Deformation in fatigue crack tip plastic zone and its role in crack propagation of titanium alloy with tri-modal microstructure

A combination of scanning electron microscopy and electron backscatter diffraction is used to investigate the deformation in the fatigue crack tip plastic zone and its role in the crack propagation of Ti-6Al-2Zr-1Mo-1V alloy with a tri-modal microstructure. The results show that heterogenous slip and secondary micro-cracks are the main features of the fatigue crack tip plastic zone. These features play important roles in fatigue crack propagation. In particular, the unique lamellar α in the tri-modal microstructure can deflect and delay the crack propagation effectively, thus, improving the fatigue life.