Characterization of hydrogen defects forming during chemical charging in the aluminum

The behavior of hydrogen and deuterium in high-purity aluminum introduced by high-fugacity chemical techniques has been studied. The aims were to establish: (a) the presence of the hydrogen-vacancies clusters and bubbles formations, (b) their size and size distributions, (c) the symmetry of the clusters and the dependence of these parameters on the hydrogen charging conditions and on subsequent annealing procedures and (d) the kinetics of hydrogen release from these clusters and the structure of the remaining defects produced when the hydrogen is removed. The study was combined with a parallel series of experiments, which utilized secondary ion mass spectrometry (SIMS), X-ray techniques (Laue, small-angle X-ray scattering (SAXS), diffractometer measurements), transmission electron microscopy (TEM) and scanning electron microscope (SEM). The experiments revealed the existence of a large size distribution of hydrogen voids and bubbles on the surface and under the surface obtained during electrochemical and chemical charging. The depth of these defects was controlled by electrochemical and chemical charging conditions and depended on the charging time. Hydrogen nearly entered the aluminum lattice interstitially. A TEM technique revealed the existence of surface bubble from the interactions between the aluminum hydroxide with hydrogen and formed a hydrogen-vacancy complex at the surface, which diffused into the volume and then clustered to form H2 interior bubbles. A large size (some micrometers in the diameter) to very small sizes (nanometers in the diameter) in the distribution and variety in the density of the surface bubbles was obtained. Between the densely packed surface bubbles, formation of the dense dislocations could be seen. Internal bubble with symmetrical bend contours of the height and dense distributions of dislocations was observed.