Mechanical behavior and fatigue properties of joints by friction stir welding

Mechanical behavior and fatigue properties of the LF2 aluminum joints by friction stir welding (FSW) were studied and the S-N curve of joints were established. The results show that the maximum tensile strength is 252.8 MPa, showing an excellent fatigue properties for FSW welded joints, which is 95.4% of that of the base metal. The fatigue strength was determined to be 59 similar to 65 MPa for the fatigue life of N=10(6) cycles. The microstructure of joints showed comparatively fine equiaxed grains and a narrow heat affecting zone in the FSW welds, which inhibit the growth of crack and produce a long fatigue life. The fracture morphologies also show that the fatigue fracture occurred under alternating stress with the development of persistent slip bands.