Nohira Naoki, Hayashi Kenta, Tahara Masaki, Hosoda Hideki
Institute of Innovative Research (IIR), Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan.
Institute of Innovative Research (IIR), Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan.
J Mech Behav Biomed Mater. 2023 May;141:105800. doi: 10.1016/j.jmbbm.2023.105800. Epub 2023 Mar 24.
For the further development of biocompatible metastable β (bcc) Ti alloys, the purpose of this study is to evaluate the potential of bismuth (Bi) addition in terms of shape memory properties and phase stability. It was found that the shape memory effect appeared in Ti-5Cr-1.6Bi (mol%) alloy. However, permanent (unrecoverable) deformation due to dislocations or twinning was also introduced simultaneously from the early stage of deformation. Regarding the formation of isothermal ω phase and the resulting hardness change by aging, it was found that the hardness change was large and that the isothermal ω phase formed in Ti-5Cr-1.6Bi alloy, while age hardening was small and no isothermal ω phase formed in Ti-5Cr-6.1Bi alloy. These results indicate the suppression of not only athermal ω but also isothermal ω phase by Bi addition. However, considering the fact that the alloy becomes brittle when Bi addition is over 3 mol%, it can be concluded that 1-3 mol% Bi addition is worth for the improvement of shape memory effect, suppression of ω phase, X-ray imaging, magnetic resonance imaging, and biocompatibility in metastable β Ti alloys.
为了进一步开发具有生物相容性的亚稳β（体心立方）钛合金，本研究的目的是评估添加铋（Bi）在形状记忆性能和相稳定性方面的潜力。研究发现，Ti-5Cr-1.6Bi（摩尔%）合金出现了形状记忆效应。然而，从变形早期开始，由于位错或孪晶导致的永久（不可恢复）变形也同时出现。关于等温ω相的形成以及时效导致的硬度变化，研究发现Ti-5Cr-1.6Bi合金的硬度变化很大且形成了等温ω相，而Ti-5Cr-6.1Bi合金的时效硬化较小且未形成等温ω相。这些结果表明，添加Bi不仅抑制了非热ω相，还抑制了等温ω相。然而，考虑到当Bi添加量超过3摩尔%时合金会变脆这一事实，可以得出结论，添加1-3摩尔%的Bi对于改善亚稳β钛合金的形状记忆效应、抑制ω相、X射线成像、磁共振成像和生物相容性是值得的。
