Microstructural tomography of a superalloy using focused ion beam microscopy

A focused ion beam (FIB) microscope has been used to simultaneously depth profile and image the γ – γ ′ microstructure of a nickel base superalloy using normal incidence milling in order to characterize the precipitate microstructure in three dimensions (3D). The normal incidence milling rates of the γ and γ ′ phases in this alloy are closely matched when the orientation of the depth-profiled surface is near 〈 0 0 1 〉 , which allows for uniform material removal to depths up to a couple of microns. Depth-profiling experiments consisted of automated ion milling and collection of ion-generated secondary-electron images at specified intervals, and was demonstrated for a voxel resolution of roughly 15 × 15 × 16 nm 3 . Image-processing software was used for automated processing of the 2D image sequence to render the γ precipitate structure in 3D.