Comparative study of very high cycle tensile and torsional fatigue in TC17 titanium alloy

Abstract Very high cycle tensile and torsional fatigue of TC17 titanium alloy with bimodal microstructure have been firstly and comparatively studied at the stress ratio of 0.1. Like the tensile cracks, torsional cracks were substantiated to nucleate from specimen surface or interior sites and presented in a fatigue life-dependent mode. Internal tensile and torsional fatigue cracks with faceted morphology were analyzed with the help of focus ion beam and unraveled to initiate in modes II +III. Particularly, short crack branching and deflection beneath the crack initiation rough area can be observed for torsional loading condition.