Development and testing of fixtures for friction stir welding of thin aluminium sheets

A simple mechanical fixture is proposed to overcome the fixturing issues present in joining of thin sheets. The fixture is similar to a lever type clamp and unlike some common FSW fixtures can hold the thin sheets close to the weld line with precision and uniform pressure. To reduce heat loss, asbestos were used as cover plate. The feasibility of the fixture was confirmed by successfully welding 0.5 mm thin aluminium alloy 6061-T6 sheets at five different tool travel speeds. A joint efficiency (UTSFSW/UTSBasemetal) of 74% and ductility of 8% in terms of percentage elongation were obtained corresponding to 150 mm/min of tool travel speed in which case the weld also withstood 180° bending test. The welds had a distorted shape similar to that of a saddle. The macrostructure indicated that TMAZ area decreased with tool travel speed.