KR20180006861A - TiNiNb ALLOY AND FOR IT USED THERMAL CONTRACTION RING FIXING COUPLING - Google Patents

Abstract

The present invention relates to a Ti-Ni-Nb shape memory alloy, comprising: 42-50 at% of Ti; 0.1-15 at% of Nb; and the remaining Ni and other inevitable impurities, wherein an atom ratio of Ni to Ti is 0.7-1.05, thereby capable of widening temperature hysteresis to be significantly useful for a product for fixing a portion to be connected such as a fastener or a coupling.

Description

TECHNICAL FIELD The present invention relates to a TiNiNb alloy and a heat shrinkable ring for fixing the joint using the TiNiNb alloy.

The present invention provides a TiNiNb shape memory wire having Nb added thereto and having an operating temperature range of a specific temperature or higher, and a TiNiNb alloy which can be used as a heat shrinkable ring for fixing a joint, and a heat shrinkable Ring.

As is well known, a binary shape memory alloy composed of a Ti element and a Ni element is a material widely used in industrial and medical applications due to its excellent shape memory effect, superelastic effect, and corrosion resistance, but the atomic ratio of the two elements is 1: The Austenite finishing temperature (Af) point at 100.0 at 50.0 at% Ni decreased to 0 at 51.0 at% Ni content, which was 1 at%, and the transformation temperature was 100 at 1% The change is an alloy system with a very high compositional dependency, which means that a change in composition of 0.1 at% results in a transformation temperature change of about 10.

In order to further utilize the TiNi material, a variety of products are being developed by satisfying the specification of the desired product by adding a third element such as Cu, Co, and the like.

Korean Patent No. 10-0622510 Korean Patent Publication No. 10-2010-0028304

The present invention relates to a TiNiNb alloy which is useful for fixing a joint such as a fastener or a coupling by widening the thmperature hysteresis by adding an Nb element to the TiNi alloy system, Heat shrink ring.

The objects of the embodiments of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description .

In order to achieve the above object, the Ti-Ni-Nb type shape memory alloy according to the present invention contains 42 to 50 atomic% of Ti, 0.1 to 15 atomic% of Nb, the remainder Ni and other unavoidable impurities, And a ratio of 0.7 to 1.05.

In the Ti-Ni-Nb based shape memory alloy according to an embodiment of the present invention, the shape memory alloy includes a matrix phase and a phase phase, and the base phase has an Ni / Ti atomic ratio of 1 to 1.05, The process phase may have a Ni / Ti atomic ratio of 0.8 to 0.97.

In the Ti-Ni-Nb-based shape memory alloy according to an embodiment of the present invention, the Nb may be 9 atomic% or less and the Ni / Ti atomic ratio may be 1 to 1.05.

In the Ti-Ni-Nb-based shape memory alloy according to an embodiment of the present invention, the shape memory alloy may have an elongation of 30% to 60%.

The present invention also includes a method for producing the above-mentioned Ti-Ni-Nb type shape memory alloy.

The method for producing a Ti-Ni-Nb based shape memory alloy according to the present invention comprises the steps of: dissolving alloy components comprising 42 to 50 atomic% of Ti, 0.1 to 15 atomic% of Nb, the remainder Ni and other unavoidable impurities, A step of subjecting the alloy base material obtained through the step to a solution treatment, and a step of quenching the solution-annealed alloy base material, wherein the Ni / Ti atomic ratio is 0.7 to 1.05.

In the method for producing a Ti-Ni-Nb based shape memory alloy according to an embodiment of the present invention, the shape memory alloy includes a matrix phase and a phase phase, and the base phase has an Ni / Ti atomic ratio of 1 to 1.05 , The process phase may have an Ni / Ti atomic ratio of 0.8 to 0.97.

In the method for producing a Ti-Ni-Nb type shape memory alloy according to an embodiment of the present invention, the Nb may be 9 atomic% or less and the Ni / Ti atomic ratio may be 1 to 1.05.

In the method for producing a Ti-Ni-Nb-based shape memory alloy according to an embodiment of the present invention, the shape memory alloy may have an elongation of 30% to 60%.

In the method for producing a Ti-Ni-Nb based shape memory alloy according to an embodiment of the present invention, the dissolving step includes melting a Ti ingot made of Ti and a Ni ingot made of Ni on the Nb ingot made of Nb They may be alternately laminated and dissolved.

In the method for producing a Ti-Ni-Nb based shape memory alloy according to an embodiment of the present invention, the shape memory alloy manufacturing method includes the steps of mechanically processing the alloy base material obtained through the dissolving step to produce a wire, And subjecting the wire to a solution treatment at a temperature of 1050 to 1300 K.

In the method of manufacturing a Ti-Ni-Nb type shape memory alloy according to an embodiment of the present invention, it may include an aging heat treatment at a temperature of 650 to 800 K after the quenching step.

In the method for manufacturing a Ti-Ni-Nb type shape memory alloy according to an embodiment of the present invention, the method may further include a step of cold-working the wire between the quenching step and the aging heat treatment step.

In the method of manufacturing a Ti-Ni-Nb based shape memory alloy according to an embodiment of the present invention, the cross-sectional reduction rate of the wire may be 10% or less in the cold working step.

The present invention also includes a heat-shrinkable ring for fixing the joint including the above-described Ti-Ni-Nb type shape memory alloy.

The present invention relates to a TiNi alloy system in which a Nb element is added to form a soft Nb-rich phase which is in a non-solid state with a TiNi base structure to expand the thmperature hysteresis, TiNiNb alloys which are very useful in fixing products for joints such as heat-shrinkable joints and heat shrinkable rings for fixing joints using the same can be provided.

On the other hand, even if the effects are not explicitly mentioned here, the effect described in the following specification, which is expected by the technical features of the present invention, and its potential effects are treated as described in the specification of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an optical microphotograph showing the microstructure of a Ti _{50- x / 2} Ni _{50 -x / 2} Nb _x alloy according to Examples 1 to 6 and Comparative Examples 1 to 3;
2 is a diagram illustrating a virtual state diagram of a TiNi-Nb alloy system according to an embodiment of the present invention.
3 is an optical microscope photograph showing the microstructure of the Ti ₅₀ Ni _{50 - x} Nb _x alloy according to Examples 7 to 12 and Comparative Example 4.
4 is an optical microscope photograph showing the microstructure of the Ti _{50 - x} Ni ₅₀ Nb _x alloy according to Examples 13 to 14 and Comparative Example 6.
5 is a graph showing a change in martensite (Ms) transformation temperature of a Ti-Ni-Nb type shape memory alloy according to an embodiment of the present invention.
FIG. 6 is a graph illustrating a graph of the transformation temperature of martensite (M) according to the addition of Nb elements according to an embodiment of the present invention.
FIG. 7 is a graph illustrating a martensite (M) transformation temperature change graph according to a change in Ni / Ti ratio according to an embodiment of the present invention.
FIG. 8 is a graph illustrating a graph of a transformation temperature of the martensite (M) phase and the transformation temperature of the austenite phase (A) according to the heat treatment temperature change according to the embodiment of the present invention.
FIG. 9 is a graph illustrating a graph of a transformation temperature of the martensite phase (a) and the transformation temperature of the austenite phase (b) according to the variation of the amount of cold working according to the embodiment of the present invention.
FIG. 10 is a graph illustrating a transformation temperature change of martensite phase (a) and austenite phase (b) according to a change of Ni / Ti ratio according to an embodiment of the present invention.
11 is a graph showing a graph of a stress-strain change according to the change (a) of the Nb content and the change (b) of the Ni / Ti ratio according to the embodiment of the present invention.
12 is a graph illustrating a graph of a change in fracture strength-fracture strain according to a change in the content of Nb added according to an embodiment of the present invention.
13 is a graph illustrating a graph of a change in fracture strength-fracture strain according to a change in Ni / Ti ratio according to an embodiment of the present invention.
FIG. 14 is a view illustrating a graph of a change in fracture strength-fracture strain according to a change in the amount of cold working according to an embodiment of the present invention.
15 is a view illustrating a schematic diagram of a process sequence for manufacturing a TiNiNb shape memory ring finished product according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. The following embodiments and drawings are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. In addition, unless otherwise defined in the technical and scientific terms used herein, unless otherwise defined, the meaning of what is commonly understood by one of ordinary skill in the art to which this invention belongs is as follows, A description of known functions and configurations that may unnecessarily obscure the gist of the present invention will be omitted.

The Ti-Ni-Nb type shape memory alloy according to the present invention contains 42 to 50 atomic% of Ti, 0.1 to 15 atomic% of Nb, the remainder Ni and other unavoidable impurities.

In general, a Ti-Ni binary alloy among Ti-Ni based shape memory alloys is an alloy containing Ti and Ni in the same amount as the number of atoms, i.e., atomic ratio of 1: 1, The feed is not just an alloy of Ti and Ni, but an intermetallic compound with a regularly ordered arrangement of atoms on both sides. Ti-Ni alloys have the same atomic ratio of Ti and Ni or have a Ni / Ti atomic ratio of 1 or more. However, when the atomic ratio of Ni / Ti is 1.04, the transformation temperature is drastically decreased.

In order to solve such a problem, in the present invention, a Ti-Ni-Nb-based alloy containing 42 to 50 atomic% of Ti, 0.1 to 15 atomic% of Nb and the balance Ni and other unavoidable impurities and having a Ni / Ti atomic ratio of 0.7 to 1.05 Memory alloy.

In addition, the Ti-Ni-Nb based shape memory alloy according to the present invention may contain a dendritic structure in its microstructure by containing 0.1 to 15 atomic percent of Nb. When the content of Nb is less than 0.1 atomic%, it is difficult to solve the problem that the above-mentioned transformation temperature sharply decreases. Further, when the Nb content exceeds 15 atomic%, most of the microstructure may have columnar structure or lamellar (lamellar) structure. Such columnar structure or lamellar structure may deteriorate mechanical properties.

However, in the present invention, in order to observe the microstructure, the Ti-Ni-Nb type shape memory alloy is dissolved in an aqueous solution containing nitric acid and hydrofluoric acid And the etched Ti-Ni-Nb type shape memory alloy was subjected to an optical microscope, a scanning electron microscope (SEM) or the like.

The Ni / Ti atomic ratio of the Ti-Ni-Nb type shape memory alloy according to the present invention may be 0.7 to 1.05. When the Ni / Ti atomic ratio described above is satisfied, the Ti-Ni-Nb type shape memory alloy according to the present invention can prevent the abrupt decrease of the above-mentioned transformation temperature even if the Ni content is increased or decreased, K of martensite (Ms) transformation temperature.

Accordingly, the present invention includes a Ti-Ni-Nb type shape memory alloy containing 42 to 50 atomic% of Ti, 0.1 to 15 atomic% of Nb, the remainder Ni and other unavoidable impurities and having a Ni / Ti atomic ratio of 0.7 to 1.05 , Which can be used for fixing joints such as fasterners and couplings by widening the temperature hysteresis.

The Ti-Ni-Nb type shape memory alloy according to an embodiment of the present invention may include a matrix phase and a process phase. At this time, the matrix phase has a Ni / Ti atomic ratio of 1 to 1.05, and the Ni / Ti atomic ratio of the process phase may be 0.8 to 0.97.

In describing the present invention, the base texture may be a part located within the dendritic tissue described above, and may represent a white part in the observation of microstructure. In addition, eutectic may be indicative of a black part in the observation of microstructure.

In detail, the matrix is composed of 46 to 49 atomic% of Ti, 46 to 50 atomic% of Ni, and 1 to 6 atomic% of Nb, and the Ni / Ti atomic ratio can be 1 to 1.05.

In addition, the process phase may consist of 39 to 46 atomic% of Ti, 37 to 39 atomic% of Ni, and 15 to 23 atomic% of Nb, and the Ni / Ti atomic ratio may be 0.8 to 1.0.

Meanwhile, in the Ti-Ni-Nb based shape memory alloy according to another embodiment of the present invention, the Nb may be 9 atomic% or less and the Ni / Ti atomic ratio may be 1 to 1.05. Ni-Nb based shape memory alloy according to the present invention has a strength (tensile strength, fracture strength, etc.) and a strain rate (or an elongation) in the case where the category of the content of Nb and the category of the Ni / Ti atomic ratio are satisfied And the work hardening rate can be lowered even after rearrangement on martensite. This is very advantageous when manufacturing a heat shrinkable ring for fixing wires or joints because it is not easily hardened on martensite when applied to actual products.

Accordingly, the Ti-Ni-Nb type shape memory alloy according to an embodiment of the present invention may have an elongation of 30% to 60%. The elongation may be measured in martensite phase and austenite phase. When such an elongation is satisfied, the Ti-Ni-Nb type shape memory alloy according to the present invention is deformed in a specific amount on the martensite, and can be restrained to its original shape at a high temperature to exhibit binding force.

The present invention also includes a method of manufacturing a Ti-Ni-Nb type shape memory alloy using the above-described Ti-Ni-Nb type shape memory alloy.

The method for producing a Ti-Ni-Nb based shape memory alloy according to the present invention comprises the steps of: dissolving alloy components containing 42 to 50 atomic% of Ti, 0.1 to 15 atomic% of Nb, residual Ni and other unavoidable impurities; , And quenching the solution-treated alloy base material, wherein the Ni / Ti atomic ratio can be 0.7 to 1.05.

Further, in the method of manufacturing a Ti-Ni-Nb based shape memory alloy according to an embodiment of the present invention, the shape memory alloy includes a matrix structure and a process phase, 1.05, and the Ni / Ti atomic ratio of the process may be 0.8 to 0.97.

Meanwhile, in the method for producing a Ti-Ni-Nb based shape memory alloy according to an embodiment of the present invention, the Nb may be 9 atomic% or less and the Ni / Ti atomic ratio may be 1 to 1.05, The memory alloy may have an elongation of 30% to 60%.

On the other hand, in the method for producing a Ti-Ni-Nb based shape memory alloy according to an embodiment of the present invention, the dissolving step may include melting the Ti ingot made of Ti and Ni And alternately laminating and dissolving the ingots.

In detail, when a metal containing Ti, Ni and Nb is dissolved, Ti has a high reactivity at a high temperature and the transformation temperature may be abruptly changed depending on the composition. Therefore, extremely precise control is required on the charging order and the basis weight of the metal . Further, in the case of using the metal powder, when the arc is shot on the sample in which the powder is stacked, there is a disadvantage that the sponge Ti generates fumes or impurities.

Accordingly, it is preferable to use Ti, Ni and Nb as the ingot in the melting step, respectively, and to laminate and dissolve in the above order.

In explaining the present invention, the ingot may be formed of granules having an average diameter of 1 to 3 mm, but the present invention is not limited to the average diameter category of the ingot.

Meanwhile, a method for manufacturing a Ti-Ni-Nb based shape memory alloy according to an embodiment of the present invention includes the steps of mechanically processing an alloy base material obtained through the dissolving step to produce a wire, RTI ID = 0.0 > 1300 K < / RTI >

In detail, the mechanical working of the alloy base material may be a method commonly used in the art, but may include hot forging, hot extrusion, cold drawing, and the like. Further, after performing the hot forging and the hot extrusion, the cold drawing and the annealing at the intermediate temperature can be repeated. The temperature during hot forging and hot extrusion may be the same as or lower than the above-mentioned solution treatment temperature, but the present invention is not limited thereto.

Further, in the method for manufacturing a Ti-Ni-Nb type shape memory alloy according to an embodiment of the present invention, it may further include an aging heat treatment step at a temperature of 650 to 800 K after the quenching step.

Further, in the method for producing a Ti-Ni-Nb type shape memory alloy according to an embodiment of the present invention, the step may further include a step of cold-working the wire between the quenching step and the aging heat treatment step .

In detail, in the cold working step, the reduction ratio of the cross section of the wire may be 10% or less. The calculation of the sectional reduction rate may be a method commonly used in the art, but may be calculated after cold-working the wire, for example, after measuring the cross-sectional area before and after the cold working.

On the other hand, when the reduction rate of the cross section of the wire is more than 10% at the time of cold working, there is a problem that the fracture strain of the Ti-Ni-Nb type shape memory alloy or the wire is sharply reduced.

Further, the present invention includes a heat-shrinkable ring for fixing a joint including the above-described Ti-Ni-Nb type shape memory alloy.

In addition, the present invention includes a heat shrinkable ring for fixing a joint manufactured by the above-described method for manufacturing a Ti-Ni-Nb type shape memory alloy.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments.

Examples 1 to 13 and Comparative Examples 1 to 6

In Table 1, the design composition ratio of the Ti-Ni-Nb type shape memory alloy according to the embodiment of the present invention is shown in atomic%. First, the ingot of Ti, Ni and Nb was weighed using a balance capable of measuring up to 0.01 g so as to have the composition shown in Table 1.

The pre-weighed Nb ingot was first charged into the mold, and then the Ti ingot and the Ni ingot were alternately stacked. Thereafter, the stacked ingots were dissolved by a vacuum arc melting method. At this time, the vacuum degree is 5 X 10 ^- were to ³ torr, the atmosphere is dissolved under an argon atmosphere to prevent the reaction of Ti with N _2.

After dissolution, all samples were subjected to solution treatment at 1,173 K for 1 hour, and then quenched. The samples prepared after quenching were etched using water: nitric acid: hydrofluoric acid to observe the microstructure.

Composition formula Ti Ni Nb Ni / Ti Example 1 Ti _{50 - x / 2} Ni _{50 - x / 2} Nb _x 48.5 48.5 3.0 One Example 2 47.5 47.5 5.0 One Example 3 45.5 45.5 9.0 One Example 4 45.0 45.0 10.0 One Example 5 44.0 44.0 12.0 One Example 6 42.5 42.5 15.0 One Comparative Example 1 50.0 50.0 0.0 One Comparative Example 2 40.0 40.0 20.0 One Comparative Example 3 37.5 37.5 25.0 One Example 7 Ti ₅₀ Ni _{50 - x} Nb _x 50.0 47.0 3.0 0.94 Example 8 45.0 5.0 0.9 Example 9 43.0 7.0 0.86 Example 10 42.0 8.0 0.84 Example 11 40.0 10.0 0.8 Example 12 35.0 15.0 0.7 Comparative Example 4 30.0 20.0 0.6 Comparative Example 5 20.0 30.0 0.4 Example 13 Ti _{50 - x} Ni ₅₀ Nb _x 49.0 50.0 1.0 1.02 Example 14 48.0 50.0 2.0 1.04 Comparative Example 6 47.0 50.0 3.0 1.06

Hereinafter, the microstructure, compositional analysis, phase transformation temperature and the like of the Ti-Ni-Nb type shape memory alloy prepared in the above examples and comparative examples will be described in detail.

1 is an optical microscope photograph showing the microstructure of the Ti _{50- x / 2} Ni _{50 -x / 2} Nb _x alloy described in Examples 1 to 6 and Comparative Examples 1 to 3. 1, the Ti-Ni-Nb type shape memory alloy according to the embodiment of the present invention is an alloy containing no Nb element (Comparative Example 1), an alloy containing an excessive amount of Nb element (Comparative Examples 2 and 3 ) And the organization. In detail, FIG. 1 (b) to FIG. 1 (d) show the white part (denoted by A) and the black part (denoted by B) of the dendritic tissue, Microstructure was observed. In (f), fine dendrite texture (denoted by c), which did not appear in Ti ₄₀ Ni ₄₀ Nb ₂₀ , was observed at the same time as the above head.

Table 2 is a table showing results of analysis of the components A, B, and C shown in FIG. The components listed in Table 2 are all atomic%. The components were identified using the EPMA after the A, B, and C sites were identified by SEM. As shown in Table 1, in the case of A in the white part, it can be seen that the Nb element is a TiNi base structure with a small amount of solid solution, and the content of Nb element in this part is also increased at the same time as the content of Nb element increases . In the case of B, the content of Nb element is 15 to 23 atomic%, and it is understood that the content distribution is relatively uniform than A in white portion. In addition, according to the virtual state diagram, the B can be inferred in terms of the process, and in the case of C, the Nb-rich state can be confirmed as a result of the component analysis.

A B C Ti Ni Nb Ni / Ti Ti Ni Nb Ni / Ti Ti Ni Nb Example 1 49.0 49.5 1.5 1.01 45.3 37.4 17.3 0.825 Example 2 47.4 49.9 2.7 1.05 41.7 37.9 20.4 0.908 Example 3 47.3 49.4 3.3 1.04 41.5 38.0 20.5 0.915 Example 4 46.8 46.8 4.2 One 40.5 38.9 20.6 0.96 Example 6 46.2 46.2 5.0 One 39.9 38.6 21.5 0.967 Comparative Example 2 40.1 40.0 19.9 0.997 Comparative Example 3 40.2 41.8 18.0 1.039 12.4 2.6 85.0

A virtual TiNi-Nb phase diagram is prepared by combining the observation results of these phases and shown in FIG. Referring to FIG. 2, the presence of the phases depending on the content of the Nb element can be quantitatively explained. In other words, according to the diagram, it is seen in the process of the TiNi matrix (alpha phase) corresponding to the region A and the Nb-rich phases β and B of the region C. As the content of Nb increased, Ti _{42 . 5} Ni _{42 . 5} Nb ₁₅ phase is formed.

3 is an optical microscope photograph showing the microstructure of the Ti ₅₀ Ni _{50 - x} Nb _x alloy described in Examples 7 to 12 and Comparative Example 4. Fig. Referring to FIG. 3, the microstructure of the Ti ₅₀ Ni _{50 - x} Nb _x alloy showed similar tendency to the microstructure of the Ti _{50- x / 2} Ni _{50 -x / 2} Nb _x alloy. (A) to (d) are observed as a white part (denoted as A) and a black part (denoted as B) of dendritic tissue, and Ti _{50 -x / 2} Ni _{50 - x / 2} Nb _x alloy, rather than a lamellar structure in the columnar structure. In the case of (f), Nb-rich phase was observed at the same time in the Ti ₅₀ Ni ₃₀ Nb ₂₀ .

4 is an optical microscope photograph showing the microstructure of the Ti _{50 - x} Ni ₅₀ Nb _x alloy described in Examples 13 to 14 and Comparative Example 6. Referring to FIG. 4, in the composition of the Ti _{50 - x} Ni ₅₀ Nb _x alloy, a relatively large amount of Ni exists in the matrix so that Ms has a very low temperature which is not suitable for practical purposes. As a result, when seen, according to Fig _{4, Ti 50 -x / 2 Ni} 50-x / 2 Nb x alloys and Ti ₅₀ Ni _{50 -} but is not a big difference between the microstructure of the _x Nb _x alloy, the dendritic white tissue There was a minute difference in the content of Nb in the portion (A) and the black portion (B). In other words, the atomic radius of Ti element and Nb element are similar to each other, so they are not solved with Ni element and are solved with Ti element, and the content of Ti element is decreased when Nb element is increased in both phases.

Fig. 5 is a graph showing a change in the martensite (Ms) transformation temperature of the Ti-Ni-Nb type shape memory alloy produced in the above-described Examples and Comparative Examples. FIG. 5 is a graph showing the change of the Ms transformation temperature according to the addition of Nb elements by the DSC analysis in the above-described embodiments and comparative examples. The first Ti _{50 -x / 2} Ni _{50 -x / 2} Nb _x In the case of alloys, the Ms transformation temperature is almost constant when the content of Nb element is in the range of 5 to 15 at%. As shown in Table 2, the content of Nb in the α phase was increased by the increase of the content of Nb, but the ratio of Ni / Ti was almost constant. This is because the transformation temperature change of Ms, Is considered to be larger. This is analogous if the transition temperature or physical properties such as Ms depend on the Ni element content change even in the Ti-Ni binary alloy, and it is possible to deduce from the context of the Ms temperature change shown in FIG. Can be explained.

Also, when the content of the Nb element is 5 at% or less, the Ni / Ti ratio in the? Phase increases as the content of the Nb element increases. Therefore, Ms decreases as the content of Nb element increases. Then, the Ni / Ti ratio is almost constant in the range of 5 to 15 at% of the Nb element, so that it is constant without change of Ms. In addition, when the content of Nb element is more than 20 atomic%, the α-phase disappears, and the bcc phase constituting the eutectic phase and the Nb-rich phase inhibiting the B2 phase transformation within the eutectic phase are reduced.

Also, Ti ₅₀ Ni _{50 - x} Nb _x In the case of the alloy, the change of the transformation temperature of Ms is almost constant even when the content of Nb element of 3 ~ 30 at% is changed, and it is judged that the Ni / Ti ratio is almost constant, The transformation temperature is high and the transformation temperature for the subsequent process is almost constant without any change. However, the absolute value of the transformation temperature is smaller than the binary alloy, which is interpreted as the fact that the Nb element is employed in the matrix. Ti _{50 - x} Ni ₅₀ Nb _x In the case of alloys, the Ni / Ti ratio increases rapidly as the content of Nb element increases, so that the change of transformation temperature is considered to be very high.

As a result of examining the compositional dependence of the Ni and Nb elements, it was found that when the composition ratio of Ti and Ni was fixed to the atomic ratio and the amount of Nb element was changed, the microstructural change was characterized by lamellar structure , And the eutectic phase composition was found to be B2 phase and bcc-phase Nb-rich phase. As a result of DSC measurement, It is necessary to systematically investigate the effect of optimal Ni / Ti ratio on the fundamental dependence of Ni / Ti composition ratio.

Examples 14 to 21 and Comparative Examples 7 to 11

The above ingots were dissolved in the same manner as in the vacuum dissolution method described in Example 1, and the compositions used in this Example are shown in Table 3 below. The molten ingot was hot-drawn and hot extruded, cold drawn and annealed at intermediate temperature, and made into a wire of 1 mm diameter. The cut sample was cut to a required length (e.g., 40 mm, 100 mm, etc.) Was subjected to solution treatment at a temperature of approximately 1,173K for 1 hour and quenched.

Thereafter, the quenched sample was cold worked to have a section reduction rate of 10 to 30%.

Finally, the cold worked samples were aged for 1 hour at a range of about 700K.

Ti Ni Nb Ni / Ti Comparative Example 7 50 50 0 One Example 15 48.5 48.5 3.0 One Example 16 47.0 47.0 6.0 One Example 17 45.5 45.5 9.0 One Example 18 44.0 44.0 12.0 One Example 19 42.5 42.5 15.0 One Example 20 46.4 47.6 6.0 1.025 Example 21 45.85 48.15 6.0 1.05 Comparative Example 8 45.3 48.7 6.0 1.075 Comparative Example 9 45.02 48.98 6.0 1.088 Comparative Example 10 43.58 47.42 9.0 1.088 Comparative Example 11 44.76 49.23 6.0 1.1

On the other hand, the transformation temperature, heat cycle and mechanical physical properties of the Ti-Ni-Nb type shape memory alloy wire fabricated in Examples 15 to 21 and Comparative Examples 7 to 11 were measured. In detail, the transformation temperature was measured by DSC at 30 to 50 mg, and the thermal cycle was measured at 10 K / min in the temperature range of 123 to 423K. Measurement of mechanical properties was carried out in the temperature range of 173 ~ 573K. The size of sample was 1mm in diameter and 70mm in length. The strain rate was 1.6% / min. All samples were maintained at Mf-30K temperature and then at As-20K, Af + 20K.

6 and 7, the dependence of the Ni / Ti ratio and the addition of the Nb element on the change in the martensitic transformation temperature will be described with reference to FIGS. 6 and 7. FIG. 6 and FIG. As shown above, the transformation temperatures of Mf, As and Af inclusive of the Ms temperature tend to decrease as described above. However, the degree of transformation temperature at the change of the content of Nb element in the immobilized Ni / Ti ratio was larger than that of the content of Nb element in the change of Ni / Ti ratio. For example, when the Ni / Ti ratio is changed, the Ms and Af temperature change widths are 90K and 60K, respectively. At the fixed Ni / Ti ratio, it is 65K and 50K, respectively.

The influence of the heat treatment temperature and the amount of cold working on the change of the transformation temperature characteristic will be described. In the process of manufacturing the TiNiNb shape memory ring, since the heat treatment process and the cold process are introduced, Considering changes in trends is a very important issue that directly affects manufacturing process design and production costs.

According to Fig. 8 (influence of the heat treatment temperature) and Fig. 9 (influence of the amount of cold working), when the Ni / Ti ratio is fixed to 1 and the heat treatment temperature is changed, there is hardly a change in the transformation temperature even when the content of the Nb element changes. However, when the Ni / Ti ratio is changed, the transformation temperature of each phase decreases when the heat treatment temperature is changed. When the heat treatment temperature rises to 773 K, the transformation temperature slightly increases but is lower than the transformation temperature in the solution treatment state. This is because the formation of the Ni-rich phase due to the aging effect results in a relatively large amount of Ti present in the matrix, resulting in an increase in temperature.

10, when the Ni / Ti ratio and the Nb element addition amount were varied with the amount of cold working, the change of the transformation temperature was larger when the Ni / Ti ratio was not constant. Particularly, when the Ni / Ti ratio is changed, the change of the transformation temperature is very large even at a cold processing amount of 10% or less. Judging from these results, it is preferable that the amount of cold working And it was found that it is advantageous to perform the heat treatment at about 773K so that the heat treatment temperature has a transformation temperature close to the solution treatment temperature.

11 shows the relationship between the content (a) of the Nb element and the Ni / Ti ratio (b) of the Ni / Ti ratio and the content of the Nb element ) Is a graph of the stress-strain curves tested on As-20K for a discussion of the effect of the change on mechanical properties. The graph shows that when the Ni / Ti ratio is greater than 1.075, the strength and strain tend to decrease, and below that, the work hardening rate is low even after M phase rearrangement. This is a very important result in that the actual product is deformed without easily hardening the workpiece on the M side. As the content of Nb element with constant Ni / Ti ratio increased, the strength increased and the strain rate decreased with increasing Nb element content. In addition, the tendency of the slope to be accelerated due to the rapid increase of the work hardening rate is presumed to be due to the formation of Nb-rich by the increase of the content of Nb, which prevents the rearrangement due to the stress of the martensite. From these results, it was judged that the Ni / Ti ratio would be 1.05 or less, and the content of Nb element would be 9at% or less at maximum.

Next, the effects of changes in the content of Ni / Ti and Nb elements on the mechanical properties will be described. The investigation of the fracture strength and strain shows that the TiNiNb ring product applied to the actual joint is deformed by a certain amount on the martensite, When applied, it should be restrained to the parent phase at high temperature and to exhibit binding force, so the breaking strength and strain rate of the two phases should be high. In order to investigate the effect of deformation on martensite on the amount of Ni / Ti and Nb elements, and the effect of the amount of cold working on the fracture strength and strain, 20K and Af + 20K, the temperature range in which the martensite (M) phase and the austenite (A) phase are present.

As shown in Figs. 12, 13, and 14, changes in the contents of Nb elements (Fig. 12), changes in Ni / Ti ratio (Fig. 13), and changes in introduction of cold working (Fig.

12, the fracture strength on the martensite is maintained at about 800 to 1,100 MPa even when the content of the Nb element is changed, but the elongation (strain amount) on the martensite is about 6 atoms % To 30% to 60%. When the content of Nb element is more than 6 atomic%, that is, when the content of Nb element is 9 atomic%, the elongation rate sharply decreases to 20% or less.

Further, referring to Fig. 12, it can be seen that the fracture strength on the austenite is maintained at about 800 to 1,100 MPa even when the content of the Nb element is changed. On the other hand, it can be seen that the elongation (strain) on the austenite maintains the content of the Nb element at about 30% to 60% up to about 9 atomic%, but when it exceeds 9 atomic% From this 12 atomic percent, it can be seen that the elongation rate sharply decreases to 20% or less.

FIG. 13 is a graph showing the influence on the Ni / Ti ratio change. As compared with FIG. 12 showing the effect on the addition of Nb element, the fracture strengths tend to be similar, but the elongation (fracture strain) .

In detail, the fracture strength on the martensite is maintained at about 800 to 1100 MPa when the Ni / Ti atomic ratio is 1.05 or less. When the Ni / Ti atomic ratio exceeds 1.05, the fracture strength is less than about 800 MPa, It can be seen that it decreases sharply as the self-sufficiency increases. In addition, the elongation (breakage strain) on the martensite is about 30 to 60% when the atomic ratio of Ni / Ti is 1.025, but when the atomic ratio of Ni / Ti is 1.05 or more, the elongation is sharply decreased to about 25% Able to know.

The fracture strength on the austenite phase is maintained at about 800 to 1100 MPa when the Ni / Ti atomic ratio is 1.05 or less. When the Ni / Ti atomic ratio exceeds 1.05, the fracture strength is less than about 800 MPa, Of the total amount of water. When the Ni / Ti atomic ratio exceeds 1.05, that is, when the Ni / Ti atomic ratio is 1.075, the elongation (break strain) on the austenite is in the range of about 30 to 60% And it is decreased to about 25%.

14 shows the determination strength and breaking strain according to the introduction of the cold working amount, and it is considered that the fracture strength increased by 200 MPa due to the increase of the slip critical stress due to introduction of the dislocation of the matrix, As the fracture strain tends to decrease at the same time, it is considered that the influence of introduction of cold worked amount before heat treatment is relatively irrelevant, and introduction of more than 10% Respectively.

These results show that the transformation temperature of martensite decreases with Ni / Ti content (Ni / Ti ratio is constant) and Ni / Ti change (Nb content is constant) The transformation temperature change is dependent on the change of the condition of the heat treatment process when the composition ratio of Ni / Ti is larger than 1. In the case where the composition ratio of Ni / Ti is 1, That is, the change in the physical properties such as the transformation temperature, etc. is more dependent on the change in the Ni / Ti composition ratio than the change in the content of Nb. Also, the change of martensite transformation temperature tended to decrease with increasing the amount of cold worked before heat treatment. After the solution treatment, the content of Nb increased by more than 6% in atomic ratio or the ratio of Ni / Ti increased by more than 1.05 The breakage strain on the martensite decreases, and the cold working of about 10% before the heat shrinkage is not useful because it rapidly decreases the fracture strain, and is not greatly influenced by the amount of cold working before heat treatment. Therefore, the guidelines for the content of Nb element, Ni / Ti ratio, and cold working amount for producing TiNiNb ring were less than 9%, less than 1.05, and less than about 10% before solution heat treatment, respectively.

A description will now be given of the manufacture of a wire for manufacturing a TiNiNb shape memory ring with reference to FIG. 15, in order to understand the degree of composition dependency of a TiNiNb shape memory material and to develop a TiNiNb wire serving as a raw material of a ring product in connection with the results of mechanical property analysis and process parameters And to analyze the wire manufacturing process. At the time of analysis, samples were prepared by dissolving -> machining -> standard sample preparation -> vacuum annealing -> heat treatment -> cold working.

For this reason, it can be said that the production process of TiNiNb shape memory ring finished product corresponds to the standard sample production process by dissolving -> mechanical machining -> ring semi-finished product processing -> vacuum heat treatment -> ring finished product. Considering the process, it is expected to be practically performed in the order shown in Fig. In other words, firstly, the shape memory alloy wire is used to manually torch the torch and then it is made into a spring shape -> externally fixed and then annealed by annealing -> cut by high speed cutter -> shape memory heat treatment ring memory -> (vacuum heat treatment) The process consisted of 10 processes such as surface treatment (including cutting) -> surface treatment of cutting surface -> argon welding -> expansion -> finished product, among which the dissolution process was performed by adding Ni / Ti ratio, According to the above analysis results and guidelines, it is considered that the order of the process is important because subsequent mechanical processing by Ni / Ti ratio may affect the characteristics of the TiNiNb shape memory wire. According to FIG. 15 Since the order of the actual processes is the same as that in the standard sample preparation process, the heat treatment and the vacuum heat treatment are changed, It is. In addition, the mass-production system for vacuum processing should be boldly omitted in terms of the unit cost of the finished product, the complexity of the process, and the effectiveness thereof. However, detailed investigation has not been conducted, It is judged that the validation process is necessary.

For example, in the present invention, a small amount of TiNiNb wire was attempted in consideration of the mass production process. The product was subjected to mechanical processing (rolling, drawing, heat treatment) to prepare a product having a diameter of 1 mm, and then tensile strength and deformation amount were measured according to the ASTM E8 standard without vacuum heat treatment and the result was compared with ASTM F 2063 As a result, the strains of 1,173 MPa and 10%, respectively, were observed, and additional characteristics as shape memory wires had to be evaluated. Further studies were required to produce products consistent with quality considering mass production rather than small amounts.

When manufacturing the TiNiNb shape memory wire is completed, the ring finished product is manufactured in the order of FIG. 15 as described above, and these processes are now all manufactured by a manual method. Shape memory alloys require constant control of the production process in the production process due to the property of changing the physical properties during processing. In the present manual production, quality deterioration (30% defective rate) and poor productivity (5,000 / month), it is decided to solve the problem of globalization. Thus, in the present invention, the passive manufacturing process of 10 processes is drastically shortened in the order of 4 processes, It is planned to produce prototypes with plasticity and consistency of dimensions. In other words, we plan to secure wire production technology for reduction of defective rate, increase of production, and cost reduction by automating process heat treatment process.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Those skilled in the art will recognize that many modifications and variations are possible in light of the above teachings.

Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

Claims (14)

42 to 50 atomic% of Ti, 0.1 to 15 atomic% of Nb, the balance Ni and other unavoidable impurities,
Ti-Ni-Nb based shape memory alloy characterized in that the Ni / Ti atomic ratio is 0.7 to 1.05.
The method according to claim 1,
Wherein the shape memory alloy comprises a matrix phase and a phase phase,
Wherein the matrix has an Ni / Ti atomic ratio of 1 to 1.05,
The Ti-Ni-Nb based shape memory alloy according to claim 1, wherein the Ni / Ti atomic ratio is 0.8 to 0.97.
The method according to claim 1,
Wherein the Nb is 9 atomic% or less, and the Ni / Ti atomic ratio is 1 to 1.05.
The method of claim 3,
Wherein the shape memory alloy has an elongation of 30% to 60%.
42 to 50 atomic% of Ti, 0.1 to 15 atomic% of Nb, the balance Ni and other unavoidable impurities,
Solubilizing the alloy base material obtained through the dissolving step, and
And quenching the solution-treated alloy base material,
Wherein the Ni / Ti atomic ratio is 0.7 to 1.05.
6. The method of claim 5,
Wherein the shape memory alloy comprises a matrix phase and a phase phase,
Wherein the matrix has an Ni / Ti atomic ratio of 1 to 1.05,
Wherein said process phase has a Ni / Ti atomic ratio of 0.8 to 0.97.
6. The method of claim 5,
Wherein the Nb is 9 atomic% or less, and the Ni / Ti atomic ratio is 1 to 1.05.
8. The method of claim 7,
Wherein the shape memory alloy has an elongation of 30% to 60%.
6. The method of claim 5,
Wherein the dissolving step comprises alternately laminating and melting the Ti ingot made of Ti and the Ni ingot made of Ni on the Nb ingot made of Nb.
6. The method of claim 5,
The shape memory alloy manufacturing method
Mechanically processing the alloy base material obtained through the dissolving step to produce a wire, and
And heat treating the wire at a temperature of 1050 to 1300 K. A method for producing a Ti-Ni-Nb based shape memory alloy,
11. The method of claim 10,
And after the quenching step, an aging heat treatment is performed at a temperature of 650 to 800 K. The method for producing a Ti-Ni-Nb based shape memory alloy according to claim 1,
12. The method of claim 11,
Further comprising a step of cold-working the wire between the quenching step and the aging heat treatment step.
13. The method of claim 12,
The method of manufacturing a Ti-Ni-Nb based shape memory alloy according to claim 1, wherein the wire has a sectional reduction ratio of 10% or less.
A heat-shrinkable ring for fixing a joint comprising the Ti-Ni-Nb type shape memory alloy according to any one of claims 1 to 4.

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