A Review on Recent Progress in Solid State Friction Based Metal Additive Manufacturing: Friction Stir Additive Techniques

Friction stir additive techniques (FSATs) constitute innovative approaches aimed at utilizing layer by layer additive manufacturing (AM) principle with solid state friction stir welding (FSW) technique. These constitute a special class of friction based additive techniques (FATs) and can be easily thought of as major breakthrough of metal additive manufacturing (MAM) domain. Ability of MAM techniques to be used for fabricating intricate parts has led them to be considered as a lucrative option for aviation, automotive, and marine sectors. However, fusion based MAM techniques have manifold limitations mainly owing to solidification related as well as poor shear strength issues. FATs overcome drawbacks of fusion based MAM methods chiefly because of their solid-state nature. FATs fabricate defect free components possessing superior structural and mechanical characteristics. Basic principles of additive manufacturing and FSW necessary for highlighting need and concept of FATs are introduced first. All FATs with their basic principles and specific merits are then presented. Special emphasis is given to two most effective FATs based upon FSW, i.e., FSATs which are friction stir additive manufacturing and additive friction stir (AFS). Aim of this work is to present a critical review of timeline and recent developments in the field of FSATs. In addition, challenges and future trends of these innovative techniques are highlighted followed by detailed discussion.