2000 Volume 49 Issue 10 Pages 619-624
The crack propagation rate VII in the region II of the relation between crack propagation rate and stress intensity factor has been formulated on the base of a theory of stress-induced hydrogen diffusion proposed by Gerberich. In present study, VII has been evaluated from microstructural factors in Ti-10V-2Fe-3Al alloy. Two different temperatures, i.e. higher and lower temperatures than both β transition temperature and martensite transformation starting points, were used for solution treatment. The difference of VII is about one order between two types of materials. The microstructure of the materials solution-treated at this high temperature consists of very fine α precipitates on the matrix β, while the other materials show relatively coarse α precipitate and primary α phases in the β matrix. VII has been understood to be mainly dependent on hydrogen diffusion coefficient D from the formulation. This study concludes that D is reduced and as a result VII is decreased by the many hydrogen trapping sites on the fine boundaries created through the martensite transformation in the solution treatment.