Study On Thermal Performance Of The Anodic Oxide Film On Aluminum Alloy Surface

Aluminum alloy has a lot of characteristics that high strength-to-weight ratio, thermalconductivity, electrical conductivity, excellent resistance to atmospheric corrosion, excellentprocessing performance are widely used in aviation, aerospace and other fields. Anodicoxidation technology can improve the corrosion and wear resistance of aluminum alloy after asurface treatment for aluminum and its alloys. In practical applications, it has become one ofthe essential process for the aluminum alloy surface treatment.In the aerospace and aviation industry, with the increasingly improvement of speed of avariety of aircraft flight and increasingly poor service environment. The problem of aircraftsurface of aerodynamic heating and thermal shock is very prominent. The material requiredfor the aircraft need have a sufficiently strength and stiffness. Generally, the aluminum alloymust be able to withstand high thermal loads as the structural material, even cracking, andeventually the protective effect of the oxide film failed.Since the difference in coefficient of thermal expansion between the anodic oxide film ofthe aluminum alloy surface and aluminum alloy matrix. Therefore, Aluminum surfacecracking behavior of the anodic film, such as2024,7075,6063, in the aerospace field werecompared and analyzed. To research the effect of heat resistance of three anodic oxide films inthe aspect from anodizing current density, anodizing time, the amount of glacial acetic acid inthe electrolyte. The research results show that2024,7075,6063, have different growth rate Inthe process of anodic oxidation. The lowest growth rate was0.13μm/min from2024. Thehardness change order is6063>7075>2024.2024aluminum alloy on the surface of theanode oxidation film has lower elastic modulus value (34.331Gpa) and7075(66.350GPa) and6063aluminum alloy surface anodic oxidation film (94.447GPa). After the heat resistance test to thethree aluminum alloy surface of the anodic oxide film, for2024aluminum and aluminumalloy7075, an increase of current density in the oxide film forming process, to extend theanodizing time will increase the cracking behavior of the anodic oxide film during the heattreatment.0.1mol/L of glacial acetic acid was added to the oxalic acid electrolyte that willincrease the thermal cracking behavior of an anodic oxide film formed, but with the increaseof glacial acetic acid, an anodic oxide film formed in the cracking behavior also increases. Based on the mathematical model of the bending beam theory and finite element method,calculating on the same process conditions, the same thickness of the anodic oxide film underthermal stress, the same thermal environment the aluminum anodized surface membranethermal stress is6063>7075>2024. And to use XRD, differential thermal and surfacemeans of spectroscopy to analyze the state before and after the heat treatment of the anodicoxide film, we can found that when thermal environment reach to500℃, theanodic oxidefilm microstructure did not change. The dehydration phenomenon caused in the process ofheat treatment lead to micro-cracks in the anodic oxide film. And micro-cracks will happenunder the thermal stress.