On the Effect of Creep on Local Lattice Orientation in Single‐Crystal Ni‐Based Superalloy Microstructures

In the present work, we use electron backscatter diffraction (EBSD) in the scanning electron microscope (SEM) to study the evolution of local misorientations in the γ / γ ′ microstructure of a single‐crystal Ni‐based superalloy after exposures to creep conditions in the high temperature and low stress field. Sampling fields of statistically relevant dimensions were evaluated (16 × 12 µm 2 , corresponding to almost 1000 γ′ particles in the initial state). We apply a new method that allows for differentiation between diffraction signals from γ and γ′ phase regions. The spatial relationships between locations where misorientation accumulation occurs are investigated for dendritic and interdendritic regions loaded along the [001] and [110] crystallographic directions. Increases in intra‐ and interphase misorientation are observed as dislocation density increases, then saturates. The higher dislocation densities in γ channels than in γ ′ particles seen by transmission electron microscopy are shown to be statistically stored on the micron size scale. Geometrically necessary misorientations are observed to cancel each other out over the macroscopic scale, resulting in no detectable macroscopic change in crystal orientation for total accumulated plastic strains of 6%. The limitations of the methods are discussed, and areas in need of further work are highlighted.