Abstract: Carbon ions with a dose of 3×10~(17) ions/cm~2 was implanted into Ti-6Al-4V alloy at an energy of 80 keV.A 28% increase in edurance limit was found with implantation under stress-controlled fatigue tests(R=O).The surface microstructure changes induced by ion implantation were identified using transmission electron microscopy(TEM).The feature of the fracture surface were observed on scanning electron microscope(SEM).The distribution profile of the implanted ions was measured by secondary ion mass spectroscopy(SIMS).The implanted surface layers contain a high density of irradiation defects and fine TiC precipitates.Subsurface crack origins were found in specimens either with or without implantation.The implanted species diffuse into matrix metal under the action of cyclic load- ing.A possible reason and mechanism for improving fatigue lifetime are also discussed.

Key words: surface modification, ion implantation, fatigue