Insights into the fatigue property of titanium alloy Ti-6Al-4V in aero-engine from the subsurface damages induced by milling: state of the art

Titanium alloy Ti-6Al-4V is extensively employed in aero-engine as blade, disk, and casing components, which have a high risk to occur fatigue failure. The milled subsurface damage is one of the critical factors influencing fatigue property. This paper has a comprehensive overview on the subsurface damage in titanium alloy Ti-6Al-4V induced by milling. It was found that the milled subsurface damage was mainly the Ti-6Al-4V plastic deformation including the changes of grain size and shape (such as grain refinement); however, the phase transformation was not observed. Such subsurface damage results in compressive residual stress (− 266 MPa ~ − 528 MPa) and work hardening (375 HV~410 HV), which significantly affect the material’s fatigue property. Nevertheless, some studies reported that no subsurface damage appeared in titanium alloy Ti-6Al-4V after milling. This might be owning to the limitation of detection method. In particular, a novel methodology was proposed to study the fatigue life of components based on the interrelationship among machining, structure, and property. Lastly, several fundamental questions necessitating further researches are recommended herein.