TWI

The effects of friction stir welding (FSW) tool geometry on material flow during the welding of 4 mm aluminium alloys 2024-T51 and 6056-T4 were investigated. Welds were made using three different welding tool pins (conical non-threaded profile, conical with a continuous thread over the tapered length, conical and threaded with three flat areas) and two shoulder profiles (concave, tilted at 2.5 degrees away from the direction of welding and spiral profile, no tilt). Tool rotation speed was held constant while travel speed was adjusted to obtain specific weld pitch ratios. Axial load was set so that weld energy input was dependent on travel speed only. Temperature through the workpiece during welding was monitored. A titanium powder was used as a marker in one of the 2024 welds. Microstructure of the weld zone was examined in detail to establish material flow patterns in the thermomechanically affected zone, within and around the weld nugget. Nugget size and shape and the presence of defects were noted.

5th International Symposium, 14-16 Sep 2004, Session 10A: Process Developments, Paper 02