Microstructural origin of flutes and their use in distinguishing striationless fatigue cleavage from stress-corrosion cracking in titanium alloys

Postfracture analysis does not always distinguish striationless low-stress fatigue from stress-corrosion cracking (SCC), since both are characterized by cleavage, together with other less distinct fracture modes. Studies of identical specimens of Ti-8A1-1Mo-1V broken under both conditions suggest that the presence of certain microplastic fracture features called flutes may be uniquely characteristic of SCC, and absent from low-stress striationless fatigue fractures. Some new observations concerning the microstructural origins of flutes verify that they arise from a tendency toward planar slip in a and α-β alloys and from the presence of multiple cleavage during crack propagation under certain circumstances, including SCC.