| dc.description.abstract | The pore formation in anodization processes was complex and draw many scholars to present different models for discussion; mainly concerning the transient development of anodic alumina oxide film (AAO film). These models included “Joule heat”, “Field-assisted dissolution”, “Water-dissolution” and “Stress driven oxide flow”, etc. Recently, a model called “Oxygen bubble mould effect” was presented and published. It described that oxygen bubble could generate the hemi spherical structure on anodic alumina matrix.
This study proposed a new interpretation about the pore formation in the anodic alumina film with sulfuric acid solution. We calculated the electric stresses acting on oxygen bubble interface, and describde how the oxygen bubble evolved during the anodizing process. Effects of different anodizing parameters, such as current densities and electrolytic temperatures, on anodic behavior were further discussed. All discussions were based upon experimental results; including the microstructures of AAO film, voltage-time curve, anti-corrosion and optical properties of different 7000 series aluminum alloys. Processing parameters included degree of deformation (0%, 5% and 10%) and different heat treatments (T5, T6, T7 and T73).
This study used a software called “COMSOL” to simulate electrical strength around a cavity. Cross sections of anodized samples were observed by transmission microscope. The electric stresses acting on the interface of an oxygen bubble was computed and highlight its magnitude under different parameters (293K, 1.2 A/dm2、283K，1.5 A/dm2、303K, 1.5 A/dm2 and 293K, 1.8 A/dm2). The voltage-time (V-T) curveused to distinguish t different growing stages. Experiments were also conducte to study the microstructure, physical properties, anti-corrosion and optical properties of AA7005-T7、AA7075-T5、AA7075-T6 and AA7075-T73 samples affected by different degress of cold rolling. | en_US |