Microstructure and fatigue behaviors of a biomedical Ti–Nb–Ta–Zr alloy with trace CeO 2 additions

Abstract

Abstract The new β-type Ti–29Nb–13Ta–4.6Zr (TNTZ) alloy containing trace amounts of CeO2 additions has been designed as a biomedical implant with improved fatigue properties achieved by keeping Young׳s modulus to a low value. The results show that the microstructure is refined by the addition of CeO2; the β grain size becomes a little larger when Ce content increases from 0.05% to 0.10%. This occurs because dispersed CeO2 particles can act as nucleation sites for β grains; thus, the effect of rare earth oxides on microstructure refinement mainly depends on the size and dispersion of the rare earth oxides. Young׳s moduli of TNTZ with CeO2 additions are maintained as low as those of TNTZ without CeO2, while the fatigue limit is highly improved. The 0.10% Ce alloy exhibits the best fatigue strength among the experimental alloys; its fatigue strength is increased by 66.7% compared to that of pure TNTZ. The mechanism by which rare earth oxides affect fatigue performance is dominated by dispersion strengthening. The stiff rare earth oxides can hinder the movement of dislocations, resulting in resistance to the formation of fatigue cracks. Rare earth oxides also change the crack propagation direction and the crack propagation route, effectively decreasing the crack propagation rate.