1994 年 43 巻 488 号 p. 502-508
The characteristics of the stage 2 fatigue crack growth was investigated in Ti-6Al-4V alloy, in order to clarify the influence of microstructure and stress ratio. The fatigue tests were carried out at the stress ratio, R, of 0.1, 0.5 or 0.8 by using annealed (AR) and solution treatment-and-aged (STA) materials. The microstructure of AR material was coarse and anisotrophic in comparision with that of STA material.
The fracture surface and the cross section of fatigue cracks were observed on both materials, and the relationship between the da/dN-ΔKeff curve and the observed results were discussed.
(1) The da/dN of AR material was lower than that of STA material because the fatigue crack grew zigzag.
(2) The ΔKeff·th at R=0.8 in AR material was higher in comparison with those at other stress ratios because the secondary cracks with a length of about 100μm were generated.