| WU Sihao,YANG Yongfei,SHI Weidong,WANG Gaowei,WU Xianglong,WU Rui.Performance of 7075 Aluminum Alloy Strengthened by Artificially Submerged Cavitation Water Jet Peening[J],53(7):190-199 |
| Performance of 7075 Aluminum Alloy Strengthened by Artificially Submerged Cavitation Water Jet Peening |
| Received:May 30, 2023 Revised:October 24, 2023 |
| View Full Text View/Add Comment Download reader |
| DOI：10.16490/j.cnki.issn.1001-3660.2024.07.020 |
| KeyWord:artificially submerged cavitation water jet peening 7075 aluminum alloy microhardness residual stress microstructure evolution surface strengthening |
| Author | Institution |
| WU Sihao |
School of Mechanical Engineering, Nantong University, Jiangsu Nantong , China |
| YANG Yongfei |
School of Mechanical Engineering, Nantong University, Jiangsu Nantong , China |
| SHI Weidong |
School of Mechanical Engineering, Nantong University, Jiangsu Nantong , China |
| WANG Gaowei |
School of Mechanical Engineering, Nantong University, Jiangsu Nantong , China |
| WU Xianglong |
School of Mechanical Engineering, Nantong University, Jiangsu Nantong , China |
| WU Rui |
School of Mechanical Engineering, Nantong University, Jiangsu Nantong , China |
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| Abstract: |
| Shot peening strengthening technology can be used to improve material performance and extend the service life of parts. A new type of shot peening strengthening technology has been developed which significantly improves impact performance by introducing compressive residual stress to the surface layer of metal components, thus making them more resistant to fatigue loads and corrosive environments. This is achieved through the use of cavitation caused by shear layers generated by two concentric co-flow jets with large velocity differences in artificially submerged cavitation water jet peening. In order to further verify the effectiveness of this technology, the surface strengthening treatment of 7075 aluminum alloy (Al7075) was carried out through artificial submerged cavitation water jet peening. The effects of artificial submerged cavitation water jet peening at different scanning speeds on the microstructure and mechanical properties of the alloy were studied. Samples with an inner nozzle pressure of 20 MPa, an outer nozzle pressure of 0.02 MPa, a target distance of 40 mm, and sample size of 100 mm × 100 mm × 3 mm were subject to heat treatment and polishing. The thickness of the surface hardening layer was analyzed with a TWVS-1 digital micro Vickers hardness tester, and the residual stress distribution on the surface of the impact area was measured with an X-ray stress analyzer. The surface morphology and roughness of Al7075 under artificially submerged cavitation water jet peening at different scanning speeds were also observed. The surface of the sample without impact was relatively flat, with a roughness value of approximately 0.46 μm. At the scanning speed of 3.0 mm/min, the roughness was approximately 1.27 μm. Under this working condition, the shot peening intensity was not high and the effect was poor. At the scanning speed of 2.0 mm/min, the roughness was approximately 4.08 μm, and the distribution density of the formed pits was increased; while at the scanning speed of 1.0 mm/min, the roughness increased significantly to approximately 12.35 μm due to the increased surface plastic deformation of the sample. The residual stress and microhardness distribution along the depth direction of Al7075 before and after artificially submerged cavitation jet shot peening were measured. When the scanning speed of artificially submerged cavitation jet shot peening reached 3.0 mm/min, the maximum microhardness on the surface of the sample was 118.6HV. At the speed of 2.0 mm/min, the maximum microhardness on the surface of the sample was about 125.4HV; and at the speed of 1.0 mm/min, the maximum microhardness on the surface of the sample was 124.9HV. This indicated that an effective hardening layer could be formed on the surface of Al7075 after artificially submerged cavitation jet shot peening enhancement, and the scanning speed of artificially submerged cavitation jet had little effect on the thickness of the hardening layer of the sample, which was about 600 μm. The microstructure evolution of Al7075 during artificially submerged cavitation water jet peening was studied and discussed. Firstly, the dislocation behavior lead to the formation of dislocation lines within the original coarse grains. As the strain increased, dislocation lines gradually accumulated, forming dislocation walls and dislocation entanglements. The rearrangement of dislocations formed small-angle grain boundaries, which further refined the lattice dislocation density within the grains. As the density of dislocations increased, the high-level fault energy and dislocation slip in aluminum alloys lead to dynamic recrystallization processes, resulting in increased grain boundary orientation differences. Ultimately, a gradual change in grain boundary characteristics occurred until the formation of large-angle grain boundaries. Artificially submerged cavitation water jet peening causes plastic deformation on the surface of Al7075, increasing surface roughness and producing an improved material performance, which ultimately extends the service life of the parts. |
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