TWI

A refill friction stir spot welding technique was employed to fabricate joints in AA 2014 aluminium alloy (Al, 3.51%Cu, 0.7%Mn) sheets (thickness 2 mm) and the effect of tool rotational speed on microstructure and mechanical properties was investigated. Welding was conducted using a modified milling machine and a tool made from heat treated EN 31 series high carbon steel at rotational speeds of 1120-1800 rpm. Microstructures and fracture surfaces were observed by optical microscopy and SEM. Mechanical properties of lap shear samples were characterised by Vickers microhardness measurements and tensile testing at a displacement rate of 0.01 mm/s. Issues discussed include grain refinement in the stir zone and thermomechanically affected zone and enhanced static shear strength for the refill technique compared with conventional friction stir spot welding.

10th International Symposium, 20-22 May 2014, Poster Session, Paper 10