Weld Formation Investigations of FSW of Al 6061-T6 Lapped Workpieces Using Dual Shoulders Tool

In present paper, dual shoulders friction stir welding (DSFSW) tools were used for friction stir welding of lapped Al 6061-T6 workpieces (152 mm X 102 mm X 3 mm) in open air-cooling conditions using different tool rotational speeds and tool feeds. A total of 17 experiments were performed using seven differently designed DSFSW tools, two different fixtures, and two different vertical milling machines to investigate the effect of tool parameters on weld formations with different processing parameters window. Some of the initial tools produced ineffective material flow due to insufficient amount of frictional heat generation and inadequate stirring action, which hindered the material movement towards the horizontal interface of lapped workpieces and reduced intermixing of workpieces material at there. Based on investigations of weld formations, a series of experiments was subsequently performed using the redesigned and modified DSFSW tools with optimized combinations of tool rotational speed and feed rate which was finally resulted in improved frictional heat generation, enhanced plasticized material flow, and sufficient material intermixing at weld interface, thereby producing improved weldments. These experiments demonstrated a progressive improvement in weld quality, ranging from unwelded joints to sound weldments, although a few hole/porosity defects were observed on the advancing side of the weld nugget zone. The investigation led to the successful development of practical DSFSW tool designs capable of producing sound friction stir welds in lapped Al 6061-T6 workpieces.

lap welding; bobbin tool; frictional heat generation; advancing side; retreating side

1. L. Dubourg, A. Merati, and M. Jahazi, “Process optimisation and mechanical properties of friction stir lap welds of 7075-T6 stringers on 2024-T3 skin,” Materials & Design, vol. 31, no. 7, pp. 3324–3330, 2010. [Crossref] [Google Scholar] [Crossref]

2. M. I. Costa, D. Verdera, C. Leitao, and D. M. Rodrigues, “Dissimilar friction stir lap welding of AA 5754-H22/AA 6082-T6 aluminium alloys: Influence of material properties and tool geometry on weld strength,” Materials & Design, vol. 87, pp. 721–731, 2015. [Crossref] [Google Scholar] [Crossref]

3. Devaraju, “Influence of Post-weld Rapid cooling on Grain size and Mechanical properties of Friction Stir Welded AA 2014,” Materials Today: Proceedings, vol. 4, no. 2, Part A, pp. 3722–3727, 2017. [Crossref] [Google Scholar] [Crossref]

4. Z. Li, Y. Yue, S. Ji, P. Chai, and Z. Zhou, “Joint features and mechanical properties of friction stir lap welded alclad 2024 aluminum alloy assisted by external stationary shoulder,” Materials & Design, vol. 90, pp. 238–247, 2016. [Crossref] [Google Scholar] [Crossref]

5. Y. C. Chen and K. Nakata, “Microstructural characterization and mechanical properties in friction stir welding of aluminum and titanium dissimilar alloys,” Materials & Design, vol. 30, no. 3, pp. 469–474, Mar. 2009. [Crossref] [Google Scholar] [Crossref]

6. Y. Gao, K. Nakata, K. Nagatsuka, T. Matsuyama, Y. Shibata, and M. Amano, “Microstructures and mechanical properties of friction stir welded brass/steel dissimilar lap joints at various welding speeds,” Materials & Design, vol. 90, pp. 1018–1025, 2016. [Crossref] [Google Scholar] [Crossref]

7. V. Paradiso, F. Rubino, P. Carlone, and G. S. Palazzo, “Magnesium and Aluminium alloys Dissimilar Joining by Friction Stir Welding,” Procedia Engineering, vol. 183, pp. 239–244, 2017. [Crossref] [Google Scholar] [Crossref]

8. K. Nagatsuka, S. Yoshida, A. Tsuchiya, and K. Nakata, “Direct joining of carbon-fiber–reinforced plastic to an aluminum alloy using friction lap joining,” Composites Part B: Engineering, vol. 73, pp. 82–88, 2015. [Crossref] [Google Scholar] [Crossref]

9. Y. Zhang, Y. Huang, X. Meng, J. Li, Y. Xie, and Q. Fan, “Friction stir lap welding of AA2024-T4 with drastically different thickness,” The International Journal of Advanced Manufacturing Technology, vol. 106, no. 9, pp. 3683–3691, Feb. 2020. [Crossref] [Google Scholar] [Crossref]

10. N. Panaskar and R. Terkar, “A Review on Recent Advances in Friction Stir Lap Welding of Aluminium and Copper,” Materials Today: Proceedings, vol. 4, no. 8, pp. 8387–8393, 2017. [Crossref] [Google Scholar] [Crossref]

11. S. Ji, Z. Li, L. Zhang, Z. Zhou, and P. Chai, “Effect of lap configuration on magnesium to aluminum friction stir lap welding assisted by external stationary shoulder,” Materials & Design, vol. 103, pp. 160–170, 2016. [Crossref] [Google Scholar] [Crossref]

12. C. Yang et al., “A comparative research on bobbin tool and conventional friction stir welding of Al-Mg-Si alloy plates,” Materials Characterization, vol. 145, pp. 20–28, Nov. 2018. [Crossref] [Google Scholar] [Crossref]

13. H. H. Jadav, V. Badheka, D. K. Sharma, and G. Upadhyay, “Effect of pin diameter and different cooling media on friction stir welding of dissimilar Al-Mg alloys,” Materials Today: Proceedings, vol. 42, pp. 362–369, 2021. [Crossref] [Google Scholar] [Crossref]

14. B. Li, Y. Shen, L. Luo, and W. Hu, “Effects of processing variables and heat treatments on Al/Ti-6Al-4V interface microstructure of bimetal clad-plate fabricated via a novel route employing friction stir lap welding,” Journal of Alloys and Compounds, vol. 658, pp. 904–913, 2016. [Crossref] [Google Scholar] [Crossref]

15. U. Dressler, G. Biallas, and U. Alfaro Mercado, “Friction stir welding of titanium alloy TiAl6V4 to aluminium alloy AA2024-T3,” Materials Science and Engineering: A, vol. 526, no. 1–2, pp. 113–117, Nov. 2009, doi: 10.1016/j.msea.2009.07.006. [Crossref] [Google Scholar] [Crossref]

16. K. Gangwar and M. Ramulu, “Friction stir welding of titanium alloys: A review,” Materials & Design, vol. 141, pp. 230–255, 2018. [Crossref] [Google Scholar] [Crossref]

17. Y. Gao, K. Nakata, K. Nagatsuka, F. C. Liu, and J. Liao, “Interface microstructural control by probe length adjustment in friction stir welding of titanium and steel lap joint,” Materials & Design, vol. 65, pp. 17–23, 2015. [Crossref] [Google Scholar] [Crossref]

18. S. H. C. Park, Y. S. Sato, H. Kokawa, K. Okamoto, S. Hirano, and M. Inagaki, “Rapid formation of the sigma phase in 304 stainless steel during friction stir welding,” Scripta Materialia, vol. 49, no. 12, pp. 1175–1180, Dec. 2003. [Crossref] [Google Scholar] [Crossref]

19. K. Fuse, V. Badheka, V. Patel, and J. Andersson, “Dual sided composite formation in Al 6061/B4C using novel bobbin tool friction stir processing,” Journal of Materials Research and Technology, vol. 13, pp. 1709–1721, Jul. 2021. [Crossref] [Google Scholar] [Crossref]

20. D. Baffari, G. Buffa, D. Campanella, E. Lo Valvo, and L. Fratini, “Experimental and numerical investigation on a new FSW based metal to composite joining technique,” Journal of Manufacturing Processes, vol. 34, pp. 758–764, Aug. 2018. [Crossref] [Google Scholar] [Crossref]

21. S. S. Emamian, M. Awang, F. Yusof, M. Sheikholeslam, and M. Mehrpouya, “Improving the friction stir welding tool life for joining the metal matrix composites,” The International Journal of Advanced Manufacturing Technology, vol. 106, no. 7, pp. 3217–3227, Feb. 2020. [Crossref] [Google Scholar] [Crossref]

22. O. S. Salih, H. Ou, X. Wei, and W. Sun, “Microstructure and mechanical properties of friction stir welded AA6092/SiC metal matrix composite,” Materials Science and Engineering: A, vol. 742, pp. 78–88, Jan. 2019. [Crossref] [Google Scholar] [Crossref]

23. S. Eslami, T. Ramos, P. J. Tavares, and P. M. G. P. Moreira, “Effect of Friction Stir Welding Parameters with Newly Developed Tool for Lap Joint of Dissimilar Polymers,” Procedia Engineering, vol. 114, pp. 199–207, 2015. [Crossref] [Google Scholar] [Crossref]

24. F. Lambiase, A. Paoletti, V. Grossi, and S. Genna, “Improving energy efficiency in friction assisted joining of metals and polymers,” Journal of Materials Processing Technology, vol. 250, pp. 379–389, 2017. [Crossref] [Google Scholar] [Crossref]

25. K. P, D. Yadav, C. S. Perugu, and S. V. Kailas, “Influence of particulate reinforcement on microstructure evolution and tensile properties of in-situ polymer derived MMC by friction stir processing,” Materials & Design, vol. 113, pp. 99–108, 2017. [Crossref] [Google Scholar] [Crossref]

26. S. Eslami, T. Ramos, P. J. Tavares, and P. M. G. P. Moreira, “Shoulder design developments for FSW lap joints of dissimilar polymers,” Journal of Manufacturing Processes, vol. 20, pp. 15–23, 2015. [Crossref] [Google Scholar] [Crossref]

27. P. S. De and R. S. Mishra, “Friction stir welding of precipitation strengthened aluminium alloys: Scope and challenges,” Science and Technology of Welding and Joining, vol. 16, no. 4, pp. 343–347, May 2011. [Crossref] [Google Scholar] [Crossref]

28. W.M. Thomas, E.D. Nicholas, J.C. Needham, M.G. Church, P. Templesmith, C. Dawes. “Friction stir welding,” GB Patent 9, 125, 978, 9, Sept 1991” [Google patent] [Google Scholar] [Crossref]

29. G. Buffa, G. Campanile, L. Fratini, and A. Prisco, “Friction stir welding of lap joints: Influence of process parameters on the metallurgical and mechanical properties,” Materials Science and Engineering: A, vol. 519, no. 1–2, pp. 19–26, Aug. 2009. [Crossref] [Google Scholar] [Crossref]

30. T. Medhi, A. Das, P. Pankaj, S. Kapil, and P. Biswas, “Multi-Pass Friction Stir Lap Welding of AA 6061-T6: Implication of Tool Pin Overlapping on Microstructure and Mechanical Properties of Joints,” Soldagem & Inspecao, vol. 27, p. e2708, 2022. [Crossref] [Google Scholar] [Crossref]

31. R. Chandran, S. Ramaiyan, A. G. Shanbhag, and S. K. V. Santhanam, “Optimization of Welding Parameters for Friction Stir Lap Welding of AA6061-T6 Alloy,” Modern Mechanical Engineering, vol. 08, no. 01, pp. 31–41, 2018. [Crossref] [Google Scholar] [Crossref]

32. X. Xu, X. Yang, G. Zhou, and J. Tong, “Microstructures and fatigue properties of friction stir lap welds in aluminum alloy AA6061-T6,” Materials & Design, vol. 35, pp. 175–183, Mar. 2012. [Crossref] [Google Scholar] [Crossref]

33. K. Fuse and V. Badheka, “Bobbin tool friction stir welding: a review,” Science and Technology of Welding and Joining, vol. 24, no. 4, pp. 277–304, May 2019. [Crossref] [Google Scholar] [Crossref]

34. P. L. Threadgill, M. M. Z. Ahmed, J. P. Martin, J. G. Perrett, and B. P. Wynne, “The Use of Bobbin Tools for Friction Stir Welding of Aluminium Alloys,” Materials Science Forum, vol. 638–642, pp. 1179–1184, Jan. 2010. [Crossref] [Google Scholar] [Crossref]

35. M. Pecanac et al., “Influence of Tool and Welding Parameters on the Risk of Wormhole Defect in Aluminum Magnesium Alloy Welded by Bobbin Tool FSW,” Metals, vol. 12, no. 6, p. 969, Jun. 2022. [Crossref] [Google Scholar] [Crossref]

36. Astarita, F. Tucci, A. T. Silvestri, M. Perrella, L. Boccarusso, and P. Carlone, “Dissimilar friction stir lap welding of AA2198 and AA7075 sheets: forces, microstructure and mechanical properties,” The International Journal of Advanced Manufacturing Technology, vol. 117, no. 3, pp. 1045–1059, Nov. 2021. [Crossref] [Google Scholar] [Crossref]

37. K. Fuse and V. Badheka, “Hybrid Self-Reacting Friction Stir Welding of AA 6061-T6 Aluminium Alloy with Cooling Assisted Approach,” Metals, vol. 11, no. 1, p. 16, Dec. 2020. [Crossref]. [Google Scholar] [Crossref]

38. K. Fuse and V. Badheka, “Effect of shoulder diameter on bobbin tool friction stir welding of AA 6061-T6 alloy,” Materials Today: Proceedings, vol. 42, pp. 810–815, 2021. [Crossref] [Google Scholar] [Crossref]

39. M. I. A. Habba, W. S. Barakat, A. Alamry, G. Çam, and M. M. Z. Ahmed, “Bobbin tool friction stir welding: A state-of-the-art review on process mechanics, material behavior, challenges, and future perspectives,” Journal of Materials Research and Technology, vol. 42, pp. 2447–2505, May 2026. [Crossref] [Google Scholar] [Crossref]

40. Gaurav Pandey1, Ashutosh Dwivedi, “Bobbin Tool Friction Stir Welding,” International Journal of Progressive Research in Engineering Management and Science, vol. 03, no. 10, pp. 251-263, Jan. 2024. [Crossref] [Google Scholar] [Crossref]

41. Węglowska, “The Use of a Bobbin Tool in the Friction Stir Welding of Plates Made of Aluminium Alloy EN AW 6082 –T6,” Material Science and Welding Technology, vol. 2018, no. 5, pp. 35–43, 2018. [Crossref] [Google Scholar] [Crossref]

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