JPH03107444A - Manufacture of cu-al-ni series shape memory alloy - Google Patents

Abstract

PURPOSE:To simultaneously execute extruding and storing treatment of the extruded shape in the shape memory alloy by extruding a Cu-Al-Ni series shape memory alloy in a specified temp. range and thereafter immediately subjecting it to rapid cooling. CONSTITUTION:At the time of defining the beta solid soln. transformation temp. in a Cu-Al-Ni series shape memory alloy as Tbeta and the melting starting temp. in the alloy as Tm, the ingot of the alloy is extruded, e.g. into the shape of a wire at T deg.C, the temp. in the range satisfying Tbeta-100 deg.C<=T<=Tm-50 deg.C and is thereafter immediately subjected to rapid cooling by a water cooling method or the like. The shape memory alloy excellent in extrudability and straightness and in which the shape in a linear state free from curling caused by rolling is correctly stored can efficiently be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for simultaneously performing hot extrusion of a Cu-Al-Ni based shape memory alloy and memorization treatment of the extruded shape.

[Prior art] Copper-based shape memory alloys include T, which is currently widely used.
Compared to i-Ni shape memory alloys, it is inferior in terms of repeated operation and durability, but it is low cost, has a wide range of operating temperatures,
In addition, it surpasses T1Ni-based shape memory alloys in terms of two-way operation and the like. Copper-based shape memory alloys include Cu-Zn-Al, which is already in practical use, and Cu.
-Al-Ni system, Cu-Δ1-Be system, Cu-At-M
n-based and Cu-A1-Fe-based alloys have been proposed, but Cu-At-Ni-based alloys are particularly promising among copper-based alloys in terms of thermal stability (heat resistance) and shape memory performance. is large. However, this alloy system has extremely coarse grains and extremely poor workability, so it has been considered extremely difficult to put it into practical use.

For example, even in hot swage processing, the limit is about 2 mmφ, and wire breakage often occurs during subsequent wire drawing and rolling.

Therefore, the present inventors developed a method to improve workability by blending Ti to refine the crystal grains (Japanese Unexamined Patent Publication No. 167737/1982), or improved shape memory properties. In order to improve workability while maintaining the same, Mn was newly added to develop a five-element alloy (Japanese Patent Application Laid-Open No. 1983-1999).
Publication No. 3064).

[Problems to be Solved by the Invention] However, even with these alloys, cold working is not possible in an industrial sense, and there are problems as described below. In other words, ■Due to extremely high deformation resistance at low temperatures, there are many wire breakage accidents in areas with small diameters, which increases production costs.■Curling is significant and quality is unstable (most commonly used wires). (When forming into a coil spring shape, a straight strand without curling is desired.) ■Since it is a functional material, a production system that can meet the needs of users who produce a wide variety of products in small quantities is required.This invention This was done in consideration of this situation, and we conducted research to establish a manufacturing technology that could overcome the drawbacks of (2) and (3) above and meet the request (2), leading to the completion of the present invention. Ta.

[Means for Solving the Problems] The main point of the manufacturing technology according to the present invention is that the Cu-Al-Ni shape memory alloy Tβ-100°C≦T≦Tm-50°C (here, Tβ is the β solid solution transformation temperature, Extrusion is carried out in a temperature range of (Tm means melting start temperature) and quenching is performed immediately after extrusion to perform extrusion molding and a process for memorizing the extruded shape at the same time.

[Operation] The shape memory effect is caused by martensitic transformation and reverse transformation occurring reversibly with heating and cooling. At this time, in copper-based alloys, the parent phase that undergoes martensitic transformation needs to become a β solid solution phase, so in order to obtain the shape memory effect, heat treatment (so-called memory treatment) is necessary to rapidly cool the alloy from the temperature range where the β phase exists. In conventional memory processing, the material is fixed in a desired shape by molding, then reheated to a high temperature above the β phase region, and then rapidly cooled.

By the way, in order to obtain a good shape memory effect, the matrix β
It is said that it is necessary that the phase has a recrystallized structure.

In this regard, in the conventional memory processing method described above, since the material is reheated to the β phase region after completion of molding, recovery recrystallization is reliably formed, and therefore there is no problem. On the other hand, in the present invention, as the final processing and forming and memory treatment are performed simultaneously as described above, there was a fear that the matrix would be affected by the processing and the shape memory properties would deteriorate. Regarding this point, the present inventors conducted detailed experiments and found that dynamic recrystallization easily occurs in Cu-Al-Ni alloys, and recrystallization does not occur in the temperature range of the present invention even under severe processing conditions such as extrusion. It has been confirmed that this occurs, and it has been found that there are no problems such as those mentioned above. On the contrary, strong working can make the recrystallized grains uniform and fine, which can be expected to be effective against mechanical fatigue.

The reason for setting the temperature range in the present invention will be described below.

Lower limit=Tβ-100°C In a temperature range below this, recrystallization becomes difficult to occur, and the amount of β phase becomes insufficient, resulting in deterioration of shape memory properties.

Upper limit = Tm - 50°C In a temperature range exceeding this, there is a risk that the temperature will rise above the melting point when the temperature is further increased by processing heat, and the quality will deteriorate due to seizure during extrusion.

The alloy composition of the C1-AI-Ni alloy according to the present invention is not particularly limited, and any alloy that exhibits a shape memory effect by the above heat treatment is included in the present invention. Therefore, Cu-Al-N
In addition to the ternary system containing i as the main component, Mn, Ti, etc. may be added as necessary.

Moreover, the shape formed by the present invention is a line.

Regardless of whether it is a rod, tube, band, etc., it is also possible to use a corrugated shape such as a corrugated one if necessary.

[Example] Cu-12% by weight A1-5% by weight Ni-2% by weight Mn-
An alloy containing 1% by weight of Ti was melted to obtain an ingot with a diameter of 90 mm.

This was forged at 900°C, and the history, shape, and memory characteristics of the conventional material and the material of the present invention were investigated. Table 1 shows the results. The straightness of the wire is 1. It was evaluated by cutting it into lengths of m and measuring the width of lateral deviation as shown in FIG. As can be seen from the table, the product according to the present invention has good straightness and has a memory of straightness, and is an effective means for manufacturing a wide variety of products in small quantities.

[Effects of the Invention] Since the present invention is configured as described above, the 1-Ni-based shape memory alloy can be applied to Cu which has good straightness, no curling tendency, and correctly remembers the shape of the straight state. It has become possible to manufacture efficiently.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a method for measuring straightness.

Claims (1)

[Claims] A Cu-Al-Ni based shape memory alloy is prepared in a temperature range of Tβ-100°C≦T≦Tm-50°C (here, Tβ means β solid solution transformation temperature and Tm means melting start temperature). A method for producing a Cu-Al-Ni shape memory alloy, characterized in that extrusion molding and a process for memorizing the extruded shape are performed simultaneously by extruding and rapidly cooling immediately after extrusion.