Papers by Keyword: Environmental Hydrogen

Abstract: Hydrogen embrittlement has been known to occur by invading hydrogen (environmental hydrogen) in some metallic materials under several certain conditions, although the cause has not been clarified yet. To clarify the cause, investigations on the behavior of environmental hydrogen in metallic materials are needed. It has been reported that environmental hydrogen invades 7075 aluminum alloy through the second-phase particles (Al₇Cu₂Fe). However it has not been clarified yet whether environmental hydrogen invades aluminum through the interface between the matrix and second-phase or through the bulk of second-phase particles. In this study, tritium autoradiography technique, TARG, has been applied to an aluminum alloy containing a single kind of second-phase particles (Al₇Cu₂Fe), to elucidate the invasion behavior of hydrogen from two different environments: tritiated water and tritium gas. In TARG, hydrogen (tritium) atoms that stay in the vicinity of the surface can be detected as silver particles. Silver particles (hydrogen atoms) were primarily detected on the interface between the matrix and second-phase. Thus most of the invading hydrogen is concluded to be trapped by the interface.

Abstract: In recent years, the use of hydrogen as a clean energy has been paid attention to in terms of the prevention of global warming. Tanks composed solely of steel and cylinders consisting of aluminum liner reinforced with C-FRP in the surrounding are used to store high-pressure hydrogen gas in hydrogen stations and in fuel cell vehicles, respectively. On the other hand, hydrogen embrittlement has been known to occur in some metallic materials under several certain conditions. Also, it has been generally known that the environmental hydrogen that invades the material during services plays major role in hydrogen embrittlement. For this reason, investigations on the behavior of environmental hydrogen in metallic materials are needed. In this study, the behavior of environmental hydrogen in pure aluminum, 6061 aluminum alloy and 7075 aluminum alloy has been investigated by means of tritium autoradiography.

Abstract: High-magnesium Al-Mg alloys are known to be sensitive to stress corrosion cracking involving environmental hydrogen, hydrogen invading from the corrosive environment. In this study, the behavior of the environmental hydrogen in Al-6%Mg and Al-8%Mg binary alloy sheets stretched by 10% during exposure to 3.5%NaCl solution has been investigated by means of hydrogen microprint technique. Microprint image is observed on one surface while the other surface is exposed to the solution. In both alloys, the silver particles corresponding to the sites where hydrogen atoms are emitted from the inside of the sheets are shown on the slip lines. It is shown that the hydrogen atoms are transported with moving dislocations in the alloys.