Fabrication of a high-performance hip prosthetic stem using β Ti–33.6Nb–4Sn

• Published in: Journal of the mechanical behavior of biomedical materials Vol. 30; pp. 140 - 149
• Main Authors: Hanada, Shuji, Masahashi, Naoya, Jung, Taek-Kyun, Yamada, Norikazu, Yamako, Go, Itoi, Eiji
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 01.02.2014
• Subjects: Cold rolling; Elastic Modulus; Heat treatment; Hip Prosthesis; Hot Temperature; Materials Testing; Modulus of elasticity; Niobium - chemistry; Prosthetics; Surface layer; Surgical implants; Swaging; Tensile Strength; Texture; Tin - chemistry; Titanium - chemistry
• ISSN: 1751-6161; 1878-0180
• DOI: 10.1016/j.jmbbm.2013.11.002

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.