Abstract: When a friction stir weld tool penetrates the interface of two workpieces of dissimilar metal alloy materials, the resultant weld of the different alloy materials may produce a weak weld joint. Such weak joints are often experienced, for example, when attempting to form spot welds or other friction stir welds between a magnesium alloy sheet or strip and an aluminum alloy sheet or strip. It is discovered that suitable coating compositions placed at the interface of assembled workpieces can alter the composition of the friction stir weld material and strengthen the resulting bond. In the example of friction stir welds between magnesium alloy and aluminum alloy workpieces, it is found that combinations of copper, tin, and zinc, and other powders can strengthen the magnesium-containing and aluminum-containing friction stir weld material.

Abstract: When a friction stir weld tool penetrates the interface of two workpieces of dissimilar metal alloy materials, the resultant weld of the different alloy materials may produce a weak weld joint. Such weak joints are often experienced, for example, when attempting to form spot welds or other friction stir welds between a magnesium alloy sheet or strip and an aluminum alloy sheet or strip. It is discovered that suitable coating compositions including an adhesive placed at the interface of assembled workpieces can alter the composition of the friction stir weld material and strengthen the resulting bond. In the example of friction stir welds between magnesium alloy and aluminum alloy workpieces, it is found that combinations of an adhesive with copper, tin, zinc, and/or other powders can strengthen the magnesium-containing and aluminum-containing friction stir weld material.

Abstract: A device for use with a welding apparatus, such as a friction stir spot welding (FSSW) apparatus, that maintains work pieces in a generally flat or flush orientation during a welding operation. The device can be mounted to the operable end of an FSSW apparatus so that it exerts a stabilizing force against an upper work piece. The stabilizing force exerted by the device prevents the upper work piece from deflecting when the rotating tool of the FSSW apparatus passes through the upper work piece and penetrates into the lower work piece. In an exemplary embodiment, the device includes a housing component that slidably receives a movable component under the force of a biasing component.

Abstract: The present invention provides an apparatus and improved method of friction stir spot welding that assures a predetermined bottom thickness and a reduction in variation in a series of resultant spot welds. The advantage of the present invention lies in that the plunge distance is controlled from the top plane of the anvil against which the bottom thickness is specified, and systematically adjusted to account for changing system parameters, such as, but not limited to, deflection and thermal expansion of the weld gun. The present invention also provides for improved and controlled weld quality through implementation of a dwell operation or dwell operations, whereby weld heat input is manipulated by causing the weld tool to dwell in a dwell region or at a desired depth or depths within the workpiece(s) for a predetermined time interval to achieve desired mechanical properties of the resultant weld joint.