High-plasticity and high-strength-ductility nickel-based alloy for second-generation high-temperature superconducting base band and preparation method of high-plasticity and high-strength-ductility nickel-based alloy

Abstract

The invention relates to a high-plasticity and high-strength-ductility nickel-based alloy for a second-generation high-temperature superconducting base band and a preparation method of the high-plasticity and high-strength-ductility nickel-based alloy, and belongs to the technical field of materials. The nickel-based alloy comprises the following chemical components in percentage by weight: 15.0-17.0% of Cr, 10.0-25.0% of W, 10.0-25.0% of Clt, 10.0-25.0% of Cu and the balance of Ni. 0.005%, Plt; 0.005%, Slt; 0.002%, Olt; 0.002%, Nlt; 0.002%, and the balance being nickel. The Ni-Cr-W ternary alloy component design thought is innovatively put forward, the W element content is optimally designed, the follow-up optimized homogenization treatment, the forging process, the hot rolling process, the solution treatment and the cold machining process are matched, and after the nickel-based alloy is annealed for 5 min at the temperature of 900 DEG C, the nickel-based alloy with the yield strength being 900 MPa or above, the tensile strength being 1100 MPa or above and the ductility being 30% or above can be obtained; the high-performance metal base band has good high-temperature oxidation resistance, and meets the requirements that the ductility of a second-generation high-performance metal base band for high-temperature superconducting reaches 30% or above, and the product of strength and elongation reaches 35.0 GPa.% or above.

Description

Technical Field

[0001] The present invention relates to a nickel-based alloy with high plasticity and high strength-plasticity product for a second-generation high-temperature superconducting baseband and a preparation method thereof, belonging to the technical field of materials. Background Art

[0002] Since the discovery of the second-generation superconductor of rare-earth barium copper oxide (REBCO, RE is a rare-earth element), it has attracted extensive international attention. The second-generation high-temperature superconductor has advantages such as a relatively high transition temperature, perfect diamagnetism, high critical current density, and high frozen magnetic field, and has achieved demonstration applications in many fields such as electric power, energy, and magnets. The most critical superconducting layer in REBCO is an oxide material with poor ductility. Since its thickness is generally less than 4 μm, it is also called coated superconductor.

[0003] The realization of the superconducting properties of REBCO requires other multifunctional coatings for protection. Usually, it is necessary to epitaxially grow a superconducting layer on a flexible metal baseband. The basis of the REBCO superconductor is a metal baseband, and the buffer layer, superconducting layer, and protective layer are all built on the metal baseband. Therefore, the comprehensive properties of the metal baseband determine the quality of the REBCO superconducting properties. The ion beam-assisted biaxial texture deposition technology (IBAD) has no specific requirements for the orientation and properties of the metal baseband and is one of the commonly used methods for commercially preparing REBCO superconducting layers. The optimal preparation process parameters of the IBAD technology are 850 °C to 900 °C. Therefore, it is required that the metal baseband not only has good mechanical properties but also has high tissue stability and excellent oxidation resistance at high temperatures. Currently, the commercially available Hastelloy C276 has excellent comprehensive properties and is the preferred material for superconducting alloy basebands. Although the tensile strength of C276 after cold deformation can be above 1500 MPa, due to the deformation storage energy accumulated by large cold deformation, recrystallization occurs during the preparation process of the superconducting coating, and its tensile strength will be reduced to below 1100 MPa. Moreover, due to its relatively high alloy element content and complex processing technology, its manufacturing cost is relatively high. Therefore, it is urgent to develop an alloy with low cost and mechanical properties equivalent to those of C276.

[0004] In addition, the applicant's three invention patents (application numbers are 202411589006.7, 202411672542.3, and 202411881969.4 respectively) are all targeted improvements based on Hastelloy C276. Although the tensile strength has been improved to a certain extent compared with C276, the alloy component content has increased to a certain extent and the preparation process is more complex, resulting in a significant increase in its manufacturing cost compared with C276. Among them, for the patent with the nitrogen alloy design concept (application number 202411672542.3), the plasticity reaches a maximum of 18.5% after annealing at 900°C for 5 minutes, still showing a certain gap compared with the Ni-Cr-W ternary alloy system designed in the present invention, which is more than 30%.

[0005] With the development of the second-generation high-temperature and high-field superconductors, higher requirements are put forward for the operating parameters of key equipment such as high-field superconducting magnets prepared for them. It is required that the metal baseband has better plasticity, for example, the elongation rate reaches more than 30% after annealing to better meet the requirements in aspects such as coil winding. In addition, it is also necessary to maintain the stability of its structure during the high-temperature preparation process of superconductors with a large cold deformation amount, and the tensile strength reaches more than 1100 MPa. At present, due to recrystallization, the tensile strength of the commercially available Hastelloy C276 metal baseband is reduced to less than 1100 MPa, and its plasticity is low and the cost is high, which cannot meet the development needs of the current second-generation low-cost high-temperature superconducting metal basebands. Therefore, there is an urgent need to develop a low-cost and high-plasticity nickel-based alloy for the second-generation high-temperature superconductors. Summary of the Invention

[0006] The purpose of the present invention is to provide a high-plasticity and high strength-plasticity product nickel-based alloy for the second-generation high-temperature superconducting baseband and its preparation method. Aiming at the low-cost requirement of the second-generation high-temperature superconducting baseband, the Ni-Cr-W ternary composition design concept is innovatively proposed. By adding an optimized content of W element, the solid solution strengthening effect and high melting point of W are utilized to improve the strength of the baseband after cold deformation and maintain the stability of the structure, and to increase the recrystallization temperature of the material after cold rolling. Pure and refined smelting is adopted to strictly control the content of O and N elements in the alloy to avoid the formation of large-size inclusions. The content of carbon element is strictly controlled, and a heat treatment process of homogenization annealing and solution quenching is adopted to avoid the precipitation of carbides and TCP phases. Finally, through cold deformation, a nickel-based alloy can be obtained with a yield strength of more than 1350 MPa, a tensile strength of more than 1450 MPa, and an elongation rate of more than 4.0%; after annealing at 900°C for 5 minutes, the yield strength reaches more than 900 MPa, the tensile strength reaches more than 1100 MPa, the elongation rate reaches more than 30%, and the strength-plasticity product reaches more than 35.0 GPa·%.

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

[0008] A nickel-based alloy with high plasticity and high strength-plasticity product for the second-generation high-temperature superconducting baseband. By weight percentage, its chemical composition is: Cr: 15.0 - 17.0%, W: 10.0 - 25.0%, C < 0.005%, P < 0.005%, S < 0.002%, O < 0.002%, N < 0.002%, and the balance is nickel.

[0009] For the nickel-based alloy with high plasticity and high strength-plasticity product for the second-generation high-temperature superconducting baseband, preferably, W: 17.0 - 23.0%.

[0010] For the nickel-based alloy with high plasticity and high strength-plasticity product for the second-generation high-temperature superconducting baseband, preferably, C < 0.002%, O < 0.001%.

[0011] The preparation method of the nickel-based alloy with high plasticity and high strength-plasticity product for the second-generation high-temperature superconducting baseband includes the following steps:

[0012] (1) Mix each chemical component in proportion, and obtain an ingot through pure purification smelting and electroslag remelting;

[0013] (2) Perform homogenization annealing treatment on the obtained ingot at high temperature. The temperature of the homogenization annealing treatment is 1230°C - 1250°C, hold for 10h - 20h and then air-cool to room temperature;

[0014] (3) Forge the ingot after homogenization annealing in the austenite phase region. The forging process is: forging temperature 1200°C - 1230°C, forging ratio above 6.0, and air-cool to room temperature after forging;

[0015] (4) Perform hot rolling on the forged alloy ingot: the rolling temperature is 1200°C - 1230°C, the reduction per pass of rolling is controlled at 20 - 30%, the total reduction is controlled at 70 - 90%, and water-cool to room temperature after hot rolling;

[0016] (5) Perform solution heat treatment after hot rolling. The solution heat treatment process is: hold at 1180°C - 1220°C for 2 - 4h and then water-quench to room temperature;

[0017] (6) Perform cold deformation after solution heat treatment. The cold deformation process is: perform cold deformation at room temperature, and the cold deformation amount is 60 - 80%.

[0018] For the preparation method of the nickel-based alloy with high plasticity and high strength-plasticity product for the second-generation high-temperature superconducting baseband, after step (6) cold deformation, the room temperature performance indexes of the nickel-based alloy are as follows: yield strength is 1350 - 1400 MPa, tensile strength is 1450 - 1510 MPa, and elongation is 4.0 - 6.0%.

[0019] The preparation method of the nickel-based alloy with high plasticity and high strength-plasticity product for the second-generation high-temperature superconducting baseband. After step (6), annealing treatment is carried out at 900 °C for 5 min, and the room-temperature performance indexes of the nickel-based alloy are as follows: yield strength is 900-950 MPa, tensile strength is 1100-1200 MPa, elongation is 31-37%, and strength-plasticity product is 37.0-42.0 GPa·%.

[0020] The description of the content range of the main elements in the present invention is as follows:

[0021] Cr: Chromium is an important element of the material of the present invention, which determines the corrosion resistance of the material of the present invention. This is because chromium improves the corrosion resistance of the material itself, making it easy to form a chromium oxide layer on it. However, when the Cr content is less than 15 wt%, the minimum corrosion resistance required for the alloy cannot be obtained. On the other hand, when the Cr content exceeds 17 wt%, chromium-rich intermetallic compounds are likely to precipitate, forming a chromium-depleted zone around the intermetallic compounds. This not only damages the hot working performance and mechanical properties of the material, but also deteriorates the oxidation corrosion resistance of the material. Therefore, in order to ensure that the material of the present invention has excellent corrosion resistance in corrosive media, the content of chromium in the alloy of the present invention is controlled to be: 15.0-17.0 wt%.

[0022] W: The function of tungsten is similar to that of Mo. It mainly plays a role in solid solution strengthening in the alloy system. Since the atomic radius of W is larger than that of Mo, the solid solution strengthening effect is greater than that of Mo. Moreover, due to the high melting point of W, appropriately increasing its content will, to a certain extent, increase the recrystallization temperature after cold working of the alloy. This is also one of the most critical design ideas of the present invention. In order to improve the strength and recrystallization temperature of the material of the present invention, the higher the W content, the better. However, too high W will cause the alloy to form relatively stable μ-phase and P-phase, which cannot be completely eliminated even when maintained at a very high solution temperature for a long time. In order to avoid the influence of the precipitated phase on the mechanical properties of the material, the content of W needs to be strictly controlled. Moreover, a higher W also brings certain difficulties to smelting preparation, and the content of W in the ternary system needs to be optimized. Therefore, the content of W in the alloy of the present invention is optimized and controlled to be 10.0-25.0%, and further optimized to be 17.0-23.0%.

[0023] C: Carbon is easy to form M 23 C6 carbides in the alloy, especially during the slow cooling process after solution treatment. Although the carbides precipitate at the grain boundary interface of the original austenite, they can pin dislocations and hinder the movement of the interface, playing a role in precipitation strengthening and effectively improving the strength of the material. However, the precipitation of these precipitated phases of carbides will affect the superconducting performance of the second-generation superconductor, and the carbon content in the alloy needs to be strictly controlled. Therefore, adopting the design idea of ultra-low carbon composition, the content of C in the alloy of the present invention is optimized and controlled to be: C < 0.005 w%, and further optimized to be C < 0.002 wt%.

[0024] S, P: In the production of nickel-based alloys, phosphorus and sulfur are usually regarded as harmful impurities because they can significantly reduce the overall properties of the alloy. P promotes the segregation of W and Mo to form Laves phases, thereby increasing the cold brittleness of the alloy, reducing the cohesion of grain boundaries, thus reducing the ductility and plasticity of the material. At the same time, it also affects the welding performance, resulting in cracks in the welded joints. On the other hand, sulfur increases the tendency of the material to thermal brittleness, especially during the processing. Excessive sulfur also affects the machining quality of the material, reducing the strength and toughness of the material. Therefore, the control of the content of sulfur and phosphorus in the alloy of the present invention is extremely strict: S < 0.002 wt%, P < 0.005 wt%.

[0025] O: Oxygen is the main element that generates oxide inclusions in the alloy. In order to reduce the inclusions in the alloy and ensure the purification of the material, it is necessary to minimize the oxygen content. When the oxygen content in the material exceeds a certain limit, especially when the material of the present invention contains a certain amount of Al, it will cause the formation of continuous brittle oxide inclusions in the alloy, resulting in stress concentration during the thin strip processing and leading to the occurrence of strip breakage accidents. Therefore, the control of the oxygen content in the alloy of the present invention is extremely strict: O < 0.002 wt%, and further optimized to O < 0.001 wt%.

[0026] N: Nitrogen is a strong austenite-forming element, which expands the austenite phase region and shrinks the ferrite phase region, and can inhibit the formation of high-temperature ferrite. Although nitrogen can increase the cold work hardening rate and improve the strength index of the alloy after cold working, due to the addition of a certain amount of B element in the present invention, in order to avoid the formation of BN inclusions, it is necessary to strictly control the content of N element in the material of the present invention. Therefore, the control of the nitrogen content in the alloy of the present invention is extremely strict: N < 0.002 wt%.

[0027] The innovative design concept of the present invention has four points, which are described as follows:

[0028] 1) Innovative ternary alloy composition design concept: According to the requirement of low cost for the second-generation superconducting base tapes, the present invention innovatively proposes the Ni-Cr-W ternary alloy design concept, achieving low-cost composition design. By adding an optimized content of W element, matching a simplified hot working and heat treatment regime, ensuring the complete solid solution of W in the ternary alloy system, and utilizing the high melting point of W, the stability of the cold-deformed microstructure of the material of the present invention is guaranteed, and its recrystallization temperature is increased. In addition, since the material of the present invention is required to meet the high plasticity and high strength-ductility product requirements of an elongation rate of more than 30% and a strength-ductility product of more than 35.0 GPa·% after annealing at 900 °C, Fe element is not added. The reason is that when Fe solid-solves into the matrix, it will aggravate the lattice distortion during the cold working process, thus affecting the mechanical properties of the material of the present invention after annealing, especially technical indicators such as elongation rate and strength-ductility product. The research results prove the correctness of the ternary alloy composition design concept. After cold deformation of 60% - 80%, the tensile strength of the material of the present invention is above 1450 MPa. Moreover, after annealing at 900 °C for 5 min, partial recrystallization and dynamic recovery occur in the material. Although the tensile strength decreases to 1100 MPa, the elongation rate increases from 4.0% to more than 30.0%, and the strength-ductility product reaches more than 35.0 GPa·%, far higher than the currently commercial Hastelloy C276.

[0029] 2) Matching of simplified processing and heat treatment regime: The Ni-Cr-W ternary alloy system of the present invention is simple, and the hot working processes such as forging and hot rolling are relatively simplified compared with the invention patents previously applied by the inventor. The back dissolution of μ and P and other TCP phases rich in W in the matrix can be achieved at a relatively low solution temperature, which not only guarantees the grain size of the material of the present invention, but also realizes the precipitation of no precipitated phases under rapid cooling. Therefore, the material preparation cost is further saved.

[0030] 3) Purified smelting technology: The material of the present invention adopts purified smelting technology, strictly controlling the contents of elements such as P, S, O, and N that are easy to form inclusions in the alloy, and strictly controlling the formation of inclusions in the material of the present invention, laying a good foundation for the preparation of subsequent thin-tape superconducting base materials.

[0031] In summary, the present invention innovatively proposes the Ni-Cr-W ternary alloy composition design concept. By optimizing the content of W element, matching the optimized hot working and heat treatment regime, ensuring the complete solid solution of W into the matrix to achieve solid solution strengthening and the effect of raising the recrystallization temperature, and combining with the increase in the strength of the matrix after cold deformation; controlling the C content, controlling the precipitation of carbides, and ensuring complete dissolution into the matrix during homogenization treatment; adopting purified smelting process, reducing the oxygen content in the alloy, reducing the inclusion content, and ensuring the high purity of the material.

[0032] The advantages and beneficial effects of the present invention are:

[0033] 1. Low-cost composition design: The ternary alloy system of the present invention is simple. The Ni matrix ensures the non-magnetic property of the baseband material, the Cr content ensures the high-temperature oxidation resistance, and the solid solution strengthening of W is fully exerted. The simple composition design and the subsequent simplification of the hot working and heat treatment systems achieve the low-cost preparation of materials, laying a solid material foundation for the rapid development of the second-generation high-temperature superconducting industry.

[0034] 2. The present invention adopts a purification smelting technology to greatly reduce the oxygen content in the materials of the present invention. On this basis, the contents of P, S, and N elements in the materials are further reduced to ensure that the inclusion content in the materials of the present invention is at an extremely low level, further improving its purity. Superconducting baseband materials with a thickness of 20 - 50 μm can be stably prepared, and a nickel-based alloy with high purity and high strength and toughness is obtained, meeting the requirements of high-temperature and high-field superconducting equipment for materials.

[0035] 3. The present invention provides a nickel-based alloy with high plasticity and high strength-plasticity product for the second-generation high-temperature superconducting baseband and a key preparation process. By adopting the technical solution provided by the present invention, a nickel-based superalloy with excellent strength-plasticity matching can be stably obtained. The materials of the present invention can better support the rapid development of the high-temperature and high-field superconducting industry in China and promote the upgrading of industry products. Brief Description of the Drawings

[0036] Figure 1 It is a schematic diagram of the scanning microstructure after forging in Example 1.

[0037] Figure 2 It is a schematic diagram of the scanning microstructure after solution treatment in Example 2.

[0038] Figure 3 It is a schematic diagram of the scanning microstructure after forging in Comparative Example 1

[0039] Figure 4 It is a schematic diagram of the scanning microstructure and energy dispersive spectroscopy (EDS) element distribution after solution treatment in Comparative Example 2.

[0040] Among them, (a) backscattered microstructure; (b) W element distribution. Detailed Description of the Invention

[0041] In the specific implementation process, in order to achieve low-cost design, the present invention proposes a Ni-Cr-W ternary alloy composition design for the first time in response to the needs of the second-generation high-temperature superconducting baseband. By optimizing the W content in the material of the present invention and matching the simplified hot processing and heat treatment system, the problem of the stable existence of TCP phases such as W-rich μ phase and P phase caused by the addition of W is solved, and the complete solid solution of W in the material of the present invention is achieved, and the role of W in solid solution strengthening and reducing the atomic migration rate in the material of the present invention is played, and the recrystallization temperature of the material of the present invention after cold deformation is increased, and the low cost of the composition design and processing preparation of the material of the present invention is achieved. At the same time, by controlling the C content in the material of the present invention, the precipitation of carbides is controlled to ensure that they are completely dissolved into the matrix during homogenization treatment; a purification smelting process is adopted to reduce the oxygen content in the alloy, control the inclusion content, and ensure the yield rate of the baseband. After cold deformation, the tensile strength of the material of the present invention reaches more than 1450MPa, and the elongation reaches more than 4.0%. After annealing at 900° C. for 5 minutes, the tensile strength of the material of the present invention reaches above 1100 MPa, the elongation reaches above 30.0%, and the strength-ductility product reaches above 35.0 GPa·%.

[0042] The following examples and drawings will further illustrate the present invention, but are not intended to limit the present invention. The nickel-based alloys in the examples and the alloys in the comparative examples were processed into standard plate-shaped tensile specimens after smelting and heat treatment to test the mechanical properties.

[0043] In the present invention, the preparation process of the high-plasticity, high-strength-plastic nickel-based alloy for the second-generation high-temperature superconducting base tape is: batching → smelting → casting → homogenization → forging and hot working → heat treatment → cold working. Examples 1 to 5 are all prepared by the following method, and the specific steps are as follows:

[0044] (1) mixing the chemical components in proportion, and obtaining an ingot through smelting and electroslag remelting;

[0045] (2) The temperature of the homogenization annealing treatment is 1230° C. to 1250° C. (Examples 1 to 5 are 1230° C., 1250° C., 1240° C., 1234° C., and 1244° C., respectively), and the temperature is kept for 10 h to 20 h (Examples 1 to 5 are 10 h, 20 h, 15 h, 18 h, and 13 h, respectively), and then air-cooled to room temperature;

[0046] (3) forging the ingot after homogenization annealing in the austenite phase region: the forging temperature is 1200° C. to 1230° C. (Examples 1 to 5 are 1200° C., 1230° C., 1220° C., 1215° C., and 1210° C., respectively), the forging ratio is greater than 6.0 (Examples 1 to 5 are 6.8, 11.0, 8.6, 7.0, and 9.5, respectively), and air-cooling to room temperature after forging;

[0047] (4) The forged alloy ingot is hot-rolled: the rolling temperature is 1200°C to 1230°C (1200°C, 1230°C, 1220°C, 1212°C, and 1218°C for Examples 1 to 5 respectively), the reduction per pass of rolling is controlled to be 20% to 30% (20%, 30%, 25%, 22%, and 28% for Examples 1 to 5 respectively), the total reduction is controlled to be 70% to 90% (70%, 90%, 80%, 75%, and 85% for Examples 1 to 5 respectively), and after hot rolling, it is water-cooled to room temperature;

[0048] (5) Solution heat treatment is carried out after hot rolling: the solution temperature is 1180°C to 1220°C (1180°C, 1220°C, 1200°C, 1210°C, and 1190°C for Examples 1 to 5 respectively), the holding time is 2.0 h to 4.0 h (2.0 h, 4.0 h, 3.0 h, 2.5 h, and 3.5 h for Examples 1 to 5 respectively), and after holding, it is water-cooled to room temperature;

[0049] (6) Cold deformation is carried out at room temperature after solution heat treatment: the cold deformation amount is 60.0% to 80.0% (60.0%, 80.0%, 70%, 64%, and 76% for Examples 1 to 5 respectively).

[0050] Next, the present invention will be further elaborated in detail through the accompanying drawings, examples, and comparative examples.

[0051] Example 1

[0052] In this example, by weight percentage, the chemical composition of the nickel-based alloy with high plasticity and high strength-plasticity product for the second-generation high-temperature superconducting baseband is: Cr: 16.05%, W: 20.3%, C: 15 ppm, S: 18 ppm, O: 9 ppm, P: 45 ppm, N: 15 ppm, and the balance is nickel.

[0053] Example 2

[0054] In this example, by weight percentage, the chemical composition of the nickel-based alloy with high plasticity and high strength-plasticity product for the second-generation high-temperature superconducting baseband is: Cr: 16.98%, W: 22.9%, C: 10 ppm, S: 16 ppm, O: 6 ppm, P: 38 ppm, N: 12 ppm, and the balance is nickel.

[0055] Example 3

[0056] In this example, by weight percentage, the chemical composition of the nickel-based alloy with high plasticity and high strength-plasticity product for the second-generation high-temperature superconducting baseband is: Cr: 15.03%, W: 17.2%, C: 19 ppm, S: 14 ppm, O: 7 ppm, P: 41 ppm, N: 16 ppm, and the balance is nickel.

[0057] Example 4

[0058] In this embodiment, by weight percentage, the chemical composition of the nickel-based alloy with high plasticity and high strength-plasticity product for the second-generation high-temperature superconducting baseband is: Cr: 15.49%, W: 19.1%, C: 13 ppm, S: 17 ppm, O: 8 ppm, P: 35 ppm, N: 13 ppm, and the balance is nickel.

[0059] Example 5

[0060] In this embodiment, by weight percentage, the chemical composition of the nickel-based alloy with high plasticity and high strength-plasticity product for the second-generation high-temperature superconducting baseband is: Cr: 16.54%, W: 21.8%, C: 17 ppm, S: 15 ppm, O: 5 ppm, P: 43 ppm, N: 14 ppm, and the balance is nickel.

[0061] Comparative Example 1

[0062] In this comparative example, by weight percentage, the chemical composition of the nickel-based alloy is: Cr: 16.07%, W: 8.0%, C: 13 ppm, S: 19 ppm, O: 8 ppm, P: 42 ppm, N: 16 ppm, and the balance is nickel. The chemical composition of the nickel-based alloy in this comparative example is similar to that in Example 1. The main difference is that the W content is 8.0%. Other homogenization treatment, forging process, hot rolling process, solution treatment and cold working process are exactly the same as those in Example 1.

[0063] Comparative Example 2

[0064] In this comparative example, by weight percentage, the chemical composition of the nickel-based alloy is: Cr: 16.92%, W: 32.0%, C: 12 ppm, S: 13 ppm, O: 7 ppm, P: 39 ppm, N: 15 ppm, and the balance is nickel. The chemical composition of the nickel-based alloy in this comparative example is similar to that in Example 2. The main difference is that the content of W element is 32.0%. Other homogenization treatment, forging process, hot rolling process, solution treatment and cold working process are exactly the same as those in Example 2.

[0065] As can be seen from Table 1, the present invention adopts an innovative chemical composition design. By adding W element with an optimized content and matching the simplified hot working process and heat treatment system, it ensures that W is completely dissolved into the matrix. Through a cold rolling reduction of 60% - 80%, an alloy with excellent strength-ductility matching can be obtained, with a yield strength above 1355 MPa, a tensile strength above 1458 MPa, and an elongation above 4.0%. In Comparative Example 1, 8.0% of W element was added, which is not within the W content range of the present invention. Comparing with Example 1, it was found that the yield strength of the Ni-Cr-W alloy with 8.0% W content only reached 1016 MPa and the tensile strength reached 1066 MPa, lower than the mechanical property indexes of the materials of the present invention. In Comparative Example 2, the W element content was as high as 32.0% W, which is not within the optimized W composition range of the present invention. Comparing with Example 2, it was found that although both the yield strength and the tensile strength reached the required range of the materials of the present invention, the elongation was only 1.0%, lower than 4.0%, and the strength-ductility product was lower, not within the required range of the present invention.

[0066] Table 1 Mechanical properties of the cold-rolled sheets of the examples and comparative examples

[0067] Serial number <![CDATA[Yield strength Rp 0.2 , MPa]]> Tensile strength Rm, MPa Elongation A, % Product of strength and plasticity, GPa·% Example 1 1376 1486 5.2 7.73 Example 2 1400 1507 4.0 6.03 Example 3 1355 1458 6.0 8.75 Example 4 1367 1473 5.6 8.25 Example 5 1384 1492 4.8 7.16 Comparative example 1 1016 1066 10.0 10.66 Comparative example 2 1530 1651 1.0 1.65

[0068] As can be seen from Table 2, after annealing at 900 °C for 5 min, the yield strength of the materials of the present invention is above 905 MPa, the tensile strength is above 1118 MPa, the elongation is above 31.5%, and the strength-ductility product reaches above 37.77 GPa·%. This is because W is completely dissolved into the alloy matrix. Although partial recrystallization occurs in the materials of the present invention and the tensile strength decreases to about 1100 MPa, the plasticity is significantly improved. In Comparative Example 1, the added W content is relatively low, and complete recrystallization occurs in the material, with its yield strength decreasing to 534 MPa and the tensile strength only being 884 MPa. Although the strength-ductility product index meets the requirements, the yield strength and tensile strength indexes do not meet the requirements of the materials of the present invention. In Comparative Example 2, the W content exceeds the requirement range of the materials of the present invention, resulting in a large amount of undissolved W-rich phase in the matrix. Although the strength index meets the requirements after annealing, its plasticity is only 1.5% and the strength-ductility product is 2.06 GPa·%, not meeting the index requirements of the materials of the present invention.

[0069] Table 2 Mechanical properties of the cold-rolled sheets of the examples and comparative examples after annealing at 900 °C for 5 min and air cooling

[0070] Serial number <![CDATA[Yield strength Rp 0.2 , MPa]]> Tensile strength Rm, MPa Elongation A, % Product of strength and plasticity, GPa·% Example 1 921 1160 34.2 39.67 Example 2 935 1199 31.5 37.77 Example 3 905 1118 36.5 40.81 Example 4 914 1140 35.5 40.47 Example 5 930 1181 32.0 37.79 Comparative example 1 534 884 41.0 36.24 Comparative example 2 1238 1377 1.5 2.06

[0071] As Figure 1As shown, the scanning microstructure of Example 1 after air cooling following large deformation forging at 1200°C. It can be seen from the figure that after one heat treatment, the dendrites of the original as-cast structure are broken. During the homogenization and the holding stage before forging, W in the nickel-based alloy matrix redissolves into the nickel-based alloy matrix. After forging and cooling, partial recrystallization occurs in the material of the present invention, and the recrystallization volume fraction is 10%.

[0072] As Figure 2 shown, the scanning microstructure of Example 2 after solution treatment at 1220°C for 4 h. It can be seen from the scanning backscattered image that after homogenization treatment, large deformation forging, hot rolling, and solution treatment, 22.9 wt% of W in Example 2 completely dissolves into the matrix, and there are no W-rich precipitates at the grain boundaries and within the grains.

[0073] As Figure 3 shown, the scanning microstructure of Comparative Example 1 after air cooling following large deformation forging at 1200°C. It can be seen from the figure that although Comparative Example 1 added 8.0 wt% of Re element, which is lower than the composition range required by the present invention, after one forging heat treatment, recrystallization occurs in the matrix, and the recrystallization volume fraction is as high as over 85%.

[0074] As Figure 4 (a) and (b) shown, the scanning electron microscope (SEM) microstructure of Comparative Example 2 after solution treatment at 1220°C for 4 h. It can be seen from the figure that since Comparative Example 2 added 32.0 wt% of W element, which is higher than the composition range required by the present invention, there are still W-rich second phases in the matrix after solution treatment at 1220°C for 4 h. As Figure 4 (b) shown, a large number of large particles of W-rich phases in the matrix result in low plasticity.

[0075] The mechanical property test results of the above Examples 1 - 5 show that the unique Ni-Cr-W ternary alloy system of the present invention and the simplified processing and heat treatment system achieve the low-cost preparation of the second-generation high-temperature superconducting baseband. By adopting the technical solution of the examples of the present invention, the content of W element is optimized to be between 17% and 23%, and Fe does not need to be added. Matching the subsequent optimized homogenization treatment, forging process, hot rolling process, solution treatment, and cold processing process, after cold rolling, a yield strength of 1355 MPa or more, a tensile strength of 1458 MPa or more, and an elongation of 4.0% or more can be obtained; after annealing at 900°C for 5 min, a yield strength of 905 MPa or more, a tensile strength of 1118 MPa or more, an elongation of 31.5% or more, and a strength-plasticity product of 37.77 GPa·% or more can be obtained, meeting the requirements of the second-generation high-temperature superconducting high-strength metal baseband with an elongation of 30% or more and a strength-plasticity product of 35.0 GPa·% or more.

[0076] The above embodiments are only used to illustrate the technical concept and features of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. It should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A nickel-based alloy with high plasticity and high strength-plasticity product for the second-generation high-temperature superconducting baseband, characterized in that, By weight percentage, its chemical composition is: Cr: 15.0 - 17.0%, W: 10.0 - 25.0%, C < 0.005%, P < 0.005%, S < 0.002%, O < 0.002%, N < 0.002%, and the balance is nickel.

2. The high-plasticity and high strength-plasticity product nickel-based alloy for the second-generation high-temperature superconducting baseband according to claim 1, characterized in that, Preferably, W: 17.0 - 23.0%.

3. The high-plasticity and high strength-plasticity product nickel-based alloy for the second-generation high-temperature superconducting baseband according to claim 1, characterized in that, Preferably, C < 0.002%, O < 0.001%.

4. A method for preparing a nickel-based alloy with high plasticity and high strength-plasticity product for a second-generation high-temperature superconducting baseband according to any one of claims 1 to 3, characterized in that, It includes the following steps: (1) Mix each chemical component in proportion, and obtain an ingot through purification smelting and electroslag remelting. (2) Anneal the obtained ingot at a high temperature for homogenization. The temperature for homogenization annealing is 1230°C - 1250°C. After holding for 10h - 20h, air-cool to room temperature. (3) Forge the ingot after homogenization annealing in the austenite phase region. The forging process is: forging temperature 1200°C - 1230°C, forging ratio above 6.0, and air-cool to room temperature after forging. (4) Hot-roll the forged alloy ingot: rolling temperature 1200°C - 1230°C, reduction per pass of rolling controlled at 20 - 30%, total reduction controlled at 70 - 90%, and water-cool to room temperature after hot-rolling. (5) Conduct solution heat treatment after hot-rolling. The solution heat treatment process is: hold at 1180°C - 1220°C for 2 - 4h and then water-quench to room temperature. (6) Conduct cold deformation after solution heat treatment. The cold deformation process is: conduct cold deformation at room temperature, and the cold deformation amount is 60 - 80%.

5. The preparation method of the nickel-based alloy with high plasticity and high strength-plasticity product for the second-generation high-temperature superconducting baseband according to claim 4, characterized in that, After step (6) of cold deformation, the room temperature performance indexes of the nickel-based alloy are as follows: yield strength is 1350 - 1400 MPa, tensile strength is 1450 - 1510 MPa, and elongation is 4.0 - 6.0%.

6. The preparation method of the nickel-based alloy with high plasticity and high strength-plasticity product for the second-generation high-temperature superconducting baseband according to claim 4, characterized in that, After step (6), anneal at 900°C for 5 min to obtain the room temperature performance indexes of the nickel-based alloy as follows: yield strength is 900 - 950 MPa, tensile strength is 1100 - 1200 MPa, elongation is 31 - 37%, and the product of strength and plasticity is 37.0 - 42.0 GPa·%.

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