Research prospects of friction stir additive manufacturing (FSAM).

Friction stir additive manufacturing (FSAM) is a recently developed additive manufacturing method that involves friction stir welding (FSW) of sheets/plates placed in a lap fashion, layer over layer, as the background of the process. As the process of FSW is done at 70 to 90% of the workpiece's melting temperature, equiaxed grain structures are obtained in the processed zone at the layer interface. For an acceptable mechanical property in the FSAM build structures, it is required that an optimized set of process parameters which mainly includes the tool's rotational speed, travel speed, its geometry/feature, plunging force/depth, and the boundary conditions such as backing plate material and the surrounding temperature, are used. In this review paper, the work done in FSAM are covered, which mainly includes process parameter optimization and the corresponding microstructural behaviour affecting the final mechanical property such as hardness and tensile strength of various metals and composite materials. In the end, based on the available literature in this field, various research prospects of FSAM are presented. [ABSTRACT FROM AUTHOR]