Micromechanisms of crack initiation of a Ti-8Al-1Mo-1V alloy in the very high cycle fatigue regime

Abstract Fatigue behavior and damage mechanisms of a Ti-8Al-1Mo-1V alloy were investigated in the very high cycle fatigue (VHCF) regime. Fracture surfaces and slip morphologies of failed specimens were observed to reveal the crack-initiation micromechanisms. The crack initiation area is characterized by nano-marking facets and flat facets surrounded by tearing topography surface (TTS). The VHCF crack initiation is attributed to the formation of nano-marking facets and flat facets in αp grains induced by dislocations and slip activity. The slip activity is the main micro-deformation mechanism while a large scatter in fatigue life can be attributed to slip inhomogeneity.