Ti-5Mo-3Sn合金の機械的性質と形状記憶特性に及ぼすZr添加の影響

摘要

The effects of Zr addition on the mechanical, shape memory and superelastic properties of Ti-5Mo-3Sn (mol%) based alloys were investigated with Zr content up to 24 mol%. The parent bcc phase was stabilized with increasing Zr content, and the volume fraction of the ω phase seemed independent of the Zr content. The ultimate tensile strength and fracture strain increased with increasing Zr content up to 6 mol%Zr, however, the alloy became brittle with further addition of Zr content over 8 mol%. Young's modulus was low around 37〜38 GPa when Zr content was 2〜6 mol%. Shape memory effect was confirmed when Zr content was less than 5 mol%, and the superelasticity appeared in 6 mol%Zr-added alloy with the good shape recovery strain of 4.3%. When the Zr addition exceeded 6 mol%, the slip deformation occurred. The slip stress was raised by Zr addition with a rate of 9.5 MPa/ mol%Zr in the alloys containing 2〜6mol%Zr. It is concluded for Ti-5Mo-3Sn based alloys that Zr addition is effective to improve the mechanical properties without degradation of lattice transformation strain, and that good room-temperature superelasticity appears in the Ti-5Mo-3Sn-6Zr alloy.%Ti基合金は，その良好な生体適合性や，形状記憶·超弾性特性といったユニークな性質を持つことから生体用材料として幅広く使用されている.現在，主に実用化されているのはTi-Ni合金であるが，その構成元素の半分がNiであるため，Niアレルギーの危険性が指摘されている.したがって，近年，生体適合元素から構成され，良好な加工性，低弾性率を持つβ-Ti基形状記憶合金の開発が積極的に行われている.