved corrosion and wear resistance,the metal properties,light weight and easily recycled properties. The main methods of aluminum coating deposition on magnesium alloy are spray coating method,liquid diffusion method,aluminizing method,high energy beam cladding method and deposition method. Additionally,the deposition method can be further classified to sputter deposition,physical/chemical vapor deposition,and electro-deposition. Among them,the electro-deposition method is attracting increasingly attention on account of its simple equipment,convenient operation,low cost and controllable thickness and quality of the coating.The processes of electro-deposition aluminum technology mainly include pre-treatment,electrolyte type,electrodeposition process parameters and post-plating treatment process and coating performance. Pre-treatment process is crucial which consists of grinding,alkaline degreasing,acid etching,activation treatment and pre-deposited metal underlayer. The electrolytes for electro-deposited aluminum include three types: organic solvents,ionic liquids and inorganic molten salts. Organic solvents are rarely used due to their volatility. Ionic liquids are environment-friendly and recyclable,while the high cost limits their quantity production. The low-cost inorganic molten salts demand for high deposition temperature and instrumentation. The electro-deposition process parameters are similar to the conventional aqueous solutions,including current density,electrodeposition temperature,agitation rate,additives and moisture content. Special attention should be paid to the moisture content,since even slight moisture can severely affect the quality of Al coating and even lead to unable to deposit aluminum. The post-plating treatment processes,including heat treatment and anodization,are extremely pivotal to the poor adhesion between the electro-deposited aluminum coating and the substrate.Heat treatment significantly promotes the adhesion of the coating by forming metallurgical bonding between the coating and the interface. Anodization can further ameliorate the corrosion resistance and hardness of the Al coating. Moreover,electro-deposition of alloy coating is an effective way to comprehensively improve the properties of the aluminum coating.In this paper,the research progress of aluminum coating by electro-deposition on magnesium alloy surface is illuminated from four aspects of pre-treatment,electrolyte type,electrodeposition aluminum process parameters and post-plating treatment and properties of the coatings. The crucial technical barriers of electrodeposited aluminum on the surface of magnesium alloy are analyzed and the future development view are pros-pected combined the research experience on aluminum plating in our group.更多还原