A disclination-based model for grain subdivision

Grain subdivision under cold rolling of fcc polycrystals is modelled by formulating evolution equations for the statistically stored dislocation densities (cell structure), the propagating partial disclination dipole densities, and the immobile partial disclination densities (cell block structure) at the slip system level. The development of the mean cell and cell block sizes and of the mean misorientations across the cell block boundaries (cbb) is predicted for several grain orientations. Two types of grain subdivision were distinguished, cube, rolling direction (RD)- and transverse direction (TD)-rotated cube oriented grains showed a finer subdivision and nearly no spread of misorientation between the cbb families, while Goss, brass and S-oriented grains showed a coarser subdivision and a significant spread of the misorientations. Copper oriented grains exhibit an intermediate behaviour. The predictions of the model for the evolution of the cell and cell block sizes are in reasonable agreement with experimental results.