Friction Stir Spot Welding of AA2024-T3 with Modified Refill Technique

Abstract:

The quality of welded joints of FSSW is mainly dependent on the processing parameters while the main disadvantage of this process is the creation of an exit hole. Process parameters, namely tool dimensions, tool rotational speed, and stir time were changed and their impact on bond dimensions and weld strength was investigated using 2024-T3 Al Alloy. Macro- and microstructures of the welded samples were examined; shear fracture loads were measured and the optimum set of operation variables was determined. To decrease the exit hole of the first stage the present paper proposes a modified two-stage weld-refill process employing the same welding machine. In this work, this two-stage process was referred to as reversed friction stir spot welding (ReFSSW). In the second stage, a smaller pin was used and the shoulder diameter was designed such that to force the metal of the upper plate to flow towards the exit hole of the first stage decreasing its dimensions. The metal flow in the second stage was evaluated by examining the microstructure of the metal that filled the exit hole of the first stage. Thin stir zone was found around the pin of the second stage followed by thermomechanically affected zone consisting of grains elongated in the vertical direction. The proposed process resulted in smaller exit hole dimensions and consequently higher mechanical properties compared with the conventional single-stage FSSW.

• Periodical: Key Engineering Materials (Volume 835)
• Pages: 274-287
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.835.274
• Online since: March 2020
• Authors: Mahmoud Hussin Fahmy*, Hamed A. Abdel-Aleem, Nahid Ahmed Abdel-Elraheem, M.R. El-Kousy
• Keywords: Exit Hole, Friction Stir Spot Welding, Lap-Shear Testing, Tensile Shear Fracture Load

References

[1] Mishra, R. S., and Sidhar, H., 2016. Friction Stir Welding of 2XXX Aluminum Alloys including Al-Li Alloys. Butterworth-Heinemann.

DOI: 10.1016/b978-0-12-805368-3.00001-7

[2] Mishra, R. S., De, P. S. and Kumar, N., 2014. Friction stir welding and processing: Science and Engineering. Springer.

[3] Tozaki, Y., Uematsu, Y. and Tokaji, K., 2007a. Effect of processing parameters on static strength of dissimilar friction stir spot welds between different aluminium alloys. Fatigue and Fracture of Engineering Mater. Struct. 30, 143-148.

DOI: 10.1111/j.1460-2695.2006.01096.x

[4] Tozaki, Y, Uematsu, Y., and Tokaji, K., 2007b. Effect of tool geometry on microstructure and static strength in friction stir spot welded aluminium alloys. Inter. J. Mach. Tools and Manuf., 47, 2230-2236.

DOI: 10.1016/j.ijmachtools.2007.07.005

[5] Zhang, Z., Yang, X. Zhang, J. Zhou, G., Xu, X. and Zou. B., 2011. Effect of welding parameters on microstructure and mechanical properties of friction stir spot welded 5052 aluminum alloy. Mater. Design. 32, 4461-4470.

DOI: 10.1016/j.matdes.2011.03.058

[6] Yuan, W., Mishra, R. S., Webb, S., Chen, Y. L., Carlson, B. Herling, D. R., and Grant. G. J., 2011. Effect of tool design and process parameters on properties of Al alloy 6016 friction stir spot welds. J. Mater. Process. Technol. 211, 972-977.

DOI: 10.1016/j.jmatprotec.2010.12.014

[7] Lin, Y., Liu, J., Lin, B., Lin, C., and Tsai, H., 2012. Effects of process parameters on strength of Mg alloy AZ61 friction stir spot welds. Mater. Design. 35, 350-357.

DOI: 10.1016/j.matdes.2011.08.050

[8] Badarinarayan, H., Yang, Q., and Zhu, S., 2009. Effect of tool geometry on static strength of friction stir spot-welded aluminum alloy. Int. J. Mach. Tools and Manuf. 49, 142-148.

DOI: 10.1016/j.ijmachtools.2008.09.004

[9] Uematsu, Y., Tokaji, K., Tozaki, Y., Kurita, T., and Murata, S., 2008. Effect of re-filling probe hole on tensile failure and fatigue behaviour of friction stir spot welded joints in Al–Mg–Si alloy. Inter. J. Fatigue. 30, 1956-1966.

DOI: 10.1016/j.ijfatigue.2008.01.006

[10] Cao, J. Y., Wang, M., Kong, L., and Guo, L. J., 2016. Hook formation and mechanical properties of friction spot welding in alloy 6061-T6. J. Mate. Process. Technol. 230, 254-262.

DOI: 10.1016/j.jmatprotec.2015.11.026

[11] Reimann, M., Gartner, T., Suhuddin, U., Göbel, J., and dos Santos, J. F., 2016. Keyhole closure using friction spot welding in aluminum alloy 6061–T6. J. Mater. Process. Technol. 237, 12-18.

DOI: 10.1016/j.jmatprotec.2016.05.013

[12] Boldsaikhan, E., Fukada, S., Fujimoto, M., Kamimuki, K., Okada, H., Duncan, B., Bui, P., Yeshiambel, M., Brown, B. and Handyside. A. 2017, Refill Friction Stir Spot Joining for Aerospace Aluminum Alloys." In Friction Stir Welding and Processing IX. Springer, Cham, 237-246.

DOI: 10.1007/978-3-319-52383-5_23

[13] Zhou, L., Liu, D., Nakata, K., Tsumura, T., Fujii, H., Ikeuchi, K., Michishita, Y., Fujiya, Y. and Morimoto, M. 2012. New technique of self-refilling friction stir welding to repair keyhole." Sci. Technol. Weld. Join. 17, 649-655.

DOI: 10.1179/1362171812y.0000000058

[14] Sajed, M. 2016. Parametric study of two-stage refilled friction stir spot welding. J. Manuf. Processes. 24, 307-317.

DOI: 10.1016/j.jmapro.2016.09.011

[15] Chen, K., Liu, X. and Ni, J., 2017. Keyhole refilled friction stir spot welding of aluminum alloy to advanced high strength steel. J. Mater. Process. Technol. 249, 452-462.

DOI: 10.1016/j.jmatprotec.2017.06.039