Nickel-titanium alloy, its manufacturing method and application

Abstract

The present invention relates to a nickel-titanium alloy, its manufacturing method, and its applications. The nickel-titanium alloy contains titanium, nickel, copper, and optional cobalt, and the weight ratios of titanium, nickel, copper, and optional cobalt to the total weight of the nickel-titanium alloy are 38% to 47%, 35% to 50%, 3% to 20%, and 0% to 5%, respectively. The nickel-titanium alloy exhibits no structural fatigue and / or functional fatigue even after at least 10 million loading-unloading cyclic phase change cycles.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority from Chinese Patent Application No. 2023101853053, the entire contents of which are incorporated herein by reference.

[0002] (Technical field) The present invention relates to the field of functional alloys, and in particular to a nickel-titanium-based shape memory alloy, its manufacturing method and its application. The nickel-titanium-based alloy of the present invention is a functional material that exhibits a reversible martensitic phase change, and the martensitic phase change can be induced by temperature or stress, and can accordingly exhibit shape memory effect and superelasticity. [Background technology]

[0003] The main problem with conventional industrially produced nickel-titanium alloys is their high phase change stress and poor stability during cyclic phase change. Polycrystalline or crystalline-amorphous composite nickel-titanium alloys generally require a compressive stress of 900-1800 MPa to achieve a complete martensitic phase change. During cyclic phase change, the phase change performance of nickel-titanium alloys decreases with increasing cycle counts, primarily manifested as a decrease in phase change stress and hysteresis area and an increase in residual strain. This deterioration in performance with increasing cycle counts can ultimately lead to a complete loss of superelasticity, i.e., functional fatigue.

[0004] The lack of strength of conventional nickel-titanium alloys and the incompatibility of the austenite-martensite phase boundary lead to the generation and slippage of dislocations that induce phase changes. These dislocations also inhibit the reverse phase transformation of martensite, resulting in residual martensite, which leads to fatigue in nickel-titanium alloys. This is usually accompanied by crack nucleation and propagation, which can lead to failure of the material, i.e., structural fatigue, before the nickel-titanium alloy completely loses its phase transformation function. Taking solid-state elastocaloric refrigeration as an example, a refrigeration air conditioner based on a shape memory alloy requires approximately 78 million cycles for a 10-year service life (operating 12 hours a day, 6 months a year at an operating frequency of 1 Hz). However, most shape memory alloys, including nickel-titanium, have yet to meet this requirement.

[0005] Therefore, there remains a need for nickel-titanium based alloys with improved performance, particularly nickel-titanium based shape memory alloys with improved cyclic phase change stability. Summary of the Invention [Means for solving the problem]

[0006] To solve the above problems, the present invention provides a new type of nickel-titanium based shape memory alloy, a method for manufacturing the nickel-titanium based shape memory alloy, and its applications in biomedical materials, solid-state elastocaloric cooling components, aerospace components, mechanical engineering components, automotive components, and / or architectural components, etc. The alloy exhibits high strength and excellent superelasticity, and exhibits a unique combination of excellent cyclic phase change stability and reduced phase change stress.

[0007] In particular embodiments, the nickel-titanium based alloy undergoes at least 10 million cyclic phase change cycles at compressive stresses of 350-700 MPa without any appreciable change in the stress-strain curve.

[0008] Specifically, the present invention provides the following:

[0009] 1. A nickel-titanium alloy containing titanium, nickel, copper, and optional cobalt, wherein the weight ratios of titanium, nickel, copper, and optional cobalt to the total weight of the nickel-titanium alloy are: Titanium 38%~47% Nickel 35%~50%, Copper 3%~20%, Cobalt 0-5% The nickel-titanium alloy undergoes at least 10 million loading-unloading cyclic phase change cycles without experiencing structural fatigue and / or significant functional fatigue. Nickel-titanium alloy.

[0010] Preferably, the nickel-titanium based alloy does not suffer from structural and / or functional fatigue after at least 10 million loading-unloading phase change cycles at a compressive stress of 350-700 MPa, preferably 550-700 MPa.

[0011] Preferably, the microstructure of the nickel-titanium based alloy includes a Ti(Ni, Cu)2 precipitate phase.

[0012] Preferably, the microstructure contains 5% to 60% by volume of the Ti(Ni, Cu)2 precipitate phase, based on the total volume.

[0013] Preferably, the thickness of the Ti(Ni, Cu)2 precipitate phase is 1 to 20 nm, preferably 1 nm, and the diameter is 10 to 500 nm.

[0014] Preferably, the nickel-titanium alloy comprises: Titanium 38%~47% Nickel 30% to 50% 4-20% copper, and Contains 0.1 to 5% cobalt.

[0015] Preferably, the nickel-titanium alloy further contains unavoidable impurities, including carbon≦0.012 wt%, iron≦0.015 wt%, sulfur≦0.001 wt%, silicon≦0.01 wt%, manganese≦0.008 wt%, zinc≦0.005 wt%, lead+tin+magnesium+bismuth≦0.002 wt%, oxygen+nitrogen≦0.1 wt%, and hydrogen≦0.001 wt%, with the total amount of impurities being ≦0.5 wt%, in addition to other small amounts of additive elements and unavoidable impurities.

[0016] Preferably, the nickel-titanium based alloy comprises: The raw materials containing titanium, nickel, copper and optional cobalt are melted and manufactured as an alloy. performing a plastic deformation treatment to apply a total strain of 1% to 60% to the alloy from one to three directions; The alloy is plastically deformed and then heat treated and quenched to obtain a nickel-titanium alloy.

[0017] 2. (i) melting and preparing an alloy sample from raw materials containing titanium, nickel, copper, and optionally cobalt; (ii) performing a plastic deformation treatment on the alloy sample from one to three directions to apply a total strain of 1% to 60%; (iii) heat treating and quenching the alloy sample after the plastic deformation treatment to obtain a nickel-titanium based alloy. A method for producing nickel-titanium alloys.

[0018] Preferably, the method for producing a nickel-titanium based alloy further comprises, prior to step (i), the step of mixing raw materials of titanium, nickel, copper and optionally cobalt.

[0019] Preferably, the method for producing a nickel-titanium alloy further comprises, before step (ii), a step of cutting the melt-prepared alloy sample into a cube, a rectangle, or a cylinder, and step (ii) comprises a plastic deformation treatment of applying a total strain of 1% to 60% to the cube, rectangle, or cylinder from one to three directions.

[0020] Preferably, the cutting is at least one selected from wire cutting, diamond electric saw cutting, and laser cutting.

[0021] Preferably, step (iii) comprises carrying out the heat treatment under conditions in which the temperature is set to 350 to 700° C. and the time is set to 0.1 to 3 hours, and quenching by immersion in water immediately after the heat treatment.

[0022] Preferably, step (i) comprises evacuating an arc melting furnace or induction melting furnace, then passing high purity argon gas having a purity of ≥ 99%, and then melting and fabricating raw materials containing titanium, nickel, copper and optionally cobalt as an alloy.

[0023] Preferably, the arc melting current is 150 to 1000 A, Preferably, the arc-melted sample may be button-shaped, with a diameter of 5 to 100 mm and a thickness of 5 to 60 mm, or the arc-melted and suction-cast sample may be cylindrical rod-shaped, with a diameter of 5 to 20 mm and a height of 100 to 200 mm.

[0024] Preferably, the induction melting furnace has a current of 200 to 300 A and an oscillation frequency of 1 to 80 KHz; Preferably, the induction melt fabricated sample is a cylindrical rod with a diameter of 5 to 100 mm and a height of 50 to 400 mm.

[0025] 3. A product comprising a nickel-titanium-based alloy, wherein the nickel-titanium-based alloy is any of the nickel-titanium-based alloys described above, or a nickel-titanium-based alloy produced by any of the methods described above.

[0026] Preferably, the article is at least one selected from a biomedical device, a solid state elastocaloric cooling member, a joint, a fastener, a damping energy dissipation device, an antenna, an electromechanical actuator member, and an automotive member.

[0027] Preferably, the solid-state elastocaloric cooling member is capable of producing a temperature drop of at least 10° C. upon unloading at a compressive stress of 350 to 700 MPa.

[0028] Applications of the nickel-titanium based alloy according to any of the above, or produced by any of the above methods, in biomedical materials, solid-state elastocaloric cooling components, aerospace components, mechanical engineering components, automotive components and / or building components.

[0029] Preferably, in a cyclic stress-strain curve test, the nickel-titanium alloy undergoes at least 10 million cyclic phase change cycles at a compressive stress of 350-700 MPa without any significant change in the stress-strain curve, i.e., the residual strain after the 10 millionth cycle of compressive deformation does not exceed 1%, preferably does not exceed 0.2%, the change in phase change stress does not exceed 25%, preferably does not exceed 3%, and the change in hysteresis area does not exceed 30%, preferably does not exceed 10%, compared to the first cycle.

[0030] The novel titanium-nickel alloy of the present invention has a large amount of nano-sized Ti(Ni,Cu)2 precipitates in its microstructure, and preferably contains 5% to 60% by volume of Ti(Ni,Cu)2 precipitates.

[0031] Preferably, the thickness of the Ti(Ni, Cu)2 precipitate phase is 1 to 20 nm, preferably 1 nm, and the diameter is 10 to 500 nm.

[0032] This suppresses the occurrence of dislocations through the strengthening effect of the precipitate phase, and promotes martensite phase transformation through the coherent strain and stress between the precipitate phase and the substrate, thereby improving the stability of the cyclic phase transformation and reducing the phase transformation stress.

[0033] These and other non-limiting features of the present disclosure are more particularly disclosed below. [Brief explanation of the drawings]

[0034] The following is a brief description of the drawings, which are intended to illustrate, but not to limit, exemplary embodiments disclosed herein.

[0035] [Figure 1] 1 is a flowchart of a part of a process for producing a titanium-nickel alloy by a three-axis forging process according to one embodiment of the present invention, in which 11, 12, and 13 are an upper pressing member, a rectangular sample, and a lower pressing member, respectively. [Figure 2] 1 is a flowchart of a part of a method for producing a titanium-nickel alloy by a single-axis forging process according to another embodiment of the present invention, in which 21, 22, and 23 are an upper pressing member, a cylindrical sample, and a lower pressing member, respectively. [Figure 3] 1 is a photograph of the microstructure of a titanium-nickel alloy according to an embodiment of the present invention after melting, forging, and heat treatment, where 31 and 32 are the TiNiCuCo substrate and the Ti(Ni, Cu)2 precipitate phase, respectively. [Figure 4] 4 shows the stress-strain curves under cyclic deformation of the titanium-nickel alloy according to Example 1 of the present invention after melting, forging, and heat treatment. 41, 42, 43, 44, and 45 are the phase change stress, residual strain, hysteresis area, stress-strain curve for the first cycle, and stress-strain curve for the 10,000,000 cycle, respectively. DETAILED DESCRIPTION OF THE INVENTION

[0036] The components, methods, and apparatus disclosed herein can be more fully understood with reference to the drawings, which are illustrative only and are not intended to represent the relative size and dimensions of the devices or their components and / or to limit or restrict the scope of the exemplary implementations, in order to facilitate explanation of the invention.

[0037] For the sake of clarity, specific terms are used in the following description, but these terms refer only to the specific structure of the implementations selected for illustrative purposes in the drawings and are not intended to limit or restrict the scope of the present disclosure. In the drawings and the following description, like numeral designations should be understood to refer to components having similar functions.

[0038] Unless expressly stated otherwise, the singular forms "a," "an," "one," and "the" may include plural referents.

[0039] Numerical values ​​in the specification and claims of this application should be understood to include identical values ​​when reduced to the same number of significant digits, and values ​​where the difference between said values ​​is less than the testing error for determining such values ​​using routine measurement techniques of the type described herein.

[0040] All ranges disclosed herein are inclusive of the recited endpoints and are independently combinable (e.g., the range "2 g to 10 g" includes the endpoints 2 g and 10 g, and also includes all intermediate values).

[0041] Values ​​modified by one or more terms (e.g., "about" or "essentially") are not limited to the exact value specified. Terms used to express approximations are consistent with the precision of the instrument used to measure the value. The modifier "about" should be considered to disclose a range defined by the absolute values ​​of the two endpoints. For example, the phrase "about 2 to about 4" further discloses the range "2 to 4."

[0042] The present invention is concerned with temperature ranges, which refer to the ambient temperature to which the alloy is exposed or the set temperature of the furnace, and the alloy itself does not need to reach these temperatures.

[0043] As used herein, the term "structural fatigue" refers to the nucleation and propagation of cracks due to the lack of strength and incompatibility of the austenite-martensite phase boundary in nickel-titanium based alloys, resulting in failure of the material due to crack propagation before the alloy completely loses its phase change function.

[0044] The term "functional fatigue" as used herein refers to the deterioration of phase change performance with an increase in the number of cycles during cyclic phase change in nickel-titanium alloys, which is manifested primarily in a decrease in phase change stress and hysteresis area and an increase in residual strain. This deterioration in performance with an increase in cycles may ultimately lead to a complete loss of superelasticity, i.e., functional fatigue.

[0045] As used herein, the term "cyclic phase change cycle" refers to the number of times a material undergoes a stress-induced, reversible austenite-martensite phase change. For example, when an appropriate stress is applied, the material changes from austenite to martensite, and then, after the stress is released, the material changes from martensite to austenite; this cycle constitutes one cycle.

[0046] The term "Ti(Ni,Cu)2 precipitates" as used herein refers to island-like nanostructures (secondary phases precipitated from the initial substrate at a specific temperature, usually without phase change function) dispersed in a continuous phase (e.g., a TiNiCuCo substrate continuous phase with phase change function) in the microstructural phase diagram of a nickel-titanium alloy. The Ti(Ni,Cu)2 precipitates are typically disk-shaped, with a thickness of 1-20 nm, preferably 1 nm, and a diameter of 10-500 nm.

[0047] The term "compressive stress" used herein refers to the compressive load applied to a sample divided by the initial cross-sectional area of ​​the sample, i.e., the absolute value of the process stress, and is expressed in megapascals (MPa).

[0048] As used herein, the term "phase change stress" includes the martensitic phase change onset stress, measured at the intersection of the linear extension of the initial elastic deformation section and the positive phase change section on the load-stress-strain curve, and is expressed in megapascals (MPa).

[0049] The term "hysteresis area" used in this paper refers to the area enclosed between the loading and unloading curves in a stress-strain curve, and is expressed in units of MPa or MJ / m. 3 is.

[0050] As used herein, the term "residual strain" refers to the unrecovered strain in a material after it has undergone cyclic deformation, i.e., the change in length of the sample divided by the original length of the sample.

[0051] The term "superelasticity" as used in this paper refers to the phenomenon in which nickel-titanium alloys undergo strains far exceeding the elastic limit of typical metallic structural materials under external force, and then automatically recover upon unloading. In other words, when an external stress is applied to the parent phase, a stress-induced martensitic phase transformation occurs, causing the alloy to exhibit mechanical behavior different from that of conventional materials, with an elastic limit far exceeding that of conventional materials and no longer obeying Hooke's law. Compared to shape memory properties, superelasticity is force-driven. In short, superelasticity can be divided into two types: linear and nonlinear. In the former, the stress and strain relationship is nearly linear. Nonlinear superelasticity refers to the occurrence of stress-induced martensitic and reverse martensitic phase transformations during loading and unloading within a certain temperature range above the austenite phase transformation finish temperature (Af).

[0052] In comparison with conventional nickel-titanium alloys, the alloys of the present invention exhibit superior superelastic deformation. The alloys of the present invention can also exhibit superior cyclic phase change stability and low phase change stress.

[0053] In one aspect, the present invention provides a nickel-titanium alloy comprising titanium, nickel, copper, and optionally cobalt, wherein the weight ratios of titanium, nickel, copper, and optionally cobalt to the total weight of the nickel-titanium alloy are: Titanium 38%~47% Nickel 35%~50%, Copper 3%~20%, Cobalt 0-5% A nickel-titanium based alloy is provided.

[0054] The nickel-titanium-based alloys can exhibit excellent cyclic phase change stability, meaning that they can undergo at least 10 million loading-unloading cyclic phase change cycles without experiencing structural fatigue and / or significant functional fatigue.

[0055] Preferably, the nickel-titanium based alloy of the present invention will not suffer from structural fatigue and / or significant functional fatigue after at least 10 million loading-unloading cyclic phase change cycles at a compressive stress of 350-700 MPa.

[0056] In one embodiment, the nickel-titanium alloy comprises, by weight: Titanium 38%~47% Nickel 30% to 50% Copper 4~20%, Contains 0.1-5% cobalt.

[0057] In the above nickel-titanium alloy, the sum of the weight percentages of the individual components is 100% of the total weight of the alloy.

[0058] The nickel-titanium alloy may further contain unavoidable impurities. In one embodiment, the impurity content of the nickel-titanium alloy is: carbon≦0.012 wt%, iron≦0.015 wt%, sulfur≦0.001 wt%, silicon≦0.01 wt%, manganese≦0.008 wt%, zinc≦0.005 wt%, lead+tin+magnesium+bismuth≦0.002 wt%, oxygen+nitrogen≦0.1 wt%, hydrogen≦0.001 wt%, and the total impurities content, including other small amounts of additive elements and unavoidable impurities, is ≦0.5 wt%.

[0059] Nickel and titanium are the basic constituents of nickel-titanium alloys. These two elements form a B2 crystal lattice-based phase-change shape memory alloy in approximately equal atomic ratios. If the content of either element is too high or too low, excessive precipitation phases without phase-change functionality, such as high-nickel (e.g., Ni3Ti) or high-titanium (e.g., Ti2Ni), will form, resulting in reduced phase-change distortion and cooling performance. The addition of copper can partially substitute for nickel, partially or completely converting the phase change from the original, incompatible B2-B19′ phase change to the more compatible B2-B19 phase change and forming the Ti(Ni,Cu)2 precipitate, thereby improving the cyclic phase-change stability of the material. If the copper content is too low, it cannot induce the B2-B19 phase change or the formation of the Ti(Ni,Cu)2 precipitate. If the copper content is too high, the material will have poor ductility and will be unsuitable for forging or other machining processes. The role of cobalt is to effectively lower the phase change temperature of the material, allowing it to exhibit superelasticity at room temperature and achieve room temperature cooling. Excessive cobalt (>5%) will excessively lower the phase change temperature of the material, causing it to lose its room temperature superelasticity and reducing the forgeability of the material.

[0060] Impurities affect the composition of the precipitate phases; for example, excess oxygen and carbon can result in nickel-titanium oxide or titanium-carbon-like precipitate phases, reducing the ductility and forgeability of the material and reducing the recoverable strain, adiabatic temperature drop, and fatigue resistance of the titanium-nickel-copper-cobalt material.

[0061] By improving the chemical composition and processing, the microstructure of the new titanium-nickel alloy developed by this invention contains a large amount of nano-sized Ti(Ni, Cu)2 precipitates. The thickness of the nano-sized Ti(Ni, Cu)2 precipitates is 1-20 nm, preferably 1 nm, and the diameter is 10-500 nm. Figure 3 shows a photograph of the microstructure of one example of the titanium-nickel alloy of this invention after melting, forging, and heat treatment.

[0062] As shown in FIG. 3, the titanium-nickel alloy includes a continuous phase (e.g., a TiNiCuCo substrate) 31 and a nano-sized Ti(Ni, Cu)2 precipitate phase 32 in the substrate.

[0063] This suppresses the generation of dislocations through the strengthening effect of the precipitate phase, and promotes martensitic phase change through the coherent strain and stress between the precipitate phase and the substrate, thereby improving the stability of the cyclic phase change and reducing the phase change stress.

[0064] Preferably, the microstructural structure of the titanium-nickel based alloy contains 5% to 60% by volume of the Ti(Ni, Cu)2 precipitate phase, relative to the total volume.

[0065] Preferably, the nickel-titanium based alloy of the present invention comprises: The raw materials containing titanium, nickel, copper and optional cobalt are melted and manufactured as an alloy. performing a plastic deformation treatment to apply a total strain of 1% to 60% to the alloy from one to three directions; The alloy is plastically deformed and then heat treated and quenched to obtain a nickel-titanium alloy.

[0066] In another aspect, the present invention provides a method for producing a pharmaceutical composition comprising: (i) melting and preparing an alloy sample from raw materials containing titanium, nickel, copper, and optionally cobalt; (ii) performing a plastic deformation treatment on the alloy sample from one to three directions to apply a total strain of 1% to 60%; (iii) heat treating and quenching the alloy sample after the plastic deformation treatment to obtain a nickel-titanium based alloy. A method for producing a nickel-titanium based alloy is provided.

[0067] Preferably, the method may further comprise the step of mixing raw materials of titanium, nickel, copper and cobalt before step (i).

[0068] Preferably, the method may further include a step of cutting the melt-fabricated alloy sample into a cube, a rectangle, or a cylinder before step (ii), and step (ii) includes a plastic deformation treatment that applies a total strain of 1% to 60% to the cube, rectangle, or cylinder from one to three directions.

[0069] Preferably, the cutting is at least one selected from wire cutting, diamond electric saw cutting, and laser cutting.

[0070] Preferably, in the method, step (iii) comprises carrying out heat treatment under conditions in which the temperature is set to 350 to 700°C, preferably 450 to 700°C, for a time period of 0.1 to 3 hours, and quenching by immersing in water immediately after the heat treatment.

[0071] Preferably, in the method, step (i) includes evacuating an arc melting furnace or an induction melting furnace, then passing high-purity argon gas having a purity of ≥ 99%, and then melting and fabricating raw materials containing titanium, nickel, copper, and optionally cobalt into an alloy.

[0072] Preferably, in the method, the arc melting current is 150 to 1000A.

[0073] Preferably, the arc-melted sample may be button-shaped, with a diameter of 5 to 100 mm and a thickness of 5 to 60 mm, or the arc-melted and suction-cast sample may be cylindrical rod-shaped, with a diameter of 5 to 20 mm and a height of 100 to 200 mm.

[0074] Also, preferably, in the above method, the current of the induction melting furnace is 200 to 300 A and the vibration frequency is 1 to 80 KHz.

[0075] Preferably, the induction melted sample is in the form of a cylindrical rod, with a diameter of 5 to 100 mm and a height of 50 to 400 mm.

[0076] FIG. 1 is a flowchart showing a part of the production of a titanium-nickel alloy by a three-axis forging process in a preferred embodiment of the present invention.

[0077] As shown in Figure 1a, before heat treatment, a plastic deformation process (i.e., forging process) is first performed on the rectangular sample 12 using an upper compressing member 11 and a lower compressing member 13, applying a 1% to 20% strain to the sample in a direction perpendicular to the C-plane of the sample. Next, as shown in Figure 1b, the sample is rotated around the y-axis so that the B-plane of the rectangular sample is perpendicular to the direction of stress application by the upper and lower compressing members. This results in a plastic deformation process in which a 0% to 20% strain is applied to the sample in a direction perpendicular to the B-plane of the rectangular sample. Finally, as shown in Figure 1c, the sample is again rotated around the x-axis so that the A-plane of the rectangular sample is perpendicular to the direction of stress application by the upper and lower compressing members. This results in a plastic deformation process in which a 0% to 20% strain is applied to the sample in a direction perpendicular to the A-plane of the rectangular sample.

[0078] Finally, the sample is subjected to a plastic deformation process (forging process) in which a total strain of 1% to 60% is applied to the sample, and the forged sample is sent to a heat treatment step.

[0079] FIG. 2 is a flow chart of a portion of another preferred embodiment of the present invention for producing a titanium-nickel alloy by a single-axis forging process.

[0080] 2, a plastic deformation process (i.e., forging process) is performed on a cylindrical sample 22 along its axial direction using an upper compressing member 21 and a lower compressing member 23, applying a total strain of 1% to 60% to the sample 22. In this embodiment, the sample is plastically deformed along only one direction, which differs from the above-described plastic deformation process, which is performed on the sample along three directions.

[0081] Without being bound by theory, it is generally believed that the above-mentioned plastic deformation process, which applies a total strain of 1% to 60% to the sample from one to three directions, is a key step in the formation of a large amount of nanosized Ti(Ni, Cu)2 precipitates in the microstructure of titanium-nickel alloys. During the plastic deformation process, a large amount of dislocations are generated within the grains, forming nanosized dislocation cell structures. During heat treatment, the dislocation defects promote the nucleation of the precipitates within the dislocation network, thereby forming densely packed nanosized precipitates and improving the phase change stability of the material.

[0082] In a third aspect, the present invention provides an article of manufacture comprising a nickel-titanium-based alloy, the nickel-titanium-based alloy being the nickel-titanium-based alloy described above.

[0083] Preferably, the article is at least one selected from a biomedical device, a solid state elastocaloric cooling member, a joint, a fastener, a damping energy dissipation device, an antenna, an electromechanical actuator member, and an automotive member.

[0084] Preferably, the solid state elastocaloric cooling member is capable of producing a temperature drop of at least 10° C. upon unloading at a compressive stress of 350 to 700 MPa.

[0085] In a fourth aspect, the present invention provides applications of the above nickel-titanium based alloys in biomedical materials, solid-state elastocaloric cooling components, aerospace components, mechanical engineering components, automotive components and / or architectural components.

[0086] According to the present invention, in cyclic stress-strain curve measurements, nickel-titanium alloys undergo at least 10 million cyclic phase change cycles at a compressive stress of 350-700 MPa without any significant change in the stress-strain curve, i.e., the residual strain measured at the 10 millionth cycle compared to the first cycle is no more than 1%, preferably no more than 0.2%, the change in phase change stress is no more than 25%, preferably no more than 3%, and the change in hysteresis area is no more than 30%, preferably no more than 10%.

[0087] The following examples are provided to illustrate the alloys, products, and methods of the present invention. These examples are for illustrative purposes only and are not intended to limit the disclosure to the materials, conditions, or process parameters described therein.

[0088] Example 1 Titanium, nickel, copper, and cobalt, all with a purity of 99.995 atomic %, were mixed in a weight ratio of 43% titanium, 47% nickel, 8.5% copper, and 1.5% cobalt, and placed in an arc melting furnace (Shenyang Kegyi DHL400) to melt 2 × 10 -4 The furnace was evacuated to 100 Pa, and then high-purity argon gas (purity ≥ 99%) was introduced. The current of the melting furnace was adjusted to 150-700 A. The raw materials were melted as an alloy, and the sample was inverted and remelted a total of five times, each time for 1-4 minutes, to obtain an alloy sample. The alloy sample was cut into a rectangular shape using a wire cutter (Mitsubishi Electric Corporation DWC90G). As shown in Figure 1, a homemade ceramic upper pressure member was used to apply a total strain of 60% to the rectangular shape in three directions (forging). The forged alloy material was heat-treated at 500°C for 40 minutes. After heat treatment, it was quickly immersed in water and quenched for 1 minute. This yielded the titanium-nickel-copper-cobalt alloy of Example 1.

[0089] Example 2 The titanium-nickel-copper-cobalt alloy of Example 2 was prepared in essentially the same manner as in Example 1, except that the heat treatment temperature was 520°C.

[0090] Example 3 Titanium, nickel, copper, and cobalt, all of which have a purity of 99.995 atomic %, are mixed in a weight ratio of 42% titanium, 45% nickel, 11.5% copper, and 1.5% cobalt, and the mixture is added to an arc melting furnace as a raw material. The alloy of Example 3 is produced in essentially the same manner as Example 1, except that a plastic deformation process (forging process) is performed to apply a total strain of 6% to a rectangular prism in one direction.

[0091] Example 4 The alloy of Example 4 is produced in essentially the same manner as Example 3, except that a plastic deformation process (forging process) is performed to apply a total strain of 9% to a rectangular parallelepiped in one direction.

[0092] Example 5 The alloy of Example 5 is produced in essentially the same manner as Example 3, except that a plastic deformation process (forging process) is performed on the rectangular parallelepiped to impart a total strain of 20% in one direction.

[0093] Example 6 The alloy of Example 6 was prepared in essentially the same manner as in Example 5, except that the heat treatment temperature was 600° C. and the heat treatment time was 2 hours.

[0094] Example 7 The alloy of Example 7 is produced in essentially the same manner as Example 1, except that a plastic deformation process (forging process) is performed to apply a total strain of 6% to a rectangular parallelepiped in one direction.

[0095] Example 8 The titanium-nickel-copper-cobalt alloy of Example 8 was produced in essentially the same manner as Example 1, except that a plastic deformation treatment was performed to apply a total strain of 50% to the rectangular prism in three directions and the heat treatment temperature was 400°C.

[0096] Example 9 The titanium-nickel-copper-cobalt alloy of Example 9 was prepared in essentially the same manner as Example 1, except that no cobalt was added, the weight ratios were titanium 43.7%, nickel 44.5%, and copper 12%, the heat treatment temperature was 400°C, and the time was 10 minutes.

[0097] Comparative Example 1 The alloy was prepared in essentially the same manner as in Example 1, except that copper and cobalt were not added and the weight ratio of the raw materials was 44% titanium and 56% nickel.

[0098] Comparative Example 2 The alloy is produced in essentially the same manner as in Example 1, except that no forging process is performed.

[0099] Comparative Example 3 The alloy was produced in essentially the same manner as in Example 3, except that no forging process was performed.

[0100] Comparative Example 4 The alloy was produced in essentially the same manner as in Comparative Example 1, except that a plastic deformation process (forging process) was performed on the rectangular parallelepiped to apply a total strain of 50% in one direction.

[0101] measurement -Mechanical and thermal properties of alloys Using a universal testing machine (MTS 858) equipped with a displacement meter (COD 632.02F-20), isothermal loading and unloading mechanical tests (strain rate 4 × 10 -4 s -1 The specimen is loaded to 550 MPa at a strain rate of 100 sq. m and then unloaded to 50 MPa at the same strain rate. The force-displacement data is recorded and further converted into a stress-strain curve. The phase change stress is measured at the linear extension intersection of the initial elastic deformation section and the positive phase change section in the loading stress-strain curve. The loading curve and the unloading curve are integrated to determine the hysteresis area, which is the area enclosed by both curves. The height of the sample before and after cyclic loading is measured with a micrometer screw, and the residual strain after loading is calculated. The adiabatic temperature drop at 550 MPa is measured using the following method: a strain rate of 4 x 10 -4 s -1 The load was slowly increased to 550 MPa at a strain rate of 2 s. -1 The sample is rapidly unloaded to 0 MPa at 1000 kJ / s. At the same time, an infrared camera (FLIR SC7700M) is used to capture the temperature change on the sample surface during rapid unloading, and the adiabatic temperature drop is calculated.

[0102] The results are shown in Table 1. [Table 1]

[0103] As can be seen, compared to Comparative Examples 1 to 4, Examples 1 to 9 have a large adiabatic temperature drop (greater than 15°C), a low phase change stress, a small hysteresis area (representing low energy consumption), and a small residual strain (representing good performance retention during cyclic deformation, i.e., high cyclic stability).

[0104] - Microstructure of alloy The microstructures of each example and comparative example were observed using a transmission electron microscope (JEOL, JEM-ARM200F) at a voltage of 200 kV. Figure 3 is a photograph of the microstructure of the titanium-nickel alloy of Example 1 after melting, forging, and heat treatment. The photograph shows that the alloy contains a TiNiCuCo substrate and a large amount of nano-sized Ti(Ni,Cu)2 precipitates in the substrate. The Ti(Ni,Cu)2 precipitates have a thickness of 1 nm and a diameter of 10-100 nm.

[0105] Table 2 shows the state of the Ti(Ni, Cu)2 precipitate phase in the microstructural structure of the alloys of each example and comparative example. [Table 2]

[0106] In comparison with Comparative Examples 1 to 4, the microstructures of Examples 1 to 9 all contain Ti(Ni, Cu)2 precipitates, or the diameter and thickness of the Ti(Ni, Cu)2 precipitates are small and the proportion is appropriate (greater than 5% and less than 50%). In the Comparative Examples, there are no Ti(Ni, Cu)2 precipitates, or the proportion of the precipitates is too small and the size is too large. Precipitates with appropriate proportions and sizes are advantageous for the material's performance, including adiabatic temperature drop, cyclic stability, phase change stress, energy consumption ratio, and fatigue.

[0107] - Loading-unloading cycling phase change characteristics of alloys The loading-unloading cyclic curve was measured using an MTS Landmark 370.10 universal testing machine, with the fatigue test frequency set to 20 Hz, and the load magnitude was calculated by multiplying the cross-sectional area of ​​the sample by the required stress (e.g., 550 MPa). Figure 4 shows the stress-strain curve under cyclic deformation of the titanium-nickel alloy of Example 1 after melting, forging, and heat treatment. As can be seen, the alloy did not undergo any significant change in the stress-strain curve even after undergoing at least 10 million cyclic phase change cycles under a cyclic compressive stress of 550 MPa.

[0108] Table 3 shows the changes in phase change stress, residual strain, hysteresis area, and temperature drop for each example and comparative example after undergoing cyclic deformation at 550 MPa, with Example 1 undergoing 10 million cycles of cyclic phase change and the other examples undergoing 10,000 cycles of cyclic phase change. [Table 3]

[0109] Table 3 shows that the Examples have superior cyclic stability compared to the Comparative Examples. This means that the alloy materials can maintain excellent performance during cyclic loading. The smaller the residual strain, the smaller the phase change stress, hysteresis area, and temperature drop, resulting in higher cyclic stability. The values ​​for these four indicators for Examples 1 to 9 are all significantly smaller than those for the Comparative Examples, demonstrating that the alloy materials of Examples 1 to 9 have superior cyclic stability. The above test results indicate that controlling the chemical composition and processing process can induce a large amount of nano-sized Ti(Ni,Cu)2 precipitates in the alloy microstructure. This strengthens the precipitation phase, suppressing dislocation generation and promoting the martensitic phase transformation through the coherent strain and stress between the precipitation phase and the substrate, thereby improving cyclic phase change stability and reducing phase change stress.

[0110] It will be appreciated that the above-disclosed variations and other features, functions, or alternatives thereof, may be combined into many other different systems or applications. Those skilled in the art will be able to subsequently make various alternatives, modifications, variations, or improvements not presently foreseen or anticipated, which are also intended to be within the scope of the appended claims.

[0111] (Addendum) (Appendix 1) A nickel-titanium alloy containing titanium, nickel, copper, and optionally cobalt, The weight ratios of titanium, nickel, copper, and optional cobalt to the total weight of the nickel-titanium alloy are: Titanium 38%~47% Nickel 35%~50%, Copper 3%~20%, Cobalt 0-5% The nickel-titanium alloy undergoes at least 10 million loading-unloading cyclic phase change cycles without experiencing structural fatigue and / or significant functional fatigue. Nickel-titanium alloy.

[0112] (Appendix 2) The nickel-titanium alloy undergoes at least 10 million loading-unloading phase change cycles under a compressive stress of 350 to 700 MPa without experiencing structural fatigue and / or significant functional fatigue; 1. A nickel-titanium-based alloy as defined in Appendix 1.

[0113] (Appendix 3) The microstructure of the nickel-titanium alloy contains a Ti(Ni, Cu)2 precipitate phase. 3. A nickel-titanium-based alloy according to claim 1 or 2.

[0114] (Appendix 4) The microstructure contains 5% to 60% by volume of Ti(Ni, Cu) precipitate phase, based on the total volume. 3. A nickel-titanium-based alloy as defined in Appendix 3.

[0115] (Appendix 5) The thickness of the Ti(Ni, Cu)2 precipitate phase is 1 to 20 nm, preferably 1 nm, and the diameter is 10 to 500 nm. 5. A nickel-titanium-based alloy according to claim 3 or 4.

[0116] (Appendix 6) The nickel-titanium alloy has a weight ratio of: Titanium 38%~47% Nickel 30% to 50% Copper 4~20%, Contains 0.1-5% cobalt, 6. A nickel-titanium alloy according to any one of appendices 1 to 5.

[0117] (Appendix 7) Further containing unavoidable impurities, including carbon≦0.012 wt%, iron≦0.015 wt%, sulfur≦0.001 wt%, silicon≦0.01 wt%, manganese≦0.008 wt%, zinc≦0.005 wt%, lead + tin + magnesium + bismuth≦0.002 wt%, oxygen + nitrogen≦0.1 wt%, hydrogen≦0.001 wt%, plus other small amounts of added elements and unavoidable impurities, the total amount of impurities is≦0.5 wt%; 7. A nickel-titanium alloy according to any one of appendices 1 to 6.

[0118] (Appendix 8) Nickel-titanium alloys are The raw materials containing titanium, nickel, copper and optional cobalt are melted and manufactured as an alloy. performing a plastic deformation treatment to apply a total strain of 1% to 60% to the alloy from one to three directions; The alloy is subjected to a plastic deformation treatment and then heat-treated and quenched to obtain a nickel-titanium alloy. 8. A nickel-titanium alloy according to any one of appendices 1 to 7.

[0119] (Appendix 9) (i) melting and preparing an alloy sample from raw materials containing titanium, nickel, copper, and optionally cobalt; (ii) performing a plastic deformation treatment on the alloy sample from one to three directions to apply a total strain of 1% to 60%; (iii) heat treating and quenching the alloy sample after the plastic deformation treatment to obtain a nickel-titanium based alloy; A method for producing nickel-titanium alloys.

[0120] (Appendix 10) further comprising, prior to step (i), mixing sources of titanium, nickel, copper and optional cobalt; The method described in Appendix 9.

[0121] (Appendix 11) The method further includes, before step (ii), a step of cutting the melt-fabricated alloy sample into a cube, a rectangle, or a cylinder, and step (ii) includes a plastic deformation treatment of applying a total strain of 1% to 60% to the cube, rectangle, or cylinder from one to three directions; Optionally, the cutting is at least one selected from wire cutting, diamond electric saw cutting, and laser cutting. 11. The method of claim 9 or 10.

[0122] (Appendix 12) Step (iii) includes heat treating the material at a temperature of 350 to 700°C for 0.1 to 3 hours, and quenching the material in water immediately after the heat treatment. 12. The method according to any one of Appendices 9 to 11.

[0123] (Appendix 13) Step (i) includes evacuating an arc melting furnace or an induction melting furnace, then passing high-purity argon gas having a purity of ≥ 99%, and then melting raw materials containing titanium, nickel, copper, and optionally cobalt to form an alloy; 13. The method according to any one of Appendices 9 to 12.

[0124] (Appendix 14) The arc melting current is 150-1000A. Optionally, the arc-melted sample may be button-shaped, with a diameter of 5-100 mm and a thickness of 5-60 mm, or the arc-melted and suction-cast sample may be cylindrical rod-shaped, with a diameter of 5-20 mm and a height of 100-200 mm. The method described in Appendix 13.

[0125] (Appendix 15) The induction melting furnace has a current of 200-300A and a vibration frequency of 1-80KHz. Optionally, the induction melt fabricated sample is a cylindrical rod with a diameter of 5-100 mm and a height of 50-400 mm. The method described in Appendix 13.

[0126] (Appendix 16) A product comprising a nickel-titanium alloy, The nickel-titanium alloy is a nickel-titanium alloy according to any one of appendices 1 to 8, or a nickel-titanium alloy produced by a method according to any one of appendices 9 to 15. Products containing nickel-titanium alloys.

[0127] (Appendix 17) The article is at least one selected from a biomedical device, a solid-state elastocaloric cooling member, a joint, a fastener, a damping energy dissipation device, an antenna, an electromechanical actuator member, and an automotive member. The product described in Appendix 16.

[0128] (Appendix 18) The solid-state elastocaloric cooling member undergoes a temperature drop of at least 10°C when subjected to a compressive stress of 350 to 700 MPa and released. The product described in Appendix 17.

[0129] (Appendix 19) 16. The application of the nickel-titanium based alloy according to any one of appendices 1 to 8 or produced by the method according to any one of appendices 9 to 15 in biomedical materials, solid-state elastocaloric cooling components, aerospace components, mechanical engineering components, automotive components and / or building components.

[0130] (Appendix 20) In a cyclic stress-strain curve test, the nickel-titanium alloy undergoes at least 10 million cyclic phase change cycles under a compressive stress of 350-700 MPa without any significant change in the stress-strain curve, i.e., compared to the first cycle, the residual strain after the 10 millionth cycle compressive deformation does not exceed 1%, preferably does not exceed 0.2%, the change in phase change stress does not exceed 25%, preferably does not exceed 3%, and the change in hysteresis area does not exceed 30%, preferably does not exceed 10%. A nickel-titanium based alloy according to any one of appendices 1 to 8, a method according to any one of appendices 9 to 15, a product according to any one of appendices 16 to 18, or an application according to appendix 19.

Claims

1. A nickel-titanium alloy containing titanium, nickel, copper, and optionally cobalt, The weight ratios of titanium, nickel, copper, and optional cobalt to the total weight of the nickel-titanium alloy are: Titanium 38% to 47% Nickel 35% to 50%, Copper 3% to 20%, Cobalt 0-5% The nickel-titanium alloy undergoes at least 10 million loading-unloading cyclic phase change cycles without experiencing structural fatigue and / or significant functional fatigue. Nickel-titanium alloy.

2. The nickel-titanium alloy undergoes at least 10 million loading-unloading phase change cycles at a compressive stress of 350-700 MPa without experiencing structural fatigue and / or significant functional fatigue; The nickel-titanium alloy of claim 1.

3. The microstructure of the nickel-titanium alloy contains Ti (Ni, Cu) 2 Contains precipitated phases, The nickel-titanium alloy according to claim 1 or 2.

4. Based on the total volume, the microstructure contains 5% to 60% by volume of Ti (Ni, Cu) 2 Contains precipitated phases, The nickel-titanium alloy according to claim 3.

5. Ti (Ni, Cu) 2 The thickness of the precipitated phase is 1 to 20 nm, preferably 1 nm, and the diameter is 10 to 500 nm. The nickel-titanium alloy according to claim 3 or 4.

6. The nickel-titanium alloy has a weight ratio of: Titanium 38% to 47% Nickel 30% to 50% Copper 4-20%, Contains 0.1-5% cobalt, The nickel-titanium alloy according to any one of claims 1 to 5.

7. Further containing unavoidable impurities, including carbon≦0.012 wt%, iron≦0.015 wt%, sulfur≦0.001 wt%, silicon≦0.01 wt%, manganese≦0.008 wt%, zinc≦0.005 wt%, lead + tin + magnesium + bismuth≦0.002 wt%, oxygen + nitrogen≦0.1 wt%, hydrogen≦0.001 wt%, plus other small amounts of added elements and unavoidable impurities, the total impurity amount is≦0.5 wt%. The nickel-titanium alloy according to any one of claims 1 to 6.

8. Nickel-titanium alloys are The raw materials containing titanium, nickel, copper and optional cobalt are melted and manufactured as an alloy. A plastic deformation treatment is performed to apply a total strain of 1% to 60% to the alloy from one to three directions, The alloy is subjected to a plastic deformation treatment and then heat-treated and quenched to obtain a nickel-titanium alloy. The nickel-titanium alloy according to any one of claims 1 to 7.

9. (i) melting and preparing an alloy sample from raw materials containing titanium, nickel, copper, and optionally cobalt; (ii) subjecting the alloy sample to a plastic deformation treatment in one to three directions to a total strain of 1% to 60%; (iii) heat treating and quenching the alloy sample after the plastic deformation treatment to obtain a nickel-titanium based alloy; A method for producing nickel-titanium alloys.

10. further comprising, prior to step (i), mixing sources of titanium, nickel, copper and optional cobalt; 10. The method of claim 9.

11. The method further comprises, before step (ii), cutting the melt-fabricated alloy sample into a cube, a rectangle, or a cylinder, and step (ii) comprises a plastic deformation treatment that applies a total strain of 1% to 60% to the cube, rectangle, or cylinder from one to three directions; Optionally, the cutting is at least one selected from wire cutting, diamond electric saw cutting, and laser cutting.

11. The method according to claim 9 or 10.

12. Step (iii) includes heat treating the material at a temperature of 350-700°C for 0.1-3 hours, and quenching the material in water immediately after the heat treatment; The method according to any one of claims 9 to 11.

13. Step (i) comprises evacuating an arc melting furnace or an induction melting furnace, then passing high-purity argon gas having a purity of ≥ 99%, and then melting raw materials containing titanium, nickel, copper, and optionally cobalt to form an alloy; The method according to any one of claims 9 to 12.

14. The arc melting current is 150 to 1000A. Optionally, the arc-melted sample may be button-shaped, with a diameter of 5-100 mm and a thickness of 5-60 mm, or the arc-melted and suction-cast sample may be cylindrical rod-shaped, with a diameter of 5-20 mm and a height of 100-200 mm. The method of claim 13.

15. The induction melting furnace has a current of 200-300A and a vibration frequency of 1-80KHz. Optionally, the induction melt fabricated sample is a cylindrical rod having a diameter of 5-100 mm and a height of 50-400 mm. The method of claim 13.

16. A product comprising a nickel-titanium alloy, The nickel-titanium alloy is a nickel-titanium alloy according to any one of claims 1 to 8, or a nickel-titanium alloy produced by a method according to any one of claims 9 to 15. Products containing nickel-titanium alloys.

17. The article is at least one selected from a biomedical device, a solid-state elastocaloric cooling member, a joint, a fastener, a damping energy dissipation device, an antenna, an electromechanical actuator member, and an automotive member.

17. The article of manufacture of claim 16.

18. The solid-state elastocaloric cooling element experiences a temperature drop of at least 10°C when unloaded under a compressive stress of 350 to 700 MPa.

18. The article of manufacture of claim 17.

19. 16. The application of the nickel-titanium based alloy according to any one of claims 1 to 8 or produced by the method according to any one of claims 9 to 15 in biomedical materials, solid-state elastocaloric cooling components, aerospace components, mechanical engineering components, automotive components and / or building components.

20. In a cyclic stress-strain curve test, the nickel-titanium alloy undergoes at least 10 million cyclic phase change cycles under a compressive stress of 350-700 MPa without any significant change in the stress-strain curve, i.e., the residual strain after the 10 millionth cycle of compressive deformation does not exceed 1%, preferably does not exceed 0.2%, the change in phase change stress does not exceed 25%, preferably does not exceed 3%, and the change in hysteresis area does not exceed 30%, preferably does not exceed 10%, compared to the first cycle. A nickel-titanium based alloy according to any one of claims 1 to 8, a method according to any one of claims 9 to 15, a product according to any one of claims 16 to 18, or an application according to claim 19.

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