Friction Stir Processing of Aluminum Alloys

Sun, Ning

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Friction Stir Processing of Aluminum Alloys

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Friction stir processing (FSP) has been developed based on the basic principles of friction stir welding (FSW), a solid-state joining process originally developed for aluminum alloys. What is attractive about FSP is that it can be incorporated in the overall manufacturing cycle as a post-processing step during the machining operation to provide localized modification and control of microstructures in near-surface layers of metallic components. FSP has emerged as an important post-processing technique, and has been identified as a process that may have a high impact, and perhaps is a disruptive manufacturing process. In this study, FSP has been applied to Al cast alloy A206, which is a high strength, widely used cast alloy in the manufacturing industry. Motivations behind this work are to (1) investigate the feasibility of FSP on manipulating the cast microstructure and strengthening the material, and (2) to explore the viability of FSP to produce a localized particle reinforced zone in cast A206 aluminum components. The thesis will show that we have optimized FSP for processing of Al alloys to locally manipulate the cast microstructure, eliminate casting defects, and attain grain refinement and second phase homogenization. We have established the mechanism leading to the microstructure evolution and have evaluated the resultant mechanical properties, i.e. hardness, tensile property and fatigue properties. We have also synthesized a localized composite material in the A206 work piece with three different reinforcement materials via FSP. These results will be presented and discussed.

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