JPS60169552A - Manufacture of shape memory alloy - Google Patents

Abstract

PURPOSE:To reduce the hysteresis of transformation of a shape memory Ti-Ni alloy from a high temp. phase to a low temp. phase by subjecting the Ti-Ni alloy contg. Ni in excess and having TiNi and TiNi3 phases to soln. heat treatment and aging each at a specified temp. CONSTITUTION:A shape memory Ti-Ni alloy contg. Ni in excess and having TiNi and TiNi3 phases is worked and constrained to a prescribed shape to be memorized. The alloy is then subjected to soln. heat treatment at 500-1,100 deg.C, quenching and aging at 200-700 deg.C. Working, soln. heat treatment, constraint and aging, or working, soln. heat treatment, aging, constraint and memory treatment may be carried out in order. By the soln. heat treatment and aging, supersatd. Ni is precipitated as TiNi3 grains, so the hysteresis of transformation from a high temp. phase to a low temp. phase is extremely reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a Ti-N1 shape memory alloy with a Ni-excessive composition having two phases of 'L'iN+ phase and TiNi3 phase.
Solution treatment in the temperature range of ~1100°C and 200°C ~
The present invention relates to a method for producing a Ti--Ni shape memory alloy, characterized in that a shape memory alloy having an extremely small transformation hysteresis from a high temperature phase to a low temperature phase is obtained by aging treatment in a temperature range of 700°C.

Ni-based shape memory alloys exhibit a remarkable shape memory effect and have excellent mechanical properties, corrosion resistance, etc., and are therefore being studied in the widest range for practical use.

The shape memory effect occurs when a material that is in a martensitic state at low temperatures is deformed and then returns to its original shape when heated.
, point), the end temperature of reverse transformation (Ar point), the start temperature of martensitic transformation (point A, s), and the start temperature of martensitic transformation (point Mr), and the shape memory effect starts at point A3 and at point Ar. It ends. The recovery power when producing this shape memory effect is 50 to 601c9/
It has a recovery power of up to 'II+7'l, and studies are being made to utilize this resilience in various applied products. A typical example of its application is an actuator that utilizes the repeated generation of a shape memory effect, as shown in FIG. Actuator spring with normal coil spring (
A bias spring is a combination of a shape memory alloy coil spring (bias spring) and a shape memory alloy coil spring.At low temperatures, the shape memory alloy is in a martensitic phase state with a lower yield stress than the bias spring, so the bias spring is stronger and has a shape memory alloy. Conversely, at high temperatures, the shape memory alloy enters a β-phase state with a higher yield stress than the bias spring, and the shape memory alloy operates to deform the bias spring.

In this case, the smaller the transformation hysteresis from the high temperature phase to the low temperature phase, the easier it is to operate as an actuator in a small temperature range.

However, in conventional IlliN-based alloys, high-temperature phase →
The transformation hysteresis of the low-temperature phase is as high as about 30°C, so the temperature range in which the actuator is operated by reversibly obtaining the low-temperature sum and high-temperature phase must be widened.
There was a drawback that the range of 111 degrees was limited.

From this point of view, the present inventors sought to obtain an alloy with a low transformation histology (7'IJ) from the high-temperature phase to the low-temperature phase, which facilitates the operation of the Akbu uniter as shown in Figure 1.
'I'1-Ni-based shape memory alloy with N1-excess composition having two phases: t, N, phase and "?INrs phase" It was found that no beneficial effects were obtained when the treatment described in the shape memory alloy range was applied. That is, by solution treatment and aging treatment, supersaturated Ni becomes '1''INi3 particles and precipitates in the matrix, and along with this, mesophase transformation is introduced, and the transformation occurs in two stages. The transformation from high temperature phase to low temperature phase (intermediate phase) becomes very small.

Next, the reasons for limiting the processing conditions in the present invention will be described.

Regarding the solution treatment temperature, T is less than 500'C.
The sufficient solid solubility of TiNi3 in the 1Ni matrix is r
If you think of it as something that doesn't affect you, its effects are not fully recognized. Moreover, when the temperature exceeds 1100°C, loss of the '1'1 element due to oxidation becomes a problem. 500-110 from the above point of view
The temperature range was limited to 0°C.

Regarding the degree of aging treatment, sufficient precipitation of I'1Ni3 particles does not occur at temperatures below 200'C, and at temperatures below 700'C.
If the temperature exceeds , intermediate phase transformation cannot be introduced, and a high temperature phase occurs.
Small hysteresis due to low-temperature summation (intermediate phase) transformation cannot be obtained. From the above point of view, the temperature range was limited to 200 to 700°C.

Regarding the Kiden treatment temperature, at temperatures exceeding 700'C, the shape memory effect deteriorates, and small hysteresis due to medium (HJ phase transformation disappears and high temperature phase -) low temperature summation (intermediate phase) transformation occurs. . From the above point of view, the temperature range was limited to 700°C or less.

4. Is there a predetermined shape that should be memorized before solution treatment and aging treatment? It is possible to memorize the shape from ζ, so there is no need for memory processing.
Or, if the person is to be restrained after the statute of limitations has passed, amnestic processing is required. With regard to the timing of constraint to a predetermined shape to be memorized, good results can be obtained regardless of the timing set forth in the claims.

The present invention will be explained below based on examples.

[Example 1] A Ti-50,7'7'%Ni alloy with a Ni-excessive composition having two phases of Ill, N, phase and 'l'iNi3 phase was melted by high frequency induction at 1000°C for 2 hours in 7141 vacuum. It was annealed and homogenized, and then forged at 900°C to obtain a φ12 bar. This rod was further hot-worked and cold-worked to form a wire of φ1. Next, set this line to
800℃ after being formed into a coil spring as shown in the figure and restrained.
At 2 o'clock 1i, JJ solution treatment was also performed and further heated to 400℃.
After aging for 5 hours, the displacement-temperature curve was measured and the transformation point was measured using a W scanning calorimeter (DSC) to determine the transformation hysteresis of the high temperature phase -> low temperature phase (intermediate phase) 6: confirmed.

FIG. 2 shows the measurement results of the transformation point by DSC after the aging treatment in Example 1. In conventional alloys, one DSC peak due to the transformation of the low-temperature phase J high-temperature phase is observed during heating and one during cooling, whereas in the alloy produced by the method of the present invention, an intermediate phase transformation is introduced, and the DSC peaks are observed at each time during heating and cooling. 2
It has one peak after another. Along with this, the peak during cooling starts at almost the same temperature as the transformation end temperature during heating, and the transformation hysteresis from the high temperature phase to the low temperature phase (intermediate phase) becomes almost 0°C. Further, FIG. 6 shows a displacement-temperature curve when a constant load is applied to the coil spring of Example 1 by a weight, and it is clear that the hysteresis is extremely small compared to the conventional material. For comparison, the transformation point measurement results by I)SC and the displacement +7iA degree curve of conventional H are shown in FIGS. 4 and 5.

[Example 2'J'11. "i-51, Qa, t% tooth metal alloy After forming a wire of φ1 in the same manner as in Example 1,
A time solution treatment was performed. Next, it was molded into a coil spring by the same method as in Example 1 and restrained, and then heated to 50'C.
Aging treatment was performed for 2 hours at . FIG. 6 shows the measurement results of the transformation point by DSC after the aging treatment in Example 2.

As is clear from the figure, intermediate phase transformation is observed, and along with this, the transformation hysteresis from high temperature phase to low temperature phase (intermediate phase) has a very small value of about 2°C. In this case, the two peaks during heating overlap at approximately the same temperature due to the influence of the crystallinity of the aging treatment. In addition, Fig. 7 shows the displacement -717, ros (curve) when a constant load is applied to the coil spring of Example 2 by a weight, and it is clear that an extremely good θf hysteresis has been obtained compared to the conventional material. .

[Example]

A Ti-51,2at N+ alloy was made into a wire of φ1 in the same manner as in Example 1, and then solution-treated at 900° C. for 2 hours. Next, aging treatment at 400℃ for 10 hours J! I'! After applying , it was formed into a coil spring and restrained by the same method as in Example 1, and was further subjected to the treatments described in 1 and 3 at 400°G for 30 minutes. The transformation hysteresis from high-temperature phase to low-temperature phase (intermediate phase) when

As described in the examples above, the alloy according to the present invention has extremely small transformation hysteresis from high temperature phase to low temperature phase (rlj to a) compared to conventional alloys, and significantly limits the operating temperature range when used in actuators etc. It is extremely beneficial as it both relaxes and enhances thermal responsiveness.

[Brief explanation of drawings]

Figure 1 shows an actuator using a shape memory alloy, Figure 2 shows the I) SC transformation point measurement results for the alloy of Example 10, and Figure 3 shows the displacement-temperature curve of the coil spring of Example 1. Figure 4 shows the transformation point measurement results of the conventional alloy by I>SC, Figure 5 shows the displacement-temperature curve of the conventional alloy, and Figure 6 shows the transformation point of the Example 20 alloy by DSC. FIG. 7 is a diagram showing the displacement-temperature curve of the coil spring of Example 2. 1゛Coil spring, 2゛Shape memory alloy coil spring. Applicant: Hitachi Metals, Ltd. Figure 1 Broom 2 Figure 3 Figure 4
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RO)rangenO,)lIYl'fX:? X(1), J: Sea urchin] iEzuru. [-↓In a Ti-Ni thread shape memory alloy with a two-phase gap of T1Ni phase and TiN1s phase and a N1-excess composition, the memorized shape after processing is constrained to a constant shape, and then 50
0~J, ], 1lrX Doga 1 at 0°C. After solution treatment in
A method for producing a shape memory alloy, characterized in that aging treatment is performed in a temperature range of 0.000C. Ni over-piercing with Z'I'jN1 phase and TiNi3 phase θjini interplay (in the formed ゛L'j-Nl thread shape memory alloy, after processing!i0C)'': 1.IOO''Q cleaning 1 degree range After solution treatment at
7. A method for manufacturing a shape memory alloy, comprising: performing aging treatment β11 in a temperature range of 0°C. 3. T1Ni phase and TiN1s phase
After processing, a Ti-Ni thread shape memory alloy with an N1 overspill composition was subjected to solution treatment in a temperature range of 500 to 110 (1'C), followed by rapid cooling treatment, and then aging treatment in a temperature range of 20 to 700C. A method for manufacturing a shape memory alloy, which is characterized in that the shape memory alloy is restrained in a predetermined shape to be memorized after applying the shape memory alloy, and then further subjected to two memory treatments in a temperature range of 700°C or less.-1

Claims (1)

[Claims] IT1Ni phase and 'I1. 'i-Ni type shape memory gold shape memory alloy with Ni excess composition having two phases of 5 phases, restrained to a predetermined shape to be memorized after processing, and then 50
Method for manufacturing a shape memory alloy 2']' iNi phase and 'In a Ni-excessive composition Ill,N,-based shape memory alloy with two phases of piNi3 phase,
After processing, the material is subjected to solution treatment in a temperature range of 500 to 1100 degrees Celsius, followed by rapid cooling treatment, then constrained to a predetermined shape to be memorized, and then further subjected to aging treatment in a temperature range of 200 to 700 degrees Celsius. Method for producing shape memory alloy 5'1. After processing, a Ti-Ni shape memory alloy with an Ni-excess composition having two phases of 'iNi phase and J, 'iNi5 phase is subjected to solution treatment in a temperature range of 500 to 1100 °C, followed by rapid cooling treatment, and then quenching treatment is performed at a temperature range of 200 to A method for manufacturing a shape memory alloy, which comprises subjecting the alloy to an aging treatment in a temperature range of 700°C, constraining it to a predetermined shape to be memorized, and then further performing a memory treatment in a temperature range of 700°C or less.