Microstructures and mechanical properties of metastable Ti–30Zr–(Cr, Mo) alloys with changeable Young’s modulus for spinal fixation applications

In order to develop a novel alloy with a changeable Young’s modulus for spinal fixation applications, we investigated the microstructures, Young’s moduli, and tensile properties of metastable Ti–30Zr–(Cr, Mo) alloys subjected to solution treatment (ST) and cold rolling (CR). All the alloys comprise a β phase and small athermal ω phase, and they exhibit low Young’s moduli after ST. During CR, deformation-induced phase transformation occurs in all the alloys. The change in Young’s modulus after CR is highly dependent on the type of deformation-induced phase. The increase in Young’s modulus after CR is attributed to the deformation-induced ω phase on {3 3 2} mechanical twinning. Ti–30Zr–3Cr–3Mo (3Cr3Mo), which exhibits excellent tensile properties and a changeable Young’s modulus, shows a smaller springback than Ti–29Nb–13Ta–4.6Zr, a β-type titanium alloy expected to be useful in spinal fixation applications. Thus, 3Cr3Mo is a potential candidate for spinal fixation applications.