OS07W0142 Fatigue characteristics of low rigidity titanium alloy, Ti-29Nb-13Ta-4.6Zr, for biomedical applications

Abstract

Plain fatigue strength of cold-rolled and forged Ti-29Nb-13Ta-4.6Zr(TNTZ) aged after solution treatment is much greater than that of TNTZ conducted with solution treatmet in both low cycle fatigue and high cycle fatigue life regions. The plain fatigue strength of TNTZ is not degraded in Ringer's solution. Fretting fatigue strength of forged TNTZ and Ti-15Mo-5Zr-3Al conducted with various heat treatments decreases dramatically as compared with their plain fatigue strength in both low cycle fatigue and high cycle fatigue life regions. In this case, the decreasing ratio of fretting fatigue life increases with increasing the small crack propagation area where both the tangential force and frictional force exist at the contact plane of pad. In fretting fatigue in air, the ratio of fretted damage (P_f/F_f), where P_f and F_f stand for plain fatigue limit and fretting fatigue limit, respectively, increases with increasing elastic modulus. In fretting fatigue in Ringer's solution, the passive film on specimen surface is broken by fretting action in TNTZ, which has excellent corrosion resistance, and, as a result, corrosion pits that lead to decreasing fretting fatigue strength especially in high cycle fatigue life region, are formed on its surface.