镁表面低缺陷富铝扩散层的制备及耐蚀机理研究

The poor corrosion resistance is the most important problem which limits the wide application of Mg alloys. Magnetron sputtering with aluminum on the surface of Mg is a green and important method to improve the corrosion resistance of Mg. However, the inevitable defects in the sputtering layer limit the benefits of this technology. Therefore, this project proposes heat treatment to make the aluminum in the film diffuse to the magnesium matrix. It produces the diffusion layers which can enhance the protectiveness of the aluminum layers for the Mg matrix. As a result, the corrosion resistance of Mg will be dramatically increased. The magnesium matrix can be improved by hot rolling. The small grains in the Mg matrix will facilitate the diffusion process. As the aluminum layer is combined with the Mg matrix tightly, the diffusion activation energy can be smaller than traditional diffusion. Therefore, the diffusion process can be operated under the eutectic temperature and obtain the layers with few defects. The project will focus on the influence factors and corrosion mechanism of the diffusion layers. The parameters of the heat treatment will be optimized based on the research achievement in order to obtain the corrosion resistant magnesium with aluminum film on the surface. The feasibility of the research has been evidenced by our preliminary experiment results. The knowledge obtained during this research is of great significance for the solution of poor resistance of Mg, which will provide a scientific basis for corrosion and protection of magnesium.

耐蚀性能差是现在制约镁应用最主要的问题。绿色环保的磁控溅射镀铝技术是提高镁耐蚀性能的重要方法。但由于得到的铝膜含有缺陷而使镁耐蚀性的提高受到限制。针对这一问题，申请人提出利用热扩散技术使溅射膜层中的铝向镁基体扩散，形成低缺陷富铝扩散层，改善膜层缺陷，大大增强其对镁基体的保护性能。通过热轧技术使原镁基体晶粒细化，大大促进热处理时铝元素的扩散，结合溅射沉积的铝膜和镁基体紧密结合从而使扩散激活能较小的优势，使在镁铝共晶温度以下顺利扩散成为可能，从而得到低缺陷致密扩散层。通过重点研究扩散层（特别是膜层率先失效处）的腐蚀行为和机理，明确热处理参数对镁铝扩散层耐蚀性和对镁基体保护性的影响机理，以此为指导优化热扩散参数，实现镁合金耐蚀性能的巨大提高。本项目的核心构思已在前期实验中得到验证。本项目的完成可为解决镁合金腐蚀问题探索一条可行的办法，具有明确的理论和实际意义。

镁合金是最轻的金属结构材料，具有低密度、高比强度和良好的阻尼减震性等优点，在航空航天、军事国防、电子器件和生物医疗等关键领域具有极其重要的应用价值。然而，腐蚀问题严重限制了镁合金大规模应用。本项目运用磁控溅射非平衡技术在镁和镁合金表面溅射了一层纯铝或其他金属涂层，实现了在Mg-Al共晶温度下均匀热扩散制备得到保护性涂层，使镁的耐蚀性得到大幅度地提高，腐蚀电流密度低至0.6μA/cm2。本项目揭示了扩散层对镁合金耐蚀性能的影响及作用机理，建立了镁表面保护性涂层缺陷处的微观腐蚀模型及相关理论。同时，本项目研究开发了多种涂层，并拓展了这些涂层在镁空气电池及人体中的应用。如Mg-Zn非晶态涂层合金具有不析氢的特性，其腐蚀原理与之前报道的都不一样,该合金涂层未来可以用在人体可降解纳米机器人的能源供应上；Mg-Al非晶涂层具有高容量的阳极特性，可用在镁空气电池以及鱼雷的海水激活电池上；无机涂层可用在人体可降解支架上，延长其降解时间。本项目的成果对解决镁合金腐蚀问题和拓展镁合金的应用具有重要的理论和实际意义。