JP2005105388A - Method of producing superelastic titanium alloy for living body, and titanium alloy for superelasticity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a superelastic titanium alloy for the living body not inferior in a strain amount showing superelasticity compared with that of a Ti-Ni alloy, and having narrow stress hysteresis. <P>SOLUTION: In the method of producing a superelastic titanium alloy for the living body, an ingot having components as a Ti alloy obtained by incorporating Mo and either one element selected from Al, Ge and Ga into Ti, and the balance inevitable impurities is prepared, and the ingot is subjected to hot working and cold working, is annealed successively to the cold working, is thereafter subjected to final cold working at a working ratio of ≥20%, and is then subjected to heating treatment at ≥450°C. Further, by the method, the superelastic titanium alloy for the living body in which residual strain after 2% tension is ≤0.20%, and stress hysteresis in 1% after the 2% tension is ≤150 MPa can be obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a bioelastic superelastic titanium alloy and a titanium alloy produced by the method.

  In recent years, alloy materials with superelasticity have been used in the medical field. For example, Ti—Ni-based alloys have characteristics such as strength, high wear resistance, excellent corrosion resistance, and good compatibility with living organisms. It is used in a wide variety of fields.

  By the way, biomaterials using Ti—Ni alloys are concerned about the elution of Ni elements that are thought to be involved in allergic symptoms. Ti-Ni alloy, which is the main constituent element of Ni, is anxious from the aspect of allergic symptoms, so it does not contain elements that are toxic or allergenic to the human body, and is safer and more elastic There is a growing demand for alloys.

  FIG. 4 summarizes the results for various pure metal elements, with the horizontal axis representing the cell growth coefficient of chicken embryo myocardial fibroblast tissue and the vertical axis representing the relative cell growth rate of L929 cells derived from mouse fibromyal tissue (Source: : Materials Science and Engineering A, A243 (1998) 244-249). According to this figure, V, Cu, Zn, Cd, Co, Hg and the like are elements having strong cytotoxicity, and Zr, Ti, Ta, Pd, Au and the like are excellent in biocompatibility. Has been.

  Furthermore, FIG. 5 shows the results (source: same as FIG. 4) in which the horizontal axis is biocompatible and the vertical axis is polarization resistance (R / Ω · m) which is an index of in vivo corrosion resistance. . This figure shows that Pt, Ta, Nb, Ti, and Zr are excellent in biocompatibility.

  Based on the above, Japanese Patent Laid-Open No. 2001-329325 focuses on a Ti—Nb alloy composed of an element excellent in biocompatibility, and adds ternary Sn as a third element that does not indicate toxicity. It has been proposed that a system alloy can be utilized as a shape memory alloy for living organisms.

  In addition, in the Japanese Patent Application No. 2002-102531, the present inventors have disclosed a Ti—Mo—Al-based alloy composed of Mo and any one of Al, Ge, and Ga, which has no indication of toxicity. Mo-Ge alloys and Ti-Mo-Ga alloys were proposed as superelastic alloys.

Such a bioelastic super-titanium material can be used for medical devices such as medical guidewires, orthodontic wires, and stents, and can also be used for spectacle frames.
JP 2001-329325 A Daisuke Kuroda, 4 others, Materials Science and Engineering A, Elsevier Science, March 15, 1998, 243, P.244-249 Edited by Yasuyuki Funakubo, “Shape Memory Alloy”, First Edition, Sangyo Tosho Co., Ltd., June 7, 1984, P36

  In the above-mentioned Japanese Patent Application Laid-Open No. 2001-329325 and Japanese Patent Application No. 2002-102531, a titanium alloy is subjected to solution heat treatment to reduce residual strain after deformation with a certain component composition, that is, to obtain superelasticity. is there.

  However, the above-described superelasticity has a small amount of strain exhibiting superelasticity compared to a Ti—Ni alloy, and is insufficient for use in a medical device for a living body. This was thought to be due to the fact that since the solution heat treatment was performed, the critical stress for the slip was lowered, and the permanent deformation due to the slip occurred before the full superelasticity was developed.

  Also, if the stress hysteresis (the difference in stress between loading and unloading) is large, the rotation at hand is difficult to be transmitted to the wire tip when used for a medical guide wire, and the maneuverability is poor (torque transmission is poor). Problems arise.

  Therefore, the present invention provides a method for producing a bioelastic elastic titanium alloy for living organisms and a bioelastic elastic titanium alloy with a low stress hysteresis, which is not inferior in strain to superelasticity compared to a Ti—Ni alloy exhibiting excellent superelasticity. It is to provide.

A first aspect of the present invention for solving the above problems is an ingot comprising a titanium alloy containing Ti and Mo and any one of Al, Ge, and Ga, the balance being inevitable impurities. Prepare
Subject the ingot to hot working and cold working;
After annealing following the cold working, the final cold working with a working rate of 20% or more is performed,
Next, it is a method for producing a superelastic titanium alloy for living body, wherein the heat treatment is performed at a temperature of 450 ° C. or higher.

  According to a second aspect of the present invention, the titanium alloy has a component composition of Mo of 2 to 12 at%, Al of 3 to 14 at%, Ge of 8 at% or less, and Ga of 14 at% or less. It is a manufacturing method of a super elastic titanium alloy.

  A third aspect of the present invention is a method for producing a bioelastic superelastic titanium alloy, wherein the heating time of the heat treatment is 1 minute to 2 hours.

  According to a fourth aspect of the present invention, any one of 2-12 at% Mo, 3-14 at% Al, 8 at% or less Ge, 14 at% or less Ga, and the balance is Ti and inevitable impurities. A bioelastic super-titanium alloy, wherein the residual strain after 2% tension is 0.2% or less.

  According to a fifth aspect of the present invention, any one of 2 to 12 at% Mo, 3 to 14 at% Al, 8 at% or less Ge, 14 at% or less Ga and the balance is Ti and inevitable impurities. A bioelastic supertitanium alloy having a stress hysteresis at 1% after 2% tension of 150 MPa or less.

  According to a sixth aspect of the present invention, any one of 2-12 at% Mo, 3-14 at% Al, 8 at% Ge or less, 14 at% Ga or less, and the balance is Ti and inevitable impurities. A living body superelastic titanium alloy, wherein the residual strain after 2% tension is 0.2% or less, and the stress hysteresis at 1% after 2% tension is 150 MPa or less It is a super elastic titanium alloy.

  Appropriate heat treatment for Ti-Mo-Al alloy, Ti-Mo-Ga alloy, Ti-Mo-Ge alloy with excellent biocompatibility to develop good superelastic properties I was able to.

Embodiments of the present invention will be described below. First, the superelasticity will be briefly described. FIG. 6 (source: shape memory alloy, edited by Yasuyuki Funakubo, page 36) is a schematic diagram showing the conditions for the development of superelasticity. FIG. 6 shows that if the critical stress for slip is high as shown in (A), superelasticity appears in the stress-temperature range with a hatched line, and if the critical stress for slip is low as shown in (B), the superelasticity is It shows that it does not express. Also, FIG. 6, superelastic have shown that expression in the temperature range of M _d from A _f.

Here, M _s is a temperature at which transformation from austenite to martensite starts, and M _f denotes a temperature at which transformation from austenite to martensite ends. A _s is the austenite transformation start temperature, A _f is an austenite transformation finish temperature. M _d is the maximum temperature at which stress-induced martensite is generated.

Since the biomaterial is used in the body or in a state of being in close contact with the body, it can be said that the operating temperature range is near room temperature. Therefore, in order to obtain superelasticity, it is necessary to control _Af to be room temperature or lower and _Md to be room temperature or higher. In general, _Af largely depends on the component composition and is difficult to change due to factors other than the component composition. Therefore, it is desirable to control _Af by changing the component composition.

M _d increases due to an increase in critical stress against slip, and good superelasticity is obtained as M _d increases. In other words, in order to obtain good superelasticity, it is necessary to increase the critical stress for slipping.

  As a method for increasing the critical stress for slipping, there is a method for forming a processed structure in which slip deformation hardly occurs. Even in Ti-Mo-Al-based alloys, Ti-Mo-Ge-based alloys, and Ti-Mo-Ga-based alloys, the critical stress is increased by forming a textured structure by cold working and making it difficult for dislocations to move. I thought it was possible.

  Here, the Ti alloy of the present invention is a β-stable Ti alloy. There is a ω phase as a fine precipitation phase of a β stable Ti alloy. However, precipitation of the ω phase may lead to embrittlement. For this reason, it is necessary to suppress the precipitation of the ω phase as much as possible in order to prevent embrittlement during the heat treatment for imparting superelasticity.

  In the present invention, an ingot comprising a Ti alloy containing Ti and Mo and any one of Al, Ge, and Ga, the balance being made of inevitable impurities is prepared, and the ingot is subjected to hot working and After performing cold working and annealing subsequent to the cold working, a final cold working with a processing rate of 20% or more is performed, and then heat treatment is performed at a temperature of 450 ° C. or higher to produce superelastic titanium for living organisms. Manufacture alloys.

  In the present invention, an ingot of Ti alloy containing Mo and any one of Al, Ge, and Ga is used. Here, the titanium alloy desirably has Mo of 2 to 12 at%, Al of 3 to 14 at%, Ge of 8 at% or less, and Ga of 14 at% or less. By setting it as this component composition and composition range, a suitable bioelastic titanium alloy can be obtained.

  In the present invention, the final cold working rate after annealing is set to 20% or more. This is because the processed structure is less prone to slip deformation, and if it is less than 20%, the desired processed structure cannot be obtained.

  In the present invention, the temperature for the heat treatment is set to 450 ° C. or higher. The reason is that if a heat treatment is performed at a temperature lower than 450 ° C., for example, 400 ° C. for 6 hours, the ω phase precipitates and becomes brittle, and good superelasticity cannot be obtained. A desirable temperature range is 450-700 ° C. However, an excellent superelasticity can be obtained if the heat treatment is performed for a short time of about 15 seconds at 800 ° C. so that the processed structure is not recrystallized even if it exceeds 700 ° C., but at a high temperature such as 800 ° C. It is difficult to stably perform a short-time heat treatment for both the treatment temperature and time. Therefore, it is desirable that the heat treatment time be in the range of 1 minute to 2 hours for the above reason.

  The bioelastic superelastic titanium alloy of the present invention has a residual strain after 2% tension of 0.20% or less. The reason is that if it exceeds 0.20%, the residual strain is large and it is difficult to use it for a medical device for living body. The tensile test was conducted according to JISH7103.

  The bioelastic super-titanium alloy of the present invention has a stress hysteresis at 1% after 2% tension of 150 MPa or less. The reason is that when used for a medical guide wire, the smaller the stress hysteresis, the better the torque transmission, and in the conventional manufacturing method, the stress hysteresis exceeds 150 MPa. The tensile test was conducted according to JISH7103.

  Melt using a non-consumable tungsten electrode type argon arc melting furnace and cast into the required shape so that Mo: 6 at%, Al: 7 at%, the remainder being Ti and Ti—Mo—Al alloy which is an inevitable impurity Thus, an ingot was produced. The ingot was hot-worked and cold-worked. After the annealing during the cold working, the final cold working was performed at a working rate of 60% to obtain a finished wire with a diameter of 0.4 mm.

  The processed wire was heat-treated every 50 ° C. within a temperature range of 400 to 750 ° C. The heat treatment time was 30 minutes. When the heat treatment temperature was 600 ° C., the heat treatment time was 2 minutes and 5 minutes. For comparison, the processed wire was subjected to a solution treatment at 950 ° C. for 30 minutes.

  This alloy wire was subjected to a tensile test at room temperature. The results are shown in Table 1 as FIG. 1 together with the residual strain after 2% tension and the stress hysteresis.

  The comparative example A-1 became brittle because the heat treatment temperature was as low as 400 ° C., and it was broken when the strain was about 1%. A-2 to A-9, which are examples of the present invention, have small residual strain and stress hysteresis compared to A-11 of the comparative example in which solution treatment was performed at 950 ° C. for 30 minutes. A-10 had a heat treatment temperature as high as 750 ° C. and recrystallized, so that the residual strain was as high as 0.29%.

  A Ti—Mo—Ga alloy having Mo: 5 at%, Ga: 5 at%, the remainder being Ti and inevitable impurities was prepared and manufactured in the same manner as in Example 1 to manufacture a finished wire having a diameter of 0.4 mm. The processed wire was heat-treated every 50 ° C. in the temperature range of 400 to 750 ° C. The heat treatment time was 30 minutes. When the heat treatment temperature was 600 ° C., the heat treatment time was 2 minutes and 5 minutes. For comparison, the processed wire was subjected to a solution treatment at 950 ° C. for 30 minutes.

  This alloy wire was subjected to a tensile test at room temperature. The results are shown in Table 2 as FIG. 2 together with the residual strain after 2% tension and the stress hysteresis.

  B-1 of the comparative example became brittle because the heat treatment temperature was as low as 400 ° C., and fractured when the strain was about 1%. B-2 to B-9, which are examples of the present invention, have small residual strain and stress hysteresis compared to B-11 of the comparative example in which solution treatment was performed at 950 ° C. for 30 minutes. B-10 had a heat treatment temperature as high as 750 ° C. and recrystallized, so that the residual strain was as high as 0.35%.

  A Ti—Mo—Ge alloy having Mo: 6 at%, Ge: 4 at%, the remainder being Ti and inevitable impurities was prepared, and a processed wire having a diameter of 0.4 mm was manufactured by the same manufacturing method as in Example 1. . The processed wire was heat-treated every 50 ° C. in the temperature range of 400 to 750 ° C. The heat treatment time was 30 minutes. When the heat treatment temperature was 600 ° C., the heat treatment time was 2 minutes and 5 minutes. For comparison, the processed wire was subjected to a solution treatment at 950 ° C. for 30 minutes.

  This alloy wire was subjected to a tensile test at room temperature. The results are shown in Table 3 as FIG. 3 together with the residual strain after 2% tension and the stress hysteresis.

  C-1 of the comparative example became brittle because the heat treatment temperature was as low as 400 ° C., and fractured when the strain was about 1%. C-2 to C-9, which are examples of the present invention, have small residual strain and stress hysteresis compared to C-11 of a comparative example in which solution treatment was performed at 950 ° C. for 30 minutes. C-10 had a heat treatment temperature as high as 750 ° C., and recrystallization showed a residual strain as high as 0.25%.

  Excellent superelastic properties can be expressed by applying an appropriate heat treatment to Ti-Mo-Al, Ti-Mo-Ge, Ti-Mo-Ga alloys, which are excellent in biocompatibility, Not only the wire material but also a plate material, strip material, tape material, pipe material, deformed wire material, and any other forms that can be cold worked are applicable.

It is Table 1 shown as FIG. 1, and is an evaluation result of a Ti—Mo—Al based alloy. It is Table 2 shown as FIG. 2, and is an evaluation result of a Ti-Mo-Ga type alloy. It is Table 3 shown as FIG. 3, and is an evaluation result of the Ti—Mo—Ge alloy. It is the figure which showed the cytotoxicity of the pure metal. It is the figure which showed the correlation of biocompatibility, such as polarization resistance and a pure metal. It is a schematic diagram which shows the appearance situation of super elasticity.

Claims (6)

An ingot is prepared which is composed of Ti alloy containing Ti and any one of Al, Ge, and Ga, or Ti alloy containing Nb and Sn in Ti, with the balance being inevitable impurities. And
Subject the ingot to hot working and cold working;
After annealing following the cold working, the final cold working with a working rate of 20% or more is performed,
Then, the manufacturing method of the superelastic titanium alloy for living bodies characterized by heat-processing at the temperature of 450 degreeC or more.   The titanium alloy has a component composition of Mo 2-12 at%, Al 3-14 at%, Ge 8 at% or less, Ga 14 at% or less, Nb 10-20 at%, Sn 3-6 at%. The manufacturing method of the superelastic titanium alloy for living bodies of Claim 1 characterized by the above-mentioned.   The method for producing a bioelastic superelastic titanium alloy according to claim 1 or 2, wherein the heating time of the heat treatment is 1 minute to 2 hours.   A titanium alloy produced by the method according to claim 1, wherein the residual strain after 2% tension is 0.2% or less.   A titanium alloy produced by the method according to claim 1, wherein the stress hysteresis at 1% after 2% tension is 150 MPa or less. The titanium alloy manufactured by the method according to claim 1, wherein the residual strain after 2% tension is 0.2% or less, and the stress hysteresis at 1% after 2% tension is 150 MPa or less. A superelastic titanium alloy for living body.

Images