| LUO Yong-sheng,LI Hao,CHEN Jiang-tao,LI Yi-fei,ZHANG Qing-long,LI Rong-he,ZHAO Su.Effect of Thermal Ultrasonic Impact Treatment on Cavitation Erosion Behavior of AA6061-T6[J],52(4):427-435, 445 |
| Effect of Thermal Ultrasonic Impact Treatment on Cavitation Erosion Behavior of AA6061-T6 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.04.039 |
| KeyWord:AA6061-T6 thermal ultrasonic impact treatment cavitation resistance microstructure mechanical properties |
| Author | Institution |
| LUO Yong-sheng |
College of Mechanical Engineering and Mechanics, Ningbo University, Zhejiang Ningbo , China;Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Zhejiang Ningbo , China |
| LI Hao |
Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Zhejiang Ningbo , China;Jingci Material Technology Co., Ltd., Beijing , China |
| CHEN Jiang-tao |
College of Mechanical Engineering and Mechanics, Ningbo University, Zhejiang Ningbo , China;Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Zhejiang Ningbo , China |
| LI Yi-fei |
Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Zhejiang Ningbo , China |
| ZHANG Qing-long |
Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Zhejiang Ningbo , China |
| LI Rong-he |
Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Zhejiang Ningbo , China |
| ZHAO Su |
Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Zhejiang Ningbo , China |
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| Abstract: |
| Aluminum alloys have been widely used in the automotive industry because of their good formability and high specific strength. However, due to the harsh working environment, cavitation corrosion is prone to occur, which results in the part failure. In order to improve its cavitation resistance, surface impact strengthening treatments are often used. But these treatments usually rely on a single surface strengthening technology, by which the enhancement of its cavitation resistance is limited. Current researches show that the thermal-mechanical coupled strengthening technology using temperature-assisted surface impact can further improve the performance of the materials. It combines the advantages of impact strengthening and dynamic strain aging, leading to the higher strain rate and dislocation density. Therefore, in this paper, the method of temperature combined ultrasonic impact treatment (UIT) is used to further improve the cavitation resistance of AA6061-T6. The samples were subjected to ultrasonic impact strengthening treatment at different temperatures (RT, 50 ℃, 100 ℃ and 150 ℃). The depth and microstructure of the strengthening layer were studied by metallographic microscope; The surface orientation after impact strengthening was studied by X-ray diffraction (XRD); The hardness distribution in depth direction of the reinforced layer was studied by a microhardness instrument; The cavitation resistance performance was tested by the ultrasonic vibration cavitation platform, and the cavitation corrosion property and mechanism of the strengthened samples were studied by observing the cavitation surface using scanning electron microscope (SEM). The results show that with the increase of temperature, the yield strength of the aluminum alloy surface decreases, and the work hardening effect of the aluminum alloy surface weakens during the strengthening process, so that the plastic deformation can further develop along the depth direction. Therefore, fine grain layers of 30 µm, 50 µm, 70 µm and 90 µm depth are formed beneath the surface of the aluminum alloy, after being treated at RT, 50 ℃, 100 ℃ and 150 ℃, respectively. After UIT, the surface preferred orientation peak of the sample changes from (200) to (111). The surface hardness increases first and then decreases with the increase of coupled temperature (RT-150 ℃), which are 168.5HV, 193.7HV, 164.1HV and 134.1HV respectively. The surface microhardness at the strengthening temperature of 50 ℃ is the highest, which is 14.9% higher than that of the sample treated at RT and 108.2% higher than that of the original sample. This phenomenon results from the dynamic strain aging phenomenon occurring under the compound of temperature field, which improves the deformation resistance of the material, However, excessively high temperature will lead to dynamic recovery of internal structure, which offsets part of the cold work hardening effect and causes the decrease of hardness. After cavitation corrosion with 300 min, the cavitation corrosion resistance of the ultrasonic impact samples treated at RT, 50 ℃, 100 ℃ and 150 ℃ is 1.77, 2.03, 1.49 and 1.38 times higher than that of untreated samples, respectively. The variation trend of cavitation corrosion resistance is consistent with that of surface hardness. After thermal ultrasonic impact treatment, the cavitation corrosion damage mechanism of the samples includes not only the initial ductile fracture failure, but also the brittleness and fatigue damage. The improved cavitation resistance of the reinforced specimens is attributed to the combined effect of the increased surface hardness, grain refinement, and preferential orientation transition. |
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