Investigation into the Degradation Mechanisms of Advanced Metallic Materials based upon Localized Hydrogen Distribution Analyses

先进的金属材料对环境非常敏感，为了弄清金属材料在使用环境中的降解机理，提高金属材料的韧性，必须弄清材料中氢的进入过程和氢阱的位置。在本研究项目中，开发了一种分析局部氢分布的方法：该方法基于银装饰技术。研究得出以下结论：1)样品上银的析出量随着样品中氢含量的增加而增加；2)该方法的灵敏度随着装饰溶液pH值的降低而增加；3)样品表面的小银颗粒可以通过一种开尔文力显微镜进行分析。iV)在样品表面涂覆一种金属薄膜，极大地提高了方法的灵敏度。更重要的是，氢的含量与样品表面银的析出量之间的关系。为此，从样品的一侧给氢充电，在样品的另一侧检测穿过样品的氢。这表明渗透氢电流或样品的氢含量与样品表面的银沉淀量之间有很好的一致性。这意味着该方法可用于定量分析氢的分布。研究还包括对高强度钢的环境强度的评价：在带阴极的条件下，裂纹扩展速度加快，断口呈穿晶状。对局部氢分布和氢的热解吸行为的分析表明，带电氢主要在晶粒内被吸收，这与断口表面形貌相一致。此外，对应力腐蚀裂纹扩展的原位AFM分析表明，裂纹的扩展行为依赖于局部氢的分布，这导致了应力腐蚀裂纹扩展的加速和延迟。少

Advanced metallic materials are sensitive to an environment and in order to clarify the degradation mechanisms and to improve the toughness of the metallic materials in a service environment, we must clarify the process of hydrogen entry as well as the hydrogen trap sites in the material. In this research project, a method to analyze the localized hydrogen distribution has been developed: the method is based upon a silver decoration technique. The investigation yields the following conclusions, i) An amount of silver precipitated on a sample is increased with an increase in a hydrogen content of the test sample, ii) The sensitivity of the method is increased with a decrease in the pH value of the decoration solution, iii) A small particle of silver on the sample surface can be analyzed by a kind of a Kelvin force microscope. iV) The sensitivity of the method is extremely improved by coating a kind of metallic thin film on the sample surface. The important thing is the correlation betwe … More en the hydrogen content and the amount of the precipitated silver on the sample surface. For this purpose, the hydrogen was charged from the one side of the sample, and the hydrogen which passed through the sample was detected on the other side of the sample. This shows a good agreement between the permeated hydrogen current or the hydrogen content of the sample and the amount of precipitated silver on the sample surface. This means that the developed method is useful to analyze the hydrogen distribution in a quantitative manner. The investigation also includes the evaluation of the environmental strength of a high-strength steel: the crack growth rate is increased under a cathodically charged condition, and the fracture surface became transgranular. The analyses of the localized hydrogen distribution as well as the thermal desorption behavior of hydrogen show that the charged hydrogen is mainly absorbed within a grain, and this agrees with the fracture surface morphology. Moreover, in situ AFM analyses of a growing stress corrosion crack show that the growth behavior is dependent on the localized hydrogen distribution, and this caused an acceleration and retardation of a stress corrosion crack growth. Less