Ti-6Al-4Vの微小疲労き裂進展に与える超高真空の影響

抄録

Small fatigue crack propagation tests were conducted on Ti-6Al-4V in ultrahigh vacuum, air, and argon to fully examine the effects of vacuum on small crack growth processes. It was found that the crack propagation rate was significantly lower in vacuum than in air. The crack propagation rate in argon matched well that in air in the small crack regime; however, it agreed with that in vacuum in the long crack regime. Additionally, the fracture surface appearance in argon was quite similar to that in air in the small crack regime; on the other hand, the similarity in the fracture surface was found between vacuum and argon in the long crack regime. These tendencies in the fracture surface are coincident with those found in the crack propagation rate. Therefore, the different trends in the crack propagation rate in argon depending on the crack length obviously reflect the different crack growth behaviors. These results allowed us to conclude that the existence of gases has dominant effects on the small crack propagation, even if they are chemically inert.