Rotating bending loading and axial loading fatigue tests were conducted to investigate the effect of zirconia shot peening on fatigue properties of Ti-6Al-4V ELI alloy. Specimen was treated in three different shot peening conditions. As a result of the rotating bending fatigue tests, the fatigue lives of shot peened specimen were longer life than non-peened specimen. Fish eyes were observed in the fracture surface of the most shot peened specimen. And there was the facet of α-Ti or the fine granular region near the crack initiation site of the fish eye. And then, fracture morphology of shot peened specimens is different by peening conditions. From the result of axial loading fatigue tests, it becomes obvious that the facet of α-Ti was formed by action of tensile stress over 500MPa without compressive stress and that the fine granular region was formed by action of compressive stress. These results suggested that low level tensile residual stress existed at subsurface near the surface of the SP treated specimen, and the residual stress distribution decided on internal crack origin type between the facet of α-Ti or the fine granular region.
