On the sharp bend of the S–N curve and the crack propagation behavior of extruded magnesium alloy

Rotating bending fatigue tests were carried out using an extruded magnesium alloy in order to determine the shape of its S–N curve, and the crack initiation and propagation behavior. It was found that a well-defined knee in the S–N curve was related to the layered microstructure of the alloy, and that fatigue cracks initiated early stage in the fatigue life. The crack propagation behavior was analyzed using a modified linear elastic fracture mechanics parameter to predict crack growth behavior and the fatigue lifetimes.