JPH062059A - Superelastic material low in residual strain - Google Patents

Abstract

PURPOSE:To obtain the objective Ni-Ti superelastic material high in the workability of manufacture, low in residual strain after deformation and excellent in superelastic properties by adding Fe into an alloy consisting of approximately equivalent amounts of Ni and Ti and forming its compsn. into a specified one. CONSTITUTION:This superelastic material has a compsn. in a region surrounded by angles A, B, C, D and E of A (50.7% Ni and 49.3% Ti, by atom), B (51.0% Ni and 49.0% Ti), C (51.0% Ni, 47.0% Ti and 2.0% Fe), D (50.2% Ni, 47.8% Ti and 2.0% Fe) and E (50.2% Ni, 49.3% Ti and 0.5% Fe) in the phase diagram of a ternary alloy of Ni, Ti and Fe, and is high in workability, and in which the increase of cost is not caused. The material is obtd. by subjecting the alloy having the compsn. to final annealing, thereafter subjecting it to cold working at about 20 to 60% draft, and subsequently executing superelasticity heat treatment at about 400 to 570 deg.C for about 20 to 200min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Ni-Ti superelastic material having excellent workability in the manufacturing process and excellent superelasticity with a small residual strain.

[0002]

2. Description of the Related Art A Ni-Ti alloy having an atomic percentage of about 1: 1 has a cubic structure in the parent phase of a high temperature phase, and when cooled, it transforms at a martensitic transformation temperature and has a monoclinic structure. Be in phase. If you expect a shape memory effect,
The shape recovery phenomenon due to the change in the crystal structure due to this transformation is utilized. On the other hand, these alloys can be used as a superelastic material only when the martensitic transformation temperature is equal to or lower than the use environment temperature. This is because when an external force is applied in the matrix phase, stress causes induced martensitic transformation. Therefore, it is necessary to change the transformation temperature of the superelastic material to a relatively low temperature range. In order to lower the transformation temperature, it is already known that Ni-Ti alloy is made to have an excessive composition of Ni in an atomic ratio of 1: 1 or a small amount of a third element such as Fe is added. There is. (Reference: T. Honma, M. Matsumoto, Y. Shug
o, M. Nishida, and I. Yamasaki; Effect of thermal
cycles and substitution elementson the phase trnas
formations of Ti-Ni; Proceedings of the Fourth Int
ernational Conference on Titanium .: 1456 (1980),
Japanese Patent Application No. 61-53307). As described above, the superelastic material and the shape memory material have different martensite transformation temperatures, but there are great differences in the usage, required properties, and effects. For example, the super elastic material is 6 to
While a large elastic region of 8% is required, a shape memory material is required to have a suitable shape change temperature, a large shape recovery force, a shape recovery amount, and a material with little deterioration after repeated use. As a result, as a matter of course, the manufacturing method and the alloy composition may be different or may be overlapped. Even when the composition regions of the shape memory material and the superelastic material overlap, the effect obtained is completely different. As described above, if Ni is excessive, one method for obtaining a superelastic material is as follows.
Although the transformation temperature is lowered, the workability is severely deteriorated, which causes a problem in manufacturing. In addition, increasing Ni increases the cost in the industry and is not preferable. The same applies to the alloy composition of the third element in the above reference, and it is necessary to select the alloy composition in consideration of workability and superelasticity from the viewpoint different from that of the shape memory material. In particular, in the case of adding the third element, even if the transformation temperature is lowered by increasing the amount of the third element to give superelasticity characteristics, the recovery amount after large deformation is small depending on the composition of Ni and Ti, The residual strain may become large. Therefore, there is a problem that it cannot be used as a superelastic material.

[0003]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, the present invention is excellent in superelastic material because it has good workability in manufacturing and has a small residual strain after deformation in superelastic characteristics. It is the development of a material with superelasticity.

[0004]

According to the present invention, in the ternary alloy phase diagram of Ni, Ti and Fe, the composition of the corners indicated by A, B, C, D and E is atomic%, and A: Ni 50. 7%, Ti 49.3% B: Ni 51.0%, Ti 49.0% C: Ni 51.0%, Ti 47.0%, F
e 2.0% D: Ni 50.2%, Ti 47.8%, F
e 2.0% E: Ni 50.2%, Ti 49.3%, F
e A superelastic material having a small residual strain, which has a composition within a region surrounded by 0.5%.

[0005]

The present invention has found that by defining the composition of the superelastic alloy within the above range, a superelastic material having excellent workability and small residual strain can be obtained. In the present invention, the alloy composition of the superelastic material is defined as described above because the Ni--Ti--F shown in FIG.
e In the ternary alloy phase diagram, the workability is inferior on the right side of the line connecting the corners B and C and on the upper side of the line connecting the corners D and C, which is not preferable in manufacturing. On the left side of the line connecting the corners A, E, and D, the residual strain is large and it cannot be used as a superelastic material. Therefore, as the superelastic material, an alloy in the region connected by the corners A, B, C, D and E is suitable. And as a manufacturing method of the above-mentioned alloy, the processing rate at the time of cold working after the final annealing is set to 20 to 60%, and the subsequent superelastic heat treatment is performed at 400%.
By applying it at ˜570 ° C. for 20 to 200 minutes, desired superelasticity can be obtained. The superelastic material having such improved properties is suitable for brassiere wires, spectacle frame materials, orthodontic wires, catheter guide wires, and the like. Also, because it has excellent workability,
The manufacturing cost is low and the processing of thin wires is easy.

[0006]

EXAMPLES An example of the present invention will be described below.
Alloys having the compositions shown in Table 1 were cast, hot-worked, then annealed and cold-worked repeatedly to produce an alloy wire with a final working rate of 30% and a wire diameter of 2 mm. For the workability test, the above-mentioned 2 mm wire rod is 750
After annealing at 15 ° C. for 15 minutes, wire drawing was carried out with a die, and the work ratio at which wire breakage occurred 3 times or more was measured and defined as the limit work ratio.
Therefore, from the viewpoint of manufacturing, the larger the critical machining rate, the smaller the number of steps and the manufacturing cost. Next, for the measurement of residual strain in the superelastic property, a wire rod with a wire diameter of 2 mm was 480
Annealing was performed at 1 ° C. for 1 hour, and a tensile test was performed at room temperature. The stress-strain curve of the tensile test is as shown in FIG.
The residual strain was measured by pulling the strain up to 6% and then unloading the strain. This residual strain is at least 1%
Unless it is below, it cannot be used as a super elastic material that often uses bending force, such as a wire for a brassiere. Note that the superelasticity test was omitted for those with a critical working rate of 30% or less. Table 1 also shows the measurement results of the limit working rate and the residual strain.

[0007]

[Table 1]

As is clear from Table 1 and FIG. 1, the corners B,
Workability is inferior on the right side of the line connected by C and on the upper side of the line connected by corners D and C. Also the corners A, E,
On the left side of the line connected by D, the residual strain is large,
It cannot be used as a super elastic material. Therefore, it can be seen that the alloy within the region bounded by the corners A, B, C, D and E is suitable as the superelastic material.

[0009]

As described above, according to the present invention,
Manufacturing cost can be reduced, and Ni-Ti has excellent superelasticity.
A system-based superelastic material is obtained, and this material has a remarkable industrial effect such as expanding the range of application of the superelastic material.

[Brief description of drawings]

FIG. 1 is a phase diagram of a Ni—Ti—Fe ternary alloy according to an embodiment of the present invention.

FIG. 2 is a stress-strain curve diagram of a superelastic alloy according to an example of the present invention.

Claims (1)

[Claims] 1. In a ternary alloy phase diagram of Ni, Ti and Fe, the composition of the corners indicated by A, B, C, D and E is atomic% and A: Ni 50.7%, Ti 49.3%. B: Ni 51.0%, Ti 49.0% C: Ni 51.0%, Ti 47.0%, F
e 2.0% D: Ni 50.2%, Ti 47.8%, F
e 2.0% E: Ni 50.2%, Ti 49.3%, F
e A superelastic material having a small residual strain, which has a composition within a region surrounded by 0.5%.