FSP is manufacturing the Technique used to modify the microstructure metals. In this process a rotating tool is penetrated in the work piece and moved in the transverse direction.Further FSP technique is used for fabrication of surface composite on aluminium substrate and homogenization of powder metallurgy aluminium alloy, metal matrix composites, and the cast aluminium alloys. By this process material properties can be improved due to enhancement of grain structure. With this technique the material have shown good corrosion resistance, high strength and high fatigue resistance.

Friction Stir Processing (FSP) is a promising thermomechanical technique that is used to modify the microstructure of metals locally, and thereby locally improve mechanical properties of the material. FSP uses a simple and inexpensive tool, and has been shown to eliminate pores and also reduce the sizes of intermetallics in aluminum alloys. This is of great interest for research on solidification, production and performance of aluminum alloy castings because FSP can enhance the structural quality of aluminum casting significantly by minimizing the effect of those structural defects. In the literature, there is evidence that the effectiveness of FSP can change with tool wear of the tool used. Therefore, a study was first conducted to determine the effect of FSP time on the tool life and wear in 6061-T6 extrusions. Results showed the presence of two distinct phases in the tool life and wear. Metallographic analyses confirmed that wear in Phase I was due to fracture of the threads of the tool and Phase II was due to regular wear, mostly without fracture. Moreover, built-up layers of aluminum were observed between threads. The microhardness profile was found to be different from those reported in the literature for 6061-T6, with Vickers hardness increasing continuously from the the stir zone to the base material. To investigate the degree of effectiveness of FSP in improving the structural quality of cast A356 alloys, ingots with different quality (high and low) were friction strir processed with single and multiple passes. Analysis of tensile test results and work hardening characteristics showed that for the high quality ingot, a single pass was sufficient to eliminate the structural defects. Subsequent FSP passes had no effect on the work hardening characteristics. In contrast, tensile results and work hardening characteristics improved with every pass for the low quality ingot, indicating that the effectiveness of FSP was dependent on the initial quality of the metal. The evolution of microstructure, specifically the size and spacing of Silicon (Si) eutectic particles, was investigated after friction stir processing of high quality A356 castings with single and multiple passes. Si particles were found to coarsen with each pass, which was in contrast with previous findings in the literature. The nearest neighbor distance of Si particles also increased with each FSP pass, indicating that microstructure became progressively more homogeneous after each pass. In the literature, the improvement observed after FSP of Al-Si cast alloys was attributed to the refinement of Si particles. Tensile data from high quality A356 ingot showed that there was no correlation between the size of Si particles and ductility. To the author's knowledge, this is the first time that the absence of a correlation between Si particle size and ductility has been found.

The evolution of mechanical properties and its characterization is important to the weld quality whose further analysis requires mechanical property and microstructure correlation. Present book addresses the basic understanding of the Friction Stir Welding (FSW) process that includes effect of various process parameters on the quality of welded joints. It discusses about various problems related to the welding of dissimilar aluminium alloys including influence of FSW process parameters on the microstructure and mechanical properties of such alloys. As a case study, effect of important process parameters on joint quality of dissimilar aluminium alloys is included.

"Friction stir welding (FSW) is a recently developed process for welding aluminum alloys that has expanded into applications other than welding by the concept of friction stir processing (FSP). Through FSP, it has been found that the properties of materials can be enhanced whether by inserting forged microstructure into a casting, consolidating regions of a part produced by powder metallurgy, or by producing materials with properties which allow them to be formed more easily to name just a few of the applications. The ability of FSP to alter the microstructure of material has lead to its expansion as a method for creating superplastic material ... This study examines the use of FSP to make commercial alloys superplastic by altering the microstructure. Not only is the understanding of the single pass process studied in more detail but the effects of using multiple passes of FSP are examined ... The use of FSP for the addition of carbon nanotubes into aluminum was also evaluated"--Abstract, leaf iv.

Friction stir welding is a solid state welding that use the idea of frictional heat to soften stirred materials without the need of melting. This study is focusing in the effects of single-pass/ double-pass technique on friction stir welding of aluminium. Two pieces aluminium alloy (AA1100) with the same thickness of 6mm were friction stir welded using CNC milling machine. Three different rotational speeds of 1400 rpm, 1600 rpm and 1800 rpm respectively were used for both groups of single-pass and double-pass. Microstructure observation of welded area was studied using metallurgy microscope. All the specimens were tested by using tensile test and Vickers hardness test to evaluate its mechanical properties. Results indicated that at low rotational speeds (rpm) due to defects such as 'surface lack of fill' and tunnel in the welded area contributed to the decreases the result in mechanical properties of the specimens. Welded specimens using double-pass technique shows increasing value of tensile strength and hardness value. Therefore, the optimum parameters in FSW process were double-pass technique with rotational speed of 1800 rpm.