Surface Studies on Industrial Aluminium Alloys

Abstract: Aluminium alloys are used in a wide range of applications due to their high tensile strength concomitant with low density. Additionally, aluminium alloys form a naturally occurring and passivating oxide layer, which leads to high corrosion and weathering resistance. In industrial manufacturing, aluminium alloys acquire their desired properties through specially designed heating processes. A common method to join aluminium work pieces together is brazing. The work pieces designed for brazing applications are coated with an aluminium alloy, which has a lower melting point as the base material. During brazing the top alloy is molten and the covering oxide layer needs to be broken up to achieve a strong and durable connection between the work pieces. This thesis present how temperature treatment affectss the surface layer of two different aluminium alloys. The processes taking place during heat treatment were studied by a combination of microscopy and spectroscopy techniques. Both alloys were heated in an UHV chamber and characterized after subsequent heating by using different operational modes of the SPELEEM (Spectroscopic PhotoEmission and Low Energy Electron Microscope). The SPELEEM is situated at beamline I311 at the MAX II storage ring at the national Swedish synchrotron radiation facility, MAX IV Laboratory. The operation modes of the SPELEEM that were used for this study are MEM (Mirror Electron Microscopy), XPEEM (X-ray PhotoEmission Electron Microscopy) and XPS (X-ray Photoelectron Spectroscopy). In addition, the samples were examined by SEM (Scanning Electron Microscopy) before and after the heat treatment. Using the above described combination of different surface science techniques, the changes occurring upon heat treatment at the aluminium-magnesium-silicon alloy 6063 surface were studied at room temperature and after heating to 300°C and 400°C. The aluminium alloy used in brazing applications was studied at higher temperatures up to 500°C to follow the decomposition of the aluminium oxide layer. Using the previously mentioned techniques allows to follow the diffusion, reactions and sublimation of the different elements.