Copper-aluminum composite material, preparation method thereof and cable cell

Abstract

The invention belongs to the technical field of high-voltage cable cells, and provides a copper-aluminum composite material and a preparation method thereof and a cable cell, the material is of a double-layer structure and comprises an inner core and a shell wrapping the outer surface of the inner core, and the shell is a copper strip; the inner core is of a fan-shaped topological structure and comprises a plurality of rare earth composite copper-aluminum alloy matrixes, and raw materials of the rare earth composite copper-aluminum alloy matrixes comprise copper powder, aluminum powder, nanometer aluminum oxide, a cerium source, a magnesium source and nanometer graphene, and the rare earth composite copper-aluminum alloy matrixes are prepared through a distributed mechanical alloying process and multiple times of ball milling. According to the invention, the temperature resistance, creep resistance and arc resistance of the copper-aluminum composite material can be effectively improved, so that the copper-aluminum composite material can bear severe environment performance requirements such as high temperature higher than 150 DEG C when being used as a cable cell for transmitting electric energy, and the requirement of improving the electric energy transmission rate in a high-safety scene of a new energy automobile can be met.

Description

Technical Field

[0001] The present application relates to the technical field of high-voltage cable cores, and in particular to a copper-aluminum composite material, a preparation method thereof, and a cable core. Background Art

[0002] With the rapid development of the new energy vehicle industry, the industry has placed extremely stringent requirements on the core materials of high-voltage cables used in new energy vehicles to ensure the charging rate and power transmission capacity in high-safety scenarios. Currently, the high-voltage cables used in new energy vehicles mainly use pure copper, oxygen-free copper or tinned copper, etc., which are made of multiple strands of copper wire woven into a circular shape as the core material. They have good electrical conductivity and are widely used in the industry. However, this core material also has some objective disadvantages, such as:

[0003] 1. Poor high-temperature stability: The cables are close to components such as motors and batteries. The temperature resistance level of the battery cell materials does not meet the requirements (for example, below 125°C). When the battery cell materials are exposed to high temperatures above 150°C for a long time, the battery cells are prone to aging and deterioration when powered on, resulting in increased resistivity and exacerbated temperature rise. In addition, some battery cell materials have poor stress cracking resistance and are prone to longitudinal cracking or thermal shock failure under the combined action of high temperature and mechanical stress.

[0004] 2. Low electrical conductivity: The electrical conductivity of lightweight battery core materials is only 60% of that of copper. Under the same current, the resistance of the battery core material is greater, resulting in increased heat generation and further reduced conductivity. The resistivity of aluminum (2.65×10 -8 Ω·m) is about 1.68 times that of copper. By pressing copper plates and aluminum plates to form a copper-aluminum composite matrix material, it is a way to prepare a new material for high-voltage cables. This copper-aluminum composite matrix material uses aluminum as the main matrix. The high resistance of aluminum directly leads to a decrease in the conductivity of the entire composite matrix material.

[0005] 3. Poor material interface strength: The copper-aluminum composite matrix material has poor interface strength under the conditions of long-term power transmission, high temperature working environment and long-term vibration due to the thermal expansion coefficient of copper (16.5×10 -6 / ℃) is significantly lower than aluminum (23.1×10 -6 / ℃), which causes shear stress in the copper-aluminum composite matrix material when the temperature changes, resulting in interface delamination or microcrack expansion. When the copper-aluminum composite matrix material is installed inside the vehicle, its bending point is prone to external cracking.

[0006] To improve the performance of existing copper-aluminum composite matrix materials, researchers are constantly modifying them, for example by adding rare earth elements such as cerium, yttrium, and chromium to enhance their conductivity and other properties. For example, patent publication number CN116994792B discloses a graphene copper-clad aluminum alloy conductor, its preparation method, and wire and cable comprising a graphene aluminum alloy core wire and a copper layer coated on the surface of the graphene aluminum alloy core wire. The graphene aluminum alloy core wire comprises 98.3-99.1% aluminum, 0.5-0.9% graphene conductive powder, and 0.4-0.8% rare earth additives. This method coats the copper layer on the surface of the graphene aluminum alloy core wire, significantly reducing copper consumption and costs. The resulting graphene copper-clad aluminum alloy conductor is lightweight, has low resistance, and exhibits excellent performance across various aspects. The graphene copper-clad aluminum alloy wire and cable produced using this method can replace copper-core wire and cables, offering safe and reliable operation, ease of transportation, and construction, while also conserving copper, electricity, and emissions, while also reducing costs and increasing efficiency. However, the working temperature of the graphene copper-clad aluminum alloy wire prepared by the above method is about 90°C, which still cannot meet the high temperature resistance performance requirements. Summary of the Invention

[0007] In view of the above-mentioned shortcomings of the prior art, the present invention provides a copper-aluminum composite material, a preparation method thereof, and a cable core, which can at least meet the high-temperature resistance performance requirements of high-voltage cable cores used in new energy vehicles.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] The first aspect of the present invention provides a copper-aluminum composite material, which has a double-layer structure, including an inner core and an outer shell coated on the outer surface of the inner core, the outer shell is a copper strip; the inner core has a fan-shaped topological structure, which includes multiple rare earth composite copper-aluminum alloy matrices, the raw materials of the rare earth composite copper-aluminum alloy matrix include copper powder, aluminum powder, nano-alumina, cerium source, magnesium source and nano-graphene, and is prepared by distributed mechanical alloying process and multiple ball milling.

[0010] According to the above-mentioned technical means, the inner core of the present application has a fan-shaped topology structure, which can effectively reduce the current loss caused by the electronic eddy current generated during the power transmission process by optimizing the current path and reducing the formation of electronic eddy currents, thereby improving the transmission efficiency; the fan-shaped topology structure of the inner core helps to improve the heat dissipation efficiency, thereby maintaining the stable operation of the copper-aluminum composite material when used as a cable core and extending its service life; and this fan-shaped topology structure can achieve uniform distribution of electrons to meet the increase in power transmission rate in high-safety scenarios of new energy vehicles, and can also reduce signal attenuation and improve signal transmission quality by optimizing the electromagnetic field distribution, thereby ensuring the stability and reliability of the copper-aluminum composite material when used as a cable core in different environments.

[0011] The present application adds the rare earth element cerium to the inner core, which can form high-melting-point compounds with impurities in the copper powder in the inner core, such as lead. These compounds are evenly distributed inside the grains in the form of tiny spherical particles, thereby effectively refining the grains and enhancing the plasticity of the material in a high-temperature environment; and cerium can significantly improve the mechanical properties of the copper-aluminum composite material, increase the density of the oxide film on the surface of the inner core, and improve the bonding strength between the oxide film and the outer shell, thereby enhancing the heat resistance of the copper-aluminum composite material.

[0012] The present invention adds magnesium to the inner core to improve the electrical conductivity and creep resistance of the copper-aluminum composite material. The present invention adds nanographene to the inner core to improve the electrical conductivity, mechanical strength, arc resistance and lightweight of the copper-aluminum composite material.

[0013] Furthermore, a plurality of rare earth composite copper-aluminum alloy substrates are staggered and arranged at a helical angle of 30° to 45° to form an inner core of a fan-shaped topological structure.

[0014] Furthermore, a heat dissipation path is provided between the inner core and the outer shell, and the heat dissipation path is filled with boron nitride.

[0015] Furthermore, the copper-aluminum composite material has properties that satisfy at least one of the following properties (a) to (c):

[0016] (a) The working temperature of copper-aluminum composite material is ≥150℃;

[0017] (b) Current density of copper-aluminum composite material ≥160A / mm 2 ;

[0018] (c) The electrical conductivity of the copper-aluminum composite material is 52MS / m~58MS / m.

[0019] A second aspect of the present invention provides a method for preparing a copper-aluminum composite material, comprising the following steps:

[0020] (1) Using copper powder, aluminum powder and nano-alumina as raw materials, a copper-aluminum alloy precursor was prepared by a step-by-step mechanical alloying process;

[0021] (2) adding a cerium source, a magnesium source, and nanographene to a copper-aluminum alloy precursor in sequence through a ball milling process, and then using a pressing process to prepare a rare earth composite copper-aluminum alloy matrix;

[0022] (3) multiple rare earth composite copper-aluminum alloy matrices are staggered at a helical angle of 30° to 45° to form an inner core of a fan-shaped topological structure;

[0023] (4) A layer of copper tape is coated on the outer surface of the inner core as an outer shell, and a heat dissipation path is provided between the outer shell and the inner core to prepare a copper-aluminum composite material.

[0024] Furthermore, in step (1), the weight percentages of copper powder, aluminum powder and nano-alumina are (67-70): (25-27): (3-8).

[0025] Furthermore, in step (2), the cerium source is selected from an aluminum-cerium master alloy;

[0026] And / or, the weight percentage of cerium in the rare earth composite copper-aluminum alloy matrix is 10wt% to 12wt%;

[0027] And / or, the weight percentage of magnesium in the rare earth composite copper-aluminum alloy matrix is 20wt% to 23wt%;

[0028] And / or, the weight percentage of nanographene in the rare earth composite copper-aluminum alloy matrix is 5wt% to 15wt%.

[0029] Furthermore, in step (4), the thickness of the copper strip is 0.1 mm to 0.3 mm;

[0030] And / or, the diameter of the inner core is 8 mm to 15 mm.

[0031] Furthermore, in step (4), a heat dissipation path is provided between the outer shell and the inner core, and the heat dissipation path is filled with boron nitride, and the filling amount of the boron nitride is 3wt% to 8wt%.

[0032] A third aspect of the present invention provides a cable core, comprising the copper-aluminum composite material, or comprising the copper-aluminum composite material prepared according to the above method.

[0033] The beneficial technical effects of the present invention are:

[0034] The copper-aluminum composite material prepared by the present invention, based on the double-layer structure of the outer shell and the inner core of the fan-shaped topology structure, can effectively improve the temperature resistance, creep resistance and arc resistance of the copper-aluminum composite material through the auxiliary effect of additives such as cerium, magnesium and nanographene, so as to ensure that it can withstand harsh environmental performance requirements such as high temperatures above 150°C when transmitting electric energy as a cable core, and can meet the requirements for improving the power transmission rate in high-safety scenarios of new energy vehicles.

[0035] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. DETAILED DESCRIPTION

[0036] Unless otherwise defined, all technical and / or scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the invention pertains. It should be understood that certain features of the present invention (described in the context of separate embodiments for clarity) may also be provided in combination in a single embodiment. On the contrary, a plurality of features of the present invention (described in the context of a single embodiment for brevity) may also be provided separately or in any suitable combination or in any other described embodiment of the present invention when appropriate. Certain features described in the context of various embodiments will not be considered as essential features of those embodiments unless the embodiment is inoperable without those elements. The present invention will be further described below by specific examples, but it should be noted that the specific process conditions and results described in the embodiments of the present invention are only used to illustrate the present invention and cannot limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and substance of the present invention should be included within the scope of protection of the present invention.

[0037] First of all, it should be noted that the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0038] The present invention provides a method for preparing a copper-aluminum composite material, comprising the following steps:

[0039] (1) Using copper powder, aluminum powder and nano-alumina as raw materials, a copper-aluminum alloy precursor was prepared through a step-by-step mechanical alloying process.

[0040] Specifically, in this step, the copper powder is selected from high-purity commercial-grade copper powder with a particle size of 25 μm; the aluminum powder is selected from high-purity aluminum powder with a particle size of 20 μm; and the nano-alumina is selected from high-purity nano-alumina powder with a particle size of 50 nm.

[0041] More specifically, the step-by-step mechanical alloying process of this step is as follows:

[0042] Under an argon protective atmosphere, copper powder and aluminum powder are mixed and ball milled at a speed of 300 rpm for 4 hours to form a solid solution pre-alloy of the copper powder and the aluminum powder. Nano-alumina is then added to the solid solution pre-alloy, the ball mill speed is adjusted to 200 rpm, and the ball milling is continued for 2 hours to obtain a mixture with uniformly dispersed nanoparticles, wherein the weight percentages of copper powder, aluminum powder, and nano-alumina in the mixture are (67-70):(25-27):(3-8);

[0043] Using anhydrous ethanol containing 0.1wt% PVP (polyvinyl pyrrolidone) as the medium, the above mixture was treated by pulsed ultrasound (power of 1000W / 20kHz) for 30 minutes. During the treatment process, the mixture worked for 5 seconds and rested for 2 seconds, and the temperature of the mixture was controlled below 40°C by circulating water cooling. Finally, a copper-aluminum alloy precursor with a multi-scale structure was obtained.

[0044] (2) The cerium source, magnesium source and nanographene are sequentially added to the copper-aluminum alloy precursor by a ball milling process, and then a pressing process is adopted to prepare a rare earth composite copper-aluminum alloy matrix.

[0045] Specifically, in this step, the cerium source is selected from an aluminum-cerium master alloy, further an Al-10Ce master alloy; the magnesium source is selected from magnesium powder or a magnesium alloy obtained by alloying magnesium with metals such as aluminum and zinc.

[0046] More specifically, the process for preparing the rare earth composite copper-aluminum alloy matrix in this step is as follows:

[0047] Al-10Ce master alloy was added to the copper-aluminum alloy precursor and ball milled for 30 hours at 300 rpm using a high-energy ball mill; magnesium powder was then added and ball milled for 20 hours at 600 rpm; finally, nano-graphene was added and ball milled for 5 hours at 800 rpm to obtain a powder;

[0048] A high-precision pressing process is adopted with multi-stage gradient pressure control (adjustable range 200MPa ~ 600MPa) and nano-scale mold calibration technology, and the above-mentioned powder is pressed into a rare earth composite copper-aluminum alloy matrix through a cold isostatic pressing and cold rolling composite process. The porosity of the rare earth composite copper-aluminum alloy matrix is strictly controlled to be less than 3%. In combination with a gradient annealing process (staged temperature control of 300℃ ~ 450℃), the thermal stress of the rare earth composite copper-aluminum alloy matrix is eliminated, so that the material densification and interface bonding strength are simultaneously optimized.

[0049] More specifically, the weight percentage of cerium in the rare earth composite copper-aluminum alloy matrix is 10wt% to 12wt%; the weight percentage of magnesium in the rare earth composite copper-aluminum alloy matrix is 20wt% to 23wt%; and the weight percentage of nanographene in the rare earth composite copper-aluminum alloy matrix is 5wt% to 15wt%.

[0050] (3) Multiple rare earth composite copper-aluminum alloy matrices are staggered at a helical angle of 30° to 45° to form an inner core of a fan-shaped topological structure.

[0051] Specifically, in this step, each rare earth composite copper-aluminum alloy matrix is drawn into a matrix with a diameter of ≤0.3 mm using a special-shaped wire drawing die, and then multiple matrices are braided into the above-mentioned fan-shaped topological structure using a braiding machine. More specifically, the number of rare earth composite copper-aluminum alloy matrices in this application can be 8 to 12.

[0052] (4) A layer of copper tape is coated on the outer surface of the inner core as an outer shell, and a heat dissipation path is provided between the outer shell and the inner core. The heat dissipation path is filled with boron nitride, and the filling amount of boron nitride is 3wt% to 8wt%, thereby preparing a copper-aluminum composite material.

[0053] Specifically, in this step, the purity of the copper strip is ≥99.95%, the thickness of the copper strip is 0.1 mm to 0.3 mm, and the diameter of the inner core is 8 mm to 15 mm.

[0054] The present invention also provides a copper-aluminum composite material, which has a double-layer structure, including an inner core and an outer shell coated on the outer surface of the inner core, wherein the outer shell is a copper strip; the inner core has a fan-shaped topological structure, which includes multiple rare earth composite copper-aluminum alloy matrices, and the raw materials of the rare earth composite copper-aluminum alloy matrix include copper powder, aluminum powder, nano-alumina, cerium source, magnesium source and nano-graphene, which are prepared by distributed mechanical alloying process and multiple ball milling.

[0055] Furthermore, the inner core of the present application has a fan-shaped topology structure, which can effectively reduce the current loss caused by the electronic eddy current generated during the power transmission process by optimizing the current path and reducing the formation of electronic eddy currents, thereby improving the transmission efficiency; the fan-shaped topology structure of the inner core helps to improve the heat dissipation efficiency, thereby maintaining the stable operation of the copper-aluminum composite material when used as a cable core and extending its service life; and this fan-shaped topology structure can achieve uniform distribution of electrons to meet the increase in power transmission rate in high-safety scenarios of new energy vehicles, and can also reduce signal attenuation and improve signal transmission quality by optimizing the electromagnetic field distribution, ensuring the stability and reliability of the copper-aluminum composite material when used as a cable core in different environments.

[0056] Furthermore, the present application adds the rare earth element cerium to the inner core, which can form high-melting-point compounds with impurities in the copper powder in the inner core, such as lead. These compounds are evenly distributed inside the grains in the form of tiny spherical particles, thereby effectively refining the grains and enhancing the plasticity of the material in a high-temperature environment; and cerium can significantly improve the mechanical properties of the copper-aluminum composite material, increase the density of the oxide film on the surface of the inner core, and enhance the bonding strength between the oxide film and the outer shell, thereby enhancing the heat resistance of the copper-aluminum composite material.

[0057] Furthermore, the present invention adds magnesium to the inner core to improve the electrical conductivity and creep resistance of the copper-aluminum composite material. The present invention adds nanographene to the inner core to improve the electrical conductivity, mechanical strength, arc resistance and lightweight of the copper-aluminum composite material.

[0058] Furthermore, a plurality of rare earth composite copper-aluminum alloy substrates are staggered and arranged at a helical angle of 30° to 45° to form an inner core of a fan-shaped topological structure.

[0059] Furthermore, a heat dissipation path is provided between the inner core and the outer shell, and the heat dissipation path is filled with boron nitride. The present application improves the heat dissipation performance, electrical insulation performance, mechanical strength and chemical stability of the copper-aluminum composite material by filling it with boron nitride.

[0060] Furthermore, the copper-aluminum composite material has properties that satisfy at least one of the following properties (a) to (c):

[0061] (a) The working temperature of copper-aluminum composite material is ≥150℃;

[0062] (b) Current density of copper-aluminum composite material ≥160A / mm 2 ;

[0063] (c) The electrical conductivity of the copper-aluminum composite material is 52MS / m~58MS / m.

[0064] The present invention also provides a cable core, comprising the copper-aluminum composite material, or comprising the copper-aluminum composite material prepared according to the above method.

[0065] The present invention is described in detail below by way of specific examples. It should also be understood that the following examples are only used to specifically illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples within a suitable range, and those skilled in the art can make selections within a suitable range through the description herein, and are not to be limited to the specific numerical values exemplified below.

[0066] Example 1

[0067] (1) Using high-purity commercial-grade copper powder with a particle size of 25 μm, high-purity aluminum powder with a particle size of 20 μm, and high-purity nano-alumina powder with a particle size of 50 nm as raw materials, the copper powder and the aluminum powder are mixed under an argon protective atmosphere, and ball milled at a speed of 300 rpm for 4 hours to form a solid solution pre-alloy of the copper powder and the aluminum powder, and then the nano-alumina powder is added to the solid solution pre-alloy, and the ball mill speed is adjusted to 200 rpm. The ball milling is continued for 2 hours to obtain a mixture with uniformly dispersed nanoparticles, wherein the weight percentages of copper powder, aluminum powder, and nano-alumina in the mixture are 70:27:3;

[0068] Using anhydrous ethanol containing 0.1wt% PVP (polyvinyl pyrrolidone) as the medium, the above mixture was treated by pulsed ultrasound (power of 1000W / 20kHz) for 30 minutes. During the treatment process, the mixture worked for 5 seconds and rested for 2 seconds, and the temperature of the mixture was controlled below 40°C by circulating water cooling. Finally, a copper-aluminum alloy precursor with a multi-scale structure was obtained.

[0069] (2) Adding Al-10Ce master alloy to the copper-aluminum alloy precursor, using a high-energy ball mill for 30 hours at a speed of 300 rpm; then adding magnesium powder and ball milling for 20 hours at a speed of 600 rpm; finally adding nanographene and ball milling for 5 hours at a speed of 800 rpm to obtain a powder;

[0070] A high-precision pressing process is adopted, with multi-level gradient pressure control and nano-scale mold calibration technology, to press the above powder into a rare earth composite copper-aluminum alloy matrix through a cold isostatic pressing and cold rolling composite process. The porosity of the rare earth composite copper-aluminum alloy matrix is strictly controlled to be less than 3%, and a gradient annealing process is combined to eliminate the thermal stress of the rare earth composite copper-aluminum alloy matrix, so that the material densification and interface bonding strength are simultaneously optimized.

[0071] The weight percentage of cerium in the rare earth composite copper-aluminum alloy matrix is 11wt%; the weight percentage of magnesium in the rare earth composite copper-aluminum alloy matrix is 22wt%; and the weight percentage of nanographene in the rare earth composite copper-aluminum alloy matrix is 10wt%.

[0072] (3) Ten rare earth composite copper-aluminum alloy substrates are drawn into substrates with a diameter of ≤0.3 mm through a special-shaped wire drawing die, and then the 10 substrates are woven into a fan-shaped topological structure core with a staggered arrangement of a 35° helix angle through a weaving machine.

[0073] (4) A layer of copper tape is coated on the outer surface of the inner core as an outer shell, and a heat dissipation path is provided between the outer shell and the inner core. The heat dissipation path is filled with boron nitride, and the filling amount of boron nitride is 3 wt %. A copper-aluminum composite material is prepared, wherein the purity of the copper tape is ≥99.95%, the thickness of the copper tape is 0.2 mm, and the diameter of the inner core is 10 mm.

[0074] Example 2

[0075] (1) Using high-purity commercial-grade copper powder with a particle size of 25 μm, high-purity aluminum powder with a particle size of 20 μm, and high-purity nano-alumina powder with a particle size of 50 nm as raw materials, the copper powder and the aluminum powder are mixed under an argon protective atmosphere, and ball milled at a speed of 300 rpm for 4 hours to form a solid solution pre-alloy of the copper powder and the aluminum powder, and then the nano-alumina powder is added to the solid solution pre-alloy, and the ball mill speed is adjusted to 200 rpm. The ball milling is continued for 2 hours to obtain a mixture with uniformly dispersed nanoparticles, wherein the weight percentages of copper powder, aluminum powder, and nano-alumina in the mixture are 67:25:8;

[0076] Using anhydrous ethanol containing 0.1wt% PVP (polyvinyl pyrrolidone) as the medium, the above mixture was treated by pulsed ultrasound (power of 1000W / 20kHz) for 30 minutes. During the treatment process, the mixture worked for 5 seconds and rested for 2 seconds, and the temperature of the mixture was controlled below 40°C by circulating water cooling. Finally, a copper-aluminum alloy precursor with a multi-scale structure was obtained.

[0077] (2) Adding Al-10Ce master alloy to the copper-aluminum alloy precursor, using a high-energy ball mill for 30 hours at a speed of 300 rpm; then adding magnesium powder and ball milling for 20 hours at a speed of 600 rpm; finally adding nanographene and ball milling for 5 hours at a speed of 800 rpm to obtain a powder;

[0078] A high-precision pressing process is adopted, with multi-level gradient pressure control and nano-scale mold calibration technology, to press the above powder into a rare earth composite copper-aluminum alloy matrix through a cold isostatic pressing and cold rolling composite process. The porosity of the rare earth composite copper-aluminum alloy matrix is strictly controlled to be less than 3%, and a gradient annealing process is combined to eliminate the thermal stress of the rare earth composite copper-aluminum alloy matrix, so that the material densification and interface bonding strength are simultaneously optimized.

[0079] The weight percentage of cerium in the rare earth composite copper-aluminum alloy matrix is 10wt%; the weight percentage of magnesium in the rare earth composite copper-aluminum alloy matrix is 20wt%; and the weight percentage of nanographene in the rare earth composite copper-aluminum alloy matrix is 5wt%.

[0080] (3) 12 rare earth composite copper-aluminum alloy substrates are drawn into substrates with a diameter of ≤0.3 mm through a special-shaped wire drawing die, and then the 12 substrates are woven into a fan-shaped topological structure core with a staggered arrangement of a 30° helix angle through a weaving machine.

[0081] (4) A layer of copper tape is coated on the outer surface of the inner core as an outer shell, and a heat dissipation path is provided between the outer shell and the inner core. The heat dissipation path is filled with boron nitride, and the filling amount of boron nitride is 5wt%. A copper-aluminum composite material is prepared, wherein the purity of the copper tape is ≥99.95%, the thickness of the copper tape is 0.15mm, and the diameter of the inner core is 15mm.

[0082] Example 3

[0083] (1) Using high-purity commercial-grade copper powder with a particle size of 25 μm, high-purity aluminum powder with a particle size of 20 μm, and high-purity nano-alumina powder with a particle size of 50 nm as raw materials, the copper powder and the aluminum powder are mixed under an argon protective atmosphere, and ball milled at a speed of 300 rpm for 4 hours to form a solid solution pre-alloy of the copper powder and the aluminum powder, and then the nano-alumina powder is added to the solid solution pre-alloy, and the ball mill speed is adjusted to 200 rpm. The ball milling is continued for 2 hours to obtain a mixture with uniformly dispersed nanoparticles, wherein the weight percentages of copper powder, aluminum powder, and nano-alumina in the mixture are 68:26:6;

[0084] Using anhydrous ethanol containing 0.1wt% PVP (polyvinyl pyrrolidone) as the medium, the above mixture was treated by pulsed ultrasound (power of 1000W / 20kHz) for 30 minutes. During the treatment process, the mixture worked for 5 seconds and rested for 2 seconds, and the temperature of the mixture was controlled below 40°C by circulating water cooling. Finally, a copper-aluminum alloy precursor with a multi-scale structure was obtained.

[0085] (2) Adding Al-10Ce master alloy to the copper-aluminum alloy precursor, using a high-energy ball mill for 30 hours at a speed of 300 rpm; then adding magnesium powder and ball milling for 20 hours at a speed of 600 rpm; finally adding nanographene and ball milling for 5 hours at a speed of 800 rpm to obtain a powder;

[0086] A high-precision pressing process is adopted, with multi-level gradient pressure control and nano-scale mold calibration technology, to press the above powder into a rare earth composite copper-aluminum alloy matrix through a cold isostatic pressing and cold rolling composite process. The porosity of the rare earth composite copper-aluminum alloy matrix is strictly controlled to be less than 3%, and a gradient annealing process is combined to eliminate the thermal stress of the rare earth composite copper-aluminum alloy matrix, so that the material densification and interface bonding strength are simultaneously optimized.

[0087] The weight percentage of cerium in the rare earth composite copper-aluminum alloy matrix is 12wt%; the weight percentage of magnesium in the rare earth composite copper-aluminum alloy matrix is 23wt%; and the weight percentage of nanographene in the rare earth composite copper-aluminum alloy matrix is 15wt%.

[0088] (3) Eight rare earth composite copper-aluminum alloy substrates are drawn into substrates with a diameter of ≤0.3 mm through a special-shaped wire drawing die, and then the eight substrates are woven into a fan-shaped topological structure core with a staggered arrangement of a 45° helix angle through a weaving machine.

[0089] (4) A layer of copper tape is coated on the outer surface of the inner core as an outer shell, and a heat dissipation path is provided between the outer shell and the inner core. The heat dissipation path is filled with boron nitride, and the filling amount of boron nitride is 8wt%, thereby preparing a copper-aluminum composite material, wherein the purity of the copper tape is ≥99.95%, the thickness of the copper tape is 0.3mm, and the diameter of the inner core is 8mm.

[0090] Comparative Example 1

[0091] The difference between this comparative example and Example 1 is:

[0092] (2) adding magnesium powder to the copper-aluminum alloy precursor and milling the mixture using a high-energy ball mill for 20 hours at a speed of 600 rpm; then adding nanographene and milling the mixture for 5 hours at a speed of 800 rpm to obtain a powder;

[0093] A high-precision pressing process is adopted, with multi-level gradient pressure control and nano-scale mold calibration technology, to press the above powder into a composite copper-aluminum alloy matrix through a cold isostatic pressing and cold rolling composite process. The porosity of the composite copper-aluminum alloy matrix is strictly controlled to be less than 3%, and a gradient annealing process is combined to eliminate the thermal stress of the composite copper-aluminum alloy matrix, so that the material densification and interface bonding strength are simultaneously optimized.

[0094] The weight percentage of magnesium in the composite copper-aluminum alloy matrix is 20wt%; the weight percentage of nanographene in the composite copper-aluminum alloy matrix is 10wt%.

[0095] Comparative Example 2

[0096] The difference between this comparative example and Example 1 is:

[0097] (2) Adding Al-10Ce master alloy to the copper-aluminum alloy precursor, using a high-energy ball mill for 30 hours at a speed of 300 rpm; then adding magnesium powder and ball milling for 20 hours at a speed of 600 rpm to obtain a powder;

[0098] A high-precision pressing process is adopted, with multi-level gradient pressure control and nano-scale mold calibration technology, to press the above powder into a rare earth composite copper-aluminum alloy matrix through a cold isostatic pressing and cold rolling composite process. The porosity of the rare earth composite copper-aluminum alloy matrix is strictly controlled to be less than 3%, and a gradient annealing process is combined to eliminate the thermal stress of the rare earth composite copper-aluminum alloy matrix, so that the material densification and interface bonding strength are simultaneously optimized.

[0099] The weight percentage of cerium in the rare earth composite copper-aluminum alloy matrix is 15wt%; the weight percentage of magnesium in the rare earth composite copper-aluminum alloy matrix is 25wt%.

[0100] Comparative Example 3

[0101] The difference between this comparative example and Example 1 is:

[0102] (3) Ten rare earth composite copper-aluminum alloy substrates are drawn into substrates with a diameter of ≤0.3 mm by a wire drawing die, and then the ten substrates are woven into an inner core of a circular distribution structure by a weaving machine.

[0103] Comparative Example 4

[0104] The difference between this comparative example and Example 1 is:

[0105] (2) Adding Mg-Y20 master alloy to the copper-aluminum alloy precursor, using a high-energy ball mill for 30 hours at a speed of 300 rpm; then adding magnesium powder and ball milling for 20 hours at a speed of 600 rpm; finally adding nanographene and ball milling for 5 hours at a speed of 800 rpm to obtain a powder;

[0106] A high-precision pressing process is adopted, with multi-level gradient pressure control and nano-scale mold calibration technology, to press the above powder into a rare earth composite copper-aluminum alloy matrix through a cold isostatic pressing and cold rolling composite process. The porosity of the rare earth composite copper-aluminum alloy matrix is strictly controlled to be less than 3%, and a gradient annealing process is combined to eliminate the thermal stress of the rare earth composite copper-aluminum alloy matrix, so that the material densification and interface bonding strength are simultaneously optimized.

[0107] The weight percentage of yttrium in the rare earth composite copper-aluminum alloy matrix is 8wt%; the weight percentage of magnesium in the rare earth composite copper-aluminum alloy matrix is 25wt%; and the weight percentage of nanographene in the rare earth composite copper-aluminum alloy matrix is 10wt%.

[0108] Comparative Example 5

[0109] The difference between this comparative example and Example 1 is:

[0110] The weight percentage of cerium in the rare earth composite copper-aluminum alloy matrix is 15wt%; the weight percentage of magnesium in the rare earth composite copper-aluminum alloy matrix is 22wt%; and the weight percentage of nanographene in the rare earth composite copper-aluminum alloy matrix is 10wt%.

[0111] Comparative Example 6

[0112] The difference between this comparative example and Example 1 is:

[0113] The weight percentage of cerium in the rare earth composite copper-aluminum alloy matrix is 5wt%; the weight percentage of magnesium in the rare earth composite copper-aluminum alloy matrix is 22wt%; and the weight percentage of nanographene in the rare earth composite copper-aluminum alloy matrix is 10wt%.

[0114] Comparative Example 7

[0115] The difference between this comparative example and Example 1 is:

[0116] The thickness of the copper strip is 0.5 mm and the diameter of the inner core is 10 mm.

[0117] Performance testing

[0118] Conductivity: The conductivity of the copper-aluminum composite materials prepared in Examples 1 to 3 and Comparative Examples 1 to 7 was accurately measured using a conductivity tester to ensure that they met the electrical transmission requirements. The test results are shown in Table 1.

[0119] Current density: Using the regional electrode test method, the copper-aluminum composite materials prepared in Examples 1 to 3 and Comparative Examples 1 to 7 were divided into multiple regions. Local current density data were obtained using independent test electrodes. The test results are shown in Table 1.

[0120] Temperature rise reduction rate under high-frequency working conditions: Using a high-frequency current generator and a constant temperature box, the temperature rise reduction rate of the copper-aluminum composite materials prepared in Examples 1 to 3 and Comparative Examples 1 to 7 under high-frequency working conditions was tested by a comparative test method. The test results are shown in Table 1.

[0121] Fatigue life: In accordance with IEC 60811, the copper-aluminum composite materials prepared in Examples 1 to 3 and Comparative Examples 1 to 7 were subjected to 150,000 cycles at a bending radius of 5D and a frequency of 2 Hz. Conductivity fluctuations were simultaneously monitored (accuracy ±0.5%). The test results are shown in Table 1.

[0122] Creep strength: Based on ISO 204, the copper-aluminum composite materials prepared in Examples 1 to 3 and Comparative Examples 1 to 7 were continuously loaded at 150°C / 50 MPa stress for 1000 hours using a high-temperature creep tester (Shimadzu AG-X). The deformation was recorded using a laser displacement sensor (KEYENCE LK-G5000). The test results are shown in Table 1.

[0123] Arc resistance performance: The arc voltage and current waveforms were collected synchronously by a high-voltage probe (bandwidth ≥ 100 MHz) and a current sensor to generate an arc volt-ampere characteristic curve. The arc energy absorption difference between the copper-aluminum composite materials prepared in Examples 1 to 3 and Comparative Examples 1 to 7 and the pure copper material was compared. The arc resistance performance was calculated as follows:

[0124] Where E is the total arc energy at the same voltage.

[0125] The test results are shown in Table 1.

[0126] Maximum operating temperature: The maximum operating temperature detection method of copper-aluminum composite materials as cable cores requires a comprehensive evaluation based on the material tolerance and insulation stability. Therefore, this application conducts thermal aging tests and dynamic temperature rise limit tests on the copper-aluminum composite materials prepared in Examples 1 to 3 and Comparative Examples 1 to 7, and comprehensively evaluates the maximum operating temperature. The test results are shown in Table 1.

[0127] The experimental data and analysis are as follows:

[0128] Table 1 Performance test results of copper-aluminum composite materials of various embodiments and comparative examples

[0129]

[0130] As can be seen from Table 1, the copper-aluminum composite materials prepared in the examples of the present application have higher performance in all aspects than the copper-aluminum composite materials of comparative examples 1 to 3 and comparative examples 5 to 6. This is because the copper-aluminum composite material of the present application has a Cu / Al metallurgical interface thickness of 50nm to 100nm at the macro level, Al is solid-dissolved in the Cu matrix at the micro level, and the solid solubility reaches 4.2at%, and the synergistic effect of the nano-alumina particles can exhibit a tensile strength of 220MPa at an operating temperature of 200°C, which is 58% higher than that of pure copper materials, and exhibits a conductivity of more than 50MS / m, which can retain 85% of the conductivity of pure copper materials. At the same time, the grain size of the copper-aluminum composite material of the present application is stable at below 1μm, and its high-temperature comprehensive performance significantly surpasses that of traditional pure copper cables.

[0131] The present application adds the rare earth element cerium to the copper-aluminum alloy precursor, which can form high-melting-point compounds with impurities such as lead in the copper powder in the inner core. These compounds are evenly distributed inside the grains in the form of tiny spherical particles, thereby effectively refining the grains and increasing the maximum operating temperature of the material. In addition, cerium can significantly improve the mechanical properties of the copper-aluminum composite material, increase the density of the oxide film on the surface of the inner core, and improve the bonding strength between the oxide film and the outer shell, thereby enhancing the heat resistance of the copper-aluminum composite material and improving the temperature rise reduction rate under high-frequency working conditions. In addition, the present application adds magnesium to the inner core to improve the electrical conductivity and creep resistance of the copper-aluminum composite material; and adds nanographene to improve the electrical conductivity, creep resistance, arc resistance and lightweight of the copper-aluminum composite material.

[0132] Furthermore, the copper-aluminum composite material of the present application benefits from the adaptive deformation ability of the fan-shaped topological structure. The conductivity fluctuation of the material is less than 2% when the bending radius is ≤5D. At the same time, through grain refinement (10μm-20μm) and nano-alumina strengthening (2vol% dispersion), the fatigue life is extended to 160,000 cycles (twice as much as the traditional process), which can meet the dual needs of high-density current transmission and mechanical reliability in the complex wiring space of new energy vehicles.

[0133] In Comparative Example 1, the copper-aluminum composite material was not added with rare earth elements, and its temperature resistance decreased, thereby reducing its maximum operating temperature. In Comparative Example 2, the copper-aluminum composite material was not added with nanographene, and its electrical conductivity, creep strength, and arc resistance all decreased.

[0134] The copper-aluminum composite material of Comparative Example 3 adopts a circular distribution structure, and its internal electron distribution is uneven, which easily leads to the generation of internal electron eddy currents, resulting in increased resistance, decreased conductivity, and decreased overall material performance.

[0135] Comparative Example 4: The copper-aluminum composite material is added with rare earth yttrium. The addition of yttrium can effectively improve its temperature resistance and electrical conductivity, thereby increasing the conductivity of the material and achieving a maximum operating temperature of 150°C. However, the resistivity of yttrium is high and the current density of the material is significantly reduced.

[0136] The cerium addition amounts of the copper-aluminum composite materials of Comparative Examples 5 and 6 are not within the specified range of this application, which indicates that the cerium addition amount plays a key role in the temperature resistance of the material. Therefore, the maximum operating temperature of the materials of Comparative Examples 5 and 6 is significantly lower than the maximum operating temperature of the materials of the examples of this application.

[0137] The outer shell copper strip of the material of Comparative Example 7 is thick. Increasing the thickness of the copper strip will lead to increased conductivity and reduced current density. Under high-frequency working conditions, the effect of the copper strip thickness on the temperature rise reduction rate is mainly reflected in the difference in thermal conductivity and heat capacity. Since copper has better thermal conductivity than aluminum, but its density is large and its volume is small, resulting in a limited heat dissipation area; while aluminum has a large surface area, which is conducive to heat dissipation, but its heat conduction speed is slow. Therefore, the thickness of the copper strip of Comparative Example 7 of the present application is based on a comprehensive consideration of the balance between thermal conductivity and heat dissipation area, and the temperature rise reduction rate is reduced by evaluating its high-frequency working conditions. If the outer shell copper strip of the material of Comparative Example 7 is too thick, the fatigue life of the copper-aluminum composite material will be reduced. If the copper strip is too thick, the weight of the material will be increased, resulting in an accelerated creep rate, thereby affecting the fatigue life of the material. Therefore, the comprehensive performance of the material of Comparative Example 7 is not as good as the performance of the copper-aluminum composite material of the embodiment of the present application.

[0138] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A copper-aluminum composite material, characterized in that: The copper-aluminum composite material has a double-layer structure, including an inner core and an outer shell coated on the outer surface of the inner core, wherein the outer shell is a copper strip; the inner core has a fan-shaped topological structure, which includes multiple rare earth composite copper-aluminum alloy matrices, and the raw materials of the rare earth composite copper-aluminum alloy matrix include copper powder, aluminum powder, nano-alumina, cerium source, magnesium source and nano-graphene, which are prepared by distributed mechanical alloying process and multiple ball milling.

2. The copper-aluminum composite material according to claim 1, characterized in that The multiple rare earth composite copper-aluminum alloy matrices are staggered and arranged at a helical angle of 30° to 45° to form the inner core of the fan-shaped topological structure.

3. The copper-aluminum composite material according to claim 1 or 2, characterized in that: A heat dissipation path is provided between the inner core and the outer shell, and the heat dissipation path is filled with boron nitride.

4. The copper-aluminum composite material according to claim 3, characterized in that The copper-aluminum composite material has properties that satisfy at least one of the following properties (a) to (c): (a) The working temperature of the copper-aluminum composite material is ≥150°C; (b) The current density of the copper-aluminum composite material is ≥160A / mm 2 ; (c) The electrical conductivity of the copper-aluminum composite material is 52MS / m to 58MS / m.

5. A method for preparing a copper-aluminum composite material, characterized in that: The method comprises the following steps: (1) Using copper powder, aluminum powder and nano-alumina as raw materials, a copper-aluminum alloy precursor was prepared by a step-by-step mechanical alloying process; (2) adding a cerium source, a magnesium source, and nanographene to a copper-aluminum alloy precursor in sequence through a ball milling process, and then using a pressing process to prepare a rare earth composite copper-aluminum alloy matrix; (3) The plurality of rare earth composite copper-aluminum alloy substrates are staggered at a helical angle of 30° to 45° to form an inner core of a fan-shaped topological structure; (4) A layer of copper strip is coated on the outer surface of the inner core as an outer shell, and a heat dissipation path is provided between the outer shell and the inner core, thereby preparing the copper-aluminum composite material.

6. The method according to claim 5, characterized in that The weight percentages of copper powder, aluminum powder and nano-alumina in the step (1) are (67-70): (25-27): (3-8).

7. The method according to claim 5 or 6, characterized in that In the step (2), the cerium source is selected from an aluminum-cerium master alloy; And / or, the weight percentage of cerium in the rare earth composite copper-aluminum alloy matrix is 10wt% to 12wt%; And / or, the weight percentage of magnesium in the rare earth composite copper-aluminum alloy matrix is 20wt% to 23wt%; And / or, the weight percentage of nanographene in the rare earth composite copper-aluminum alloy matrix is 5wt% to 15wt%.

8. The method according to claim 5 or 6, characterized in that In the step (4), the thickness of the copper strip is 0.1 mm to 0.3 mm; And / or, the diameter of the inner core is 8 mm to 15 mm.

9. The method according to claim 5 or 6, characterized in that In the step (4), a heat dissipation path is provided between the outer shell and the inner core, and the heat dissipation path is filled with boron nitride, and the filling amount of the boron nitride is 3wt% to 8wt%.

10. A cable core, characterized in that: The invention comprises the copper-aluminum composite material according to any one of claims 1 to 4, or comprises the copper-aluminum composite material prepared by the method according to any one of claims 5 to 9.

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