| YANG Wenfeng,LI Qing,LI Shaolong,CHANG Xuedong,XIE Minyue,HU Yue.Influence of Laser Paint Removal on Microstructure of Aluminum Alloy Aircraft Skin[J],53(11):239-247 |
| Influence of Laser Paint Removal on Microstructure of Aluminum Alloy Aircraft Skin |
| Received:June 28, 2023 Revised:September 07, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.11.021 |
| KeyWord:laser paint removal aircraft skin 2024-T3 aluminum alloy microstructure microhardness |
| Author | Institution |
| YANG Wenfeng |
Civil Aircraft Composite Material Maintenance Research Center, Civil Aviation Flight University of China, Sichuan Guanghan , China |
| LI Qing |
Civil Aircraft Composite Material Maintenance Research Center, Civil Aviation Flight University of China, Sichuan Guanghan , China |
| LI Shaolong |
Civil Aircraft Composite Material Maintenance Research Center, Civil Aviation Flight University of China, Sichuan Guanghan , China |
| CHANG Xuedong |
Civil Aircraft Composite Material Maintenance Research Center, Civil Aviation Flight University of China, Sichuan Guanghan , China |
| XIE Minyue |
Civil Aircraft Composite Material Maintenance Research Center, Civil Aviation Flight University of China, Sichuan Guanghan , China |
| HU Yue |
Civil Aircraft Composite Material Maintenance Research Center, Civil Aviation Flight University of China, Sichuan Guanghan , China |
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| Abstract: |
| The objective of this study is to investigate the influence of laser paint removal on the microstructure of the near-surface layer (15 μm) of the aluminum alloy aircraft skin. Consequently, the internal relationship between the microstructural changes in the near-surface layer and the corresponding microhardness variations would be elucidated. To achieve the research objectives, a comprehensive experimental methodology was employed. A nanosecond-pulsed infrared laser was utilized to remove the surface paint layer from the 2024-T3 aluminum alloy aircraft skin firstly. The laser energy density was precisely adjusted to selectively remove the paint layer to different depths, including the anodized layer, the aluminum alloy substrate, and the molten aluminum alloy surface. And then, the extent of paint removal and the surface morphology of the substrate were evaluated using advanced techniques such as laser scanning confocal microscopy (LSCM). Furthermore, state-of-the-art imaging techniques, including high-resolution three-dimensional optical microscopy (OM), scanning electron microscopy (SEM), and Image-Pro Plus software, were employed to characterize the microstructural changes in the near-surface layer of the aluminum alloy substrate after corrosion with Keller's reagent. Finally, the microhardness profiles of the substrate were analyzed with a digital micro Vickers hardness tester. The results showed that compared with the original substrate, at a low laser energy density of 4.26 J/cm2, the anodized layer remained intact, exhibiting preserved structural integrity. The surface roughness and maximum height of the aluminum alloy substrate closely resembled those of the unpainted substrate, indicating minimal surface alteration. Microstructural analysis of the near-surface layer revealed no significant changes compared with the initial state. However, a slight increase in microhardness of approximately 1.6% was observed, suggesting a marginal improvement in the material's resistance to indentation. At a relatively high laser energy density of 15.25 J/cm2, the aluminum alloy surface remained undamaged, displaying reduced surface roughness and maximum height compared with the original substrate. Microstructural analysis confirmed that the near-surface layer exhibited similar characteristics to those of the unpainted substrate, indicating negligible microstructural modifications. However, a notable enhancement in microhardness of approximately 4.8% was observed, indicating an improvement in the material's hardness and strength. Increasing the laser energy density to 27.79 J/cm2 resulted in localized melting of the aluminum alloy surface, leading to amplified surface roughness and maximum height compared to the initial state. The laser paint removal process induced grain refinement within the near-surface region, resulting in a significant increase in microhardness of approximately 17.3%. This substantial enhancement in microhardnesscould be attributed to the refined microstructure, which enhanced the material's resistance to deformation and improved its mechanical properties. In conclusion, when the paint was removed down to the anodized layer, no significant changes were observed in the microstructure of the near-surface layer, but a slight increase in microhardness could be detected. With the increasing laser energy density, the paint removal extended to the aluminum alloy substrate, resulting in a more complete preservation of the near-surface microstructure without significant changes, and a further increase in microhardness. Therefore, it can be indicated that laser paint removal of aluminum alloy aircraft skin under appropriate parameters will not significantly change the microstructure of the near surface layer of the matrix material. However, when the paint removal reaches the aluminum alloy and causes surface melting, the refinement of the near-surface grain structure and a consequently significant increase in microhardness will occur, which will result in the skin not being able to meet the requirements of safe service after laser paint removal. |
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