Effect of sulfuric acid anodization on fatigue property of 7A65 aluminum alloy for aviation
[Introduction]The fatigue performance of aluminum alloy part is one of the key factors determining the service life of aircraft.Sulfuric acid anodization is a common surface treatment technology used in manufacturing of aluminum alloy parts.It's very important to study the effect of anodization on the fatigue performance of aluminum alloys for guiding industrial production.[Method]The anodization and oxide film stripping were conducted repeatedly on a novel aluminum alloy 7A65 for aviation.The fatigue properties of the specimens after the repeated treatment for different times were tested with a fatigue testing machine,and then the strain vs.fatigue life curves were plotted for analysis and comparison.The morphologies of typical fractures were characterized by using stereomicroscope and scanning electron microscope,and the mechanism of fatigue failure was discussed.[Result]The fatigue limit of 7A65 aluminum alloy was greatly decreased after repeated anodization and oxide film stripping.The fatigue limit was decreased to 61.1%of the un-anodized 7A65 aluminum alloy after anodization for twice.The decreasing trend of fatigue limit became slower after oxide film striping and anodization one more time,and the fatigue limit was decreased to 56.5%of the un-anodized 7A65 aluminum alloy after anodization for four times.During these repeated treatment process,the fatigue fracture showed a transition from single to multiple in crack sources,and from ductile to brittle in fracture mechanism.[Conclusion]Sulfuric acid anodization has a significant impact on the fatigue performance of 7A65 aluminum alloy.It is necessary to control reworking times of anodized aluminum alloy parts in industrial production.
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