Fabrication of surface metal matrix composites for structural applications using friction stir processing – A review

Surface metal matrix composites (SMMCs) are the best choice materials for recent advanced engineering applications. In this regard, friction stir processing (FSP) is gaining popularity as a promising method for producing SMMCs. FSP is extensively used to make magnesium and aluminum based SMMCs. In addition, this technique is also suitable to produce surface composites made from steel, copper, and titanium-based alloys. The FSP of metals can improve the mechanical properties e.g., ductility, strength, fatigue life, abrasion resistance, corrosion resistance, hardness, and formability. This paper provides a comprehensive overview of FSP of single and hybrid fillers reinforced SMMCs along with the influence of process parameters to enhance the mechanical properties and tribological behavior of SMMCs. Tool variables and processing parameters frequently influence the properties of FSPed SMMCs. Due to the significant impact of tool variables at high melting temperature zone, especially for the hard SMMCs, a quick word on tool design parameters and their limitations are systematically presented. The numerous research articles are reviewed in detail to determine the effects of tool and process parameters, multiple passes of the tool in the process zone, and reinforcing particles on grain refinement during fabrication of SMMCs. To determine the effective machine/process parameters, it is necessary to examine the underlying mechanisms involved during FSP thoroughly. With the help of reported models, the fundamental mechanisms in the strengthening of FSP manufactured SMMCs are examined in this paper. Enhancements of mechanical properties and wear behavior on aluminum SMMCs due to mono and hybrid reinforcements are also reviewed. Common defects during processing and their remedial are deliberated. FSP technique has several research needs, such as producing customizing microstructures with defect-free composites are also discussed in this study. © 2021