JPH06128709A - Thermomechanical treatment for shape memory alloy and shape memory alloy member - Google Patents

Abstract

PURPOSE:To provide a shape under constraint, as a shape at a martensitic-phase temp., by applying shape memory treatment and constraining heat treatment to a member made of shape memory alloy consisting of specific percentages of Ni, Cu, and Ti under respectively specified conditions. CONSTITUTION:Shape memory treatment (length, L0), consisting of heating up to 400-650 deg.C for 0.5-120min, is applied to a member made of a shape memory alloy having a composition consisting of, by weight, 45-50% Ni, 5-12% Cu, and the balance Ti. Further, this member is subjected to constraining heat treatment consisting of heating in a state under constraint (length, L1) up to a temp. exceeding the transformation heat treatment temp. and cooling in the constrained state. By this method, a shape under constraint (length, L2) can be provided as a shape at a martensitic-phase temp., and the recovery when this member is heated up to a temp. not lower than the transformation temp. can take the value of (L0-L2) as working distance.

Description

Detailed Description of the Invention

[0001]

The present invention relates to NiTiX (X = C
(u, Cr, Fe, Co, Mo, V, Pd) Shape memory alloy thermomechanical processing method, and shape memory alloy member processed by the method.

[0002]

2. Description of the Related Art As is well known, shape memory alloys exhibit the property of being flexible in the martensite phase (low temperature) and being hard in the matrix phase (high temperature), and remembering the shape stored at high temperatures, Even if a deformation is given in the martensite phase, when it is heated above the transformation temperature (Af temperature) determined by the alloy composition, the original shape that has been memorized is restored.

Utilizing this performance, it can be made to function as a temperature sensor, and it can also be made to function as an actuator by utilizing the recovery force when recovering the stored shape. NiT is a practical shape memory alloy
i-based and NiTiX-based. As an actuator, it is usually used in the form of a coil spring.

However, when a coil spring is manufactured from a conventionally known shape memory alloy, even if the coil spring is deformed at a high temperature or a low temperature, spring back is inevitably generated, so that a desired shape (for example, after deformation) is obtained. It was extremely difficult to achieve the coil height).

Further, the relative magnitude of the displacement realized when returning to the original shape has its own limit in the conventional shape memory alloy member. This is inconvenient for applications in which the recovery force may be small but the displacement is large.

FIG. 1 shows these relationships. The coil spring is set as shown in the first stage (length l ₀ ) and the shape is memorized by heating it. Even if the material is restrained as shown in the step (length l ₁ ) and deformed, if the restraining force is released, springback occurs as shown in the third step (length l ₂ ) and the shape of the restrained state is not given. No, and even if this is heated to Af temperature or higher and returned to the memorized shape as in the fourth stage, the working distance of the actuator using this coil spring can be only l ₀ -l ₂ .

[0007]

An object of the present invention is to eliminate the above-mentioned problems in shape memory alloys and to heat-process a shape memory alloy capable of giving an arbitrary shape in the martensite phase (low temperature). It is another object of the present invention to provide a method, and also to provide a shape memory alloy member which has a shape that is accurately approximated to a desired shape, and therefore can set the recovery amount with high accuracy.

With respect to an actuator using a member having a typical shape of a coil spring, it is also an object of the present invention to realize an actuator having a relatively large working distance in addition to making the working distance highly accurate. Be done.

[0009]

The method of thermomechanical processing of a shape memory alloy according to the present invention is a shape memory alloy comprising Ni: 45 to 50% (weight%, hereinafter the same), Cu: 5 to 12%, and the balance Ti. 0.5 ~ to the temperature of 400 ~ 650 ℃
A shape memory treatment is performed by heating for 120 minutes, and a constraint heat treatment is performed in which the member is constrained and heated to a temperature exceeding the transformation temperature and cooled while constrained, so that the shape at the martensite phase temperature is constrained. It is characterized by giving a shape.

The shape memory alloy member of the present invention is Ni: 45.
A shape memory alloy member composed of ˜50% (weight%, the same hereinafter), Cu: 5 to 12%, and the balance Ti, characterized by being given a shape in a restrained state by shape memory treatment and restraint heat treatment. To do.

As the composition of the shape memory alloy, a part of Ni and / or Ti among the above components is Cr, Fe, C.
One or more of o, Mo, V and Pd 0.1 to 0.1
Substitutions with 5.0% can be used as well.
The substitution by the elements below Cr is not limited to the transformation temperature (Af
Has the effect of lowering the point.

[0012]

FUNCTION The alloy composition itself of the shape memory alloy used in the present invention is known. In NiTiCu based alloy,
Ni: 45 to 50% is indispensable for exhibiting shape memory performance.

If Cu is not added in an amount of 5% or more, the effect intended by the present invention cannot be obtained. On the other hand, the presence of more than 12% reduces workability and makes it difficult to form a coil spring or the like.

Cr, Fe, Co, Mo, V and Pd
Is 0.1% in order to clearly obtain the effect of lowering the transformation temperature.
The above addition is required. However, if the transformation temperature is lowered too much, the shape memory property will not be exhibited in the normal temperature region, and it is better not to add too much in order to maintain the workability.
An upper limit of 0% was set.

When the restraint heat treatment following the shape memory treatment is performed according to the present invention, any shape can be given at the martensite phase temperature. This pattern is as shown in FIG. 2. The first stage shows the shape memory processing similar to that of FIG. 1, but the second stage shows the restraint heat treatment peculiar to the present invention, and as a result, shown in the third stage. As described above, the coil spring after being released from the constraint maintains the shape at the time of the constraint. The recovery when this is heated to the transformation temperature or higher is as shown in the fourth stage, so the working distance is L ₀ −.
L ₂ (> l ₀ −l ₂ ) can be taken.

[0016]

Example: Ni: 46.8%, Cu: 8.3%, balance T
A shape memory alloy having a composition of i was prepared and drawn to a diameter of 1.0 mm. This was wound on a coil having an inner diameter of 15.0 mm and 7 effective turns. The free height of the coil is 30.0 mm.

This coil was heated at 440 ° C. for 30 minutes to perform shape memory to the above free height of 30.0 mm.

Subsequently, the coil was constrained in a form compressed to a height of 10.0 mm, heated at 90 ° C. for 1 minute, and constrained heat treatment was performed to cool it to room temperature. When released from restraint, virtually no springback was observed.

With respect to the coil spring which has been subjected to the above processing, 0
The force generated by the coil spring was measured by applying a temperature change of heating from 90 ° C to 90 ° C and returning from 90 ° C to 0 ° C. The relationship between temperature and generated force is as shown in the graph of FIG.

[0020]

According to the heat treatment method of the present invention, NiTi
An arbitrary shape can be given to the member of the Cu-based shape memory alloy in the martensite phase. Therefore, the shape memory alloy member of the present invention obtained by this heat treatment method has a precise free length in terms of a coil spring, and the recovery amount can also be set accurately. As an actuator, it is possible to manufacture an actuator having a high working distance and a large working distance with a small recovery force.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a length of a coil spring from a shape memory treatment to a deformation at a martensite phase to a recovery at a high temperature for a conventional shape memory alloy member.

FIG. 2 shows the relationship between the process of heat treatment and the length of the coil spring for the shape memory alloy member according to the present invention,
The figure corresponding to FIG.

FIG. 3 is a graph showing the relationship between the force generated by the coil spring and the temperature obtained in the example of the present invention.

Claims (5)

[Claims] 1. A shape memory alloy member composed of Ni: 45 to 50% (weight%, the same applies hereinafter), Cu: 5 to 12% and the balance Ti: 0.5 to 1 at a temperature of 400 to 650 ° C.
A shape-memory treatment of heating for 20 minutes is performed, and a constraint heat treatment of heating to a temperature above the transformation temperature in a state of restraining the member and cooling while restrained is performed, whereby the shape at the martensite phase temperature is restrained. A thermomechanical processing method for a shape memory alloy, which is characterized by giving a shape. 2. A shape memory alloy consisting of Ni: 45 to 50% (weight%, the same applies hereinafter), Cu: 5 to 12%, and the balance Ti, and a part of Ni and / or Ti is Cr, Fe, C.
One or more of o, Mo, V and Pd 0.1 to 0.1
400-650 for alloy members replaced with 5.0%
The martensite phase is subjected to a shape memory treatment of heating at a temperature of 0.5 ° C. for 0.5 to 120 minutes, and further to a restraining heat treatment of heating the member to a temperature above the transformation temperature in a restrained state and cooling while restrained. A method for thermomechanical processing of a shape memory alloy, characterized in that a shape in a restrained state is given as a shape at temperature. 3. A shape memory alloy member comprising Ni: 45 to 50% (weight%, the same applies hereinafter), Cu: 5 to 12%, and the balance Ti, the shape being in a restrained state by shape memory treatment and restraint heat treatment. A shape memory alloy member characterized by being given. 4. A shape memory alloy consisting of Ni: 45 to 50% (weight%, the same applies hereinafter), Cu: 5 to 12%, and the balance Ti, and a part of Ni and (or) Ti is Cr, Fe, C.
One or more of o, Mo, V and Pd 0.1 to 0.1
A shape memory alloy member, which is an alloy member replaced by 5.0% and is given a shape in a constrained state by shape memory treatment and restraint heat treatment. 5. The shape memory alloy member according to claim 3, which has the shape of a coil spring.