Disclination models for misorientation band generation and development

Disclination models for misorientation band (MB) generation at grain boundary faults such as boundary kinks and junctions are considered. The models operate with wedge disclination dipole and quadrupole configurations and predict the existence of a critical external shear stress tau(c) for MB nucleation event to take place. The numerical estimates for cc give the values of order G/1000 (G being shear modulus) which are in a good agreement with typical values for applied stresses at the end of Stage II of deformation curves for BCC and FCC metals. The critical stress tau(c) is shown to be strongly dependent on the geometry and strengths of initial disclinations at grain boundary faults. Additionally tau(c) is found to be proportional to the effective surface energy gamma of misorientation boundaries of a MB. The further development of MBs demonstrates two main regimes of their propagation: stable and unstable propagation. The transition between above two regimes of MB propagation is controlled by the other critical value for external stress tau(p), which is also proportional to surface energy gamma.