JPH059686A - Method for manufacturing NiTi-based shape memory alloy - Google Patents

Abstract

(57) [Summary] [Objective] A manufacturing method in which a wide hysteresis characteristic is obtained by shifting the martensitic transformation temperature of a NiTi-based shape memory alloy used for a connector or the like to a low temperature side and the reverse transformation temperature to a high temperature side. [Structure] 49.5 to 51.5% Ni in atomic% balance T
i, Ni 49.5 to 51.5%, and Fe, C
1% or more of o, Cr, V, Pd, and Al in total of 1% and the balance Ti, Ni 38.0 to 52.0%,
Ni consisting of 5 to 12% of Cu or Nb and the balance of Ti
After subjecting the Ti-based alloy to shape memory treatment at a temperature of 500 to 800 ° C, 4 to 12% in a temperature environment of Ms point + 30 ° C or less.
The deformation strain of is given to the low temperature side of the martensite transformation point,
Ni characterized by shifting the reverse transformation temperature to a high temperature side
A method for manufacturing a Ti-based shape memory alloy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a NiTi-based shape memory alloy which raises the reverse transformation temperature and lowers the martensite transformation temperature by deformation.

[0002]

2. Description of the Related Art Shape memory alloys have a cubic crystal structure in the parent phase of a high temperature phase, and when cooled, they transform at the martensite transformation temperature and have a monoclinic structure martensite phase (hereinafter M phase). Becomes When this alloy is heated, it undergoes reverse transformation and returns to the parent phase via the reverse transformation temperature. The martensitic transformation temperature and the reverse transformation temperature are not the same temperature, and the former is lower than the latter. This temperature difference is called temperature hysteresis of transformation. When the shape memory alloy is applied as a temperature sensor, it is preferable that this temperature hysteresis is narrow.
That is, it is required to operate at the same temperature when the temperature rises and when the temperature falls. On the other hand, it is desirable that an element that is deformed and fixed by heating, such as a connector, has a reverse transformation temperature in a high temperature range and a transformation temperature to a soft martensite phase in a low temperature range as much as possible. In response to such requirements, when the Ni—Ti alloy was subjected to ordinary casting, hot working, cold working, and then subjected to shape memory treatment, the temperature hysteresis was at most 40 ° C.

[0003]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, the present invention has a reverse transformation temperature of ordinary Ni-T.
This is a method for producing a shape memory alloy having a temperature higher than i and a martensitic transformation temperature in a low temperature range.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to atomic percent Ni.
After shape memory treatment of a NiTi alloy consisting of 49.5 to 51.5% and the balance Ti at a temperature of 500 to 800 ° C, a deformation strain of 4 to 12% is applied in a temperature environment of Ms point + 30 ° C or less. NiT characterized by shifting the martensitic transformation temperature to the low temperature side and the reverse transformation temperature to the high temperature side.
A method for producing an i-based shape memory alloy is defined in claim 1, which contains 49.5 to 51.5% Ni in atomic%, and further comprises Fe, Co,
A NiTi-based alloy containing 1% or less of Cr, V, Pd, and Al in a total amount of 1% or less and the balance Ti is 50
After performing shape memory treatment at a temperature of 0 to 800 ° C, a deformation strain of 4 to 12% is applied in a temperature environment of Ms point + 30 ° C or less, the martensite transformation temperature is set to the low temperature side, and the reverse transformation temperature is set to the high temperature side. The method for producing a NiTi-based shape memory alloy is characterized in that
After shape memory treatment of a NiTi-based alloy consisting of 8.0 to 52.0% and 5 to 12% of Cu as the balance Ti at a temperature of 500 to 800 ° C., 4 to 4 in a temperature environment of Ms point + 30 ° C. or less.
A method for producing a NiTi-based shape memory alloy is characterized in that a deformation strain of 12% is applied, the martensite transformation temperature is shifted to a low temperature side, and the reverse transformation temperature is shifted to a high temperature side. 38.0 to 52.0% and Nb to 5
NiTi alloy consisting of 12% and the balance Ti is 500 to 8
After shape memory treatment at a temperature of 00 ° C, Ms point +30
Claiming a method for producing a NiTi-based shape memory alloy, characterized in that a deformation strain of 4 to 12% is applied in a temperature environment of ℃ or less, and the martensitic transformation temperature is shifted to a low temperature side and the reverse transformation temperature is shifted to a high temperature side. It is defined as item 4.

[0005]

In other words, according to the present invention, the NiTi alloy having the above composition is processed into a predetermined shape, and the shape memory treatment is performed at 500 ° C. or higher for 80
It is performed at a temperature of 0 ° C. or lower, and by giving a deformation strain of 4% or more and 12% or less in a temperature environment of Ms point + 30 ° C. or less, the martensite transformation temperature is shifted to the low temperature side and the reverse transformation temperature is shifted to the high temperature side. A NiTi-based shape memory alloy having a wide hysteresis is obtained. Especially for wire rods, NiT having a wide hysteresis can be easily obtained by linearly shape-memory processing under the same conditions and applying a deformation strain of 4% or more and 12% or less in the longitudinal direction in a temperature environment of Ms point + 30 ° C or less.
An i-based shape memory alloy wire rod is obtained. The composition range of the alloy targeted by the present invention is 49.5 to 5 in atomic% of Ni.
1.5% balance Ti or Ni 49.5 to 51.5 and F
eNi, Co, Cr, V, Pd, and Al, NiTi-based alloys containing 1% or less in total of 1% or less and the balance Ti, 38.0 to 52% Ni and 5 to 12% Cu.
%, NiTi-based alloy consisting of balance Ti, and N in atomic%
iTi is 38.0 to 52, Nb is 5 to 12%, and the balance is a NiTi-based alloy or the like composed of Ti. When the amount of Ni is less than the above lower limit and more than the above upper limit, shape memory characteristics are not exhibited and workability is also deteriorated. . Fe, Co, Cr, V, Pd, Al,
The NiTi-based alloy to which Cu and Nb are added also has the above-mentioned wide hysteresis characteristic, but if it is out of the above range, the workability is deteriorated. If the memory heat treatment temperature is less than 500 ° C, the shape is not accurately memorized. On the other hand, if the temperature exceeds 800 ° C, oxidation of the alloy surface will be severe, which is not preferable in terms of materials. If the deformation strain amount after shape memory treatment is less than 4%, the reverse transformation temperature does not rise sufficiently, and if it exceeds 12%, the recovery strain amount decreases significantly. The deformation temperature is preferably lower than the Ms temperature,
When the Ms point exceeds + 30 ° C., the recovery strain amount also decreases.

[0006]

EXAMPLES Next, examples of the present invention will be described. Table 1
After casting the alloy having the composition shown in Fig. 1, hot working, and repeating annealing and cold working, an alloy wire having a wire diameter of 1 mm was produced.

[0007]

[Table 1]

This alloy was subjected to a linear memory heat treatment under the treatment conditions shown in Table 2. Further, tensile deformation was applied by a tensile tester at an atmospheric temperature controlled by a thermostatic chamber as shown in Table 2. The transformation temperature Ms and As point of the alloy before deformation were determined by the DSC method.

[0009]

[Table 2]

The alloy wire after the treatment was subjected to a constant load temperature cycle test to determine the As point, the Ms point and the amount of shape recovery strain as shown in FIG. The results are shown in Table 2. In the comparative example in the table, the recovery strain does not reach 4% or more because either the shape memory processing of the present invention or the condition for imparting the deformation strain is missing.
Figure 2 shows the processing numbers. The As and Ms points obtained by the constant strain test after deformation in 2 to 7 are shown. The value of 0% is DS
The transformation temperature before deformation obtained by the C method is shown. When the deformation strain exceeds 4%, the As point rises by 10 ° C or more and the Ms point also falls by 3 ° C or more. FIG. 3 shows the amount of recovery strain of this sample. It can be seen that the recovery strain is extremely reduced when the deformation strain exceeds 12%. The sample No. is shown in FIG. 1
The relationship between the deformation temperature and the recovery strain in 4 to 18 is shown.
It is clear that the higher the deformation temperature, the more the recovery strain decreases. Therefore, the deformation temperature is preferably Ms point + 30 ° C. or lower. The alloy system is NiTi binary alloy, but Fe, C
Even in the alloy containing o, Cr, V, Pd, Al, Cu, and Nb, the reverse transformation temperature shifts to the high temperature side, and the martensite temperature shifts to the low temperature side.

[0011]

As described above, according to the present invention, N
In the iTi-based shape memory alloy, the reverse transformation temperature is set to the high temperature side,
The present invention provides a shape memory alloy in which the martensite transformation temperature is set to a low temperature side, which leads to the application of an element or the like that is deformed and then fixed by an increase in temperature, and has a remarkable industrial effect.

[Brief description of drawings]

FIG. 1 is a graph showing strain-temperature characteristics of a NiTi-based shape memory alloy according to an example of the present invention.

FIG. 2 is a graph showing the relationship between temperature and deformation strain of a NiTi-based shape memory alloy according to an example of the present invention.

FIG. 3 is a graph showing the relationship between recovery strain and deformation strain of a NiTi-based shape memory alloy according to an example of the present invention.

FIG. 4 is a graph showing the relationship between recovery strain and deformation temperature of a NiTi-based shape memory alloy according to an example of the present invention.

Claims (4)

[Claims] 1. A NiTi-based alloy consisting of 49.5 to 51.5% of Ni in atomic% and the balance of Ti is subjected to shape memory treatment at a temperature of 500 to 800 ° C., and then subjected to a temperature environment of Ms point + 30 ° C. or less. A method for producing a NiTi-based shape memory alloy, characterized in that a deformation strain of -12% is applied and the martensitic transformation temperature is shifted to a low temperature side and the reverse transformation temperature is shifted to a high temperature side. 2. The alloy contains 49.5 to 51.5% of Ni in atomic%, and further contains 1 out of Fe, Co, Cr, V, Pd and Al.
After performing shape memory treatment at a temperature of 500 to 800 ° C. for a NiTi alloy containing 1% or less in total of 1% or more and 2% or more in total, and 4 to 4 in a temperature environment of Ms point + 30 ° C. or less.
A method for producing a NiTi-based shape memory alloy, which comprises imparting 12% deformation strain and shifting the martensitic transformation temperature to a low temperature side and the reverse transformation temperature to a high temperature side. 3. Ni: 38.0-52.0% in atomic%,
NiTi-based alloy consisting of 5 to 12% Cu and the balance Ti is 5
After performing shape memory treatment at a temperature of 00 to 800 ° C., Ms
A method for producing a NiTi-based shape memory alloy, characterized in that a deformation strain of 4 to 12% is applied in a temperature environment of a point + 30 ° C. or less, and the martensite transformation temperature is shifted to a low temperature side and the reverse transformation temperature is shifted to a high temperature side. . 4. Ni: 38.0-52.0% in atomic%,
After performing a shape memory treatment on a NiTi-based alloy composed of 5 to 12% of Nb and the balance of Ti at a temperature of 500 to 800 ° C., M
Manufacture of a NiTi-based shape memory alloy characterized in that a deformation strain of 4 to 12% is applied in a temperature environment of s point + 30 ° C. or lower, and the martensite transformation temperature is shifted to a low temperature side and the reverse transformation temperature is shifted to a high temperature side. Method.