Ti-Nb-Zr Alloy

a superelastic alloy and shape memory technology, applied in the field of shape memory and superelastic alloy, can solve the problems of degrading the low-temperature properties of the human body, the inability to use a member relating to the human body, and the superelasticity and shape memory effect, and achieves low-temperature properties in the practical range and high cold workability.

Inactive Publication Date: 2008-08-14
JAPAN BASIC MATERIAL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0011]The principal elements of this alloy are Ti, Nb and Zr that form a strong and dense oxidation film to provide biocompatibility, so that this alloy can be used as a biomaterial. Moreover, this alloy is a practical material that has high cold workability such as to withstand cold working of 50% or more (if working is divided into several cycles, 95% or more without annealing) by one cycle. Also, since martensitic transformation—reverse martensitic transformation occurs in the temperature range of −50° C. to −20 or −30° C., a sudden decrease in rigidity does not occur at a temperature near 0° C., so that this alloy has low-temperature properties in the practical range.

Problems solved by technology

However, since the Ti—Ni alloy contains Ni as a component, the biocompatibility thereof is poor, so that in particular, it cannot be used for a member relating to the human body.
In addition, the Ti—Ni alloy undergoes martensitic transformation—reverse martensitic transformation at a temperature near room temperature, so that it also has a problem in that when the temperature lowers to −50° C. or lower, it softens suddenly and thus the low-temperature properties thereof are degraded.
However, all of the alloys having been developed so far have problems in that the elongation is low, the superelasticity and shape memory effect is poor, and the availableness as a practical alloy is poor.
Besides, all of the Ni-free shape memory alloys have a drawback in that because of poor cold workability, they are difficult to use as an industrial material.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0033]Three kinds of plates containing 23 wt % Nb, 22 wt % Zr, and 1.6, 1.9 and 2.3 wt % Al, the balance being Ti alloy were prepared. These plates were subjected to solution heat treatment by heating at 800° C., and then were water quenched. The stress-elongation curves of the three kinds of specimens are shown in FIGS. 1 to 3. In all cases, a plastic deformation elongation of 4% was given to the plates, then the load was removed. In the case of FIG. 1 (Al: 1.6 wt %), a residual strain of about 2% was developed, and as a result, a superelastic deformation elongation of 3.8% was exhibited as given in Table 2. In the case of FIG. 2 (Al: 1.9 wt %), a residual strain of about 3% was developed, and as a result, a superelastic deformation elongation of 3.7% was exhibited as given in Table 2. In the case of FIG. 3 (Al: 2.3 wt %), a residual strain of about 4% was developed, and as a result, a superelastic deformation elongation of 3.6% was exhibited as given in Table 2. It is found that t...

example 2

[0034]The stress-elongation curve in the case where a plate (width=2.47 mm, thickness=0.9979 mm) containing 23.2 wt % Nb, 22.1 wt % Zr, and 1.27 wt % Al, the balance being Ti alloy was subjected to solution heat treatment by heating at 800° C., and then was water quenched is shown by a solid line. When a stress of 520 MPa was applied, a plastic elongation of 4% was exhibited, and when the stress was removed, a residual strain of about 0.2% was developed, and superelasticity (superelastic elongation is about 3.8%) was exhibited (FIG. 4).

example 3

[0035]A plate (width=2.47 mm, thickness=1.001 mm) containing 23.2 wt % Nb, 22.1 wt % Zr, and 1.27 wt % Al, the balance being Ti alloy was subjected to solution heat treatment by heating at 800° C. for 30 minutes. The tensile stress (MPa) vs. elongation (%) of this plate was as shown in FIG. 5. When a stress of 699.2 MPa was applied at the first time, an elongation of 4% was exhibited, and when the stress was removed, a residual strain of 0.7% was present. When a stress of about 731.05 MPa was applied again, an elongation of 4.7% was exhibited, and when the stress was removed, a residual strain of 0.72% was developed from the point of load 0 at the first time. The figure reveals that the superelasticity (and shape memory properties) appeared (FIG. 5).

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Abstract

An object of the present invention is to develop a shape memory and superelastic alloy that does not contain nickel, and has superelasticity and shape memory properties even if being subjected to heat treatment in spite of high biocompatibility, moreover having high cold workability. The Ti—Nb—Zr base alloy is comprising an alloy composition consisting of 40 to 60 wt % Ti, 18 to 30 wt % Nb, 18 to 30 wt % Zr, and 0.77 to 3.7 wt % at least one metal additional element selected from Al, Sn, In and Ga. The Ti—Nb—Zr base alloy is a practical alloy in which the principal components form a strong and dense oxidation film to exhibit high biocompatibility, and also the alloy has superelasticity and shape memory properties, high cold workability, and high low-temperature properties.

Description

BACKGROUND OF THE INVENTION[0001]1. Technical Field[0002]The present invention relates to a shape memory and superelastic alloy having high cold workability and moreover having high biocompatibility.[0003]2. Background Art[0004]Shape memory properties mean a phenomenon that although a large residual strain occurs when a load is applied to a metal having a certain particular shape (for example, a coil shape) given at the start to plastically deform the metal by elongating it exceeding the elastic limit and then the load is removed, the metal returns into the original shape (original coil shape) when it is heated, namely, a phenomenon utilizing what is called martensitic transformation—reverse martensitic transformation. The shape memory properties have so far been utilized for turbine-type thermal engines, pipe joints, and brassiere wires, for example.[0005]On the other hand, superelasticity means a phenomenon that when a load is applied to a metal in the same way as described above ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C22C14/00C22F1/04
CPCC22C14/00C22F1/183C22F1/006C22C30/00
Inventor WANG, XIN MININOUE, AKIHISATADA, HIROYUKIARAKAWA, TATSUE
Owner JAPAN BASIC MATERIAL
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