Abstract
The effects of shot peening on the axial fatigue properties of Ti-6Al-4V were examined in connection with residual stress and microstructure. Double edge notched plate specimens with the stress concentration factor 1.63 were prepared. By shot peening, compressive residual stress was introduced into the surface layer of approximately 70μm in depth, which showed the maximum value of 600MPa. Fatigue tests were carried out at R=0.05. The fatigue strength of the shot peened specimens increased by about 1.3 times that of the unpeening specimens. The fatigue crack initiaion site in the shot peened specimens was at about 150 to 180μm below the specimen surface. In the unpeened specimens, however, a fatigue crack was initiated within α phase microstructure at the specimen surface of the notch root. The increase of fatigue strength in the shot peened specimens might be due to a shift of the initiation site from the surface to the subsurface. The surface residual stress in the shot peened specimen measured by an X-ray diffraction method slightly decreased during cyclic loading.
