ABSTRACT
A novel solid state friction stir welding technique is used for joining ferrous and non-ferrous alloys, especially aluminum alloys. The weld quality depends on the tool design and its material properties. Geometry of the tool plays an essential role for the fabrication of good quality welds. Selection of tool material is also an important aspect for the consideration of tool performance, its weld quality, and cost. The concave-shaped tool shoulder produces defect-free welds compared with other shapes. Both sticking and sliding are responsible factors for generation of heat, whereas sticking is only responsible for material flow during operation. The tool wear rate decreased after initial wear and then smoothed (self-optimized) the tool. In this chapter, the friction stir welding tools are reviewed briefly in terms of tool geometry, tool pin (probe) shape, materials, tool failure, and wear behavior.
