Metallurgical and mechanical properties of Ti–24Nb–4Zr–8Sn alloy fabricated by metal injection molding

Abstract

Metastable β-titanium alloys are especially favourable as implant materials because this type of Ti alloy containing β stabilising elements such as Nb, Zr and Ta has an excellent combination of low modulus, high strength, corrosion resistance and biocompatibility. A low elastic modulus reduces the risk of stress shielding and associated bone resorption. The difficulty of producing complex shapes of these alloys by conventional methods for reasonable costs makes Metal Injection Moulding (MIM) attractive. In this work, the results of using MIM to process successfully Ti–24Nb–4Zr–8Sn alloy powder are presented. Specimens with relative density up to 97.6% have been produced using a feedstock based on wax-polymer binder. Microstructure observations reveal a pure β microstructure with TixC precipitates along the grain boundaries. The carbides form due to reaction of titanium with binder residuals and deteriorate the plastic behaviour. However, the specimens exhibit an ultimate tensile strength within the range from 655 to 720 MPa and a plastic elongation ranging between 2% and 9% in dependence on sintering parameters. The lowest Young’s modulus is about 54 GPa and this value is about 50% lower than that of CP Ti and Ti–6Al–4V.