Fracture toughness of fretting obtained TTS in Ti-6Al-4V by in situ notched beam test

Fretting wear is surface degradation caused by reciprocating contact slipping. During gross slip, high surface stress can lead to plastic deformation and the creation of a nanosized grained structure called Tribologically Transformed Structure (TTS) at the surface. The formation and destruction of TTS under fretting influences the wear kinetics as it is the contact material involved. The fracture toughness of Ti-6Al-4V TTS was studied by in-situ notched FIB-machined microbeam bending test in a Scanning Electron Microscope. Two notch geometries were investigated, and digital image correlation tracked the entire displacement field of the beam. Very low toughness was found, confirming that TTS is a brittle layer, very different from white etching layer.