Textural evolution and spatial distribution in AA6111-T4 automotive body sheet

A non-isotropic spatial distribution or banding of textural components develops in Al-Mg-Si-(Cu) sheet, such as AA6111, during its production. These bands of similarly oriented grains undergo rotation at the free surface during subsequent forming operations, resulting in a unique pattern of `orange peel' that manifests itself as a series of fine ridges in the rolling direction approximately 0.1 mm high. Despite their small dimension, these ridges are readily visible, even in products that are subsequently painted after forming, and constitute a visible surface defect that is objectionable on exterior automotive components. Eliminating the condition not only results in an improved surface appearance, but also reduces the textural anisotropy of the sheet, which improves formability. The texture evolution, the spatial distribution of the textural components, and the textural effects on 6111 sheet formability will be discussed.