CuSnTi / Nb composite material for Ni3Sn superconducting wire and preparation method and application of CuSnTi / Nb composite material

Abstract

The invention belongs to the technical field of superconducting wires, and particularly relates to a CuSnTi / Nb composite material for a Ni3Sn superconducting wire and a preparation method and application of the CuSnTi / Nb composite material. The preparation method comprises the steps that molten CuSnTi alloy liquid is cast into a mold where a niobium rod is fixed for heat preservation, then directional solidification is conducted, an obtained CuSnTi / Nb composite blank is subjected to heat treatment, and the CuSnTi / Nb composite material is obtained. The directional solidification technology is adopted for preparing the CuSnTi / Nb composite blank, the temperature gradient and the cooling rate in the solidification process are accurately controlled, tin element segregation can be effectively restrained, generation of brittle phases is reduced, the structure uniformity is improved, and a directional solidification structure is obtained, so that the plasticity of the alloy in the axial direction is improved, the ductility of the CuSnTi / Nb composite material is greatly improved, and the service life of the CuSnTi / Nb composite material is prolonged. The problem that in the process of preparing the Nb3Sn superconducting wire through a bronze method, the CuSnTi alloy is quick in work hardening and insufficient in plasticity, and consequently the core of the superconducting wire is broken is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of superconducting wires, and particularly relates to a CuSnTi / Nb composite material for Nb3Sn superconducting wires, a preparation method thereof, and an application thereof. Background Art

[0002] Niobium tin (Nb3Sn) is an intermetallic compound with an A15 crystal structure and belongs to the second type of superconducting material. The superconducting transition temperature ( Tc ) of niobium tin is 18.3K, and its upper critical magnetic field can reach 22.5T at 4.2K. Due to its high critical magnetic field characteristics and excellent mechanical properties, niobium tin is the main material for manufacturing superconducting magnets above 10T and is widely used in high magnetic field strength demand fields such as particle accelerators, nuclear magnetic resonance imaging (MRI) devices, and nuclear fusion devices.

[0003] Niobium tin is brittle and difficult to be directly processed into superconducting wires. It is usually prepared by the method of forming first and then diffusing to form a phase. The typical steps for preparing niobium tin superconducting wires by the bronze method are as follows: punching a tin bronze ingot, then placing a pure niobium rod in the hole of the tin bronze, and obtaining a multi-core niobium / tin bronze composite wire through hot extrusion and multi-pass drawing deformation. After phase-forming heat treatment, the tin element in the tin bronze diffuses into the niobium core to generate a niobium tin superconducting phase, and a niobium tin superconducting wire is obtained. Related technologies have disclosed a preparation method for bronze method niobium tin superconducting wires, including: obtaining an assembled structure by primary assembly, the assembled structure including: a drilled bronze ingot having a plurality of drilled holes filled with Nb rods, and the drilled bronze ingot is successively installed in a barrier layer and a stabilizing matrix; and obtaining the niobium tin superconducting wire after extruding, multi-pass drawing, and annealing the assembled structure. However, the existing bronze method for preparing niobium tin superconducting wires relies on a copper-tin alloy (Cu-Sn) with a high tin content as the matrix material. The higher the tin content, the higher the content of niobium tin generated during the phase-forming heat treatment process, and the better the performance of the superconducting wire. However, the solubility of tin in copper is limited, approaching 0 wt.% at room temperature, resulting in the easy generation of a large amount of brittle tin-rich phases during the preparation of tin bronze with a high tin content (Sn≥10.0 wt.%) by traditional casting, serious composition segregation, resulting in significant work hardening characteristics and insufficient plasticity of the tin bronze during cold processing; problems such as broken cores and broken wires are extremely likely to occur during the multi-pass drawing process for preparing superconducting wires, restricting the preparation of ten-thousand-meter high-performance niobium tin superconducting wires. Therefore, the contradiction between the tin content in tin bronze and the plasticity of the alloy has become a key problem in the preparation of niobium tin superconducting wires by the bronze method. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a CuSnTi / Nb composite material for Nb₃Sn superconducting wire, a preparation method thereof and an application thereof. The preparation method of the present invention can obtain a CuSnTi / Nb composite material for Nb₃Sn superconducting wire with good plasticity, which can realize multi-pass continuous drawing deformation, and the tin content can reach 16 wt.%.

[0005] The present invention provides a preparation method of a CuSnTi / Nb composite material for Nb₃Sn superconducting wire, comprising the following steps: Pouring molten CuSnTi alloy liquid into a mold fixed with a niobium rod for heat preservation, and performing directional solidification to obtain a CuSnTi / Nb composite blank; the drawing rate of the blank during the directional solidification process is 10-100 µm / s; Performing heat treatment on the CuSnTi / Nb composite blank to obtain a CuSnTi / Nb composite material for Nb₃Sn superconducting wire.

[0006] Preferably, the drawing rate of the blank during the directional solidification process is 40-60 µm / s.

[0007] Preferably, the molten CuSnTi alloy liquid is obtained by vacuum induction melting using copper blocks, tin particles and titanium particles as raw materials; the temperature of the vacuum induction melting is 1100-1200 °C, and the heat preservation time is 10-20 min.

[0008] Preferably, the molten CuSnTi alloy liquid comprises the following elements in mass percentages: copper 83.7%-91.7%, tin 8%-16% and titanium 0.3%.

[0009] Preferably, the molten CuSnTi alloy liquid comprises the following elements in mass percentages: copper 87.7%, tin 12% and titanium 0.3%.

[0010] Preferably, the mold fixed with the niobium rod comprises a chassis for fixing the niobium rod, the diameter of the chassis is 20-25 mm; 1-7 niobium rods are positioned and fixed on the chassis for fixing the niobium rod, and the diameter of the niobium rod is 4-7 mm.

[0011] Preferably, before the casting, it further includes: preheating the mold fixed with the niobium rod in a heat preservation area, the temperature of the heat preservation area is 1250-1270 °C, and the preheating time is 10-20 min.

[0012] Preferably, the temperature of the heat treatment is 600-700 °C, and the heat preservation time is 24-72 h.

[0013] The present invention also provides a CuSnTi / Nb composite material for Nb₃Sn superconducting wire obtained by the preparation method described in the above technical solution.

[0014] The present invention also provides the application of the CuSnTi / Nb composite material for niobium-tin superconducting wire in the field of low-temperature superconductivity described in the above technical solution.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention prepares the CuSnTi / Nb composite billet by using the directional solidification technology. By precisely controlling the drawing rate of the billet during the directional solidification process, the temperature gradient and cooling rate during the directional solidification process can be precisely controlled, which can effectively reduce the composition segregation and the generation of brittle phases. At the same time, the directional solidification process enables the grains to preferentially grow along a specific direction, forming a composite material with a directional grain structure, significantly improving the tensile strength and elongation of the composite material along the axial direction, and solving the problems of work hardening and insufficient plasticity easily occurring in the preparation of Nb3Sn superconducting wire by the existing bronze method, resulting in broken cores and broken wires of the superconducting wire.

[0016] The present invention directly prepares the CuSnTi / Nb composite material by compounding the CuSnTi alloy liquid and the pure niobium (Nb) rod, adopting a new processing method of "liquid-solid" coupling, which can reduce the problems of low material utilization rate, long processing flow, and high process control difficulty caused by drilling holes in the CuSnTi alloy and inserting niobium rods during the processing of the traditional bronze method.

[0017] Furthermore, the present invention ensures that the preparation process of the CuSnTi / Nb composite material for niobium-tin superconducting wire has higher reliability and repeatability by precisely controlling the key parameters such as the temperature gradient and cooling rate during the directional solidification process, the preheating temperature of the mold, and the preparation temperature of the molten CuSnTi alloy liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0019] Figure 1 It is a schematic diagram of the chassis of the drawing mold for directional solidification in Example 1; Figure 2 It is a photo of the CuSnTi / Nb composite material for niobium-tin superconducting wire obtained in Example 1; Figure 3 It is a cross-sectional photo of the CuSnTi / Nb composite material for niobium-tin superconducting wire obtained in Example 1; Figure 4 It is the room-temperature tensile test result of the CuSnTi / Nb composite material for niobium-tin superconducting wire obtained in Example 1; Figure 5 It is a microstructural photograph of the CuSnTi / Nb composite material for niobium-tin superconducting wire obtained in Example 1; Figure 6 It is a schematic diagram of the chassis of the drawing die for directional solidification in Example 2; Figure 7 It is a photograph of the CuSnTi / Nb composite material for niobium-tin superconducting wire obtained in Example 2; Figure 8 It is a cross-sectional photograph of the CuSnTi / Nb composite material for niobium-tin superconducting wire obtained in Example 2; Figure 9 It is the room-temperature tensile test result of the CuSnTi / Nb composite material for niobium-tin superconducting wire obtained in Example 2; Figure 10 It is a microstructural photograph of the CuSnTi / Nb composite material for niobium-tin superconducting wire obtained in Example 2; Figure 11 It is a schematic diagram of the chassis of the drawing die for directional solidification in Example 3; Figure 12 It is a photograph of the CuSnTi / Nb composite material for niobium-tin superconducting wire obtained in Example 3; Figure 13 It is a cross-sectional photograph of the CuSnTi / Nb composite material for niobium-tin superconducting wire obtained in Example 3; Figure 14 It is the room-temperature tensile test result of the CuSnTi / Nb composite material for niobium-tin superconducting wire obtained in Example 3; Figure 15 It is a microstructural photograph of the CuSnTi / Nb composite material for niobium-tin superconducting wire obtained in Example 3; Figure 16 It is a microstructural diagram of the copper-tin-titanium alloy ingot in Comparative Example 1. Specific embodiments

[0020] The present invention provides a preparation method of a CuSnTi / Nb composite material for niobium-tin superconducting wire, comprising the following steps: Pour the molten CuSnTi alloy liquid into a mold fixed with a niobium rod and keep it warm, and perform directional solidification to obtain a CuSnTi / Nb composite blank; the drawing rate of the blank during the directional solidification process is 10-100 µm / s; Heat-treat the CuSnTi / Nb composite blank to obtain a CuSnTi / Nb composite material for niobium-tin superconducting wire.

[0021] In the present invention, unless otherwise specified, the materials and equipment used are all commercially available products in the art.

[0022] In the present invention, the molten CuSnTi alloy liquid is cast into a mold fixed with niobium rods and kept warm, and directionally solidified to obtain a CuSnTi / Nb composite blank; during the directional solidification process, the pulling rate of the blank is 10~100 µm / s.

[0023] In the present invention, the molten CuSnTi alloy liquid preferably comprises the following elements by mass percentage: copper (Cu) 83.7%~91.7%, tin (Sn) 8%~16% and titanium (Ti) 0.3%; specifically, it may include: 91.7% copper, 8% tin and 0.3% titanium, or include: 87.7% copper, 12% tin and 0.3% titanium, or include: 83.7% copper, 16% tin and 0.3% titanium.

[0024] In the present invention, the molten CuSnTi alloy liquid is preferably obtained by vacuum induction melting using copper blocks, tin particles and titanium particles as raw materials; the vacuum degree of the vacuum induction melting is preferably 3×10 -3 ~3×10 -4 Pa; the temperature of the vacuum induction melting is preferably 1100~1200 °C, specifically it may be 1100 °C, 1150 °C or 1200 °C, and the holding time is preferably 10~20 min, specifically it may be 10 min, 15 min or 20 min; the heating rate from room temperature to the temperature of the vacuum induction melting is preferably 5~10 °C / min, specifically it may be 5 °C / min, 7 °C / min or 10 °C / min.

[0025] In the present invention, the mold is a pulling mold for directional solidification; the mold fixed with niobium rods includes a chassis for fixing the niobium rods, and the diameter of the chassis is preferably 20~25 mm, specifically it may be 22 mm; the chassis for fixing the niobium rods is preferably positioned and fixed with 1~7 niobium (Nb) rods, specifically it may be 1 rod, 3 rods or 7 rods, and the diameter of the niobium rods is preferably 4~7 mm, specifically it may be 4 mm, 5 mm or 7 mm; the niobium rods are vertically fixed to the chassis through the drilled holes on the chassis. The surface of the niobium rods is preferably cleaned with deionized water before use.

[0026] In the present invention, before the casting, it preferably further includes: placing the mold fixed with niobium rods in a heat preservation zone for preheating, the temperature of the heat preservation zone is 1250~1270 °C, and the preheating time is 10~20 min. By preheating the mold in the present invention, it can ensure that the molten CuSnTi alloy liquid maintains good fluidity during the casting process, avoid premature solidification of the alloy liquid, and reduce the thermal stress caused by the temperature gradient.

[0027] In the present invention, after the casting, the molten CuSnTi alloy liquid fills the gaps between the niobium rods.

[0028] In the present invention, the temperature for heat preservation is preferably 1250 - 1270 °C, and the time is preferably 10 - 20 min.

[0029] In the present invention, the directional solidification is as follows: a unidirectional cooling technique is adopted to draw the green body from one end of the mold, and water cooling is applied at the drawing end of the mold during the drawing process; the drawing end is the bottom of the chassis for fixing the niobium rod; the water cooling is circulating water cooling, and the present invention has no special requirements for the flow rate of the circulating water. The drawing rate of the green body during the directional solidification process is 10 - 100 µm / s, preferably 40 - 60 µm / s, and specifically can be 10 µm / s, 50 µm / s or 100 µm / s. The present invention adopts unidirectional temperature gradient cooling, and the grains preferentially grow along a specific direction, thereby obtaining a CuSnTi alloy with a directional grain structure. Directional solidification is a process that enables the alloy melt to solidify along the direction opposite to the heat flow according to the required crystallization orientation by establishing a temperature gradient in a specific direction during the solidification process; it can eliminate the transverse grain boundaries, thereby significantly improving the unidirectional mechanical properties of the material. The present invention realizes the directional solidification of the CuSnTi alloy liquid by precisely controlling the cooling rate (drawing rate).

[0030] After obtaining the CuSnTi / Nb composite green body, the present invention performs heat treatment on the CuSnTi / Nb composite green body to obtain a CuSnTi / Nb composite material for niobium-tin superconducting wire.

[0031] In the present invention, the temperature for heat treatment is preferably 600 - 700 °C, specifically can be 650 °C, and the heat preservation time is preferably 24 - 72 h, specifically can be 24 h, 48 h or 72 h. During the heat treatment process, the microstructure morphology of the copper-tin-titanium alloy can be regulated, and the dissolution of the tin-rich phase can be promoted.

[0032] The present invention also provides a CuSnTi / Nb composite material for niobium-tin superconducting wire obtained by the preparation method described in the above technical solution.

[0033] The present invention also provides the application of the CuSnTi / Nb composite material for niobium-tin superconducting wire described in the above technical solution in the field of low-temperature superconductivity.

[0034] The present invention has no special requirements for the method of preparing a niobium-tin superconducting wire from the CuSnTi / Nb composite material, and the commonly used methods by those skilled in the art can be adopted.

[0035] In the present invention, the application in the field of high-temperature superconductivity preferably includes being used in particle accelerators, nuclear magnetic resonance imaging devices or nuclear fusion devices.

[0036] The present invention uses the directional solidification technology to prepare CuSnTi / Nb composites for niobium-tin superconducting wires, solving the problems of the contradiction between tin content and plasticity, work hardening, and brittle tin-rich phases in the traditional bronze method, and the preparation process is simple and the cost is low.

[0037] To further illustrate the present invention, the CuSnTi / Nb composites for niobium-tin superconducting wires provided by the present invention, their preparation methods and applications will be described in detail below with reference to the accompanying drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0038] Example 1 A method for preparing CuSnTi / Nb composites for niobium-tin superconducting wires, comprising the following steps: Step 1. CuSnTi alloy batching: Weigh 91.7% of copper blocks, 8% of tin particles and 0.3% of Ti particles according to the following mass percentages.

[0039] Step 2. Vacuum induction melting of CuSnTi alloy batching: Set the vacuum degree of the induction melting furnace at 3×10 -3 Pa, use induction melting heating, heat at a heating rate of 5 °C / min to 1100 °C, and after the temperature reaches 1100 °C, keep it warm for 10 min to obtain molten CuSnTi alloy liquid.

[0040] Step 3. Design and processing of the drawing die for directional solidification: The diameter of the bottom plate of the drawing die is 22 mm, and holes are drilled on the bottom plate according to the preset positions for positioning 7 pure niobium (Nb) rods with a diameter of 4 mm. The surface of the pure niobium rods is cleaned with deionized water.

[0041] Step 4. Assembly of the drawing die and pure niobium rods: Integrate the drilled bottom plate with the Nb rods to ensure precise fit and stable connection. The length of the Nb rods exposed from the bottom plate is 15 mm.

[0042] Step 5. Preheat treatment of the drawing die and pure niobium rods: Place the die with the niobium rods fixed in the insulation area and preheat it to 1250 °C, and keep it warm for 10 min.

[0043] Step 6. Pour the molten CuSnTi alloy liquid into the gaps between the pure niobium rods: Pour the molten CuSnTi alloy liquid into the die preheated in the insulation area, and the alloy liquid fills the gaps between the pure niobium rods, and keep it warm for 10 min.

[0044] Step 7. Directional solidification of the CuSnTi alloy liquid / pure niobium rods: Adopt the unidirectional cooling technology, gradually draw at a speed of 100 µm / s from one end of the die, and apply water cooling during the drawing process to obtain a CuSnTi / Nb composite blank.

[0045] Step 8. Heat treatment: The CuSnTi / Nb composite blank obtained by directional solidification is heated at 650 °C for 24 h, and then water-cooled to obtain the CuSnTi / Nb composite material for Nb₃Sn superconducting wire.

[0046] The schematic diagram of the chassis of the drawing die for directional solidification in Example 1 is as Figure 1 shown.

[0047] The CuSnTi / Nb composite material for Nb₃Sn superconducting wire obtained in Example 1 is as Figure 2 shown, and the cross-section of the CuSnTi / Nb composite material for Nb₃Sn superconducting wire obtained in Example 1 is as Figure 3 shown.

[0048] A room-temperature tensile experiment was carried out on the CuSnTi / Nb composite material sample for Nb₃Sn superconducting wire obtained after heat treatment in Example 1, and the set rate was 0.5 mm / s. The results are as Figure 4 shown, where the abscissa is the tensile strength (unit: MPa) and the ordinate is the elongation. The measured tensile strength is 345 MPa and the elongation is 57%.

[0049] Figure 5 is the microstructural photo of the CuSnTi / Nb composite material for Nb₃Sn superconducting wire obtained in Example 1. It can be seen that the microstructure is mainly composed of α-Cu and a very small amount of δ-Cu₄₁Sn₁₁ phase. The tin-rich phase has a small content and small size, indicating that the directional solidification technology can greatly improve the solid solubility of Sn in Cu, reduce element segregation, and is beneficial to improving the plasticity of the alloy.

[0050] Example 2 A preparation method of a CuSnTi / Nb composite material for Nb₃Sn superconducting wire includes the following steps: Step 1. CuSnTi alloy batching: Weigh 87.7% of copper blocks, 12% of tin particles, and 0.3% of Ti particles according to the following mass percentages.

[0051] Step 2. Vacuum induction melting of CuSnTi alloy batching: Set the vacuum degree range of induction melting at 3×10 - 3 Pa, and use induction melting for heating. Heat at a heating rate of 7 °C / min to 1150 °C. After the temperature reaches 1150 °C, hold for 15 min to obtain the molten CuSnTi alloy liquid.

[0052] Step 3. Design and processing of the drawing die for directional solidification: The diameter of the chassis of the drawing die is 22 mm, and holes are drilled on the chassis according to the preset positions for positioning 3 pure niobium (Nb) rods with a diameter of 5 mm. The surfaces of the pure niobium rods are cleaned with deionized water.

[0053] Step 4. Assembly of the drawing die and the pure niobium rod: Integrate the drilled chassis with the Nb rod systemically to ensure precise fit and stable connection.

[0054] Step 5. Preheat treatment of the drawing die and the pure niobium rod: Place the die with the niobium rod fixed in the heat preservation zone and preheat it to 1260 °C, then keep it warm for 15 min.

[0055] Step 6. Pour the molten CuSnTi alloy liquid into the gaps between the pure niobium rods: Pour the molten CuSnTi alloy liquid into the die preheated in the heat preservation zone. The alloy liquid fills the gaps between the pure niobium rods and keep it warm for 10 min.

[0056] Step 7. Directional solidification of the CuSnTi alloy liquid / pure niobium rod: Adopt the unidirectional cooling technology, gradually draw from one end of the die at a speed of 50 µm / s, and apply water cooling during the drawing process to obtain the CuSnTi / Nb composite billet.

[0057] Step 8. Heat treatment: Heat the CuSnTi / Nb composite billet obtained by directional solidification at 650 °C for 48 h, and then carry out water cooling to obtain the CuSnTi / Nb composite material for niobium trisulfide superconducting wire.

[0058] The schematic diagram of the chassis of the drawing die for directional solidification in Example 2 is as Figure 6 shown.

[0059] The CuSnTi / Nb composite material for niobium trisulfide superconducting wire obtained in Example 2 is as Figure 7 shown, and the cross-section of the CuSnTi / Nb composite material for niobium trisulfide superconducting wire obtained in Example 2 is as Figure 8 shown.

[0060] Carry out a room temperature tensile test on the CuSnTi / Nb composite material sample for niobium trisulfide superconducting wire obtained after heat treatment in Example 2, set the rate to 0.5 mm / s, and the results are as Figure 9 shown, where the abscissa is the tensile strength (unit: MPa) and the ordinate is the elongation. The measured tensile strength is 410.5 MPa and the elongation is 62%.

[0061] Figure 10 is the microstructural photo of the CuSnTi / Nb composite material for niobium trisulfide superconducting wire obtained in Example 2. The microstructure is mainly composed of α-Cu and a very small amount of δ-Cu41Sn11 phase. The tin-rich phase has a small content and small size, indicating that the directional solidification technology can improve the segregation of Sn element and is beneficial to improving the plasticity of the alloy.

[0062] Example 3 A preparation method of a CuSnTi / Nb composite material for niobium trisulfide superconducting wire, comprising the following steps: Step 1. CuSnTi alloy batching: Weigh 83.7% of copper blocks, 16% of tin particles, and 0.3% of Ti particles according to the following mass percentages.

[0063] Step 2. Vacuum induction melting of CuSnTi alloy batching: Set the vacuum range of induction melting at 3×10 - 4 Pa, use induction melting for heating, heat at a heating rate of 10 °C / min to 1200 °C, and after the temperature reaches 1200 °C, hold for 20 min to obtain molten CuSnTi alloy liquid.

[0064] Step 3. Design and processing of the drawing die for directional solidification: The diameter of the bottom plate of the drawing die is 22 mm. Drill holes on the bottom plate according to the preset positions for positioning 1 pure niobium (Nb) rod with a diameter of 7 mm. The surface of the pure niobium rod is cleaned with deionized water.

[0065] Step 4. Assembly of the drawing die and the pure niobium rod: Integrate the drilled bottom plate with the Nb rod to ensure precise fit and stable connection.

[0066] Step 5. Preheat treatment of the drawing die and the pure niobium rod: Place the die with the niobium rod fixed in the heat preservation zone and preheat it to 1270 °C, and hold for 20 min.

[0067] Step 6. Pour the molten CuSnTi alloy liquid into the gap between the pure niobium rods: Pour the molten CuSnTi alloy liquid into the die preheated in the heat preservation zone, and the alloy liquid fills the gap between the pure niobium rods, and hold for 10 min.

[0068] Step 7. Directional solidification of the CuSnTi alloy liquid / pure niobium rod: Adopt the unidirectional cooling technology, gradually draw at a speed of 10 µm / s from one end of the die, and apply water cooling during the drawing process to obtain the CuSnTi / Nb composite blank.

[0069] Step 8. Heat treatment: Heat the CuSnTi / Nb composite blank obtained by directional solidification at 650 °C for 72 h, and then carry out water cooling to obtain the CuSnTi / Nb composite material for niobium trisulfide superconducting wire.

[0070] The schematic diagram of the bottom plate of the drawing die for directional solidification in Example 3 is as Figure 11 shown.

[0071] The CuSnTi / Nb composite material for niobium trisulfide superconducting wire obtained in Example 3 is as Figure 12 described, and the cross-section of the CuSnTi / Nb composite material for niobium trisulfide superconducting wire obtained in Example 3 is as Figure 13 shown.

[0072] A room-temperature tensile experiment was conducted on the CuSnTi / Nb composite material sample for the Nb₃Sn superconducting wire obtained after heat treatment in Example 3, with a set rate of 0.5 mm / s. The results are as Figure 14 shown, where the abscissa is the tensile strength (unit: MPa) and the ordinate is the elongation. The measured tensile strength is 400 MPa and the elongation is 46%.

[0073] Figure 15 Figure is a microstructural photograph of the CuSnTi / Nb composite material for the Nb₃Sn superconducting wire obtained in Example 3. The microstructure mainly consists of α-Cu and a very small amount of tin-rich phase, and the content of the tin-rich phase is small and the size is small, indicating that the directional solidification technology can greatly reduce the segregation of Sn elements in the CuSnTi alloy and improve the plasticity of the alloy.

[0074] Comparative Example 1 A copper-tin-titanium alloy was prepared by a traditional casting method: 83.7% of copper blocks, 16% of tin particles, and 0.3% of Ti particles were weighed according to the following mass percentages. The raw materials were added to a vacuum induction melting furnace, and the vacuum was pumped to 3×10 -4 Pa, the melting temperature was set at 1250 °C, the melting time was 0.5 h, and an ingot was prepared by the tilting casting method. The cooling method of the ingot was water-cooled copper mold cooling.

[0075] The microstructure of the copper-tin-titanium alloy ingot is as Figure 16 shown. The results show that there are coarse aggregations of tin-rich phases in the microstructure, serious segregation of Sn elements occurs during the traditional solidification process, the content of the tin-rich phase is high, which is not conducive to the improvement of the plasticity of the alloy. After room-temperature tensile testing (the testing method is the same as that in the example), its tensile strength is 340 MPa and the elongation is only 6.7%.

[0076] Comparative Example 2 A copper-tin-titanium alloy was prepared by a traditional casting method: 83.7% of copper blocks, 16% of tin particles, and 0.3% of Ti particles were weighed according to the following mass percentages. The raw materials were added to a vacuum induction melting furnace, and the vacuum was pumped to 3×10 -4 Pa, the melting temperature was set at 1250 °C, the melting time was 0.5 h, and an ingot was prepared by the tilting casting method. The cooling method of the ingot was water-cooled copper mold cooling.

[0077] The obtained copper-tin-titanium alloy ingot was heat-treated at 650 °C for 24 h, and the mechanical properties of the alloy were measured. The results show that after room-temperature tensile testing (the testing method is the same as that in the example), its elongation is 45%.

[0078] From the data of Examples 1-3 and Comparative Examples 1-2, it can be seen that for the CuSnTi / Nb composite material prepared by the method of the present invention, its elongation is between 46% and 62%, while for the CuSnTi / Nb composite material prepared by the traditional casting method, its elongation is only between 6.7% and 45%. The composite material prepared by the present invention has a higher elongation and can meet the performance requirements for the preparation of niobium-tin superconducting wires.

[0079] The present invention composites the CuSnTi alloy liquid with a pure niobium (Nb) rod for directional solidification. By establishing a stable temperature gradient and precisely controlling the solidification rate, it can effectively reduce component segregation and obtain a fine and uniform dendritic structure; it can also improve the plasticity of the alloy and reduce the generation of brittle phases, thereby improving the processing performance of the material. In addition, the directional solidification process can also effectively reduce the generation of thermal stress and improve the reliability and service life of the material. The CuSnTi / Nb composite material for niobium-tin superconducting wires of the present invention can meet the stringent requirements for material performance in high-end engineering fields and provides strong support for the development of related industries.

[0080] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments according to the embodiments of the present invention without creative labor, and these embodiments all belong to the protection scope of the present invention.

Claims

1. A preparation method of a CuSnTi / Nb composite material for a niobium-tin superconducting wire, characterized in that, It includes the following steps: Pour the molten CuSnTi alloy liquid into a mold fixed with a niobium rod and keep it warm, and carry out directional solidification to obtain a CuSnTi / Nb composite blank; during the directional solidification process, the drawing rate of the blank is 10~100 µm / s; Heat-treat the CuSnTi / Nb composite blank to obtain a CuSnTi / Nb composite material for niobium-tin superconducting wire.

2. The preparation method according to claim 1, wherein During the directional solidification process, the drawing rate of the blank is 40~60 µm / s.

3. The preparation method according to claim 1, characterized in that, The molten CuSnTi alloy liquid is obtained by vacuum induction melting using copper blocks, tin particles and titanium particles as raw materials; the temperature of the vacuum induction melting is 1100~1200 °C, and the holding time is 10~20 min.

4. The preparation method according to claim 1 or 3, characterized in that, The molten CuSnTi alloy liquid contains the following elements by mass percentage: 83.7%~91.7% of copper, 8%~16% of tin and 0.3% of titanium.

5. The preparation method according to claim 4, characterized in that, The molten CuSnTi alloy liquid contains the following elements by mass percentage: 87.7% of copper, 12% of tin and 0.3% of titanium.

6. The preparation method according to claim 1, wherein, The mold fixed with the niobium rod includes a chassis for fixing the niobium rod, and the diameter of the chassis is 20~25 mm; 1~7 niobium rods are positioned and fixed on the chassis for fixing the niobium rod, and the diameter of the niobium rod is 4~7 mm.

7. The preparation method according to claim 1, wherein Before the casting, it also includes: placing the mold fixed with the niobium rod in a heat preservation area for preheating, the temperature of the heat preservation area is 1250~1270 °C, and the preheating time is 10~20 min.

8. The preparation method according to claim 1, characterized in that, The temperature of the heat treatment is 600~700 °C, and the holding time is 24~72 h.

9. The CuSnTi / Nb composite material for niobium-tin superconducting wire obtained by the preparation method according to any one of claims 1~8.

10. The application of the CuSnTi / Nb composite material for niobium-tin superconducting wire according to claim 9 in the field of low-temperature superconductivity.

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