The effect of roll gap geometry on microstructure in cold-rolled aluminum

Microstructure and texture are analyzed through the thickness of two aluminum plates cold-rolled 40% with different roll gap geometries. It is found that both texture and microstructure are strongly affected by the rolling geometry. After rolling with intermediate-size draughts a rolling-type texture is developed throughout the plate thickness. In this case, grains are subdivided by extended planar dislocation boundaries preferentially aligned at an angle of 40 +/- 15degrees to the rolling direction. In the plate rolled with small draughts, shear texture components appear in the intermediate layers. In these layers, extended planar dislocation boundaries are frequently found to be inclined closely to the rolling direction. The subsurface and central layers of this plate exhibit microstructures similar to those in the plate rolled with intermediate draughts. It is suggested that the development of different textures and microstructures at different depths is related to the activation of different slip systems due to through-thickness strain gradients.