TWI

The influence of pin length and insulating anvil material on friction stir spot welding (FSSW) of thin (0.9 mm) 6111-T4 aluminium (Al, 0.73%Si, 0.65%Mg, 0.96%Cu, 0.3%Mn, 0.2%Fe) was investigated. Welds were made varying the length of the tool pin (1.0, 1.2, 1.4, 1.6 mm) with a constant shoulder plunge depth (10 mm) and reducing the heat loss by using an insulating material (Macor ceramic plate) rather than a conventional steel anvil. Welding parameters were plunge rate (2.5 mm/s), rotation speed (2000 rpm), dwell time (2.5 s), and shoulder plunge depth (0.2 mm). Weld cross sections were examined. The weld energy calculation from the torque curve is given. Lap shear test load displacement curves showing the behaviour (average maximum shear loads and failure energies) for different pin lengths with steel and ceramic anvils were established and discussed. The effect of the pin length, dwell time and insulating material on weld energy and thermal measurements is described. The effect of pin length on failure mode (shear, mixed cleavage, nugget pull out) and average strength of the lap shear was assessed. Microstructural changes and hardness distributions in the HAZ/TMAZ for different pin lengths and insulation are discussed. Factors contributing to joint performance and weld quality in thin sheet FSSW are summarised.

7th International Symposium, 20-22 May 2008, 11A: Spot 3 (Al), Paper 04