Surface Characterization Methods to Evaluate Adhesive Bonding Performance of 6xxx Automotive Alloys

Abstract

6xxx series aluminum alloys are increasingly used within the automotive industry due to their lightweight potential. For assembling several joining techniques are common. This paper focuses on adhesive bonding, which is widely employed but its mechanism is by far not fully understood. The sheet metal process, including hot and cold rolling, solution heat treatment, pickling and Ti/Zr conversion treatment, contributes heavily to the final bonding performance. Even minor changes in the rolling process may alter the surface near deformation layer or a variation during pickling can lead to unfavorable oxidic conditions. To evaluate these changes X-ray photoelectron spectroscopy (XPS), which is extremely powerful in gathering elemental, chemical and oxidic information from the topmost surface (<10 nm), was performed. Furthermore, transmission transmission Kikuchi diffraction (TKD) in combination with a focused ion beam (FIB) preparation was employed to investigate the surface near grain structure near grain structure. Additionally, scanning electron microscopy (SEM) provided valuable knowledge concerning the surface topography.