Metal injection moulding of low modulus Ti–Nb alloys for biomedical applications

Titanium alloys containing β stabilising elements such as Nb, Zr and 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 (MIM) attractive. Ti–17Nb alloy parts with densities 94% of theoretical have been produced by MIM of a feedstock based on blended elemental powders. Scanning electron microscopy reveals a typical α−β Widmanstatten microstructure with a precipitated α 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.