Nano <i>γ′/γ</i>″ composite precipitates in Alloy 718

Abstract

Nanoscale composite precipitates of Alloy 718 have been investigated with both high-resolution scanning transmission electron microscopy and phase field modeling. Chemical analysis via energy-dispersive x-ray spectroscopy allowed for the differentiation of γ′ and γ″ particles, which is not otherwise possible through traditional Z-contrast methods. Phase field modeling was applied to determine the stress distribution and elastic interaction around and between the particles, respectively, and it was determined that a composite particle (of both γ′ and γ″) has an elastic energy that is significantly lower than, for example, single γ′ and γ″ precipitates which are non-interacting.