High-resolution transmission electron microscopy observations and atomic simulations of the structures of exact and near Sigma=11, {332} tilt grain boundaries in nickel

A Sigma = 11, {332} nickel bicrystal was grown by solidification. The aim o f this paper is to show the evolution of the grain-boundary (GB) structure depending upon the position in the bicrystal of the extracted sample. Conve ntional transmission electron microscopy and high-resolution transmission e lectron microscopy (HRTEM) observations were used to characterize the GBs o n microscopic and nanoscopic scales respectively. The detailed atomic struc tures of the exact {332} and the asymmetrical {111}parallel to{331} GBs wer e investigated by numerical calculations and compared with the HRTEM images . There is a perfect agreement between the calculated and the experimental image for the symmetrical (332) GB at the head of the bicrystal. The high G B defect density in the asymmetrical GBs at the end of the bicrystal makes the comparison less straightforward. It is, however, noteworthy that two co mplete periods of the calculated structure are actually observed in the exp erimental image. In order to approach the atomic description of the {111}(1 )parallel to{hkl}(2) asymmetrical tilt GBs, it is proposed to use for each side the structural units which appear in the corresponding symmetrical (11 1) and hkl tilt GBs respectively.