Aspects of interphase boundary structure in diffusional phase transformations

Distinctions among fully coherent, partly coherent and incoherent interphas e boundaries are presented. Introduction of a single linear misfit compensa ting defect is concluded to represent the most useful definition of the tra nsition between fully and partly coherent interfaces. The limit between par tly and fully incoherent interphase boundaries is taken operationally as th e absence of detectable misfit accommodating defects (i.e., localization) a t the interface by high-resolution transmission electron microscopy. An ans wer to the question of whether or not a precipitate crystal can be fully or partly coherent at one or more boundary orientations and incoherent at oth ers is developed. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Sci ence Ltd. All rights reserved.