Low magnification electron fractographs of the cup and cone fatigue fracture showed parallel markings which are said to be characteristics of the stage I fatigue crack. However, high magnification fractographs of the etch pitted fracture surfaces revealed {100} fracture surface-<110> crack propagation direction and striations as well as {111} surface-<110> direction. This suggests that the opening and closing mode mechanism of fatigue crack propagation is operating as well as the shear mode mechanism in spite of the same fracture surface appearance as the stage I crack. A correlation of the fracture with the texture of material is also suggested.
