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Abstract

A method of root closure of friction stir welds in all types of stir weldable materials, especially difficult to weld materials, such as non-extrudable aluminum alloy 2024, 2014, 2090 and 7075. The method includes providing a backing device that has a recess, such as a groove or channel, sized to receive the tip of the pin of the welding tool and to contain the bead of the weld being formed. The workpiece rests on the backing device, with the proposed weld line aligned with the recess. Thus, as the weld is formed, material is extruded into the recess, completing closure of the weld root, and forming a small bead on the rear side of the workpiece. Optionally, this bead may be removed by a machining process. In one embodiment, the backing device is a plate with a channel machined in its surface so that the workpiece may be temporarily affixed to the plate, with weld line aligned with the channel, for welding. In an alternative embodiment, the backing device is a roller, mounted beneath the rotating pin of the friction stir welding tool, with a circumferential groove on its exterior surface, sized to receive the pin tip and contain the weld bead as the weld is being formed.

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First Claim