摘要本文采用真空固态扩散渗锌的工艺，在 AZ91D 镁合金表面进行渗锌处理，以达 到在镁合金表面生成一定厚度渗层的目的，从而改善镁合金在各种应用环境中表面的 耐蚀性。此次试验采用控制变量法，在真空钼丝炉中通过对热扩散渗锌温度及保温时 间的控制，在 AZ91D 镁合金表面制备渗锌层，研究热扩散渗锌温度及保温时间对渗 层组织性能的影响。并采用蔡司金相显微镜以及扫描电镜对热扩渗后的试样进行组织 形貌以及渗层厚度的观察，采用能谱分析仪和 X 射线衍射仪对试样的成分和物相进 行测定，并用显微硬度计和电化学站对试样的硬度和耐蚀性进行测试。

结果表明，随着温度和时间的不断变化，试样的组织形貌、微观结构以及成分等 因素也在不断地变化。通过对比金相组织观察结果和扫描电镜分析结果，显示在 310-320℃和 1。5h-2h 范围内有明显渗层组织的出现，并且在 315℃-2h 工艺参数下可 以得到理想的渗层；再结合显微硬度分析结果和极化曲线测试结果可以确定，渗层中 金属化合物的生成，可以提高渗层的显微硬度和耐蚀性能；通过对各个参数的自腐蚀 电位和腐蚀电流的对比，发现与基体相比，经过 315℃-2h 热扩渗处理的试样自腐蚀 电位最高，腐蚀电流最低，因此可以确定此实验的最佳工艺参数为 315℃-2h。

综上所述，采用真空固态扩散渗锌的工艺可以在 AZ91D 镁合金表面形成一定理 想厚度的合金层，可以有效提高基体材料的耐蚀性，从而进一步拓宽镁合金的应用领 域。83559

毕业论文关键词：AZ91D 镁合金；热扩渗；渗层；耐蚀性

Abstract In this paper, the AZ91D magnesium alloy surface infiltration of zinc is carried out by the process of vacuum solid state diffusion infiltration of zinc, in order to achieve the purpose of generating a certain thickness of the diffusion layer in the surface of magnesium alloy to improve the corrosion resistance of magnesium alloys in a variety of applications。 The test uses a variable control method by controlling the temperature of thermal diffusion seepage zinc and holding time in a vacuum molybdenum wire furnace, and prepare infiltration of zinc layer in AZ91D magnesium alloy surface, then study the effect of Structure and properties on the diffusion layer under the temperature of thermal diffusion seepage zinc and holding time。And observing the tissue structural and morphology as well as the thickness of diffusion layer of samples after thermal diffusion by optical microscope and scanning electron microscope, measuring the composition and structure of the sample by using spectrum analyzer and X-ray diffraction, and testing the corrosion resistance and hardness through micro hardness tester and electrochemical station。

The results show that morphology and micro-structure even ingredients are constantly altering with the changing factors of temperature and time, the sample; By comparing the results of micro-structure observation and SEM analysis, displayed the layer appears at

310-320℃ and 1。5h-2h, and the ideal permeation layer can be obtained at 315℃-1。5h  and

315℃-2h; It can be determined that the formation of metal compound diffusion layer can improve the hardness and corrosion resistance of the diffusion layer by combining analysis of micro-hardness and polarization curves test results; By comparing the  corrosion potential and corrosion current of each parameter, it can be found that compared with the

substrate, the corrosion potential of sample after 315℃-2h thermal diffusion is the   highest

and the corrosion current is the lowest, so we can determine the optimal experiment parameter is 315℃-2h。

In summary, it is possible that a certain thickness in the AZ91D magnesium alloy surface can be formed by the process of vacuum solid state diffusion infiltration of zinc, therefore it can effectively improve the corrosion resistance of the base material, thus further widening the application field of magnesium alloys。