M. Nunn, M. J. Russell, TWI Ltd, Cambridge, United Kingdom

Summary:

In this presentation, the results of recent work on FSW tool development and welding parameter studies in Al alloys will be shown. The results of applying advanced FSW tools in both butt welding and lap welding configurations will be described.

The first part of this presentation will describe recent work on the assessment of advanced FSW tool designs for butt welding in Al. FSW trials have been carried out on a range of Al alloys, in both sheet and plate thicknesses. The main focus of this effort has been a drive to increase welding speed in the FSW of thin Al. Increased welding speed offers obvious productivity benefits, but also has the potential to deliver improved weld strength in age hardening (heat damageable) alloy grades. Details from this programme of work will be shown including.

1. The FSW tool forms assessed
2. The welding parameter envelopes developed
3. Preliminary weld mechanical properties
4. The results of the initial fatigue studies

In the second part of this talk, work on the development of improved FSW tools for lap welding of Al alloys (in both sheet and plate forms) will be described. As an introduction to this work, the particular challenges of friction stir lap welding will be reviewed, and the key areas of concern in terms of weld quaility will be described. The presentation will then detail the results of recent work on the development of improved FSW tools, designed specifically for the lap welding of Al sheet. As will be seen, this work has produced major improvements in the quality of friction stir lap welds, and has addressed the key areas of concern in this joint configuration.

To conclude this presentation, preliminary results will be shown from the application of the interesting new FSW variant, Skew-Stir™ to the lap welding of Al plate. The characteristics of the Skew-Stir™ process, and Skew-Stir™ FSW tools will be described as will the results of preliminary weld mechanical and fatigue studies, carried out during this programme of work.

In summary this presentation will provide an overview of recent FSW tool development work focused on the delivery of improved welding speeds and quality in Al alloys, and will highlight future areas of development in this exciting field.