| ZOU Yang,LIU Hai-xia,CHEN Jie,OUYANG Ya-dong,WANG Lei-bo.Variation of Microstructure and Property of In-situ Nanoparticle-reinforced AA6016 Matrix Composite after Ultrasonic Cavitation Strengthening[J],52(8):424-432, 443 |
| Variation of Microstructure and Property of In-situ Nanoparticle-reinforced AA6016 Matrix Composite after Ultrasonic Cavitation Strengthening |
| Received:August 30, 2022 Revised:December 02, 2022 |
| View Full Text View/Add Comment Download reader |
| DOI：10.16490/j.cnki.issn.1001-3660.2023.08.038 |
| KeyWord:aluminum matrix composite ultrasonic cavitation strengthening grain refinement residual stress surface hardness |
| Author | Institution |
| ZOU Yang |
School of Materials Science and Engineering, Jiangsu University, Jiangsu Zhenjiang , China |
| LIU Hai-xia |
School of Materials Science and Engineering, Jiangsu University, Jiangsu Zhenjiang , China |
| CHEN Jie |
School of Materials Science and Engineering, Jiangsu University, Jiangsu Zhenjiang , China |
| OUYANG Ya-dong |
School of Materials Science and Engineering, Jiangsu University, Jiangsu Zhenjiang , China |
| WANG Lei-bo |
School of Materials Science and Engineering, Jiangsu University, Jiangsu Zhenjiang , China |
|
| Hits: |
| Download times: |
| Abstract: |
| As a new composite material, in-situ nanoparticle-reinforced AA6016 aluminum matrix composite, has been developed to fulfill the requirements for the manufacturing of aerospace and automotive equipment. Although with high fatigue strength and resistance to external impact, such a material has shortcoming in terms of enduring alternating loads in corresponding applications. Therefore, it is necessary to devise a surface strengthening method to handle this issue. Strengthening through surface deformation serves as one of the commonly used surface modification methods, which can be implemented through pulsed waterjet, laser shock peening and mechanical shot peening. Each of the three methods has its own limitations. Ultrasonic cavitation strengthening is a promising, environmentally friendly surface strengthening method that can significantly improve the surface hardness of the material and produce a layer characterized by a certain depth and residual compressive stress. The work aims to improve the surface properties of in-situ nanoparticle-reinforced AA6016 aluminum matrix composite. The samples were processed into cylinders with a diameter of 185 mm, which were then polished with diamond polishing agent after polishing by sandpaper. An experimental work on these samples was performed with an ultrasonic cavitation experimental device. A constant ultrasonic frequency of 20 kHz was set throughout the experiment. The diameter of the lower end of the ultrasonic tool head was set to (15.9±0.05) mm, the submerged depth 20 mm, and the standoff distance 0.8 mm. The liquid medium of pure water was adopted and its temperature was remained at (25±1) ℃ through the thermostat method. The mass loss of the samples before and after the cavitation experiment was measured with an EX225DZH electronic analytical balance with an accuracy of 0.1 mg. Three-dimensional morphology of the sample surface was observed by an OlympusVN-4100 laser confocal microscope, and the surface roughness was calculated based on the recorded data. An FEI Nova NanoSEM 450 scanning electron microscope was used to analyze the surface morphology of the samples. The residual stress on the material surface was measured by an X-350a X-ray stress tester. The Vickers hardness was measured by a KB30S-FA automatic microhardness tester. The SmartLab X-ray diffractometer was used to observe the X-ray diffraction (XRD) patterns on surface of the samples. The electron backscattering diffraction (EBSD) technique was used to investigate variation in orientation of grains after the cavitation experiment, which was based on a GeminiSEM 300 field emission scanning electron microscope. Surface microstructure was observed with a JEM-2100PLUS transmission electron microscope. The results showed that mass loss and surface roughness of the tested samples increased as the cavitation time was extended. More specifically, the surface hardness and the residual compressive stress increased by 89.8% and 57.7%, respectively, after 30 s of ultrasonic cavitation treatment. After cavitation of 60 s, the number of recognizable grain boundaries increased remarkably relative to those monitored at previous moments. Ultrasonic cavitation can effectively improve surface property of in-situ nanoparticle-reinforced AA6016 aluminum matrix composite with appropriate processing parameters. Improvement of surface property is closely related to dislocation proliferation and dislocation entanglement. As cavitation bubbles collapse near the surface of tested samples, multi-directional force is exerted on the surface. Consequently, a large number of dislocations are introduced into the material. Due to movement of the dislocations, mutual entanglement and pinning effect of reinforcing particles cause the formation of dislocation cells, and eventually the formation of sub-grain boundaries, resulting in grain refinement. This essentially explains the increase in surface hardness. When plastic deformation of the surface attains a certain degree, cracks expand along grain boundaries, and the residual compressive stress is released. |
| Close |
|
|
|