JP2003089834A - Ni-Ti ALLOY WITH HIGH RIGIDITY TYPE REVERSIBLE DEFORMATION - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Ni-Ti alloy having high rigidity type reversible deformation. SOLUTION: The Ni-Ti alloy has a composition consisting of, by atom, 50.4-52.0% Ni and the balance Ti and also has high rigidity type reversible deformation within the range enclosed with straight lines connecting points A (60, 50), B (60, 70), C (-75, 95) and D (-75, 55) in the order in the coordinate plane in which the Af temperature at cooling after solution heat treatment and the volume fraction of matrix in the alloy at room temperature are used as coordinate axes, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Ni-Ti alloy having a high rigidity and reversible deformation, and more specifically, a high rigidity reversible deformation used for medical purposes, accessories, and antennas. The present invention relates to a Ni-Ti alloy material having More specifically, it is mainly a catheter guide wire, a stent, etc. for medical use, a bracelet, a spectacles template etc. for accessories, and a high-rigidity reversible type antenna mainly used for mobile phone antennas. The present invention relates to a Ni-Ti alloy having deformation.

[0002]

2. Description of the Related Art Conventionally, Ni—Ti alloys have been used as cold-worked materials or low-temperature heat-treated materials in order to provide rigidity. However, when they are deformed during use, strain remains. , It may not return to the original shape completely. On the other hand, if heat treatment is applied to reduce the residual strain, the rigidity becomes extremely low due to stress-induced transformation or twinning deformation. Highly rigid Ni with little residual strain
There are some documents that suggest that a method of performing a low temperature heat treatment after processing is preferable for obtaining a Ti-based alloy material, but for the above reason, it is difficult to determine an appropriate range of processing and heat treatment. It was

[0003]

As described above, when the conventional Ni-Ti alloy is deformed, the strain may remain and the shape may not be completely returned to the original shape. Further, in order to reduce the residual strain. However, the present invention has a problem that the rigidity becomes extremely low due to stress-induced transformation or twinning deformation. Therefore, the present invention exhibits almost perfect reversible deformation behavior during use and has a relatively large strain region (deformation). region)
Also provides a high-rigidity Ni-Ti based alloy having high rigidity and reversible deformation.

[0004]

As a result of intensive studies in view of the above problems, the present inventor has found that the A _f temperature after solution treatment and Ni
It has been found that the above problems can be solved by defining the volume ratio of the matrix phase in the —Ti alloy, and the present invention has been completed based on this finding. That is, the present invention (the invention according to claim 1) has a composition of Ni of 50.4 to 52.
A Ni-Ti alloy containing 0 at% and the balance Ti, in the coordinate plane with the _Af temperature when cooled after the solution treatment and the volume ratio of the mother phase in the alloy at room temperature as coordinate axes. , (A _f temperature (° C.), mother phase volume ratio (%)) have coordinates (60, 50), (60, 50)
70), (-75,95) and (-75,55) 4
This is a Ni—Ti based alloy having a high rigidity type and reversible deformation, characterized in that the A _f temperature and the volume fraction of the matrix phase are within a region where points are connected by a straight line in this order.

The present invention (the invention according to claim 2) is
The composition contains 50.4 to 52.0 at% Ni, and further contains Co, Fe, Cr, Mn, Mo, Pd, Zr, Hf, and A.
u, Cu, V, one or more selected from the group consisting of 0.1 to 2.0 at% in total, with the balance being Ti
In the coordinate plane having the _Af temperature when cooled after the solution treatment and the volume ratio of the parent phase in the alloy at room temperature as coordinate axes, the (A _f
The coordinates indicated by the temperature (℃) and the matrix volume ratio (%) are
The A _f temperature and the volume fraction of the mother phase are within a region where four points of (60, 50), (60, 70), (-75, 95) and (-75, 55) are connected by a straight line in this order. It is a Ni—Ti based alloy having high rigidity and reversible deformation. Furthermore, the present invention (the invention according to claim 3)
Is a NiTi alloy material having the composition according to claim 1 or 2, and is a coordinate plane having coordinate axes of the A _f temperature when cooled after the solution treatment and the volume ratio of the matrix phase in the alloy at room temperature. In, the coordinates indicated by (A _f temperature (° C.), parent phase volume ratio (%)) are (40, 55), (40,
70), (-10, 80) and (-10, 55) 4
This is a Ni—Ti based alloy having a high rigidity type and reversible deformation, characterized in that the A _f temperature and the volume fraction of the matrix phase are within a region where points are connected by a straight line in this order.

[0006]

The reason for limiting the alloy composition in the Ni-Ti alloy of the present invention will be shown. In the present invention, the alloy composition with the Ni content of 50.4 to 52.0 at% is 52.0a.
This is because it is difficult to manufacture the composition at t% or more, and at the composition temperature of 50.4 at% or less, the residual strain is too large near the room temperature and the operating temperature near the body temperature. In addition, as an accessory component, Co: 0.1 to 2.0a
t%, Fe: 0.1 to 2.0 at%, Cr: 0.1
2.0 at%, Mn: 0.1 to 2.0 at%, Mo:
0.1-2.0 at%, Pd: 0.1-2.0 at%,
Zr: 0.1 to 2.0 at%, Hf: 0.1 to 2.0 a
t%, Au: 0.1 to 2.0 at%, Cu: 0.1
2.0 at%, V: 0.1 to 2.0 at% and 1 or 2 or more elements selected from the group consisting of 0.1 in total.
The rigidity is improved by adding ~ 2.0 at%. C
o, Fe, Cr, Mn, Mo, Pd, Zr, Hf, A
If at least one at least one selected from the group consisting of u, Cu and V is 0.1 at% or less in total, the effect does not appear, and if it is 2.0 at% or more, production becomes difficult.

The _Af temperature of the Ni-Ti alloy of the present invention when cooled after the solution treatment and the volume ratio of the matrix phase in the alloy at room temperature will be described with reference to FIG. Figure 1
Horizontal axis A _f temperature [℃] when cooled after the solution treatment as coordinate axes, is obtained by the vertical axis the volume fraction of the matrix phase of the alloy at room temperature [%], on the coordinate plane (A _f
Coordinates indicated by temperature (° C) and volume ratio of parent phase (%) are A
Point (60, 50), B point (60, 70), C point (-7
5, 95) and D point (-75, 55) were connected by a straight line in order from A point to D point. A _f temperature [° C.] when cooled after solution treatment in the Ni—Ti alloy of the present invention
And the volume ratio [%] of the matrix phase in the alloy at room temperature are shown in FIG.
Within the range surrounded by a straight line from the point A to the point D.

In the present invention (claims 1 and 2), the coordinates indicated by (A _f temperature (° C.), mother phase volume ratio (%)) are points A (60, 50) and B (60, 50). 70), point C (-75,
95) and D point (-75, 55) within the range of connecting straight lines from A point to D point in order that the volume ratio of the mother phase is B point (60, 70), C point. If it is larger than the straight line connecting (-75, 95), the residual strain becomes large and reversible deformation does not occur. In addition, the volume ratio of the mother phase is point A (60,5
If it is smaller than the straight line connecting points 0) and D (-75, 55), the stress-induced transformation causes a marked decrease in rigidity, making it unsuitable for practical use. The reason for setting the A _f temperature [° C.] after cooling after the solution treatment to −75 to 60 ° C. will be described. In order to keep the A _f temperature at −75 ° C. or lower,
Since it corresponds to the case where the composition is 52 at% Ni or more or the sub-component element is added at a high concentration, the manufacturing becomes difficult. On the other hand, when the A _f temperature is 60 ° C. or higher, a large amount of martensite phase exists at a temperature near room temperature or near body temperature, and the martensite phase deforms with a low stress, resulting in a decrease in rigidity. Is.

For the above reasons, (A _f temperature (° C.), volume ratio (%)) is the coordinates in FIG. 1, point A (60, 50), point B (60, 70), point C (−75, 95). ) And D point (-75, 55) are limited to the range connected by a straight line in the order from A point to D point. Further, in the present invention (claim 3), FIG. Coordinates, E point (40,5
5), F point (40, 70), G point (-10, 80), and H point (-10, 55) within the area surrounded by a straight line from E point to H point. Is preferred.

The A _f temperature depends on the processing and heat treatment conditions at the time of manufacturing the Ni—Ti alloy. A _f dependent only on alloy composition
In order to obtain a transformation temperature such as a temperature, a treatment of quenching after the solution treatment is usually performed. In the present invention, after heating at 950 ° C. for 1 hour, the A _f temperature was obtained from the oil-cooled material. Next, a method for obtaining the volume ratio of the mother phase will be described. As the phases that may constitute the structure of the Ni—Ti alloy of the present invention, there are a matrix phase, a martensite phase, an R phase, and a minute amount of precipitation phase. Each crystal grain was subjected to electron beam diffraction by a TEM (transmission electron microscope) to identify the phase of the crystal grain, and to what extent each phase existed was investigated. In the Ni—Ti alloy of the present invention, most of the phases are a body-centered cubic matrix and a monoclinic martensite phase. Since both have different crystal lattices, which phase is each crystal? Can be determined. The phase can be identified not only by electron diffraction by TEM but also by X-ray diffraction, electron diffraction (EBSD) by SEM (scanning electron microscope), and the like. For each sample, "the number of diffraction images of the mother phase / the number of all diffraction images" was defined as the volume ratio of the mother phase.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The highly rigid Ni-Ti alloy having reversible deformation according to the present invention has both high rigidity and reversible deformability, and exhibits excellent characteristics in rigidity and residual strain. This alloy material is industrially useful, for example, for catheter guide wires, stents and the like for medical purposes, bracelets and glasses templates for personal accessories, and for mobile phone antennas and the like as antennas.

[0012]

EXAMPLES Table 1, FIG. 1 and FIG.
2 will be described. Table 1 shows the Ni content of the Ni-Ti alloy,
Amount of additive element, A_fTemperature, heat treatment, matrix volume ratio, rigidity, residual
Fig. 1 shows the residual strain.
And (A _fThe temperature (° C) and volume ratio (%) are shown. table
Each Ni-Ti alloy shown in 1 is melt cast, forged, hot
After working, the diameter is reduced while repeating cold wire drawing and annealing.
After the final annealing, cold drawing with 35% surface reduction is performed to obtain the wire diameter.
A plurality of wire rods of 2.0 mm to 0.5 mm were produced. This
Various heat treatments were performed on these wire rods to obtain sample pieces.

[Table 1]

Further, using a transmission electron microscope, each Ni
In order to determine whether the crystal grains in the -Ti alloy are the parent phase or the martensite phase, the sample was sliced for an electron microscope. First, a sample piece having a thickness of about 0.5 mm was cut out from each wire and mechanically polished to a thickness of about 0.1 mm. Next, a fine hole was formed in the center of the sample by electrolytic polishing. Then, for the thinned sample,
A single crystal grain was irradiated with an electron beam, and an electron beam diffraction image was taken. Twenty crystal grains were arbitrarily selected for one sample, a diffraction image was taken, and the matrix phase volume ratio was obtained. The sample temperature is room temperature. The A _f temperature (end temperature of austenite transformation (reverse transformation of martensite)) was measured by using a sample subjected to oil cooling treatment after heat treatment at 950 ° C. for 1 hour, and DS
It was determined from the temperature rising process by C (differential scanning calorimeter) measurement.
A tensile test was performed at room temperature to examine the rigidity and residual strain. As for rigidity, if the stress-strain curve in the region where the strain amount is 0 to 4% is a perfect straight line or a nearly straight line, “◎”,
Those having an obvious inflection point were marked with "x". A curve having an intermediate shape between “◎” and “x” was designated as “◯”.

As is clear from Table 1, the results show that the Ni--Ti alloy material according to the present invention has both high rigidity and reversible deformability. Among the present invention, Example No. 3, N
o. 4, No. 5, No. No. 7, No. 8, No.
Regarding No. 9, both the rigidity and the residual strain, or one of them was “⊚”, that is, extremely excellent characteristics were exhibited. On the other hand, Comparative Example No. 10, No. 12 is
Although it exhibits high rigidity, the residual strain exceeds 0.5%. These have so-called work hardening type stress-strain characteristics. That is, the strain remained because the matrix volume ratio was too small. In addition, Comparative Example No. In No. 11, the residual strain is within 0.5%, but the rigidity is low. This is a so-called superelastic type stress-strain characteristic. That is, since the matrix phase volume ratio is too large, stress-induced martensite transformation from the matrix phase to the martensite phase occurs at low stress, and high rigidity cannot be obtained.

FIG. 2 shows an example of a stress-strain curve loading process. Example No. No. 4 does not form an inflection point from the elastic deformation region at the initial stage of strain to strain of 3 to 4%, and has the characteristic that the rigidity is higher than the others in the high strain region. No. 5 also had a feature of high rigidity. On the other hand, Comparative Example No. No. 11 has an inflection point at a strain of about 1%, and the stress value is low in a high strain region. This is a material with low rigidity. Such an inflection point is due to the stress-induced martensitic transformation or twin deformation of the martensitic phase. Therefore, by determining the linearity of the stress-strain curve, that is, whether or not there is an inflection point,
You can see the size of the rigidity.

[0016]

As described above, according to the present invention,
Shows almost complete reversible deformation behavior during use, and exhibits high rigidity even in a relatively large strain area (deformation area),
It is possible to obtain a NiTi-based alloy material having both high rigidity and reversible deformability, and it has an industrially remarkable effect for medical use, accessories, and antennas.

[Brief description of drawings]

FIG. 1 is a diagram showing coordinates of A _f temperature and matrix volume fraction.

FIG. 2 is a diagram showing a stress-strain curve.

[Explanation of symbols]

A to D, E to G A _f Temperature and mother phase volume ratio Coordinate points 1 to 12 A _f temperature and mother phase volume ratio coordinate points of the present invention region

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masato Asai             2-6-1, Marunouchi, Chiyoda-ku, Tokyo             Kawa Electric Industry Co., Ltd. (72) Inventor Hiroshi Horikawa             5-1-8 Higashi-Hachiman, Hiratsuka City, Kanagawa Prefecture             Furukawa Techno Material (72) Inventor Toyonobu Tanaka             5-1-8 Higashi-Hachiman, Hiratsuka City, Kanagawa Prefecture             Furukawa Techno Material

Claims (3)

[Claims] 1. The composition has a Ni content of 50.4 to 52.0 at%.
A Ni-Ti alloy containing Ti, the balance being Ti, in the coordinate planes with the _Af temperature when cooled after the solution treatment and the volume ratio of the parent phase in the alloy at room temperature as coordinate axes, The coordinates indicated by A _f temperature (° C.) and mother phase volume ratio (%) are (60, 50), (60, 70), (−
75, 95) and (-75, 55) having a high rigidity reversible deformation characterized by having the A _f temperature and the volume fraction of the mother phase in a region connected by a straight line in this order. Ni-Ti alloy. 2. The composition has Ni of 50.4 to 52.0 at%.
In addition, Co, Fe, Cr, Mn, Mo, Pd,
A Ni-Ti alloy material containing 0.1 to 2.0 at% in total of one type or two or more types selected from the group consisting of Zr, Hf, Au, Cu and V, and the balance being Ti, On the coordinate planes with the A _f temperature when cooled after the solution treatment and the volume ratio of the matrix phase in the alloy at room temperature as coordinate axes, (A _f temperature (° C.), matrix phase volume ratio (%)) The coordinates shown are (60, 50), (60, 70), (-7
5, 95) and (-75, 55) have a high rigidity type reversible deformation characterized in that the A _f temperature and the volume fraction of the parent phase are within a region connected by straight lines in this order. Ni-Ti alloy. 3. NiT having the composition according to claim 1 or 2.
In the coordinate planes of the i alloy material, the A _f temperature when cooled after the solution treatment and the volume ratio of the matrix phase in the alloy at room temperature are coordinate axes, (A _f temperature (° C.), matrix phase The coordinates indicated by the volume ratio (%) are (40, 55),
(40,70), (-10,80) and (-10,5)
In the area where the four points in 5) are connected by a straight line in this order, the A _f
A high-rigidity reversible Ni-Ti based alloy having a temperature and a volume fraction of the parent phase.