Wide-temperature-range high-elasticity nickel-titanium-chromium shape memory alloy and preparation method thereof

Abstract

This invention provides a wide-temperature-range, high-elasticity nickel-titanium-chromium shape memory alloy and its preparation method. The alloy, by atomic percentage, comprises: 48%–57% nickel, 42%–50% titanium, and 0.5%–5% chromium. Within a temperature range of -100℃ to 200℃, the shape memory alloy exhibits a recoverable strain of 3%–6% and an elastic energy density of 30 MJ / m³. 3 ~50MJ / m 3 Compared to existing nickel-titanium shape memory alloys, the alloy composition and preparation method have been adjusted, enabling the nickel-titanium-chromium shape memory alloy to exhibit excellent superelasticity and low hysteresis in the temperature range of -100℃ to 200℃.

Description

Technical Field

[0001] This invention relates to the technical field of shape memory alloys, and particularly to a wide-temperature-range, high-elasticity nickel-titanium-chromium shape memory alloy and its preparation method. Background Technology

[0002] Shape memory alloys are a class of superelastic smart materials widely used in aerospace, medical devices, artificial intelligence, and emerging solid-state refrigeration. However, as modern exploration technologies continue to expand into extreme conditions such as deep space and polar regions, specialized equipment such as hopping robots or drone catapults place increasingly stringent demands on smart drive materials: these materials must not only possess extremely high mechanical energy absorption and storage capabilities but also maintain stable mechanical responses under drastic temperature changes. Traditional metals exhibit a high degree of overlap between their elastic phase and loading / unloading curves, achieving near 100% elastic energy efficiency, but their linear recoverable strain is typically less than 1%, resulting in low absolute capacity. In contrast, NiTi shape memory alloys undergo stress-induced martensitic transformation above the austenitic transformation end temperature, producing 8%–10% superelastic strain. This large elastic strain endows NiTi alloys with enormous application potential in elastic energy storage.

[0003] However, the efficient utilization of the high elasticity of NiTi alloys is severely limited by the large stress hysteresis. During the loading / unloading cyclic phase transformation, interfacial friction and the generation of internal defects consume mechanical energy, forming a significant stress hysteresis loop. This not only reduces the mechanical energy conversion efficiency but also accelerates the degradation of material properties due to internal heat generation. Furthermore, the extremely high temperature sensitivity of NiTi alloys further limits the application temperature range of their elastic energy storage. The critical phase transformation stress of traditional binary NiTi alloys varies linearly with temperature. At low temperatures, the material cannot rebound due to the lack of reverse phase transformation driving force, completely losing its energy storage function; at high temperatures, the phase transformation stress easily exceeds the yield limit of the parent phase, inducing irreversible plastic damage or even failure. Summary of the Invention

[0004] The purpose of this invention is to provide a wide-temperature-range, high-elasticity nickel-titanium-chromium shape memory alloy and its preparation method, which can exhibit excellent superelasticity and elastic energy storage capacity over a wide temperature range.

[0005] The first aspect of this invention provides a wide-temperature-range, high-elasticity nickel-titanium-chromium shape memory alloy, comprising, by atomic percentage: 48%–57% nickel, 42%–50% titanium, and 0.5%–5% chromium; the shape memory alloy exhibits a recoverable strain of 3%–6% within a temperature range of -100℃ to 200℃, and its elastic energy density is 30 MJ / m². 3 ~50 MJ / m 3 .

[0006] Furthermore, the atomic percentage content includes: 50.5% nickel, 49% titanium, and 0.5% chromium.

[0007] A second aspect of this invention provides a method for preparing a wide-temperature-range, high-elasticity nickel-titanium-chromium shape memory alloy, comprising: Weigh the raw materials, and weigh 48%–57% nickel, 42%–50% titanium, and 0.5%–5% chromium by atomic percentage. Alloy ingots are obtained by mixing and melting weighed nickel, titanium, and chromium. Casting alloy: The alloy ingot is completely melted in a casting mold, and after cooling, an alloy plate-shaped sample is obtained. Homogenization treatment: The alloy plate-shaped sample is placed under vacuum and subjected to high-temperature homogenization treatment to obtain a homogeneous material; Subsequent heat treatment: The homogeneous material undergoes subsequent heat treatment.

[0008] Furthermore, the alloy ingot comprises: Weigh out elemental nickel, elemental titanium, and elemental chromium and place them in an electric arc melting furnace, an induction melting furnace, or a suspension induction melting furnace; After evacuation, a protective gas is introduced. The melting current is adjusted and the melting is repeated. After the melting is completed, the furnace is cooled to room temperature to obtain an alloy ingot.

[0009] Furthermore, the protective gas introduced is high-purity argon.

[0010] Furthermore, during the repeated melting process of adjusting the melting current, if the furnace is placed in an electric arc melting furnace, the melting current is 70A~500A; if the furnace is placed in an induction melting furnace or a suspension induction melting furnace, the melting current is 30A~400A and the frequency is 1000Hz~5000Hz.

[0011] Furthermore, the process of repeatedly melting by adjusting the melting current includes: repeatedly melting the alloy ingot 2 to 8 times, and cooling it to room temperature with the furnace after each melting.

[0012] Furthermore, the casting of the alloy specifically includes: pulling the alloy ingot to the crucible where the casting mold is located, using 30A~500A to remelt the ingot, completing the casting, and waiting for the sample to cool to room temperature to obtain an alloy plate-shaped sample.

[0013] Furthermore, the homogenization process includes: placing the alloy plate-shaped sample in a vacuum quenching furnace, evacuating it to a vacuum state, and performing a homogenization process at 900℃~1200℃ for 1h~24h to eliminate segregation, followed by water quenching to obtain a homogenized material.

[0014] Furthermore, the temperature of the subsequent heat treatment is 200℃~800℃, and the heat treatment time is 0.01h~12h.

[0015] The beneficial effects of this plan are as follows: The nickel-titanium-chromium shape memory alloy of this application, compared with existing nickel-titanium shape memory alloys, has adjusted the alloy composition and preparation method, which can effectively suppress the martensitic phase transformation process while strengthening the alloy matrix. This allows the nickel-titanium-chromium shape memory alloy to exhibit excellent superelasticity and low hysteresis characteristics in the temperature range of -100℃ to 200℃. Within this temperature range, the strain recovery is 3% to 6%, and the elastic energy density reaches 30 MJ / m. 3 ~50 MJ / m 3 The energy efficiency is 90%–99%. By precisely controlling the atomic percentage composition of nickel, titanium, and chromium, the stress hysteresis phenomenon during the phase transformation process is effectively suppressed, significantly improving the mechanical stability of the material under extreme temperature environments. It has a wide operating temperature range and high elastic energy density, and can maintain stable recoverable strain and high energy storage efficiency in the temperature range of -100℃ to 200℃. Attached Figure Description

[0016] Figure 1 This is a flowchart of a method for preparing shape memory alloys provided in an embodiment of this application; Figure 2 This is a compressive stress-strain curve of the shape memory alloy prepared in Example 1 within the temperature range of -100℃ to 200℃; Figure 3 This is a temperature-dependent recoverable strain diagram of the shape memory alloy prepared in Example 1 within the temperature range of -100℃ to 200℃. Figure 4 This is a schematic diagram illustrating the calculation method of the elastic energy density and energy efficiency of the shape memory alloy prepared in Example 1; Figure 5 This is a statistical graph of the elastic energy density and energy efficiency of the shape memory alloy prepared in Example 1 in the temperature range of -100℃ to 200℃. Figure 6 This is a compressive stress-strain curve of the shape memory alloy prepared in Example 2 at room temperature; Figure 7 This is a compressive stress-strain curve of the shape memory alloy prepared in Example 3 at room temperature; Figure 8 This is a compressive stress-strain curve of the shape memory alloy prepared in Example 4 at room temperature; Figure 9 This is the compressive stress-strain curve of the shape memory alloy prepared in Example 5 at room temperature. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] The numerical parameters involved in this application should be broadly understood to include not only the equivalent values ​​obtained by rounding to the same significant figures, but also the reasonable test error range allowed by conventional testing methods in the art when measuring such values.

[0019] All numerical ranges disclosed in this application include the upper and lower limits and all intermediate values ​​in between, and each disclosed range can be combined independently (for example, the range "900 ℃~1200 ℃" includes the limits of 900 ℃ and 1200 ℃, and includes all intermediate values).

[0020] Regarding the temperature parameters defined in this application, it should be stated that such temperatures refer to the ambient temperature of the environment in which the alloy is located or the set parameters of the heating furnace, and do not require the alloy body to reach a corresponding internal temperature.

[0021] In the context of this application, the term "hyperelasticity" refers to the physical property of shape memory alloys, when subjected to external loads, to exhibit strain significantly exceeding the elastic limit (typically ≥1%) of conventional metal structural components, and to spontaneously recover this deformation after the external load is removed. Specifically, materials in the austenitic phase undergo stress-induced martensitic transformation under external stress, causing them to exhibit mechanical behavior deviating from Hooke's Law and exceeding the elastic limit of ordinary materials. The hyperelasticity testing methods in this application are all cyclic compression tests, including two steps: loading and unloading.

[0022] The term "recoverable strain" refers to the amount of strain that a material or structure can recover after being subjected to loading and unloading of forces, reflecting the elastic or hyperelastic mechanical properties of the material or structure.

[0023] The term "elastic energy density" refers to the elastic strain energy per unit volume released by a material during the stress unloading stage. It reflects the material's elastic energy storage capacity and is specifically calculated as the integral area of ​​the stress-strain curve during the unloading stage.

[0024] The term "energy efficiency" refers to the proportion of elastic strain energy released during the unloading phase to the work input during the loading phase. It reflects the efficiency with which a material stores elastic energy. Specifically, it is calculated by dividing the integral area of ​​the stress-strain curve during the unloading phase by the integral area of ​​the stress-strain curve during the loading phase. For materials following Hooke's Law, the energy efficiency during the elastic phase is close to 100%; however, for ordinary NiTi alloys, due to the hysteresis loop between loading and unloading, their energy efficiency is often relatively low.

[0025] The term "temperature range" refers to the temperature range between the extreme high temperature and the extreme low temperature within which a material can serve normally; while the term "wide temperature range" refers to a wide effective environmental temperature range within which a material can maintain its set performance. In this application, a temperature range that spans 100 °C or more can be defined as a wide temperature range.

[0026] The wide-temperature-range, high-elasticity nickel-titanium-chromium shape memory alloy disclosed in this embodiment comprises, by atomic percentage, 48%–57% nickel, 42%–50% titanium, and 0.5%–5% chromium; the shape memory alloy exhibits a recoverable strain of 3%–6% within a temperature range of -100℃ to 200℃, and its elastic energy density is 30 MJ / m³. 3 ~50 MJ / m 3 .

[0027] Nickel-titanium alloys exhibit superelasticity, demonstrating exceptionally large elastic strain and thus possessing significant potential for elastic energy storage. Chromium, as an alloying element, can significantly regulate the properties of nickel-titanium alloys through trace addition. When the atomic percentage of chromium is precisely controlled between 0.5% and 5%, it can effectively lower the phase transformation temperature of the alloy, broaden its operating temperature range, and simultaneously increase its strength, thereby further enhancing the alloy's elastic energy density and recoverable strain capacity over a wide temperature range.

[0028] The method for preparing a wide-temperature-range, high-elasticity nickel-titanium-chromium shape memory alloy disclosed in this embodiment includes: S1. Weigh the raw materials, weighing 48%–57% nickel, 42%–50% titanium, and 0.5%–5% chromium by atomic percentage. S2, alloy ingot: The weighed nickel, titanium and chromium are mixed and smelted to obtain an alloy ingot; Specifically, nickel, titanium, and chromium raw materials are weighed and placed in an electric arc melting furnace, an induction melting furnace, or a suspension induction melting furnace; after evacuation, a protective gas is introduced; the melting current is adjusted and the melting is repeated. After the melting is completed, the furnace is cooled to room temperature to obtain an alloy ingot.

[0029] For example, the weighed raw materials of elemental nickel, elemental titanium, and elemental chromium are placed in a copper crucible of an electric arc melting furnace; a vacuum of 1×10⁻⁶ is then applied.-3 Pa, then argon and other protective gases are introduced; the melting current is adjusted to 70A to 500A for melting, and the melting time for each melting is 1min to 5min; the melting is repeated 4 to 8 times, and the alloy ingot is turned over before each repeated melting. After the melting is completed, the ingot is cooled to room temperature with the furnace to obtain an alloy ingot. The ingot is button-shaped, with a diameter of 5mm to 40mm and a thickness of 1mm to 20mm.

[0030] For example, the weighed raw materials of elemental nickel, elemental titanium, and elemental chromium are placed in the crucible of an induction melting furnace or a suspension induction melting furnace; after evacuation, protective gases such as argon are introduced; the melting current is adjusted to 30A to 400A and the frequency is 1000Hz to 5000Hz for melting; the melting is repeated 2 to 4 times, and after the melting is completed, the furnace is cooled to room temperature to obtain an alloy ingot, which is in the shape of a cylindrical rod.

[0031] Repeated melting of the alloy ingot 2–8 times, ensuring each melting time is between 1 and 5 minutes, effectively promotes the thorough mixing and diffusion of components such as nickel, titanium, and chromium in the liquid phase, significantly reducing the risk of elemental segregation. Simultaneously, flipping the alloy ingot before each repeated melting during arc melting effectively overcomes the gravitational segregation effect, ensuring uniform heating of the melt and further improving the macroscopic and microscopic homogeneity of the alloy. Cooling the furnace to room temperature after each melting helps form a more stable and uniform crystal structure, reducing internal stress and laying a good microstructure foundation for subsequent homogenization and heat treatment.

[0032] S3. Casting alloy: The alloy ingot is completely melted in a casting mold, and after cooling, an alloy plate-shaped sample is obtained. For example, the alloy ingot obtained in step two is placed in the crucible containing the casting mold, and an arc is initiated using a current of 30A to 150A. Finally, the current is increased to 200A to 500A to completely melt the ingot, completing the casting. After the sample cools to room temperature, an alloy plate-shaped sample is obtained. By adopting a staged current control strategy, that is, first initiating the arc with a lower current and then increasing the current for main melting, precise control of the alloy ingot melting process can be achieved.

[0033] S4. Homogenization treatment: The alloy plate-shaped sample is placed under vacuum and subjected to high-temperature homogenization treatment to obtain a homogeneous material. For example, the obtained alloy plate-shaped sample is placed in a vacuum quenching furnace, and after being evacuated to a vacuum state, it is homogenized at 900℃~1200℃ for 1h~24h to eliminate segregation, and then water quenched to obtain a homogenized sample.

[0034] Segregation refers to the phenomenon of uneven chemical composition within an alloy during solidification due to differences in the solubility of different components in the liquid and solid phases. Eliminating segregation is crucial for shape memory alloys because it leads to uneven phase transformation temperatures, decreased mechanical properties, and instability in the shape memory effect. A vacuum environment also facilitates uniform heat transfer, ensuring a uniform temperature distribution within the alloy plate-shaped sample. Homogenization treatment at 900℃–1200℃ for 1–24 hours aims to eliminate compositional segregation formed during casting through atomic diffusion, resulting in a more homogeneous chemical composition and microstructure within the alloy. The temperature range of 900℃–1200℃ provides sufficient atomic diffusion motive force to promote the uniform distribution of segregated elements; the time range of 1h–24h ensures that atoms have enough time to diffuse sufficiently, thereby effectively eliminating segregation.

[0035] S5. Subsequent heat treatment: The homogeneous material undergoes subsequent heat treatment.

[0036] For example, the alloy sample obtained after homogenization is subjected to subsequent heat treatment at a temperature of 200℃ to 800℃ for a time of 0.01h to 12h.

[0037] Subsequent heat treatment is for the purpose of precipitating phases and obtaining better performance. By performing subsequent heat treatment on homogeneous materials and precisely controlling the temperature between 200℃ and 800℃ and the time between 0.01h and 12h, the microstructure of the alloy can be effectively regulated, the formation and distribution of specific precipitates can be promoted, and the internal stress generated in the early preparation process can be fully eliminated.

[0038] Based on the preparation method provided in the embodiments of this application, the prepared nickel-titanium-chromium shape memory alloy exhibits excellent superelasticity and low hysteresis in the temperature range of -100℃ to 200℃. Within this temperature range, the strain recovery is 3% to 6%, and the elastic energy density reaches 30 MJ / m. 3 ~50 MJ / m 3 With an energy efficiency of 90%–99%, this alloy effectively overcomes the problems of traditional shape memory alloys, such as limited mechanical energy absorption and storage capacity, insufficient mechanical response stability, and high temperature sensitivity under extreme working conditions. It provides a smart drive material with stable performance for special equipment such as deep space and polar regions.

[0039] The following examples are provided to illustrate the alloys and preparation methods of this application. These examples are merely illustrative and are not intended to limit the disclosure to the materials, conditions, or process parameters described herein.

[0040] Example 1

[0041] Titanium, nickel, and chromium with a purity of at least 99.9% (mass percentage) are mixed in an atomic percentage ratio of 50.5% nickel (Ni), 49% titanium (Ti), and 0.5% chromium (Cr) and added to an electric arc melting furnace. The furnace is then evacuated to a vacuum of 1×10⁻⁶. -3 Pa, then high-purity argon gas with a purity ≥99% was introduced to melt the raw materials into an alloy. The sample was then flipped and remelted, for a total of 6 melting cycles, each lasting 1 minute, to obtain an alloy ingot. The alloy ingot was then moved to the crucible containing the casting mold, and an arc was ignited using an 80A current. Finally, the current was increased to 200A to completely melt the ingot, completing the casting. After the sample cooled to room temperature, a plate-shaped alloy sample was obtained. The plate-shaped alloy sample was placed in a vacuum quenching furnace, evacuated to a vacuum state, and homogenized at 900℃ for 24 hours to eliminate segregation. Afterward, it was water-quenched to obtain a homogenized sample. The homogenized alloy material was then heat-treated at 400℃ for 2 hours. After heat treatment, it was quickly quenched in room temperature water. This yielded the nickel-titanium-chromium shape memory alloy of Example 1. Figure 2 This is a compressive stress-strain curve of the shape memory alloy prepared in Example 1 of this application within a temperature range of -100℃ to 200℃. Figure 2 As shown, this shape memory alloy exhibits superelastic behavior in an ambient temperature range of -100℃ to 200℃. Figure 3 The recoverable strain of this shape memory alloy at different ambient temperatures within the temperature range of -100℃ to 200℃ is 3.2% to 4.8%. Figure 4 This describes a method for calculating the elastic energy storage and energy efficiency of shape memory alloys. The gray area obtained by integrating the unloading curve represents the elastic energy density, while the hysteresis loop (dashed line area) enclosed by the loading / unloading stress-strain curves represents energy dissipation. Energy efficiency is calculated by dividing the area of ​​the gray area by the sum of the areas of the gray and dashed lines. This shape memory alloy exhibits an elastic energy density of 30 MJ / m² within a temperature range of -100℃ to 200℃. 3 ~48 MJ / m 3 Energy efficiency reaches 93%–99%, such as Figure 5 As shown.

[0042] Example 2

[0043] Titanium, nickel, and chromium with a purity of at least 99.9% (mass percentage) are mixed in an atomic percentage ratio of 48% nickel (Ni), 50% titanium (Ti), and 2% chromium (Cr) and added to an electric arc melting furnace. The furnace is then evacuated to a vacuum of 1×10⁻⁶. -3Pa, then high-purity argon gas with a purity ≥99% was introduced to melt the raw materials into an alloy. The sample was then flipped and remelted, for a total of 4 melting cycles, each lasting 5 minutes, to obtain an alloy ingot. The alloy ingot was then moved to the crucible containing the casting mold, and an arc was ignited using a current of 70A. Finally, the current was increased to 300A to completely melt the ingot, completing the casting. After the sample cooled to room temperature, an alloy plate-shaped sample was obtained. The alloy plate-shaped sample was placed in a vacuum quenching furnace, evacuated to a vacuum state, and homogenized at 1000℃ for 12 hours to eliminate segregation. Afterward, it was water-quenched to obtain a homogenized sample. The homogenized alloy material was then heat-treated at 300℃ for 1 hour. After heat treatment, it was quickly quenched in room temperature water. This yielded the nickel-titanium-chromium shape memory alloy of Example 2. Figure 6 This is the compressive stress-strain curve of the shape memory alloy prepared in Example 2 of this application at room temperature.

[0044] Example 3

[0045] Titanium, nickel, and chromium with a purity of at least 99.9% (mass percentage) are mixed in an atomic percentage ratio of 53% nickel (Ni), 44% titanium (Ti), and 3% chromium (Cr) and added to an electric arc melting furnace. The furnace is then evacuated to a vacuum of 1×10⁻⁶. -3 Pa, then high-purity argon gas with a purity ≥99% was introduced to melt the raw materials into an alloy. The sample was then flipped and remelted, for a total of 8 melting cycles, each lasting 3 minutes, to obtain an alloy ingot. The alloy ingot was then moved to the crucible containing the casting mold, and an arc was ignited using a current of 150A. Finally, the current was increased to 500A to completely melt the ingot, completing the casting. After the sample cooled to room temperature, an alloy plate-shaped sample was obtained. The alloy plate-shaped sample was placed in a vacuum quenching furnace, evacuated to a vacuum state, and homogenized at 1200℃ for 24 hours to eliminate segregation. Afterward, it was water-quenched to obtain a homogenized sample. The homogenized alloy material was then heat-treated at 600℃ for 6 hours. After heat treatment, it was quickly quenched in room temperature water. This yielded the nickel-titanium-chromium shape memory alloy of Example 3. Figure 7 This is the compressive stress-strain curve of the shape memory alloy prepared in Example 3 of this application at room temperature.

[0046] Example 4

[0047] Titanium, nickel, and chromium with a purity of at least 99.9% (mass percentage) are mixed in an atomic percentage ratio of 50% nickel (Ni), 45% titanium (Ti), and 5% chromium (Cr) and added to an induction melting furnace. The furnace is then evacuated to a vacuum of 1×10⁻⁶. -3Pa, then high-purity argon gas with a purity ≥99% was introduced, and the induction melting current was 30A with a frequency of 5000Hz. The melting was repeated three times to obtain a cylindrical alloy ingot. The ingot was then placed in the crucible containing the casting mold, and electricity was applied to completely melt the ingot, completing the casting. After the sample cooled to room temperature, a plate-shaped alloy sample was obtained. The plate-shaped alloy sample was placed in a vacuum quenching furnace, and under vacuum, it underwent homogenization treatment at 1100℃ for 18 hours to eliminate segregation. Afterward, it was water-quenched to obtain a homogenized sample. The homogenized alloy material was then heat-treated at 800℃ for 0.01 hours. After heat treatment, it was quickly quenched in room temperature water. This yielded the nickel-titanium-chromium shape memory alloy of Example 4. Figure 8 This is a compressive stress-strain curve of the shape memory alloy prepared in Example 4 of this application at room temperature.

[0048] Example 5

[0049] Titanium, nickel, and chromium with a purity of at least 99.9% (mass percentage) were mixed in an atomic percentage ratio of 57% nickel (Ni), 42% titanium (Ti), and 1% chromium (Cr) and added to a suspension induction melting furnace. The furnace was then evacuated to a vacuum of 1×10⁻⁶. -3 Pa, then high-purity argon gas with a purity ≥99% was introduced, and the suspension induction melting current was 400A with a frequency of 1000Hz, and melting was performed twice to obtain a cylindrical alloy ingot. The alloy ingot was then placed in the crucible containing the casting mold, and electricity was applied to completely melt the ingot, completing the casting. After the sample cooled to room temperature, a plate-shaped alloy sample was obtained. The plate-shaped alloy sample was placed in a vacuum quenching furnace, and under vacuum, it underwent homogenization treatment at 900℃ for 16 hours to eliminate segregation, followed by water quenching to obtain a homogenized sample. The homogenized alloy material was then heat-treated at 400℃ for 3 hours. After heat treatment, it was quickly quenched in room temperature water. This yielded the nickel-titanium-chromium shape memory alloy of Example 5. Figure 9 This is a compressive stress-strain curve of the shape memory alloy prepared in Example 5 of this application at room temperature.

[0050] It needs to be explained that, Figure 2 , Figures 6-9 The figure shows the superelastic compressive stress-strain curves of the shape memory alloys prepared in Examples 1-5 at room temperature. The upper and lower curves in the figure represent the stress-strain curves under loading and unloading, respectively. Unlike general linear elastic alloys, the alloys in Examples 1-5 do not have completely overlapping loading and unloading curves, exhibiting particularly large elastic strain and a very small hysteresis area.

[0051] The performance comparison of the shape memory alloys of Examples 1-5 in the temperature range of -100℃ to 200℃ is shown in Table 1 below.

[0052] Table 1 As shown in Table 1, the nickel-titanium-chromium shape memory alloys prepared in Examples 1-5 of this scheme exhibit excellent superelasticity and low hysteresis in the temperature range of -100℃ to 200℃.

[0053] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A wide temperature range, high ductility nickel-titanium-chromium shape memory alloy characterized in that, Based on atomic percentage content, it includes: 48%–57% nickel, 42%–50% titanium, and 0.5%–5% chromium; the shape memory alloy has a recoverable strain of 3%–6% within a temperature range of -100℃ to 200℃, and its elastic energy density is 30 MJ / m³. 3 ~50 MJ / m 3 .

2. The wide temperature range, high energy nickel-titanium-chromium shape memory alloy of claim 1, wherein, The composition, by atomic percentage, includes: 50.5% nickel, 49% titanium, and 0.5% chromium.

3. A method for preparing a wide temperature range high elastic property nickel-titanium-chromium shape memory alloy, characterized in that, include: Weigh the raw materials, and weigh 48%–57% nickel, 42%–50% titanium, and 0.5%–5% chromium by atomic percentage. Alloy ingots are obtained by mixing and melting weighed nickel, titanium, and chromium. Casting alloy: The alloy ingot is completely melted in a casting mold, and after cooling, an alloy strip sample is obtained. Homogenization treatment: The alloy plate-shaped sample is placed under vacuum and subjected to high-temperature homogenization treatment to obtain a homogeneous material; Subsequent heat treatment: The homogeneous material undergoes subsequent heat treatment.

4. The method for preparing a wide-temperature-range, high-elasticity nickel-titanium-chromium shape memory alloy according to claim 3, characterized in that, The alloy ingot comprises: The weighed nickel, titanium and chromium are placed in an electric arc furnace, an induction furnace or a suspension induction furnace; After evacuation, a protective gas is introduced. The melting current is adjusted and the melting is repeated. After the melting is completed, the furnace is cooled to room temperature to obtain an alloy ingot.

5. The method for preparing a wide-temperature-range, high-elasticity nickel-titanium-chromium shape memory alloy according to claim 4, characterized in that, The protective gas introduced is high-purity argon.

6. The method for preparing a wide-temperature-range, high-elasticity nickel-titanium-chromium shape memory alloy according to claim 4, characterized in that, During the repeated melting process of adjusting the melting current, if the furnace is placed in an electric arc melting furnace, the melting current is 70A~500A; if the furnace is placed in an induction melting furnace or a suspension induction melting furnace, the melting current is 30A~400A and the frequency is 1000Hz~5000Hz.

7. The method for preparing a wide-temperature-range, high-elasticity nickel-titanium-chromium shape memory alloy according to claim 4, characterized in that, The process of repeatedly melting by adjusting the melting current includes: repeatedly melting the alloy ingot 2 to 8 times, and cooling it to room temperature with the furnace after each melting.

8. The method for preparing a wide-temperature-range, high-elasticity nickel-titanium-chromium shape memory alloy according to claim 3, characterized in that, The casting of the alloy specifically includes: placing the alloy ingot into the crucible where the casting mold is located, using a current of 30A to 500A to remelt the ingot, completing the casting, and waiting for the sample to cool to room temperature to obtain an alloy plate-shaped sample.

9. The method for preparing a wide-temperature-range, high-elasticity nickel-titanium-chromium shape memory alloy according to claim 3, characterized in that, The homogenization process includes: placing the alloy plate-shaped sample in a vacuum quenching furnace, drawing a vacuum, and performing a homogenization process at 900℃~1200℃ for 1h~24h to eliminate segregation, followed by water quenching to obtain a homogenized material.

10. The method for preparing a wide-temperature-range, high-elasticity nickel-titanium-chromium shape memory alloy according to claim 3, characterized in that, The subsequent heat treatment temperature is 200℃~800℃, and the heat treatment time is 0.01h~12h.

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