Abstract
The fatigue strength has been investigated about the plastic deformed specimens by roller-working in Ti-6Al-4V alloy with a notch by 4 kinds of plastic deformation ratio. The results in this test are summarized as follow: (1) Though the hardness number of roller-worked materials are higher than those of non-deformed Ti-6Al-4V alloy, the fatigue limit of roller-worked materials becomes deteriorated in spite of roller-working. Low work-hardening ratio of Ti-6A1-4V alloy may not contribute to the improved hardness and residual stress. (2) Fatigue fracture had occurred in the boundary (weak part) between plastic deformed area and non-deformed area where tensile residual stress would exist. (3) The results of the SEM observation, the roller-worked specimen showed crack initiating from the one point on the surface. It shows two-step fracture modes, which are shear fracture mode and normal one. (4) The fatigue limit of at the plastic deformed area seemed to be improved. It is necessary to further study the qualitative analysis of residual stress at the plastic deformed area.
