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Study on Fatigue Crack Propagation and Fracture Characterization of 7050-T7451 Friction Stir Welded Joints

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Abstract

The fatigue crack propagation (FCP) behavior of FSW welded 7050-T7451 joints was studied using compact tensile specimens. Based on Paris law and three-stage theory of FCP, the FCP rate of joint was obtained by data fitting and calculation. The fracture morphologies at different stages of FCP were characterized by metallography and scanning electron microscopy (SEM). Results showed that the FCP rate in each region for FSW joint was as follows: heat affected zone (HAZ) > weld nugget zone (WNZ) > base metal (BM). In the first stage of FCP, the fracture morphologies of BM and HAZ were mainly tearing ridges and river pattern. There were a small number of dimples on the fracture of BM, but no dimples on the fracture of HAZ. In the second stage of FCP, the fatigue striations of the BM were denser and finer than those in the HAZ, and have dimple fracture characteristics. In the third stage of FCP, dimples still existed in the fracture surface of the BM, and the fatigue striations disappeared. The HAZ was dominated by lamellar tearing and cleavage fracture without dimples. During the three stages of FCP, the fracture morphology of the WNZ in the first and second stages was fine dimple fracture with significant equiaxed deep dimple morphology. In the third stage, the fracture dimple in the WNZ changed from equiaxed deep dimples to tearing dimples.

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Acknowledgments

This work was financially supported by the Shandong Provincial Natural Science Foundation, China (Grant No. ZR2016JL017).

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Authors and Affiliations

  1. School of Materials Science and Engineering, Shandong Jianzhu University, Jinan, 250101, People’s Republic of China

    Kang Xiao, Peng Liu, Siyu Sun & Jiaying Hu

  2. School of Mechanical Engineering and Automation, Beihang University, Beijing, 100191, People’s Republic of China

    Wei Guo & Hepeng Zhang

  3. Institute of Intelligent Manufacturing, Shandong Labor Vocational and Technical College, Jinan, 250300, People’s Republic of China

    Shikai Li

Authors
  1. Kang Xiao
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  2. Peng Liu
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  3. Siyu Sun
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  4. Wei Guo
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Correspondence to Peng Liu.

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Xiao, K., Liu, P., Sun, S. et al. Study on Fatigue Crack Propagation and Fracture Characterization of 7050-T7451 Friction Stir Welded Joints. J. of Materi Eng and Perform 30, 5625–5632 (2021). https://doi.org/10.1007/s11665-021-05797-y

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  • DOI: https://doi.org/10.1007/s11665-021-05797-y

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