Multi-alloy Aluminum Tubing via Shear Assisted Processing and Extrusion

To promote lightweighting of automotive structures, there is a need for new processing techniques that create a variation in properties within a single component. Such customization would enable optimization of mechanical properties such as strength, ductility, and stiffness thereby reducing the need to specify a material or gage thickness on one region that is not needed in another. To this end, Shear Assisted Processing and Extrusion (ShAPE) was used to fabricate thin-walled tubing having a gradient in alloy composition, and thus performance, along the length. Tubes that transition from alloy 6061, to 7075, and back to 6061 have been extruded with an outer diameter of 12 mm and wall thickness of 1 mm. Bonding between the alloys appeared relatively sound based on optical micrographs, and few defects were observed using X-ray computed tomography. Very little mixing between the alloys were observed, and the interface between them was very sharp. Hardness in the transition region was nearly identical to the base material, further confirming lack of mixing. Additionally, this work represents the first known thermomechanical processing technique whereby alloy 7075 has been joined without creating a weakened heat-affected zone.