Friction stir welding (FSW) is a solid state welding process in which the relative motion between the tool and workpiece produces heat which makes the material of two edges joined plastic atomic diffusion. This method relies on direct conversion of mechanical energy to thermal energy to form the weld without the application of heat from conventional source. The rotational speed of the tool, the axial pressure, weld speed and the weld time are the principle variables that are controlled in order to provide the necessary combination of heat and pressure to form the weld.