Collaborative Research: Friction Stir Processing of Cast Metal Matrix Nanocomposites

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Incorporation of nanoparticles into light metals, forming metal matrix nanocomposites, can lead to significantly enhanced properties to generate tremendous impacts in the automotive, aerospace, and other industries that demand lightweight structural components in order to achieve high energy efficiency, which also means less air pollution. However, it is very difficult to achieve a good dispersion and capture of nanoparticles during solidification of metals. Effective nanoparticle incorporation into high temperature metal melts also presents a severe problem. Friction stir processing can serve as a powerful tool to disperse nanoparticles in the lightweight metal matrix nanocomposites fabricated by semi-solid processing at a relatively low temperature. This award supports fundamental research to provide knowledge needed to create a simple, novel and scalable manufacturing technology to drive metal matrix nanocomposites toward widespread applications. The research will attract, retain, and engage students from under-represented group. K-12 students/teachers and industry partners will be exposed to the new technology. Interdisciplinary curriculum materials will be developed to train graduate and undergraduate students.The objectives of this collaborative project are to (1) significantly advance the fundamental understanding of how friction stir processing interacts with nanoparticles in lightweight metal matrix nanocomposites, fabricated by semi-solid casting route, through a systematic experimental study on the nanoparticle movements and dispersion inside the grains during processing, and (2) understand the processing-microstructure-properties relations by investigating the effects of nanoparticle size and morphology, nanoparticle loading, and processing parameters on the micro/nano-structural evolution and the resultant mechanical properties of the nanocomposites. The metal matrix nanocomposites for the experimental study will be fabricated through a combination of semi-solid casting and friction stir processing to effectively incorporate nanoparticles in semi-solid state at a relatively-low temperature and disperse nanoparticles and refine microstructures in solid state to achieve superior properties. Through micro/nano materials analysis tools, this study will characterize micro/nano-structures, nanoparticle incorporation and distribution in alloys at semi-solid state and the nanoparticle dispersion by friction stir processing in metal matrix nanocomposites. Tensile and hardness (macro, micro, and nano) tests will be conducted to characterize the mechanical properties of the nanocomposites before and after friction stir processing.