Microstructural and mechanical inhomogeneity in the narrow-gap weld seam of thick GMA welded Al–Zn–Mg alloy plates


Inhomogeneity may lead to premature failure and operationally determines the lifetime estimation of thick weld joints. Considerable novelty of this paper was the achievement of the microstructural and mechanical inhomogeneity, especially along the thickness direction, in the narrow-gap weld seam of thick gas metal arc (GMA) welded Al–Zn–Mg alloy plates. The microstructure of the weld seam was investigated by means of optical metallography, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectrum (EDS), after which the phase composition was ascertained according to the x-ray diffraction (XRD) analysis and selected area diffraction analysis by TEM (TEM-SAD). The generation of intergranular short rod-shaped MgZn2 particles changed the distribution of precipitates on the grain boundary with intragranular ellipsoidal MgZn2 particles simultaneously formed as the strengthening phase, which rendered preferable mechanical performances to the bottom layer of the weld seam. The above conclusion was farther affirmed by micro fractography and EDS test results on the fractured surface of the tensile samples. In addition, the effect of following weld passes on the microstructure and micro hardness profile of the finished weld pass was investigated.

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  1. 1.

    M.M. Amrei, H. Monajati, D. Thibault, Y. Verreman, L. Germain, and P. Bocher: Microstructure characterization and hardness distribution of 13Cr4Ni multi-pass weld metal. Mater. Charact. 111, 128 (2016).

    CAS  Article  Google Scholar 

  2. 2.

    G.M. Castelluccio, J.E. Perez Ipiña, A.A. Yawny, and H.A. Ernst: Fracture testing of the best effected zone from welded steel pipes using an in situ stage. Eng. Fract. Mech. 98, 52 (2013).

    Article  Google Scholar 

  3. 3.

    G. Mathers: The Welding of Aluminium and its Alloys (CRC Press, Cambridge, England, 2002); p. 94.

    Google Scholar 

  4. 4.

    Zh.H. Zhang, Sh.Y. Dong, Y.J. Wang, B.Sh. Xu, J.X. Fang, and P. He: Microstructure characteristics of thick aluminum alloy plate joints welded by fiber laser. Mater. Des. 84, 173 (2015).

    CAS  Article  Google Scholar 

  5. 5.

    F.Y. Shu, Z. Tian, Y.H. Lv, W.X. He, F.Y. Lv, J.J. Lin, H.Y. Zhao, and B.Sh. Xu: Prediction of vulnerable zones based on residual stress and microstructure in CMT welded aluminum alloy joint. Trans. Nonferrous Met. Soc. China 25 (8), 2701 (2015).

    CAS  Article  Google Scholar 

  6. 6.

    T. Ma and G. Den Ouden: Softening behavior of Al–Zn–Mg alloys due to welding. Mater. Sci. Eng., A 266, 198 (1999).

    Article  Google Scholar 

  7. 7.

    K. Devakumaran, M.R. Ananthapadmanaban, and P.K. Ghosh: Variation of chemical composition of high strength low alloy steels with different groove sizes in multi-pass conventional and pulsed current gas metal arc weld depositions. Def. Technol. 11 (2), 147 (2015).

    Article  Google Scholar 

  8. 8.

    R. Mythili, V. Thomas Paul, S. Saroja, M. Vijayalakshmi, and V.S. Raghunathan: Microstructural modification due to reheating in multi-pass manual metal arc welds of 9Cr–1Mo steel. J. Nucl. Mater. 312, 199 (2003).

    CAS  Article  Google Scholar 

  9. 9.

    R. Ma, K. Fang, J.G. Yang, X.S. Liu, and H.Y. Fang: Grain refinement of HAZ in multi-pass welding. J. Mater. Process. Technol. 214, 1131 (2014).

    Article  Google Scholar 

  10. 10.

    V.D. Vijayanand, K. Laha, P. Parameswaran, V. Ganesan, and M.D. Mathew: Microstructural evolution during creep of 316LN stainless steel multi-pass weld joints. Mater. Sci. Eng., A 607, 138 (2014).

    CAS  Article  Google Scholar 

  11. 11.

    D. Deng and S. Kiyoshima: Numerical simulation of welding temperature field, residual stress and deformation induced by electro slag welding. Comput. Mater. Sci. 62, 23 (2012).

    Article  Google Scholar 

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This work was supported by Natural Scientific Research Innovation Foundation in Harbin Institute of Technology (Grant No. HIT.NSRIF.201703).

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Correspondence to H. Y. Zhao.

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Shu, F.Y., Sun, Y.M., Zhao, H.Y. et al. Microstructural and mechanical inhomogeneity in the narrow-gap weld seam of thick GMA welded Al–Zn–Mg alloy plates. Journal of Materials Research 31, 3948–3955 (2016). https://doi.org/10.1557/jmr.2016.392

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