2008 Volume 49 Issue 4 Pages 885-888
The microstructure, mechanical properties and thermal stability of double friction stir welded 2219 Al alloy were investigated. The grain size of the double friction stir zone was about 0.8 μm, which was smaller than that of the single friction stir zone. The dissolution of the very fine strengthening particles resulted in a decrease of the hardness values in the single and double friction stir zone. Following the post weld heat treatment (PWHT), the grain structure of the double-FSW joints was found to be more unstable than that of the single-FSW joints, owing to the finer grain size, higher fraction of sub-grains and lower particle density.