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Friction stir welding was employed to fabricate bead-on-plate welds on AA 6063 aluminium alloy sheets (thickness 5 mm) and dissimilar joints between AA 6063 and S45C carbon steel plates (thickness 6 mm), and the influence of weld shape on microstructure and mechanical properties was investigated. Welding experiments were conducted at a rotational speed of 1000 rpm, welding speed of 200 mm/min and plunge depths of 4 or 4.2 mm. For comparison, a linear weld and curved welds (radius 20-50 mm) were studied under several sets of conditions. Cross-sectional microstructures and fracture surfaces were observed by optical microscopy and SEM. Mechanical properties were characterised by hardness measurements and room-temperature tensile tests. The relationship between weld shape induced changes in microstructure and mechanical behaviour and the precipitation dissolution process during welding are discussed.

10th International Symposium, 20-22 May 2014, Session 10A: Microstructure and Properties, Paper 04