Influence of plastic properties on defects formation in butt and lap welding of aluminium alloys
By Carlos Leitao (CEMMPRE - UC), Maria Inês Costa (CEMMPRE - UC), Dulce Maria Rodrigues (ISISE - UC)

Several authors already addressed the formation of welding defects, in FSW. The studies performed enabled to conclude that meanwhile defects such as tunnels or surface flaws, may be observed in all joint configurations, hooking and cold-lap defects are exclusive of lap joints. Independently of its location and morphology, all the friction stir welding defects were attributed to undesirable material flow during welding and related to a wrong selection of welding parameters or tool geometry. In present study, defects formation in butt and lap welding, of two distinct aluminium alloys (AA6xxx and AA5xxx), was related to the differences in plastic behaviour between the two base material types. The differences in sensibility to defects formation, of the two alloys, for different joint configurations, shows that FSW is more a metal forming technology, than a metallurgical based process.