EFFECT OF ALLOYING ELEMENTS ON MECHANICAL-PROPERTIES OF TITANIUM-ALLOYS FOR MEDICAL IMPLANTS

Titanium alloys for medical implants were casted using 5 approximately 20 mass%Zr, 10 approximately 20%Sn, 4 approximately 8%Nb, 2 approximately 4%Ta and 0 approximately 0.2%Pd as alloying elements instead of using harmful Al and V. The alloys were forged in their alpha and alpha + beta regions followed by annealing at 973 K for 7.2 ks. The annealed microstructures of the alloys consisted mainly of the acicular structure containing elongated beta grains in the range from 10 to 30 vol%. The room temperature tensile strength of the alloys markedly increased with increasing Sn content, as compared with increasing than 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. The tensile strength was further improved by the additions of nitrogen and oxygen.