Microstructure and Mechanical Properties of Friction Stir Welded and Processed Joints with the Addition of Nanoparticles: A Review

Background: Friction Stir Welding (FSW) is an efficient process for solid-state joining of two different material without melting by using a non-consumable tool. FSW process was developed for the modification of metallic material microstructure. FSW requires a precise investigation of the process, microstructure, and the welds mechanical properties in order to be used in the fabrication of high- quality engineering components. Through the efforts of improving the weld's mechanical and microstructural properties and conveying the current knowledge of the friction stir to other applications, multiple new technologies have been developed over the time. One of the latest methods to fabricate high performance joints or Nanocomposites alloys is the addition of nano- reinforcements to the joint in Friction Stir Welding (FSW) or the metal matrix in Friction Stir Processing (FSP). Objective: In this study, an overview of the effect of nanoparticles on microstructural and mechanical properties of the FSW/ FSP joints is presented. The review revealed that the most widely employed additions are SiC, SiO2, Al2O3, and graphite nano-powders. Microstructural evolutions, such as grain size, second phase particles, and reinforcement distribution, usually are investigated using optical methods and Scanning Electron Microscopy (SEM). Furthermore, the mechanical properties of the joints, such as tensile strength, hardness, and wear performance, are also investigated. Based on most of the researches, microstructural evolution associated with adding nanoparticles led to improve the joints mechanical properties.