An ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material, its preparation method, and its applications.

Abstract

This invention discloses an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material, its preparation method, and its applications, belonging to the technical field of new copper alloy materials. The alloy composition, by mass fraction, is: Mg: 0.1-0.6%; Sc: 0.02-0.10%; the balance being copper and other unavoidable impurities. The alloy of this invention is prepared through microalloying design combined with a multi-stage plastic deformation process via the following steps: vacuum melting – solution treatment – ​​equal-channel angle extrusion – rolling. During the deformation process, a multi-scale strengthening structure is formed, including nanoscale Cu4Sc precipitates, high dislocation density, high-density large-angle grain boundaries, nanotwins, and an average grain size of approximately 2 μm. By controlling the microstructure, its strength and toughness are improved, and it exhibits excellent high-temperature performance.

Description

Technical Field

[0001] This invention relates to a Cu-Mg-Sc copper alloy material, its preparation method, and its application, particularly to an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material, its preparation method, and its application, belonging to the technical field of new copper alloy materials. Background Technology

[0002] New-generation information technology, advanced rail transit equipment, aerospace equipment, energy-saving and new energy vehicles, 5G communications, and high-speed railway overhead contact line equipment are key high-tech fields that my country is focusing on developing. High-performance copper alloys are one of the crucial basic materials in these fields. High-performance copper alloys possess a series of excellent properties, including high electrical conductivity, high thermal conductivity, high strength, high corrosion resistance, plating suitability, and ease of processing, making them an indispensable material type for the development of these fields. They play an irreplaceable role in meeting the practical application needs of numerous products for integration, functionalization, miniaturization, lightweighting, energy saving, and reliability.

[0003] These high-tech industries are placing increasingly stringent and comprehensive performance requirements on high-performance copper alloys due to their increasingly complex service environments. Copper alloys must not only possess ideal strength and conductivity at room temperature, but also exhibit good high-temperature strength, softening temperature resistance, and high-temperature structural stability in high-temperature environments. Contact wires operate in the harshest environment of all power supply conductors, needing to withstand impacts, vibrations, temperature variations, environmental corrosion, abrasion, electrical spark erosion, and extreme working tension during normal operation. Therefore, their performance directly affects the safe operation of high-speed trains. Currently, the main development direction for copper alloys is to improve their strength and high-temperature performance through alloying, heat treatment, and deformation processes while maintaining high conductivity.

[0004] Therefore, designing novel alloys based on requirements and selecting appropriate strengthening methods to resolve the contradiction between strength and conductivity has become a hot topic in the research of high-strength, high-conductivity copper alloys. Currently popular high-strength, high-conductivity copper alloys have formed several alloy series, such as Cu-Mg / Ag / Sn, Cu-Fe-P, Cu-Cr-Zr, Cu-Ni-Si, and Cu-based composites. Among them, the Cu-Fe-P, Cu-Cr-Zr, and Cu-Ni-Si series are age-precipitation strengthened copper alloys with excellent comprehensive properties. However, the preparation of age-precipitation strengthened copper alloys requires complex processing procedures. Another type, the Cu-Mg / Ag / Sn series, is a solution- and work-strengthened copper alloy, which can maintain high conductivity while achieving high tensile strength. The addition of Mg can also increase the recrystallization temperature of the copper alloy. Clearly, appropriate alloy composition design is the foundation for obtaining high-performance materials, but processing technology also has a significant impact on material performance. The development of high-strength, high-heat-resistant, and high-conductivity copper alloy materials is mainly achieved through material design and optimized preparation processes.

[0005] This invention selects a solid solution strengthened conductive copper alloy primarily based on the following two considerations. First, solid solution strengthened conductive copper alloys with Mg as the main alloying element, after dislocation strengthening, can achieve high comprehensive mechanical and electrical properties, possessing a wide performance control range, and are widely used in fields such as railway tram contact lines. Second, the processing technology of this type of alloy is relatively simple; the strengthening mechanism mainly consists of solid solution strengthening, dislocation strengthening, and grain boundary strengthening, without the influence of complex factors such as aging precipitation, making it suitable for industrial production. High-strength, high-conductivity, and heat-resistant copper materials with qualified properties need to maintain high strength while also possessing sufficient plasticity to facilitate subsequent processing into various required shapes, while maintaining high strength in high-temperature environments. This invention requires the use of appropriate preparation methods to obtain copper-magnesium alloy materials with a good match of strength, plasticity, and high-temperature performance. This invention uses rare earth microalloying on solid solution strengthened copper-magnesium alloys, maintaining the simplicity of the solid solution strengthening process, while utilizing the advantages of rare earth microalloying in purifying the matrix and micro-precipitation strengthening to further improve the strength and high-temperature resistance of the copper alloy. The preparation and processing methods of copper-magnesium-scandium-copper alloy materials have not yet been found, therefore the preparation and processing of materials with this composition deserve further research.

[0006] Chinese patent application number 202310861131.8 discloses a high-strength, high-conductivity, and wear-resistant copper-magnesium alloy and its preparation method. This high-strength, high-conductivity, and wear-resistant copper-magnesium alloy, by mass fraction, comprises the following components: 0.45-0.55 wt% Mg, 0.0001-0.01 wt% M, and the remainder Cu. The method adjusts the alloy element content and initial grain structure through smelting and casting, and adjusts the final grain structure, texture type, and content through extrusion and drawing, ultimately achieving the characteristics of high strength, high conductivity, and high wear resistance.

[0007] Chinese patent application number 201510926780.7 discloses a high-strength, high-conductivity copper-magnesium alloy and its preparation method. This alloy achieves superior strength and conductivity compared to traditional copper-magnesium alloys by adding calcium and trace amounts of boron. The alloy's chemical composition is: Mg: 0.2-0.8 wt%; Ca: 0.05-0.5 wt%; B: 0.005-0.01 wt%; balance Cu and unavoidable impurities. The preparation process includes non-vacuum induction melting, casting, milling, cold working, intermediate annealing, cold finishing, and final annealing. Summary of the Invention

[0008] To further improve the strength and high-temperature resistance of copper-magnesium alloys and obtain copper-magnesium alloy materials with a good match between strength, toughness and high-temperature performance, this invention provides a method for preparing ultrafine-grained, high-strength, high-conductivity and high-heat-resistant Cu-Mg-Sc copper alloy materials. By adding trace amounts of the rare earth element scandium and combining large plastic deformation with subsequent room temperature rolling, copper-magnesium alloy materials with a good match between strength, toughness and high-temperature performance are finally obtained.

[0009] Meanwhile, this invention provides an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material.

[0010] Meanwhile, this invention provides an application of an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material in high-temperature and high-conductivity applications.

[0011] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0012] A high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material with the following composition by mass fraction: Mg: 0.1-0.6%; Sc: 0.02-0.10%; the balance being copper and other unavoidable impurities.

[0013] This invention adjusts the composition and initial grain structure of the material through smelting and casting, and obtains ultrafine-grained copper-magnesium alloy material by room temperature rolling combined with equal channel angular extrusion.

[0014] A method for preparing an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material includes the following steps:

[0015] S1: Vacuum Induction Melting: The melting equipment is a VVlco-100-25 type vacuum induction melting furnace. The materials are batched according to the composition of the copper alloy. First, a 99.99% pure upward-drawing copper rod is placed in the crucible, and a vacuum is drawn to 500 Pa. Heating is then performed at 20 kW for 10 minutes, raising the temperature to 800℃~900℃. The vacuum is then stopped, and a protective atmosphere of 99.99% argon is introduced. The power is increased to 35 kW to completely melt the copper. Then, 99.99% pure magnesium blocks and magnesium-scandium master alloys are added. After all the newly added alloying elements have melted, a holding temperature of 1200-1250℃ is applied for 5-8 minutes. Finally, the copper alloy ingot is cast. The impurity content of the ingot is ≤0.05%, and the oxygen content is ≤6 ppm.

[0016] S2: Pre-treatment and equal channel corner extrusion processing:

[0017] Cu-Mg-Sc copper alloy ingots were cut into square columnar specimens using an electrical discharge wire cutting machine.

[0018] The square columnar specimen was cleaned, dried, and polished.

[0019] The cubic columnar specimen was solution treated and then water-cooled.

[0020] The square columnar specimen and the mold were preheated.

[0021] The square columnar specimen was subjected to equal-channel corner extrusion processing.

[0022] Furthermore, the Cu-Mg-Sc copper alloy ingot is cut into square columnar specimens using an electrical discharge wire cutting machine, with a cutting size of 19.5*19.5*45mm.

[0023] Furthermore, the cleaning, drying, and polishing process for the square columnar specimen includes ultrasonic cleaning, drying, and polishing with 1000# silicon carbide sandpaper.

[0024] Furthermore, the solution treatment and water cooling of the cubic columnar specimen refers to placing the specimen in an SX2-12-12 type box-type resistance furnace at a solution temperature of 850-880℃ for 1-1.5 hours, followed immediately by water quenching in clean water. Water quenching refers to immediately immersing the solution-treated sample in clean water at room temperature for cooling.

[0025] Furthermore, before preheating the cubic columnar specimen and the mold, a graphite lubricant is applied to the mold and the cubic columnar specimen.

[0026] Furthermore, the preheating treatment of the cubic columnar specimen and the mold includes first placing the mold in a muffle furnace for preheating for 40-60 minutes, and then placing the cubic columnar specimen in the mold for further preheating for 20-30 minutes, with a preheating temperature of 350-400℃.

[0027] Furthermore, the cylindrical specimen is subjected to equal channel corner extrusion processing, with 8-12 extrusion passes.

[0028] Furthermore, the square columnar specimen undergoes equal-channel angular extrusion processing at a speed of 15-20 mm / min, with the die rotating 90° in adjacent passes. Further, the equal-channel angular extrusion processing of the square columnar specimen includes heat treatment of the specimen and die every four passes at a temperature of 350-400℃ for 10-20 minutes, followed by water cooling of the specimen after extrusion.

[0029] S3: Room temperature rolling: This process consists of the following steps:

[0030] The specimen obtained in step S2 was cut into slices using wire cutting.

[0031] The cut sheet-like specimens were cleaned and polished.

[0032] The treated sheet specimens were rolled at room temperature.

[0033] Furthermore, the cut sheet specimens are cleaned and polished, including ultrasonic cleaning and drying, and polishing with silicon carbide sandpaper to remove surface dirt and oxide layer.

[0034] Furthermore, the prepared sheet specimen is subjected to room temperature rolling using a ZK-WS1C type rolling mill, with a rolling reduction of 50-95%, a unidirectional double-sided rolling direction, and a single reduction of 4-10%.

[0035] Application of an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material in high-temperature and high-conductivity applications, including railway tram contact wires, aerospace wires, or new energy vehicle connectors.

[0036] A railway tram contact wire is prepared according to the present invention using an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material.

[0037] An aerospace conductor is prepared from an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material according to the present invention.

[0038] A connector for new energy vehicles is prepared from an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material according to the present invention.

[0039] The beneficial effects achieved by this invention are as follows:

[0040] (1) The addition of trace rare earth element Sc to Cu-0.4Mg alloy can improve its comprehensive performance. The preparation process is simple. The formation of nanoscale Cu4Sc precipitates through the Orovan mechanism significantly improves the strength and hardness of the copper alloy. It is highly coherent with the copper matrix, with small lattice mismatch. The interfacial strain field can further enhance the dislocation pinning effect. At the same time, the Cu4Sc precipitate is small in size, only nanoscale (<10nm), and has a relatively uniform distribution, resulting in a significant strengthening effect. It can improve the room temperature strength of the material. At the same time, the melting point of Cu4Sc is about 1000℃, which helps to maintain structural stability in high-temperature environments. The Sc atom diffusion rate is low, and the precipitate coarsens slowly at high temperatures, making it suitable for high-temperature applications. The thermal expansion coefficient of Cu4Sc is close to that of the Cu matrix, which can reduce the risk of interfacial stress cracking during thermal cycling and improve the strength and high-temperature performance of the material (including thermal stability and high-temperature tensile strength). Sc element easily forms a dense oxide layer Sc2O3, which can inhibit further oxidation of the Cu matrix and improve the corrosion resistance of the alloy in humid and high-temperature oxidizing environments.

[0041] (2) The process of this invention is simple and does not require a complicated and precisely controlled process. After melting and casting and after solution treatment, the microstructure is controlled by a combination of equal channel corner extrusion and rolling to improve its strength and toughness, and maintains a relatively stable conductivity to improve the overall performance of the material, achieving high strength, high conductivity and heat resistance.

[0042] The alloy of this invention is prepared through microalloying design combined with a multi-stage plastic deformation process via the following steps: vacuum melting, solution treatment, isochannel angular extrusion, and rolling. During deformation, a multi-scale strengthening structure is formed, including nanoscale Cu4Sc precipitates, high dislocation density, high-density large-angle grain boundaries, nanotwins, and an average grain size of approximately 2 μm. Controlling the microstructure improves its strength and toughness, and it exhibits excellent high-temperature performance. The addition of trace rare earth elements enhances overall performance, and subsequent processing further improves strength while maintaining relative plasticity stability, thus improving the material's overall performance and achieving a reasonable balance between strength, toughness, and heat resistance. Its room temperature tensile strength is ≥720 MPa, elongation ≥30%, 200℃ high-temperature strength retention ≥95%, 300℃ high-temperature strength retention ≥82%, and conductivity ≥60% IACS. It possesses both ultra-high strength and high-temperature stability, making it suitable for high-temperature, high-conductivity applications such as aerospace wires and new energy vehicle connectors. This invention's process is green and efficient, requiring no complex aging treatment, and has promising industrial prospects. Attached Figure Description

[0043] Figure 1 This is a room temperature metallographic image of the as-cast Cu-Mg-Sc alloy of the present invention, which is characterized by its ultrafine grain, high strength, high conductivity, and heat resistance.

[0044] Figure 2 This is the tensile curve of Cu-Mg-Sc alloy 8P in Example 1 of the present invention;

[0045] Figure 3 This is the tensile curve of the ultrafine-grained, high-strength, high-conductivity, and heat-resistant Cu-Mg-Sc alloy 8P+CR50% from Embodiment 2 of the present invention.

[0046] Figure 4 This is the tensile curve of Cu-Mg-Sc alloy 12P in Example 3 of the present invention;

[0047] Figure 5 This is the tensile curve of the ultrafine-grained, high-strength, high-conductivity, and heat-resistant Cu-Mg-Sc alloy 12P+CR50% in Example 4 of the present invention;

[0048] Figure 6 This is a room temperature tensile fracture scan (500X) of Cu-Mg-Sc alloy 8P from Example 1 of the present invention.

[0049] Figure 7 This is a room temperature tensile fracture scan (500X) of the ultrafine-grained, high-strength, high-conductivity, and heat-resistant Cu-Mg-Sc alloy 8P+CR50% from Embodiment 2 of the present invention.

[0050] Figure 8 This is a room temperature tensile fracture scan (500X) of Cu-Mg-Sc alloy 12P from Example 3 of the present invention.

[0051] Figure 9 This is a room temperature tensile fracture scan (500X) of the ultrafine-grained, high-strength, high-conductivity, and heat-resistant Cu-Mg-Sc alloy 12P+CR 50% from Example 4 of the present invention.

[0052] Figure 10 This is a TEM observation of the Cu4Sc precipitate and mapping diagram of the ultrafine-grained, high-strength, high-conductivity, and heat-resistant Cu-Mg-Sc alloy in the 12P+CR 50% state of the present invention.

[0053] Figure 11 This is a high-resolution TEM image and diffraction calibration diagram of the Cu4Sc precipitate phase in the 12P+CR50% state of the ultrafine-grained, high-strength, high-conductivity, and heat-resistant Cu-Mg-Sc alloy of this invention.

[0054] Figure 12 This is a dislocation structure diagram observed by TEM in the 12P+CR 50% state of the ultrafine-grained, high-strength, high-conductivity, and heat-resistant Cu-Mg-Sc alloy of this invention;

[0055] Figure 13This is a TEM image of the twin structure of the ultrafine-grained, high-strength, high-conductivity, and heat-resistant Cu-Mg-Sc alloy of this invention in the 12P+CR 50% state;

[0056] Figure 14 This is a TEM image of the overall grain morphology distribution of the ultrafine-grained, high-strength, high-conductivity, and heat-resistant Cu-Mg-Sc alloy in the 12P+CR 50% state of the present invention. Detailed Implementation

[0057] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Example 1

[0058] A method for preparing Cu-Mg-Sc copper alloy material, the preparation and processing methods of this embodiment are as follows:

[0059] (1) Using oxygen-free copper, magnesium blocks with a purity of 99.99% and magnesium-scandium master alloy as raw materials, the proportion of copper alloy material is 0.37wt% Mg and 0.07wt% Sc, with the balance being copper.

[0060] (2) Vacuum induction casting: First, put the 99.99% copper rod into the crucible, then evacuate to 500Pa, heat with 20kW power for 10min, raise the temperature to 850℃, stop evacuating and fill with a protective atmosphere of 99.99% argon, raise the power to 35kW to completely melt the copper, then add 99.99% magnesium blocks and magnesium scandium intermediate alloy, and after all the newly added alloy elements have melted, perform heat preservation treatment at 1200℃ for 5 minutes, then cast the copper alloy ingot. Before casting, preheat the mold.

[0061] (3) The Cu-Mg-Sc copper alloy ingot was cut into 19.5*19.5*45mm square columnar specimens using an electrical discharge wire cutting machine. The specimens were then cleaned, dried, polished, and solution treated. The solution temperature was 850℃, and the solution time was 1 hour. After the solution treatment, the specimens were immediately placed in clean water for water quenching. Graphite lubricant was then applied to the surface of the specimens and the mold. The mold was preheated in a muffle furnace for 40 minutes, and then the specimens were placed in the molds for another 20 minutes of preheating. The preheating temperature was 350℃. The specimens were then subjected to equal channel corner extrusion for 8 passes at a speed of 15mm / min, with a 90° rotation between adjacent passes. The specimens were held at 400℃ for 10 minutes after each of the four passes. After extrusion, the specimens were water-cooled to prevent grain growth.

[0062] like Figure 2As shown, the copper-magnesium-scandium alloy can be obtained through the above steps. Its room temperature (20℃) tensile strength can reach 607.3MPa, elongation can reach 40.3%, and hardness is 184.8HV; its 200℃ tensile strength is 570.8MPa, elongation is 37.58%, and high-temperature strength retention rate is as high as 94%; its 300℃ tensile strength is 510.2MPa, elongation is 39.46%, high-temperature strength retention rate is 84%, and conductivity is 61.3% IACS.

[0063] like Figure 6 The figure shows the room temperature tensile fracture morphology of copper-magnesium-scandium alloy processed by 8 passes of ECAP. It is a ductile fracture with dimples that are basically equiaxed, indicating that the alloy has good plasticity and a fracture elongation of 40%. Example 2

[0064] Steps (1), (2), and (3) in this embodiment are the same as steps (1), (2), and (3) in embodiment 1;

[0065] (4) Room temperature rolling: The specimen obtained in step (3) of this embodiment is cut into sheet specimens by wire cutting machine. Then the cut sheet specimens are cleaned and polished. Then, room temperature rolling is performed using ZK-WS1C type rolling mill with a reduction of 50%. Unidirectional double-sided rolling is performed with a single reduction of 10%.

[0066] Application of an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material in high-temperature and high-conductivity applications, including railway tram contact wires, aerospace wires, or new energy vehicle connectors.

[0067] like Figure 3 As shown, the copper-magnesium-scandium alloy material obtained through the above steps has a tensile strength of 662.1 MPa, an elongation of 31.8%, and a hardness of 185.4 HV; a tensile strength of 642.1 MPa at 200℃, an elongation of 21.3%, and a high-temperature strength retention rate of up to 97%; a tensile strength of 583.3 MPa at 300℃, an elongation of 19%, and a high-temperature strength retention rate of 88%; and an electrical conductivity of 61% IACS.

[0068] like Figure 7 As shown, this embodiment is the room temperature tensile fracture morphology of copper-magnesium-scandium alloy rolled in 8 passes with a reduction of 50%. The fracture surface has a large number of dimples, which are arranged in a certain direction, indicating that the grains are elongated along the rolling direction. In addition to the dimples, there are also some cleavage planes. The surface plasticity of the copper-magnesium-scandium alloy rolled in 8 passes with a reduction of 50% is lower than that of the alloy processed in 8 passes, but it is still a ductile fracture. The fracture diffraction rate of the alloy exceeds 30%. Example 3

[0069] Steps (1) and (2) in this embodiment are the same as steps (1) and (2) in embodiment 1;

[0070] (3) The Cu-Mg-Sc copper alloy ingot was cut into 19.5*19.5*45mm square columnar specimens using an electrical discharge wire cutting machine. The specimens were then cleaned, dried, polished, and solution treated. The solution temperature was 850℃, and the solution time was 1 hour. After the solution treatment, the specimens were immediately placed in clean water for water quenching. Graphite lubricant was then applied to the surface of the specimens and the mold. The mold was preheated in a muffle furnace for 40 minutes, and then the specimens were placed in the mold for another 20 minutes of preheating. The preheating temperature was 350℃. The specimens were then subjected to equal channel corner extrusion for 12 passes at a speed of 15mm / min, with a 90° rotation between adjacent passes. The specimens were held at 400℃ for 10 minutes after each of the four passes. After extrusion, the specimens were water-cooled to prevent grain growth.

[0071] like Figure 4 As shown, the copper-magnesium-scandium alloy can be obtained through the above steps. Its room temperature tensile strength can reach 631 MPa, elongation can reach 41.4%, and hardness is 226.1 HV; its tensile strength at 200℃ is 601 MPa, elongation is 35.2%, and high-temperature strength retention rate is as high as 95.2%; its tensile strength at 300℃ is 532 MPa, elongation is 32%, high-temperature strength retention rate is 85%, and conductivity is 60.8% IACS.

[0072] like Figure 8 The image shows the room temperature tensile fracture morphology of a copper-magnesium-scandium alloy processed by ECAP in 12 passes. It has a large number of dimples, and the dimple size is slightly smaller than that of the copper-magnesium-scandium alloy processed in 8 passes, indicating ductile fracture. The alloy has a fracture elongation of 41%. Example 4

[0073] Steps (1), (2), and (3) in this embodiment are the same as steps (1), (2), and (3) in embodiment 3;

[0074] (4) Room temperature rolling: The specimen obtained in step (3) of this embodiment is cut into sheet specimens by wire cutting machine, and then the cut sheet specimens are cleaned and polished. Then, room temperature rolling is performed using ZK-WS1C type rolling mill with a reduction of 50%, and unidirectional double-sided rolling is performed with a single reduction of 10%.

[0075] Application of an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material in high-temperature and high-conductivity applications, including railway tram contact wires, aerospace wires, or new energy vehicle connectors.

[0076] like Figure 5As shown, the copper-magnesium-scandium alloy material finally obtained in step (4) has a tensile strength of 721 MPa, an elongation of 33%, and a hardness of 226.8 HV; a tensile strength of 698 MPa at 200℃, an elongation of 23%, and a high-temperature strength retention rate of up to 96.8%; a tensile strength of 589 MPa at 300℃, an elongation of 30%; a high-temperature strength retention rate of 82%; and a conductivity of 60.5% IACS.

[0077] like Figure 9 The image shows the tensile fracture morphology of copper-magnesium-scandium alloy rolled by ECAP with 12 passes and 50% reduction. The fracture surface has a large number of dimples, and the dimples have a certain directionality, indicating that the grains are elongated and refined along the rolling direction. The alloy still exhibits ductile fracture, with a fracture elongation of 33%, which is higher than that of copper-magnesium alloy rolled with 8 passes and 50% reduction.

[0078] like Figure 1 The figure shows a room temperature metallographic image of the as-cast Cu-Mg-Sc alloy obtained in this embodiment. As can be seen from the figure, the as-cast sample has coarse grains with a grain size of about several hundred micrometers.

[0079] like Figure 10 The image shows the Cu4Sc precipitate and mapping diagram obtained by TEM observation of the ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material in this embodiment. It can be seen that Mg is uniformly distributed in the alloy, indicating that Mg is dissolved in the copper matrix and plays a solid solution strengthening role, while Sc is partially dissolved in the matrix and partially precipitated to form nanoparticles distributed in the matrix. Figure 11 The high-resolution image and diffraction calibration diagram of the Cu4Sc precipitate in this embodiment, observed by TEM, show that some Sc in the Cu-Mg-Sc alloy of this embodiment precipitates in the form of Cu4Sc, which is diffusely distributed in the copper matrix and has a size of about 5 nm. Figure 12 This is a diagram of the dislocation structure observed by TEM in this embodiment. Figure 13 This is a TEM image of the twin structure of this embodiment. The nanotwins obtained in this embodiment are face-centered cubic copper twins. Figure 14 This is a TEM image showing the overall grain morphology distribution of this embodiment. The width of the lath-shaped grains obtained in this embodiment is approximately 100-200 nm. Example 5

[0080] A method for preparing an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material. The preparation and processing methods in this embodiment are as follows:

[0081] (1) Using oxygen-free copper, magnesium blocks with a purity of 99.99% and magnesium-scandium master alloy as raw materials, the proportion of copper alloy material is 0.1wt% Mg and 0.04wt% Sc, with the balance being copper.

[0082] (2) Vacuum induction casting: First, put the 99.99% copper rod into the crucible, then evacuate to 500Pa, heat with 20kW power for 10min, raise the temperature to 800℃, stop evacuating and fill with a protective atmosphere of 99.99% argon, raise the power to 35kW to completely melt the copper, then add 99.99% magnesium blocks and magnesium scandium intermediate alloy, and after all the newly added alloy elements have melted, perform heat preservation treatment at 1250℃ for 8 minutes, then cast the copper alloy ingot. Before casting, preheat the mold.

[0083] (3) The Cu-Mg-Sc copper alloy ingot was cut into 19.5*19.5*45mm square columnar specimens using an electrical discharge wire cutting machine. The specimens were then cleaned, dried, polished, and solution treated. The solution treatment temperature was 880℃, and the solution treatment time was 1.5h. After the solution treatment, the specimens were immediately placed in clean water for water quenching. Graphite lubricant was then applied to the surface of the specimens and the mold. The mold was preheated in a muffle furnace for 60min, and then the specimens were placed in the mold for another 30min of preheating. The preheating temperature was 400℃. The specimens were then subjected to equal channel corner extrusion for 12 passes at a speed of 20mm / min, with a 90° rotation between adjacent passes. The specimens were held at 350℃ for 20min after every four passes. After extrusion, the specimens were water-cooled to prevent grain growth.

[0084] (4) Room temperature rolling: The specimen obtained in step (3) of this embodiment is cut into sheet specimens by wire cutting machine, and then the cut sheet specimens are cleaned and polished. Then, room temperature rolling is performed using ZK-WS1C type rolling mill with a reduction of 95%, and unidirectional double-sided rolling is performed with a single reduction of 4%. Example 6

[0085] A method for preparing an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material. The preparation and processing methods in this embodiment are as follows:

[0086] (1) Using oxygen-free copper, magnesium blocks with a purity of 99.99% and magnesium-scandium master alloy as raw materials, the proportion of copper alloy material is 0.6wt% Mg and 0.1wt% Sc, with the balance being copper.

[0087] (2) Vacuum induction casting: First, put the 99.99% copper rod into the crucible, then evacuate to 500Pa, heat with 20kW power for 10min, raise the temperature to 900℃, stop evacuating and fill with a protective atmosphere of 99.99% argon, raise the power to 35kW to completely melt the copper, then add 99.99% magnesium blocks and magnesium scandium intermediate alloy, and after all the newly added alloy elements have melted, perform heat preservation treatment at 1220℃ for 6 minutes, and then cast the copper alloy ingot. Before casting, preheat the mold.

[0088] (3) The Cu-Mg-Sc copper alloy ingot was cut into 19.5*19.5*45mm square columnar specimens using an electrical discharge wire cutting machine. The specimens were then cleaned, dried, polished, and solution treated. The solution temperature was 865℃, and the solution time was 1.2h. After the solution treatment, the specimens were immediately placed in clean water for water quenching. Graphite lubricant was then applied to the surface of the specimens and the mold. The mold was preheated in a muffle furnace for 50min, and then the specimens were placed in the molds for another 25min of preheating. The preheating temperature was 380℃. The specimens were then subjected to equal channel corner extrusion for 12 passes at a speed of 18mm / min, with a 90° rotation between adjacent passes. The specimens were held at 380℃ for 15min every four passes. After extrusion, the specimens were water-cooled to prevent grain growth.

[0089] (4) Room temperature rolling: The specimen obtained in step (3) of this embodiment is cut into sheet specimens by wire cutting machine, and then the cut sheet specimens are cleaned and polished. Then, room temperature rolling is performed using ZK-WS1C type rolling mill with a reduction of 70%, and unidirectional double-sided rolling is performed with a single reduction of 7%. Example 7

[0090] The only difference between this embodiment and embodiment 6 is that:

[0091] The composition of the copper alloy material is: 0.4wt% Mg and 0.02wt% Sc, with the balance being copper.

[0092] The mechanical property data of the ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy materials obtained in Examples 1 to 4 are shown in Table 1 below.

[0093] Table 1 Mechanical Properties

[0094]

[0095] Table 1 leads to the following conclusions: Simply adding Sc to copper-magnesium alloys does not yield nano-precipitates and high performance; the strength of the as-cast Cu-Mg-Sc alloy is only around 200 MPa. To achieve the target performance, alloy composition design and combined processing techniques are necessary. Examples 1 and 3, which did not undergo rolling, resulted in alloys with relatively low strength. Only the copper-magnesium-scandium material of this invention, processed through a combination of equal-channel angular extrusion and rolling, controls the microstructure to improve its strength and toughness, resulting in a copper-magnesium alloy with a good balance of strength, toughness, and high-temperature performance. Furthermore, it maintains relatively stable conductivity to enhance the overall performance of the material, achieving high strength, high conductivity, and heat resistance. Ultimately, a copper-magnesium alloy with a good balance of strength, plasticity, and high-temperature performance is obtained.

[0096] It should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the invention, features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof in the above description of exemplary embodiments of the invention. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in fewer than all the features of the foregoingly disclosed embodiments. Therefore, the claims, following the detailed description, are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0097] Although the invention has been described with reference to a limited number of embodiments, those skilled in the art will understand from the foregoing description that other embodiments are conceivable within the scope of the invention described herein. Furthermore, it should be noted that the language used in this specification has been chosen primarily for readability and instructional purposes, and not for the purpose of interpreting or limiting the subject matter of the invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the invention is illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

[0098] 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 method for preparing an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material, characterized in that, The alloy composition, by mass fraction, is: Mg: 0.1-0.6%; Sc: 0.02-0.10%; the balance is copper and other unavoidable impurities; The preparation method includes the following steps: S1: Vacuum Induction Casting: According to the composition of the copper alloy material, the raw materials are prepared. First, the high-purity upward copper rod is placed in the crucible, and then the vacuum is drawn to at least 500 Pa. The material is heated at a power of at least 20 kW for at least 10 minutes, and the temperature is raised to 800℃~900℃. The vacuum is stopped and a protective atmosphere is introduced. The power is increased to completely melt the upward copper rod. Then, high-purity magnesium blocks and magnesium-scandium master alloys are added. After the magnesium blocks and magnesium-scandium master alloys are completely melted, the material is held at a temperature of 1200-1250℃ for 5-8 minutes. After that, the copper alloy material ingot is cast to obtain the Cu-Mg-Sc copper alloy ingot. S2: Pre-treatment and equal channel corner extrusion processing: The Cu-Mg-Sc copper alloy ingot was cut into square columnar specimens, and then the square columnar specimens were cleaned, dried and polished. Then the square columnar specimens were solution treated and water cooled. The square columnar specimen and the mold are then preheated. The square columnar specimen is then subjected to equal channel corner extrusion processing with 8-12 extrusion passes at a speed of 15-20 mm / min. The molds of adjacent passes are rotated 90°. The specimen and the mold are kept warm every 4 passes at a temperature of 350-400℃ for 10-20 minutes. After extrusion, the specimen is water-cooled. S3: Room temperature rolling: The specimen obtained in S2 is cut into slices by wire cutting. The sliced ​​specimens are cleaned and polished. The processed sliced ​​specimens are then rolled at room temperature with a rolling reduction of 50-95%. The rolling direction is unidirectional double-sided rolling, and the single reduction is 4-10%.

2. The method for preparing an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material according to claim 1, characterized in that, In S1, the protective atmosphere is 99.99% argon.

3. The method for preparing an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material according to claim 1, characterized in that, In S1, the purity of the high-purity upward-drawing copper rod and the high-purity magnesium block is at least 99.99%.

4. The method for preparing an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material according to claim 1, characterized in that, In S2, the cleaning, drying, and polishing process includes ultrasonic cleaning, drying, and polishing of the specimen with 1000# silicon carbide sandpaper.

5. The method for preparing an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material according to claim 1, characterized in that, In S2, the solution temperature is 850-880℃, the solution time is 1-1.5h, and immediately after the solution is dissolved, it is placed in clean water for water quenching.

6. The method for preparing an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material according to claim 1, characterized in that, In S2, before preheating the cubic columnar specimen and the mold, graphite lubricant is applied to the mold and the cubic columnar specimen; then the mold is placed in a muffle furnace for preheating for 40-60 minutes, and then the cubic columnar specimen is placed in the mold for preheating for another 20-30 minutes. The preheating temperature is 350-400℃.

7. The method for preparing an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material according to claim 1, characterized in that, In S3, the cleaning and polishing process includes ultrasonic cleaning and drying, followed by polishing with silicon carbide sandpaper to remove surface dirt and oxide layers.

8. The application of the ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material obtained by the preparation method according to claim 1 in high-temperature and high-conductivity applications, characterized in that... Materials used in high-temperature and high-conductivity applications include railway tram contact wires, aerospace wires, and connectors for new energy vehicles.

9. A railway tram contact wire, characterized in that, The method described in claim 1 yields an ultrafine-grained, high-strength, high-conductivity, and high-heat-resistant Cu-Mg-Sc copper alloy material.

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