M. Niinomi, T. Akahori, M. Nakai, Tohoku University, Sendai, Japan; N. Kawakita, Toyohashi University of Technology, Toyohashi, Japan
TNTZ (Ti-29Nb-13Ta-4.6Zr) shows superelastic behavior, which is an advantageous character for applying TNTZ to stents, guide wires of the catheters and orthodontic wires. However, the small change in chemical composition is considered to change the superelastic behavior of TNTZ. Therefore, Nb content of TNTZ was changed from 1 to 2 mass% below 30 mass%. The change in the behavior of functionalities such as superelasticity and shape memory effect were investigated by tensile loading-unloading tests, X-ray analysis and DSC analysis. When the Nb content is below approximately 28 mass%, the tensile loading-unloading stress-strain curve exhibits the similar curve obtained when the general shape memory behavior occurs due the deformation induced martensite and its reversion. When the Nb content is from approximately 29 mass% to 30 mass%, the tensile loading-unloading curve exhibits superelastc behavior, which can not be explained by deformation induced martensite and its reversion. The very narrow range of change in the chemical composition of Nb changes the superelastic behavior of TNTZ.
Summary: The very narrow range of change in the chemical composition of Nb changes the superelastic behavior of TNTZ.
