Mn-Fe-Cu-Ga alloy carbide negative thermal expansion material and preparation method thereof

Abstract

The invention relates to a Mn-Fe-Cu-Ga alloy carbide negative thermal expansion material and a preparation method thereof. The chemical formula of the material is Mn < 50 > Fe < 25-x > Cu < x > Ga < 25 > C < y >, wherein x is larger than or equal to 7.5 and smaller than or equal to 15, y is larger than or equal to 2.5 and smaller than or equal to 5, and x and y represent the atomic ratio of Cu and C in the chemical formula; the form of the negative thermal expansion material is a polycrystalline ribbon material or a polycrystalline rod-like material. During preparation, the negative thermal expansion material with accurate carbon content and uniform components can be synthesized directly through electric arc melting and subsequent rapid quenching or suction casting, and the preparation method is suitable for large-scale industrial production. The material obtained by the method has the advantages of low carbon doping amount and simple and convenient preparation process, the negative thermal expansion temperature range of the material prepared by the method is mainly in the range of 300K-385K, the common working temperature range of devices and equipment is covered, and meanwhile, the material has good mechanical properties and can meet the processing and use requirements of precise devices.

Description

Technical Field

[0001] The present invention belongs to the field of functional materials, and provides a negative thermal expansion material based on Mn-Fe-Cu-Ga alloy carbide and a preparation method thereof. Background Art

[0002] The positive thermal expansion phenomenon that the size and volume of materials increase with the increase of temperature is an inherent property of conventional materials. Its microscopic mechanism lies in the anharmonic vibration of the material lattice caused by temperature. This thermal vibration will cause the distance between atoms in the lattice to continuously increase with the increase of temperature, and macroscopically it is manifested as the thermal expansion of the material. The thermal expansion of materials is generally related to their crystal structure, microstructure, defects, and magnetism, etc. As a common physical phenomenon, the thermal expansion phenomenon has an important impact in the engineering field and has become a problem that must be considered in the design and use of equipment and devices. Especially in the fields of aerospace, microelectronics, optics, precision instruments and meters, etc., there are often high requirements for the precision and stability of devices. When the temperature changes, the instrument accuracy cannot be reduced due to thermal expansion, or thermal stress and microscale mismatch cannot occur, resulting in product failure. To solve this problem, it is necessary to obtain a class of materials with negative thermal expansion, whose size and volume decrease with the increase of temperature in a certain temperature range, so as to be compounded and compensated with the positive thermal expansion of conventional materials, and achieve approximately no change in size in the working temperature range of the device. Therefore, as a functional material, negative thermal expansion materials can be used for the design and control of the thermal expansion performance of devices, and have important application values in many fields such as optical instruments, precision instruments, and advanced electronic devices.

[0003] The realization mechanisms of negative thermal expansion materials can be divided into two categories. One is the phonon mechanism, such as metal-organic framework materials, etc.; the other is the electron mechanism, including magnetic materials, ferroelectric materials, etc. So far, the discovered negative thermal expansion materials include Invar alloys, zirconium tungstate, some rare earth intermetallic compounds, metal cyanides, Mn alloy nitrides / carbides Mn3AN and Mn3AC (A represents some transition or main group elements), etc. Among them, Mn alloy nitrides / carbides such as Mn3GaN have the temperature range and expansion amount of negative thermal expansion that can be adjusted within a large range, and the materials have good electrical and thermal conductivity characteristics and hardness close to that of steel, etc., becoming a class of negative thermal expansion materials with promising development prospects.

[0004] However, there are still a series of problems that limit the practical application of Mn alloy nitrides / carbides Mn3AN and Mn3AC as negative thermal expansion materials. First of all, only when they contain a large amount of nitrogen and carbon components can the materials exhibit negative thermal expansion effects, which makes it difficult to directly prepare them by conventional alloy melting methods, and they can only be achieved by long-term diffusion annealing of raw material powders and other means. For example, in the literature "Negative thermal expansion, magnetic and electronic transport properties in antiperovskite compounds Mn3Ga 1-x Ag x N(0≤x≤1.0)", the Mn3Ga 1-x Ag x N(0≤x≤1.0) alloy. Its preparation process first requires high-temperature annealing of Mn powder in a nitrogen environment to obtain Mn2N, then mixing Mn2N, Ga, and Ag powders in proportion for grinding, and finally continuing long-term annealing of the ground powder to obtain it. The literature "Role of Tin and Carbon in the magnetic interactions in Mn3SnC" prepared an Mn alloy carbide material with negative thermal expansion effects. The preparation method is to first mix Mn, Sn, and graphite powders in proportion, press the powder into tablets, anneal at 1073K for 48 hours first, then anneal at 1150K for 120 hours, and then crush and grind the tablets and repeat the above annealing steps once to obtain the finished product. During the preparation of the sample, in order to ensure the full reaction of C, an additional 15% graphite powder needs to be added based on the nominal composition. The above preparation methods are not only cumbersome and time-consuming, but also difficult to well control the composition accuracy and uniformity of the obtained products, which is not conducive to the large-scale synthesis and application of materials. In addition, due to the high nitrogen and carbon content in the material composition, its hardness is very high, but its toughness or ductility is poor, which brings many difficulties to the processing of devices, especially precision devices with complex shapes, and limits the practical application of the material.

[0005] Therefore, it has practical significance in engineering to develop negative thermal expansion materials with simple preparation methods, good mechanical properties, obvious negative thermal expansion effects, and a wide negative thermal expansion temperature range. Summary of the Invention

[0006] The primary purpose of the present invention is to overcome the deficiencies in the preparation process and performance of existing Mn alloy nitrogen / carbide negative thermal expansion materials, and propose a Mn-Fe-Cu-Ga alloy carbide negative thermal expansion material and its preparation method. By adding Fe and Cu elements, the material reduces the doping amount of carbon elements required to achieve negative thermal expansion, so that the material can be synthesized by a more commonly used method and directly obtain a bulk material; during the preparation, a negative thermal expansion material with accurate carbon content and uniform composition can be synthesized directly by arc melting and subsequent rapid quenching or suction casting, which is suitable for large-scale industrial production. The material obtained by the present invention has the advantages of low carbon doping and simple preparation process. The negative thermal expansion temperature range of the material prepared by this method is mainly in the range of 300K-385K, covering the common operating temperature range of devices and equipment. At the same time, the material has good mechanical properties and can meet the needs of precision device processing and use.

[0007] The technical solution of the present invention is:

[0008] A Mn-Fe-Cu-Ga alloy carbide negative thermal expansion material, the chemical formula of which is: Mn 50 Fe 25-x Cu x Ga 25 C y ; Wherein, 7.5≤x≤15, 2.5≤y≤5, the subscript symbol of the element is the atomic ratio of the element, and the sum of the atomic numbers of Mn, Fe, Cu and Ga is 100;

[0009] The negative thermal expansion material is in the form of a polycrystalline thin ribbon material or a polycrystalline rod material.

[0010] The preparation method of the Mn-Fe-Cu-Ga alloy carbide negative thermal expansion material is any of the following two methods:

[0011] Method 1, preparation of polycrystalline thin ribbon material, comprising the following steps:

[0012] (1) According to the chemical formula Mn 50 Fe 25-x Cu x Ga 25 C y Weigh the required mass of each component raw material, put pure Mn, pure Fe, pure Cu, pure Ga and carbon into the crucible of vacuum arc melting furnace, and perform arc melting under argon atmosphere protection to obtain Mn 50 Fe 25-x Cu x Ga 25 C yAlloy ingots; the obtained alloy ingots are wrapped with tantalum sheets and then placed in a sealed vacuum quartz tube for annealing at 800 - 900 °C for 12 - 24 hours, and then cooled to room temperature to obtain alloy ingots for preparing polycrystalline thin strips;

[0013] Among them, the melting conditions adopted are: when the vacuum degree in the melting chamber reaches 2×10 -3 -5×10 -3 Pa, argon gas is introduced into it until the pressure reaches 0.02 - 0.06 MPa; the melting current is 50 - 70 A, and each alloy ingot is flipped 2 - 4 times during the whole melting process;

[0014] The purities of pure Mn, pure Fe, pure Cu, pure Ga, and pure C are all 99.9%;

[0015] (2) Clean the surface of the annealed alloy ingot, place it in a quartz tube with an opening at the bottom, fix it in the furnace cavity of a strip casting machine, evacuate to make the vacuum in the furnace cavity reach 2×10 -3 -5×10 -3 Pa, introduce high-purity argon gas into the furnace cavity, with the pressure being -0.1 to -0.05 MPa, use induction heating or resistance heating to make the alloy in a molten state, and then blow high-purity argon gas from the upper part of the quartz tube to make the molten alloy liquid spray out from the small hole at the bottom onto a rotating copper wheel with a linear velocity of 15 - 20 m / s and be rapidly ejected to obtain a polycrystalline metal thin strip material with a width of 3 - 7 mm and a thickness of 50 - 90 μm;

[0016] The purity of the high-purity argon gas described is 99.9%;

[0017] Or, Method 2, preparation of polycrystalline suction casting materials, includes the following steps:

[0018] (1) First, weigh the raw materials of each component required according to the chemical formula Mn 50 Fe 25-x Cu x Ga 25 C y Weigh the raw materials of each component required, put the weighed raw materials into the crucible of an arc melting furnace, and use the arc melting method to obtain Mn 50 Fe 25-x Cu x Ga 25 C y Alloy ingots;

[0019] Among them, the melting conditions adopted are: when the vacuum in the melting chamber reaches 2×10 -3 -5×10 -3At 0.02 - 0.06 MPa, argon gas is introduced into it until the pressure reaches 0.02 - 0.06 MPa. During the entire melting process, the sample is protected by argon gas. The melting current is 50 - 70 A, and each alloy ingot is flipped 2 - 4 times during the entire melting process. The obtained alloy ingots are wrapped with tantalum sheets and then 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 alloy ingots for preparing suction casting rods.

[0020] (2) Clean the surface of the annealed polycrystalline alloy ingot and place it in the suction casting crucible of a vacuum suction casting machine. Evacuate to make the vacuum degree of the furnace cavity reach 2×10 -3 -5×10 -3 Pa. High-purity argon gas is introduced into the furnace cavity until the pressure reaches 0.01 - 0.02 MPa. The alloy in the crucible is heated to a completely molten state by arc melting method. Then, open the suction casting valve, and the molten alloy liquid is injected into the water-cooled copper mold below through the small holes at the bottom of the crucible under the action of air pressure and quickly cooled to obtain polycrystalline metal rods with a diameter of 3 - 8 mm and a length of 50 - 80 mm.

[0021] The substantial features of the present invention are:

[0022] Although the materials in the current technology can achieve negative thermal expansion, the prerequisite is that their compositions must contain a large amount of C / N atoms. The ratio of C / N atoms in the typical composition to all other atoms in the chemical formula is usually 1:4. Therefore, the synthesis method can only be achieved by high-temperature solid-phase reaction of raw material powders, that is, the powders need to be annealed for a long time under vacuum conditions, and obtaining bulk materials also relies on subsequent sintering. The process is relatively complex, and the composition accuracy and uniformity of the obtained finished products are poor. And the high C / N content makes the material very brittle, so it is difficult to machine.

[0023] The present invention is a Mn-based alloy carbide material that can achieve the negative thermal expansion effect with only a very small amount of C doping. The ratio of C atoms to all other atoms in the chemical formula is 1:40 - 1:20, which is much lower than the ratio of 1:4 in the current technology. Therefore, this material can directly obtain bulk materials with negative thermal expansion effect through a simpler method of arc melting plus subsequent rapid quenching or suction casting. At the same time, the mechanical properties of the material are also improved due to the reduction of C content. The mechanism is that by adding some Fe and Cu elements in the composition and reducing the content of Mn element at the same time, the C content required to obtain the negative thermal expansion effect is significantly reduced; a rapid cooling step such as spin casting or suction casting is adopted during the preparation to inhibit the formation of possible second phases in the sample and obtain samples with the required crystal structure.

[0024] The beneficial effects of the present invention are:

[0025] The Mn provided by the present invention 50 Fe25-x Cu x Ga 25 C y An alloy and its preparation method not only have the characteristic that general negative thermal expansion materials shrink in size and volume with the increase of temperature in a certain temperature range, but also the content of C element required to achieve the negative thermal expansion effect is significantly reduced compared with the existing Mn-based alloy carbide negative thermal expansion materials. The ratio of C atoms to all other atoms in the chemical formula is 1:40 - 1:20, far lower than the ratio of 1:4 in the existing materials. This material can directly obtain bulk finished products through the steps of arc melting + subsequent melt spinning or annealing, without the need to first mix the raw material powders for long-term diffusion annealing and then sinter to obtain the bulk like the existing materials. Therefore, the preparation method of this material is more simple and direct, and is more conducive to controlling the accuracy and uniformity of the material composition.

[0026] By changing the composition of Fe, Cu, and C elements in the material, Mn 50 Fe 25-x Cu x Ga 25 C y The negative thermal expansion range can cover the common working temperature range of 300K - 385K for equipment, and its thermal expansion coefficient can be adjusted by changing the composition to meet the requirements of different occasions and uses. At the same time, this series of alloys has good plasticity and ductility, overcoming the brittleness problem of the previous Mn alloy nitride / carbide negative thermal expansion alloys. Finally, Mn 50 Fe 25-x Cu x Ga 25 C y alloys can directly obtain bulk materials such as strips or rods, without the need for a relatively complex long-term solid-state diffusion and sintering process, thus simplifying the material preparation process and being conducive to actual production and application. Brief Description of the Drawings

[0027] Figure 1 are the X-ray diffraction spectra of the Mn 50 Fe 17 Cu8Ga 25 C 2.5 and Mn 50 Fe 17 Cu8Ga 25 C5 alloys in Examples 1 - 3;

[0028] Figure 2 are the X-ray diffraction spectra of the Mn 50 Fe 17 Cu8Ga 25 C 2.5 and Mn 50 Fe 17 Cu8Ga25 Thermal expansion measurement results of C5 alloy;

[0029] Figure 3 Mn in Examples 1-3 50 Fe 17 Cu8Ga 25 C 2.5 Tensile curve of the alloy;

[0030] Figure 4 Mn in Examples 1-3 50 Fe 17 Cu8Ga 25 C 2.5 SEM image of the alloy fracture morphology;

[0031] Figure 5 Mn in Example 4-5 50 Fe 15 Cu 10 Ga 25 C 3.5 X-ray diffraction spectrum of the alloy;

[0032] Figure 6 Mn in Example 4-5 50 Fe 15 Cu 10 Ga 25 C 3.5 Thermal expansion measurement results of the alloy. DETAILED DESCRIPTION

[0033] Example 1

[0034] Preparation composition is Mn 50 Fe 17 Cu8Ga 25 C 2.5 The polycrystalline alloy ribbon material is prepared by arc melting with a current of 55A and argon gas with a positive pressure of 0.03MPa as a protective gas in the furnace chamber. The alloy ingot is melted in a water-cooled copper crucible and then spun into a thin ribbon by a ribbon spinning machine at a speed of 20m / s. The preparation method is carried out according to the following specific steps:

[0035] (1) First, according to Mn 50 Fe 17 Cu8Ga 25 C 2.5 The atomic ratio in the chemical formula of is calculated and the required mass of pure Mn, pure Fe, pure Cu, pure Ga and C elements are weighed (the purity of the raw materials used is 99.9%). The weighed raw materials are placed in the crucible of the vacuum arc melting furnace. The furnace chamber is pre-evacuated to 5×10 -1 Pa; then use a molecular pump to evacuate to 3×10 -3Pa, and then introduce high-purity (purity 99.9%) argon gas to a predetermined pressure; after the electrode tip arcs, keep the tip at a position 1-3 cm above the alloy raw material and swing it repeatedly within a small range, (the melting current is 55 A) use the electric arc to melt and mix the raw materials, stop melting after melting for about 1 min, wait for the alloy ingot to solidify and then turn it over, repeat the previous melting steps; each alloy ingot is turned over three times during the entire melting process and melted four times to ensure the uniformity of the obtained alloy composition; the obtained alloy ingot is wrapped with tantalum sheets and then placed in a sealed vacuum quartz tube and annealed at 900 °C for 12 hours, and then cooled to room temperature to obtain an alloy ingot for preparing polycrystalline thin strips.

[0036] (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 cavity of the strip casting machine, evacuate to 5×10 -3 Pa, introduce high-purity argon gas into the furnace cavity, the pressure is -0.08 MPa, use induction heating to completely melt the alloy ingot, and then blow high-purity argon gas with a certain pressure from the upper part of the quartz tube to make the molten alloy liquid spray from the bottom hole onto a high-speed rotating copper wheel with a linear velocity of 20 m / s and be quickly ejected to obtain a polycrystalline metal thin strip with a width of 3-7 mm and a thickness of about 70 μm.

[0037] Example 2

[0038] Other steps are the same as in Example 1, the difference is that the target material is Mn 50 Fe 17 Cu8Ga 25 C4; the annealing time in step (1) is 24 hours;

[0039] Example 3

[0040] Other steps are the same as in Example 1, the difference is that the target material is Mn 50 Fe 17 Cu8Ga 25 C5; the linear velocity of the copper wheel in step (2) is 16 m / s;

[0041] Using the strip casting samples obtained in Examples 1-3, perform performance tests. Use an X-ray diffractometer to measure the crystal structure of the samples and find that the obtained samples all have the required face-centered cubic crystal structure. As an example, the X-ray diffraction spectra of the Mn 50 Fe 17 Cu8Ga 25 C 2.5 and Mn 50 Fe 17 Cu8Ga 25 C5 samples are at Figure 1Given that both are single phases with a face-centered cubic structure, it is proved that this method can synthesize materials with the required crystal structure. The relationship between the thermal expansion of the sample and temperature was measured using a strain gauge and a resistance strain gauge. Figure 2 gave Mn 50 Fe 17 Cu8Ga 25 C 2.5 and Mn 50 Fe 17 Cu8Ga 25 C5 ribbon samples. Based on the results, it can be seen that the sizes of both shrink with increasing temperature in the ranges of 363 - 385 K and 335 - 375 K respectively, and the thermal expansion coefficients in this range are -16.1×10 -6 / K and -15.3×10 -6 / K respectively, showing obvious negative thermal expansion; Figure 3 gave the tensile curves of the ribbon samples of Mn 50 Fe 17 Cu8Ga 25 C 2.5 tested using a universal material testing machine. It can be seen that there is an obvious plastic deformation process during the tensile process of the sample; Figure 4 gave the SEM photos of the fracture surface of the sample, in which there are obvious dimple structures, further proving that the material has good plasticity.

[0042] Example 4

[0043] Prepare a polycrystalline alloy suction casting rod with the composition of Mn 50 Fe 15 Cu 10 Ga 25 C 3.5 by the arc melting method. The current is 65 A, and argon gas with a positive pressure of 0.05 MPa in the furnace cavity is used as the protective gas. The alloy ingot is melted in a water-cooled copper crucible, and then the suction casting rod is prepared through a vacuum suction casting machine. The preparation method is carried out according to the following specific steps:

[0044] (1) First, calculate and weigh the required masses of the Mn, Fe, Cu, Ga, and C elements according to the atomic ratios of the chemical formula of Mn 50 Fe 15 Cu 10 Ga 25 C 3.5 (the purity of the raw materials used is 99.9%). Put the weighed raw materials into the crucible of the vacuum arc melting furnace. First, use a mechanical pump to pre-pump the vacuum of the furnace cavity to 5×10 -1 Pa; then use a molecular pump to pump the vacuum to 3×10 -3Pa, and then introduce high-purity argon gas (purity of 99.9%) to a predetermined pressure; after the electrode tip arcs, keep the tip at a position 1 - 3 cm above the alloy raw material and swing it repeatedly within a small range, melt and mix the raw material with the arc, the melting current is 65 A, continue melting for about 1 min after the material melts and then stop melting, turn the sample over after it solidifies, and repeat the previous melting steps; each alloy ingot is turned over three times during the whole melting process and melted four times in total to ensure the uniformity of the obtained alloy composition; the obtained alloy ingot is wrapped with tantalum sheets and placed in a sealed vacuum quartz tube for annealing at 800 °C for 12 hours, and then cooled to room temperature to obtain the alloy ingot for preparing the suction casting rod. (2) Clean the surface of the annealed alloy ingot, place it in the crucible in the furnace cavity of the vacuum suction casting machine, evacuate to 4×10 -3 Pa, introduce high-purity argon gas into the furnace cavity to 0.02 MPa, melt the alloy ingot to a liquid state by arc melting, then open the suction casting valve, suck the molten liquid metal through the small hole at the bottom of the crucible into the water-cooled copper mold below, and obtain a polycrystalline metal rod with a length of 50 - 70 mm and a diameter of about 7 mm after solidification;

[0045] Example 5

[0046] Other steps are the same as in Example 4, the difference is that the target material is Mn 50 Fe 11 Cu 14 Ga 25 C 3.5 ;

[0047] Using the rod samples obtained in Examples 4 - 5, perform performance tests. Measure the crystal structure of the samples using an X-ray diffractometer. As an example, Mn 50 Fe 15 Cu 10 Ga 25 C 3.5 The X-ray diffraction spectrum of the suction casting rod sample is shown in Figure 5 It can be seen that the sample forms a single-phase face-centered cubic structure, meeting the requirements for the crystal structure of the sample; measure the relationship between the thermal expansion of the material and temperature using a strain gauge and a resistance strain gauge. As an example, Mn 50 Fe 15 Cu 10 Ga 25 C 3.5 The test results of the suction casting rod are shown in Figure 6 It can be seen that the sample shows a negative thermal expansion effect in the range of 313 - 370 K, and the thermal expansion coefficient in this range is -31.2×10 -6 / K.

[0048] The above embodiments show that a negative thermal expansion material based on Mn-Fe-Cu-Ga alloy carbide and a preparation method thereof provided by the present invention can effectively synthesize strips or rods with an obvious negative thermal expansion effect. The preparation method is simple, the C doping amount can be accurately controlled, and by changing the proportion of each constituent element, the negative thermal expansion temperature range can be adjusted as needed, and it has good toughness, can adapt to different use conditions, and is conducive to promoting its industrial application.

[0049] Therefore, a negative thermal expansion material based on Mn-Fe-Cu-Ga alloy carbide and a preparation method thereof provided by the present invention can obtain a negative thermal expansion material covering the room temperature range, and can be used for the design and control of the thermal expansion performance of devices, and has important application values in many fields such as optical instruments, precision instruments, and advanced electronic devices.

[0050] Matters not described in the present invention are well-known technologies.

Claims

1. A Mn-Fe-Cu-Ga alloy carbide negative thermal expansion material, characterized in that, The chemical formula of the material is: Mn 50 Fe 25-x Cu x Ga 25 C y ; where 7.5 ≤ x ≤ 15, 2.5 ≤ y ≤ 5, and the subscript symbol of the element represents the atomic ratio of the element. The total number of atoms of Mn, Fe, Cu, and Ga is 100.

2. The Mn-Fe-Cu-Ga alloy carbide negative thermal expansion material according to claim 1, characterized in that, The morphology of the negative thermal expansion material is a polycrystalline thin strip material or a polycrystalline rod-shaped material.

3. The preparation method of the Mn-Fe-Cu-Ga alloy carbide negative thermal expansion material according to claim 1, characterized in that any one of the following two methods: Method 1, preparation of polycrystalline thin strip material, including the following steps: (1) According to the chemical formula Mn 50 Fe 25-x Cu x Ga 25 C y Weigh the required mass of each component raw material, put pure Mn, pure Fe, pure Cu, pure Ga and carbon into the crucible of vacuum arc melting furnace, and perform arc melting under argon atmosphere protection to obtain Mn 50 Fe 25- x Cu x Ga 25 C y Alloy ingot; the obtained alloy ingot is wrapped with a tantalum sheet and placed in a sealed vacuum quartz tube, annealed at 800-900°C for 12-24 hours, and then cooled to room temperature to obtain an alloy ingot for preparing a polycrystalline thin ribbon; Among them, The melting conditions adopted are as follows: when the vacuum degree in the melting chamber reaches 2×10 -3 -5×10 -3 Pa, argon gas is introduced into it until the pressure reaches 0.02 - 0.06 MPa; the melting current is 50 - 70 A, and each alloy ingot is flipped 2 - 4 times during the whole melting process; (2) Clean the surface of the annealed alloy ingot, place it in a quartz tube with an opening at the bottom, fix it in the chamber of the melt spinning machine, evacuate the chamber to a vacuum of 2×10 -3 -5×10 -3 Pa, introduce high-purity argon gas into the chamber with a pressure of -0.1 to -0.05 MPa, use induction heating or resistance heating to keep the alloy in a molten state, and then blow high-purity argon gas from the upper part of the quartz tube to make the molten alloy liquid spray out from the small holes at the bottom onto a rotating copper wheel with a linear velocity of 15 - 20 m / s and be rapidly spun out to obtain a polycrystalline metal thin strip material; Or, Method 2, preparation of polycrystalline suction casting material, including the following steps: (1) First, according to the chemical formula Mn 50 Fe 25-x Cu x Ga 25 C y weigh each required raw material component, put the weighed raw materials into the crucible of an arc melting furnace, and obtain a Mn 50 Fe 25-x Cu x Ga 25 C y alloy ingot; Among them, the melting conditions adopted are as follows: when the vacuum in the melting chamber reaches 2×10 -3 -5×10 -3 Pa, argon gas is introduced into it until the pressure reaches 0.02 - 0.06 MPa. During the whole melting process, the sample is protected by argon gas. The melting current is 50 - 70 A, and each alloy ingot is flipped 2 - 4 times during the whole melting process; the obtained alloy ingot is wrapped with tantalum sheets and then 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 the alloy ingot for preparing the suction casting rod; (2) Clean the surface of the annealed polycrystalline alloy ingot, place it in the suction casting crucible of a vacuum suction casting machine, evacuate to make the vacuum degree of the furnace cavity reach 2×10 -3 -5×10 -3 Pa, introduce high-purity argon gas into the furnace cavity until the pressure is 0.01 - 0.02 MPa, heat the alloy in the crucible to a completely molten state by the arc melting method, then open the suction casting valve, and make the molten alloy liquid be injected into the water-cooled copper mold below through the small holes at the bottom of the crucible under the action of air pressure and rapidly cooled to obtain polycrystalline metal bars.

4. The preparation method of the Mn-Fe-Cu-Ga alloy carbide negative thermal expansion material according to claim 3, characterized in that, The purities of pure Mn, pure Fe, pure Cu, pure Ga and pure C are all 99.9%; the purity of the high-purity argon gas is 99.9%.

5. The preparation method of the Mn-Fe-Cu-Ga alloy carbide negative thermal expansion material according to claim 3, characterized in that, In Method 1, the width of the polycrystalline metal thin strip material is 3-7 mm, and the thickness is 50-90 μm; in Method 2, the diameter of the polycrystalline metal rod is 3-8 mm, and the length is 50-80 mm.

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