Electron backscattered diffraction (EBSD) is a technique regularly used to obtain crystallographic information from inorganic samples. When EBSD is acquired simultaneously with emitting diodes data, a sample can be thoroughly characterized both structurally and compositionally. For organic materials, coherent Kikuchi patterns do form when the electron beam interacts with crystalline material. However, such patterns tend to be weak due to the low average atomic number of organic materials. This is compounded by the fact that the patterns fade quickly and disappear completely once a critical electron dose is exceeded, inhibiting successful collection of EBSD maps from them. In this study, a new approach is presented that allows successful collection of EBSD maps from organic materials, here the extreme example of a hydrocarbon organic molecular thin film, and opens new avenues of characterization for crystalline organic materials.

The role of grain orientation and grain boundary misorientation on the formation of subcritical grain boundary cracks in creep of a conventionally cast nickel-based superalloy has been studied. The crystallographic orientations of the grains adjacent to grain boundaries normal to the tensile axis were measured using electron backscattered diffraction. The difference in the Schmid factor for the {111} ⟨112⟩ slip system between the grains was compared to the occurrence of grain boundary cracking. In addition, the difference in the amount of potential primary creep was calculated. The cracked grain boundaries were found to have a larger difference in Schmid factor, as well as a larger difference in potential primary creep, compared with uncracked grain boundaries.

Udimet 188 was subjected to thermomechanical processing (TMP) in an attempt to understand the effects of cold-rolling deformation on the microstructure and tensile-creep behavior. Commercially available sheet was cold rolled to varying amounts of deformation (between 5–35% reduction in sheet thickness) followed by a solution treatment at 1,464 K (1,191°C) for 1 h and subsequent air cooling. This sequence was repeated four times to induce a high-volume fraction of low-energy grain boundaries. The resultant microstructure was characterized using electron backscattered diffraction. The effect of the TMP treatment on the high-temperature [1,033–1,088 K (760–815°C)] creep behavior was evaluated. The measured creep stress exponents (6.0–6.8) suggested that dislocation creep was dominant at 1,033 K (760°C) for stresses ranging between 100–220 MPa. For stresses ranging between 25–100 MPa at 1,033 K (760°C), the stress exponents (2.3–2.8) suggested grain boundary sliding was dominant. A significant amount of grain boundary cracking was observed both on the surface and subsurface of deformed samples. To assess the mechanisms of crack nucleation, in situ scanning electron microscopy was performed during the elevated-temperature tensile-creep deformation. Cracking occurred preferentially along general high-angle grain boundaries (GHAB) and less than 25% of the cracks were found on low-angle grain boundaries (LAB) and coincident site lattice boundaries (CSLB). Creep rupture experiments were performed at T = 1,088 K (815°C) and σ = 165 MPa and the greatest average time-to-rupture was exhibited by the TMP sheet with the greatest fraction of LAB+CSLB. However, a clear correlation was not exhibited between the grain boundary character distribution and the minimum creep rates. The findings of this work suggest that although grain boundary engineering may be possible for this alloy, simply relating the fraction of grain boundary types to the creep resistance is not sufficient.