Nano γ′/γ composite precipitates in Alloy 718

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 gamma' and gamma '' 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 gamma' and gamma '') has an elastic energy that is significantly lower than, for example, single gamma' and gamma '' precipitates which are non-interacting. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4721456]