The out-of-phase thermomechanical fatigue behavior of Ultra SCS-6/Ti–24Al–17Nb–xMo (at.%) metal matrix composites

The out-of-phase thermomechanical fatigue behavior of Ultra SCS-6/Ti–24Al–17Nb–2.3Mo (at.%), Ultra SCS-6/Ti–24Al–17Nb–1.1Mo (at.%), and Ultra SCS-6/Ti–24Al–17Nb–0.6Mo (at.%) continuously-reinforced metal matrix composites (MMCs) was investigated in order to understand the effect of Mo on the microstructure and fatigue behavior of titanium–alloy–matrix composites. From the recorded stress versus cycle behavior, two failure regimes were noted. For the highest stresses examined, fatigue-dominated failure occurred. For the lowest stresses examined, a creep-dominated failure occurred. The Ultra SCS-6/Ti–24Al–17Nb–1.1Mo MMC exhibited the shortest fatigue lives for all the applied stress levels examined. The Ultra SCS-6/Ti–24Al–17Nb–2.3Mo MMC exhibited the longest fatigue lives for the lowest applied stress levels, and the Ultra SCS-6/Ti–24Al–17Nb–0.66Mo MMC exhibited the longest fatigue lives for most of the higher applied stress levels.