Pattern formation in dislocation sub-structures

A variety of dislocation sub-structures associated with plastic deformation ranging from dipole clusters to dislocation cells have been documented over the years. Using perturbation analysis techniques, it is possible to simulate the spatial arrangement of the dislocation species, which provides an insight into the mechanisms controlling the evolution of dislocation substructures. A specific case of NiAl single crystals subjected to LCF (low cycle fatigue) has been considered to demonstrate the formation of dislocation patterns. A stress assisted diffusion mechanism that gives rise to the pattern is considered and the microstructure is simulated. The simulation is found to be in agreement with the experimental micrographs, thus providing evidence for the mechanism to be active in the material during low cycle fatigue.