Multifunctional Beta Ti Alloy with Improved Specific Strength

Abstract

Gum metals feature properties such as ultrahigh strength, ultralow elastic modulus, superelasticity, and superplasticity. They are composed of elements from Groups 4 and 5 of the periodic table and exist when the valance electron concentration ( \(\overline{e/a}\) ) is 4.24; the bond order ( \(\overline{\text{Bo}}\) ) is 2.87; and the "d" electron-orbital energy level ( \(\overline{\text{Md}}\) ) is 2.45 eV. Typical compositions include Ti–23Nb–2Zr–0.7Ta–O and Ti–12Ta–9Nb–6Zr–3 V–O, which contain large amounts of heavy Group-5 elements such as Nb and Ta. In the present study, to improve the specific strength of a multifunctional beta Ti alloy, three alloys (Ti–20Nb–5Zr–1Fe–O, Ti–12Zr–10Mo–4Nb–O, and Ti–24Zr–9Cr–3Mo–O) were designed by satisfying the above three requirements while adding Fe, Mo, and Cr, which are not only lightweight but also have strong hardening effects. Microstructural and mechanical property analyses revealed that Ti–20Nb–5Zr–1Fe–O has a 25% higher specific strength than gum metal while maintaining an ultralow elastic modulus.

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