CRYSTALLOGRAPHIC STUDY OF FATIGUE CRACKING IN NI3AL(CRB) SINGLE-CRYSTAL

The effect of crystallographic orientation on the fatigue-crack initia tion and propagation in Ni3Al(CrB) single crystal was studied using a compact-tension specimen. Stage I crystallographic cracking and cleava ge fracture were observed, Crystallographic cracking can occur on two or more {111} slip planes simultaneously. It was shown that the thresh old stress intensity for crack initiation from the notch root exhibits a dependence on crystallographic orientation, In addition, an effect of orientation on microcracking behavior was also shown. The number of {111} planes intersecting with each other determines the different mi croscopic features on the cleavage fracture surface.