Abstract
Mechanical properties, such as fracture strength and Young’s modulus, of the anodic oxide films formed on aluminum specimens in sulfuric acid, oxalic acid and chromic acid baths were measured by means of a tensile testing machine. Experimental results show that the shapes of stress-strain curves of aluminum specimens with the anodic oxide films varied according to the kinds of the anodizing baths used for the formation of the films. Based on theoretical analysis of the above curves of the specimens, Young’s modulus and the fracture strength of the oxide films obtained by various baths were calculated. These results revealed that the values of fracture strength of the anodic oxide films formed in the above baths were between 140-220 MPa, while the values of Young’s modulus of the anodic oxide films were more different according to the baths used for anodizing. The values were around 36 GPa for the film formed in oxalic acid bath, around 28 GPa in the sulfuric acid bath, and around 15 GPa in the chromic acid bath. Elongation of the oxide film formed in the chromic acid bath was greater than those of the films formed in the other baths. The formation of the anodic oxide films on aluminum alloys resulted in a great decrease of the fatigue strength of aluminum specimens.
