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

先进金属材料对环境非常敏感，为了弄清材料在服役环境中的退化机理，提高材料的韧性，必须弄清材料中氢进入的过程以及氢陷阱的位置。在本研究计画中，发展了一种分析局部氢分布的方法：此方法是以银装饰技术为基础。研究得出以下结论，i）沉淀在样品上的银的量随着测试样品的氢含量的增加而增加，ii）该方法的灵敏度随着装饰溶液的pH值的降低而增加，iii）样品表面上的小颗粒银可以通过一种开尔文力显微镜来分析。（4）在样品表面镀上一层金属薄膜，大大提高了方法的灵敏度。重要的是， 关于我们 氢含量和样品表面上沉淀的银量。为此，从样品的一侧充入氢，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上沉淀的银量之间的良好一致性。这意味着，所开发的方法是有用的，以定量的方式分析氢的分布。调查还包括高强度钢的环境强度的评估：阴极充电条件下的裂纹扩展速率增加，断裂面成为穿晶。氢的热脱附行为和局部氢分布的分析表明，充氢主要吸附在晶粒内部，这与断口形貌一致。此外，在原位原子力显微镜分析的应力腐蚀裂纹的生长行为是依赖于局部的氢分布，这导致了加速和延迟的应力腐蚀裂纹的生长。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