Properties of Micro-Arc Oxides of 7075 Aluminum Alloys Prepared with Different pH AITranslate
Abstract AITranslate
7075 Al alloy is a kind of alloy material with high strength and excellent wear resistance，which is widely used in aerospace，automotive and other fields. In recent years，the application of 7075 aluminum alloy in marine vessels has gradually increased with the proposal of marine energy strategy. However，despite its good mechanical properties and strength，its corrosion resistance in marine environment is unsatisfactory and susceptible to corrosion，which seriously affects its safety and service life，and limits its large-scale application in the field of 7075 Al alloy in the field of marine engineering，national defense industry and others. In order to solve this problem，researchers are constantly searching for ways to improve the alloy，such as alloy surface coating technology，alloy formulation optimization，etc.，to improve the corrosion resistance of 7075 Al alloy in marine environment. Micro arc oxidation (MAO) technology is one of the effective ways to improve the surface properties of aluminum alloys by combining the electrolyte and appropriate electrical parameters so that the metal on the surface of the substrate interacts with the electrolyte solution，forming a ceramic film layer on the surface of the substrate，which is dominated by the metal oxides of the substrate. This technique can significantly improve the surface hardness，wear resistance，corrosion resistance and other properties of the material，which is of great importance in improving the overall performance of aluminum alloys. The pH of the electrolyte is a key parameter affecting the microstructure，mechanical properties and physical and chemical properties of the micro-arc oxidation film layer. Different pH leads to changes in the composition and structure of the film layer，which in turn affects its hardness，wear and corrosion resistance，and other properties. Therefore，in the micro-arc oxidation process，proper control of the pH of the electrolyte is essential to achieve the desired performance of the film layer. The film layer was prepared on the surface of 7075 aluminum alloy by using micro-arc oxidation technology in this paper. By adjusting pH of the electrolyte，the effects of different pH on the microstructure and corrosion resistance of the micro-arc oxidized film layer were investigated. Aiming to understand the influence mechanism of pH change on the performance of the film layer during the micro-arc oxidation process，and to provide theoretical support and experimental basis for the optimization of the micro-arc oxidation process. The surface morphology of the membrane layers prepared with different pH electrolytes was observed using scanning electron microscope （SEM），and the changes in micropore distribution，pore size，and porosity of the membrane layers were analyzed using Image-J software. Meanwhile，an eddy current thickness gauge was used to check the thickness variation of the membrane layer. Vickers microhardness tester was used to evaluate the hardness of the membrane layer. In addition，the corrosion resistance was tested in 3.5% NaCl （mass fraction） solution using an electrochemical workstation. Tafel fitting method was used to obtain the corresponding electrochemical parameters to quantitatively analyze the changes in corrosion performance of 7075 aluminum alloy before and after micro-arc oxidation treatment. And the effects of pH changes on the microstructure，thickness，hardness，and corrosion resistance of the membrane layer were systematically analyzed.The results showed that the micro-arc oxidation treatment could significantly improve the corrosion resistance of 7075 aluminum alloy. As pH of the electrolyte increased，the breakdown voltage during the micro-arc oxidation process decreased，resulting in the generation of finer discharge sparks，the number of large-size micropores （diameter larger than 2.5 μm） or the total number of micropores decreased and then increased，and the porosity of the film layer showed a tendency to decrease and then increase，while the hardness and thickness of the film layer showed the opposite tendency. Moreover，the corrosion resistance of the samples was improved. The self-corrosion current and corrosion rate of the micro-arc oxidized film layer showed a trend of decreasing and then increasing with the increase of pH，and the trend of self-corrosion voltage was opposite. When pH of the electrolyte was 12.7，the surface film layer of 7075 aluminum alloy showed the best corrosion resistance，with self-corrosion potential of -0.6 V，self-corrosion current of 4.74×10−7 A·cm−2，corrosion rate of 0.0056 mm·a−1 and polarization resistance value of 18.7×103 Ω·cm2，which was about one order of magnitude lower than that of 7075 aluminum alloy. However，when pH of the electrolyte was too high，the growth rate of the coating slowed down，the film layer became thinner and the corrosion resistance decreased.
KeyWords AITranslate
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Basic Information:
DOI：10.13373/j.cnki.cjrm.XY23120003
Chinese Library Classification Number:TG174.4
Citation Information:
7075 Al alloy is a kind of alloy material with high strength and excellent wear resistance，which is widely used in aerospace，automotive and other fields. In recent years，the application of 7075 aluminum alloy in marine vessels has gradually increased with the proposal of marine energy strategy. However，despite its good mechanical properties and strength，its corrosion resistance in marine environment is unsatisfactory and susceptible to corrosion，which seriously affects its safety and service life，and limits its large-scale application in the field of 7075 Al alloy in the field of marine engineering，national defense industry and others. In order to solve this problem，researchers are constantly searching for ways to improve the alloy，such as alloy surface coating technology，alloy formulation optimization，etc.，to improve the corrosion resistance of 7075 Al alloy in marine environment. Micro arc oxidation (MAO) technology is one of the effective ways to improve the surface properties of aluminum alloys by combining the electrolyte and appropriate electrical parameters so that the metal on the surface of the substrate interacts with the electrolyte solution，forming a ceramic film layer on the surface of the substrate，which is dominated by the metal oxides of the substrate. This technique can significantly improve the surface hardness，wear resistance，corrosion resistance and other properties of the material，which is of great importance in improving the overall performance of aluminum alloys. The pH of the electrolyte is a key parameter affecting the microstructure，mechanical properties and physical and chemical properties of the micro-arc oxidation film layer. Different pH leads to changes in the composition and structure of the film layer，which in turn affects its hardness，wear and corrosion resistance，and other properties. Therefore，in the micro-arc oxidation process，proper control of the pH of the electrolyte is essential to achieve the desired performance of the film layer. The film layer was prepared on the surface of 7075 aluminum alloy by using micro-arc oxidation technology in this paper. By adjusting pH of the electrolyte，the effects of different pH on the microstructure and corrosion resistance of the micro-arc oxidized film layer were investigated. Aiming to understand the influence mechanism of pH change on the performance of the film layer during the micro-arc oxidation process，and to provide theoretical support and experimental basis for the optimization of the micro-arc oxidation process. The surface morphology of the membrane layers prepared with different pH electrolytes was observed using scanning electron microscope （SEM），and the changes in micropore distribution，pore size，and porosity of the membrane layers were analyzed using Image-J software. Meanwhile，an eddy current thickness gauge was used to check the thickness variation of the membrane layer. Vickers microhardness tester was used to evaluate the hardness of the membrane layer. In addition，the corrosion resistance was tested in 3.5% NaCl （mass fraction） solution using an electrochemical workstation. Tafel fitting method was used to obtain the corresponding electrochemical parameters to quantitatively analyze the changes in corrosion performance of 7075 aluminum alloy before and after micro-arc oxidation treatment. And the effects of pH changes on the microstructure，thickness，hardness，and corrosion resistance of the membrane layer were systematically analyzed.The results showed that the micro-arc oxidation treatment could significantly improve the corrosion resistance of 7075 aluminum alloy. As pH of the electrolyte increased，the breakdown voltage during the micro-arc oxidation process decreased，resulting in the generation of finer discharge sparks，the number of large-size micropores （diameter larger than 2.5 μm） or the total number of micropores decreased and then increased，and the porosity of the film layer showed a tendency to decrease and then increase，while the hardness and thickness of the film layer showed the opposite tendency. Moreover，the corrosion resistance of the samples was improved. The self-corrosion current and corrosion rate of the micro-arc oxidized film layer showed a trend of decreasing and then increasing with the increase of pH，and the trend of self-corrosion voltage was opposite. When pH of the electrolyte was 12.7，the surface film layer of 7075 aluminum alloy showed the best corrosion resistance，with self-corrosion potential of -0.6 V，self-corrosion current of 4.74×10−7 A·cm−2，corrosion rate of 0.0056 mm·a−1 and polarization resistance value of 18.7×103 Ω·cm2，which was about one order of magnitude lower than that of 7075 aluminum alloy. However，when pH of the electrolyte was too high，the growth rate of the coating slowed down，the film layer became thinner and the corrosion resistance decreased.
quote
| GB/T 7714-2015 | [1] Haixia Jiang, Liman Chen, Dong Han, et al. Properties of Micro-Arc Oxides of 7075 Aluminum Alloys Prepared with Different pH[J]. Chinese Journal of Rare Metals, 2024, 48(12): 1692-1701. DOI:10.13373/j.cnki.cjrm.XY23120003. |
| MLA | [1] Haixia Jiang, et al., "Properties of Micro-Arc Oxides of 7075 Aluminum Alloys Prepared with Different pH." Chinese Journal of Rare Metals, vol. 48, no. 12, 2024, pp. 1692-1701, https://doi.org/10.13373/j.cnki.cjrm.XY23120003. |
| APA | [1] Haixia Jiang, Liman Chen, Dong Han, Bo Zhou, Gang Liu, Xiaogang Hu, & Longshi Qiu. (2024). Properties of Micro-Arc Oxides of 7075 Aluminum Alloys Prepared with Different pH. Chinese Journal of Rare Metals, 48(12), 1692-1701. https://doi.org/10.13373/j.cnki.cjrm.XY23120003 |
| IEEE | [1] Haixia Jiang, Liman Chen, Dong Han, Bo Zhou, Gang Liu, Xiaogang Hu, and Longshi Qiu, "Properties of Micro-Arc Oxides of 7075 Aluminum Alloys Prepared with Different pH," Chinese Journal of Rare Metals, vol. 48, no. 12, pp. 1692-1701, 2024, doi: 10.13373/j.cnki.cjrm.XY23120003. keywords: {7075 aluminum alloy;pH;micro-arc oxidation （MAO）;corrosion resistance} |