Understanding the effect of particle reinforcement on friction stir weldment: A review

Friction stir welding is a solid-state environment-friendly joining process with many advantages over all fusion welding processes. Many variants in friction stir welding are used for uplifting the process to its maximum possible extent. One such variant is particle reinforcement in the weldment, which is used for improving the mechanical properties by enhancing the metallurgical aspects in the weld region. Generally, micro- and nano-sized ceramic particles are used for reinforcing, which have a much higher melting point than the materials to be joined. From the literature studies, particle size plays a prominent role in attaining better mechanical properties in reinforcing techniques. In addition, an increase in particle size decreases the corresponding mechanical property. Higher heat input conditions like higher tool rotational speed and low welding speed are preferred as they better mix reinforced particles with the matrix material in the weld zone. However, the higher input conditions in the regular friction stir welding process coarsen the grains, thereby deteriorating the mechanical properties of the joint. Increasing the number of passes and switching the direction between the passes leads to uniform distribution of particles and enhance the mechanical properties. This review article's main aim is to understand better reinforcement particles in the weld line of a friction stir welding process. Also, the author emphasizes reinforcing the combination of nano and microparticles to reduce the cost of reinforcement without compromising the mechanical properties. The work mentioned above is missing in the open literature.