New insights into microstructure refinement in crack initiation region of very-high-cycle fatigue for SLM Ti-6Al-4V via precession electron diffraction

Abstract

The formation mechanism of crack initiation region of selective laser melted (SLM) Ti-6Al-4V in very-high-cycle fatigue (VHCF) was investigated by using the novel approach of transmission electron microscopy (TEM) with precession electron diffraction (PED). It is the first time to reveal the microstructure details of nanograin layer in the crack banks of both main crack and sub-crack in SLM Ti-6Al-4V via TEM with PED, which is the result of the crack closure and contacting between fracture surfaces. This revelation provides new insights into the microstructural evolution in the crack initiation region for SLM titanium alloys and other metallic materials, which is helpful for further understanding the crack initiation mechanism in VHCF.