The Study On Anti-corrosion Performance Of Aluminum Alloy After Shot Peening Processing

In order to improve the corrosion resistance of the aluminum alloy aircraft components, such as the skin, the spar and keel beam which had been usually shot peened before serving. The corrosion areas and dents with different degrees would be produced on surface of aluminum alloy, which had been affected by the serving time and serving environment. They were difficult to completely remove or restore for the above surface corrosion defects after repair, which can reduce the anti-stress corrosion property of the component. According to these cases, the variation of the anti-stress corrosion and anti-corrosion fatigue properties of peened components for aluminum alloy were analyzed before and after corrosion, and the surface of peened components after corrosion whether need to be treated again by shot peening was discussed, which were beneficial to guide the repair of aluminum alloy components.The 7075 aluminum alloy samples with different shot peening conditions on surface were selected, in this paper, and the research contents and conclusions as the follows:(1)The slow strain rate tests were carried out under variety of experimental conditions, for aluminum alloy samples with different surface states. The results show that the corrosion resistance performances of the peened samples were improved, such as yield strength and tensile strength; the strengthening effects of the samples peened on four surfaces are more promoted than that of the samples peened on two surfaces. While, the influence of experimental conditions on stress corrosion properties of the shot peened samples were also discussed.(2)The corrosion damage with different degree were obtained by changing the corrosion parameters such as NaCl concentration, pH value, temperature and time, on the surface of aluminum alloy samples with different shot peened conditions, then the contrast tests with slow strain rate were carried out. The results show that the anti-stress corrosion properties of the samples after corrosion were descended compared with the un-corrosion samples, for the aluminum alloy samples with the same shot peening conditions; after corrosion tests, if samples were treated in shot peening again, the material properties such as the yield strength, tensile strength and elongation rate, were respectively improved in different degree.(3)The anti-stress corrosion properties of the aluminum alloy components which were shot peened before corrosion would be improved after pre-corrosion in same condition; the anti-stress corrosion properties would be further improved as the eroded sample after shot peening were peened again. While, the influence of the pre-corrosion process factors such as NaCl concentration, pH value, temperature and time, on the yield strength, tensile strength and elongation rate were analyzed.(4)The fatigue life of the aluminum alloy samples under the condition of un-shot peening and shot peening on three surfaces were analyzed after pre-corrosion. The results show that the fatigue life of materials would be improved significantly, if the aluminum alloy samples were shot peened after corrosion; the fatigue life of materials would be further improved if the eroded sample after shot peening were peened again. The stress concentration of aluminum alloy samples after shot peening would be weaken on cross-section abrupt change by observing the fracture location. While, the influence of the pre-corrosion process factors such as Na Cl concentration, temperature and time on the fatigue life of the material were analyzed.