Ti-Nb-Ta-Zr ALLOYS WITH IRON, SILICON AND AND OXYGEN CONTENT: INCREASING STRENGTH OF LOAD-BEARING IMPLANTS MATERIAL

摘要

Beta titanium alloys are promising materials for load-bearing orthopaedic implants due to their excellent corrosion resistance common for all Ti alloys, enhanced biocompatibility, if favourable alloying elements are used, and low elastic modulus in beta solution treated condition. Biocompatibility requirements restrict the usage of higher amount of alloying elements mostly to Nb, Zr and Ta. In this study, commercial Ti-35Nb-6Ta-7Zr (TNTZ) biocompatible alloy was enriched by low content of Fe, Si and O to increase its strength in beta solution treated condition. 14 alloys with different amount of Fe, Si and O were prepared. Fe, Si and mainly O additions caused a significant increase in tensile strength to more than 1000 MPa, but also increased the elastic modulus (from 65 GPa to 85 GPa). However, these values are still much lower than those of widely used Ti-6Al-4V alloy (115 GPa). Si decreases the elongation to failure, whereas Fe and O increase the uniform elongation thanks to increased work hardening. Material containing 0.7 wt. % oxygen surprisingly shows increased room temperature ductility of the β solution treated material, despite oxygen causes significant embrittlement in α-Ti. In conclusion, Fe, Si and mainly O alloying of commercial TNTZ β-Ti alloy provide promising combination of low elastic modulus, very high strength and reasonable ductility, which makes it a viable candidate for use in load-bearing implants.