An interface consisting of an antiphase boundary and a short-range-ordering interphase layer (4nm) in the elongated γ′ precipitate for a chosen model alloy was examined. Interface image simulations, high-resolution electron microscopy, and scanning transmission electron microscopy techniques were employed to show interfacial segregation at an antiphase boundary and to identify the local composition changes across it. Emphasis was also given to understanding the influence of the antiphase boundary on the microstructural evolution in the rafting mechanism. In contrast to the widely accepted notion that out-of-phase precipitates never coalesce to form a single particle, results of this study indicate that complete coalescence of γ′ precipitates during annealing may occur at high temperatures as a result of the glide and climb of a ½<110> super-partial dislocation in the thin interphase layer, despite the presence of an antiphase boundary between the merging γ′ particles.

Interfacial Segregation and Influence of Antiphase Boundaries on Rafting in a γ/γ′ Alloy. C.Y.Chen, W.M.Stobbs: Metallurgical and Materials Transactions A, 2004, 35[3], 733-40