摘要为提高 AZ91D 镁合金实际应用能力，本课题对 AZ91D 镁合金采用真空热扩散渗 铝工艺处理。试验采用控制变量法，在加热速率、加热时间以及真空度恒定的情况下， 尝试改变保温时间和保温温度，于镁合金表面制备渗铝层。然后用蔡司显微镜、电化 学工作站分析试样耐腐蚀性能和维氏硬度计对试样进行观察、测量、分析，以选出最 佳工艺参数。之后使用扫描电镜、EDS 能谱仪、X 射线衍射仪（XRD）分析渗铝层 物相构成。79380

研究发现，工艺参数为保温温度 400℃、保温时间 90min 所制备渗铝层最为理想。 此时渗铝层最为连续、均匀、致密，缺陷最少，其与基体之间存在过渡层。此渗铝层 相对基体自腐蚀电位更高，自腐蚀电流更低，耐腐蚀性能获得提升，对内部合金起到 良好的保护性能。此渗铝层硬度（179。9HV）相较原镁合金（70。5HV）提高大约 1。5 倍。此渗铝层外层由α-Al、β-Mg17Al12、Al3Mg2、α-Mg 构成，以α-Al、Al3Mg2 为主； 内层由β-Mg17Al12、α-Al、α-Mg 构成，以β-Mg17Al12、α-Mg 为主。

毕业论文关键词：AZ91D 镁合金；热扩渗铝；真空；耐蚀性；硬度

Abstract In order to improve the practical application of AZ91D magnesium alloy, this project studied the process of vacuum thermal diffusion treatment of AZ91D magnesium alloy。 The control variables method was used in the experiment ,with the heating rate, the heating time and the vacuum degree in constant circumstances, try to change the heat preservation time and the heat preservation temperature, preparing aluminized layer on the surface of a magnesium alloy。 Then using the Zeiss microscope ,SEM , EDS energy spectrometer, Vickers hardness tester to observe, measure, analysis, in order to obtain optimum process parameters。 Then the corrosion resistance of the sample was analyzed by the electrochemical workstation, and the phase composition of the layer was analyzed by X ray diffraction (XRD)。

The study found that the process parameters of heat preservation temperature of 400℃, heat preservation time  90min  is  the  most ideal for the preparation of the  layer  of

aluminum。 The self corrosion potential of the alloy is higher than that of the substrate, and the corrosion etching current of the alloy is improved, and internal alloy play a good protection。 The hardness (179。9HV) of this infiltrated al layer is about 1。5 times as much as that of the original magnesium alloy (70。5HV)。 The outer infiltrated layer is composed of

α-Al、β-Mg17Al12、Al3Mg2、α-Mg, and α-Al、Al3Mg2  mainly; the inner layer consists of

β-Mg17Al12、α-Al、α-Mg, and β-Mg17Al12、α-Mg mainly。

Key words: AZ91D magnesium alloy; thermal diffusion of aluminum; vacuum; corrosion resistance; hardness

目 录

第一章 绪论 1

1。1  镁及镁合金简介 1

1。1。1 镁资源分布 1

1。1。2 镁及镁合金优点 1

1。1。3 镁合金的应用 2

1。1。4 镁合金缺陷 4

1。2  镁及镁合金的腐蚀 4

1。2。1 腐蚀的基本概念和分类 4

1。2。2 镁及镁合金腐蚀特性 6

1。3  镁合金防护 6

1。3。1 降低镁合金内有害杂质元素含量 6