ABSTRACT
Hard materials such as high-strength steels, advanced high-strength steels, Ni-based superalloys and titanium alloys, are difficult to weld through usual conventional friction stir welding processes with relatively softer materials like Al and Mg alloys due to their distinct thermophysical properties. Hybrid friction stir welding in combination with secondary heat sources like plasma, ultrasonic laser, induction, arc and electric current has helped in reducing the plunging force, enhancing tool life by decreasing stresses on the tool. By using the secondary heat source, the yield strength value has been reduced, which in turn has increased the plasticity of the material and hence the material flow behavior. This has also helped in minimizing the tool cost. This article aims to discuss hybrid friction stir welding, where various types of secondary heat sources to weld the relatively harder materials have been employed. The comparative research in the field of similar and dissimilar hard materials using hybrid heat sources in friction stir welding is still in its preliminary stage, this chapter will provide a reference to the researcher so that it can be applied for similar and dissimilar types of the weld by using a different secondary heat source.
