Medium-high-entropy alloy superconducting joint of superconducting cable and preparation method and application of medium-high-entropy alloy superconducting joint

Abstract

The invention discloses a medium-high-entropy alloy superconducting joint of a superconducting cable and a preparation method and application of the medium-high-entropy alloy superconducting joint. The medium-high-entropy alloy superconducting joint is prepared from medium-entropy alloys of 3-4 metal elements or high-entropy alloys of 5 or more metal elements. The medium-high-entropy alloy is used as a core material to be introduced into the superconducting joint structure, and the joint performance is directly improved through the unique material characteristics of the medium-high-entropy alloy.

Description

Technical Field

[0001] This invention relates to the field of superconducting materials technology, and in particular to a medium-high entropy alloy superconducting connector for superconducting cables, its preparation method, and its application. Background Technology

[0002] Superconducting cables offer significant advantages in power transmission, including low loss and high capacity. In practical applications, long-distance superconducting cables require intermediate joints to connect multiple cable segments. The performance of these joints directly determines the efficiency and reliability of the entire cable system. An ideal superconducting joint should possess low resistance, high mechanical strength, and long-term operational stability similar to the superconducting tape itself.

[0003] Currently, superconducting cable joints typically use conventional metals (such as tin, indium, lead, and their alloys) as solders to connect superconducting tapes via welding or crimping. However, these traditional materials have the following inherent drawbacks: 1. Traditional superconducting joints often use solders such as Pb-Bi alloys and Wood's metals, which contain lead and cadmium, and are harmful to the environment.

[0004] 2. Conventional metals are not superconductors, and additional resistance is introduced at the junction, resulting in energy loss and localized heating.

[0005] 3. Soft metals such as tin and indium have low strength and are prone to creep or deformation under thermal cycling and electromagnetic forces, which leads to a decrease in contact pressure, an increase in joint resistance, or even failure.

[0006] 4. Traditional superconducting joints generally have a low critical magnetic field. In most cases, the joint part needs to be placed in a low magnetic field area at a certain distance from the ferromagnetic coil or additional electromagnetic shielding is required.

[0007] Therefore, developing a novel superconducting connector that combines low resistance, high strength, and high stability has become a key technical problem that urgently needs to be solved in this field.

[0008] The medium-high entropy alloys of this invention are novel materials composed of multiple (usually 3-5 or more) main elements mixed in near-equal proportions. This breaks away from the traditional alloy model that uses one or two metallic elements as the main components and adds specific small amounts of other elements to achieve different properties. For example, transmission alloy steel is made by adding small amounts of carbon and trace amounts of manganese, silicon, etc. The core principle lies in utilizing high mixing entropy to stably form a simple solid solution structure, rather than a complex intermetallic compound. These materials exhibit significant advantages in mechanical, thermal, and chemical stability, such as high yield strength and ductility, high strength at high temperatures, strong corrosion resistance and oxidation resistance, and excellent thermal stability. Summary of the Invention

[0009] The purpose of this invention is to address the technical deficiencies in the existing technology by providing a medium-high entropy alloy superconducting connector for superconducting cables.

[0010] Another object of the present invention is to provide a method for preparing the medium-high entropy alloy superconducting joint of the above-mentioned superconducting cable.

[0011] Another object of the present invention is to provide the application of the medium-high entropy alloy superconducting joint of the above-mentioned superconducting cable.

[0012] The technical solution adopted to achieve the purpose of this invention is: A medium-high entropy alloy superconducting connector for a superconducting cable, wherein the medium-high entropy alloy superconducting connector is prepared by a medium-entropy alloy of 3-4 elements, or a high-entropy alloy of 5 or more elements, wherein the elements include Li, Be, B, C, N, Mg, Al, Zn, Nb, Co, Fe, Ni, Cu, Mn, Ti, V, Ta, Cr, V, Zr, Hf, Ta, Mo, W, Sc, or Sn.

[0013] In the above technical solution, the medium-entropy alloy is Hf. a Nb b Zr c Ti d Ta a Nb b Hf c Zr d or Nb a Sc b Hf c Zr d Ti a Nb b Ta c N d Fe a Ni b Co c Cr d Where 5≤a, b, c, d≤35, and a+b+c+d=100.

[0014] In the above technical solution, the high-entropy alloy is Hf. a Nb b Ti c V d Zr e (ScZrNb) 1-x [RhPd] x Ta a Nb b Hf c Zr d Ti e Hf a Ta bNb c Mo d W e or Nb a Re b Hf c Zr d Ti e , where 5≤a,b,c,d,e≤35, and a+b+c+d+e=100, 0.3≤x≤0.4.

[0015] In the above technical solution, the medium-high entropy alloy superconducting connector is in the form of a thin sheet or a block.

[0016] In the above technical solution, the sheet or block is grown by electric arc melting or laser levitation zone furnace.

[0017] Another aspect of the present invention includes a method for preparing the aforementioned medium-high entropy alloy superconducting joint, comprising the following steps: Under an argon atmosphere, 3-4 or more elements are mixed evenly, cold isostatically pressed into billets, sintered, and crystals are grown using a laser levitation zone furnace to obtain a medium-high entropy alloy superconducting joint.

[0018] In the above technical solution, the cold isostatic pressing is carried out at 160–200 MPa.

[0019] In the above technical solution, the crystal growth conditions are a growth rate of 3–6 mm / h, a rotation rate of 15–20 rpm, and a growth temperature of 1400°C–1500°C.

[0020] Another aspect of the present invention includes the application of the aforementioned medium-high entropy alloy superconducting joint in the connection of superconducting tapes, the series connection of superconducting magnets, or the formation of closed-loop operation of superconducting magnet coils.

[0021] In the above technical solution, the medium-high entropy alloy superconducting joint is placed between the ends of the two superconducting strips and connected through a metallurgical chemical reaction.

[0022] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention introduces medium-high entropy alloy as the core material into the superconducting joint structure, and directly improves the joint performance through its unique material properties.

[0023] 2. The high-entropy alloy of the present invention possesses superconductivity, thereby achieving a connection with near-zero resistance.

[0024] 3. The high strength and high hardness of the medium-high entropy alloy of the present invention enable the joint to withstand huge thermal stress and electromagnetic force, and its creep resistance is far superior to that of traditional soft solder joints, resulting in a significantly extended service life.

[0025] 4. The high-entropy alloy of this invention does not contain lead or cadmium, and is harmless to the environment. This invention achieves a balance between non-toxicity, environmental friendliness, and high performance. Attached Figure Description

[0026] Figure 1 HfNiZrTi alloy prepared by laser floating zone furnace method in Example 1.

[0027] Figure 2 The resistivity of the HfNbZrTi alloy in Example 1 varies with temperature under different applied magnetic fields.

[0028] Figure 3 (ScZrNb) is from Example 2. 0.65 [RhPd] 0.35 The resistivity of the alloy changes with temperature under different applied magnetic fields.

[0029] Figure 4 This is a schematic diagram comparing the structures of traditional alloys and high-entropy alloys, where a represents a traditional alloy and b represents a high-entropy alloy. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0031] Example 1 A method for preparing a medium-high entropy alloy superconducting joint for a superconducting cable includes the following steps: High-purity (99.9%) hafnium (Hf), niobium (Nb), zirconium (Zr), and titanium (Ti) metal powders were mixed in an argon atmosphere using a ball milling process. The mixture was then cold isostatically pressed into billets at 160–200 MPa. These billets were then sintered at 1100°C for 15 hours in a tube furnace under argon protection. Hf crystals were then grown in a laser-assisted levitation furnace at a growth rate of 3–6 mm / h, a rotation speed of 15–20 rpm, and a growth temperature of 1400°C–1500°C in a high-purity argon atmosphere. 25 Nb 25 Zr 25 Ti 25 The alloy, namely HfNbZrTi alloy, is used as a medium-to-high entropy alloy superconducting joint, such as... Figure 1 As shown.

[0032] like Figure 2 As shown, the resistivity of the HfNbZrTi alloy in this embodiment varies with temperature under different magnetic fields, ranging from 0 T to 9 T. Figure 2It can be seen that even under an external magnetic field of up to 9T, a zero-resistance transition can still occur.

[0033] Example 2 A method for preparing a medium-high entropy alloy superconducting joint for a superconducting cable includes the following steps: (ScZrNb) 0.65 [RhPd] 0.35 The alloy was prepared using arc melting technology: high-purity (99.9%) scandium blocks, zirconium foil, niobium blocks, rhodium blocks, and palladium granules were mixed in a molar ratio of 0.65:0.65:0.65:0.35:0.35 and then melted under an argon protective atmosphere using a high-current arc melting process (temperature...). 2000°C, current 100 A) A single metal ingot was formed and rapidly quenched on a water-cooled copper plate. To ensure thorough mixing of the components, all metal samples were remelted multiple times, ultimately yielding (ScZrNb). 0.65 [RhPd] 0.35 Alloy, as a medium-to-high entropy alloy superconducting joint.

[0034] like Figure 3 As shown, (ScZrNb) 0.65 [RhPd] 0.35 The resistivity of the alloy changes with temperature under different magnetic fields, ranging from 0 T to 9 T. Figure 3 It is known that without an external magnetic field, it undergoes a superconducting transition at 9.7 K, and even under an external magnetic field as high as 9 T, it can still undergo a zero-resistance transition. (ScZrNb) is chemically bonded. 0.65 [RhPd] 0.35 The medium-high entropy alloy superconducting joint does not contain elements such as Pb and Bi, making it more environmentally friendly.

[0035] Example 3 The Nb3Sn superwires obtained in Example 1 were connected using a metallurgical chemical reaction, as follows: Using HNO The superconducting wire was chemically etched with a solution to remove its outer Cu sheath. The diffusion barrier layer inside the Nb3Sn precursor wire was removed by mechanical polishing, exposing the inner Nb wire. Then, the end of the Nb3Sn superconducting wire precursor wire was spirally wound onto one end of an HfNbZrTi alloy core and pressed tightly with a metal support tube to ensure close contact between the filament and the active, fresh surface of the core. The wire was then heat-treated in a vacuum environment for 50 hours. During this heat treatment, Sn diffused from the Cu-Sn phase into the interior of the Nb filament, and also migrated to the surface of the HfNbZrTi alloy core and the Nb / alloy interface, subsequently reacting at the interface to form Nb. The Sn superconducting layer is now connected.

[0036] Example 4 (ScZrNb) prepared in Example 2 0.65 [RhPd] 0.35 The Nb3Sn superwires are joined together by an alloy through a metallurgical chemical reaction, as detailed below: Using HNO The superconducting wire is chemically etched with a solution to remove its outer Cu sheath. The diffusion barrier layer inside the Nb3Sn precursor wire is removed by mechanical polishing, exposing the inner Nb wire; then, the ends of the Nb3Sn precursor wire are spirally wound onto (ScZrNb). 0.65 [RhPd] 0.35 One end of the alloy is pressed with a metal support tube to ensure close contact between the filament and the active, fresh surface of the core; in a vacuum environment, it is heat-treated for 60 hours. During the heat treatment, Sn diffuses from the Cu-Sn phase into the interior of the Nb filament, and also diffuses into (ScZrNb). 0.65 [RhPd] 0.35 The Nb migrates to the surface of the alloy core and at the Nb / alloy interface, and then reacts at the interface to generate Nb. The Sn superconducting layer is now connected.

[0037] Application examples Comparison of conventional alloys (containing one or two metallic elements) with the high-entropy alloy of this invention Figure 4 As shown. In traditional alloys, atoms are usually arranged in a highly ordered, repeating crystal structure with a low overall entropy value, exhibiting a regular microscopic order. High-entropy alloys, however, break this paradigm; the "high entropy" in their name directly reflects the high degree of disorder within the system. These alloys are composed of multiple main elements in approximately equal proportions, with atoms randomly distributed in the crystal lattice, forming a highly disordered solid solution structure. Microscopically, this manifests as a chaotic chemical sequence and a diverse lattice arrangement. Due to their unique elemental composition, arrangement, and interaction potential, high-entropy alloys exhibit some significantly different properties from traditional alloys, summarized as "four major effects": the thermodynamic high-entropy effect, the structural lattice distortion effect, the kinetic hysteresis diffusion effect, and the property "cocktail" effect. The high-entropy effect enables high-entropy alloys to form "super solid solutions," the lattice distortion effect leads to a strong strengthening effect, and the hysteresis diffusion effect causes the formation of a large number of nanoscale precipitates. The combined effect of these factors results in structural characteristics different from traditional alloys, leading to unique properties and performance characteristics.

[0038] High strength, high hardness, and high wear resistance are the main mechanical properties of high-entropy alloys. The high-entropy effect makes high-entropy alloys "super solid solutions," with severe lattice distortion leading to strong solid solution strengthening, and hysteresis diffusion promoting the precipitation of nanocrystals. The combined effect of these factors results in the excellent mechanical properties of high-entropy alloys. Certain elements in high-entropy alloys readily form dense oxide films. Simultaneously, the alloys possess characteristics such as glass transition, microcrystallization, and single-phase structure, which provide favorable conditions for improving the corrosion resistance of high-entropy alloys.

[0039] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A medium-high entropy alloy superconducting joint for a superconducting cable, characterized in that, The medium-high entropy alloy superconducting joint is made of a medium-entropy alloy of 3-4 elements or a high-entropy alloy of 5 or more elements.

2. The medium-high entropy alloy superconducting joint according to claim 1, characterized in that, The elements include Li, Be, B, C, N, Mg, Al, Zn, Nb, Co, Fe, Cu, Mn, Ti, V, Ta, Cr, V, Zr, Hf, Ta, Mo, W, Sc, or Sn.

3. The medium-high entropy alloy superconducting joint according to claim 1, characterized in that, The medium-entropy alloy is Hf a Nb b Zr c Ti d Ta a Nb b Hf c Zr d or Nb a Sc b Hf c Zr d Ti a Nb b Ta c N d Fe a Ni b Co c Cr d Where 5≤a, b, c, d≤35, and a+b+c+d=100.

4. The medium-high entropy alloy superconducting joint according to claim 1, characterized in that, The high-entropy alloy is Hf a Nb b Ti c V d Zr e (ScZrNb) 1-x [RhPd] x Ta a Nb b Hf c Zr d Ti e Hf a Ta b Nb c Mo d W e or Nb a Re b Hf c Zr d Ti e , where 5≤a,b,c,d,e≤35, and a+b+c+d+e=100, 0.3≤x≤0.

4.

5. The medium-high entropy alloy superconducting joint according to claim 1, characterized in that, The medium-high entropy alloy superconducting joint is in the form of a thin sheet or a block; the thin sheet or block is grown by electric arc melting or laser levitation zone furnace.

6. The method for preparing a medium-to-high entropy alloy superconducting joint as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Under an argon atmosphere, 3-4 or more elements are mixed evenly, cold isostatically pressed into billets, sintered, and crystals are grown using a laser levitation zone furnace to obtain a medium-high entropy alloy superconducting joint.

7. The preparation method according to claim 5, characterized in that, The cold isostatic pressing was carried out at 160–200 MPa.

8. The preparation method according to claim 5, characterized in that, The crystal growth conditions are as follows: crystal growth is carried out at a growth rate of 3–6 mm / h, a rotation rate of 15–20 rpm, and a growth temperature of 1400°C–1500°C.

9. The application of the medium-high entropy alloy superconducting joint as described in any one of claims 1 to 5 in the connection of superconducting tapes, the series connection of superconducting magnets, or the formation of a closed-loop operation of superconducting magnet coils.

10. The application according to claim 9, characterized in that, The medium-high entropy alloy superconducting joint is placed between the ends of two superconducting strips and connected through a metallurgical chemical reaction.

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