SEDL / STP / STP1272-EB / STP16069S

New Titanium Alloys to be Considered for Medical Implants

Okazaki, Y
Research scientist, Mechanical Engineering Laboratory, Agency of Industrial Science and Technology, Ministry of International Trade and Industry, Tsukuba,

Ito, Y
Research scientist, Technical Development Group, Kobe Steel, LTD., Kobe,

Ito, A
Research scientists and manager, Bionic Design Group, National Institute for Advanced Interdisciplinary Research, Tsukuba,

Tateishi, T
Research scientists and manager, Bionic Design Group, National Institute for Advanced Interdisciplinary Research, Tsukuba,

Pages: 15    Published: Jan 1996

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Abstract

Alloying elements for titanium alloys were selected from 5–20 mass%Zr, 10–20 mass% Sn, 4–8 mass% Nb, 2–4 mass% Ta and 0–0.5mass% Pd instead of using Al and V.

The room temperature tensile strength of the alloys markedly increase with increasing Sn content as compared with increasing Zr content. As a result, the Ti-15%Sn-4%Nb-2 %Ta -0.2%Pd alloy surpassed the Ti-6%Al-4%V extra low interstitial alloy for medical implants (ASTM F136-84 standard) in tensile strength as well as in elongation and reduction of area. Tensile strength was further improved by the additions of nitrogen and oxygen.

The effect of alloying elements on the corrosion resistance of titanium alloy for medical implants was also investigated by immersion tests in an aerated 5 wt. % HCl solution for 864 ks at 310 K and anodic polarization measurements in a phosphate buffer solution containing chloride ion (PBS(-)) and 5% HCl solution. The concentration of released Ti in 5 % HCl solution decreased with increasing Zr, Ta and Pd contents in the range from 10 to 15%, 2 to 4% and 0 to 0.2% respectively, although Nb and Sn had adverse effect in the range from 4 to 8% and 10 to 20%, respectively. The critical current density for passivation ( Ic ) of the titanium alloys in PBS(-) decreased with increasing Zr, Nb, Ta and Pd contents. The I c values in the PBS(-) decreased as those in the 5 % HCl solution decreased.