JPS6056038A - Shape memory alloy and its production - Google Patents

Abstract

PURPOSE:To provide a shape memory alloy which has small transformation hysteresis of high-temp. phase low-temp. phase and has two-way memory characteristic by incorporating >=1 kind among Cu, Co and Fe at a prescribed ratio into a Ti-Ne shape memory alloy. CONSTITUTION:A Ti-Ni shape memory alloy incorporated with 0.05-10wt%, more preferably 0.08-5wt% >=1 kind among Cu, Co and Fe is prepd. Such shape memory alloy is then melted in an inert gas such as Ar and is then subjected to vacuum annealing and to a homogenizing treatment. The shape memory alloy after the homogenizing treatment is subjected to a soln. heat treatment at 500- 1,100 deg.C in the state of restraining or not restraining the same to a prescribed state and thereafter the alloy is quickly cooled by water, etc. The shape memory alloy after the quick cooling is subjected to an aging treatment in a temp. range of 200-700 deg.C in the state of restraining the same to the prescribed shape to be memorized. As a result, the shape memory alloy which has small transformation hysteresis of high-temp. phase low-temp. phase, more particularly high- temp. phase low-temp. phase transformation and has two-way memory characteristic is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides 'ri-Ni shape memory gold shape memory alloy: 1
After the alloy containing 0% by weight of Ou, Oo, and one or more iron is solution-treated with or without restraint in the predetermined shape to be memorized, it is subjected to a quenching treatment and then memorized. A shape memory alloy characterized in that the transformation between a high temperature phase and a low temperature phase, especially the transformation hysteresis from a high temperature phase to a low temperature phase, is small and bidirectional, by subjecting it to an aging treatment while being constrained to a predetermined shape. This relates to a manufacturing method.

It is known that most alloys that have a 0sO1 type body-centered cubic structure and undergo a thermoelastic martensitic transformation at high temperatures exhibit a shape memory effect. AL, 0u-At-1i1.0
u-Zn-Au, 0u-Zn-Ga, 0u-Zn-
anlou-Zn-81,0u-8n, Au-0d
, Ag-0d and other alloys have been found.

It is generally known that shape memory alloys do not exhibit shape memory effects unless they are single crystals, but Ti-Ni alloys are an exception; they are polycrystalline and have shape memory effects, making them extremely practical. Among the alloys mentioned above, it has been studied most extensively.

The shape memory effect occurs when a material that is in a martensitic state at a low temperature is deformed and then heated to return it to its original shape before deformation.The temperature at which this effect occurs is usually the alloy's reverse transformation start temperature (AB point), It is determined by the reverse transformation end fM degree (Ar point), the martensitic transformation start temperature (Ms point), and the martensitic transformation end temperature (Mf point), and the shape memory effect starts at the A8 point and ends at the Af point. .

The recovery power when producing this shape memory effect is 50 to 60 ky.
/ m*”, and studies are being conducted to utilize this resilience in various applied products.

A typical example of its application is an actuator that utilizes the reversible and repeated generation of a shape memory effect, as shown in FIG. This actuator is a combination of a regular coil spring (bias spring) made by Piasuka and a shape memory alloy coil spring, and at low temperatures the shape memory alloy is in a martensitic phase with a lower yield stress than the bias spring. At high temperatures, the bias spring is stronger and acts to deform the shape memory alloy, and 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 deforms the bias spring. It works like this.

In this case, the smaller the transformation hysteresis between the high temperature phase and the low temperature phase, and the more bidirectional the actuator 2 can easily operate in a small temperature range.

However, in conventional Ti-Ni alloys, only a unidirectional shape memory effect can be obtained, and the transformation hysteresis of high temperature phase = low temperature phase, especially high temperature phase → low temperature phase, is about 30°C.
Therefore, the temperature range in which the actuator operates by reversibly obtaining a low-temperature phase and a high-temperature phase must be increased.The operating temperature range is limited, and the bias spring combined with the shape memory alloy also has a large size. The drawback was that it required a large and strong material.

In order to improve these drawbacks, the present inventors have attempted to improve the Ti-Ni
0.05-10% by weight of Ou, Oo in thread shape memory alloy
and 50% alloy containing one or more types of iron.
The material should be memorized in the temperature range of 0°C to 1100°O. It should be solution-treated with or without restraint in a predetermined shape and then subjected to rapid cooling treatment, and then memorized in the 200° to -7° Mano temperature W range. It was discovered that aging treatment while constrained to a predetermined shape produces beneficial effects.

Next, the reason for limiting the content range of the additive element and the solution treatment/aging treatment temperature range in the present invention will be described.

When one or more of Ou, Oo, and iron are contained in an amount exceeding 10% by weight, hot workability and cold workability are significantly deteriorated, and processing becomes extremely difficult. Also, 0
．． If it is less than 0.05% by weight, sufficient small hysteresis and bidirectionality cannot be obtained, so the content is limited to 0.05 to 10% by weight. Note that from the viewpoint of balance between shape memory properties, hot and cold workability, etc., a range of 0.08-'7% by weight is preferable, and a range of α0EF-6% by weight is more preferable.

Next, regarding melting temperature, no sufficient effect is observed at 500°C, and when it exceeds 1100°0, loss of T1 element due to thermal melting becomes a problem. Based on the above considerations, the temperature range was limited to 100°C for 50CPC.

In this case, the same effect can be observed whether or not the alloy is constrained to a predetermined shape to be memorized.

Further, regarding the aging treatment temperature, no sufficient effect is observed when 200 CO is not added, and when it exceeds '70 (I'd), the deterioration of shape memory properties (recovery rate, recovery power) becomes noticeable.

From the above point of view, the temperature range was limited to 2ONO(6).

In this case, it is necessary to constrain the alloy to a predetermined shape in order to make the alloy memorize the predetermined shape.

The present invention will be explained below based on examples.

Various alloys as shown in Table 1 were arc melted in argon, vacuum annealed at 1000 CO for 2 hours for homogenization, and then hot rolled in Boo-e oCPO. It was made into a thick plate. 50 pieces of this board
Solution treatment was carried out for 3 hours at various temperatures ranging from 0 to 1100°C, followed by water cooling. In the table, sample A l = Al.

is the alloy of the present invention.

Next, as shown in Figure 2, the sample was wrapped around the inner surface of a stainless steel pipe with an inner diameter of 40φ and restrained with Ni#.
- Determining the degree of bidirectionality and the transformation point using differential scanning calorimetry (DSO) of the latter samples aged for 10 hours at various temperatures in the range of 7030 - 2000 - high temperature phase →
Transformation hysteresis of the low temperature phase (intermediate phase) was confirmed.

The results are shown in Table 1 in comparison with conventional Ti--Ni alloys.

The degree of bidirectionality was determined by the degree to which the sample took on a constrained shape when heated and spontaneously tried to take on a straight-stretched shape when cooled, as shown in FIG.

It is clear from Table 1 that the alloy of the present invention has bidirectional properties and that the transformation hysteresis from high temperature phase to low temperature phase (intermediate phase) is extremely small.Table 1 (Jllfii%)

[Brief explanation of drawings]

FIG. 1 shows an actuator using a shape memory alloy. In the figure, 1 indicates a normal coil spring, and 2 indicates a shape memory alloy coil spring. FIG. 2 shows the restrained state of the sample. In the figure, 1 is a stainless steel pipe with an inner diameter of 40φ, 2 is a shape memory alloy, and 3 is NiM wrapped around the sample to restrain it. Figure 3 □0 shows the constrained shape of the sample, and (c) and (c) show the state in which the sample spontaneously assumes a straight-stretched shape upon cooling.

Claims (1)

[Claims] L Ti-Ni type, shape memory alloy with α05-10% by weight
Ou. A shape memory effect containing one or more types of 00 and iron, characterized in that the transformation hysteresis of the high temperature phase=low temperature phase is small and bidirectional. & α05-10% by weight of O in Ti-Ni shape memory alloy. 00 and an alloy containing one or more types of iron is subjected to solution treatment in a temperature range of 5OCR 3 to 1100°C in a state in which it is constrained to a predetermined shape to be memorized or in an unconstrained state, and then subjected to a rapid cooling treatment. , then 200 force ~ 7
A method for producing a shape memory alloy, characterized in that an aging treatment is performed in a temperature range of 00° C. while the shape is constrained to a predetermined shape to be memorized.