Effect of Different Heat Treatments on Surface Microstruc-tures and Anodic Oxide Film Structures of Al-5.6Mg Alloy Sheets

Abstract:

The effect of different intermediate annealing heat treatments on the surface microstructures and anodic oxide film structures of rolled Al-5.6Mg sheets was studied. The results show that when the continuous annealing is used to control microstructures of the sheets instead of the static state annealing in the intermediate annealing process, the surface grain size of the sheets can be reduced by about 65.7%, and the size of the Mg precipitation phase (Mg₂Al₃) can be reduced by about 67%. Under the combined influence of grain size, precipitation phase, and texture, the highest glossiness can be obtained, which is attributed to continuous intermediate annealing and stabilization annealing at low temperature. The uniform grain and precipitation structures is beneficial to reducing the inhomogeneous dissolution of the oxide film and to obtain the anodic oxide film with uniform thickness and high glossiness.