Selection of Welding Conditions for Butt Friction stir welding of Al and Cu
By Toru Nagaoka (Osaka Research Institute of Industrial Science and Technology), Takeshi Kyouda (Fuji Terminal Industry Co., Ltd.), Shao Tongge (Beijing Institute of Petrochemical Technology), Hua Zhang (Beijing Institute of Petrochemical Technology)

Tool offset is very important for butt friction stir welding of Al plates and Cu plates. In this study, the tool probe was shifted 2.9 mm, 3.0 mm, and 3.1 mm from the weld center line to Al side. The diameter of cylindrical threaded probe was 6.0 mm. When the tool offset was 2.9 mm, some fragments of Cu and some voids were observed in the Al side after FSW. The voids were formed because Cu fragments acted as a barrier to material flow in the stir zone. When the offset was 3.0 mm and 3.1 mm, the amount of Cu fragments was decreased. No voids were observed in the Al side. However, root flaw was likely to be remained at the bottom of the faying surfaces. Increase of tool rotating rate and decrease of tool tilt angle could suppress the root flaw.