Orientations of recrystallization nuclei developed in columnar-grained Ni at triple junctions and a high-angle grain boundary

A directionally solidified, high-purity nickel sample with a strong 〈0 0 1〉 fiber texture was cold rolled to 40% reduction. Electron backscattered diffraction (EBSD) was used to identify triple junctions (grain edges) before annealing the sample at 430 °C, after which further EBSD was performed to identify 17 recrystallization nuclei at the initially characterized triple junctions on the rolling plane. In addition, a longitudinal section was cut on which a further seven recrystallization nuclei were found and characterized. This characterization of all nuclei revealed that the majority of nuclei could be broadly associated with a 40° 〈1 1 1〉 misorientation to the matrix in which they formed, while a much lower percentage were found to have orientations as those of the local deformation substructure. However, a substantial fraction (around one-third) could not be associated with either of these types. Mechanisms for the formation of nuclei with new orientations are discussed, as is evidence of reorientation of material ahead of the recrystallization front.