微弧氧化膜抑制高强铝合金氢致延迟开裂机理研究

The hydrogen induced delay cracking in humid air often occurs for high strength aluminum alloys during service, and it is very harmful to aerospace industry. In the present application, typical 7000 series high strength aluminum alloys are slected as the research object, and then the surface morphologies, microstructure, chemical compositions, coating thickness, coating-induced internal stress, hydrogen concentration in the sample, hydrogen induced local plastic deformation and the effect of micro-arc oxidation (MAO) coatings on the hydrogen induced delay cracking beahvior in humid air for high strength aluminum alloys will be investigated deeply and systematically using the modern analysis and testing methods such as MAO technique, slow strain rate tensile test (SSRT), hydrogen determinator, scanning electron microscope (SEM), transmission electron microscope（TEM）, X-ray diffractometer (XRD), and X-ray photoelectron spectroscope (XPS), etc. It will be confirmed that the MAO coatings restrain the hydrogen induced delay cracking in humid air for high strength aluminum alloys effectively. The relationship between the MAO coatings and hydrogen embrittlement susceptibility will be also discussed, hence it will be elucidated from the point of hydrogen permeation resistance of coating and coating-induced internal stress that the mechanism of MAO coatings restraining hydrogen induced delay cracking in high strength aluminum alloys. It is of very important scientific significance because the goal of the present application is to clarify the restraining role of MAO coatings formed on high strength aluminum alloys in the process of hydrogen induced delay cracking and its mechanism. Moreover, the present research may offer a theoretical basis for solving the issue of high susceptibility to hydrogen induced delay cracking constantly existing in high strength aluminum alloys, therefore, the present application is also of important actual significance.

高强铝合金在湿空气中服役时经常发生氢致延迟开裂，对航空工业危害极大。本申请以典型的7000系高强铝合金为研究对象，采用微弧氧化(MAO)技术、慢应变速率拉伸试验、定氢仪、扫描电镜（SEM）、透射电镜（TEM）、X射线衍射仪（XRD）及X射线光电子谱（XPS）等现代分析测试手段，深入系统地研究微弧氧化膜的表面形貌、显微组织、表面成分、膜厚、膜致内应力、试样中的氢浓度、氢促进局部塑性变形及其对高强铝合金氢致延迟开裂行为的影响，确认其对高强铝合金氢致延迟开裂的抑制作用，探讨其与氢脆敏感性之间的关系，并从膜阻氢渗透及膜致内应力的角度阐明微弧氧化膜抑制高强铝合金氢致延迟开裂的机理。由于本申请的目的旨在弄清微弧氧化膜对高强铝合金氢致延迟开裂的抑制作用和机理，因此具有重要的科学意义。此外，本申请的有关成果可能为解决高强铝合金一直存在的氢致延迟开裂敏感性高的问题提供理论基础，故本申请也具有重要的实际意义。

高强铝合金在湿空气中服役时经常发生氢致延迟开裂，对航空工业危害极大。为此，本项目以典型的7000系高强铝合金为研究对象，采用微弧氧化(MAO)技术、慢应变速率拉伸试验 、定氢仪、扫描电镜（SEM）、透射电镜（TEM）、X射线衍射仪（XRD）及X射线光电子谱 （XPS）等现代分析测试手段，深入系统地研究了微弧氧化膜的表面形貌、显微组织、表面成分、膜厚、膜致内应力、试样中的氢浓度、氢促进局部塑性变形及其对高强铝合金氢致延迟开裂行为的影响，确认其对高强铝合金氢致延迟开裂的抑制作用，探讨其与氢脆敏感性之间的关系，并从膜阻氢渗透及膜致内应力的角度阐明了微弧氧化膜抑制高强铝合金氢致延迟开裂的机理。主要结果如下：.(1).7050高强铝合金MAO陶瓷膜表面呈多孔状，且膜层的致密性、厚度与微弧氧化的电流密度、电压、氧化时间、电解液成分及浓度等因素密切相关。.(2).微弧氧化膜层主要是由α-Al2O3、γ-Al2O3组成。.(3).微弧氧化膜可以有效降低7050高强铝合金的氢致延迟开裂敏感性。.(4).微弧氧化膜可有效阻止氢渗透进入试样内部，且氢渗透浓度与微弧氧化膜层致密性相关。.(5).微弧氧化膜层产生的膜致应力均为压应力，对防止试样受到应力作用时发生断裂具有阻碍作用，能有效延迟裂纹的形核和运动，从而降低氢致延迟开裂的敏感性。.(6).微弧氧化膜对铝合金氢致局部塑性变形有明显抑制作用。