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

Abstract

In order to meet the requirements of the patients and surgeons simultaneously for spinal fixation applications, a novel biomedical alloy with a changeable Young's modulus, that is, with a low Young's modulus to prevent the stress-shielding effect for patients and a high Young's modulus to suppress springback for surgeons, was developed. In this study, the chromium and oxygen contents in ternary Ti(11, 12mass%)Cr–(0.2, 0.4, 0.6mass%)O alloys were optimized in order to achieve a changeable Young's modulus via deformation-induced ω-phase transformation with good mechanical properties.The Young's 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 Young's modulus of less than 80GPa in the solution-treated (ST) condition and a high Young's modulus of more than 90GPa in the cold rolled (CR) condition. The Ti–11Cr–0.2O alloy also exhibits a high tensile strength, above 1000MPa, 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 Young's modulus, high tensile strength, good plasticity, and minimal springback, is considered to be a potential candidate for spinal fixation applications.