Deformation effects related to pin-tool geometry during friction-stir welding of aluminum alloy 6061

William Charles Davis, University of Texas at El Paso

Abstract

Friction-stir welding (FSW) is a solid-state joining process where a non-consumable pin-tool is plunged, rotated, and traversed along a square butt weld joint using conventional milling techniques. The process involves superplastic deformation and results in a weld zone characterized by dynamically recrystallized, equiaxed grains. FSW has been demonstrated to be a favorable process for the joining of a variety of metals, alloys, and metal matrix composites (MMC). Two particular studies involving the FSW of cast aluminum 359 and aluminum alloy 6061 with 20% SiC MMC document the tool wear phenomena. The studies indicate that a self-optimization process occurs changing the geometry of the pin-tool as it is worn away and altering material flow within the weld zone. This study seeks to evaluate and compare welds made using these two (threaded screw and wear-optimized) pin-tool geometries. ^ Single-pass friction-stir welding was performed along the 4&inches; direction on commercial plates of aluminum alloy 6061 with dimensions of 4&inches; x 2.25&inches; x 0.25&inches;. The plates were clamped on a steel backing plate and the friction-stir welding tool was mounted in a 1.9 cm diameter milling chuck. The plunge depth was 0.025&inches; at the back of the shoulder and a lead angle of 1° was used. The rotation speeds were 500 and 1000 RPM and the traverse speeds were 3, 5, and 7 mm/s. The pin tool geometry was classified as screw or wear-optimized and each pin tool was slightly foreshortened. Samples were examined by optical metallography and Vickers microhardness measurements were taken along a mid-thickness line traversing the weld zone. Grain size measurements were also calculated. ^

Subject Area

Engineering, Metallurgy|Engineering, Materials Science

Recommended Citation

Davis, William Charles, "Deformation effects related to pin-tool geometry during friction-stir welding of aluminum alloy 6061" (2005). ETD Collection for University of Texas, El Paso. AAI1425896.
http://digitalcommons.utep.edu/dissertations/AAI1425896

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