Recent Developments in Hybrid Surface Metal Matrix Composites Produced by Friction Stir Processing: A Review

Abstract

The metal matrix composites combine the metallic properties of a tough and ductile matrix with properties of reinforcement particles, simultaneously develop the functional properties by proper selection of reinforcements for projected applications. However, hard ceramics reinforcements decrease toughness and ductility of soft matrix and restrict their wide applications. The surface metal matrix composites (SMMCs) preserve the matrix properties with added advanced surface properties by reinforcing particles only in the surface layer. The hybrid surface metal matrix composites (HSMMCs) with more than one reinforcement gained attention in material processing due to their noble tribological behavior and surface properties, which cannot be attained in mono composites. Conventional liquid-phase processing techniques to fabricate hybrid surface composites result in the formation of undesirable brittle compounds, detrimental to desirable properties of composites. Friction stir processing (FSP), a solid-state processing technique, has been used by many investigators using different reinforcements to fabricate mono as well as hybrid surface composites. Friction stir processed (FSPed) hybrid surface composites have not been extensively reviewed. The current review provides a comprehensive understanding of the latest developments of FSP in hybrid surface composites manufacturing. This paper review different reinforcement strategies in the fabrication of FSPed hybrid surface composites and also the effects of single-pass, multipass, and change in pass direction on microstructure and resultant properties. Finally, future directions and challenges to FSPed hybrid surface composites are summarized. This review article containing important information on hybrid surface composites fabrication by FSP will be useful to academicians and investigators in the field.