Fatigue Behaviour of Friction Stir Welded Rolled Thick Plates of AA7075-T651 Aluminium Alloy Joints

The fatigue strength of welded joints represents the core problem for their industrial applications. Friction stir welding (FSW) demonstrated the enhancement of fatigue resistance for aluminium alloys, with respect to traditional fusion techniques. The aim of the present work is to evaluate the fatigue properties of 12 mm thick AA 7075 -T651 aluminium alloy plates joined by friction stir welding (FSW) process. The fatigue properties were evaluated under uniaxial tensile loading condition (stress ratio = 0.1, Frequency=10Hz) at room temperature using servo-hydraulic controlled machine. The fatigue endurance (S-N) curves of the welded joints and unwelded parent metal were constructed. The resultant fatigue properties were correlated with the tensile, hardness and microstructural characteristics of welded joints. The mode of failure was analyzed through scanning electron microscopy. It is found that the fatigue life of friction stir welded AA 7075- T651 Aluminium alloy joints is appreciably lower than unwelded parent metal but it is higher than fusion welded joints.