Mn-Ni-Sn-Cu series shape memory alloy and preparation method thereof

Abstract

The invention relates to a Mn-Ni-Sn-Cu series shape memory alloy and a preparation method of the Mn-Ni-Sn-Cu series shape memory alloy. The chemical formula of the alloy is Mn2NiSn (1-x) Cux, wherein x is more than or equal to 0.725 and less than or equal to 0.85, and x represents the number of Cu atoms in the chemical formula; the shape memory alloy is in the form of a rapid quenching polycrystalline thin strip, and the thickness of the shape memory alloy is about 30-60 microns. A conventional electric arc melting-rapid quenching process flow is adopted in the preparation method, and the preparation method is simple, convenient and feasible. The martensite phase transformation temperature of the material covers the range of 55-316 K through Cu content change, and the application requirement from a liquid nitrogen cryogenic temperature zone to the room temperature can be met; in addition, as a common metal element which is widely used, Cu is low in price, and as a doping element, Cu is beneficial to keeping the advantage of low cost of the Mn-Ni-Sn alloy.

Description

Technical Field

[0001] This invention belongs to the field of functional metal materials technology, specifically relating to a Mn-Ni-Cu-Sn shape memory alloy thin strip material with good mechanical properties, a wide and continuously adjustable phase transformation temperature range, and its preparation method. Background Technology

[0002] Shape memory alloys (SMAs), as smart materials capable of reversibly deforming in response to external physical fields such as temperature and stress, have crucial applications in aerospace, biomedicine, precision machinery, and energy conservation and environmental protection. The physical basis for the shape memory effect in these materials lies in the thermoelastic martensitic phase transformation. Heusler alloys, such as Ni₂MnGa and Ni-Mn-In, are important examples of shape memory alloys, exhibiting significant shape memory effects and a series of practically valuable physical properties, including magnetocaloric and elasto-thermo-thermal properties, making them promising shape memory alloy materials. However, most existing Heusler-type shape memory alloys still suffer from some common problems that affect their practical applications. For example, the materials often contain a high proportion of high-value metal elements such as Ga and In, which increases the production cost and limits large-scale production. Furthermore, since Heusler alloys are essentially intermetallic compounds formed by transition metals and main metals, the chemical bonds within them have strong covalent properties, resulting in significant intrinsic brittleness within the material. This makes them prone to fracture under stress and has poor machinability, thus limiting their engineering applications.

[0003] To reduce costs and further improve the practical performance of materials, and to reduce the use of expensive raw materials, developing relatively inexpensive Mn-Ni-Sn Heusler-type shape memory alloys is a feasible approach. However, since typical positively fractionated Heusler alloys (i.e., the atomic ratio of Mn, Ni, and Sn is the usual 2:1:1 ratio in Heusler alloys) Mn2NiSn itself cannot undergo martensitic phase transformation, further adjustments to its composition are necessary. For example, H. Rekik et al. (Structura and martensitic transformation of MnNiSn shape memory alloys, Int. J. Adv.Manuf. Technol. 90 (2017) 291) disclosed a series of partially fractionated (i.e., the atomic ratio of Mn, Ni, and Sn deviates from the usual 2:1:1 ratio in Heusler alloys) Mn-Ni-Sn shape memory alloys. 50 Ni 50-x Sn xThe (x = 7, 8.7, 10.5) material, compared to the positive composition, exhibits shape memory effect by increasing the proportion of Ni in the material, allowing the series of alloys to undergo martensitic transformation at 300 K-394 K with variations in Sn composition. However, due to the strong covalent bonds between Sn, Ni, and Mn, this series of Mn-Ni-Sn alloys is brittle and prone to cleavage fracture. Therefore, the existing Mn-Ni-Sn alloys still do not solve the problem of intrinsic brittleness. Under conventional machining or low stress, the material may fracture brittlely, making it difficult to process into functional devices. Even if it can be fabricated into devices, microcrack propagation during use can easily lead to failure. These factors hinder the large-scale industrial application of such materials and remain a problem that needs to be solved.

[0004] Therefore, while maintaining the low-cost advantage of Mn-Ni-Sn Heusler alloys, developing new compositions and preparation methods to enhance the plasticity of Mn-Ni-Sn alloys and enabling the phase transformation temperature to cover a wide temperature range through simple compositional changes will significantly improve the practical value of such materials and promote their engineering applications. Summary of the Invention

[0005] The purpose of this invention is to overcome the performance deficiencies of existing Mn-Ni-Sn Heusler-type shape memory alloys and to provide a Mn-Ni-Sn-Cu-based shape memory alloy and its preparation method. This alloy, based on Mn2NiSn, is doped with Cu, which, while maintaining the Heusler alloy structure, enables the material to undergo a martensitic phase transformation and significantly reduces its intrinsic brittleness, resulting in Mn2NiSn with a wide phase transformation temperature range. 1-x Cu x (0.725≤x≤0.85) Shape memory alloy material; the preparation method adopts a conventional arc melting-rapid quenching process, which is simple and easy to implement. This invention uses variations in Cu content to allow the material's martensitic transformation temperature to cover the range of 55 K-316 K, meeting application requirements from liquid nitrogen cryogenic temperatures to room temperature. Furthermore, Cu, as a widely used and common metallic element, is relatively inexpensive, and its use as a dopant element helps maintain the low-cost advantage of Mn-Ni-Sn alloys.

[0006] The technical solution of this invention is as follows: A Mn-Ni-Sn-Cu based shape memory alloy, the chemical formula of which is: Mn2NiSn 1-x Cu x Where 0.725≤x≤0.85, x represents the number of Cu atoms in the aforementioned chemical formula.

[0007] The Mn-Ni-Sn-Cu shape memory alloy is a rapidly quenched polycrystalline thin strip with a thickness of approximately 30-60 μm.

[0008] The preparation method of the Mn-Ni-Sn-Cu shape memory alloy includes the following steps: (1) Preparation of alloy ingots: The raw materials used are elemental Mn, Ni, Sn, and Cu. First, according to the chemical formula Mn₂NiSn… 1-x Cu x Calculate and weigh the required mass of each elemental raw material, place the weighed raw material into the crucible of a vacuum arc melting furnace, and obtain Mn2NiSn by arc melting. 1-x Cu x Alloy ingot; the obtained alloy ingot is wrapped with tantalum sheet and placed in a sealed vacuum quartz tube and annealed at 800-900 °C for 12-24 hours, and then cooled to room temperature to obtain an alloy ingot for preparing rapidly quenched thin strips. The smelting conditions are: the vacuum degree in the smelting chamber reaches 1×10⁻⁶. -3 -5×10 -3 After the Pa range, argon gas is introduced into it to 0.02-0.05 MPa. Argon gas protection is used throughout the entire alloy melting process. The melting current is 55-70 A. Each alloy ingot is turned over 3-4 times during the entire melting process, and a total of 4-5 meltings are performed to ensure that the resulting alloy composition is uniform.

[0009] (2) Preparation of rapidly quenched thin strips: After cleaning the oxide layer from the surface of the annealed alloy ingot, place it inside a quartz tube with a hole at the bottom, fix it in the furnace chamber of the strip spinning machine, and evacuate the furnace chamber to a vacuum level of 1×10⁻⁶. -3 -5×10 -3 The furnace is then purged with argon gas at a pressure of -0.1 to -0.05 MPa. Induction heating or resistance heating is used to bring the alloy to a molten state. Argon gas is then blown in from the top of the quartz tube to spray the molten liquid alloy from the bottom hole onto a rotating copper roller with a linear velocity of 23-30 m / s and quickly eject it, resulting in a polycrystalline fast-quenched strip with a width of 3-7 mm and a thickness of 30-60 μm.

[0010] The purity of the argon gas is greater than or equal to 99%.

[0011] The essential features of this invention are: The current material Mn2NiSn is a typical positively fractionated Mn-based Heusler alloy, but due to its high Sn content, its valence electron concentration is low. It is generally believed that the phase transformation temperature of Heusler-type shape memory alloys is directly proportional to their valence electron concentration; therefore, a low valence electron concentration is unfavorable for the material to undergo a martensitic phase transformation. Mn2NiSn, however, cannot actually undergo a martensitic phase transformation and possess shape memory effects. Separately fractionated Mn-Ni-Sn alloys, such as Mn... 50 Ni 50-x Sn x (x = 7, 8.7, 10.5) Although it can undergo martensitic phase transformation, it is obviously brittle and prone to cleavage fracture, which limits its practical application.

[0012] This invention involves doping Mn2NiSn with Cu to partially replace Sn (Mn2NiSn). 1-x Cu x (0.725≤x≤0.85)), taking advantage of the fact that Cu has more outer valence electrons than Sn, the yield of Mn2NiSn is improved. 1-x Cu x The concentration of valence electrons in the alloy promotes the martensitic phase transformation in the material. Furthermore, as the Cu doping concentration increases, the valence electron concentration continuously increases, leading to a corresponding increase in the phase transformation temperature, thus achieving coverage from liquid nitrogen to room temperature. The brittleness of Mn-Ni-Sn alloys is closely related to the covalent bonds in the material, especially the covalent bonds between the main group element Sn and Ni or Mn. In this invention, after replacing a large amount of Sn with the transition element Cu, the chemical bonds between Cu and Ni or Mn are predominantly metallic bonds. A key characteristic of metallic bonds is their lack of directionality and saturation, thereby enhancing the plasticity of the doped material. The question remains: how to improve the valence electron concentration of Cu in Mn2NiSn alloys... 1-x Cu x The doping level in the alloy, and avoiding the formation of a second phase, is a key issue of this invention. Rapid quenching is a material preparation method with extremely fast cooling rates, which can solidify the alloy from the liquid phase to the solid phase in a very short time. This, to a certain extent, suppresses the segregation of different phases in the material and the formation of a second phase, thus obtaining Mn2NiSn with high Cu doping. 1-x Cu x Alloy. Through the above measures, this invention ultimately achieves a class of Mn2NiSn alloys with good plasticity and a wide phase transformation temperature range. 1-x Cu x Shape memory alloy materials.

[0013] The beneficial effects of this invention are as follows: The Mn2NiSn provided by this invention 1-x Cu xShape memory alloys and their preparation methods are described, featuring simple and direct material synthesis, uniform and accurate material composition, good single-phase properties, and good plasticity. Through Cu doping, shape memory alloys are developed in Mn2NiSn... 1-x Cu x A martensitic phase transformation was achieved in Mn2NiSn, resulting in a new shape memory alloy material. The material's plasticity was significantly improved compared to before Cu doping. This was achieved by changing the Cu doping amount in the material. 1-x Cu x It can achieve a martensitic phase transformation that is continuously adjustable from 55 K to 316 K, with a wide phase transformation temperature range, adapting to various application needs from the cryogenic temperature range of liquid nitrogen to room temperature; and all components of the material are common metallic elements, without involving high-value components such as Ga and In commonly used in Heusler-type shape memory alloys, so the raw material cost is low, which is conducive to large-scale industrial production and application. Attached Figure Description

[0014] Figure 1 It is Mn2NiSn in Example 1 0.2 Cu 0.8 X-ray diffraction pattern of alloy ribbon; Figure 2 It is Mn2NiSn in Example 1 0.2 Cu 0.8 Magnetization-temperature relationship curve of alloy strip; Figure 3 It is Mn2NiSn in Example 1 0.2 Cu 0.8 Resistance measurement results and DSC curves of alloy strips; Figure 4 It is Mn2NiSn in Example 2 0.15 Cu 0.85 X-ray diffraction pattern of alloy ribbon and its relationship with Mn2NiSn 0.15 Cu 0.85 Comparison of X-ray diffraction patterns of alloy ingots; Figure 5 It is Mn2NiSn in Example 2 0.15 Cu 0.85 DSC curve of alloy strip; Figure 6 This is the magnetization-temperature relationship curve of the Mn2NiSn alloy strip in Example 2; Figure 7 It is Mn2NiSn in Example 2 0.15 Cu 0.85 SEM images of the fracture surface of alloy strips and their comparison with SEM images of the fracture surface of Mn2NiSn strips; Figure 8 It is Mn2NiSn in Example 30.275 Cu 0.725 X-ray diffraction pattern of alloy ribbon; Figure 9 It is Mn2NiSn in Example 3 0.275 Cu 0.725 Magnetization intensity-temperature relationship curve of alloy strip. Detailed Implementation

[0015] Example 1: The preparation composition is Mn2NiSn 0.2 Cu 0.8 The rapidly quenched polycrystalline ribbon material was prepared by arc melting at a current of 60A, with argon gas at a positive pressure of 0.03MPa as the protective gas in the furnace chamber. The alloy ingot was melted in a water-cooled copper crucible, and then spun into a ribbon at a speed of 23 m / s using a ribbon spinning machine. The preparation method is as follows: (1) First, according to Mn2NiSn 0.2 Cu 0.8 The required mass of raw materials, namely Mn, Ni, Sn, and Cu, with a purity of 99.9% (the same applies to the following examples), were weighed according to their chemical formulas. The weighed raw materials were then placed in a water-cooled copper crucible in a vacuum arc melting furnace. The furnace cavity was first pre-evacuated to a vacuum of 3 × 10⁻⁶ using a mechanical pump. -1 Pa; then a molecular pump was used to evacuate to 4 × 10 Pa; -3 Pa, then argon gas (99% purity, the purity of argon gas in the following steps and examples is the same) is introduced to 0.03 MPa; after the electrode head is arced, the electrode head is held 1-3 cm above the alloy raw material and repeatedly swung in a small range to melt and mix the raw material with the electric arc. The melting current is 60 A. After the material melts, the melting is stopped after about 2 minutes. After the sample cools and solidifies, it is flipped over and the previous melting steps are repeated; each alloy ingot is flipped three times in the whole melting process, and a total of four meltings are performed to ensure that the alloy composition is uniform; the obtained alloy ingot is wrapped with tantalum sheet and placed in a vacuum-sealed quartz tube and annealed in an annealing furnace at 900°C for 24 hours, and then cooled to room temperature to obtain the alloy ingot used to prepare polycrystalline ribbons.

[0016] (2) Clean the oxides off the surface of the annealed alloy ingot, place it in a quartz tube with a small hole at the bottom, install it in the furnace chamber of the belt spinning machine, and evacuate it to 4×10. -3 Argon gas is introduced into the furnace chamber at a pressure of -0.08 MPa. The alloy ingot is completely melted by induction heating. Then, argon gas is blown in from the top of the quartz tube to spray the molten alloy liquid from the bottom hole onto a high-speed rotating copper roller with a linear velocity of 23 m / s and quickly throw it out to obtain a polycrystalline metal strip with a width of about 6 mm and a thickness of about 50 μm. (3) The obtained Mn2NiSn 0.2Cu 0.8 Performance testing was conducted on rapidly quenched polycrystalline ribbons. The crystal structure of the samples was measured using an X-ray diffractometer, and their X-ray diffraction patterns were observed in... Figure 1 Given, it can be seen that Mn2NiSn 0.2 Cu 0.8 The method demonstrates that the Mn2NiSn alloy exhibits a cubic single-phase structure, proving its ability to synthesize materials with the desired crystal structure. The Mn2NiSn crystal structure was measured using the Quantium Design PPMS system. 0.2 Cu 0.8 The relationship between magnetization and temperature. Figure 2 The magnetization-temperature curves of the sample show that the cooling and heating processes involve a phase transformation from austenite to martensite and a reverse phase transformation from martensite to austenite, respectively, with the martensitic phase transformation temperature range around 230K. The resistance-temperature relationship measured by PPMS and the DSC curve measured by differential scanning calorimetry also confirm the existence of the martensitic phase transformation. Figure 3 Mn2NiSn 0.2 Cu 0.8 The resistance of the thin strip sample and the DSC measurement results show that the resistance increases sharply at the martensitic phase transformation temperature, and the DSC curve shows obvious exothermic and endothermic peaks during the temperature change process, which confirms that there is a thermoelastic martensitic phase transformation in the material, and it can be used as a shape memory alloy.

[0017] Example 2: The preparation composition is Mn2NiSn 0.15 Cu 0.85 Polycrystalline alloy strip material was prepared by arc melting at a current of 70A, with argon gas at a positive pressure of 0.04 MPa as the protective gas in the furnace chamber. The alloy ingot was melted in a water-cooled copper crucible, and then spun into a strip at a speed of 30 m / s using a strip spinning machine. The preparation method is as follows: (1) First, according to Mn2NiSn 0.15 Cu 0.85 The chemical formulas of Mn, Ni, Sn, and Cu raw materials were calculated and weighed to obtain the required mass. The weighed raw materials were then placed in the crucible of the vacuum arc melting furnace. The furnace cavity was first pre-evacuated to a vacuum of 3 × 10⁻⁶ using a mechanical pump. -1 Pa; then a molecular pump was used to evacuate to 3 × 10 Pa; -3Pa, then argon gas is introduced to 0.04 MPa; after the electrode tip is arced, the electrode tip is held 1-3 cm above the alloy material and repeatedly oscillated in a small range to melt and mix the material with the electric arc. The melting current is 70 A. The melting is stopped about 2 minutes after the material melts. After the sample solidifies, it is flipped over and the previous melting steps are repeated; each alloy ingot is flipped three times during the whole melting process, and a total of four meltings are performed to ensure that the alloy composition is uniform; the obtained alloy ingot is wrapped with tantalum sheet and placed in a sealed vacuum quartz tube and annealed at 900 °C for 12 hours, and then cooled to room temperature to obtain the alloy ingot used to prepare polycrystalline ribbons.

[0018] (2) Clean the oxide from the surface of the annealed alloy ingot, place it in a quartz tube with a small hole at the bottom, install it in the furnace chamber of the strip spinning machine, and evacuate it to 5×10. -3 Below Pa, argon gas is introduced into the furnace cavity at a pressure of -0.06 MPa. Induction heating is used to completely melt the alloy ingot. Then, argon gas with a certain pressure is blown in from the top of the quartz tube, causing the molten alloy liquid to be sprayed from the bottom hole onto a high-speed rotating copper wheel with a linear velocity of 30 m / s and quickly thrown out, resulting in a polycrystalline metal strip with a width of about 4 mm and a thickness of about 30 μm. (3) For Mn2NiSn 0.15 Cu 0.85 The sample was tested. The crystal structure of the sample was measured using an X-ray diffractometer, and its X-ray diffraction pattern was observed. Figure 4 The right-hand side of the figure shows the Mn2NiSn at room temperature. 0.15 Cu 0.85 The main phase is a 7M modulated martensite structure, which meets the requirements for crystal structure and shows that its phase transition temperature is higher than room temperature. Figure 5 Differential scanning calorimetry was used to measure Mn2NiSn 0.15 Cu 0.85 The DSC curves showed distinct exothermic and endothermic peaks during the temperature change process, corresponding to the martensitic and reverse phase transformations, respectively. The martensitic phase transformation temperature was 316 K, higher than room temperature. Meanwhile... Figure 4 The left-hand side of the figure also shows the X-ray diffraction pattern of the alloy ingot sample obtained by step (1) in this embodiment. It can be seen that there are obvious diffraction peaks of the second phase, which shows that the rapid quenching method can improve the efficiency of Cu in Mn2NiSn alloys. 1-x Cu x The role of medium solid solubility in obtaining good single-phase alloy materials; To more intuitively demonstrate the promoting effect of Cu doping on the phase transition and the improving effect on the material's plasticity, we prepared undoped Cu-doped positively split Mn2NiSn polycrystalline metal ribbons using the same process conditions as in Example 2 above, and... Figure 6The magnetization-temperature relationship curve is given, showing that no martensitic phase transformation occurred even when the sample was cooled to 5 K, confirming that Mn2NiSn before Cu doping does not have shape memory effect.

[0019] Figure 7 The comparison between Mn2NiSn and Mn2NiSn was conducted. 0.15 Cu 0.85 Scanning electron microscope images of the fracture surface, from Figure 7 The image on the left shows the smooth fracture surface of Mn2NiSn, exhibiting a "candy-like morphology" and river-like patterns of cleavage fractures—typical characteristics of brittle fracture. Figure 7 The middle figure shows Mn2NiSn 0.15 Cu 0.85 The fracture surface has numerous obvious dimples. Figure 7 The fracture side view on the right side shows obvious necking of the sample before fracture, indicating that Cu doping gives the alloy good plasticity.

[0020] Example 3: The preparation composition is Mn2NiSn 0.275 Cu 0.725 Polycrystalline alloy strip material samples were prepared by arc melting at a current of 65A in a water-cooled copper crucible with argon gas at a positive pressure of 0.03MPa as the protective gas. The alloy ingots were then melted and spun into strips at a speed of 23 m / s using a strip spinning machine. The preparation method is as follows: (1) First, according to Mn2NiSn 0.275 Cu 0.725 The chemical formulas of Mn, Ni, Sn, and Cu raw materials were calculated and weighed according to their respective mass values. The weighed raw materials were then placed in the crucible of the vacuum arc melting furnace. The furnace cavity was first pre-evacuated to a vacuum of 3 × 10⁻⁶ using a mechanical pump. -1 Pa; then a molecular pump was used to evacuate to 2 × 10⁻⁶ Pa; -3 Pa, then argon gas is introduced to 0.03 MPa; after the electrode tip is arced, the electrode tip is held 1-3 cm above the alloy material and repeatedly oscillated in a small range to melt and mix the material with the electric arc. The melting current is 65 A. Melting is stopped 2 min after the material melts. After the sample solidifies, it is flipped over and the previous melting steps are repeated; each alloy ingot is flipped three times during the whole melting process, and a total of four meltings are performed to ensure that the alloy composition is uniform; the obtained alloy ingot is wrapped with tantalum sheet and placed in a sealed vacuum quartz tube and annealed at 800 °C for 24 hours, and then cooled to room temperature to obtain the alloy ingot used to prepare polycrystalline ribbons.

[0021] (2) Clean the surface of the annealed alloy ingot, place it in a quartz tube with a small hole at the bottom, install it in the furnace chamber of the belt spinning machine, and evacuate it to 5×10. -3 Below Pa, argon gas is introduced into the furnace cavity at a pressure of -0.1 MPa. Induction heating is used to completely melt the alloy ingot. Then, argon gas with a certain pressure is blown in from the top of the quartz tube, causing the molten alloy liquid to be sprayed from the bottom hole onto a high-speed rotating copper wheel with a linear velocity of 23 m / s and quickly thrown out, resulting in a polycrystalline metal strip with a width of about 5 mm and a thickness of about 50 μm. (3) Using the obtained Mn2NiSn 0.275 Cu 0.725 The thin strip samples underwent performance testing. The crystal structure of the samples was measured using an X-ray diffractometer; the X-ray diffraction patterns are shown in the attached figure. Figure 8 It can be determined that Mn2NiSn 0.275 Cu 0.725 A single-phase structure of the Heusler alloy was formed, meeting the requirements for the material's crystal structure. The relationship between the sample's magnetization and temperature was measured using the Quantium Design PPMS system, and the results are shown in the attached... Figure 9 Given, it can be seen that Mn2NiSn 0.275 Cu 0.725 Martensitic phase transformation occurs in the middle, and its martensitic phase transformation temperature is 55K.

[0022] The above embodiments demonstrate that the present invention provides a Mn2NiSn 1-x Cu x Shape memory alloys and their preparation methods can yield polycrystalline ribbons with high Cu doping levels and good single-phase properties. Their phase transition temperature can be adjusted from liquid nitrogen to room temperature by varying the Cu content, providing a novel material option for applications such as smart devices and solid-state phase change refrigeration in low-temperature / room-temperature environments. Simultaneously, the addition of Cu significantly improves the material's plasticity, solving the intrinsic brittleness problem commonly found in Mn-Ni-Sn alloys. Finally, the doping element Cu is a commonly used alloying element, inexpensive, and still maintains the low production cost advantage of Mn-Ni-Sn alloys, which is conducive to promoting their industrial application.

[0023] Matters not covered in this invention are common knowledge.

Claims

1. A Mn-Ni-Sn-Cu based shape memory alloy, characterized by, The chemical formula of the alloy is: Mn2NiSn 1-x Cu x ; wherein 0.725≤x≤0.85, x represents the number of Cu atoms in the aforementioned chemical formula.

2. The Mn-Ni-Sn-Cu based shape memory alloy according to claim 1, wherein The Mn-Ni-Sn-Cu shape memory alloy is in the form of quenched polycrystalline thin strip, and the thickness is about 30-60 μm.

3. The method of producing a Mn-Ni-Sn-Cu based shape memory alloy according to claim 1, wherein The method comprises the following steps: (1) preparation of alloy ingot: The raw materials used are the elements Mn, Ni, Sn and Cu in the form of simple substance. First, the chemical formula Mn2NiSn 1-x Cu x The required mass of each simple substance raw material is calculated and weighed, and the weighed raw materials are placed in a crucible of a vacuum arc melting furnace, and an Mn2NiSn 1-x Cu x The alloy ingot is obtained; the obtained alloy ingot is wrapped with a tantalum sheet and then loaded into a sealed vacuum quartz tube for annealing at 800-900 ℃ for 12-24 hours, and then cooled to room temperature to obtain an alloy ingot used for preparing a rapidly quenched thin ribbon. (2) preparation of quenched thin strip: After annealing, the surface oxide layer of the alloy ingot is cleaned, and the alloy ingot is placed in a bottom-holed quartz tube and fixed in a furnace cavity of a spinning machine. The furnace cavity is vacuumized to reach 1x10 -3 -5x10 -3 Pa, then argon is introduced into the furnace cavity at a pressure of -0.1 to -0.05 MPa, the alloy is brought to a molten state by induction heating or resistance heating, argon is blown from the upper part of the quartz tube to make the molten liquid alloy sprayed from the bottom hole to a rotating copper roller at a linear velocity of 23-30 m / s and spun off to obtain a polycrystalline rapidly quenched thin strip.

4. The method of producing a Mn-Ni-Sn-Cu based shape memory alloy according to claim 3, wherein The smelting condition in step (1) is: after the vacuum degree of the smelting chamber reaches 1×10 -3 -5×10 -3 Pa, argon is introduced into the smelting chamber to 0.02-0.05 MPa, the whole alloy smelting process is protected by argon, the smelting current is 55-70 A, each alloy ingot is turned over 3~4 times in the whole smelting process, and is smelted for 4~5 times.

5. The method of producing the Mn-Ni-Sn-Cu based shape memory alloy according to claim 3, wherein The purity of the argon in the step (2) is greater than or equal to 99%.

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