JP2573507B2 - Shape memory alloy and manufacturing method thereof - Google Patents

Description

The present invention relates to a shape memory alloy which operates at a temperature of 30 ° C. or lower and has a large load difference between high temperature and low temperature. Things.

[Prior Art] It is well known that TiNi alloys exhibit a remarkable shape memory effect accompanying the reverse transformation of thermoelastic martensitic transformation. Also, ternary alloys obtained by adding a third element to TiNi alloys
Similar to TiNi alloys, it is known to exhibit a shape memory effect. In particular, the Cu-added ternary alloy has a smaller operating temperature composition dependency than the TiNi alloy, and can be easily reproduced and economically manufactured within the range of industrial manufacturing parameters. No. 1993. The best way to bring out the shape memory characteristics of TiNi alloy is to perform a short time treatment at about 500 ° C after cold working.
Various shape memory springs have been made based on this method and are now used as actuators.

[Problems to be Solved by the Invention] However, in Cu-added ternary alloys, by adding Cu, the structure of the martensitic phase changes from monoclinic to orthorhombic with an increase in the amount of Cu added, Accordingly, the temperatures at which the martensite phase and the parent phase appear gradually approach each other, and the temperature hysteresis decreases. on the other hand,
When the amount of Cu added increases, the structure dependence of the operating temperature decreases, so in order to reduce the operating temperature to 30 ° C or lower, the main component
Ti must deviate significantly from the stoichiometric value. However, the workability (hot and cold) of the Ti—Ni alloy gradually deteriorates as the composition deviates from the stoichiometry, and the Ti48Ni52 alloy, Ti52Ni48 alloy, and the like can hardly be worked. Furthermore, in the case of a Cu-added ternary alloy, a TiCu phase begins to precipitate with an increase in the Cu addition amount, which adversely affects workability. Therefore, in order to shift the operating temperature, the Ti concentration is shifted from the stoichiometric value. Processing is almost impossible.

In the TiNi alloy, a method of making a spring with a small hysteresis generally uses the short-time treatment at approximately 500 ° C. of the aforementioned Buheler et al. The load required to deform the spring at low temperatures is extremely large, and the difference between the deformation load of the spring at high temperatures (during operation) and at low temperatures is smaller than that of the solution that has been solution-treated (at 700 ° C. or more for 30 minutes). For this reason, the output (force at high temperature-force at low temperature) of the TiNi binary alloy is small, and there remains a problem in spring manufacturing and design.

SUMMARY OF THE INVENTION An object of the present invention is to provide a shape memory alloy which operates at a temperature of 30 ° C. or less, which has excellent workability, and has a large output at this time, and a method of manufacturing the same.

[Means for Solving the Problems] According to the present invention, T in the range of 49 to 50 atomic percent
i from more than 5 atomic percent to 20 atomic percent C
u, V in the range of 0.5-3.0 atomic percent, and the balance N
Thus, a shape memory alloy characterized by comprising i is obtained.

According to the present invention, there is also provided a TiNiCuV alloy ingot comprising Ti in the range of 49 to 50 atomic percent, Cu exceeding 5 atomic percent to 20 atomic percent, V in the range of 0.5 to 3.0 atomic percent, and the balance of Ni. A method for producing a shape memory alloy which is subjected to a homogenizing treatment, a hot working and a cold working, wherein a heat treatment is carried out at a temperature of substantially 425 ° C. for substantially one hour after the cold working. Is obtained.

Example An example of the present invention will be described with reference to the drawings.

After homogenizing a TiNi-based alloy having a chemical composition as shown in Table 1 and having a chemical composition shown in Table 1 to No. 16 at a temperature of 900 ° C. for 2 hours, a hot hammer, a hot roll, And cold working was performed and the workability was examined. Table 1 shows the results.

In Table 1, Nos. 1 to 4, 8, 9, 11, and 13
15 to 15 are comparative examples, and Nos. 5 to 7, 10, 12, and 16 are examples of the present invention.

In the table, ○ indicates good processability, Δ indicates normal processability, and × indicates no processability. An asterisk of the operating temperature indicates that the hysteresis is large. In the table, hot working was performed at a working rate of 30% at a time. As a result, the fourth alloy according to the comparative example had cracks during processing and had some difficulty in workability, whereas the seventh alloy according to the example was processed smoothly (No. The fourth and seventh alloys have the same amount of Ti as the main element.) In addition, cold working was performed from 3 mm to 1 mm in diameter while repeating annealing at a temperature of 750 ° C., and final annealing was performed at 1.3 mm in diameter, and then processed to 1.0 mm in diameter. as a result, A remarkable difference was observed in the workability between the fourth and seventh alloys, and it was found that the seventh alloy according to the example had better workability than the fourth alloy according to the comparative example.

The alloy wires in the table that were cold workable were 425 ° C each.
And a temperature load curve under strain of 0.25% elongation and strain was measured. Sixth Example
FIG. 1 shows the measurement results of the alloy No. 1. Measurement curves of the first and third alloys according to the comparative example are shown in FIGS. 2 and 3, respectively. Each of the curves 11, 13 and 16 draws a hysteresis loop. The operating temperatures shown in the table are the first
In FIGS. 3 to 3, Af11, Af13, and Af1 shown on the curves 11, 13, and 16 are shown, and these temperatures indicate the temperature Af when the alloy wire is heated and the shape recovery is completed. ing.

In the second and third alloys according to the comparative examples, the operating temperature was lowered by decreasing the Ti concentration in the alloy, but the effect of adding Cu was large and the limit was 40 ° C. Furthermore, it is difficult to process when the Ti concentration is reduced. Become. On the other hand, in the fifth to seventh alloys according to the example, the effect of adding Cu is smaller than that of the comparative example, and the operating temperature is remarkably lowered. Also, the workability has not deteriorated. Looking at the load difference between low temperature and high temperature, the first of the proportional examples shows that
Each of the third and sixth additive alloys indicates about 7 kg. From this result, the sixth alloy according to the embodiment makes it possible to shift the operating temperature to the low temperature side without losing its output effect, that is, the load difference between the low temperature and the high temperature. It is well known that the addition of Cu produces an output effect. Comparative Example 8 is an example showing that the workability deteriorates when Ti is less than 49 atomic percent, and Comparative Example 9 shows that the amount of V is 0.
If it is less than 5 and it is as low as 0.1, the operating temperature will exceed 30 ° C. In Example 10 and Comparative Example 11, if the amount of V is 3.0, the workability is also acceptable and the operating temperature is low. Can be achieved, but exceeds 3.0, and when it reaches 5.0, it is an example showing that the workability is extremely poor, Example 12 and Comparative Example 13
Is an example showing that if the amount of Cu is 20.0, the workability is also acceptable and a low operating temperature can be achieved, but if it exceeds 20.0 and becomes 25.0, the workability becomes extremely poor.Comparative Example 14 And 15 are examples showing that workability is good when the amount of Cu is 5 or less, but an operating temperature of 30 ° C. or more cannot be achieved. Example 16 shows that even when the amount of Cu is 15, This is an example showing that a material satisfying both the properties and the operating temperature can be obtained.

From the above example, Ti in the range of 49-50 atomic percent,
More than 5 atomic percent and up to 20 atomic percent Cu,
A shape memory alloy composed of V in the range of 5 to 3.0 atomic percent and the balance of Ni has excellent workability and an operating temperature of 30%.
It turns out that it is below ° C.

[Effects of the Invention] As described above, according to the present invention, excellent workability is achieved.
It is possible to obtain a shape memory spring that can operate at a temperature of 30 ° C. or less and has a large output, and can be applied not only to the spring but also to various industrial products such as clamps and fixing members.

[Brief description of the drawings]

FIG. 1 is a diagram showing a load temperature curve of a shape memory alloy according to an example of the present invention, FIG. 2 is a diagram showing a load temperature curve of a shape memory alloy according to a comparative example, and FIG. It is a figure showing a load temperature curve of a shape memory alloy concerning a comparative example.

Claims (2)

(57) [Claims] 1. The method according to claim 1, wherein Ti in the range of 49 to 50 atomic percent, Cu in excess of 5 at.
A shape memory alloy comprising V in the range of 3.0 atomic percent and the balance Ni. 2. Ti in the range of 49 to 50 at.%, Cu in excess of 5 at.
In a TiNiCuV alloy ingot consisting of V in the range of 3.0 atomic percent and the balance of Ni, homogenization treatment, hot working,
And performing a heat treatment at a temperature of substantially 425 ° C. for substantially one hour after the cold working.