| Abstract Scope |
The study focuses on the dislocation structure evolution in surface and interior grain of pure Ni in the absence and presence of hydrogen. By combining EBSD and FIB lift-out techniques, electron-transparent foil at orientation of interest was obtained. The dislocation structure was observed at diffraction-contrast imaging condition in STEM. Diverged from the well-established dislocation pattern evolution theory, in the presence of hydrogen, the predominant dislocation structure type in surface grain was found to be always dislocation cell, which was independent of orientation. At the same strain level, the observations also indicated hydrogen has no significant effect on the size of surface dislocation cell. However, in the interior grain, hydrogen-accelerated evolution of the dislocation structure was evident. The results are attributed to different evolution process for dislocation structure in the surface and interior grains, and the hydrogen effect on surface and interior of material are discussed based on dislocation-hydrogen interaction theory. |