Ti alloys have attracted continuing research attention as promising biomaterials due to their superior corrosion resistance and biocompatibility and excellent mechanical properties. Metastable β-type Ti alloys also provide several unique properties such as low Young’s modulus, shape memory effect, and superelasticity. Such unique properties are predominantly attributed to the phase stability and reversible martensitic transformation. In this study, the effects of the Nb and Zr contents on phase constitution, transformation temperature, deformation behavior, and Young’s modulus were investigated. Ti–Nb and Ti–Nb–Zr alloys over a wide composition range, i.e., Ti–(18–40)Nb, Ti–(15–40)Nb–4Zr, Ti–(16–40)Nb–8Zr, Ti–(15–40)Nb–12Zr, Ti–(12–17)Nb–18Zr, were fabricated and their properties were characterized. The phase boundary between the β phase and the α′′ martensite phase was clarified. The lower limit content of Nb to suppress the martensitic transformation and to obtain a single β phase at room temperature decreased with increasing Zr content. The Ti–25Nb, Ti–22Nb–4Zr, Ti–19Nb–8Zr, Ti–17Nb–12Zr and Ti–14Nb–18Zr alloys exhibit the lowest Young’s modulus among Ti–Nb–Zr alloys with Zr content of 0, 4, 8, 12, and 18 at.%, respectively. Particularly, the Ti–14Nb–18Zr alloy exhibits a very low Young’s modulus less than 40 GPa. Correlation among alloy composition, phase stability, and Young’s modulus was discussed.

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Recently, metastable β‐type Ti alloys have attracted attention as promising materials for medical implants due to low Young's modulus and superior biocompatibility. The former is dependent on texture developed during the thermomechanical process. Herein, new Ti–Zr–Nb–Sn–Mo alloys with ultralow Young's modulus and excellent biocompatibility are developed as promising materials for medical implants. The effect of Mo on the microstructure and mechanical properties of the Ti–18Zr–5Nb–3Sn system is investigated. X‐ray diffraction (XRD) and scanning electron microscope (SEM) results reveal that Mo acts as a β‐phase stabilizer. Moreover, mechanical behavior and recrystallization texture show strong composition dependence; the 2.5Mo alloy shows the lowest Young's modulus of 40 GPa. This is due to the formation of a recrystallization texture with strong Goss component of <001>. Corrosion behavior of the 2.5Mo alloy in the cell culture medium is similar to that of the commercially pure titanium (cp‐Ti), suggesting excellent corrosion resistance in the biological environment. Both murine fibroblasts and osteoblastic cells show good growth on the 2.5Mo alloy as the same level of that on the cp‐Ti. Implantation into rat subcutaneous tissue confirms no significant difference in the tissue reaction between the 2.5Mo alloy and the cp‐Ti.