Copper graphene composite material and preparation method thereof

Abstract

The invention discloses a copper-graphene composite material and a preparation method thereof.The composite material comprises a copper matrix and graphene serving as a reinforcing phase, the graphene is dispersed and distributed at the grain boundary of the copper matrix and in the grain boundary, and the graphene at the grain boundary is of a three-dimensional network structure and wraps the copper matrix; in the cross section of the composite material, the sum of the lengths of the graphene horizontally oriented in the crystal boundary accounts for 60% or above of the sum of the lengths of all the graphene in the crystal boundary, and the variable coefficient of the grain size of the copper matrix is smaller than or equal to 30%. The composite material has excellent strength, corrosion resistance, high-temperature oxidation resistance and intrinsic conductivity, the tensile strength of the composite material is larger than or equal to 280 MPa, the conductivity of the composite material is larger than or equal to 95% IACS, the thickness of an oxidation layer obtained after 180 DEG C / 100 h high-temperature oxidation is smaller than or equal to 20 micrometers, and the local pitting corrosion area rate obtained after 1000 h salt spray test is smaller than 10%. The composite material is excellent in comprehensive performance and low in manufacturing cost, has a good industrialization prospect, and can meet the key requirements of the electronic and electrical industry on high-conductivity, high-temperature stability and long-life conductors.

Description

TECHNICAL FIELD

[0001] The present application relates to a copper-based composite material, in particular to a copper-graphene composite material and a preparation method thereof. BACKGROUND

[0002] Copper is widely used in electronic devices, power transmission and wear-resistant components due to its excellent electrical conductivity (58 MS / m) and thermal conductivity (400 W / (m·K)). However, pure copper has low strength and poor corrosion resistance, especially in environments containing sulfur or salt. In addition, copper is easily oxidized during use, and the formed oxide layer can significantly reduce its electrical conductivity, which seriously restricts its application in high-end fields.

[0003] In the prior art, metal elements, ceramic particles (such as Al2O3, SiC) or carbon materials (such as carbon nanotubes, graphite) are usually added as reinforcing phases to improve the strength and corrosion resistance of the copper matrix. However, the above methods have the following defects: the introduction of reinforcing phases can cause a serious decrease in electrical conductivity; the interface between the reinforcing phase and copper is prone to peeling, forming micro-crack sources and limiting the further improvement of the mechanical properties of the material; in addition, when the reinforcing phase is not uniformly dispersed, the galvanic corrosion of the copper matrix is accelerated, which damages the corrosion resistance.

[0004] Graphene has become an ideal reinforcing phase for improving the comprehensive performance of copper-based composite materials due to its ultra-high strength (130 GPa), intrinsic high electrical conductivity (100 MS / m) and excellent chemical inertness, which is particularly helpful in achieving high strength and high electrical conductivity. However, the actual strengthening effect of graphene on copper-based composite materials is far from the theoretical expectation. In addition, existing researches mainly focus on preparation process technology, and there is little systematic study on the microstructure of the composite material. There are the following significant challenges: 1) the fragmentation and poor continuity of graphene in copper-based composite materials lead to increased electron scattering, oxidation and corrosion of the composite material; 2) the aggregation of graphene in copper-based composite materials is serious, and the distribution is severely disordered, which is not conducive to the improvement of the comprehensive performance of the composite material; 3) there is a lack of microstructure research on copper matrix, and there is a lack of correlation analysis between microstructure and comprehensive performance; 4) the preparation technology of copper-graphene composite materials has poor repeatability, high cost and complex process, which is difficult to meet the large-scale production demand.

[0005] Therefore, it is necessary to systematically study the strengthening mechanism of the microstructure of copper-graphene composite materials and develop a new type of copper-graphene composite material and a preparation method thereof. Under the premise of maintaining excellent electrical conductivity, the material can achieve high strength, significantly improved corrosion resistance and high-temperature oxidation resistance. SUMMARY

[0006] The technical problems to be solved by the present application are that, in view of the deficiencies of the prior art, a copper graphene composite material and a preparation method thereof are provided, the copper graphene composite material has excellent strength, corrosion resistance, high-temperature oxidation resistance and intrinsic conductivity, has excellent comprehensive performance, has low manufacturing cost, has good industrialization prospect, and can meet the key requirements of the electronic and electrical industry for high-conductivity, high-temperature stability and long-life conductors.

[0007] The technical scheme adopted by the present application to solve the above technical problems is: a copper graphene composite material, comprising a copper matrix and graphene as a reinforcing phase, the graphene in the composite material is dispersedly distributed at the grain boundaries and in the grain boundaries of the copper matrix, the graphene at the grain boundaries is in a three-dimensional network structure and coats the copper matrix; in the cross section of the composite material, the total length of the horizontally oriented graphene in the grain boundaries accounts for more than 60% of the total length of all the graphene in the grain boundaries, and the coefficient of variation (i.e., CV) of the grain size of the copper matrix is ≤30%.

[0008] The copper graphene composite material of the present application comprises a copper matrix and graphene as a reinforcing phase, wherein the copper matrix comprises copper and unavoidable impurities, and the content of the unavoidable impurities in the copper matrix is not higher than 0.5wt%. The graphene in the copper graphene composite material of the present application is dispersedly distributed at the grain boundaries and in the grain boundaries of the copper matrix, and the graphene at the grain boundaries is in a three-dimensional network structure and coats the copper matrix, thereby maximally improving the comprehensive performance of the composite material through the following mechanisms:

[0009] (1) The graphene at the grain boundaries pins the grain boundaries, and the graphene in the grain boundaries inhibits the coarsening and non-uniformity of the grains during high-temperature and deformation processes, in addition, during the loading process, the graphene distributed at the grain boundaries and in the grain boundaries effectively transfers the load from the copper matrix to the high-strength graphene, and utilizes the high intrinsic strength and large specific surface area of the graphene to hinder dislocation movement, thereby significantly improving the tensile strength;

[0010] (2) The graphene at the grain boundaries and in the grain boundaries synergistically blocks the diffusion paths of corrosion media such as H2O, Cl - , O2, and at the same time, the graphene can inhibit the oxidation-reduction reaction of the copper matrix due to its chemical inertness and high-temperature stability, and the three-dimensional continuous graphene coating layer at the grain boundaries can also effectively isolate oxygen permeation, thereby improving the high-temperature oxidation resistance of the composite material;

[0011] (3) The three-dimensional network graphene at the grain boundaries and the graphene inside the grains jointly construct low-scattering electron transmission channels, thereby providing a guarantee for the improvement of the conductivity of the composite material.

[0012] In the cross-sectional microstructure of the copper-graphene composite material of this invention, the graphene within the grain boundaries tends to be ordered, with the total length of horizontally oriented graphene accounting for more than 60% of the total length of all graphene within the grain boundaries. On the one hand, the horizontal orientation of the graphene within the grain boundaries forms low-resistance electron channels, greatly reducing electron scattering losses and bringing the conductivity close to the theoretical value. On the other hand, the horizontally oriented graphene layers are perpendicular to the dislocation propagation direction, forcing dislocations to significantly bypass or cut around the edges, doubling the resistance of graphene to dislocations compared to randomly oriented graphene, further improving the strength of the composite material. In addition, the horizontally oriented graphene further shields corrosion factors, further enhancing the corrosion resistance of the composite material.

[0013] This invention, by controlling the coefficient of variation of the copper matrix grain size in the cross-section of the copper-graphene composite material to ≤30%, ensures a synergistic improvement in the overall performance of the composite material. It overcomes the bottleneck of the mutual exclusion between strength and conductivity in traditional copper-based composite materials, significantly improving its overall performance while maintaining the intrinsic conductivity of copper. First, grain size homogenization ensures low scattering transmission of electrons within continuous and uniform grains, resulting in more stable electron transport and improved conductivity. Second, grain size homogenization promotes the formation of a dense passivation film, which helps reduce the corrosion current density of the composite material, improving it by several orders of magnitude compared to non-uniform structures (CV > 30%). Third, uniform grain size enables high coverage of graphene sheets and forms a low-defect oxygen diffusion barrier, further improving the high-temperature oxidation resistance of the composite material. Additionally, uniform grain size improves the material's deformation coordination, significantly reduces stress concentration, delays crack initiation, and further enhances the tensile strength of the composite material.

[0014] Preferably, in the cross-section of the copper-graphene composite material of the present invention, the total length of graphene within the grain boundaries accounts for 20-50% of the total length of all graphene. Apart from the graphene within the grain boundaries, the remaining graphene is distributed at the grain boundaries to form a three-dimensional continuous network (i.e., a three-dimensional mesh structure). When the total length of graphene within the grain boundaries accounts for 20-50% of the total length of all graphene in the cross-section of the copper-graphene composite material of the present invention, on the one hand, it ensures the formation of a continuous dislocation blocking network within the grain boundaries, significantly improving material strength without blocking electron migration; on the other hand, the graphene within the grain boundaries forms a nanoscale shielding layer, synergistically constructing a dual protection system with the graphene at the grain boundaries, greatly suppressing dielectric penetration and high-temperature oxygen diffusion. When the total length of graphene within the grain boundaries accounts for less than 20% of the total length of all graphene, there are insufficient dislocation bypass paths, resulting in grain coarsening and weakened strength. When the total length of graphene within the grain boundaries accounts for more than 50% of the total length of all graphene, excessive graphene will disrupt the continuity of the copper matrix, leading to severe electron scattering and making it difficult to maintain high conductivity.

[0015] Preferably, the copper-graphene composite material of the present invention has 1 to 10 graphene layers, wherein the total length of graphene layers with 1 to 5 layers accounts for more than 70% of the total length of all graphene layers. When the number of graphene layers exceeds 10, the intensity ratio of the D peak to the G peak in the Raman spectrum (I D / I G (Exceeding 0.5, sp) 3 Increased defect content leads to a sharp drop in the intrinsic conductivity of copper. Furthermore, graphene with more than 10 layers has a high defect rate, reducing interfacial bonding with the copper matrix, decreasing load transfer efficiency and dislocation hindering effect, thus reducing the strength of the composite material. Interlayer stacking defects become channels for corrosive media penetration, and these defects accelerate copper-based corrosion and high-temperature oxidation. Maintaining a proportion of 1–5 layers of thin graphene is key to further achieving "conductivity-strengthening." 1–5 layer graphene possesses ultra-high intrinsic conductivity and low boundary scattering characteristics; when its proportion is ≥70%, the conductivity of the composite material can exceed that of pure copper. 1–5 layer thin graphene forms a semi-coherent interface with the copper matrix, with significantly higher interfacial bonding than thicker graphene with more than 5 layers, improving load transfer efficiency. In addition, the reduced wrinkle rate of 1–5 layer thin graphene helps avoid early cracking caused by stress concentration.

[0016] Preferably, the average grain boundary curvature radius R of the copper-graphene composite material of this invention is ≥100μm. The advantages of an average grain boundary curvature radius R ≥100μm are: 1) It facilitates highly straight grain boundaries, placing them in a low-energy state, eliminating stress concentration, increasing crack initiation resistance, and further enhancing the tensile strength of the material; 2) It reduces the corrosion current density of the material and lowers the interfacial energy, improving both the adsorption resistance of the corrosive liquid and the adhesion of the oxide film, thereby further improving the material's corrosion resistance and oxygen diffusion barrier; 3) It reduces the interfacial scattering resistance and increases electron migration efficiency, thereby further improving the material's conductivity. However, when the average grain boundary curvature radius R <100μm, the following situations occur: stress concentration is caused, inducing microcracks and reducing the material's strength; interfacial electron scattering is intensified, limiting the improvement of the material's conductivity; the grain boundary energy barrier decreases, the oxygen diffusion rate increases, the corrosion area increases, and the oxide layer thickens at high temperatures.

[0017] The copper-graphene composite material of this invention has a tensile strength ≥280MPa, conductivity ≥95%IACS, oxide layer thickness ≤20μm after high-temperature oxidation at 180℃ / 100h, and local pitting corrosion area ratio <10% after 1000h salt spray test.

[0018] The preparation method of the copper-graphene composite material of the present invention includes the following steps: preparing copper-graphene composite powder → high-temperature repair → rotary extrusion → continuous extrusion → cold deformation → annealing. Before and after the above main processes, rolling, annealing, stretching, and other processes can be performed as needed to process the copper-graphene composite material into different sizes and shapes, such as wires and strips. The specific preparation method steps are as follows:

[0019] (1) Preparation of copper-graphene composite powder: The copper-graphene composite powder used in this invention can be obtained by using copper powder as raw material, depositing graphene on the surface of copper powder by chemical vapor deposition, or by mixing copper powder and graphene powder evenly by mechanical mixing.

[0020] (2) High-Temperature Repair: The copper-graphene composite powder is heat-treated at 300–1000℃ in an atmosphere (e.g., at least one gas selected from Ar, H2, CH4, and N2) or in a vacuum for 20–240 min to complete the high-temperature repair of graphene. This process repairs the graphene structure in the composite powder and optimizes the copper-based microstructure, further improving the quality and coverage of graphene, and promoting the formation of a three-dimensional interpenetrating network structure at the grain boundaries. In addition, during the high-temperature repair process, graphene can inhibit the coarsening of copper grains and form a uniform structure. The quality of the repaired graphene structure must meet the requirement that the peak intensity ratio of the D peak to the G peak in the Raman spectrum (I0.05) is within the acceptable range. D / I G )≤0.5. If the I of graphene in the composite powder D / I G A defect density greater than 0.5 leads to an increase in graphene structural defects in copper-graphene composites, significantly reducing the improvement effect on the overall performance of the composite material. Therefore, this invention lays an atomic-level foundation for subsequent enhancement of the composite material's strength, conductivity, high-temperature oxidation resistance, and corrosion resistance by suppressing the defect density of graphene.

[0021] (3) Rotary extrusion: The copper-graphene composite powder after high-temperature repair is subjected to rotary friction extrusion at 100–500℃ in a protective atmosphere, with an extrusion rate of 50–400 mm / min. This parameter combination synergistically achieves two core breakthroughs: First, graphene is further uniformly dispersed. The high shear rheological field effectively reduces the number of graphene layers, improving the uniformity of dispersion of fewer-layer graphene. Furthermore, the axial extrusion force and axial shear force are coupled, driving the straightening of grain boundaries and the directional alignment of graphene along the extrusion direction. Second, continuous plastic deformation eliminates interfacial micropores, reducing porosity and crack initiation energy. If the extrusion temperature is higher than 500℃, during the deformation process, the sp... 2The bonds are easily damaged, which reduces the quality of graphene and results in poor reinforcement of composite materials, especially a sharp drop in conductivity. If the extrusion speed is too low, the extrusion efficiency will be too low, and the composite material will be easily oxidized by long-term high-temperature extrusion. If the speed is too high, the strain will be uneven, the graphene dispersion effect will be poor, and there will be a risk of damaging the graphene structure.

[0022] (4) Continuous Extrusion: This invention employs continuous extrusion processing on copper-graphene composite materials. Before continuous extrusion, the surface of the copper-graphene composite material is peeled or acid-washed to remove surface impurities and oxides, preventing their negative effects. The preheating temperature of the die cavity for continuous extrusion is 300–700℃, and the extrusion speed is 4–20 rpm. This parameter range achieves further densification of the composite material while avoiding damage to the graphene structure. Compared to conventional extrusion, the multidimensional shear force field generated by continuous extrusion can achieve dual synergistic optimization: firstly, it promotes the dynamic recrystallization process, reducing the grain size variation coefficient of the composite material; secondly, it enhances the phase distribution optimization, improving the spatial distribution uniformity of graphene through strong shear dispersion effect, effectively eliminating interfacial porosity and agglomeration defects, and promoting grain boundary straightening and graphene directional alignment. The above dual synergistic optimization significantly improves the overall performance of the copper-graphene composite material.

[0023] (5) Cold deformation: The present invention reduces the diameter of the copper graphene composite material to the required size through multiple cold deformations. If necessary, the surface is peeled or pickled before cold deformation. The processing rate of cold deformation is 5-30%. The processing rate should not be too high during the cold deformation process, otherwise the composite material is prone to cracking or even breaking, which is not conducive to the improvement of performance.

[0024] (6) Annealing treatment: The annealing temperature of this invention is 300-600℃, and the annealing time is 60-240 min. This invention further homogenizes the microstructure and eliminates defects by annealing under a protective atmosphere, thereby further improving the comprehensive performance of the copper-graphene composite material.

[0025] Compared with existing technologies, this invention has the following advantages: By controlling the distribution and structure of graphene in the copper-graphene composite material, and simultaneously controlling the proportion of graphene orientation within the grain boundaries and the grain size variation coefficient in the cross-section of the composite material, this invention enables the copper-graphene composite material to possess excellent strength, corrosion resistance, and high-temperature oxidation resistance while maintaining the excellent intrinsic conductivity of copper. The copper-graphene composite material of this invention combines excellent strength, corrosion resistance, high-temperature oxidation resistance, and intrinsic conductivity, with a tensile strength ≥280MPa, conductivity ≥95% IACS, oxide layer thickness ≤20μm after 180℃ / 100h high-temperature oxidation, and local pitting corrosion area ratio <10% after 1000h salt spray test. The copper-graphene composite material of this invention exhibits excellent comprehensive performance, low manufacturing cost, and good industrialization prospects, meeting the key requirements of the electronics and electrical industry for high conductivity, high-temperature stability, and long-life conductors. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the cross-section of the copper-graphene composite material of the present invention. Detailed Implementation

[0027] The following selection of 10 examples and 2 comparative examples of copper-graphene composite materials provides a clear and complete description of the technical solution of the present invention.

[0028] Taking the preparation of copper-graphene composite wires as an example, the preparation process of copper-graphene composite wires in 10 embodiments is as follows: preparing copper-graphene composite powder → high-temperature repair → rotary extrusion → continuous extrusion → cold deformation → annealing treatment. The key process parameters are controlled as shown in Table 1. The specific preparation method includes the following steps:

[0029] (1) Preparation of copper-graphene composite powder: Graphene was deposited on the surface of copper powder by chemical vapor deposition to prepare copper-graphene composite powder.

[0030] (2) High-temperature repair: The copper-graphene composite powder was kept at a protective atmosphere of 300–1000℃ for 20–240 min to repair the graphene at high temperature. Raman spectroscopy was used to detect that the ratio of the D peak intensity to the G peak intensity in the graphene after high-temperature repair met the following condition: D / I G ≤0.5;

[0031] (3) Rotary extrusion: The copper graphene composite powder after high temperature repair is filled into a pure copper container, and rotary friction extrusion is carried out at a temperature of 100-500℃ in a protective atmosphere to obtain copper graphene composite rods. The extrusion is carried out for 20-200 min before extrusion, and the extrusion rate is 50-400 mm / min.

[0032] (4) Continuous extrusion: Before continuous extrusion, the copper graphene composite rod is peeled to remove surface impurities and oxides; then the copper graphene composite rod is continuously extruded. The key process parameters are controlled as follows: the preheating temperature of the mold cavity is 300-700℃, and the extrusion speed is 4-20rpm to obtain copper graphene composite wire.

[0033] (5) Cold deformation: The copper graphene composite wire is subjected to multiple cold deformations to reduce the diameter of the copper graphene composite wire to the required size. The processing rate of cold deformation is 5-30%. If necessary, the copper graphene composite wire is pickled between multiple cold deformations to remove surface impurities and oxides.

[0034] (6) Annealing treatment: The copper graphene composite wire obtained by cold deformation is annealed under a protective atmosphere. The annealing temperature is 300-600℃ and the annealing time is 60-240min. The protective atmosphere is nitrogen.

[0035] The difference between the preparation methods of the two comparative copper-graphene composite wires and the copper-graphene composite wires of the above 10 embodiments is that there is no high-temperature repair step in comparative example 1 and no rotational extrusion step in comparative example 2.

[0036] The performance and microstructure of the copper-graphene composite wire samples of Examples 1-10 and Comparative Examples 1-2 of this invention were tested according to the methods specified in relevant national and industry standards. The percentage of the total length of graphene within grain boundaries to the total length of all graphene, and the percentage of the total length of horizontally oriented graphene within grain boundaries to the total length of all graphene within grain boundaries, were obtained from statistical data of SEM images of the cross-section of the copper-graphene composite material. The percentage of the total length of graphene with 1-5 layers to the total length of all graphene was obtained from statistical data of TEM images of the copper-graphene composite material. The specific testing methods are as follows:

[0037] The tensile strength was tested on an electronic universal mechanical testing machine in accordance with GB / T 228.1-2021 Metallic materials, tensile testing - Part 1: Test method at room temperature, with a tensile speed of 5 mm / min.

[0038] Conductivity was tested using the Bridge method, according to GB / T351-2019 "Method for Measurement of Resistivity of Metallic Materials". The test sample wire / strip length was ≥200mm. First, the resistance was measured at least three times at different directions and positions of the sample, and the average value was taken as the resistance value of the sample. Then, the wire diameter / strip thickness was measured using a micrometer and laser measuring instrument. The dimensions of each sample were measured at least five different positions, and the average value was calculated as the wire diameter / strip thickness of the sample. The conductivity was calculated based on the wire diameter / strip thickness, resistance, and length of the composite material.

[0039] The corrosion resistance test was conducted according to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test". A salt spray test was carried out for 1000 hours in an atmosphere with a pH value of 6.5 to 7.2. The corroded samples were then observed by scanning electron microscopy, and the ratio of the corroded area to the total observed area was counted as the local pitting corrosion area rate after 1000 hours of salt spray test.

[0040] The high-temperature antioxidant test involves placing the sample on a heating stage (in air) at 180℃ for 100 hours. At least three samples are selected. After heating, the cross-section of the sample is observed using a scanning electron microscope and the thickness of the oxide layer is measured. The average thickness of the oxide layer of all samples is calculated as the oxide layer thickness after high-temperature oxidation at 180℃ / 100h.

[0041] Microstructural observation: At least five fields of view were randomly scanned using an optical microscope. Based on the results, the number of grains was counted, and the equivalent diameter d of the grains was extracted. i Therefore, the average grain size d is calculated, and the standard deviation of the grain size σ is calculated. d Then, according to the formula CV = σ d The coefficient of variation for grain size was calculated as / d×100%. Cross-sections were observed using a scanning electron microscope to examine the dispersed distribution of graphene sheets at and within grain boundaries, and the proportion of the total length of graphene located within grain boundaries to the total length of all graphene was calculated. Simultaneously, the ratio of the total length of horizontally oriented graphene (i.e., orientation angle ≤10° in the extrusion direction) within grain boundaries to the total length of all graphene within the grain boundaries was calculated. The number of graphene layers was observed using a transmission electron microscope, and the ratio of the total length of graphene layers 1–5 to the total length of all graphene was calculated.

[0042] The average grain boundary curvature radius R is calculated by observing the sample with a metallographic microscope, randomly selecting at least 20 positions from the grain boundaries of the sample, and calculating the grain boundary curvature radius at each position according to the three-point circle method, and then calculating the average grain boundary curvature radius R (μm).

[0043] The structural quality of graphene was characterized by laser Raman spectroscopy surface scanning. At an excitation wavelength of 532 nm, the intensity ratio I of the D peak to the G peak at all measurement points within the field of view was statistically analyzed. D / I G .

[0044] Figure 1 This is a schematic diagram of the cross-section of the copper-graphene composite material of the present invention. Figure 1 The dashed lines represent grain boundaries without graphene, while the graphene at and within the grain boundaries is represented by solid lines.

[0045] Table 1

[0046]

[0047]

[0048] Table 2

[0049]

[0050] In Table 2, A represents the ratio (%) of the total length of graphene with 1 to 5 layers to the total length of all graphene; B represents the ratio (%) of the total length of graphene within the grain boundaries to the total length of all graphene; and C represents the ratio (%) of the total length of horizontally oriented graphene within the grain boundaries to the total length of all graphene within the grain boundaries.

Claims

1. A copper-graphene composite material, comprising a copper matrix and graphene as a reinforcing phase, characterized in that, In this composite material, graphene is dispersed at and within the grain boundaries of the copper matrix. The graphene at the grain boundaries forms a three-dimensional network structure that coats the copper matrix. In the cross-section of this composite material, the total length of the horizontally oriented graphene within the grain boundaries accounts for more than 60% of the total length of all graphene within the grain boundaries, and the coefficient of variation of the grain size of the copper matrix is ​​≤30%.

2. The copper-graphene composite material according to claim 1, characterized in that, In the cross-section of this composite material, the total length of graphene within the grain boundaries accounts for 20-50% of the total length of all graphene.

3. The copper-graphene composite material according to claim 1, characterized in that, The graphene in this composite material has 1 to 10 layers, of which the total length of graphene with 1 to 5 layers accounts for more than 70% of the total length of all graphene.

4. The copper-graphene composite material according to claim 1, characterized in that, The average grain boundary curvature radius R of the composite material is ≥100μm.

5. The copper-graphene composite material according to claim 1, characterized in that, The composite material has a tensile strength ≥280MPa, conductivity ≥95%IACS, oxide layer thickness ≤20μm after high-temperature oxidation at 180℃ / 100h, and local pitting corrosion area ratio <10% after 1000h salt spray test.

6. A method for preparing the copper-graphene composite material according to any one of claims 1 to 5, characterized in that, The process includes the following steps: preparing copper-graphene composite powder → high-temperature repair → rotary extrusion → continuous extrusion → cold deformation → annealing.

7. The method for preparing the copper-graphene composite material according to claim 6, characterized in that, I of graphene after high temperature repair D / I G The ratio is ≤0.

5.

8. The method for preparing the copper-graphene composite material according to claim 6, characterized in that, The temperature for high-temperature repair is 300–1000℃, and the time is 20–240 minutes.

9. The method for preparing the copper-graphene composite material according to claim 6, characterized in that, The temperature of the rotary extrusion is 100–500℃, and the extrusion rate is 50–400 mm / min.

10. The method for preparing the copper-graphene composite material according to claim 6, characterized in that, The preheating temperature of the die cavity for continuous extrusion is 300–700℃, and the extrusion speed is 4–20 rpm.

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