Effect of Synchronized Laser Shock Peening on Decreasing Defects and Improving Microstructures of Ti-6Al-4V Laser Joint

Li Zhang; Wentai Ouyang; Di Wu; Liyuan Sheng; Chunhai Guo; Licheng Ma; Zhihao Chen; Zhenkai Zhu; Yongxiao Du; Peijuan Cui; Zhanlin Hou; Wenwu Zhang

doi:10.3390/ma16134570

Effect of Synchronized Laser Shock Peening on Decreasing Defects and Improving Microstructures of Ti-6Al-4V Laser Joint

Materials (Basel). 2023 Jun 24;16(13):4570. doi: 10.3390/ma16134570.

Authors

Li Zhang^{1

2}, Wentai Ouyang², Di Wu^{3

4}, Liyuan Sheng^{3

4}, Chunhai Guo², Licheng Ma², Zhihao Chen^{1

2}, Zhenkai Zhu², Yongxiao Du^{1

2}, Peijuan Cui⁵, Zhanlin Hou⁵, Wenwu Zhang²

Affiliations

¹ School of Materials Science and Chemical Engineering, Ningbo University, Ningbo 315211, China.
² Key Laboratory of Aero Engine Extreme Manufacturing Technology of Zhejiang Province, Ningbo Institute of Materials Technology and Engineering, CAS, Ningbo 315201, China.
³ Shenzhen Institute, Peking University, Shenzhen 518057, China.
⁴ PKU-HKUST Shenzhen-Hongkong Institution, Shenzhen 518057, China.
⁵ Beijing Institute of Precision Mechatronics and Controls, Beijing 100076, China.

Abstract

Repairing processing is a significant method for damaged high-cost Ti-6Al-4V components to decrease economic loss, which usually utilizes a welding technique. For a large-size structural component, welding processing is commonly completed in air conditioning, which makes it difficult to avoid welding defects. To this end, an appropriate matching technique is important for improving welding performance. In the present research, asynchronized laser shock peening (ALSP) and synchronized laser shock peening (SLSP) techniques were utilized to decrease the influence of macro welding defects on laser-welded Ti-6Al-4V joints. The results show that SLSP has a greater effect on inducing surface plastic deformation on Ti-6Al-4V joints with a pitting depth of more than 25 microns while ALSP can lead to a pitting depth of about 15 microns. Through micro-CT observation a long hot crack exists in the central area of as-welded joints with a length of about 2.24 mm, accompanied by lots of pores in different sizes on double sides. After ALSP processing, some pores are eliminated while others are enlarged, and one-side crack tips present closure morphology. However, some microcracks exist on the side-wall of hot cracks. With the influence of SLSP, significant shrinkage of pores can be observed and both sides of crack tips tend to be closed, which presents a better effect than ALSP processing. Moreover, greater effects of grain refinement and thermal stress release could be achieved by SLSP processing than ALSP, which can be ascribed to dynamic recrystallization. For the as-welded joint, the ultimate tensile strength (UTS) and elongation (EL) values are 418 MPa and 0.73%, respectively. The values of UTS and EL in the ALSP processed joint are increased to 437 MPa and 1.07%, which are 4.55% and 46.48% higher than the as-welded joint, respectively. Such values after SLSP processing are 498 MPa and 1.23%, which are 19.14% and 68.49% higher than the as-welded joint, respectively.

Keywords: Ti-6Al-4V laser joint; laser shock peening; mechanical properties; microstructure; welding defect.

Abstract

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