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Measurements of Localized Ion Distribution and Nanoscopic AFM Observation of Crack Initiation and Propagation of Stress Corrosion Cracking

应力腐蚀裂纹萌生和扩展的局域离子分布测量和纳米级 AFM 观察

基本信息

批准号：
10650086
负责人：
MINOSHIMA Kohji
金额：
$ 2.24万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

In order to perform in situ observation of an initiation stage of corrosion damage including pitting corrosion and stress corrosion cracking, a so called chronoamperometric method was applied to localized corrosion damage, where a micron size Pt microelectrode (Diameter : 20 μm) is cyclically polarized by using a square waveform : local concentration of chloride ion and hydrogen ion, or pH values, can be respectively measured by using a current by an anodically and a cathodically polarized condition. By using this chronoamperometric method, distributions of chloride and hydrogen ion near a pitting corrosion was measured, at the bottom of which a stress corrosion crack sometimes initiates : the distributions of ions in and out of a corrosion pit was successfully measured, and the localization of ions around a pitting corrosion could be clearly visualized. In situ nanoscopic atomic force microscope (AFM) observation was also conducted to closely examine the growing process of stress corrosion cracking of a high-strength steel under a sustained loading : nanoscopic mechanism of stress corrosion cracking was discussed. Crack initiation and growth behavior was also investigated in a high-strength P/M Al-Zn-Mg alloy and a Ti-6Al-4V alloy under dynamic loading in order to clarify the environmental degradation behavior. Special attention was paid to the influence of combined loading on crack initiation and fracture behavior in a SiC whisker reinforced Al alloy.

为了对点蚀和应力腐蚀裂纹等腐蚀损伤的起始阶段进行原位观察，将计时电流法应用于局部腐蚀损伤，（直径：20 μm）通过使用方波进行循环极化：氯离子和氢离子的局部浓度或pH值可以分别通过使用阳极和阴极极化条件下的电流来测量。利用该计时电流法，测量了孔蚀附近的氯离子和氢离子的分布，孔蚀底部有时会产生应力腐蚀裂纹，成功地测量了孔蚀内外的离子分布，并能清晰地观察到孔蚀周围的离子分布。利用原子力显微镜（AFM）原位观察了高强度钢在持续载荷作用下的应力腐蚀裂纹扩展过程，探讨了应力腐蚀裂纹的纳米级机理。研究了高强度粉末冶金Al-Zn-Mg合金和Ti-6Al-4V合金在动态载荷下的裂纹萌生和扩展行为，以阐明其环境退化行为。研究了复合载荷对SiC晶须增强铝合金裂纹萌生和断裂行为的影响。