JP2916924B2 - TiNiCu-based shape memory alloy fine wire and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a TiNi-based shape memory alloy fine wire containing Cu and a method for producing the same.

[Prior art] TiNiCu alloys exhibit a more remarkable shape memory effect than TiNi-based alloys as the Cu content (addition amount) increases with the inverse transformation of thermoelastic martensitic transformation. Known and very promising industrially.

And the alloy wire of this TiNi-based shape memory alloy is a Ti-NiCu alloy wire containing 10 at% or more of Cu in atomic%.
The fact is that it has not been obtained even on a laboratory scale.

As one of them, TiNi-based alloys are usually
Most of Cu, which does not form a solid solution with TiNi-based alloys, has a relatively low melting point due to extremely slow solidification cooling
A compound of Ti _X Cu _Y is formed, and during solidification, much of it precipitates at crystal grain boundaries rather than within crystal grains.

As a result, the grain boundaries become extremely fragile and the mechanical properties of the material deteriorate.

Furthermore, the brittleness of the grain boundaries, that is, the mechanical properties of the alloy material, tend to increase as the Cu content increases, and more particularly in alloys with a Cu content of more than 10 at%. Become stronger.

Therefore, TiNiCu based alloy by the conventional melting casting method,
Approximately, even if it is said that the alloy fine wire is manufactured for the TiNiCu alloy whose Cu content does not exceed 10 at%, in the manufacturing process, when the ingot after melting and casting is formed into a diameter of 5 to 10 mm by hot working. Since the mechanical properties during hot working are smaller than those of conventional TiNi-based alloys, in hot working, the working ratio is made as small as possible and annealing is repeated alternately.

Further, since the above-mentioned precipitate of Ti _X Cu _Y has a relatively low melting point, when it is processed at a temperature of about 800 ° C. or more, it exhibits hot brittleness and causes hot cracking.

As described above, there are many problems and the like, and it cannot be said that it has been obtained industrially stably.

All of these problems and limitations in hot working are due to grain boundary precipitation of the Ti _X Ni _Y compound generated due to the low solidification rate during melt casting.

Therefore, in recent years, experimental research has been conducted using a water-cooled copper mold as a casting mold to increase the solidification rate, but the solidification rate has been improved enough to suppress the precipitation of Ti _X Ni _Y compounds. The fact is that they have not.

In addition, for those containing 10 at% or more of Cu, even if the above-described problem in the hot working process is solved,
In subsequent cold working, repetitive annealing is required due to severe work hardening. That is, there is a major problem that the cost required for cold working as a whole accounts for a large part of the cost of the TiNiCu alloy wire.

[Problems to be Solved by the Invention] Therefore, recently, in order to solve the cost problem of the thin alloy wire, research has been focused on shortening the manufacturing process.

One of the research methods is continuous casting, which gradually changes (solidifies) a molten alloy to a solid state.

According to this method, the solidification rate of the molten metal is relatively low, and therefore, the center of the alloy ingot (the final solidified portion on the cross section) is relatively easily segregated, and it is known that a problem such as a crack is caused in a later step. TiNiCu alloys have not yet been put to practical use, let alone TiNi-based shape memory alloys.

Therefore, the technical problem of the present invention is to produce an alloy thin wire while suppressing Ti _X Ni _Y precipitates, and to have a low-cost and circular cross section of 10 at.
An object of the present invention is to provide a TiNiCu-based shape memory alloy thin wire containing more than% of Cu and a method for directly producing the same.

[Means for Solving the Problems] According to the present invention, Ni is 49 to 51 at%, and the balance is substantially Ti
A TiNiCu-based shape memory alloy fine wire characterized by being obtained by replacing Ni in an amount exceeding 10 at% of the alloy consisting of Cu with Cu and being crystalline.

According to the present invention, a cooling liquid layer is formed in a rotating cylindrical drum by centrifugal force, and Ti is contained in the cooling liquid layer.
A method for producing a TiNi-based alloy thin wire for injecting a molten metal of a Ni-based alloy as a jet and solidifying the molten metal,
In the molten TiNi alloy, Ni is 49-51at%, and the balance is substantially
Characterized in that an alloy of Ti is replaced with Cu in an amount exceeding 10 at% by Cu, and heat treatment is performed after the solidification.
Thus, a method for producing a system shape memory alloy fine wire is obtained.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples.

FIG. 1 is a diagram showing an apparatus for manufacturing a TiNiCu-based shape memory alloy thin wire according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG.

In FIG. 1, the manufacturing apparatus includes a cylindrical drum 1 having an open surface, a rotating shaft 2 having one end at the center of the other surface of the cylindrical drum 1, and a sliding bearing 3 rotatably supporting the shaft 2. , 3.

Further, it has a pulley 4 interposed between the slide bearings 3 and 3 and fixed to the shaft 2, and a V-belt 5 mounted on the pulley 4 and rotated by a DC motor.

Further, at the edge of the drum 1, an outflow prevention plate 6 having a surface protruding toward the central axis is provided.
And a supply pipe 7 which is bent into a rectangular shape and supplies a cooling liquid 9 into the drum 1 from one surface side.

The cooling liquid 9 supplied into the drum 1 forms a cooling liquid layer 9 by the centrifugal force of the rotation of the drum 1. A substrate 10 having one end inserted therein is provided in the opening on one surface side of the drum, and a portion extending from one end of the substrate 10 is supported by a plurality of rollers 11 so as to be movable in the horizontal direction.

A rack 12 is provided so as to face the roller 11 with the substrate 10 interposed therebetween, and the rack 12 meshes with a pinion 13.
Further, at one end of the substrate, a molten metal spraying device 14 is provided. The injection device 14 has a nozzle portion, and a jet 15 of molten metal is jetted from the nozzle portion by the argon gas pressure.

The drum 1 has a gap 20 divided by a partition wall 17 in the wall.
The inside is cooled through a cooling liquid.

The operation of the apparatus according to the embodiment of the present invention having such a configuration will be described.

When the rotation of the drum 1 reaches a predetermined value due to the rotation of the V-belt 5, the drum 1 is injected into the inner surface of the drum 1 through a cooling pipe such as water by a liquid supply pipe 7.

The injected liquid forms a cooling liquid layer 9 by centrifugal force, and the liquid drum 1
Spills are prevented.

Then, a molten metal 15 obtained by re-melting the alloy ingot into the liquid layer 9 is jetted from the jetting device 14 as a molten metal jet at an appropriate speed to produce an alloy thin wire of a TiNiCu-based shape memory alloy. Example 1. Each of the alloys having the composition of Ti50Ni20Cu30 was melted in an argon atmosphere by an apparatus using water having a diameter of 500 mmφ, a depth of 20 mm and a temperature of 0 ° C. as a cooling liquid layer 9 as the drum 1 shown in FIG. Melting at a temperature higher by 50 ° C. and a pore diameter D = 20
This molten metal was jetted into the cooling liquid layer 9 at a speed of 430 mm / min by controlling the argon gas pressure from the spinning nozzle of the jetting device 14 of 0 (μm). At this time, the peripheral speed of the drum 1 was 500 m / min.

Comparative Example 1 For comparison, an alloy having a composition of Ti50Ni45Cu5 was spun by the same method.

With the composition of the alloy used, fine wire formation, and surface shape,
Further, the martensitic transformation temperature (Ms) and the reverse transformation end temperature (Af) were measured by a differential scanning calorimeter (DSC) for each sample obtained by subjecting the generated thin wire to heat treatment at 800 ° C. for 2 hours.

In addition, the result of the fine wire sample (Comparative Example 2 and Comparative Example 3) by the dice method is also shown for reference. As shown in Table 1, according to the method of the embodiment of the present invention, Ti containing Cu in an amount exceeding 10 atomic%, which cannot be conventionally produced, is used.
A NiCu alloy fine wire is obtained. Further, the cross section of the obtained alloy fine wire was examined with an optical microscope and an X-ray microanalyzer to determine whether or not there was a problem such as a crack. However, no such type was found over the entire length. .

[Effects of the Invention] As described above, according to the present invention, Ti _x Ni _Y precipitates are suppressed to produce an alloy thin wire, which is inexpensive and contains Cu in an amount exceeding 10 atomic% which is a circular cross section. It is possible to provide a TiNiCu-based shape memory alloy and a method for directly producing the same.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an apparatus for carrying out the method for producing a TiNiCu alloy fine wire of the present invention, and FIG. 2 is a sectional view of the apparatus shown in FIG. In the figure, 1 ... cylindrical drum, 2 ... rotating shaft, 3 ... sliding bearing, 4 ... belt wheel, 5 ... V belt, 6 ... outflow prevention plate, 7 ... liquid supply pipe, 8 ... ... Control valve, 9 ... Cooling liquid layer, 10 ... Substrate, 11 ... Roller, 12 ... Rack, 13 ...
... pinion, 14 ... injection device, 15 ... molten metal.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C22C 1/00-19/03 B22D 11/06

Claims (2)

(57) [Claims] 1. A TiNiCu-based shape memory characterized in that Ni is 49 to 51 at% and the balance is substantially crystalline. Alloy fine wire. 2. A TiNi-based cooling liquid layer is formed in a rotating cylindrical drum by centrifugal force, and a molten TiNi-based alloy is jetted into the cooling liquid layer as a jet to solidify the molten metal. A method for producing a shape memory alloy fine wire, wherein the molten TiNi alloy is obtained by replacing Ni in an amount of 49 to 51 at% and the balance of Ni exceeding 10 at% in an alloy substantially consisting of Ti with Cu. And a heat treatment after the solidification.