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Science China Materials

, Volume 61, Issue 3, pp 417–423 | Cite as

Achieving superior low temperature and high strain rate superplasticity in submerged friction stir welded Ti-6AI-4V alloy

  • Lihui Wu (吴利辉)
  • Hao Zhang (张昊)
  • Xianghao Zeng (曾祥浩)
  • Peng Xue (薛鹏)
  • Bolv Xiao (肖伯律)
  • Zongyi Ma (马宗义)
Articles
  • 237 Downloads

Abstract

The superplastic forming of Ti alloy welds has great application prospects in producing integrated components. However, the nugget zone (NZ) of the Ti alloy welds, produced by fusion welding or conventional friction stir welding (FSW), consists of lamellar microstructure, which exhibits either low superplasticity or high superplastic temperautre and low strain rate. As a result, the NZ plays a leading role in hindering the superplastic forming of the whole welds. In this study, submerged friction stir welding (SFSW) was conducted in Ti-6Al-4V alloy for the first time, and a defectfree weld with the NZ consisting of a strip microstructure was obtained. The NZ exhibited a low-temperature superplasticity at 600°C, which was the lowest superplastic temperature ever reported in the Ti alloy welds. Besides, at 800°C, the NZ showed high strain rate (3×10−2 s−1) superplasticity and a largest elongation of 615% at 1×10−3 s−1. Compared to conventional FSW joints, the NZ of SFSW joint exhibited a much lower flow stress and a decrease in optimal superplastic temperature by 100°C. This is mainly attributed to the easy globularization of the strip microstructure, enhancing the ability of grain/phase boundary sliding.

Keywords

titanium alloys friction stir welding superplasticity microstructure 

Ti-6A1-4V合金水下搅拌摩擦焊接头的低温与高应变速率超塑性

摘要

钛合金焊接接头超塑成型用于生产整体构件具有广泛应用前景. 熔焊或常规搅拌摩擦焊(FSW)通常得到具有片层组织的焊核, 从而导致过低超塑性、 或过高超塑温度以及过低应变速率, 成为影响接头整体成型的关键. 本研究首次采用水下FSW(SFSW)对Ti-6A1-4V进行焊接, 得到焊核为条带组织的无缺陷接头. 焊核在600°C下仍具有超塑性, 是目前实现钛合金焊接头超塑性的最低温度. 此外, 焊核可在800°C下和高应变速率(3×10−2 s—1)下实现超塑性, 并在1×10−3 s−1下获高达615%的延伸率. 与常规FSW相比, SFSW焊核的最佳超塑温度下降了100°C且流变应力大幅下降, 其优异超塑性能主要是由于条带组织在超塑变形中极易球化, 提高了晶界/相界滑移能力的结果.

Notes

Acknowledgements

This work was supported by the National Natural Science Foundation of China under Grant (51471171, 51601194, and 51331008).

References

  1. 1.
    Lütjering G, Williams JC. Titanium. 2nd ed. New York: Springer, 2007Google Scholar
  2. 2.
    Sanders DG, Ramulu M. Examination of superplastic forming combined with diffusion bonding for titanium: perspective from experience. J Mater Eng Performance, 2004, 13: 744–752CrossRefGoogle Scholar
  3. 3.
    Chen S, Huang J, Cheng D, et al. Superplastic deformation mechanism and mechanical behavior of a laser-welded Ti-6Al-4V alloy joint. Mater Sci Eng-A, 2012, 541: 110–119CrossRefGoogle Scholar
  4. 4.
    Edwards P, Ramulu M. Effect of process conditions on superplastic forming behaviour in Ti-6Al-4V friction stir welds. Sci Tech Welding Joining, 2009, 14: 669–680CrossRefGoogle Scholar
  5. 5.
    Lu W, Shi Y, Lei Y, et al. Effect of electron beam welding on the microstructures and mechanical properties of thick TC4-DT alloy. Mater Des, 2012, 34: 509–515CrossRefGoogle Scholar
  6. 6.
    Mahoney MW, Rhodes CG, Flintoff JG, et al. Properties of friction- stir-welded 7075 T651 aluminum. Metall Mat Trans A, 1998, 29: 1955–1964CrossRefGoogle Scholar
  7. 7.
    Fonda RW, Knipling KE. Texture development in near-a Ti friction stir welds. Acta Mater, 2010, 58: 6452–6463CrossRefGoogle Scholar
  8. 8.
    Wu LH, Wang D, Xiao BL, et al. Microstructural evolution of the thermomechanically affected zone in a Ti-6Al-4V friction stir welded joint. Scripta Mater, 2014, 78–79: 17–20CrossRefGoogle Scholar
  9. 9.
    Wu LH, Wang D, Xiao BL, et al. Tool wear and its effect on microstructure and properties of friction stir processed Ti-6Al-4V. Mater Chem Phys, 2014, 146: 512–522CrossRefGoogle Scholar
  10. 10.
    Wang L, Xie L, Lv Y, et al. Microstructure evolution and superelastic behavior in Ti-35Nb-2Ta-3Zr alloy processed by friction stir processing. Acta Mater, 2017, 131: 499–510CrossRefGoogle Scholar
  11. 11.
    Bahl S, Nithilaksh PL, Suwas S, et al. Processing-microstructurecrystallographic texture-surface property relationships in friction stir processing of titanium. J Materi Eng Perform, 2017, 26: 4206–4216CrossRefGoogle Scholar
  12. 12.
    Zhou L, Liu HJ, Liu P, et al. The stir zone microstructure and its formation mechanism in Ti-6Al-4V friction stir welds. Scripta Mater, 2009, 61: 596–599CrossRefGoogle Scholar
  13. 13.
    Ji S, Li Z, Zhang L, et al. Eliminating the tearing defect in Ti-6Al-4V alloy joint by back heating assisted friction stir welding. Mater Lett, 2017, 188: 21–24CrossRefGoogle Scholar
  14. 14.
    Zhou L, Liu HJ, Liu QW. Effect of rotation speed on microstructure and mechanical properties of Ti-6Al-4V friction stir welded joints. Mater Des, 2010, 31: 2631–2636CrossRefGoogle Scholar
  15. 15.
    Sanders DG, Ramulu M, Klock-McCook EJ, et al. Characterization of superplastically formed friction stir weld in titanium 6Al-4V: preliminary results. J Materi Eng Perform, 2008, 17: 187–192CrossRefGoogle Scholar
  16. 16.
    Sanders DG, Ramulu M, Edwards PD, et al. Effects on the surface texture, superplastic forming, and fatigue performance of titanium 6Al-4V friction stir welds. J Materi Eng Perform, 2010, 19: 503–509CrossRefGoogle Scholar
  17. 17.
    Ramulu M, Edwards PD, Sanders DG, et al. Tensile properties of friction stir welded and friction stir welded-superplastically formed Ti-6Al-4V butt joints. Mater Des, 2010, 31: 3056–3061CrossRefGoogle Scholar
  18. 18.
    Wu LH, Xue P, Xiao BL, et al. Achieving superior low-temperature superplasticity for lamellar microstructure in nugget of a friction stir welded Ti-6Al-4V joint. Scripta Mater, 2016, 122: 26–30CrossRefGoogle Scholar
  19. 19.
    Wu LH, Xiao BL, Ni DR, et al. Achieving superior superplasticity from lamellar microstructure of a nugget in a friction-stir-welded Ti-6Al-4V joint. Scripta Mater, 2015, 98: 44–47CrossRefGoogle Scholar
  20. 20.
    Mofid MA, Abdollah Zadeh A, Ghaini FM, et al. Submerged friction-stir welding (SFSW) underwater and under liquid nitrogen: an improved method to join al alloys to mg alloys. Metall Mat Trans A, 2012, 43: 5106–5114CrossRefGoogle Scholar
  21. 21.
    Xue P, Xiao BL, Ma ZY. High tensile ductility via enhanced strain hardening in ultrafine-grained Cu. Mater Sci Eng-A, 2012, 532: 106–110CrossRefGoogle Scholar
  22. 22.
    Chai F, Zhang D, Li Y, et al. High strain rate superplasticity of a fine-grained AZ91 magnesium alloy prepared by submerged friction stir processing. Mater Sci Eng-A, 2013, 568: 40–48CrossRefGoogle Scholar
  23. 23.
    Liu FC, Xiao BL, Wang K, et al. Investigation of superplasticity in friction stir processed 2219Al alloy. Mater Sci Eng-A, 2010, 527: 4191–4196CrossRefGoogle Scholar
  24. 24.
    Ma ZY, Mishra RS, Mahoney MW. Superplastic deformation behaviour of friction stir processed 7075Al alloy. Acta Mater, 2002, 50: 4419–4430CrossRefGoogle Scholar
  25. 25.
    Kim JS, Kim JH, Lee YT, et al. Microstructural analysis on boundary sliding and its accommodation mode during superplastic deformation of Ti-6Al-4V alloy. Mater Sci Eng-A, 1999, 263: 272–280CrossRefGoogle Scholar
  26. 26.
    Zherebtsov S, Murzinova M, Salishchev G, et al. Spheroidization of the lamellar microstructure in Ti-6Al-4V alloy during warm deformation and annealing. Acta Mater, 2011, 59: 4138–4150CrossRefGoogle Scholar

Copyright information

© Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature 2017

Authors and Affiliations

  • Lihui Wu (吴利辉)
    • 1
  • Hao Zhang (张昊)
    • 1
  • Xianghao Zeng (曾祥浩)
    • 1
  • Peng Xue (薛鹏)
    • 1
  • Bolv Xiao (肖伯律)
    • 1
  • Zongyi Ma (马宗义)
    • 1
  1. 1.Shenyang National Laboratory for Materials Science, Institute of Metal ResearchChinese Academy of SciencesShenyangChina

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