刘纹序,李秀兰,周新军.AZ81 镁合金表面固态扩渗 Al、Zn 渗层形成机理[J].表面技术,2018,47(8):36-41.
LIU Wen-xu,LI Xiu-lan,ZHOU Xin-jun.Formation Mechanism of Al and Zn Coating by Solid Diffusion on AZ81 Magnesium Alloy Surface[J].Surface Technology,2018,47(8):36-41 |
| AZ81 镁合金表面固态扩渗 Al、Zn 渗层形成机理 |
| Formation Mechanism of Al and Zn Coating by Solid Diffusion on AZ81 Magnesium Alloy Surface |
| 投稿时间：2018-04-02 修订日期：2018-08-20 |
| DOI：10.16490/j.cnki.issn.1001-3660.2018.08.006 |
| 中文关键词: 镁合金 Al Zn 固态扩渗 形成机理 |
| 英文关键词:magnesium alloy Al Zn solid diffusion formation mechanism |
| 基金项目:国家自然科学基金青年科学基金项目（51701133）；四川省教育厅重点项目（18ZA0348）；四川理工学院人才引进项目（2017RCL07）；过程装备与控制工程四川省高校重点实验室项目（GK201703） |
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| 中文摘要: |
| 目的 通过表面固态扩渗合金化技术获得金属扩渗涂层，研究扩渗涂层的形成机理。方法 在 390 ℃ 对 AZ81 镁合金表面固态扩渗 Al 和 Zn，通过 X 射线衍射仪和光学显微镜，对扩渗合金层的物相结构和形貌进行分析，通过建立扩渗过程模型研究其扩渗形成机理。结果 扩渗时间为 4~8 h 时，合金扩渗层中除了 AZ81 镁合金的原始相-Mg+Mg17Al12 外，还会发生 Mg0.97Zn0.03→Mg7Zn3+Mg2Zn3+Mg2Zn11+AlMg2Zn→ Mg32(Al,Zn)49+AlMg4Zn11+AlMg2Zn 等变化。Al 和 Zn 初始阶段在 AZ81 镁合金表面的扩渗机理为空位扩散， Al 和 Zn 固溶于镁合金基体表面，Zn 原子首先达到最大固溶度，Mg 和 Zn 反应生成化合物。但在 390 ℃下 扩渗，Mg 和 Zn 的化合物不稳定，会发生分解，形成更稳定的 Mg-Al-Zn 化合物。Mg-Zn 化合物出现后，渗层的形成机理表现为空位扩散+反应扩散+熔化分解，Mg-Zn 化合物的熔化分解加速了扩散和反应扩散的进程。结论 AZ81 镁合金表面固态扩渗金属 Al 和 Zn，在同一扩渗温度下，随扩渗时间的延长，渗层的厚度、相组成、大小、形貌逐渐发生变化，扩渗合金层的主要形成机理由物理扩散转变为反应扩散。 |
| 英文摘要: |
| The work aims to obtain the metal diffusion coating by the surface solid diffusion technology and study the formation mechanism of the diffusion coating. Solid diffusion Al and Zn was prepared on AZ81 magnesium alloy surface at 390 ℃, the phase constituents and morphologies of the diffusion alloyed coating were analyzed by X-ray and optical microscope. And the diffusion formation mechanism was studied by building diffusion processing model. When the diffusion time changed from 4 h to 8 h, the alloy coating changed as follows except the original phases -Mg+Mg17Al12 in AZ81 magnesium alloy: Mg0.97Zn0.03→Mg7Zn3+Mg2Zn3+Mg2Zn11+AlMg2Zn→Mg32(Al,Zn)49+AlMg4Zn11+AlMg2Zn. The mechanism of surface diffusion of Al and Zn on AZ81 magnesium alloy was vacancy diffusion at the initial stage. Al and Zn were dissolved in AZ81 magnesium alloy matrix surface, Zn firstly reached to the matrix solid solubility and then Mg and Zn reacted to generate compounds. However, the Mg and Zn compounds were thermodynamically unstable and decomposition occurred at the diffusion temperature of 390 ℃ and the more stable Mg-Al-Zn compounds were formed. After the presence of Mg-Zn compounds, the formation mechanism of the diffusion coating was combined with vacancy diffusion, reaction diffusion and melt decomposition and the diffusion and reaction diffusion process were accelerated by melt decomposition of Mg-Zn compounds. The thickness, phase constituents, phase size and morphology of diffusion coating for solid diffusion Al and Zn on AZ81 magnesium alloy change gradually with prolonged diffusion holding time at the same temperature. The main formation mechanism of the diffusion coating changes to reaction diffusion from physical diffusion. |
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