Microscopie à haute résolution d'une interface semi-cohérente phase µ/matrice γ-γ'

Abstract
Among different orientation relationships between rhomboedral µ precipitates and the γ-γ' two-phase medium of a nickel base superalloy, one is found appropriate for the observation of the heterointerface by high resolution electron microscopy. Misfit dislocations (MD's) are observed, associated with interfacial ledges. They accommodate a 0.6 % length misfit and a small long range angular departure equal to 1.9° between the planes (542)µ and (113)γ'.The relative position of the crystals along the interface facets has been determined, as well as the common Burgers vector of the MD's. A computer analysis of a MD image, observed at near-atomic scale, demonstrates that the experimental elastic displacement field of the surrounding atomic columns is in good agreement with the dislocation-ledge theory developed by the authors (Phys. Rev. Lett., 1992, 69, 104-107).