JPS61127892A - Production of shape memory alloy element - Google Patents

Abstract

PURPOSE:To prolong the endurance life by putting an electrically conductive metallic layer on the surface of a shape memory alloy substrate and joining them together at a specified temp. so as to increase the adhesion of the metallic layer to the substrate. CONSTITUTION:A layer of an electrically conductive metal such as Cu or Ni is put on pat of the surface of a substrate of a shape memory alloy such as NiTi at one or more positions. The thickness of the metallic layer is <= about 5% of the minimum thickness of the substrate. They are joined together at >=400 deg.C in vacuum or in an inert or reducing gas to obtain a shape memory alloy element. The electrically conductive layer is not stripped by repeated shape restoring action, and the element maintains its stable characteristics for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a shape memory alloy element with improved layer density of a shape memory alloy surface (=metal layer provided).

[Technical background of the invention and its problems]

As in Shusho, the composition ratio is set appropriately (-Ni-T1
The Cu-based alloy and the Cu-based alloy have a shape memory function. Such shape memory alloys have the unique property of changing to the memorized shape when heated to a predetermined temperature.This unique property requires mechanical displacement. For example, it is effective (= can be used) for various actuators and switches.

By the way, a shape memory element (=
To perform a shape recovery operation (; means to apply heat to the shape memory element (= to return to the memorized shape (= to exceed the required reverse transformation point temperature, and to eliminate the rimata martensite) !degree 1; It is necessary to raise the temperature again, but this is a common method for raising the temperature. A method of heating υ using a heat source is adopted.In particular, the so-called energization heating method uses pulsed energization (=
Therefore, shape recovery control can be performed, which contributes to the simplification of the control system compared to the other methods C.

A conventional actuator that faces a shape memory substrate made of a shape memory alloy is activated by tracking heating (usually, electrodes are provided at both ends of the shape memory substrate.
During shape recovery control (-1) A torrent flow is applied to the entire shape memory element through these electrodes to generate Joule heating.

At this time, the current flowing through the shape memory base almost uniformly flows throughout the shape memory base. Therefore, Joule heat is also generated uniformly over the entire shape memory substrate, and shape recovery caused by this heat (= occurs uniformly (-) over the entire shape memory substrate. Actuator (
: If so, a method is adopted in which the temperature of the entire shape memory substrate is raised to if exceeding the reverse transformation point @ degree, and the entire shape memory substrate is instantaneously (=stepwise displaced when it is displaced to the memorized shape). ing.

However, as mentioned above (= conventional actuator that uses only stepwise displacement of the entire shape memory element (=
However, the drawback is that only one simple movement can be performed, and the usable range is significantly narrower. , or it is not possible to perform multiple types of complex movements.For this reason, there is a problem that the range of use is inevitably specified.One of the means to diversify the movements of shape memory alloys (-1 shape memory alloy) There is a method of providing a metal 4-hole Ii#'Y in the shape memory equivalence control part of the joint.In other words, the shape recovery control area (
=, 241J- is provided in advance by bonding, etc., and a magnetic current during proper heating is passed through the conductive dL layer, and the current flowing through the shape memory alloy is controlled to control the temperature rise in the shape recovery inhibition region. It is. Normally, in a shape memory element using a shape memory substrate, the speed of shape recovery 9t varies depending on the heating tray during magnetization, and if the voltage is constant, the smaller the current, the smaller the heat generation t. Therefore, the rate of temperature rise will be slower,
The time required for shape recovery is long, and the speed of recovery is also slow.

In addition, if the voltage applied to the shape memory alloy and the magnetic current flowing through it are very small, shape recovery will occur (required temperature (A
(point s), no displacement occurs due to shape recovery. In this way (=, shape recovery can be controlled by the voltage and magnetic current during energization.

However, this method has the drawback that the adhesion between the four whetstones and the shape memory alloy provided at = is not always sufficient, and the conductive layer peels off during repeated use. =NiT is often used in actuators, switches, etc. because it has excellent corrosion resistance and deterioration resistance.
The shape memory alloy had a thin oxide film formed on the surface, and its adhesion was poor, which was an obstacle to controlling the shape memory alloy with a conductive layer.

[Purpose of the invention]

The present invention was made in view of the above circumstances, and its purpose is to strongly strengthen the adhesion between the metal 4-layer, which is provided to partially control the shape memory alloy, and the shape memory alloy. To provide a method for manufacturing a shape memory alloy element, which improves the service life of a repeater.

[Summary of the invention-double]

The present invention provides a shape memory alloy made of a shape memory alloy that reverts to its memorized shape when heated to a predetermined temperature.1. is a 4-layer structure consisting of 41 layers of metal for partial control and a shape memory substrate provided on the surface of the substrate.
8! ! Targeting shape memory alloy elements with modified adhesion properties.

In such a shape memory alloy element, the present invention uses gold-14
After the layer is provided on the surface of the shape memory substrate, a bonding treatment is performed at a temperature of 400° C. or higher to improve the adhesion between the metal conductive layer and the shape memory substrate. Here, the bonding process is performed once at 4o
The reason for setting the temperature above o'c is that the temperature at which the metal conductive layer and the shape memory alloy diffuse and start bonding is around 400°C. Preferably at a temperature. Further, the treatment time may be shorter as the temperature increases, but when the treatment is performed at 600C, the treatment time may be 10 minutes or more.

Nine, the peeling of the metal conductor 41- from the entire shape memory substrate is as follows:
4 parts of metal groove QC shield and corner 1 of shape memory alloy element @
S (= Since this occurs a lot, this bonding process is suitable for metal conductivity
Particularly effective for shape memory alloy elements that have many edges, i.e., for partial control (=shape memory alloy elements that have metal conductive layers in multiple locations, and shape memory alloy elements that have corners) .

Furthermore, if the metal conductive layer is applied too thick, the financial strength of the attached conductive layer will affect the recovery power of the shape memory alloy, and complete shape recovery will not occur. It is necessary that the thickness of the shape memory substrate be 5% or less of the minimum thickness of the shape memory substrate.

Smooth - preferably 3 or less threads. Here, when the shape memory substrate is a wire rod (=, the minimum thickness is the diameter, and when the shape memory substrate is a plate material, it is determined by the plate thickness.

As the metal 1-, any metal may be used as long as it has a high tensile strength, but in the case where the target is partial control, copper, nickel, ordinary metal, aluminum, It is preferable to use TK6 or an alloy thereof. As the main stage for changing the 4-fly layer, any method can be used as long as it can be bonded to the surface of the shape memory alloy, such as Metsu-boshi, Spak, Fish-watch, mW, S-bonding, etc. Although it is different from fA-, considering the oxidation of shape memory alloys and 4@1-metals during processing, it is recommended to carry out the process in vacuum, in an inert gas such as argon or F, or in a reducing gas such as CoTK. I'm sorry. Furthermore, even in the -1 method, it is particularly desirable to set the pressure so that the pressure ratio is lower than 10-3 turr.

The shape memory alloy may be any alloy that has shape memory properties, but from the viewpoint of stability of properties, NlTi-based and Cu-based shape memory substrates are preferred; however, in order to achieve effective partial control; Shape memory alloys are preferred; in this case, the metal conductive layer (= copper and nickel are preferred from the viewpoint of diffusion and adhesion).

〔Effect of the invention〕

Shape memory metal elements 0 and C of the present invention improve the adhesion between the shield and the shape memory alloy in the metal grooves provided on the surface of the shape memory base, and prevent peeling of the conductive layer during repeated shape recovery operations. It is possible to maintain stable characteristics for a long time (= over a long period of time).

[Embodiments of the invention]

The shape memory element of the present invention will be explained in detail with reference to Examples below.

(Example 1) NLTi shape memory alloy poles with a diameter of 1 m and a length of 1000 + n, with a width of 250 rxtx at 2 locations at 250 mm intervals from one end of the shape memory alloy coil, which is shaped into a coil with a length of 50 + 11 blades. , electroplated with 20 μm thick copper and nickel. Then 350-900'
After performing the additive bonding process in step C, the valley plated portion was cut at the joint, and the bonding state in the vertical and cross sections was examined using an optical microscope. The results are shown in Table 1≦2.

Table 1 In addition, the first robe ×: The interface remains the same as after plating. Δ: Partially diffusion bonded ○: Complete (=diffusion bonding are shown respectively.

(Example 2) Among the shape memory coils of Example 1, 350'C and 6
A shape ratio 1 alloy coil which was bonded for each I minute at 00'C was stretched to a total length of 250 tax (: After being stretched by a twist bias spring, a DC voltage of 2V was applied to both ends of the coil for an extended period of time through the - wire. The coil was completely restored to its shape.

After cooling for 3 minutes, the coil was stretched again, and the above cycle was repeated 100 times.

:150"C shape memory alloy coil is 1
Plated 1i from 2 repeated repetitions! Peeling was observed at the edges and center (= peeling was observed, and with the number of repetitions (= peeling W & part) increased. After 18 repetitions, the edges were turned over, and after repeating n times, the plating layer near the center was peeled off. Cracks occurred, and as the number of repeats increased, the tail stream became unstable.

On the other hand, the plated portion of the shape memory alloy coil bonded at 600'C did not peel off at all even after 100 twists.

(Miho ψIJ3) A NiTi shape memory alloy wire with a diameter of 1 silk and a length of 1000B is divided into a coil with a diameter of 20mm and a length of 50cm (= shape memory alloy coil coil is divided into two parts at 250mm intervals from one end of the coil). 250, 5 μm thick, and 55 μm nickel
I felt nervous. Next, after 7QO"C and 30 minutes of bonding, the total length of the coil was reduced to 250JI using a bias spring.
After stretching, the coil was applied with a DC voltage of 2V for a few seconds to recover its shape, and the nickel-plated coil with a thickness of 5 μm completely recovered to its shape.
However, the coil with 55 μm thick nickel plating recovered to only about 85 inches. The shape recovery of the coil was repeated in a 10θ concave, but the plating thickness was 6 μm,
There was no peeling with the coil having a plating thickness of 55 μm.

Claims (2)

[Claims] (1) After providing a metal layer in at least one place on a part of the surface of a shape memory base made of a shape memory alloy that recovers its memorized shape when heated to a predetermined temperature,
A method for manufacturing a shape memory alloy element, characterized in that a bonding treatment is performed at a temperature of ℃ or higher. (2) The thickness of the metal layer is 5% of the minimum thickness of the shape memory substrate.
% or less, the method for manufacturing a shape memory alloy element according to claim 1.