Ti-6Al-4Vの超高サイクル疲労における内部破壊初期過程の放射光μCTイメージング

抄録

The initial process of internal fracture in Ti-6Al-4V was non-destructively observed by synchrotron radiation μCT imaging to clarify the crack initiation and initial growth behavior in very high cycle fatigue. As a result, a number of cracks were detected all over the observation volume. The internal crack firstly initiated at around 5.0 × 10⁶ cycles, however, the initiation lives of these cracks varied widely. The just initiated crack propagated microstructure-sensitively at significantly low growth rate. Some cracks initiated so early and propagated so slowly, but others initiated so lately and propagated so rapidly. As above, the crack initiation sites and lives widely varied, and the crack growth rate just after the initiation has a large scatter. These results let us to conclude that the local microstructural conditions and the effect of environment around the crack are indispensable factors to fully understand the initial process of internal fracture in very high cycle fatigue.