Appeal No. 2004-1150
Application No. 09/924,490
components and causing relative movement between the probe and
components whereby frictional heat is generated to cause portions
of the components in the region of the joint to take up a
plasticized condition, and moving the probe relative to the
components to allow the plasticized portions formed in front of the
probe to move behind the probe, thus allowing the plasticized
portions to solidify into a weld joint (page 42; Figure 2). Thus,
Dawes discloses a method of joining two components by utilizing a
friction stir welding technique. The welding technique disclosed
in Dawes is particularly well suited for joining components made of
aluminum alloy (page 42, first column). Moreover, the friction
stir welding technique of Dawes may be used to form a variety of
different welded joints, including butt or lap joints (page 42;
Figures 2 and 7). In contrast to some other welding techniques,
the Dawes welding technique can achieve welds that are completely
void and crack free (page 42, second column). Because friction
stir welding produces a finer grain structure than the base metal
itself, tensile failure of friction stir welded components occurs
in the base metal rather than in the HAZ (heat-affected zone) or
the weld metal (paragraph spanning pages 42-43; Figure 5). Fatigue
performance of friction stir welds is far better than has been
obtained from several known arc welding techniques and comparable
5
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