Fatigue behaviour of friction stir welds without neither welding flash nor flaw in several aluminium alloys

Fully reversed axial fatigue tests have been performed in order to investigate the fatigue behaviour in the friction stir welds of 1050-O, 5083-O, 6061-T6 and 7075-T6 aluminium alloys. In all alloys, the comparative studies on the fatigue behaviour between parent materials and welds have been done. The fatigue behaviour of the welds was sensitive to the microstructures such as stir zone, thermo-mechanically affected zone and heat affected zone. The fatigue strengths of the welds are comparative to or lower than those of the parent materials. The observed fatigue strengths were discussed based on the microstructure and crack initiation behaviour.