Advances in Development of Titanium Alloys for Spinal Fixation Applications-Titanium Alloys with High Fatigue Strength and Low Springback for Spinal Fixation Applications-

Abstract:

The fatigue strength of the newly developed β-type titanium alloy Ti-29Nb-13Ta-4.6Zr (referred to as TNTZ) is important for its applications in spinal fixation rods. Enhancements in the fatigue strength of TNTZ upon solution treatmnet and thermo-mechanical processing (aging after severe cold-caliber rolling or sever cold-swaging) have been investigated. Aging the rods at 723 K for 259.2 ks after cold-swaging is shown to be the optimal thermo-mechanical processing method for the TNTZ rod , yeilding a high 0.2% proof stress of about 1200 MPa, high elongation of 18%, and high fatigue strength of 950 MPa. High springback is undesirable for application of TNTZ spinal-fixation rods. To reduce springback, a High Youngs modulus is required; on the other hand, a low Youngs modulus is beneficial to reduce bone absorption and obtain good bone remodeling. To achieve a balance between these two factors, TNTZ has been modified by adding Cr to obtain an alloy with a high Youngs modulus at the deformed region and a low Youngs modulus throughout the undeformed region. TNTZ-8Ti-2Cr and TNTZ-16Ti-4Cr are novel alloys whose β phase is more stable than that of TNTZ. Only the β phase is present in these alloys, which exhibit relatively low Youngs moduli of <65 GPa after solution treatment, and higher Youngs moduli after cold rolling, owing to a deformation-induced ω-phase transformation. These modified TNTZ alloys show significantly less springback than the original TNTZ, based on tensile and loadingunloading bending tests.

• Periodical: Key Engineering Materials (Volumes 575-576)
• Pages: 446-452
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.575-576.446
• Online since: September 2013
• Authors: Mitsuo Niinomi, Masaaki Nakai, Junko Hieda, Ken Cho, Kengo Narita
• Keywords: Mechanical Property, Spinal Fixation, TNTZ, Young's Modulus, β-Type Titanium Alloy

References

[1] D. Kuroda, M. Niinomi, M. Morinaga, Y. Kat, T. Yashiro, Mater. Sci. Eng. A, 243(1998)244-249.

[2] M. Niinomi, Biomaterials, 24(2003)2673-2683.

[3] M. Niinomi, T. Hattori,K. Morikawa, T. Kasuga, A. Suzuki, H. Fukui, S. Niwa, Mater. Trans, 43(2002)2970-2977.

DOI: 10.2320/matertrans.43.2970

[4] T. Akahori, M. Niinomi, H. Fukui, M. Ogawa, H. Toda, Mater. Sci. Eng. C, 25(2005)248-254.

[5] J. P. Steib, R. Dumas, D. Mitton, W. Skalli, Spine, 29(2004)193-199.

[6] Y. L. Hao, R. Yang, M. Niinomi, D. Kuroda, Y. L. Zhou, K. Fukunaga, A. Suzuki, Metall. Mater. Trans. A, 34(2003)1007-1012.

[7] M. Nakai, M. Niinomi, X. F. Zhao, X. L. Zhao, Mater. Letters, 65(2011)688-690.

[8] M. Niinomi, T. Akahori, M. Nakai, H. Tsutsumi, Mater. Trans., 50(2009)1704–1712.

[9] X. L. Zhao, M. Niinomi, M. Nakai, M. Goro, T. Furuhara, Acta Biomater. 7(2011)3230–3236.

[10] K. Narita, M. Niinomi, M. Nakai, J. Hieda and K. Oribe, JMBBM, 9(2012)207-216.

[11] A. W. Bowen, A, Scripta Metallurgica, 5(1971)709-715.

[12] Q. Li, M. Niinomi, J. Hieda, M. Nakai, and K. Cho, Acta Biomaterialia, to be published.

[13] M. Niinomi, M, Nakai and J, Hieda, Acta Biomaterialia, 8(2012) 3888-3903.