High-temperature shape memory alloy, preparation method and driver
By adding crickets in high temperature -shaped memory alloys to form a spherical or rigid NB phase, it solves the problem of lack of performance of traditional shape memory alloys at high temperature, and achieves the effect of high extension rate, larger driving amplitude and long fatigue life.
Patent Information
- Application Number
- CN202310927874.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-07-26
- Publication Date
- 2025-01-28
AI Technical Summary
Traditional shape memory alloys operate at ambient temperature below 100℃, with an elongation rate of less than 10%, with a low driving amplitude and fatigue life, making it difficult to meet the needs of high-temperature application scenarios.
Through the increase in titanium and nickel composition, a spherical or rod -shaped NB phase is formed, and the stress concentration of the crystal and the phase boundary is transferred to achieve the distribution of stress and strain, thereby increasing the extension and fatigue life of high temperature -shaped memory alloys.
The extension of high temperature -shaped memory alloys reached more than 40 %, the maximum driving range exceeded 4.5 %, and the fatigue life exceeded 20,000, which significantly improved the performance of the material.
Smart Images
Figure CN119372524A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of alloy materials, and in particular to a high-temperature shape memory alloy, a preparation method and a driver. Background Art
[0002] Metallic intelligent drive devices made of shape memory alloys can replace traditional mechanical devices with complex structures. This shape memory alloy can be nickel-titanium shape memory alloy or other shape memory alloys. However, traditional shape memory alloys can only work at ambient temperatures below 100°C, and the tensile elongation is usually less than 10%, and the drive amplitude and fatigue life are low. Summary of the invention
[0003] The purpose of the present application is to provide a high temperature shape memory alloy, a preparation method and a driver, so as to achieve that the high temperature shape memory alloy has a higher elongation and fatigue life and can work normally at an ambient temperature greater than 100°C.
[0004] A first aspect of the present application provides a high temperature shape memory alloy, wherein the chemical composition, by mass percentage, is: 25-35% titanium, 45-55% nickel, 12-18% hafnium, and 6-10% niobium.
[0005] In the present application, by adding niobium to the titanium and nickel components and forming the Nb phase into a spherical or rod-shaped shape, the stress concentration at the grain boundaries and phase boundaries can be transferred to the Nb phase. The stress and strain distribution can be achieved through the Nb phase, thereby improving the elongation and fatigue life of the high-temperature shape memory alloy material.
[0006] The second aspect of the present application provides a method for preparing a high temperature shape memory alloy, which comprises the following steps:
[0007] Vacuum melting of titanium, nickel, hafnium and niobium to obtain pure ingots;
[0008] Performing hot drawing on the pure ingot to obtain a memory alloy coarse wire;
[0009] The memory alloy thick wire is subjected to continuous cold drawing treatment, and then subjected to a first step of annealing treatment to obtain a memory alloy thin wire;
[0010] The memory alloy filaments are subjected to a second annealing treatment to adjust the shape of the niobium phase into a spherical shape and / or a rod shape.
[0011] In the present application, by subjecting the material to a second step annealing treatment, the Nb phase can be regulated into a spherical or rod-shaped shape, so that the elongation of the high-temperature shape memory alloy can reach more than 40%. In addition, the high-temperature shape memory alloy having the above-mentioned Nb phase shape, after being used to manufacture an actuator, the maximum driving amplitude of the material can exceed 4.5%, while the maximum driving amplitude of the TiNiHf shape memory alloy formed without adding Nb is less than 3.5%, thus, the maximum driving amplitude of the TiNiHfNb high-temperature shape memory alloy has a higher upper limit. In addition, the fatigue life of the high-temperature shape memory alloy having the above-mentioned Nb phase shape exceeds 20,000 times when the driving amplitude is 2.8%, while the fatigue life of the TiNiHf shape memory alloy formed without adding Nb under the same conditions is about 5,000 times, thus, the high-temperature shape memory alloy having the above-mentioned Nb phase shape has a longer fatigue life.
[0012] In a possible implementation, the temperature of the first annealing treatment is between 650° C. and 800° C., so as to ensure that the thick wire is cold drawn into a thin wire with a desired diameter, while ensuring the hardness and strength of the material and the uniformity of the material structure.
[0013] In a possible implementation, the temperature of the second annealing treatment is between 750° C. and 850° C., so that the Nb phase in the material can be regulated into a spherical or rod-shaped shape to improve the elongation of the high-temperature shape memory alloy.
[0014] In a possible implementation, the ratio of the maximum length dimension of the niobium phase to the diameter of the niobium phase is between 1 and 50. By making the ratio of the maximum length dimension of the Nb phase to the diameter of the Nb phase between 1 and 50, the elongation of the high temperature shape memory alloy can be improved, and the fatigue life can be improved.
[0015] In a possible implementation, the maximum length of the niobium phase is between 15 nm and 200 nm. By adjusting the maximum length of the Nb phase to between 15 nm and 200 nm, the high temperature shape memory alloy in this embodiment can be guaranteed to have a larger elongation and fatigue life.
[0016] In a possible implementation manner, the spherical cross-section is circular or elliptical.
[0017] In a possible implementation, before hot drawing the clean ingot, the method further includes:
[0018] The clean ingot is subjected to forging, hot rolling and coiling treatment in sequence, thereby facilitating obtaining an ingot with a uniform material structure.
[0019] In a possible implementation, the vacuum melting of titanium, nickel, hafnium and niobium specifically includes:
[0020] Titanium, nickel, hafnium and niobium are subjected to vacuum suspension melting or vacuum consumable melting. This makes it possible to obtain pure ingots in a more flexible way and to process and manufacture in different scenarios and under different processing environments.
[0021] A third aspect of the present application provides a driver, wherein the driver is made of the high-temperature shape memory alloy provided in the first aspect of the present application.
[0022] It should be understood that the foregoing general description and the following detailed description are exemplary only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 A flow chart of a method for preparing a high temperature shape memory alloy provided in an embodiment of the present application;
[0024] Figure 2 An electron microscope photograph of an ingot of a high temperature shape memory alloy provided in an embodiment of the present application formed in step S1;
[0025] Figure 3 An electron microscope photograph of the shape memory alloy filament formed in step S3 of the high temperature shape memory alloy provided in the embodiment of the present application;
[0026] Figure 4 An electron microscope photograph of the Nb phase in the high temperature shape memory alloy provided in the embodiment of the present application after being adjusted into a spherical or rod-shaped shape;
[0027] Figure 5 This is an enlarged electron microscope photo of the Nb phase in the high temperature shape memory alloy provided in the embodiment of the present application after being adjusted into a spherical or rod-shaped shape;
[0028] Figure 6 This is an enlarged electron microscope photo of the spherical Nb phase;
[0029] Figure 7 This is the stress-strain curve of the high-temperature shape memory alloy provided in the embodiment of the present application.
[0030] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application. DETAILED DESCRIPTION
[0031] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.
[0032] In the description of this application, unless otherwise clearly specified and limited, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance; unless otherwise specified or explained, the term "plurality" refers to two or more; the terms "connected" and "fixed" should be understood in a broad sense, for example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0033] Metal intelligent drive devices made of shape memory alloys can replace traditional mechanical devices with complex structures, achieve lightweight and compactness, improve system reliability, and even realize functions that are difficult for mechanical devices to complete. Traditional shape memory alloys can only work at ambient temperatures below 100°C. In application scenarios such as aircraft engines, nuclear power, oil and gas, and communication equipment, the internal operating temperature is usually higher than 100°C, so the required drive devices need to work in a relatively higher temperature environment, which puts higher requirements on the design and development of shape memory alloy materials used in drive devices.
[0034] At present, the nickel-titanium memory alloy that can be used in practical applications is limited by the phase transition temperature, and its operating temperature is difficult to exceed 100°C. Most other system shape memory alloys are difficult to put into use due to their poor shape memory effect or uncontrollable attenuation behavior. In addition, after being processed into actuating wires, the current shape memory alloys have a low tensile elongation, usually below 10%, and the comprehensive performance parameters such as actuating amplitude and fatigue life are low.
[0035] To this end, the embodiment of the present application provides a high-temperature shape memory alloy, which can be used to prepare a driver, wherein the chemical composition of the high-temperature shape memory alloy is as follows: 25-35% titanium (Ti), 45-55% nickel (Ni), 12-18% hafnium (Hf), and 6-10% niobium (Nb) by mass percentage. By adding hafnium to the titanium and nickel components, the phase transition temperature of the material can be increased to above 100°C, so that the material phase transition temperature of the high-temperature shape memory alloy can be increased to above 100°C, so that it can work in an ambient temperature greater than 100°C, which can broaden the application scenarios.
[0036] Among them, for the TiNiHf shape memory alloy formed without adding Nb, although the phase transition temperature of the material can be increased, it shows obvious brittleness and the tensile elongation of the material is low. The brittleness of the TiNiHf shape memory alloy comes from the stress concentration at the grain boundary and phase boundary caused by the anisotropy of the variants during the grain and martensitic phase transformation, which leads to the initiation and expansion of material cracks and manifests itself as the brittleness of the material on a macro scale.
[0037] In this embodiment, by adding niobium to the titanium and nickel components and forming the Nb phase into a spherical or rod-shaped shape, the stress concentration at the grain boundaries and phase boundaries can be transferred to the Nb phase. The stress and strain distribution can be achieved through the Nb phase, thereby improving the elongation and fatigue life of the high-temperature shape memory alloy material.
[0038] Among them, this embodiment can achieve an elongation of more than 40% for the TiNiHfNb high temperature shape memory alloy through the composition ratio between the above-mentioned Ti, Ni, Hf and Nb, which is far more than the elongation of less than 10% of the conventional nickel-titanium shape memory alloy. In addition, the maximum driving amplitude of the TiNiHfNb high temperature shape memory alloy exceeds 4.5%, while the maximum driving amplitude of the TiNiHf shape memory alloy formed without adding Nb is less than 3.5%, thus, the maximum driving amplitude of the TiNiHfNb high temperature shape memory alloy has a higher upper limit value. In addition, the fatigue life of the TiNiHfNb high temperature shape memory alloy when the driving amplitude is 2.8% exceeds 20,000 times, while the fatigue life of the TiNiHf shape memory alloy formed without adding Nb under the same conditions is about 5,000 times, thus, the TiNiHfNb high temperature shape memory alloy has a longer fatigue life.
[0039] In one embodiment, the chemical composition of the high-temperature shape memory alloy is as follows: Ti31.95%, Ni44.55%, Hf 13.5%, Nb 10% by mass percentage, the heat treatment temperature is 750°C, the heat treatment time is 48h, the elongation of the wire can reach 38%, and the breaking strength is 1350MPa.
[0040] In one embodiment, the chemical composition of the high-temperature shape memory alloy is as follows: Ti29.9%, Ni45.54%, Hf16.56%, Nb8% by mass percentage, the heat treatment temperature is 800°C, the heat treatment time is 4h, the elongation of the wire can reach 28%, and the breaking strength is 1400MPa.
[0041] Among them, the above-mentioned heat treatment process can make the Nb phase form a spherical or rod-shaped, so that the stress concentration at the grain boundary and phase boundary can be transferred to the Nb phase. The spherical or rod-shaped Nb phase can achieve stress and strain distribution, thereby improving the elongation and fatigue life of the high-temperature shape memory alloy material.
[0042] Of course, in some other embodiments, the components in the high temperature shape memory alloy may also have other proportions and different heat treatment conditions, which can also achieve the above-mentioned effects, and will not be elaborated here.
[0043] Figure 1 Flow chart of the method for preparing high temperature shape memory alloy provided in the embodiment of the present application, refer to Figure 1 The present application also provides a method for preparing the high temperature shape memory alloy, the method comprising the following steps:
[0044] Step S1, vacuum melting titanium, nickel, hafnium and niobium to obtain a pure ingot, Figure 2 This is an electron microscope photograph of the ingot of the high-temperature shape memory alloy provided in an embodiment of the present application formed in step S1.
[0045] Among them, vacuum suspension melting can be used, that is, under vacuum conditions, the above materials are suspended in a vacuum furnace, such as by generating high-frequency eddy currents in the vacuum furnace to suspend the materials and then melt them. In addition, vacuum consumable melting can also be used, that is, the above materials are melted by high temperature of an arc and dripped into a crucible, gradually melted, and gradually condensed into an ingot.
[0046] Step S2: hot drawing the clean ingot to obtain a memory alloy coarse wire.
[0047] Step S3: continuously cold-draw the thick memory alloy wire and perform the first step of annealing to obtain the memory alloy thin wire. Figure 3 This is an electron microscope photograph of the shape memory alloy filament formed in step S3 of the high temperature shape memory alloy provided in the embodiment of the present application.
[0048] Among them, after the continuous cold drawing treatment, the yield strength of the memory alloy thick wire can be increased by 20% to 30%, and the diameter is much smaller than the memory alloy thick wire. At the same time, through the first step of annealing, the hardness of the thick wire can be reduced to facilitate drawing. Among them, the continuous cold drawing treatment and the first step of annealing can be carried out in multiple times. For example, a cold drawing treatment can be carried out first, and then an annealing treatment can be carried out, and then a cold drawing treatment can be carried out again, and then an annealing treatment can be carried out again, and this cycle can be repeated many times until the diameter of the memory alloy thin wire reaches the expected value range. In this step, refer to Figure 2 , memory alloy filaments can form a strong texture, the material <111> The directional texture strength value reaches above 15.
[0049] Step S4, performing a second annealing treatment on the memory alloy filaments to adjust the shape of the niobium phase into a spherical and / or rod-like shape. The spherical shape may be a regular sphere, or an ellipsoid, or a shape that is approximately spherical or ellipsoidal. The rod-like shape may be a cylinder with a certain length or a shape that is approximately cylindrical.
[0050] in, Figure 4 This is an electron microscope photo of the Nb phase in the high temperature shape memory alloy provided in the embodiment of the present application after being adjusted to a spherical or rod-shaped shape. Figure 5 This is an enlarged electron microscope photo of the Nb phase in the high temperature shape memory alloy provided in the embodiment of the present application being adjusted to a spherical or rod-shaped shape. Figure 6 This is an enlarged electron microscope photo of the spherical Nb phase, refer to Figures 4 to 6 After drawing to form a thin wire, it can be further annealed. The annealing treatment in this step can regulate the Nb phase structure so that the material has a strong crystal orientation and can form a spherical or rod-like shape, or a spherical and rod-like shape at the same time.
[0051] Figure 7 The stress-strain curve of the high temperature shape memory alloy provided in the embodiment of the present application, the horizontal axis is the strain, that is, the elongation, the unit is percentage %, the vertical axis is the tensile force, the unit is MPa, refer to Figure 7 , Figure 7 The stress-strain relationship of the high temperature shape memory alloy under the condition of an ambient temperature of 750°C is shown by way of example. Curve a represents the mechanical properties when the Nb phase presents a nanofiber structure. Curve a is the curve when the Nb phase is not subjected to the second step annealing treatment in step S4, which shows that the corresponding elongation in the tensile force range of 0 to 1500 MPa is only 7%. Curves b, c, d, e, f, and g are the curves when the Nb phase is subjected to the second step annealing treatment in step S4. After the second step annealing treatment, the Nb phase is regulated into a spherical or rod-shaped shape, so that the elongation of the high temperature shape memory alloy can reach more than 40%.
[0052] In addition, the high-temperature shape memory alloy having the above-mentioned Nb phase shape, after being used to manufacture the actuator, the maximum driving amplitude of the material can exceed 4.5%, while the maximum driving amplitude of the TiNiHf shape memory alloy formed without adding Nb is less than 3.5%, thus, the maximum driving amplitude of the TiNiHfNb high-temperature shape memory alloy has a higher upper limit. In addition, the fatigue life of the high-temperature shape memory alloy having the above-mentioned Nb phase shape exceeds 20,000 times when the driving amplitude is 2.8%, while the fatigue life of the TiNiHf shape memory alloy formed without adding Nb under the same conditions is about 5,000 times, thus, the high-temperature shape memory alloy having the above-mentioned Nb phase shape has a longer fatigue life.
[0053] In one embodiment, the temperature of the first annealing treatment in step S3 needs to be within a certain temperature range. If the annealing temperature is too low, for example, less than 650°C, the tensile strength of the material will also decrease, making the material more fragile, which is not conducive to cold drawing to form fine wires; if the annealing temperature is too high, for example, greater than 800°C, the hardness and strength of the material will decrease. For this reason, in this embodiment, the temperature of the first annealing treatment in step S3 is between 650°C and 800°C, specifically 650°C, 700°C, 750°C, and 800°C, so as to ensure that the thick wire is cold drawn into a fine wire with a desired diameter, while ensuring the hardness and strength of the material and the uniformity of the material structure.
[0054] In one embodiment, the temperature of the second annealing treatment in step S4 needs to be within a certain temperature range. If the annealing temperature is too low, for example, less than 750°C, it is not conducive to regulating the Nb phase into a spherical or rod-shaped shape. For example, fibrous Nb is not conducive to improving the elongation of the high-temperature shape memory alloy. If the annealing temperature is too high, for example, exceeding 850°C, the risk of material fracture will increase. For this reason, in this embodiment, the temperature of the second annealing treatment in step S4 is between 750°C and 850°C, specifically 750°C, 800°C, and 850°C, so that the Nb phase in the material can be regulated into a spherical or rod-shaped shape to improve the elongation of the high-temperature shape memory alloy.
[0055] In one embodiment, the ratio of the maximum length dimension of the Nb phase in the high temperature shape memory alloy to the diameter of the Nb phase is between 1 and 50.
[0056] As described above, the shape of the Nb phase regulated by the second step annealing treatment is spherical or rod-shaped. For example, when the shape of the Nb phase is a cylindrical rod, the Nb phase has a length and a diameter, and the ratio of its length to diameter is within 50 and greater than 1; for example, when the shape of the Nb phase is a sphere with a circular cross-section, its length in all directions is equal, which can also be understood as the length and diameter of the spherical Nb phase are equal, that is, the ratio of its length to diameter is 1. In this embodiment, by making the ratio between the maximum length dimension of the Nb phase and the diameter of the Nb phase between 1 and 50, the elongation of the high temperature shape memory alloy can be improved, and the fatigue life can be improved at the same time.
[0057] In one embodiment, the maximum length of the niobium phase is between 15nm and 200nm. As described above, the Nb phase can be spherical or rod-shaped. For the rod-shaped Nb phase, its maximum length is the length of the axial direction of the rod-shaped structure. For the spherical Nb phase with a circular cross-section, its maximum length is the diameter of the sphere. For the spherical Nb with an elliptical cross-section, its maximum length is the long diameter of the ellipse. By adjusting the maximum length of the Nb phase to between 15nm and 200nm, it can be ensured that the high-temperature shape memory alloy in this embodiment has a large elongation and fatigue life.
[0058] In one embodiment, before step S2, the method further comprises: sequentially forging, hot rolling and coiling the clean ingot obtained in step S1, so as to facilitate obtaining an ingot with a uniform material structure.
[0059] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims
1. A high temperature shape memory alloy, characterized in that: The chemical composition by mass percentage is: titanium 25-35%, nickel 45-55%, hafnium 12-18%, and niobium 6-10%.
2. A method for preparing a high temperature shape memory alloy, characterized in that: The steps include: Vacuum melting of titanium, nickel, hafnium and niobium to obtain pure ingots; Performing hot drawing on the pure ingot to obtain a memory alloy coarse wire; The memory alloy thick wire is subjected to continuous cold drawing treatment, and then subjected to a first step of annealing treatment to obtain a memory alloy thin wire; The memory alloy filaments are subjected to a second annealing treatment to adjust the shape of the niobium phase into a spherical shape and / or a rod shape.
3. The method for preparing a high temperature shape memory alloy according to claim 2, characterized in that: The temperature of the first step annealing treatment is between 650°C and 800°C.
4. The method for preparing a high temperature shape memory alloy according to claim 2, characterized in that: The temperature of the second annealing treatment is between 750°C and 850°C.
5. The method for preparing a high temperature shape memory alloy according to claim 2, characterized in that: The ratio of the maximum length dimension of the niobium phase to the diameter of the niobium phase is between 1 and 50.
6. The method for preparing a high temperature shape memory alloy according to claim 2, characterized in that: The maximum length dimension of the niobium phase is between 15 nm and 200 nm.
7. The method for preparing a high temperature shape memory alloy according to claim 2, characterized in that: The cross section of the sphere is circular or elliptical.
8. The method for preparing a high temperature shape memory alloy according to claim 2, characterized in that: Before hot drawing the clean ingot, the method further comprises: The clean ingot is subjected to forging, hot rolling and coiling treatment in sequence.
9. The method for preparing a high temperature shape memory alloy according to claim 2, characterized in that: The vacuum melting of titanium, nickel, hafnium and niobium specifically comprises: Vacuum levitation melting or vacuum consumable melting of titanium, nickel, hafnium and niobium.
10. A driver, characterized in that: The actuator is made of the high temperature shape memory alloy according to claim 1.