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

A Sigma = 11, {332} nickel bicrystal was grown by solidification. The aim of this paper is to show the evolution of the grain-boundary (GB) structure depending upon the position in the bicrystal of the extracted sample. Conventional transmission electron microscopy and high-resolution transmission electron microscopy (HRTEM) observations were used to characterize the GBs on microscopic and nanoscopic scales respectively. The detailed atomic structures of the exact {332} and the asymmetrical {111}parallel to{331} GBs were 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 GB defect density in the asymmetrical GBs at the end of the bicrystal makes the comparison less straightforward. It is, however, noteworthy that two complete periods of the calculated structure are actually observed in the experimental 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 (111) and hkl tilt GBs respectively.