Unusual through-thickness variations of microstructure and texture in heavily rolled and annealed Al–0.3%Cu

The evolution of microstructure and texture has been investigated in coarse-grained Al–0.3%Cu subjected to 98% cold rolling and subsequent annealing for 1 h at temperatures up to 300 °C. In the rolled material the distribution of crystallographic orientations is found to be highly non-uniform through the sample thickness, with the center layer being strongly dominated by the Bs component, whereas no single texture component dominates in the subsurface. The rolled microstructure contains lamellar structures and a large number of shear bands in all layers. The shear bands promote nucleation of Goss-oriented and other grains in the center layer. Most grains nucleated in the subsurface have random orientations. In the fully recrystallized microstructure obtained after annealing at 225 °C for 1 h, a strong Goss texture is formed in the center layer, while random orientations constitute the greatest area fraction of all orientations in the subsurface. Grain growth taking place after complete recrystallization at 250 °C and 300 °C leads to unusually high fractions of the Goss texture and high fractions of low angle boundaries in the center layer. In the subsurface layers, grain growth results in increased fractions of random orientations, and consequently most grain boundaries in these layers are high angle boundaries. The sample annealed at 300 °C for 1 h exhibits a pronounced sandwich-type structure, with a Goss-oriented band in the center layer enclosed by subsurface layers containing coarser grains of many different orientations.