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Article

Relationship between Stress State and Microstructure of 7B04 Aluminum Alloy Surface Fatigue Properties by Laser Shock Peening Improvement

by
Song Shu
1,2,3,
Zonghui Cheng
1,3,
Leilei Wang
1,4,*,
Xiaohong Zhan
4,*,
Feiyue Lyu
4 and
Zhiwei Dou
4
1
State-Owned Machinery Factory in Wuhu, Wuhu 241007, China
2
Science and Technology on Plasma Dynamics Laboratory, Air Force Engineering University, Xi’an 710038, China
3
Anhui Province Aviation Equipment Testing and Control and Reverse Engineering Laboratory, Wuhu 241007, China
4
College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211100, China
*
Authors to whom correspondence should be addressed.
Coatings 2022, 12(10), 1556; https://doi.org/10.3390/coatings12101556
Submission received: 7 September 2022 / Revised: 5 October 2022 / Accepted: 7 October 2022 / Published: 15 October 2022
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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Abstract

:
Fatigue performance is always an important factor affecting the application of aluminum alloys. The service life of the 7B04 aluminum alloy tends to reduce under continuous alternating loads. Therefore, a new method is urgently needed to improve fatigue performance. Laser shock peening (LSP) is a widely proposed method to enhance fatigue performance. It is found that LSP can prolong the fatigue life of 7B04 by improving the surface stress state. During the strengthening process, the residual stress is mainly attributed to the change in microstructure, which the statistical results of grain size can reflect. The microhardness of the treated 7B04 is 22.7% higher than that of the untreated sample. In addition, there is a significant residual compressive stress from the specimen surface to its interior of about 1500 µm after the process of laser shock peening. The fatigue life is extended to 93%, and the ultimate fracture changes macroscopically. The fatigue performance of 7B04 is greatly improved by the LSP treatment. The strengthening mechanism of LSP is established to reveal the relationship between microstructure and stress state to improve the fatigue performance of metal parts of any shape.

1. Introduction

The 7B04 aluminum alloy belongs to the Al–Zn–MG–Cu series, a super-hard aluminum alloy used earlier and more widely [1,2,3,4]. Due to its low density, high specific strength, good corrosion resistance and excellent machining performance, it is a critical metal in the aerospace field. For example, it is widely used for beams, frames, ribs, stringers and other aircraft components [5,6,7]. The critical parts of the aircraft are prone to fatigue fracture, which may cause severe consequences for aircraft destruction. The necessary techniques and methods should be adopted to repair the damaged aviation equipment, which can enhance its performance. Therefore, much research has been performed to find a surface-strengthening method for the 7B04 aluminum alloy [8,9,10].
Traditionally, shot peening and rolling are used to solve the fatigue problem. After shot peening, the surface roughness of metal parts is significantly increased and the residual compressive stress layer is shallow; thus, the effect of improving the fatigue performance is limited. Rolling produces a hardening layer on the surface of the workpiece, which is stratified with the internal material, causing the surface to easily fall off and not meet the processing requirements of rigid parts, such as slender rods and thin-walled pipe fittings [11,12,13,14]. Therefore, traditional strengthening methods are no longer sufficient to meet the increasing needs of modern metal components, and some new strengthening methods have been proposed to replace these traditional strengthening methods [15,16].
Laser shock peening (LSP) is an advanced surface-strengthening method that solves the shortcomings of traditional methods [17,18]. LSP is a new technology that uses plasma shock waves generated by an intense laser beam to improve the fatigue resistance of metal materials. It has outstanding advantages, such as non-contact, no heat-affected zone, highly controllable performance and significant strengthening effects [19,20]. This technique can change the surface microstructure within a certain internal depth and lead to residual compressive stress on the surface, high-density dislocation and surface nanocrystals [21,22]. Significant compressive residual stress can be introduced in the depth range of 1.5 mm to around 2 mm from the metal surface, effectively improving the surface hardness, wear resistance and fatigue strength of metal parts [23,24]. These references mainly focus on changing the microstructure to improve the fatigue properties of aluminum alloys.
Li Songbai et al. [25] explored the influence of laser impact process parameters on the hardness and fatigue life of the 2524 aluminum alloy. The results show that laser shock peening can significantly improve the surface hardness of the 2524 aluminum alloy and produce significant residual compressive stress on the surface. Laser shock peening can effectively delay the fatigue crack growth rate of the 2524-T3 aluminum alloy; thus, effectively prolonging the fatigue life [26].
Wang Jun et al. [27] used a laser beam with a wavelength of 1064 nm and a pulse width of about 10 ns to conduct a double-sided shock peening treatment on the 304 stainless steel and conducted experiments and observations on the samples. The results show that the maximum deformation of the specimen surface is about 25 µm and the maximum residual compressive stress is 218 MPa, as well as the crack source is transferred to the specimen. Laser shock strengthening can significantly reduce the crack growth rate in the impact zone. Based on the curve of the fatigue crack growth rate, it is verified again that laser shock peening can significantly improve the fatigue resistance of the 304 stainless steel [28,29].
Most of the research mainly focuses on the relationship between microstructure and mechanical properties during the LSP processes, such as corrosive properties [30], yield strength [31] and microhardness profile [32]. In addition, Hfaiedh et al. [33] investigated the residual stress distribution induced by laser shock processing to improve the fatigue performance of materials. In this paper, we further studied the effect of LSP on the fatigue life and fracture behavior of the 7B04 aluminum alloy and the corresponding strengthening mechanism analyses under high loading stress. The strengthening mechanism of LSP is proven to reveal the relationship between microstructure and stress state to improve the fatigue performance of materials.

2. Experiments

2.1. Materials and Components

Table 1 lists the chemical composition of the 7B04 aluminum alloy. The size of the 7B04 aluminum alloy plates was 450 mm × 300 mm × 10 mm, and the fatigue samples were cut from two areas (250 mm × 120 mm), which are outlined by the red dashed line in Figure 1a. The fatigue samples were cut by a wire-cut machine, after which the sample surface without an LSP treatment was processed by grinding and polishing. The size of the fatigue samples was processed in strict accordance with GB/T 3075-2008 “Metallic Material-Fatigue Testing-Axial Force-Controlled Method”. The surface of the fatigue samples was cleaned with alcohol and dried with cold air to ensure uniform roughness. After processing these samples, the original surface roughness Ra (the surface roughness of the sample without any surface treatment) was less than 0.8 µm. The size of the fatigue sample and the selection of the LSP region are shown in Figure 1b. Finally, the LSP was executed on the entire distance segment, as shown in the red dotted box.
The laser shock was performed four times. Each laser shock area was treated with film (black tape) to ensure the effect of the laser shock. The spot distribution of the first laser shock is shown in Figure 2a, and the adjacent laser spots are tangent. The laser spot position of the second shock was shifted to the right, relative to the laser spot position of the first shock, and the amount of movement was the radius of the laser spot, as shown in Figure 2b. After that, the laser spot position of the third shock was moved down relative to the laser spot position of the second shock, as shown in Figure 2c. Finally, the laser spot was shifted to the left, relative to the last laser spot in Figure 2d, and the amount of movement still kept the radius of the laser spot.

2.2. Experimental Procedures

Figure 3 shows the complete set of the YS100-R200A laser shock equipment for Xi’an Tianruida Optoelectronics Technology Co., Ltd. (Xi’an, China). The maximum output energy value of this equipment was 10 J. The pulse width and the focusing spot size were 18–20 ns and 2–5 mm, respectively. The positioning accuracy of the six-joint robot was ±0.2 mm; it was equipped with a water nozzle robot. The motion path and laser parameters of the robot were set on the operation interface so that the laser shock treatment can be accurately completed for the corresponding area. Table 2 lists the different LSP-processing parameters.

2.3. Measurement Apparatuses and Methods

The residual stress test was conducted for the different conditions of the fatigue samples before tension through an X-ray diffractometer (Tongda Technology Co., LTD, Dandong, China), which had a power of 3 KW, as well as an angle deviation of no more than ±1% and a minimum step angle of 0.0001. The ultra-high measurement speed allowed for the measurement to be completed within 1 min.
Changes in the grain morphology were observed using a Leica DMI 3000 M metallographic microscope (Wetzlar, Germany). The SRA-1 surface roughness tester (Beijing Shangguang Instrument Co., LTD, Beijing, China) measured the surface roughness. As for the residual stress, the equipment consisted of an LXRD residual stress tester (Beituo Science and Technology Co. LTD, Guangzhou, China) and an 8818 V-3 electrolytic polishing device (Veno Metal Surface Treatment Technology Co. LTD, Shanghai, China). After the electrolytic polishing, the microhardness was tested at a 200-g load for 15 s using an HX-1000TM/LCD device (Shanghai optical instrument factory, Shanghai, China).
The fatigue test was carried out at room temperature with a high frequency of the alternating load (150 Hz) through the QBG-100 high-frequency fatigue-testing machine (Lihua Test System Co., LTD, Jinan, China). The loading stress ranged from 500 MPa to 580 MPa. The fracture toughness of the specimens was tested under continuous alternating loads generated by the shaker to test the crack growth rate and the fracture threshold of the 7B04 alloy.

3. Results and Discussion

3.1. Surface Roughness and Microhardness

The roughness changes of the 7B04 aluminum alloy after the different strengthening processes are compared, as shown in Figure 4. It can be seen that the surface roughness increases with the increase in the Al-1–Al-3 laser power density. At the same power density, Al-4 has multiple impacts compared with Al-1, and the surface state decreases more seriously. The surface state of the 7B04 aluminum alloy is relatively good after the Al-1 and Al-2 peening processes.
As shown in Figure 4, the microhardnesses of the 7B04 aluminum alloy after the different strengthening processes are compared. After the different laser impact processing, the surface microhardness increased by more than 10%. The increase in the laser power density intensifies the plastic deformation of the material during the strengthening process, which increases the surface hardness of the sample significantly. In addition, the hardened layer of the sample becomes deeper with the increase in laser power density. The plastic deformation layer of the sample is thickened with the increase in laser power density, which leads to a deeper hardening layer.
On the other hand, the laser-induced high-pressure shock wave produces a plastic deformation layer with a high strain rate on the surface of the 7B04 aluminum alloy. Meanwhile, the laser shock can increase the dislocation density inside and between the original grains, resulting in a work-hardening effect. With the increase in laser energy and shock times, the deformation energy and strain rate increase, the degree of plastic deformation increases, the degree of grain refinement deepens, the grain boundaries increase and the work hardening effect becomes more significant, which leads to the decrease in the hardness growth rate of the 7B04 aluminum alloy.
However, a slight decrease can be found in both the roughness and the microhardness for the Al-4 samples compared to the Al-3 samples. As the number of shock times exceeds three, the surface of the residual stress becomes more uniform and the roughness begins to decrease. The surface of the residual stress drops sharply for the Al-4 samples, and then the deformation energy and the degree of plastic deformation decline. The work-hardening effect is not apparent, which causes the microhardness of the Al-4 samples to be lower than that of the Al-3 samples.

3.2. Microstructures

As shown in Figure 5, the 7B04 matrix and the Al-1–AL-4 strengthening region are amplified by a 500× metallographic structure. It can be seen that the metallographic structure is an equiaxial α-phase and β-transition matrix containing an acicular α-phase. After the laser shock, a large number of refined grains are formed at the grain boundary of the microstructure.
From Figure 5, it can be observed that there is a difference in the grain size for the sample in the different states. Peening on the Al-1 and Al-2 samples with a single pulse at a laser fluence of 2.83 and 3.54 GW/cm2 led to a substantial increase in the compressive residual surface stress in comparison to the unpeened sample (Al-matrix), which can increase the nucleation rate and obtain more fine grains, as shown in Figure 5b,c. However, a higher fluence for Al-3 and the number of laser impacts for Al-4 can lead to a homogenous distribution of the surface residual stress. Then, the surface residual stress dropped sharply for the Al-3 and Al-4 samples, which can obtain a small number of fine grains, as shown in Figure 5d,e.
The grains are gradually refined because the increase in the laser power density will significantly impact the dislocation density and the moving speed during the deformation, enhancing the plastic deformation ability of the material [34]. As the number of movable dislocations increases, the material will undergo further plastic deformation. The presence of refined grains near the larger grains indicates that the introduction of a pulsed laser contributes to the dynamic recrystallization of the material.

3.3. Residual Stress

Figure 6 compares the residual stress test results of the 7B04 aluminum alloy matrix under different laser shock energies. It can be seen that significant residual compressive stress is maintained on the surface up to 1500 μm after the laser shock peening. This is because the surface grains appear in the dislocation slip and annihilation when the shock wave pressure exceeds the dynamic yield strength of the material, which forms more refined grains. As the position reached by the shock wave is further away from the surface, the energy continues to decay and the plastic strain of the material decreases; therefore, the residual stress decreases.
The residual compressive stress on the specimen surface gradually increases with the increased laser shock energy, but the increased amplitude gradually decreases. It can be seen that the pulse energy is beneficial to improving the surface residual compressive stress of the 7B04 aluminum alloy material, but it is not necessarily true that the more influential the pulsed laser, the better. When the peak pressure of the laser-induced shock wave exceeds a certain multiple of the highest elastic stress of the material, the wave released from the surface of the material is amplified from the edge of the impact area and converges to the center to produce an opposite strain, affecting the distribution of the residual stress. The plastic deformation in the impact area is a superposition with increased impact energy. The dislocation density increases, and the deformation resistance increases. The plastic deformation reaches the saturation state, and the growing range of residual compressive stress is close to the saturation state.

3.4. Failure Mechanism

Figure 7 shows the S–N curves of the 7B04 aluminum alloy matrix at three stress levels. As can be seen from Figure 7, after the laser shock peening, the fatigue life of the 7B04 aluminum alloy has been dramatically improved at various stress levels. Under low stress levels, the fatigue life improvement effect is more apparent, and the life improvement can reach more than five times.
The sample after the fatigue test under the condition of high-stress load is shown in Figure 8. The fracture morphology of the unstrengthened specimen is similar to that of the tensile fracture under static load, with a shear fracture zone of nearly 45°. The transient fracture zone in the crack propagation region is straight and perpendicular to the axis direction of the specimen. The macroscopic fracture of the sample is flat after the laser shock peening, which belongs to the typical macroscopic morphology of the fatigue fracture.
The surface morphology of the fracture samples before and after hardening was observed by scanning electron microscopy. The convergence area of the pattern against the river was the source of the crack. According to the fracture morphology in Figure 9a, the crack of the unreinforced fatigue sample originates from the surface. It can also be found that the fatigue band is perpendicular to the crack propagation direction, as shown in Figure 9c. As it can be seen from the fracture morphology in Figure 9b, the fatigue sample presents multi-source cracking after the laser shock peening. The fatigue bands appear in groups, and adjacent groups of fatigue bands form tiny, raised transition prisms, as is shown in Figure 9d. The fatigue fracture surface is composed of many transition prisms with non-parallel and discontinuous fatigue bands for the LSP samples, which can improve the fatigue performance of the materials. The diameter and depth of the dimples in the LSP samples are lower than those in the unreinforced fatigue sample, which means that the strength of the LSP samples is higher, as shown in Figure 9e,f.

4. Conclusions

The roughness, metallography, gradient residual stress and fatigue life of the 7B04 aluminum alloy were tested under different laser powers and pulses. The following conclusions were obtained:
(1)
The laser shock does not only cause significant residual compressive stress on the metal surface, but it can also cause the modification of the structure in the surface deformation layer; therefore, it can improve the fatigue performance of metal parts.
(2)
The suitable laser power density of the 7B04 aluminum alloy is 3.54 GW/cm2. After the laser shock peening, the surface of the 7B04 aluminum alloy was in a state of residual compressive stress to a depth of 1500 μm, and the fatigue life increased by at least 93%. Stress-life curves were obtained to provide a reference for prolonging the overhaul cycle of the metal parts of the corresponding brand of aircraft and optimizing the structure of damaged parts.
(3)
After the laser shock treatment, the fatigue life of the 7B04 aluminum alloy can be increased by more than five times at low stress levels. The crack of the unreinforced fatigue sample originates from the surface, while the fatigue sample presents multi-source cracking after the laser shock peening process.

Author Contributions

Methodology, Z.C.; writing—original draft, S.S.; supervision, L.W.; project administration, X.Z.; writing—review and editing, F.L.; data curation, Z.D. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Foundation of National Key Laboratory of Science and Technology on Helicopter Transmission (grant number HTL-A-22G08).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Zheng, C.; Tian, Z.; Zhao, X.; Tan, Y.; Zhang, G.; Zhao, G.; Ji, Z. Effect of pulsed laser parameters on deformation inhomogeneity in laser shock incremental forming of pure copper foil. Opt. Laser Technol. 2020, 127, 106205. [Google Scholar] [CrossRef]
  2. Zhang, X.; Ma, Y.; Peng, Y.; Yang, M.; Du, Y.; Wang, Z. Effects of residual stress induced by laser shock peening on mixed-mode crack propagation behavior in 7075-T6 aluminum alloy panel. Theor. Appl. Fract. Mec. 2022, 119, 103358. [Google Scholar] [CrossRef]
  3. Zabeen, S.; Langer, K.; Fitzpatrick, M.E. Effect of alloy temper on surface modification of aluminium 2624 by laser shock peening. Surf. Coat. Technol. 2018, 347, 123–135. [Google Scholar] [CrossRef]
  4. Wang, J.T.; Zhang, Y.K.; Chen, J.F.; Zhou, J.Y.; Luo, K.Y.; Tan, W.S.; Sun, L.Y.; Lu, Y.L. Effect of laser shock peening on the high-temperature fatigue performance of 7075 aluminum alloy. Mat. Sci. Eng. A-Struct. 2017, 704, 459–468. [Google Scholar] [CrossRef]
  5. Yang, Y.; Zhou, K.; Li, G. Surface gradient microstructural characteristics and evolution mechanism of 2195 aluminum lithium alloy induced by laser shock peening. Opt. Laser Technol. 2019, 109, 1–7. [Google Scholar] [CrossRef]
  6. Xiang, Y.F.; Mei, R.L.; Wang, S.P.; Azad, F.; Zhao, L.Z.; Su, S.C. Numerical investigation of the effect of laser shock peening parameters on the residual stress and deformation response of 7075 aluminum alloy. Optik 2021, 243, 167446. [Google Scholar] [CrossRef]
  7. Wang, J.T.; Zhang, Y.K.; Chen, J.F.; Zhou, J.Y.; Ge, M.Z.; Lu, Y.L.; Li, X.L. Effects of laser shock peening on stress corrosion behavior of 7075 aluminum alloy laser welded joints. Mat. Sci. Eng. A-Struct. 2015, 647, 7–14. [Google Scholar] [CrossRef]
  8. Wang, J.T.; Xie, L.; Luo, K.Y.; Tan, W.S.; Cheng, L.; Chen, J.F.; Lu, Y.L.; Li, X.P.; Ge, M.Z. Improving creep properties of 7075 aluminum alloy by laser shock peening. Surf. Coat. Technol. 2018, 349, 725–735. [Google Scholar] [CrossRef]
  9. Wang, J.; Lu, Y.; Zhou, D.; Sun, L.; Xie, L.; Wang, J. Mechanical properties and microstructural response of 2A14 aluminum alloy subjected to multiple laser shock peening impacts. Vacuum 2019, 165, 193–198. [Google Scholar] [CrossRef]
  10. Wang, H.; Ning, C.; Huang, Y.; Cao, Z.; Chen, X.; Zhang, W. Improvement of abrasion resistance in artificial seawater and corrosion resistance in NaCl solution of 7075 aluminum alloy processed by laser shock peening. Opt. Laser Eng. 2017, 90, 179–185. [Google Scholar] [CrossRef]
  11. Aswegen, D.C.; Polese, C. Experimental and analytical investigation of the effects of laser shock peening processing strategy on fatigue crack growth in thin 2024 aluminium alloy panels. Int. J. Fatigue 2021, 142, 105969. [Google Scholar] [CrossRef]
  12. Trdan, U.; Grum, J. Evaluation of corrosion resistance of AA6082-T651 aluminium alloy after laser shock peening by means of cyclic polarisation and ElS methods. Corros. Sci. 2012, 59, 324–333. [Google Scholar]
  13. Sun, R.; Li, L.; Zhu, Y.; Guo, W.; Peng, P.; Cong, B.; Sun, J.; Che, Z.; Li, B.; Guo, C.; et al. Microstructure, residual stress and tensile properties control of wire-arc additive manufactured 2319 aluminum alloy with laser shock peening. J. Alloys Compd. 2018, 747, 255–265. [Google Scholar] [CrossRef]
  14. Sun, B.; Zhao, J.; Qiao, H.; Lu, Y. Effects of square spot size and beam quality on residual stress of 7050 aluminum alloy by laser shock peening. Mater. Chem. Phys. 2022, 284, 126023. [Google Scholar] [CrossRef]
  15. Song, M.; Liu, J.; Chen, H.; Hu, Y.; Shi, Z.; Yin, H.; Xia, J.; Berto, F.; Li, R. Effects and optimization of biomimetic laser shock peening on residual fatigue life improvement of aluminum alloy used in aircraft skin. Theor. Appl. Fract. Mec. 2022, 117, 103155. [Google Scholar] [CrossRef]
  16. Rouleau, B.; Peyre, P.; Breuils, J.; Pelletier, H.; Baudin, T.; Brisset, F. Characterization at a local scale of a laser-shock peened aluminum alloy surface. Appl. Surf. Sci. 2011, 257, 7195–7203. [Google Scholar] [CrossRef]
  17. Qin, Z.; Li, B.; Huang, X.; Zhang, H.; Chen, R.; Adeel, M.; Xue, H. The effect of laser shock peening on surface integrity and high and very high cycle fatigue properties of 2024-T351 aluminum alloy. Opt. Laser Technol. 2022, 149, 107897. [Google Scholar]
  18. Park, J.; Yeo, I.; Jang, I.; Jeong, S. Improvement of friction characteristics of cast aluminum-silicon alloy by laser shock peening. J. Mater. Process. Technol. 2019, 266, 283–291. [Google Scholar] [CrossRef]
  19. Meng, X.; Wang, H.; Tan, W.; Cai, J.; Zhou, J.; Liu, L. Gradient microstructure and vibration fatigue properties of 2024-T351 aluminium alloy treated by laser shock peening. Surf. Coat. Technol. 2020, 391, 125698. [Google Scholar] [CrossRef]
  20. Abeens, M.; Muruganandhan, R.; Thirumavalavan, K. Effect of Low energy laser shock peening on plastic deformation, wettability and corrosion resistance of aluminum alloy 7075 T651. Optik 2020, 219, 165045. [Google Scholar]
  21. Gao, Y.; Yang, W.; Huang, Z.; Lu, Z. Effects of residual stress and surface roughness on the fatigue life of nickel aluminium bronze alloy under laser shock peening. Eng. Fract. Mech. 2021, 244, 107524. [Google Scholar] [CrossRef]
  22. Dhakal, B.; Swaroop, S. Mechanical properties and deformation dependent microstructural aspects of laser shock peened 7075-T6 aluminum alloy without coating. Mater. Charact. 2022, 183, 111620. [Google Scholar] [CrossRef]
  23. Lu, L.; Huang, T.; Zhong, M. WC nano-particle surface injection via laser shock peening onto 5A06 aluminum alloy, Surf. Coat. Technol. 2012, 206, 4525–4530. [Google Scholar] [CrossRef]
  24. Liu, P.; Sun, S.; Xu, S.; Li, Y.; Ren, G. Microstructure and properties in the weld surface of friction stir welded 7050-T7451 aluminium alloys by laser shock peening. Vacuum 2018, 152, 25–29. [Google Scholar] [CrossRef]
  25. Li, B.; Zhang, C.; Li, X.; Wang, C. Effect of Laser Shock Peening on Fatigue Life of 2524 Aluminum Alloy. Surf. Technol. 2020, 5, 207213. [Google Scholar]
  26. Adu-Gyamfi, S.; Ren, X.D.; Larson, E.A.; Ren, Y.; Tong, Z. The effects of laser shock peening scanning patterns on residual stress distribution and fatigue life of AA2024 aluminium alloy. Opt. Laser Technol. 2018, 108, 177–185. [Google Scholar] [CrossRef]
  27. Wang, J.; Li, M.; Wang, J.X.; Zhang, X.Q.; Wei, W. Effects of Laser Shock Processing on Fatigue Life of 304 Stainless Steel. Chin. J. Lasers 2019, 46, 100107. [Google Scholar]
  28. He, Z.; Shen, Y.; Tao, J.; Chen, H.; Zeng, X.; Huang, X.; El-Aty, A.A. Laser shock peening regulating aluminum alloy surface residual stresses for enhancing the mechanical properties: Roles of shock number and energy. Surf. Coat. Technol. 2021, 421, 127481. [Google Scholar] [CrossRef]
  29. Guo, W.; Wang, H.; He, G.; Peng, P.; He, D.; Han, G.; Yan, J. Comparison of mechanical and corrosion properties of 7050 aluminum alloy after different laser shock peening. Opt. Laser Technol. 2022, 151, 108061. [Google Scholar] [CrossRef]
  30. Karthik, D.; Jiang, J.; Hu, Y.; Yao, Z. Effect of multiple laser shock peening on microstructure, crystallographic texture and pitting corrosion of Aluminum-Lithium alloy 2060-T8. Surf. Coat. Technol. 2021, 421, 127354. [Google Scholar] [CrossRef]
  31. Jing, Y.; Fang, X.; Xi, N.; Feng, X.; Huang, K. Investigation of microstructure and mechanical properties evolution in 7050 aluminum alloy and 316L stainless steel treated by laser shock peening. Mater. Charact. 2021, 182, 111571. [Google Scholar] [CrossRef]
  32. Dhakal, B.; Swaroop, S. Effect of laser shock peening on mechanical and microstructural aspects of 6061-T6 aluminum alloy. J. Mater. Process. Technol. 2020, 282, 116640. [Google Scholar] [CrossRef]
  33. Hfaiedh, N.; Peyre, P.; Song, H.; Popa, I.; Ji, V.; Vignal, V. Finite element analysis of laser shock peening of 2050-T8 aluminum alloy. Int. J. Fatigue 2015, 70, 480–489. [Google Scholar] [CrossRef] [Green Version]
  34. Rai, A.K.; Biswal, R.; Gupta, R.K.; Singh, R.; Rai, S.K.; Ranganathan, K.; Ganesh, P.; Kaul, R.; Kushvinder, S.B. Study on the effect of multiple laser shock peening on residual stress and microstructural changes in modified 9Cr-1Mo (P91) steel. Surf. Coat. Technol. 2019, 358, 125–135. [Google Scholar] [CrossRef]
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Figure 1. Diagram of the 7B04 aluminum alloy reinforcement area. (a) Position of the fatigue sample sampling; (b) size of the fatigue sample and the selection of the LSP region.
Figure 1. Diagram of the 7B04 aluminum alloy reinforcement area. (a) Position of the fatigue sample sampling; (b) size of the fatigue sample and the selection of the LSP region.
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Figure 2. Schematic diagram of the laser shock method. (a) The first laser shock; (b) the second laser shock; (c) the third laser shock; (d) the fourth laser shock.
Figure 2. Schematic diagram of the laser shock method. (a) The first laser shock; (b) the second laser shock; (c) the third laser shock; (d) the fourth laser shock.
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Figure 3. (a) YS100-R200A laser shock device; (b) the laser shock process.
Figure 3. (a) YS100-R200A laser shock device; (b) the laser shock process.
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Figure 4. (a) Comparison of the roughness of the 7B04 aluminum alloy under different strengthening processes; (b) Comparison of the microhardness of the 7B04 aluminum alloy under different strengthening processes.
Figure 4. (a) Comparison of the roughness of the 7B04 aluminum alloy under different strengthening processes; (b) Comparison of the microhardness of the 7B04 aluminum alloy under different strengthening processes.
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Figure 5. 7B04 aluminum alloy phase structure. (a) Al matrix; (b) Al-1 enhancement zone; (c) Al-2 enhancement zone; (d) Al-3 enhancement zone; (e) Al-4 enhancement zone.
Figure 5. 7B04 aluminum alloy phase structure. (a) Al matrix; (b) Al-1 enhancement zone; (c) Al-2 enhancement zone; (d) Al-3 enhancement zone; (e) Al-4 enhancement zone.
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Figure 6. Comparison of the residual stress in different strengthening processes of the 7B04 aluminum alloy.
Figure 6. Comparison of the residual stress in different strengthening processes of the 7B04 aluminum alloy.
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Figure 7. Comparison of the fatigue life of the 7B04 aluminum alloy before and after impact strengthening.
Figure 7. Comparison of the fatigue life of the 7B04 aluminum alloy before and after impact strengthening.
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Figure 8. Morphology of the 7B04 aluminum alloy specimen after the fatigue test.
Figure 8. Morphology of the 7B04 aluminum alloy specimen after the fatigue test.
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Figure 9. Morphology of the 7B04 aluminum alloy sample after the fatigue test. (a) Without a laser shock-peening sample; (b) a laser shock-peening sample; (c) a local enlarged figure of the crack initiation region without LSP; (d) a local enlarged figure of the crack initiation region with LSP; (e) a local enlarged figure of the final fracture without LSP; (f) a local enlarged figure of the final fracture region with LSP.
Figure 9. Morphology of the 7B04 aluminum alloy sample after the fatigue test. (a) Without a laser shock-peening sample; (b) a laser shock-peening sample; (c) a local enlarged figure of the crack initiation region without LSP; (d) a local enlarged figure of the crack initiation region with LSP; (e) a local enlarged figure of the final fracture without LSP; (f) a local enlarged figure of the final fracture region with LSP.
Coatings 12 01556 g009
Table
Table 1. Chemical composition of the 7B04 aluminum alloy (wt.%).
Table 1. Chemical composition of the 7B04 aluminum alloy (wt.%).
ZnMgCuMnTiFeSiAl
5.0–6.51.8–2.81.4–2.00.2–0.6≤0.050.05–0.25≤0.1Bal.
Table
Table 2. Laser shock peening process parameters of the 7B04 aluminum alloy.
Table 2. Laser shock peening process parameters of the 7B04 aluminum alloy.
NumberLaser Power/JSpot Diameter/mmOverlap RatePulseLaser Fluence/GW/cm2
Al-14350 %12.83
Al-2513.54
Al-3614.25
Al-4432.83
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Shu, S.; Cheng, Z.; Wang, L.; Zhan, X.; Lyu, F.; Dou, Z. Relationship between Stress State and Microstructure of 7B04 Aluminum Alloy Surface Fatigue Properties by Laser Shock Peening Improvement. Coatings 2022, 12, 1556. https://doi.org/10.3390/coatings12101556

AMA Style

Shu S, Cheng Z, Wang L, Zhan X, Lyu F, Dou Z. Relationship between Stress State and Microstructure of 7B04 Aluminum Alloy Surface Fatigue Properties by Laser Shock Peening Improvement. Coatings. 2022; 12(10):1556. https://doi.org/10.3390/coatings12101556

Chicago/Turabian Style

Shu, Song, Zonghui Cheng, Leilei Wang, Xiaohong Zhan, Feiyue Lyu, and Zhiwei Dou. 2022. "Relationship between Stress State and Microstructure of 7B04 Aluminum Alloy Surface Fatigue Properties by Laser Shock Peening Improvement" Coatings 12, no. 10: 1556. https://doi.org/10.3390/coatings12101556

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