MITSUO NINOMI - Institute for Materials Research, Tohoku University, ۲-۱-۱, Katahira, Aoba-ku, City, Miyagi ۹۸۰-۸۵۷۷, Japan
MASA AKINAKAI - Institute for Materials Research, Tohoku University, ۲-۱-۱, Katahira, Aoba-ku, Sendai, Miyagi ۹۸۰-۸۵۷۷, Japan
JUNKO HIEDA - Institute for Materials Research, Tohoku University, ۲-۱-۱, Katahira, Aoba-ku, Sendai, Miyagi ۹۸۰-۸۵۷۷, Japan
KENGO) NARITA - Graduate Student, Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai ۹۸۰-۸۵۷۹, Japan

Solutionized Ti-29Nb-13Ta-4.6Zr, which is referred to as TNTZ, has a low Young s modulus of approximately 60 GPa. This value is much smaller than the corresponding Young s moduli of Co-Cr alloys and stainless steel (SUS 31.6L), which are approximately 210 GPa and 200 GPa, respectively. A low Young s modulus has been proved to be effective in inhibiting stress shielding. TNTZ is expected to be used for developing spinal rods. The fatigue strength and Young s modulus are the most important mechanical biocompatibility that determines the mechanical biocompatibility. In particular, bending fatigue strength is important for spinal rods. The mechanical biocompatibilities such as un-iaxial fatigue strength, bending fatigue strength, and balance of strength and ductility of TNTZ can be improved by heat treatment or thermomechanical treatments, which control the microstructure of TNTZ. Therefore, the effects of thermomechanical treatments on mechanical biocompatibilities of TNTZ rods are discussed in this paper.

B-type titanium alloy, Young s modulus; Mechanical biocompatibility; Spine rod; Thermomechanical treatment