The crack initiation mechanism of the forged Mg–Zn–Y–Zr alloy in the super-long fatigue life regime

In the super-long fatigue life regime (106–109 cycles), the fatigue behavior of the forged Mg–Zn–Y–Zr Mg alloy with T5 temper was studied. The results showed that a pronounced fatigue limit exists in the investigated alloy, with a value of about 85 ± 5 MPa. Fracture observation showed that the crack basically initiated at the surface or subsurface. SEM observation and EDAX analysis indicated that the crack initiation site was covered with a layer of oxide film.