| WANG Feng-qin,SU Yan,ZHONG Yong,ZUO Peng-cheng,ZHUANG Ning,WU Jun-sheng,ZHANG Bo-wei.Microscopic Corrosion Mechanism and Durability of 7B04 Aluminum Alloy and Its Screw Joint[J],52(10):181-193 |
| Microscopic Corrosion Mechanism and Durability of 7B04 Aluminum Alloy and Its Screw Joint |
| Received:July 06, 2022 Revised:March 23, 2023 |
| View Full Text View/Add Comment Download reader |
| DOI：10.16490/j.cnki.issn.1001-3660.2023.10.014 |
| KeyWord:7B04 aluminum alloy screw joint pitting corrosion crevice corrosion micromechanism fatigue life |
| Author | Institution |
| WANG Feng-qin |
Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing , China |
| SU Yan |
Southwest Institute of Technology and Engineering, Chongqing , China |
| ZHONG Yong |
Southwest Institute of Technology and Engineering, Chongqing , China |
| ZUO Peng-cheng |
Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing , China |
| ZHUANG Ning |
Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing , China |
| WU Jun-sheng |
Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing , China |
| ZHANG Bo-wei |
Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing , China |
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| Abstract: |
| In this work, the 7B04 high-strength aluminum alloy and its screw joints for aircraft structure were selected as the test objects to study the corrosion behavior law in the marine atmospheric environment of the South China Sea under the simulation through indoor accelerated corrosion test. Moreover, the intrinsic correlation between its microscopic corrosion mechanism and fatigue performance was analyzed in depth. The macroscopic and microscopic corrosion characteristics of 7B04 high-strength aluminum alloy and its screw joints in the simulated marine atmosphere environment of the South China Sea were studied by means of digital camera, 3D confocal microscope and scanning electron microscope, and the fatigue life of 7B04 high-strength aluminum alloy specimens and screw joints after different cycles of indoor accelerated corrosion was analyzed by fatigue test. The results indicated that the corrosion behavior of 7B04 high-strength aluminum alloy and its screw joints was significantly different after the indoor accelerated corrosion test, and the corrosion behavior of 7B04 high-strength aluminum alloy specimens could be concluded that uniform corrosion and pitting corrosion mainly occurred on the surface, while the corrosion behavior of screw joints was more complex. Therein, the corrosion of 7B04 aluminum alloy screw parts in the exposed area and away from the screw area was consistent with that of aluminum alloy specimens, but obvious crevice corrosion took place near the screw hole area. Owing to the long-term accumulation of corrosive solutions in the transition zone of the screw joint, the severe local thinning was caused on the spot. In addition, the regular of degradation of aluminum alloy specimens and screw joints was also different with the extension of corrosion cycle, and the corrosion made the performance on fatigue of 7B04 high-strength aluminum alloy and its screw joints degrade in varying degrees. The fatigue life of 7B04 aluminum alloy specimen was only reduced by 16.77% after 28 days of indoor accelerated corrosion test, demonstrating a relatively mild reduction trend of fatigue life. In contrast, the fatigue life of 7B04 aluminum alloy screw joints dropped to about 50% of the original life when the corrosion developed to the second cycle, and eventually, the screw joints exhibited an almost complete loss of the mechanical properties when the corrosion process underwent the fourth cycle. Therefore, it can be concluded that, after accelerated corrosion in the indoor environment, the corrosion of 7B04 high-strength aluminum alloy specimen only occurs as pitting corrosion, and subsequently, there is a uniform corrosion trend with the extension of the corrosion cycle, leading to the relatively flat decrease of fatigue life. Nevertheless, due to the effect of crevice corrosion on 7B04 high-strength aluminum alloy screw joint, the extremely serious corrosion comes up in the gap area, and gradually develops into a vulnerable part of fatigue fracture, resulting in a plummet of fatigue life when the corrosion process reaches the second cycle. The late peeling corrosion of the aluminum alloy leads to a decrease in the effective force cross-sectional area, and finally breaks off in advance under a large stress concentration. Although serious corrosion occurs in the transition zone of 7B04 high-strength aluminum alloy screw joint, the local force area of the screw joint induced by crevice corrosion and pitting corrosion induced by the gap area is reduced, which is the primary factor causing the sharp attenuation of fatigue life. |
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