Electron back scattered diffraction characterization of thermomechanical fatigue crack propagation of a near α titanium alloy Timetal 834

Fatigue crack growth (FCG) mechanisms have been studied in light of the interaction of a propagating crack with local crystallographic orientations of primary alpha (alpha(P)) and secondary alpha (alpha(S)) colonies in a near alpha Timetal 834 Ti-alloy under thermomechanical fatigue (TMF) loading using electron backscattered diffraction (EBSD). FCG testing at in-phase (IP) and out-of-phase (OP) TMF loading have been carried out at two temperature intervals 300 degrees C <-> 450 degrees C and 450 degrees C <-> 600 degrees C. EBSD analysis and microhardness measurements have confirmed that larger cyclic plastic zone size at the crack tip leads to lower crack propagation under IP-TMFCG loading as compared to OP-TMFCG loading. EBSD analysis has also confirmed that crack dissipates more energy to propagate when it passes from a soft grain oriented with its c-axis normal to the loading direction and encounters a hard grain with its c-axis parallel with the loading direction. (C) 2014 Elsevier Ltd. All rights reserved.