TWI

6061-T6 aluminium alloy (Al, 0.96%Mg, 0.59%Si) sheets (thickness 1 mm) were joined by friction stir spot welding (FSSW) under low rotational speed conditions and the microstructure and mechanical properties of the welded joints were investigated. FSSW was performed using both a flat tool and a tool with a probe at rotational speeds no greater than 50 rpm (to decrease peak welding temperature), applied load of 31.1-71.2 kN and dwell time of 30 s. A digital thermal camera was employed to record temperature distribution during welding. Microstructure was observed by optical microscopy, SEM, electron backscatter diffraction and TEM. Mechanical properties were characterised by Vickers hardness profile measurements and shear tensile tests. The occurrence of ultrafine grained structure formation in the stir zone and high maximum shear tensile strength is discussed.

11th International Symposium, 17-19 May 2016, Poster Session, Paper 15