Recent developments in cold dwell fatigue of titanium alloys for aero-engine applications: a review

Cold dwell fatigue of titanium alloys used in aero-engine components has threatened flight safety for over five decades. This phenomenon was encountered in Al-containing titanium alloys, occurring at relatively low temperatures, where load hold at applied peak stress result in reduction in number of cycles by an order of magnitude or more (the so-called dwell debit). The present paper reviews the recent advances in dwell-fatigue of titanium alloys with the primary motivation being to understand the dwell-fatigue damage mechanism relating microstructural configurations, dislocations and local strain rate sensitivity. Numerous studies have focused on the identification of fatigue-critical microstructural configurations, such as microtextured regions, rogue grain pairs and (0001) twist grain boundaries. As an example of dwell resistant alloy design, Timetal 575 is a candidate alloy for aero-engine fan disc applications with both superior static and cyclic strengths and low dwell sensitivity.