【作者】 渠毓萍；

【导师】 李忠厚；

【作者基本信息】 太原理工大学 ， 材料加工工程， 2005， 硕士

【摘要】 镁及镁合金(如AZ91D)具有密度小、比强度高、尺寸稳定性好及良好的磁屏蔽性等一系列特性,正成为现代高新技术领域中最有希望的材料,其性能优于铝基合金。它以其优异的力学性能、物理性能已经广泛的应用于航空航天、汽车工业、电子工业等领域,然而,镁合金在各介质中的耐蚀性差使其应用受到了制约。如何解决这个问题,一直是人们所关注的课题。 现有许多表面工程技术被用来提高镁合金的耐蚀性,如化学氧化、电化学氧化、着色、酸盐转化膜层等。由于化学氧化膜薄而软,电化学氧化膜脆而多孔,故氧化处理法很少单独使用。针对其它表面改性技术的局限,本文采用一种金属表面化学镀镍技术,对AZ91D镁合金进行表面化学镀Ni-P的研究。 在前人的基础上,通过查阅相关文献资料,课题进行了在AZ91D表面上进行直接化学镀镍的研究,并且通过正交试验,探讨了在酸性条件下镁合金表面直接化学镀镍层的制备,并对Ni-P层的组织结构、电化学性能特性进行了研究。更多还原

【Abstract】 Magnesium and its alloy which are better than aluminium alloys are of many characteristics, such as small density, high specific strength, good stationary property of dimensions and fine magnetic shielding. Because of its outstanding mechanics and physical performance, it has already been applied widely in aerospace, automobile industry, electronics industry and so on, becoming one kind of most hopeful material in the modern high and new technology domain. However, application of magnesium alloy has been restricted for poor corrosion-resistance. How to improve its corrosion-resistance is an urgent topic of the day.Today, many surface treatment techniques are used for enhancing the corrosion resistance of magnesium alloy, like chemistry oxidation, electrochemistry oxidation, coloring, souring salty transformation membrane and so on. Because of thin and soft chemistry oxide film,brittle and porous electrochemistry oxide film, these oxidation methods are only used in the decoration. In view of the limitations of other surface modified technologies, this article introduces one kind of electroless nickel plating technology for enhancing corrosion -resistance of the AZ91D.In predecessor’s foundation, the research on electroless nickel plating on the AZ91D surface was proceeding through consulting related literature material. Through orthogonal experiment, it was studied that the Ni-P layer was directly obtained on the surface of magnesium alloy by electroless technique. The structure of the Ni-P layer and its electrochemistry performance were also studied. The studies indicated that Ni-P layer on the surface of magnesium alloy may be directly formed by electroless plating technique. The experimental disposition and the operation are simple, avoiding the trouble of plating the intermediate layer. Through the orthogonal experiment the best process parameter of prepared Ni-P layer had been obtained（optimal process: degreasing （10min）- acid pickling （10min） - activation （12min）, NiSO4 6H₂O （10g/L）, Na2HPO4 H2O （20g/L）, HF40% （10ml/L）, Na3C6H5O7 · 2H2O （7g/L）, NH4HF2 （8g/L）, a few buffer, PH =5.5, 80 + 2 ℃ ）. The coating thickness, the microhardness, the plating condition, microstructure and the surface morphology were measured. The heat shock and the scratchexperiments indicated that a good adhesive strength of the coating and the substrate had been obtained. The scratch appearance of the coating shows that the coating basically does not peel off.Contrast with the base material electrochemistry corrosion property under three kind of different corrosions conditions, the result showed that the corrosion electric potential of the Ni-P coating obtained a very big enhancement. In order to further examine the corrosion resistance of electroless plating Ni-P, a contrast experiment was carried for Ni-P coating, stainless steel and treated coating. Result showed that the corrosion resistance of electroless plating nickel layer lies between that of the stainless steel and that of the treated coating.The electrochemistry and the soaking experiments were carried in 3.5%NaCl solution for the coatings of the different phosphorus contents, results indicated that the corrosion resistance of high phosphorus coating is bigger than that of low phosphorus coating. Therefore, electroless nickel plating technology provided an ideal method of the protection AZ9 ID from the corrosion.更多还原