Metal injection moulding of low modulus Ti-Nb for biomedical applications

Ti alloys containing beta stabilizing elements such as Nb, Zr, Ta are particularly promising as implant materials because of their excellent combination of low modulus, high strength, corrosion resistance and biocompatibility. A low elastic modulus is important for implants to avoid stress shielding and associated bone resorption. The difficulty of producing complex shapes of these alloys by conventional methods makes metal injection moulding attractive. In this work, Ti-17Nb alloy parts with densities of 94% of theoretical density have been produced by metal injection moulding based on a feedstock using blended elemental powders. Scanning electron microscopy reveals a typical alpha-beta Widmanstätten microstructure with precipitated alpha phase layer along the grain boundaries. The parts exhibit an ultimate tensile strength of 768 MPa and a plastic elongation of over 5%. The modulus of elasticity, about 84 GPa, is more than 20% lower than that of CP Ti and Ti-6Al-4V.