SEDL / STP / STP675-EB / STP35884S

On the Process of Subsurface Fatigue Crack Initiation in Ti-6Al-4V

Ruppen, J
Graduate assistant, post doctoral research fellow, and professor, Institute of Materials Science, University of Connecticut, Storrs, Conn.

Bhowal, P
Graduate assistant, post doctoral research fellow, and professor, Institute of Materials Science, University of Connecticut, Storrs, Conn.

Eylon, D
University of Cincinnati, Cincinnati, Ohio

McEvily, AJ
Graduate assistant, post doctoral research fellow, and professor, Institute of Materials Science, University of Connecticut, Storrs, Conn.

Pages: 22    Published: Jan 1979

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Abstract

The process of subsurface crack initiation in Ti-6AI-4V has been investigated in some detail. At low stress amplitudes, slip occurs primarily on prism planes and is blocked at α-β interfaces. The piled-up dislocations induce slip in the β-phase under cyclic loading which can lead to the formation of a Cottrell cleavage knife and thereby provide a site for subsurface crack initiation. At high stress amplitudes, pyramidal slip becomes operative and as a consequence a more compatible type of plastic deformation between the two phases can develop. Under these circumstances the tendency for subsurface crack initiation may be reduced.