title: Fabrication of a high-performance hip prosthetic stem using β Ti-33.6Nb-4Sn.
abstract: This study used severe cold rolling followed by cold swaging of β Ti-33.6% Nb-4% Sn rods to form a characteristic fiber structure composed of stress-induced α″ martensite with <010> texture and a β phase with <101> texture, resulting in a material with a low Young's modulus of 40GPa. The material's tensile strength of 1270MPa and fatigue strength of 850MPa were attained by heat treatment at 673K for 5h through fine α precipitation in the fiber structure. A new method of fabricating a high-performance hip prosthetic stem was investigated based on the low Young's modulus and high strength obtained. After fabricating the stem by cold rolling, cold swaging, cold die-forging and machining, its neck region was given higher strength through local heat treatment, while the low Young's modulus remained almost unchanged in a distal portion of the stem. When a stem tip in the distal part was heat treated at 423K, reverse α″→β transformation occurred and the tangent modulus decreased to less than 30GPa, accompanied by stress-induced β→α″. It was concluded that the method presented herein provided a low Young's modulus of approximately 40GPa in the distal part and high fatigue strength of approximately 850MPa in the neck region of a high-performance hip prosthetic stem.
authors.affiliation: Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan. Electronic address: hanada@imr.tohoku.ac.jp.
authors.forename: Shuji
authors.initials: S
authors.lastname: Hanada
authors.affiliation: Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Naoya
authors.initials: N
authors.lastname: Masahashi
authors.affiliation: Korea Institute of Industrial Technology, Incheon 406-840, Republic of Korea.
authors.forename: Taek-Kyun
authors.initials: TK
authors.lastname: Jung
authors.affiliation: Tohoku University School of Medicine, Sendai 980-8574, Japan.
authors.forename: Norikazu
authors.initials: N
authors.lastname: Yamada
authors.affiliation: Organization for Promotion of Tenure Track, University of Miyazaki, Miyazaki 889-2192, Japan.
authors.forename: Go
authors.initials: G
authors.lastname: Yamako
authors.affiliation: Tohoku University School of Medicine, Sendai 980-8574, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Itoi
mesh_terms: D055119:Elastic Modulus; D006622:Hip Prosthesis; D006358:Hot Temperature; D008422:Materials Testing; D009556:Niobium / Q000737:chemistry*; D013718:Tensile Strength; D014001:Tin / Q000737:chemistry*; D014025:Titanium / Q000737:chemistry*
chemical_list: D009556:Niobium; D014001:Tin; D014025:Titanium