Texture and Microstructure Control of Al-Mg-Si Alloy Sheet by Differential Speed Rolling

It is known that well developed //ND texture increases Lankford value (r-value) of not only bcc metals but also fcc metals and alloys. However, //ND texture cannot be formed in fcc metals by conventional rolling and annealing processes. The //ND orientation is one of the major components of shear texture. Accordingly, this orientation develops in aluminum sheet when shear deformation is introduced. Al-Mg-Si alloy 6016 sheet was processed by two-pass differential speed rolling at room temperature under a high friction conditions. The rolling direction of the second pass was so selected that the direction of shear deformation introduced in the second pass was either similar (unidirectional shear rolling) to or opposite (reverse shear rolling) to that in the first pass. The roll speed ratio was 2.0. Large shear strain was successfully introduced through the thickness uniformly by the differential speed rolling. The shear texture with major components of {001} and {111} were developed throughout the thickness. Though large reduction in thickness of 75% was applied to the sheets by the rolling, conventional rolling texture such as {112} or {123} orientation was not detected in any part of the thickness. By solution treatment after the rolling, intensity of shear texture weakened and grain size decreased. It has been found that r-value is improved by the differential speed rolling subsequently followed by solution treatment.