Discontinuous subgrain growth in deformed and annealed {110}<001> aluminium single crystals

Single-phase crystals of Al-0.05% Si of the Goss orientation {110}[001] have been deformed in channel die plane strain compression and found to be stable up to true strains of 3.0. The deformation microstructure contains neither long range orientation gradients nor heterogeneities and the crystals are resistant to recrystallization in the range 250-350 degrees C, although rapid recrystallization can be induced if the crystal surfaces are lightly abraded. During annealing it is found that whilst the general subgrain structure coarsens gradually, a few subgrains grow rapidly to diameters of over 100 mu m. Such discontinuous subgrain growth, which is topologically similar to primary recrystallization and abnormal grain growth has not previously been reported. It is shown that the rapidly growing subgrains are associated with slightly larger misorientations than the average subgrains. The origin of discontinuous subgrain growth is analyzed in terms of the orientation dependence of low angle boundary energies and mobilities.