JPH02221342A - Copper-series shape memory alloy - Google Patents

Abstract

PURPOSE:To improve the workability and shape memory properties of the shape memory alloy by incorporating a trace amt. of misch metal into a Cu-Al- Zn-Mn alloy having specified compsn. CONSTITUTION:The compsn. of the shape memory alloy is formed with, by weight, 2 to 14% Al, 1 to 10% Zn, 1 to 10% Mn, 0.005 to 0.5% misch metal and the balance Cu. By this compsn., the crystal grains in a beta single phase of the alloy are refined and the crystal anisotropy of the alloy is relaxed to improve the workability. Together with this, the amt. of critical introducing strain (the amt. of shape memory to be treated) is improved. Furthermore, the control of the transformation temp. is facilitated without requiring complicated heat treatment.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides Cu-Aj! This invention relates to an improvement of a -Zn-Mn alloy, and relates to a copper-based shape memory alloy in which Mitshu metal is added to improve workability and shape memory properties.

[Conventional technology and its issues]

Cu-Aj! -Zn-Mn alloy has β→α+T!, which is considered to be a practical problem with copper-based shape memory alloys. This is a practical alloy that achieves stress relaxation through eutectoid decomposition.

However, the β phase, which contributes to the shape characteristics, has a large crystal anisotropy, so it has poor workability during cold working, and there is also the problem that the critical amount of introduced strain, which affects the memory capacity, cannot be increased. Therefore, in order to solve the problem of poor workability caused by the crystal anisotropy of the β phase, it has been considered to make up for it by making the crystal grains finer. This method involves finely dispersing intermetallic compounds by adding Tt, B, Zr, Fe, etc. However, the shape memory phase is a β phase (the rz phase also transforms, but it is brittle, so the presence of the T□ phase is difficult to process). In addition, complex heat treatment is required to create an α-10β phase structure for miniaturization, and it is practically useful because only the strain added to the β phase exhibits shape memory changes. In addition, in the method of dispersing intermetallic compounds by adding a third element, the transformation temperature, which is a shape memory characteristic value, greatly depends on the amounts of Al, Zn, and Mn, so it is difficult to disperse intermetallic compounds by adding a third element. If this occurs, these main components will be consumed, making it difficult to control the transformation temperature.

Furthermore, if an intermetallic compound is present, there are various problems such as, for example, layered dispersion along the extruded structure imparts anisotropy to the material.

[Invention tries to solve! 11J! As a result of studies on the above-mentioned problems, the present invention has improved memory properties by improving cold workability and critical introduced strain by refining the β-phase single-phase crystal grains in a Cu-An-Zn-Mn alloy. This is a copper-based shape memory base developed using 9-karat gold.

[Means and effects for solving the problem] The present invention has the following features:
j! 2-14wt%, Zn1-10wt%, Mnl-1
0wL% and Mitsushmetal 0.005-0.5wL
% and the balance is Cu.

That is, the present invention applies to conventionally known Cu-An! -Zn-Mn
By adding a small amount of Mitshu metal to the copper-based shape memory alloy,
By refining the crystal grains of the single beta phase of the alloy, the crystal anisotropy of the alloy is relaxed, resulting in improved workability and a copper-based shape that improves the amount of shape memory processing (limit amount of introduced strain). A memory alloy was obtained.

However, in the present invention, the amount of Al, Zn, and Mn is limited as described above because Al % Z n s M n
Each amount affects the transformation temperature of the shape memory alloy, and if it is less than or exceeds the above range, the required transformation temperature of -150°C to 300°C cannot be obtained. . The base amount of Cu is 65-8
A range of 5-t% is suitable, and as the amount of Cu increases, the transformation temperature also increases. Also, the amount of Mitsushmetal is Q, OO5
The reason for setting the value to 0.5 wt% is that if it is less than 0.6005 wt%, the effect of refining crystal grains is insufficient, so 0.5 wt%
This is because if it exceeds this, defects such as cracks will occur during processing such as forging. It is preferable that the Mitsushi metal used in the present invention is mainly composed of Ce and contains 99.7% or more of rare earth elements such as La, Pr, and Nd.

The alloy of the present invention can be processed by hot forging, hot extrusion, cold working, etc. after casting, like ordinary copper-based shape memory alloys, and can be machined into desired shapes such as couplings. , shape memory treatment is applied to the product.

As described above, the present invention adds a small amount of Mitshu metal to a Cu-Al2-Zn-Mn based copper shape memory alloy to refine the crystal grains of the single β phase of the alloy, thereby improving cold workability and limiting introduced strain. This is an improved version of the conventional α+
This method does not require complicated heat treatment, unlike the method of finely distributing the β phase or finely dispersing intermetallic compounds, and the transformation temperature can be easily controlled.

〔Example〕

An embodiment of the present invention will be described below.

Aj! lO, 0wt%, Mn5.0wt%, Zn4.0
An ingot having a diameter of 250 aφ and a length of 500 cm and having a composition shown in Table 1 and containing a base material of 0.005 to 1.015 wt % of Mitshu metal in the base material with a balance of Cu and a balance of Cu was cast. The characteristics of the ingot structure and grain size of this ingot were investigated. The results are shown in Table 1.

As is clear from Table 1, as the amount of Mische metal increases, the effect of refining the crystal grains becomes more significant.
When added, the amount becomes about 1/10 of that of the material without additives. As the amount increased, the miniaturization progressed, but 1. If the ingot is about Owt%, cracks occur inside the ingot.

Next, the above ingot was heated to 700"C after external cutting, and the diameter was 30".
After hot extrusion and air cooling, the outer diameter is 28mm by machining.
A ring-shaped sample with a diameter of 20 mm and a thickness of 5 mm was prepared.

This sample was annealed at 400° C. for 20 minutes to undergo shape memory treatment. Here, a strain introduction test was performed by initially applying an expansion of 5%, and the critical amount of strain was investigated. The maximum value and average value of the critical strain amount were determined.

The results are shown in Table 2, and the test was conducted on 10 samples for each sample number.

As is clear from Table 2, since the Mische metal-free material had a large recrystallized grain size, cracking occurred in all the samples even in the initial test (5% strain). On the other hand, the Mische metal additive material showed an average strain of 5% or more, indicating that the workability was significantly improved. However, for the ingots with about 1wt% addition, although the maximum strain was large, many of them fractured at low strain, and the average value was low.The reason for this is thought to be that internal cracks in the ingot remained microscopically even after processing. .

Through the above tests, Mitsushmetal was evaluated as o, o o s~
The material containing 0.5 wt% has a sound casting structure, making it possible to obtain fine recrystallized grains through a simple process, and therefore making it possible to introduce an average strain of 5% or more through shape memory treatment. Note that when the above samples were heated to a temperature higher than the reverse transformation temperature and the amount of shape restoration was measured, all values showed a value of 100%.

〔effect〕

As explained above, according to the present invention, it is possible to obtain a copper-based shape memory alloy that has fine crystal grains, alleviates the crystal anisotropy of the alloy, improves workability, and improves the critical amount of introduced strain. It has a remarkable industrial effect.

Claims (1)

[Claims] Al2-14wt%, Zn1-10wt%, Mn1-1
0wt%, and misch metal 0.005~0.5w
A copper-based shape memory alloy containing t% and the balance being Cu.