Antiphase boundaries in D03 long-range ordered samples were studied by means of transmission electron microscopy. It was found that the antiphase boundaries gave rise to diffraction contrast, not only in the superlattice reflections but also in the fundamental ones. This indicated that the total fault displacement across the antiphase boundaries was not exactly equal to the basic displacement, but instead involved an additional one. The basic displacement was either ¼<111> for the nearest-neighbor antiphase boundaries, or ½<111> for the next-nearest neighbor antiphase boundaries. The basic displacement was responsible for the normal strong antiphase boundary contrast when imaged with superlattice reflections. An anomalous antiphase boundary contrast during imaging with fundamental reflections could be attributed to the additional non-crystallographic displacement. The antiphase boundary contrast which was caused by the latter displacement was generally weak and asymmetrical in dark-field images. Whereas the nearest-neighbor antiphase boundaries were clearly visible when imaged using fundamental reflections, the next-nearest neighbor antiphase boundaries gave no observable anomalous contrast. The additional displacement was therefore dependent upon the basic displacement. Its magnitude was smaller for ½<111> than for ¼<111>. The direction of the additional displacement across the nearest-neighbor antiphase boundary varied with the orientation of the domain boundaries. The main component of the fault vector was perpendicular to the fault plane. The nearest-neighbor antiphase boundary was of extrinsic character. The lattice near to the antiphase boundary was dilated.

TEM Investigations of the Structure of Antiphase Boundaries in D03 Ordered Fe3Al. W.Liu, H.Rosner, E.Langmaack, A.Gemperle, J.Gemperlova, J.Pesicka, E.Nembach: Materials Science and Engineering A, 1998, 258[1-2], 15-9