title: Development of thermo-mechanical processing for fabricating highly durable β-type Ti-Nb-Ta-Zr rod for use in spinal fixation devices.
abstract: The mechanical strength of a beta titanium alloy such as Ti-Nb-Ta-Zr alloy (TNTZ) can be improved significantly by thermo-mechanical treatment. In this study, TNTZ was subjected to solution treatment, cold caliber rolling, and cold swaging before aging treatment to form a rod for spinal fixation. The {110}(β) are aligned parallel to the cross-section with two strong peaks approximately 180° apart, facing one another, in the TNTZ rods subjected to cold caliber rolling and six strong peaks at approximately 60° intervals, facing one another, in the TNTZ rods subjected to cold swaging. Therefore, the TNTZ rods subjected to cold swaging have a more uniform structure than those subjected to cold caliber rolling. The orientation relationship between the α and β phases is different. A [110](β)//[121](α), (112)(β)//(210)(α) orientation relationship is observed in the TNTZ rods subjected to aging treatment at 723 K after solution treatment and cold caliber rolling. On the other hand, a [110](β)//[001](α), (112)(β)//(200)(α) orientation relationship is observed in TNTZ rod subjected to aging treatment at 723 K after cold swaging. A high 0.2% proof stress of about 1200 MPa, high elongation of 18%, and high fatigue strength of 950 MPa indicate that aging treatment at 723 K after cold swaging is the optimal thermo-mechanical process for a TNTZ rod.
authors.affiliation: Tohoku University, 6-6 Aramaki Aza, Sendai, 980-8579, Japan.
authors.forename: Kengo
authors.initials: K
authors.lastname: Narita
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: Kazuya
authors.initials: K
authors.lastname: Oribe
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D003080:Cold Temperature; D004867:Equipment Design; D006358:Hot Temperature; D006801:Humans; D016268:Internal Fixators; D008855:Microscopy, Electron, Scanning / Q000379:methods; D009556:Niobium / Q000737:chemistry*; D055095:Optics and Photonics; D019736:Prostheses and Implants; D011475:Prosthesis Failure; D012996:Solutions; D013131:Spine / Q000473:pathology*; D013314:Stress, Mechanical; D013499:Surface Properties; D013635:Tantalum / Q000737:chemistry*; D013718:Tensile Strength; D014025:Titanium / Q000737:chemistry*; D014961:X-Ray Diffraction; D015040:Zirconium / Q000737:chemistry*
chemical_list: D001672:Biocompatible Materials; D012996:Solutions; C023988:beta titanium; D009556:Niobium; D013635:Tantalum; D015040:Zirconium; D014025:Titanium