KR100395588B1 - Shape memory alloy in Ti-Ni-Cu-Mo - Google Patents

Abstract

The present invention relates to a Ti-Ni-Cu-Mo shape memory alloy, which is based on a Ti-Ni-Cu-based alloy, and by adding Mo to 1 at% or less, B2-B19 transformation and B19-B19 ' Even when thermal cycles are carried out under 120 MPa load stress using materials that have been subjected to solution treatment by separating the transformation and improving the slip critical stress, the shape memory effect due to the B2-B19 transformation can be achieved without plastic deformation. To get it.

Description

Ti-Ni-Cu-M e shape memory alloy {Shape memory alloy in Ti-Ni-Cu-Mo}

The present invention relates to a Ti-Ni-Cu-Mo shape memory alloy, and more particularly, the Ti-Ni-Cu alloy and the B2-B19 transformation and B19-B19 'transformation of the Ti-Ni-Cu alloy are clearly separated. It relates to a Ti-Ni-Cu-Mo shape memory alloy to improve the slip critical stress by replacing a portion of Ni with Mo.

Generally, shape memory alloys are classified into Ti-Ni alloys, Cu alloys, and Fe alloys. Among them, isoatomic Ti-Ni alloys are most widely used. The shape memory effect of the Ti-Ni-based shape memory alloy of isoatomic composition is caused by the B2 (Cubic) -B19 '(Monoclinic) thermoelastic martensite transformation, and the lattice deformation accompanying the transformation results in the appearance of the shape memory effect. It is known to play an important role in.

Meanwhile, in addition to the B2-B19 'transformation, the Ti-Ni-based shape memory alloy undergoes a B2-R (Rhombohedral) transformation before the B19' martensite is formed by processing heat treatment and aging heat treatment, and the shape memory effect is also caused by the transformation. Is known to occur.

However, there are large differences in the shape memory effects associated with B2-B19 'and B2-R transformations. Therefore, for practical use of shape memory alloys, the intermediate properties of the shape memory effects (transformation strain and transformation history) accompanying two transformations are required. Since shape memory alloys are required, Ti-Ni-Cu alloys in which Ni is partially substituted by Ti-Ni alloys have been developed and used.

The Ti-Ni-Cu alloy is B2-B19 'transformation when the Cu concentration is less than 5at%, but B2-B19 (Orthorhombic) transformation occurs before the formation of B19' martensite when the Cu concentration is 10at% or more, The shape memory effect that accompanies this is intermediate between B2-B19 'and B2-R transformation.

However, when the Ti-Ni-Cu shape memory alloy has a Cu concentration of 10at%, the temperature range in which the B2-B19 transformation occurs and the temperature region indicating the B19-B19 'transformation are clearly separated, and the B2-B19 transformation is industrially used. Although it is very suitable for this, in this case, since the plastic working is impossible and cannot be used, in order to put the B2-B19 transformation of the Ti-Ni-Cu shape memory alloy into practical use, a Cu concentration of 10 at% or less, which can be plastic working, is used. There is a problem in that the method of clearly separating the B2-B19 transformation from B19-B19 'in the alloy has to be devised.

In addition, the Ti-Ni-Cu shape memory alloy has a problem in that the slip threshold stress is low in the solution treated state, so that slip deformation occurs during use, thereby deteriorating the shape memory effect.

Conventionally, to improve the slip phenomenon occurring in the Ti-Ni-Cu shape memory alloy, the slip critical stress is improved by processing heat, but the transformation of B2-B19 and B2-B19 'transformation is closer to this. There was a downside. In other words, Japanese Patent Laid-Open No. 61-177360 (August 9, 1986) discloses an alloy obtained by substituting a part of Ti or Ni to a Ti-Ni alloy by replacing up to 20 wt% of Cu, Mo, or the like. By dispersing and introducing defects into the material and arranging these defects appropriately by heat treatment, a method of producing a bidirectional shape memory alloy that induces bidirectional expression or controls bidirectional expression temperature and generating force is known. have. Further, Japanese Laid-Open Patent Publication No. 59-116341 (1984. 7. 5) alternately stacks a thin plate of Ti and Ni alternately, or alternately stacks a plate such as Ti, Ni, Cu or Mo, and heats the Ti. A method of manufacturing a shape memory alloy rod, a plate, and a pipe has been proposed as a method of alloying by heat of synthesis reaction with Ni.

However, the method known in Japanese Patent Laid-Open No. 61-177360 mentioned above is a heat treatment process that requires a high level of skill and experience in order to improve the slip critical stress of the shape memory alloy or to promote bidirectional expression. Since it must go through, there was a problem that the failure rate of the finished product is high. In addition, Japanese Patent Application Laid-Open No. 59-116341 (July 5, 1984) applies a self-combustion high temperature synthesis reaction (SHS) of Ti and Ni powders, which simplifies a complicated process compared to the case of manufacturing by dissolution method. Although there is an advantage, on the contrary, when another type of plate material is laminated between the Ti plate material and the Ni plate material, heat of reaction does not occur, and there is a high possibility that alloying is not performed or a heterogeneous alloy is produced. Thus, there was a closure that was not suitable for producing ternary alloys or quaternary alloys. The present invention allows the B2-B19 transformation and the B19-B19 'transformation of the Ti-Ni-Cu shape memory alloy to be clearly separated to facilitate the industrial application of the B2-B19 transformation, which is known to have an excellent shape memory effect. At the same time, Ti-Ni-Cu-Mo shape memory alloy can be used to improve the slip critical stress so that it can be used industrially without any additional heat treatment such as processing heat treatment on materials that have been subjected to solution treatment only. To provide. Another object of the present invention is to replace a part of Ni in the Ti-Ni-Cu shape memory alloy with Mo, without performing heat treatment, thereby improving the slip critical stress, as well as Cu in the existing Ti-Ni-Cu alloy. B2-B19 transformation occurs at concentrations of 10at% or more, and B2-B19 transformation occurs only by addition of Mo at 10at% or less Cu concentration, and B2-B19 transformation and B19-B19 'transformation are clearly separated and solutionized. The present invention provides a Ti-Ni-Cu-Mo-based shape memory alloy that can obtain an alloy having a slip critical stress of 120 MPa or more by treatment alone . It is still another object of the present invention to prepare a three- or multi-element alloy by melting and alloying a metal by a dissolution method, and to produce a Ti-Ni-Cu-Mo shape memory alloy having a high slip critical stress without processing heat treatment. And Ti-Ni-Cu-Mo shape memory alloys in which the B2-B19 transformation, which is only present in alloys containing 10at% or more of Cu concentration, is also present in 5at% or less of conventional Ti-Ni-Cu alloys . .

(A) of Figure 1 is the electrical resistance temperature curve of 50Ti-44.7Ni-5Cu-0.3Mo alloy,

(B) is the electric resistance temperature curve of 50Ti-44.5Ni-5Cu-0.5Mo alloy,

(C) is the electric resistance temperature curve of 50Ti-44.0Ni-5Cu-1.0Mo alloy.

(A) of Figure 2 is an X-ray diffraction diagram of 50Ti-44.7Ni-5Cu-0.3Mo alloy,

(B) is X-ray diffraction diagram of 50Ti-44.5Ni-5Cu-0.5Mo alloy,

(C) is X-ray diffraction diagram of 50Ti-44.0Ni-5Cu-1.0Mo alloy.

3 is a graph showing the Mo concentration dependence between Ms '(B2-B19 transformation start temperature) and Ms (B19-B19' transformation start temperature).

4 shows recoverable strains of Ti-44.7Ni-5Cu-0.3Mo and Ti-44.5Ni-5Cu-0.5Mo alloys.

This graph shows the load stress dependence.

5A is an electrical resistance temperature curve of Ti-39.7Ni-10Cu-0.3Mo alloy,

(B) is electric resistance temperature curve of Ti-39.5Ni-19Cu-0.5Mo alloy.

6A is an X-ray diffraction diagram of a Ti-39.7Ni-10Cu-0.3Mo alloy,

(B) is X-ray diffraction diagram of Ti-39.5Ni-19Cu-0.5Mo alloy.

Figure 7 (a) is a temperature curve showing the deformation amount of Ti-39.7Ni-10Cu-0.3Mo alloy

ego,

(B) is the temperature curve showing the deformation of Ti-39.5Ni-19Cu-0.5Mo alloy

to be.

8A is an electrical resistance temperature curve of Ti-34.7Ni-15Cu-0.3Mo alloy,

(B) is electric resistance temperature curve of Ti-34.5Ni-15Cu-0.5Mo alloy,

(C) is the electric resistance temperature curve of Ti-34.0Ni-15Cu-1.0Mo alloy.

9 is an X-ray diffraction diagram of a Ti-34.7Ni-15Cu-0.3Mo alloy.

10 is a temperature curve diagram showing the deformation amount of Ti-39.7Ni-15Cu-0.3Mo alloy.

11A is an electrical resistance temperature curve of Ti-29.7Ni-20Cu-0.3Mo alloy,

(B) is electric resistance temperature curve of Ti-29.5Ni-20Cu-0.5Mo alloy,

(C) is electric resistance temperature curve of Ti-29.0Ni-20Cu-1.0Mo alloy.

Fig. 12 is an X-ray diffraction diagram of a Ti-27.7Ni-20Cu-0.3Mo alloy.

13 is a temperature curve diagram showing the deformation amount of Ti-29.7Ni-20Cu-0.3Mo alloy.

The present invention for achieving the above object is 50Ti- (45-X) Ni-5Cu-XMo (at%) (X = 0.3 ~ 1.0), 50Ti- (40-X) Ni-10Cu-XMo (at %) (X = 0.3 ~ 1.0), 50Ti- (35-X) Ni-15Cu-XMo (at%) (X = 0.3 ~ 1.0), 50Ti- (30-X) Ni-20Cu-XMo (at%) It consists of (X = 0.3 ~ 1.0).

More specifically, the shape memory alloy of the present invention is a Ti-Ni-Cu-based alloy as a basic component, and by adding Mo below 1 at%, the B2-B19 transformation and B19-B19 'transformation are separated and slipped at the same time. Even if the thermal cycle is carried out under 120 MPa load stress by using the solution treated by improving the critical stress, the shape memory effect by B2-B19 transformation can be obtained without plastic deformation. .

Shape memory alloy according to the present invention is prepared by adding less than 1 at% Mo to Ti-45Ni-5Cu (at%), Ti-40Ni-10Cu (at%), Ti-35Ni-20Cu (at%) alloy, Since the melting point of Mo is very high at 26 ° C during the alloy production, the master alloy of Ti and Mo is prepared by the plasma melting method, and the prepared master alloy and sponge Ti (99.6% purity), pure Ni (99.9% purity), pure Cu (99.99% purity) is charged into a graphite crucible and subjected to high frequency vacuum melting.

Ingot manufactured is hot-rolled at 1123K in an alloy having a Cu concentration of 10 at% or less, and then processed into a wire having a diameter of 1.2 mm at 298K. (At this time, the amount of cold working is 25% or less.)

On the other hand, in an alloy having a Cu concentration of 15 at% or more, rolling and drawing are impossible, so that a sample is directly collected from an ingot.

Here, the amount of Mo is 1 at% or less because when the amount of Mo is added at least 1 at%, the transformation temperature is excessively lowered, which is beyond the normal use temperature range and the workability of the material is greatly deteriorated.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(Example 1)

1A is an electrical resistance temperature curve of 50Ti-44.7Ni-5Cu-0.3Mo alloy in which Ni of Ti-45Ni-5Cu (at%) alloy is substituted with 0.3% of Mo, and (b) is Ti- The electrical resistance temperature curve of 50Ti-44.5Ni-5Cu-0.5Mo alloy in which 0.5% of Ni of 45Ni-5Cu (at%) alloy is substituted with Mo, and (C) is the Ti-45Ni-5Cu (at%) alloy. The electrical resistance temperature curve of 50Ti-44.0Ni-5Cu-1.0Mo alloy in which 0.3% of Ni is substituted for Mo. The alloy has a high melting point of 2610 ° C, so the Ti and Mo mother alloys are subjected to the plasma dissolution method. The prepared master alloy, sponge Ti (purity 99.9%), pure Ni (purity 99.9%), and pure copper (99.99%) were charged into a graphite crucible and prepared by high frequency vacuum melting. At this time, the cold working amount was 25%. After cold working, the solution is maintained at 1123K for 1 hour and then quenched in ice water to obtain Ti-44.7Ni-5Cu-0.3Mo (at%) alloy and Ti-44.5Ni-5Cu-0.5Mo (at% ) The electrical resistance change of the alloy appears in two stages, but in the case of Ti-44.0Ni-5Cu-1.0Mo (at%) alloy, the electrical resistance change occurs in one stage.

(A) of Fig. 2 is the result of X-ray diffraction experiment with temperature change to explain the electrical resistance change of 50Ti-44.7Ni-5Cu-0.3Mo (at%) alloy, (B) is 50Ti-44.5Ni-5Cu This is the result of X-ray diffraction experiment with temperature change to explain the change of electrical resistance of -0.5Mo (at%) alloy, and (C) shows the change of electrical resistance of 50Ti-44.0Ni-5Cu-1.0Mo (at%) alloy. As a result of X-ray diffraction experiment with temperature change to explain,

B19 martensite in both 50Ti-44.7Ni-5Cu-0.3Mo (at%) alloy, 50Ti-44.5Ni-5Cu-0.5Mo (at%) alloy and 50Ti-44.0Ni-5Cu-1.0Mo (at%) alloy Is observed.

In the 50Ti-44.0Ni-5Cu-1.0Mo (at%) alloy, it can be seen that B2-B19 transformation and B19-B19 'transformation are completely separated.

FIG. 3 is a graph summarizing Mo concentrations by obtaining Ms '(B2-B19 transformation start temperature) and Ms (B19-B19' transformation start temperature) from FIGS. 1 and 2, wherein B19 martensite exists as Mo amount increases. It can be seen that the temperature zone is enlarged.

4 is a graph showing the load stress dependence of the recoverable deformation amount of the Ti-44.7Ni-5Cu-0.3Mo (AT%) alloy and the Ti-44.5Ni-5Cu-0.5Mo (at%) alloy. The recoverable strain increased and the Ti-44.7Ni-5Cu-0.3Mo (at%) alloy had a maximum strain of 6.4% and the Ti-44.5Ni-5Cu-0.5Mo (at%) alloy had a maximum strain of 7%.

(Example 2)

5A is an electrical resistance temperature curve of Ti-39.7Ni-10Cu-0.3Mo alloy, (B) is an electrical resistance temperature curve of Ti-39.5Ni-19Cu-0.5Mo alloy, and Ti and Mo Is prepared by using a plasma melting method, and the prepared mother alloy, sponge Ti (purity 99.9%), pure Ni (purity 99.9%) and pure copper (99.99%) are charged into a graphite crucible and prepared by high frequency vacuum melting. . At this time, the cold working amount was 25%. After cold working for 1 hour at 1123K it is prepared by performing a solution treatment to cold to ice water.

FIG. 6 shows the results of X-ray diffraction tests with varying temperatures to determine the reason for the change in electrical resistance of FIG. 5. FIG. 6 shows the X-ray diffraction diagrams of Ti-39.7Ni-10Cu-0.3Mo alloy of (A) and (B). As can be seen from the X-ray diffraction diagram of the Ti-39.5Ni-19Cu-0.5Mo alloy, B19 martensite is produced. Even when cooled to 213K, B19'martensite is not observed.

This is because the temperature range where B2-B19 transformation and B19-B19 'transformation occurs is separated by about 100K or more by Mo addition.

FIG. 7 is a static load thermal cycle test result for measuring the shape memory effect of Ti-39.7Ni-10Cu-0.3Mo (at%) alloy and Ti-39.5Ni-19Cu-0.5Mo (at%) alloy. According to the temperature curve showing the deformation amount of Ti-39.7Ni-10Cu-0.3Mo (at%) alloy of) and the Ti-39.5Ni-19Cu-0.5Mo (at%) alloy of (B), Although only the solution was subjected to the solution treatment, it can be seen that even if it is 120 MPa, the amount of deformation generated during cooling is all recovered upon heating.

(Example 3)

8A is an electric resistance temperature curve of Ti-34.7Ni-15Cu-0.3Mo alloy, (B) is an electric resistance temperature curve of Ti-34.5Ni-15Cu-0.5Mo alloy, and (C) Is an electrical resistance temperature curve of Ti-34.0Ni-15Cu-1.0Mo alloy, and the method for producing the alloy is the same as in Example 1 and 2. However, this alloy can be rolled and drawn, so that the sample is delivered directly from the ingot. The cut sample is subjected to the same solution treatment as in Example 1.

FIG. 9 is an X-ray diffraction test result of Ti-34.7Ni-15Cu-0.3Mo (at%) alloy to explain the electrical resistance change of FIG. 8, and only B19 martensite is observed even when cooled to 123K.

10 is a static load thermal cycle test result for measuring the shape memory effect of Ti-34.7Ni-15Cu-0.3Mo (at%) alloy, and shows the deformation amount of Ti-34.7Ni-15Cu-0.3Mo (at%) alloy. In spite of the temperature curve shown and only the solution solution, the amount of deformation generated during cooling was recovered even when heated to 120 MPa.

(Example 4)

11A is an electrical resistance temperature curve of Ti-29.7Ni-20Cu-0.3Mo (at%) alloy, and (B) is an electrical resistance of Ti-29.5Ni-20Cu-0.5Mo (at%) alloy. The temperature curve, (C) is the electrical resistance temperature curve of Ti-29.0Ni-20Cu-1.0Mo (at%) alloy, the alloy production method is the same as in Example 1, except that the alloy is rolled and As drawing is not possible, the sample is cut directly from the incoat. The cut sample is subjected to the same solution treatment as in Example 1. FIG. 12 is an X-ray diffraction test result of Ti-27.7Ni-20Cu-0.3Mo (at%) alloy performed to explain the electrical resistance change of FIG. 11, and only B19 martensite is observed even when cooled to 88K. FIG. 13 is a static load thermal cycle test result for measuring the shape memory effect of Ti-29.7Ni-20Cu-0.3Mo (at%) alloy, and shows the deformation amount of Ti-29.7Ni-20Cu-0.3Mo (at%) alloy. Although the sample shows only the solution treatment by the temperature curve shown, it can be seen that even if it is 120 MPa, the amount of deformation generated during cooling is all recovered upon heating. As described above, the Ti-Ni-Cu-Mo system of the present invention The shape memory alloy is cooled even at a significantly lower temperature in the variable range of 50Ti-{(30 ~ 45) -X} Ni- (5 ~ 20) Cu-XMo (at%) (X = 0.3 ~ 1.0). In addition to being observed, even though the sample was subjected to the solution treatment only, even if it is 120MPa, it can be seen that the amount of deformation generated during cooling is all recovered upon heating.

As described above, the Ti-Ni-Cu-Mo alloy according to the present invention is known to have an excellent shape memory effect because the stability of B19 martensite is increased and the B2-B19 transformation and B19-B19 'transformation are clearly separated. The industrial application of the B2-B19 transformation is made very easy, and the slip critical stress is improved, so that the material subjected to the solution treatment only has to be applied industrially without additional heat treatment such as processing heat treatment. By using it, the Ti-Ni-Cu-Mo alloy has a small temperature history of about 10K and a large load stress of about 120MPa is used as the driving device material used to exert excellent performance.

Claims (4)

Ti-Ni-Cu-Mo shape memory alloy consisting of 50Ti- (45-X) Ni-5Cu-XMo (at%) (X = 0.3 ~ 1.0). Ti-Ni-Cu-Mo shape memory alloy consisting of 50Ti- (40-X) Ni-10Cu-XMo (at%) (X = 0.3 ~ 1.0). Ti-Ni-Cu-Mo shape memory alloy consisting of 50Ti- (35-X) Ni-15Cu-XMo (at%) (X = 0.3 ~ 1.0). Ti-Ni-Cu-Mo shape memory alloy consisting of 50Ti- (30-X) Ni-20Cu-XMo (at%) (X = 0.3 ~ 1.0).