FRICTION STIR WELDING OF TAILORED JOINTS FOR INDUSTRIAL APPLICATIONS

Friction stir welding (FSW) is an energy efficient and environmentally "friendly" (no fumes, noise, or sparks) welding process, during which the workpieces are welded together in a solid-state joining process at a temperature below the melting point of the workpiece material under a combination of extruding and forging. Since its invention in 1991 by TWI, such process has been reaching a continuously increasing popularity among aerospace, automotive and shipbuilding industries due its capability to weld unweldable or difficult-to-weld light alloys in different joint morphologies. In this paper a wide experimental campaign is carried out in order to obtain T and lap joints characterized by dimensions of industrial interest from two sheets, the stringer and the skin, of different materials. In particular a peculiar clamping fixture has been designed in order to assure a perfect contact between the stringer and the skin and to develop the "transparency" welding; a proper welding tool has been utilized allowing to obtain at the same time a sound joint and the designed final component fillet radii. Finally T-pull tests together with macro and micro observations have been developed at the varying of the main process parameters.