S-N curves of welding joint were established by investigating fatigue behavior of LF2 aluminum alloy joint for stirring friction welding. The experimental results show that fatigue strength of stirring friction welding joint is about 59

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5 MPa at fatigue life N=10

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showing excellent fatigue behavior. Fatigue behavior of the joint was improved due to fine equiaxed grain and narrow heat effect zone inhibiting formation of slide-zone and propagation of crack. Fatigue fracture analysis shows that failure occurs at the condition of alternative stress with crack formation resulting from propagation of stayed slide zone.