Effects of Nb on Superelasticity and Low Modulus Properties of Metastable β-Type Ti-Nb-Ta-Zr Biomedical Alloys

In this work, a series of Ti-xNb-2Ta-3Zr (x = 25, 30, 35, 40 wt.%) alloys are designed, and the transformation of beta-phase to alpha '' martensitic, beta-phase stability, microstructure, mechanical properties and corrosion performance of these alloys are investigated. The phase analysis shows as the Nb content increases, the alpha '' phase in these alloys decreases, while the intensity of the two main peaks beta(110) and beta(211) of Ti-40Nb-2Ta-3Zr alloy is reduced. These results can be attributed to the variation of beta-phase stability caused by Nb element of alloy and cold rolling process. The mechanical properties test shows that the elastic modulus (52GPa) of the Ti-35Nb-2Ta-3Zr alloy is the lowest and the elongation (18.8%) is the maximum. In addition, the alloy is susceptible to beta-phase elastic deformation and stress-induced martensitic transformation resulting in the highest recovery strain of the alloy (66.87%). The polarization curves show that the Ti-35Nb-2Ta-3Zr alloy has the highest corrosion potential (-0.34V) and the lowest corrosion current density (0.21 mu A cm(-2)) exhibiting the best corrosion resistance.