Understanding the probability of deformation transfer across grain boundaries is necessary for prediction of geometrical and stress conditions that lead to microcrack formation in grain boundaries of the intermetallic compound TiAl. To assist model development, grain boundary compatibility in gamma-gamma boundaries has been examined by studying the characteristics of grain boundaries at which cracks form or extensive deformation transfer is observed. The characterization of deformation defects and relative grain orientation has been accomplished through the use of selected area channeling patterns (SACPs) and electron channeling contrast imaging (ECCI) True grain orientations (including crystal tetragonality) are obtained via superlattice information available in the SACPs, while the use of ECCI allows the imaging of dislocations and deformation twins. The combination of these techniques allows trace analysis of the active deformation systems, which can be correlated to grain boundaries that display shear transmission and/or fracture initiation. A new approach to modeling deformation transfer is presented, based upon a hybrid of recent modeling approaches to multiscale interfacial mechanics to formulate a nonlinear variational model of plastic deformation in a bi-crystal.
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