HIGH RESOLUTION ELECTRON MICROSCOPY OF GRAIN BOUNDARIES IN fcc AND bcc METALS

Abstract
HREM observation of small and high angle boundaries was performed in gold and iron in order to assess the influence of the crystal structure. A small angle boundary consisting of dislocation arrays was usually inclined with respect to the foil surface. High angle boundaries were mostly vertical. Atomic structure of the ordered boundary did not agree with details of the geometrical model. Lattice relaxation was evident at the boundary. The regularity of atomic structure of CSL boundary decreased with increasing the missorientation from the perfect CSL orientation relationship. A low indices crystal plane was frequently parallel to the boundary plane in both fcc gold and bcc iron. The plane matching boundary was abundant at, or near, the rotation angle of high sigma CSL boundary in iron.