Thick plate rending of friction stir processed aluminum alloys

Friction stir processing (FSP) was used to modify the surface microstructure in thick plate 7050-T7451 aluminum to enhance room temperature bending. Plates, 254 x 216 x 50 mm thick, were friction stir processed on the pre-tensile surface to shallow and different depths (3.1 and 6.3 mm) using different approaches; i.e., the FSP raster included both linear and spiral patterns. Following FSP, plates were bent at room temperature to different degrees, including a compound curvature. Results illustrate the ability to significantly enhance room temperature formability via FSP. To illustrate the extreme capability of this technique, similar processing was applied to 150 mrn thick 6061 aluminum. In this case, FSP was applied to a depth of 25 mm, and this very thick plate bent to 30 degrees at room temperature without failure. Thick plate bending can be used to substitute for welding of corner structures or to shape plates for machining of a monolithic structure where a particular plate thickness is not available.