Abstract: The reliability and durability of materials in service are the assessment foundation of the structural safety. Aimed at the 7N01 aluminum alloy experienced a long term service in high speed trains， the fatigue mechanical properties were investigated in laboratorial atmosphere， and the fatigue cracks propagation (FCP) behaviors of materials with/without service were analyzed. The results showed that the experience of service deteriorates the mechanical properties， showing a regular decline trend. The da/dN-ΔK curve in the FCP zone after service showed a turning phenomenon， and a piecewise Paris’ curve fitting method was used to describe the FCP behavior. The results of the fracture surface morphologies showed that the are crack initiation zone， steady growth zone and rapid growth zone of 7N01 alloy after service corresponding to cleavage fracture mode， mixed plastic and cleavage fatigue striation， and mixed intergranular and transgranular fracture， respectively.

Key words: 7N01 aluminum alloy, fracture mechanics, fatigue crack propagation, turning phenomenon, fracture morphology