DISCONTINUOUS SUBGRAIN GROWTH IN DEFORMED AND ANNEALED (110)[001]ALUMINUM 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 microstructur e contains neither long range orientation gradients nor heterogeneitie s 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 th at whilst the general subgrain structure coarsens gradually, a few sub grains grow rapidly to diameters of over 100 mu m. Such discontinuous subgrain growth, which is topologically similar to primary recrystalli zation and abnormal grain growth has not previously been reported. It is shown that the rapidly growing subgrains are associated with slight ly larger misorientations than the average subgrains. The origin of di scontinuous subgrain growth is analyzed in terms of the orientation de pendence of low angle boundary energies and mobilities.