Slip systems, lattice rotations and dislocation boundaries

Plastic deformation by slip induces rotations of the crystallographic lattice and evolution of dislocation structures. Both lattice rotations and dislocation structures exhibit a dependence on the grain orientation, which reflects underlying relations to the slip pattern. Relations between the type of dislocation structure formed, in particular the crystallographic alignment of dislocation boundaries, and the slip pattern are demonstrated. These relations are applied to polycrystals deformed in tension and rolling, producing good agreement with experiment for rolling but less good agreement for tension. The grain orientations, for which the relations do not hold in tension, are also the grain orientations where the deviation between lattice rotations observed by three-dimensional X-ray diffraction (3DXRD) during tension deviate the most from those predicted with the Taylor model. The origin of these discrepancies is discussed. Finally, the implications of the relations between slip and dislocation structures for the modelling of mechanical properties are discussed.