Metastable dual-phase Ti–Nb–Sn–Zr and Ti–Nb–Sn–Fe alloys with high strength-to-modulus ratio

Abstract

Conventional dual-phase titanium (Ti) alloy exhibits high strength and toughness, but the high elastic modulus makes it unsuitable for biomedical implants. In this study, two novel metastable dual-phase (α"+β) Ti–Nb–Sn–(Zr/Fe) systems have been developed using [Mo]eq theory. The dual-phase α"+β structure contributed to the alloys’ characteristics of high strength and low elastic modulus. The bending strengths of Ti–(16−22)Nb–8Sn–(5−8)Zr and Ti–(17−19)Nb–8Sn–(0.5–1.5)Fe alloys (1023–1190 MPa and 960–1308 MPa, respectively) were obviously higher than that of Ti–25 Nb–8Sn (962 MPa). Among them, both Ti–18Nb–8Sn–7Zr and Ti–19Nb–8Sn–0.5Fe with dual phase had lower elastic moduli (50.4 and 50.5 GPa, respectively) than Ti–25Nb–8Sn (52 GPa), which can avoid the stress shielding effect after implantation. Ti–18Nb–8Sn–7Zr and Ti–19Nb–8Sn–0.5Fe alloys exhibited greater bending strength-to-modulus ratios (20.3 and 19.0, respectively) than those of c.p. Ti (7.1) and Ti–25Nb–8Sn (18.5). Both dual-phase Ti–18Nb–8Sn–7Zr and Ti–19Nb–8Sn–0.5Fe with low elastic moduli and high strength-to-modulus ratios are promising candidates for bio-implant applications.