A study on the effect of stacking fault energy on fatigue crack propagation as deduced from dislocation patterns

Fatigue tests of crack growth rates and transmission electron microscopy in the immediate vicinity of crack tips were performed on specimens of copper and 70/30 brass. In brass, very dense dislocations accumulated on the primary and the conjugate slip planes were observed just ahead of the crack tips, and they appeared to be not easy to move because of the difficulty of cross slip. In copper, well-defined cells were observed around the crack tips and there were frequently found cracks propagating along or across cell boundaries. On the basis of these observation results, an interpretation is put on the effect of stacking fault energy on fatigue crack growth.