title: Optimization of Cr content of metastable β-type Ti-Cr alloys with changeable Young's modulus for spinal fixation applications.
abstract: Metallic implant rods used in spinal fixtures should have a Young's modulus that is sufficiently low to prevent stress shielding for the patient and sufficiently high to suppress springback for the surgeon. Therefore, we propose a new concept: novel biomedical titanium alloys with a changeable Young's modulus via deformation-induced ω phase transformation. In this study, the Cr content in the range of 10-14 mass% was optimized to produce deformation-induced ω phase transformation, resulting in a large increase in the Young's modulus of binary Ti-Cr alloys. The springback and cytotoxicity of the optimized alloys were also examined. Ti-(10-12)Cr alloys exhibit an increase in Young's modulus owing to deformation-induced ω phase transformation. In this case, such deformation-induced ω phase transformation occurs along with {332}(β) mechanical twinning, resulting in the maintenance of acceptable ductility with relatively high strength. Among the examined alloys, the lowest Young's modulus and largest increase in Young's modulus are obtained from the Ti-12Cr alloy. This alloy exhibits smaller springback than and comparable cytocompatibility to the biomedical Ti alloy Ti-29Nb-13Ta-4.6Zr.
authors.affiliation: Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai, Japan.
authors.forename: Xingfeng
authors.initials: X
authors.lastname: Zhao
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Niinomi
authors.forename: Masaaki
authors.initials: M
authors.lastname: Nakai
authors.forename: Junko
authors.initials: J
authors.lastname: Hieda
authors.forename: Takuya
authors.initials: T
authors.lastname: Ishimoto
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Nakano
mesh_terms: D016475:3T3 Cells; D000497:Alloys; D000818:Animals; D002470:Cell Survival; D002857:Chromium; D008422:Materials Testing; D051379:Mice; D019736:Prostheses and Implants; D013131:Spine / Q000601:surgery*; D013718:Tensile Strength; D014025:Titanium; D014961:X-Ray Diffraction
chemical_list: D000497:Alloys; D002857:Chromium; D014025:Titanium