Shape memory alloy, preparation method thereof and door lock device comprising shape memory alloy

Abstract

The invention provides a shape memory alloy, a preparation method thereof and a door lock device comprising the shape memory alloy, and relates to the technical field of alloy materials. The shape memory alloy comprises the following elements in percentage by atomic number: 50-56% of Ti, 30-36% of Ni and the balance of Cu. By optimizing the components of the shape memory alloy, the intrinsic lattice difference of the shape memory alloy is reduced, and the phase change stability is improved, so that the anti-fatigue performance of the shape memory alloy is improved. The shape memory alloy can be applied to a door lock device, and the service life of a door lock is prolonged.

Description

Technical Field

[0001] This invention relates to the field of alloy materials technology, and in particular to a shape memory alloy, its preparation method, and a door lock device containing the same. Background Technology

[0002] Traditional household door locks generally use a coil magnetic structure. The basic principle of a coil magnetic door lock is that energizing the coil creates a magnetic field, attracting the iron core and thus locking the door. Coil magnetic door locks require constant power supply, resulting in high power consumption and increasing the risk of overheating and burnout. Furthermore, coil magnetic door locks face several reliability issues, such as: a loose coil causing no resistance in the lock mechanism; water ingress causing locking failure; a stuck coil causing unlocking timeouts; overheating of the positive temperature coefficient (PTC) spring leading to no signal; and arcing and carbon buildup between the contact plate and the coil's metal pin causing poor signal conduction. In short, traditional coil magnetic door locks suffer from complex structures, high manufacturing costs, high power consumption, slow release speeds, and inherent reliability concerns.

[0003] Shape memory effect refers to the phenomenon where a specific alloy, after being shaped at high temperature, cooled to a low-temperature martensitic transformation state (Mf), subjected to a certain limit of plastic deformation, and then heated back to a high-temperature parent phase state (Af), recovers its original shape before low-temperature deformation. Shape memory alloys (SMA) are materials composed of two or more metallic elements that possess shape memory effect through thermoelasticity and martensitic transformation and its inverse.

[0004] Shape memory alloys, due to their superior properties such as shape memory effect and superelasticity, are widely used in aerospace, mechanical electronics, biomedicine, bridge construction, automotive industry, and everyday life. To date, proven shape memory alloy systems include: Au-Cd, Ag-Cd, Cu-Zn, Cu-Zn-Al, Cu-Zn-Sn, Cu-Zn-Si, Cu-Sn, Cu-Zn-Ga, In-Ti, Au-Cu-Zn, NiAl, Fe-Pt, Ti-Ni, Ti-Ni-Pd, Ti-Nb, U-Nb, and Fe-Mn-Si. Among these, Ti-Ni-based shape memory alloys, with their rich phase transformation pathways and excellent processing performance, were the first shape memory alloys to achieve commercialization.

[0005] Shape memory alloy door locks utilize the shape memory effect for opening and closing. They consist of a conductive resistance wire made of shape memory alloy, which contracts in length when excited by current or temperature. Current excitation selectively locks or releases the door. Since no coil magnet or PTC component is needed, operating energy consumption and the risk of heat-related damage are reduced. However, commercial Ti-Ni alloy wires exhibit stress hysteresis during phase transformation, and the intrinsic energy dissipation due to the lattice difference between the austenite and martensite phases leads to poor fatigue resistance, ultimately causing door lock structural failure. This is one of the biggest problems limiting the application of shape memory alloys. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a shape memory alloy, its preparation method, and a door lock device incorporating the same. This shape memory alloy exhibits excellent fatigue resistance and can be applied to door lock devices to improve the service life of door locks.

[0007] In a first aspect, the present invention provides a shape memory alloy, the shape memory alloy comprising elements in the following atomic percentages:

[0008] Ti: 50-56%, Ni: 30-36%, and the balance Cu.

[0009] In some embodiments of the present invention, the shape memory alloy further includes element X, wherein element X is Co and / or Al.

[0010] In some embodiments of the present invention, the atomic percentage of element X is 1-2%.

[0011] In some embodiments of the present invention, the shape memory alloy comprises elements with the following atomic percentages:

[0012] Ti: 51-54%, Ni: 32-35%, Cu: 10-14%, and X: 1-2%; element X is Co and / or Al.

[0013] In a second aspect, the present invention provides a method for preparing a shape memory alloy as described in the first aspect, the method comprising the following steps:

[0014] (1) Mix the metal raw materials of shape memory alloy, melt them, and cool them to obtain the first alloy blank;

[0015] (2) The first alloy blank is homogenized to obtain the second alloy blank;

[0016] (3) The second alloy blank is subjected to aging treatment to obtain an alloy ingot;

[0017] (4) The alloy ingot is processed into the required shape to obtain the shape memory alloy finished product.

[0018] In some embodiments of the present invention, the melting method is vacuum arc melting.

[0019] In some embodiments of the present invention, the homogenization treatment temperature is 840-940°C.

[0020] In some embodiments of the present invention, the homogenization process takes 20-26 hours.

[0021] In some embodiments of the present invention, the aging treatment temperature is 550-650°C.

[0022] In some embodiments of the present invention, the aging process takes 0.5-1.5 hours.

[0023] In some embodiments of the present invention, the shape memory alloy finished product is a shape memory alloy wire, and the step of processing the alloy ingot into the desired shape includes:

[0024] The alloy ingot is hot-drawn at 500-700℃ until the wire diameter reaches 130-140% of the preset diameter of the shape memory alloy wire; then, it is cold-drawn at 100-200℃ at least 3 times until the wire diameter reaches the preset diameter of the shape memory alloy wire. After each cold drawing, the wire is annealed at 650-800℃ for 15-30 minutes.

[0025] In some embodiments of the present invention, the cold drawing of the wire is performed 3-4 times.

[0026] In some embodiments of the present invention, in each cold-drawn wire, the change in wire diameter is less than 15% of the preset diameter of the shape memory alloy wire.

[0027] In some embodiments of the present invention, the drawing rate of the cold-drawn wire is 3-9 m / min.

[0028] Thirdly, the present invention provides a door lock device, the door lock device comprising a conductive resistance wire, the material of which is the shape memory alloy described in the first aspect, or the shape memory alloy prepared by the preparation method described in the second aspect.

[0029] The technical solution provided by the embodiments of the present invention has the following advantages compared with the prior art:

[0030] This invention optimizes the alloy composition by combining the various components in specific proportions, reducing the intrinsic lattice difference (austenite and martensite phases) in the Ti-Ni-based shape memory alloy, thus improving phase transformation stability and consequently enhancing the fatigue resistance of the shape memory alloy. This shape memory alloy can be applied to door lock devices to extend the service life of the locks. Attached Figure Description

[0031] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 The stress-strain curve of the shape memory alloy wire provided in Embodiment 1 of the present invention;

[0034] Figure 2 This is a stress-strain curve diagram of a shape memory alloy wire provided in Embodiment 2 of the present invention;

[0035] Figure 3 This is a stress-strain curve diagram of the shape memory alloy wire provided in Embodiment 3 of the present invention;

[0036] Figure 4 The stress-strain curve of the shape memory alloy wire provided in Embodiment 4 of the present invention;

[0037] Figure 5 The stress-strain curve of the shape memory alloy wire provided in Embodiment 5 of the present invention. Detailed Implementation

[0038] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0039] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application.

[0041] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0042] In a first aspect, embodiments of the present invention provide a shape memory alloy, the shape memory alloy comprising elements in the following atomic percentages:

[0043] Ti: 50-56%, Ni: 30-36%, and the balance Cu.

[0044] The atomic percentage of Ti can be 50%, 51.5%, 52%, 52.5%, 53%, 53.5%, 54%, 54.5%, 55%, 55.5%, or 56%, etc. However, the present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0045] The atomic percentage of Ni can be 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, 33.5%, 34%, 34.5%, 35%, 35.5%, or 36%, etc. However, the present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0046] This invention optimizes the alloy composition by selecting Ti, Ni, and Cu in the above-mentioned proportions to reduce the intrinsic lattice (austenite parent phase and martensite phase) difference in Ti-Ni based shape memory alloys. During the transformation of austenite to martensite, a coherent intermediate phase of Ti2Cu is generated, which improves the phase transformation stability, thereby improving the fatigue resistance of shape memory alloys and extending their fatigue life.

[0047] In some embodiments of the present invention, the shape memory alloy further includes element X, wherein element X is Co and / or Al, preferably Co.

[0048] In some embodiments of the present invention, the atomic percentage of element X is 1-2%, for example, it can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%, etc. However, the present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0049] This invention, through the further introduction of Co and / or Al into the shape memory alloy, utilizes the pinning effect of Ti₂Cu and Co and / or Al elements to further improve the phase transformation stability of the alloy, thereby further enhancing its fatigue resistance. However, if the content of Co and / or Al is too high, it will lead to an increase in the precipitation of intermetallic compounds, affecting the overall mechanical properties of the alloy. In addition, the composition of the original precipitates will also change, affecting the shape memory effect.

[0050] In some embodiments of the present invention, the shape memory alloy comprises elements with the following atomic percentages:

[0051] Ti: 50-56%, Ni: 30-36%, Cu: 10-14%, and X: 1-2%; element X is Co and / or Al.

[0052] In some embodiments of the present invention, the shape memory alloy comprises elements with the following atomic percentages:

[0053] Ti: 51-54%, Ni: 32-35%, Cu: 10-14%, and X: 1-2%; element X is Co and / or Al.

[0054] The atomic percentage of Ti can be 51.5%, 51.8%, 52%, 52.2%, 52.5%, 52.8%, 53%, 53.2%, 53.5%, 53.8%, or 54%, etc. However, the present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0055] The atomic percentage of Ni can be 32%, 32.2%, 32.5%, 32.8%, 33%, 33.2%, 33.5%, 33.8%, 34%, 34.2%, 34.5%, 34.8%, or 35%, etc. However, the present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0056] The atomic percentage of Cu can be 10%, 10.2%, 10.5%, 10.8%, 11%, 11.2%, 11.5%, 11.8%, 12%, 12.2%, 12.5%, 12.8%, 13%, 13.2%, 13.5%, 13.8%, or 14%, etc. However, the present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0057] The percentage of atoms of X can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%, etc. However, the present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0058] In a second aspect, the present invention provides a method for preparing a shape memory alloy as described in the first aspect, the method comprising the following steps:

[0059] (1) Mix the metal raw materials of shape memory alloy, melt them, and cool them to obtain the first alloy blank;

[0060] (2) The first alloy blank is homogenized to obtain the second alloy blank;

[0061] (3) The second alloy blank is subjected to aging treatment to obtain an alloy ingot;

[0062] (4) The alloy ingot is processed into the required shape to obtain the shape memory alloy finished product.

[0063] In some embodiments of the present invention, the melting method is vacuum arc melting.

[0064] In some embodiments of the present invention, the homogenization treatment temperature is 840-940℃; for example, it can be 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, or 940℃, etc. However, the present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0065] In some embodiments of the present invention, the homogenization process takes 20-26 hours; for example, it can be 20 hours, 21 hours, 22 hours, 23 hours, 24 hours, 25 hours, or 26 hours. However, the present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0066] In some embodiments of the present invention, the aging treatment temperature is 550-650℃; for example, it can be 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃, or 650℃, etc. However, the present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0067] In some embodiments of the present invention, the aging process takes 0.5-1.5 hours; for example, it can be 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours, 1 hour, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, or 1.5 hours. However, the present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0068] In some embodiments of the present invention, the shape memory alloy finished product is a shape memory alloy wire, and the step of processing the alloy ingot into the desired shape includes:

[0069] The alloy ingot is hot-drawn at 500-700℃ (e.g., 500℃, 520℃, 550℃, 580℃, 600℃, 620℃, 650℃, 680℃, or 700℃, etc.) until the wire diameter reaches 130-140% (e.g., 130%, 132%, 133%, 135%, 136%, 138%, or 140%, etc.) of the preset diameter of the shape memory alloy wire; then it is hot-drawn at 100-200℃ (e.g., 100℃, 110℃, 120℃, 130℃, 140℃, etc.). The wire is cold-drawn at least three times at 150℃, 160℃, 170℃, 180℃, 190℃ or 200℃, etc., until the wire diameter reaches the preset diameter of the shape memory alloy wire. After each cold drawing, the wire is annealed at 650-800℃ (e.g., 650℃, 680℃, 700℃, 720℃, 750℃, 780℃ or 800℃, etc.) for 15-30 minutes (e.g., 15 minutes, 18 minutes, 20 minutes, 22 minutes, 25 minutes, 28 minutes or 30 minutes, etc.).

[0070] In some embodiments of the present invention, the cold drawing of the wire is performed 3-4 times.

[0071] In some embodiments of the present invention, the change in wire diameter in each cold-drawn wire is less than 15% of the preset diameter of the shape memory alloy wire; for example, it can be 15%, 12%, 10%, 8%, 5%, or 3%, etc. However, the present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0072] In some embodiments of the present invention, the drawing rate of the cold-drawn wire is 3-9 m / min; for example, it can be 3 m / min, 4 m / min, 5 m / min, 6 m / min, 7 m / min, 8 m / min, or 9 m / min, etc. However, the present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0073] In this embodiment of the invention, by optimizing the preparation process of shape memory alloys, it is helpful to further reduce the intrinsic lattice (austenite parent phase and martensite phase) difference and further improve the fatigue resistance of shape memory alloys.

[0074] Thirdly, the present invention provides a door lock device, the door lock device comprising a conductive resistance wire, the material of which is the shape memory alloy described in the first aspect, or the shape memory alloy prepared by the preparation method described in the second aspect.

[0075] The shape memory alloy provided in this invention has good fatigue resistance. When applied to door lock devices, it can improve the service life and reliability of the door lock devices.

[0076] To make the technical problems solved, technical solutions, and beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0077] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with conventional techniques or conditions in the art, techniques or conditions described in the literature, or product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0078] In the following embodiments, the chemical formula of the shape memory alloy is represented by Ti. a Ni b Cu c Co d Al e The subscripts represent the atomic percentage of that element in the shape memory alloy, i.e., Ti has an atomic percentage of a%, Ni has an atomic percentage of b%, Cu has an atomic percentage of c%, Co has an atomic percentage of d%, and Al has an atomic percentage of e%.

[0079] Example 1

[0080] This embodiment provides a shape memory alloy wire with the chemical formula Ti. 51 Ni 36 Cu 13 .

[0081] The method for preparing the shape memory alloy described in this embodiment is as follows:

[0082] (1) Mix the metal raw materials of shape memory alloy, perform vacuum arc melting, and cool to obtain the first alloy billet;

[0083] (2) The first alloy blank is homogenized at 840°C for 26 hours to obtain the second alloy blank;

[0084] (3) The second alloy billet is aged at 550°C for 1.5 hours to obtain an alloy ingot;

[0085] (4) The alloy ingot is hot-drawn at 550°C until the wire diameter reaches 130% of the preset diameter of the shape memory alloy wire; then it is cold-drawn three times at 100°C. The deformation of the wire (i.e., the change in wire diameter to the preset diameter of the shape memory alloy wire) is 10% in each cold drawing. After each cold drawing, the wire is annealed at 700°C for 20 minutes to form a shape memory alloy wire.

[0086] Example 2

[0087] This embodiment provides a shape memory alloy wire with the chemical formula Ti. 54 Ni 34 Cu 12 .

[0088] The method for preparing the shape memory alloy described in this embodiment is as follows:

[0089] (1) Mix the metal raw materials of shape memory alloy, perform vacuum arc melting, and cool to obtain the first alloy billet;

[0090] (2) The first alloy blank is homogenized at 940°C for 20 hours to obtain the second alloy blank;

[0091] (3) The second alloy billet is aged at 650°C for 0.5 h to obtain an alloy ingot;

[0092] (4) The alloy ingot is hot-drawn at 650°C until the wire diameter reaches 130% of the preset diameter of the shape memory alloy wire; then it is cold-drawn three times at 200°C, with the wire deformation amount being 10% in each cold drawing. After each cold drawing, the wire is annealed at 650°C for 30 minutes to form a shape memory alloy wire.

[0093] Example 3

[0094] This embodiment provides a shape memory alloy wire with the chemical formula Ti. 51 Ni 35 Cu 12 Co2.

[0095] The method for preparing the shape memory alloy described in this embodiment is as follows:

[0096] (1) Mix the metal raw materials of shape memory alloy, perform vacuum arc melting, and cool to obtain the first alloy billet;

[0097] (2) The first alloy blank is homogenized at 890°C for 24 hours to obtain the second alloy blank;

[0098] (3) The second alloy billet is aged at 600°C for 1 hour to obtain an alloy ingot;

[0099] (4) The alloy ingot is hot-drawn at 600°C until the wire diameter reaches 130% of the preset diameter of the shape memory alloy wire; then it is cold-drawn three times at 150°C, with the wire deformation amount being 10% in each cold drawing. After each cold drawing, the wire is annealed at 800°C for 15 minutes to form a shape memory alloy wire.

[0100] Example 4

[0101] This embodiment provides a shape memory alloy wire with the chemical formula Ti. 53 Ni 33 Cu 12 Co2.

[0102] The method for preparing the shape memory alloy described in this embodiment is as follows:

[0103] (1) Mix the metal raw materials of shape memory alloy, perform vacuum arc melting, and cool to obtain the first alloy billet;

[0104] (2) The first alloy blank is homogenized at 860°C for 25 hours to obtain the second alloy blank;

[0105] (3) The second alloy billet is aged at 580°C for 1.2 hours to obtain an alloy ingot;

[0106] (4) The alloy ingot is hot-drawn at 500°C until the wire diameter reaches 130% of the preset diameter of the shape memory alloy wire; then it is cold-drawn three times at 120°C, with the wire deformation amount being 10% in each cold drawing. After each cold drawing, the wire is annealed at 750°C for 15 minutes to form a shape memory alloy wire.

[0107] Example 5

[0108] This embodiment provides a shape memory alloy wire with the chemical formula Ti. 54 Ni 32 Cu 12 Co2.

[0109] The method for preparing the shape memory alloy described in this embodiment is as follows:

[0110] (1) Mix the metal raw materials of shape memory alloy, perform vacuum arc melting, and cool to obtain the first alloy billet;

[0111] (2) The first alloy blank is homogenized at 920°C for 22 hours to obtain the second alloy blank;

[0112] (3) The second alloy billet is aged at 620°C for 0.8 hours to obtain an alloy ingot;

[0113] (4) The alloy ingot is hot-drawn at 700°C until the wire diameter reaches 130% of the preset diameter of the shape memory alloy wire; then it is cold-drawn three times at 100°C, with the wire deformation amount being 10% in each cold drawing. After each cold drawing, the wire is annealed at 700°C for 15 minutes to form a shape memory alloy wire.

[0114] Example 6

[0115] This embodiment provides a shape memory alloy wire, which differs from Embodiment 3 only in that its chemical formula is Ti. 54 Ni 33 Cu 11 Co2.

[0116] Example 7

[0117] This embodiment provides a shape memory alloy wire, which differs from Embodiment 3 only in that its chemical formula is Ti. 50 Ni 30 Cu 18 Co2.

[0118] Example 8

[0119] This embodiment provides a shape memory alloy wire, which differs from Embodiment 3 only in that its chemical formula is Ti. 56 Ni 36 Cu6Co2.

[0120] Example 9

[0121] This embodiment provides a shape memory alloy wire, which differs from Embodiment 3 only in that its chemical formula is Ti. 50 Ni 36 Cu 12 Co2.

[0122] Example 10

[0123] This embodiment provides a shape memory alloy wire, which differs from Embodiment 3 only in that its chemical formula is Ti. 56 Ni 30 Cu 12 Co2.

[0124] Example 11

[0125] This embodiment provides a shape memory alloy wire, which differs from Embodiment 3 only in that its chemical formula is Ti. 54 Ni 35 Cu 10 Co1.

[0126] Example 12

[0127] This embodiment provides a shape memory alloy wire, which differs from Embodiment 3 only in that its chemical formula is Ti. 52 Ni 32.5 Cu 14 Co 1.5 .

[0128] Example 13

[0129] This embodiment provides a shape memory alloy wire, which differs from Embodiment 3 only in that its chemical formula is Ti. 51 Ni 35 Cu 12 Al2.

[0130] Example 14

[0131] This embodiment provides a shape memory alloy wire, which differs from Embodiment 3 only in that its chemical formula is Ti. 51 Ni 34 Cu 12 Co3.

[0132] Comparative Example 1

[0133] This embodiment provides a shape memory alloy wire, which differs from Embodiment 3 only in that its chemical formula is Ti. 48 Ni 38 Cu 12 Co2.

[0134] Comparative Example 2

[0135] This embodiment provides a shape memory alloy wire, which differs from Embodiment 3 only in that its chemical formula is Ti. 58 Ni 28 Cu 12 Co2.

[0136] Comparative Example 3

[0137] This embodiment provides a shape memory alloy wire, which differs from Embodiment 3 only in that its chemical formula is Ti. 51 Ni 38 Cu9Co2.

[0138] Performance testing

[0139] The fatigue resistance of the shape memory alloy wires provided in the above examples and comparative examples was tested according to the "Tensive Testing Method for Non-ferrous Metal Wires" (GB / T 10573-2020). The test diameter of the alloy wire was 0.3 mm. The stress-strain curves of the alloy wires were obtained from the tests. The fatigue resistance was characterized by the number of cycles in which the hysteresis loop remained unchanged. The greater the number of cycles, the better the fatigue resistance.

[0140] The stress-strain curves of the shape memory alloy wires provided in Examples 1-5 are shown below. Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 As shown in Table 1 below, the performance test data is as follows.

[0141] Table 1

[0142]

[0143]

[0144] Among them, the shape memory alloy Ti provided in Example 1 51 Ni 36 Cu 13 The martensitic phase transformation process does not involve the intermediate phase, resulting in the worst fatigue resistance. Example 2 provides a shape memory alloy Ti... 54 Ni 34 Cu 12 During the transformation of austenite into martensite, a coherent intermediate phase of Ti2Cu is generated. This intermediate phase can improve the phase transformation stability of the alloy, thus its fatigue resistance is improved compared with Example 1.

[0145] The shape memory alloys provided in Examples 3-14 introduce Co or Al elements. The pinning effect of the precipitated phase Ti2Cu and Co or Al elements further improves the phase transformation stability of the alloy, thus its fatigue resistance is significantly improved compared with Examples 1-2.

[0146] Compared with Example 3, the shape memory alloy provided in Example 14 has a higher Co content, which leads to an increase in the precipitation of intermetallic compounds and changes in the composition of the precipitates, thus reducing its fatigue resistance.

[0147] Compared with Example 3, the Ti content in the shape memory alloy wire provided in Comparative Example 1 is too low and the Ni content is too high; the Ti content in the shape memory alloy wire provided in Comparative Example 2 is too high and the Ni content is too low; the Ni content in the shape memory alloy wire provided in Comparative Example 3 is too high and the Cu content is too low. These factors affect the synergistic relationship between the elements and all lead to a significant decrease in the fatigue resistance of the shape memory alloy wire.

[0148] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A shape memory alloy, characterized in that, The shape memory alloy comprises elements in the following atomic percentages: Ti: 50-56%, Ni: 30-36%, and the balance Cu.

2. The shape memory alloy according to claim 1, characterized in that, The shape memory alloy further includes element X, wherein element X is Co and / or Al; Preferably, the atomic percentage of element X is 1-2%.

3. The shape memory alloy according to claim 1 or 2, characterized in that, The shape memory alloy comprises elements in the following atomic percentages: Ti: 51-54%, Ni: 32-35%, Cu: 10-14%, and X: 1-2%; element X is Co and / or Al.

4. A method for preparing a shape memory alloy as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: (1) Mix the metal raw materials of shape memory alloy, melt them, and cool them to obtain the first alloy blank; (2) The first alloy blank is homogenized to obtain the second alloy blank; (3) The second alloy blank is subjected to aging treatment to obtain an alloy ingot; (4) The alloy ingot is processed into the required shape to obtain the shape memory alloy finished product.

5. The preparation method according to claim 4, characterized in that, The melting method is vacuum arc melting.

6. The preparation method according to claim 4 or 5, characterized in that, The homogenization process is performed at a temperature of 840-940℃. Preferably, the homogenization process takes 20-26 hours.

7. The preparation method according to any one of claims 4-6, characterized in that, The aging treatment temperature is 550-650℃; Preferably, the aging process takes 0.5-1.5 hours.

8. The preparation method according to any one of claims 4-7, characterized in that, The shape memory alloy finished product is a shape memory alloy wire, and the step of processing the alloy ingot into the desired shape includes: The alloy ingot is hot-drawn at 500-700℃ until the wire diameter reaches 130-140% of the preset diameter of the shape memory alloy wire; then, it is cold-drawn at 100-200℃ at least 3 times until the wire diameter reaches the preset diameter of the shape memory alloy wire. After each cold drawing, the wire is annealed at 650-800℃ for 15-30 minutes.

9. The preparation method according to claim 8, characterized in that, The number of cold drawing cycles is 3-4. Preferably, in each cold-drawn wire, the change in wire diameter is less than 15% of the preset diameter of the shape memory alloy wire; Preferably, the drawing rate of the cold-drawn wire is 3-9 m / min.

10. A door lock device, characterized in that, The door lock device includes a conductive resistance wire, the material of which is the shape memory alloy as described in any one of claims 1-3, or the shape memory alloy prepared by the preparation method described in any one of claims 4-9.

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