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很敏感，为了弄清金属材料在使用环境中的退化机理和提高其韧性，必须弄清氢进入材料的过程以及材料中的氢陷阱位置。在本研究项目中，发展了一种分析局域氢分布的方法：该方法基于银装饰技术。研究结果表明：1)样品上的银量随样品中氢含量的增加而增加；2)方法的灵敏度随装饰液pH值的降低而增加；3)样品表面的小颗粒银可用开尔文力显微镜进行分析。4)在样品表面涂覆一层金属薄膜，大大提高了方法的灵敏度。重要的是…之间的相关性更重要的是氢含量和样品表面的沉淀银的数量。为此，氢气从样品的一侧充电，穿过样品的氢气在样品的另一侧被检测到。这表明渗透氢电流或样品的氢含量与样品表面的沉淀银的量有很好的一致性。这意味着所开发的方法对于定量分析氢的分布是有用的。研究还包括对一种高强度钢的环境强度进行评估：在阴极充电条件下，裂纹扩展速度加快，断口表面变为穿晶。氢的局域化分布和热脱附行为的分析表明，带电的氢主要吸附在颗粒内，这与断口形貌相吻合。此外，对扩展应力腐蚀裂纹的原位AFM分析表明，扩展行为依赖于局域氢的分布，这导致了应力腐蚀裂纹扩展的加速和延缓。较少

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