Dr. Jiajun Wu Profile

Dr. Jiajun Wu

at Shenyang Institute of Automation

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Publications (2)

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Proceedings Article | 2 December 2020 Paper

Effect of laser shock processing on the surface morphology and microstructure of metal material

Xianliang Hu, Jibin Zhao, Jiajun Wu, Ying Lu, Boyu Sun, Yuqi Yang, Hongchao Qiao

Proceedings Volume 11717, 1171706 (2020) https://doi.org/10.1117/12.2579389

KEYWORDS: Metals, Titanium, Plasma, Aluminum, Laser processing, Surface roughness, Laser energy

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Laser shock processing (LSP) is a surface hardening technology by using plasma shock waves, which can improve the mechanical properties of material and extend the service life significantly. This work introduced the mechanism of LSP briefly, the analysis of the effect of LSP on the surface morphology, microstructure of material and its related laws are summarized with the aspect from aluminum alloy, titanium alloy and superalloy. The results show that the strong plastic deformation would be appeared in the near-surface of material due to the laser-generated stress effect, resulting the change of surface roughness and the microstructure evolution. At the same time, high-density dislocation walls, dislocation tangles and mechanical twins are generated on the surface, which are accompanied by changes in grain refinement and increased grain boundaries, thereby significantly improve the mechanical properties of material. The convex structure can be found on different material surfaces after LSP, which is micro-scale reverse deformation caused by the free plastic flow of materials under laser shock. And the high pressure of shock waves can lead to destructive dimples on the material surface, and affect its service performance. Aiming at the characteristics of different material, this work comprehensively compares the differences in the surface morphology and microstructure changes of the alloys caused by LSP, and makes a detailed analysis and discussion. This work is helpful for researchers to further understand the high strain rate dynamic plastic deformation mechanism of material treated by LSP, and promote the development of LSP.

Proceedings Article | 2 December 2020 Paper

The research progress on strengthen property and mechanism of warm laser shock peening

Yuqi Yang, Jibin Zhao, Hongchao Qiao, Jiajun Wun, Xianliang Hu

Proceedings Volume 11717, 117170E (2020) https://doi.org/10.1117/12.2584353

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Warm laser shock processing (WLSP) is an innovative method of surface modification to obviously improve materials’ surface strength stability and service performance in elevated temperature, due to the thermal-mechanical interaction of Laser shock processing, Dynamic strain aging and Dynamic precipitation. In the work, the fundamental mechanism and technological difficulty of WLSP are summarized. The technology can’t be applied in industry ripely for lacking new absorbed layer and confined layer, the method of controlling temperature precisely. The research progress of WLSP in the surface modification is analyzed respectively from the surface’s profiles, the residual stress’ amplitude and stability, the microstructure evolution, and service performance et al. in modified materials. Elevated temperature and severe plastic deformation are the key factors of WLSP, and nano precipitates and high-density dislocations induced in the process are the basic reasons for the thermal stability of residual stress and microstructure. In addition, after reviewing the influence of severe plastic deformation, the pinning effect of nanoscale precipitation and high dislocation on the materials’ structure, the problems of the technology are pointed out, providing a theoretical basis in the field.

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