Deformation-induced changeable Youngʹs modulus with high strength in β-type Ti–Cr–O alloys for spinal fixture

In order to meet the requirements of the patients and surgeons simultaneously for spinal fixation applications, a novel biomedical alloy with a changeable Youngʹs modulus, that is, with a low Youngʹs modulus to prevent the stress-shielding effect for patients and a high Youngʹs modulus to suppress springback for surgeons, was developed. In this study, the chromium and oxygen contents in ternary Ti(11, 12 mass%)Cr–(0.2, 0.4, 0.6 mass%)O alloys were optimized in order to achieve a changeable Youngʹs modulus via deformation-induced ω-phase transformation with good mechanical properties. ungʹs moduli of all the examined alloys increase after cold rolling, which is attributed to the deformation-induced ω-phase transformation. This transformation is suppressed by oxygen but enhanced with lower chromium content, which is related to the β(bcc)-lattice stability. Among the examined alloys, the Ti–11Cr–0.2O alloy shows a low Youngʹs modulus of less than 80 GPa in the solution-treated (ST) condition and a high Youngʹs modulus of more than 90 GPa in the cold rolled (CR) condition. The Ti–11Cr–0.2O alloy also exhibits a high tensile strength, above 1000 MPa, with an acceptable elongation of ~12% in the ST condition. Furthermore, the Ti–11Cr–0.2O alloy exhibits minimal springback. This value of springback is the closest to that of Ti64 ELI alloy among the compared alloys. Therefore, the Ti–11Cr–0.2O alloy, which has a good balance between large changeable Youngʹs modulus, high tensile strength, good plasticity, and minimal springback, is considered to be a potential candidate for spinal fixation applications.