抄録
⊿K-decreasing tests of Ti-6Al-4V were conducted in air and high vacuum environments using compact-tension specimens. Effects of high vacuum environment on fatigue crack propagation characteristics and fracture surfaces were investigated. As a result, the following were obtained. (1) Fatigue crack growth rates in high vacuum were slower than those in air. This trend was dominantly found in Stage 2a region. (2) Fatigue crack growth limit in high vacuum was higher than that in air. (3) Granular substances existed only on the fracture surfaces of Stage 2a region in high vacuum. Similar features were observed on the fracture surfaces of interior-originating fractures.
