Surface Modification on Magnesium Alloys by Magneisum Vapor Deposition.

采用气相沉积技术在镁合金表面涂覆高纯镁，对镁合金进行表面改性，以提高镁合金的耐腐蚀性。该技术原理简单，将3N级纯镁或镁合金在973K左右的真空中加热，温度约为10℃~(-3)~(-1)；在此条件下，蒸气压较高的镁可以汽化，而对镁合金耐蚀性有不利影响的重金属杂质铁、镍、铜由于蒸气压较低而不能汽化，纯镁蒸气沉积在镁合金衬底上的温度较低。盐浸试验表明，沉积涂层样品的腐蚀比未涂层样品减少了约十分之一。为了阐明提高耐蚀性的机理，进行了原位激光显微镜观察。IT…进一步研究表明，AZ31镁合金和3N级纯镁出现“丝状腐蚀”，而高纯镁、6N-镁和镀膜试件则未观察到丝状腐蚀。蒸发沉积过程中固有的净化作用可以改善镁合金的耐腐蚀性，初步实验中使用了10×10×6 mm的小尺寸镜片。对60×100×6 mm的大尺寸试件进行了实用化试验，优化了制备无缺陷涂层的工艺条件。还尝试了热压和热等静压处理，以提高粘接强度。在涂覆膜和基材之间。热压和热等静压处理也提高了耐腐蚀性。另一方面，对腐蚀产物的分析导致了另一项提高耐腐蚀性的研究。结果表明，在空气中加热，腐蚀反应生成的氢氧化镁很容易转化为氧化镁。也就是说，当样品浸泡在pH值约为12的盐溶液中后，在约673K的空气中加热，样品的表面覆盖有一层氧化镁，有望显示出良好的耐蚀性。事实上，经过“人工腐蚀-氧化法”处理的试件出现丝状腐蚀的时间比未经处理的试件延长了20倍。为同一优先领域科学研究中的“固体回收组”提供了沉积涂层试件，并在沉积涂层试件上表现出了优越的循环利用能力。较少

Surface modification of magnesium alloys has been attempted in order to improve corrosion resistance in magnesium alloys by coating the surface with high purity magnesium applying vapor deposition technique. Principle of the technique is very simple ; pure magnesium with 3N grade or magnesium alloys are heated at about 973 K in vacuum with about 10^<-3> Pa, magnesium with high vapor pressure can be vaporized under the conditions, while heavy metal impurities such as Fe, Ni and Cu, which have deteriorative effects on corrosion resistance in magnesium alloys, can not be vaporized because of their low vapor pressure, purified magnesium vapor depositis on magnesium alloy substrate set at lower temperature region. Salt immersion tests have revealed that corrosion on the deposition coated specimen is decreased about one tenth of that on the un-coated specimen.In order to clarify the mechanism for improvement in corrosion resistance, in-situ laser microscopic observations were carried out. It … More has been shown that "filiform corrosion" occurred on AZ31 magnesium alloy and pure magnesium with 3N grade, while the filiform corrosion was never observed on high purity magnesium, 6N-Mg, and on the deposition coated specimen. Purification effect intrinsically included in vaporization-deposition process can improve the corrosion resistance in magnesium alloys.Specimens with small sizes, 10×10×6mm, were used in the preliminary experiments. large size specimens, 60×100×6mm, were attempted to be used for practical usage, and conditions for fabricating defect-less coating were optimized. Hot pressing and HIP treatment were also tried in order to improve adhesion strength. between the coated film and substrates. Corrosion resistance was also improved by hot pressing and HIP treatment.On the other hand, analyses of the corrosion products lead to another study for improving corrosion resistance. It has been shown that magnesium hydroxide formed by the corrosion reactions is easily changed into magnesium oxide by heating in air. That is, when the specimen is heated in air at about 673 K after immersion in salt solution with pH value of about 12, surface of the specimen was covered by magnesium oxide which is expected to show superior corrosion resistance. Indeed, time for occurring filiform corrosion on the specimen treated by the "artificial corrosion-oxidation method" is prolonged by a factor of twenty in comparison with that on the un-treated specimen.The deposition coated specimens were provided for the "Solid recycling group" in the same Scientific Research on Priority Areas, and superior property for recycle ability on the deposition coated specimen has been shown. Less