LARGE-STRAIN DEFORMATION STRUCTURES IN ALUMINUM CRYSTALS WITH ROLLING TEXTURE ORIENTATIONS

Four single crystal orientations of high purity aluminium have been deformed in channel die compression up to strains of approximately 1 to correlate the dislocation substructures, in single and polycrystals with the slip system distribution. Three orientations are close to the stable rolling texture components of fcc metals: (110)[112BAR], (112)[111BAR] and (112)[174BAR] and one is very unstable (121)[311BAR]. The substructures are characterized on the longitudinal section over a wide range of scales by optical microscopy. TEM and SEM with EBSD. Low energy dislocation matrix structures composed of cells, cell blocks, dense dislocation walls and first generation microbands are observed in all orientations in agreement with the microstructures of rolled polycrystals. The S (213)[142BAR] and C (112)[111BAR] orientations also develop narrow bands of localized glide associated with relatively high local misorientations. The S orientation exhibits characteristic S-shaped band structures of first generation microbands sheared on {111} planes whereas the C orientation forms non-crystallographic shear bands. These two orientations can be considered stable in terms of average texture but unstable in terms of microstructure.