New orientation formation during recrystallization of cold deformed, high symmetry aluminium bicrystals

The crystallography of recrystallization nucleation has been investigated in channel-die deformed pure Al bicrystals with {100} (011) / {110 } (001), {100}(001)/{110}(011) and {100}(001)/11101(001) orientations. The new grain orientations and misorientations were followed by systematic local orientation measurements using SEM and semi-automatic measurements in TEM. The bicrystals were cold deformed by channel-die compression up to true strains of 1.5. During recrystallization annealing, the deformation bands of unstable orientations are the privileged sites for the formation of new grains. These nuclei were misoriented with respect to the orientations identified within the neighbouring deformed areas by a( (111), (112) or (100)) relations. Grain boundary migration and 'consumption' of the as-deformed areas was always favoured along directions parallel to the traces of the 11111 slip planes that had been most active during deformation as shown in the stable and structurally homogeneous Goss {110} (001) oriented grains. At logarithmic strains below 1-1.5 the grain boundary does not seem to be a specific nucleation site of new grains.