Interfacial segregation and influence of antiphase boundaries on rafting in a γ/γ, alloy

An interface consisting of an antiphase boundary (APB) and a short-range-ordering interphase layer (similar to4 nm) in the elongated gamma' precipitate for a chosen model alloy was examined. Interface image simulations, high-resolution electron microscopy (HREM), and scanning transmission electron microscopy (STEM) techniques were employed to show interfacial segregation at an APB and to identify the local composition changes across it. Emphasis is also given to understanding the influence of the APB 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 gamma' precipitates during annealing may occur at high temperatures as a result of the glide and climb of a 1/2 <110> superpartial dislocation in the thin interphase layer, despite the presence of an APB between the merging gamma' particles.