Elucidating Role of Strain and Dislocation Density on Abnormal Grain Growth in Ni by Dark Field X-ray Microscopy

The goal of this work is to use dark-field x-ray microscopy to evaluate the role of elastic strain and defect density on the persistence of abnormal grain growth (AGG) in nickel. Previously, AGG, in which a small fraction of grains grow much faster than the matrix, was observed in nickel with laboratory-based diffraction contrast tomography. Microstructural features such as curvature and grain size were not found to be predictors of such growth behavior. Even when a specimen is recrystallized and annealed, simulations suggest heterogeneous strain and strain-coupled grain boundary motion can cause preferred growth. In this study, the strain state will be compared in abnormal and normal growing grains. Furthermore, the abnormal grains will be mapped in situ to examine the role of line defects during discontinuous grain boundary migration. Therefore, DFXM will evaluate the role of strain in the persistence of AGG and general grain boundary migration in the absence of an applied stress.