Effects of thread interruptions on tool pins in friction stir welding of AA6061

ABSTRACT

In this work, effects of pin thread and thread interruptions (flats) on weld quality and process response parameters during friction stir welding (FSW) of 6061 aluminium alloy were quantified. Otherwise, identical smooth and threaded pins with zero to four flats were adopted for FSW. Weldability and process response variables were examined. Results showed that threads with flats significantly improved weld quality and reduced in-plane forces. A three-flat threaded pin led to production of defect-free welds under all examined welding conditions. Spectral analyses of in-plane forces and weld cross-sectional analysis were performed to establish correlation among pin flats, force dynamics and defect formation. The lowest in-plane force spectra amplitudes were consistently observed for defect-free welds.

KEYWORDS:

• Friction stir welding
• unthreaded pin
• threaded pin
• flats
• in-plane forces

Acknowledgements

The authors thank Mr. Daniel Wilhelm, Associate Engineer, Department of Mechanical Engineering, University of South Carolina, Columbia, SC, USA for his help in manufacturing pins and preparing the weld joints.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors acknowledge the financial support of the Center for Friction Stir Processing which is a National Science Foundation I/UCRC (NSF I/UCRC) supported by Grant no. 0934319.