锌基—稀土合金机械镀无结晶形层机理及工艺研究

【作者】 赵霞；

【导师】 何明奕；

【作者基本信息】 昆明理工大学 ， 材料加工工程， 2007， 硕士

【摘要】 论文针对在室温下以无结晶过程形成锌基—稀土合金镀层的工艺过程、镀层性能和相关形层理论进行研究分析，初步确定了锌基—稀土合金机械镀的工艺，并进行了工业验证。利用体视显微镜、金相显微镜、扫描电子显微镜观察分析了机械镀Zn-RE、Zn-Al-RE合金镀层的表面形貌和断口结构，对其致密度、显微硬度、耐腐蚀性和电化学特性等性能进行检测，并分析添加稀土对镀层形成和性能的影响。结果表明：在所设计的稀土金属(<5％)及铝粉(<5％)添加范围内，加入2％稀土的Zn-RE镀层与加入1％稀土、3％Al粉的Zn-Al-RE合金镀层是综合性能非常优良的防护性镀层。镀层形成过程中，适量稀土金属盐的加入能影响金属微粉的集聚、吸附和沉积特性，使得金属粉在以无结晶方式形层时趋于面状吸附-沉积，改善了镀层的形成条件。并使得机械镀锌基稀土合金镀层的致密度、显微硬度、耐腐蚀性和电化学特性明显优于传统机械镀锌层。对于Zn-RE镀层，镀层的各项性能测定值曲线均呈现先增高后降低的趋势，在稀土金属盐加入量2％的位置出现拐点；对于Zn-Al-RE合金镀层，镀层的各项性能测定值曲线随稀土加入量的增加呈现递减的趋势，在稀土金属盐加入量1％的位置出现极大值。利用X射线荧光光谱仪、扫描电镜及能谱仪，初步确定了镀层中铝的成分、分布及稀土的存在。结果表明：加入1％～3％稀土的机械镀Zn-Al-RE镀层，Al均匀分布于镀层表面，有利于形成均匀致密氧化铝膜，提高镀层的耐腐蚀性能；当稀土加入量超过3％时，镀层表面Al含量大大降低且分布不均。稀土元素存在于镀层当中，但其含量还有待于进一步的确定研究。论文还通过对镀层形成过程及组织结构的探讨分析，得出以无结晶方式形成Zn-RE、Zn-Al-RE合金的形层机理。在形层过程中，Sn结晶携带金属粉形层；Al粉被Zn粉包裹共同沉积，由于其活化效率低于Zn粉，导致Al有偏聚倾向；添加的稀土金属盐，增加了金属粉的分散、润湿性，细化均匀了金属粉藻团、使得金属粉趋于面状吸附-沉积，加快了吸附过程的进行，从而改善了镀层的形成条件。技术经济分析表明，机械镀锌基—稀土合金是一种环保型的“绿色技术”，具有较大的工业应用价值。更多还原

【Abstract】 The technical process, performance and related cambium theory of Zinc-base alloy with rare earth cladding in a none-crystallization form were studied, the technical process of mechanical zinc-base alloy with rare earth plating was initially identifie d and proceeded industrial test.Surface orphology and structure of fracture surface of mechanical Zn-RE, Zn-Al-RE plating were studied using stereomicroscopy, metalloscopy and scanning eletronic microscopy. The density,microhardness,corrosion resistance and electrochemical characteristics were detected and the influence of adding rare earth on its cladding formation and performance was analyzed. In the scope of design(rare earth <5%, aluminum <5%), Zn-RE coating adding 2% RE and Zn-Al-RE alloy coating adding 1% RE and 3% Al were protection film with fine integral performance. During the process of coating formation, adding rare earth can impact the aggregation, adsorption and sedimentation characteristics of small metal powder, and make metal powder drive to planimetric aggregate-adsorption. In the result, the conditions of the formation were improved, and the density, microhardness, corrosion resistance and electrochemical characteristics of mechanical zinc-base alloy with rare earth plating were better than the galvanizing layer obviously.For Zn-RE coating, the performance curve showed a increasing first and then decreasing trend. When adding 2% RE, the performance curve presented inflection point; for Zn-Al-RE alloy coatings, the performance curve showed a decreasing trend with increasing of rare earth’s addition. When adding 1% RE, the performance curve presented a great value.The aluminum composition, distribution and the existence of rare earth were initially identified using X-ray diffraction fluorescence spectra, scanning eletronic microscopy and energy spectrometer. For mechanical Zn-Al-RE plating added 1%～3 % RE, Al evenly distributed on the surface of the coating. It was propitious to the forma tion of uniform and dense pellumina to enhance the corrosion resistance of the coatin g; When the addition of rare earth was more than 3%, Al content on the surface of the coating greatly reduced and unevenly distributed. The rare earth exists, but its content has yet to determine further. The mechanics of the zinc-base alloy with rare earth cladding in the nonecrystallization form was reached by analyzing formative process and organizational structure. During the process of coating formation, Sn crystallined and carried the metal powder to form cladding; Zn powder wrapped Al powder and proceeded co-deposition. Because Al powder’s activated efficiency is lower than Zn powder’s, there was a Al segregation tendency; The rare earth resulted an increase of the metal powder’s dispersibility and wettability. The rare earth made the metal powder maerl become thin and homogeneous, made metal powder drive to planimetric aggregateadsorption, and accelerated the process of adsorption. Accordingly, the formative conditions of the coating were improved.Cost-effectiveness analysis indicates that mechanical zinc-base alloy with rare earth plating is an environmental"green technology" with the larger industrial applications.更多还原