Titanium alloys for medical implants were cast using 5∼20 mass%Zr, 10∼20%Sn, 4∼8%Nb, 2∼4%Ta and 0∼0.2%Pd as alloying elements instead of using harmful Al and V.
The alloys were forged in their α and α+β regions and then annealed at 973 K for 7.2 ks. The annealed microstructures of the alloys consisted mainly of the acicular structure containing 10 to 30 volume% elongated β grains.
While the room temperature tensile strength of the Ti-(5∼15%)Zr-4%Nb-2%Ta-0.2%Pd alloys increased slightly with increasing Zr content, the strength of the Ti-(10∼20%)Sn-4%Nb-2%Ta-0.2%Pd alloys increased markedly with increasing Sn content. The Ti-15%Sn-4%Nb-2%Ta-0.2%Pd alloy surpassed the Ti-6%Al-4%V extra low interstitial (ELI) alloy for medical implants (ASTM F136-84 Standard) in tensile strength as well as in elongation and reduction of area. The tensile strength was further improved by the additions of nitrogen and oxygen.