The aim of this study is to consider the effect hydrogen on dezincification behavior of Cu-Zn alloys. The investigations include microstructural observations with scanning electron microscope and chemical composition analysis with energy dispersive spectrometer. The dezincification layer was found to occur in high pressure hydrogen atmosphere, not in air atmosphere. In addition, the layers penetrated into the inner side along the grain boundaries in the case of hydrogen condition. The shape of the dezincification layers was porous because of Zn dissolution from the α or β phase. In the case of stress corrosion cracks formed in the Cu-Zn microstructure, the dezincification phenomenon with porous voids was also accompanied by grain boundary cracking.
Extensive studies of the metastable structures in beta Ti alloys have investigated the ambiguity of the unstable phase. Their microstructural characteristics have been observed to have a modulated structure, and spot satellites of diffraction in TEM, however the formation mechanisms have not been successfully interpreted because of the resolution limit of the nano lattice structure. High resolution TEM was performed to observe the metastable nano structure and for analysis of the relationship between the nano lattice and spot satellites. A metastable structure was formed just before α precipitation by overlapping a new lattice onto the β matrix, inducing a modulated structure as a kind of Moire fringe. The new lattice structure of the 3a phase had 3 times the distance of the β lattice parameter and had lattice relationships with the β//3a phases of β(112)/(1100)/3a[⅓(112)] and β(222)/(1101)/3a[⅓(222)]. It was unreasonable to interpret the 3a phase as a definite precipitation of the phase, because only the limited zone axes of <113> and <110> were present in the TEM diffraction results of the metastable structures. Other zone axes, such as <100> or <111> etc., were not able to break the distinct metastable features of the spot satellites. Rather than precipitation, the 3a phase was activated by the slip of <113>/(112) and <110>/(112) in the TEM diffraction. It exhibited 3 times the distance of the β lattice parameter, which could not be achieved by typical precipitation.
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