1 Department of Mechanical Engineering, Technical University of Denmark2 Materials and Surface Engineering, Department of Mechanical Engineering, Technical University of Denmark3 Department of Photonics Engineering, Technical University of Denmark4 Optical Microsensors and Micromaterials, Department of Photonics Engineering, Technical University of Denmark5 Centre National de la Recherche Scientifique6 Danish Technological Institute7 Centre for oil and gas – DTU, Center, Technical University of Denmark8 Danish Technological Institute
Anodized Al alloy components are extensively used in various applications like architectural, decorative and automobiles for corrosion protection and/or decorative optical appearance. However, tailoring the anodized layer for specific optical appearance is limited due to variation in composition and microstructure of the commercial alloys, and even more difficult with recycled alloys. Sputter coating methods promise to control the chemical composition of the Al alloy surfaces and eventually modify the microstructure of the surfaces with heat treatments thus enabling the freedom on the substrate quality. This paper evaluates the use of magnetron sputtered Al-Zr coatings on Al combined with heat treatment and anodizing for obtaining required optical properties. Metallurgical and optical characterization was carried out to investigate the effect of coating microstructure and anodizing parameters on appearance of the anodized layer. The microstructure of the coating is found to influence the appearance of anodized layer owing to the presence of completely or partially dissolved second phases during anodizing process. Oxidation status of the second phase particles in the coatings affected the light absorption and scattering phenomenon there by imparting different appearances to the anodized alloy surfaces.