Effect of grain orientation on deformation structure in cold-rolled polycrystalline aluminium

Pure (99.996%) polycrystalline aluminium (grain size about 300μm) has been cold-rolled to reductions in the range from 5 to 50% (εvm=0.06–0.80) and the deformation microstructure has been analysed by TEM in a large number of grains. The deformation microstructure is subdivided by dislocation boundaries having different characteristics depending on the orientation of the deformed grain.

An analysis of the dislocation boundaries based on Frank's formula shows that the majority of the dislocations in the boundaries originate from active slip systems predicted by a Schmid factor analysis. Thereby a link is created between the microstructural evolution and the macroscopic plastic behaviour.

The boundary parameters have also been used in a calculation of the dislocation density and the stored energy for grains of different orientations. These calculations together with measurements of the angular misorientation distribution shows that microstructural differences caused by differences in grain orientation are enhanced as the strain is increased.