| Summary: | 碩士 === 國立臺灣海洋大學 === 機械與機電工程學系 === 105 === 7000 series aluminum alloy have been widely utilized in aeronautic industry, bridge, highly stressed structures. Using traditional welding can’t obtain great jointed quality. 7050 aluminum alloy have high strength and high content of zinc but when alloy melts it will makes micro holes and poor jointed quality in welding bead. Friction Stir Welding don’t approach melting point, so there’s no micro hole and cracking of solidification, suitable for application of aluminum welding. The aims of this study is to apply Friction Stir Welding, comparing different welding parameters and mechanical properties. Utilize Taguchi method to attempt experimental parameters include feed rate, rotating speed, dimension of pushing down and holding time. The experimental results are shown most of cracking concentrated on the bottom of stirring area, but microstructure of Friction Stir Welding do not have macro holes in welding bead. Hardness of 7050 aluminum alloy elevate greatly because of plastic deformation and grain refining by FSW. Whether horizontal or vertical welding bead make hardness of 7050 aluminum alloy elevate, but elongation decrease significantly. Welding bead of 7050 aluminum alloy make hardness degrade by FSW. Friction Stir Welding is not suitable for 7050 aluminum alloy welding.
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