Rare earth aluminum alloy cable material, preparation method and application of rare earth aluminum alloy cable material to power transmission line

Abstract

The invention discloses a rare earth aluminum alloy cable material, a preparation method and application of the rare earth aluminum alloy cable material to a power transmission line, the cable material comprises, based on the total weight, 0.3-0.6 wt% of Er, 0.1-0.3 wt% of Yb, 0.05-0.15 wt% of Ce, 0.35-0.5 wt% of Mg, 0.2-1.5 wt% of Cu, 0.1-2.5 wt% of nano SiC particles, 0.1-0.3 wt% of graphene and the balance Al and impurities, the cable material is designed by adopting a three-layer gradient structure, the middle layer contains 0.1-0.2 wt% of Er and 0.01-0.2 wt% of graphene, and the core layer contains 0.5-0.6 wt% of Er and less than 0.01 wt% of graphene; during preparation, the composite wire with the thickness ratio of the core layer to the middle layer being 1: 3-3: 1 is formed through argon protection smelting, ultrasonic dispersion of nano-particles and static magnetic field assisted co-extrusion, and the surface roughness is enhanced in combination with micro-arc oxidation (Ra = 0.5-1.5 microns). The cable material is excellent in tensile strength, dynamic fatigue life, electromagnetic shielding performance and corrosion resistance through Er gradient distribution, SiC / graphene coating and multi-scale interface synergistic effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of cable materials, and particularly relates to a cable material of rare earth aluminum alloy, a preparation method thereof, and an application thereof on transmission lines. Background Art

[0002] In the field of power transmission, copper conductors have long dominated, but their high cost and weight disadvantages have prompted aluminum alloy to become a substitute material. Aluminum alloy can not only reduce the comprehensive cost by 30%-50%, but also alleviate the problem of overcapacity of electrolytic aluminum in China, and at the same time has the advantage of light weight. However, traditional aluminum alloy cables have significant performance defects: First, the mechanical strength and creep resistance are insufficient. The deformation rate of pure aluminum is 40% higher than that of copper under the conditions of 120°C and 112 MPa, and microcracks are likely to occur under long-term alternating loads. Moreover, the high-temperature softening characteristic increases the fire risk under extreme working conditions. Second, the corrosion resistance is weak. The β-Al2O3 oxide film naturally formed on the aluminum surface has a loose structure and is easily eroded by acids and alkalis. The electrochemical corrosion rate in a humid and hot environment is 2-3 times faster than that of copper. Third, processing technology defects occur frequently. Problems such as porosity, slag inclusion, and coarse grains are likely to occur during the casting process. For example, when the grain size exceeds 50 μm, the elongation rate decreases by 30%. At the same time, the poor thermal stability makes it difficult to control the springback during rolling, and the finished product rate is less than 70%.

[0003] The introduction of rare earth elements significantly optimizes the performance of aluminum alloy through the microalloying effect. For example, in CN102978474B, rare earth elements such as lanthanum (La) and cerium (Ce) are added. The above-mentioned high-melting-point active metal compounds are dispersed between grains and dendrites in a network or skeleton shape and are firmly combined with the matrix, playing a role in strengthening and stabilizing the grain boundaries. At the same time, it can also neutralize elements such as Fe and Cu in the molten metal, form high-melting-point compounds or make them uniformly distributed throughout the crystal structure between dendrites, eliminating the dendritic structure, and increasing the dynamic fatigue life by more than 50%. At the same time, the formed rare earth oxide film is transformed into a dense α-Al2O3 structure, and the corrosion resistance is increased by more than 3 times. However, the rare earth modification process still causes new problems: Although high-temperature annealing (850-950°C) enhances the creep resistance, it leads to the risk of grain coarsening, and the incidence of center cracks during casting increases by 15%. To improve the electromagnetic shielding efficiency, the conductor cross-sectional area needs to be expanded to 1.5 times that of copper, resulting in material redundancy and a 20% increase in laying cost. In addition, the chemical bonding efficiency between the rare earth oxide film and the silane coupling agent is insufficient, and the interfacial adhesion attenuation rate after humid and hot cycling still reaches 25%. Moreover, although the rare earth oxide film improves the corrosion resistance, it cannot take into account the electrical conductivity. If the rare earth oxide film layer is too thick, it is not conducive to high-power long-distance power transmission of the cable.

[0004] These problems severely restrict the long-term reliability of rare earth aluminum alloy cable materials in areas with high electromagnetic interference, frequent typhoons, and humid and hot climates. There is an urgent need for an aluminum alloy cable material with excellent dynamic fatigue performance, electromagnetic compatibility, and surface adhesion, without reducing its own mechanical and electrical properties, and meeting the requirements of large-scale production. Summary of the Invention

[0005] The present invention aims to provide a rare earth aluminum alloy cable material with excellent dynamic fatigue performance, electromagnetic compatibility, and surface adhesion, without reducing its own mechanical and electrical properties, and capable of achieving large-scale production. The specific implementation scheme is as follows: A rare earth aluminum alloy cable material, based on the total weight of the cable material, includes the following components: Er 0.3 - 0.6 wt%, Yb 0.1 - 0.3 wt%, Ce 0.05 - 0.15 wt%, Mg 0.35 - 0.5 wt%, Cu 0.2 - 1.5 wt%, nano SiC particles 0.1 - 2.5 wt%, graphene 0.1 - 0.3 wt%, and the balance is Al and unavoidable impurities. The cable material includes a three-layer structure, namely: The outer layer, which is a SiC / graphene composite coating by plasma-enhanced chemical vapor deposition, with an average thickness H1 of 1 - 5 μm. In this layer, no metal elements are contained. The middle layer, based on the total weight of this layer, includes the following components: Er 0.1 - 0.2 wt%, Yb 0.1 - 0.3 wt%, Ce 0.05 - 0.1 wt%, Mg 0.35 - 0.5 wt%, Cu 0.2 - 1.5 wt%, nano SiC particles 0.1 - 2 wt%, graphene 0.01 - 0.2 wt%, and the balance is Al and unavoidable impurities; The core layer, based on the total weight of this layer, includes the following components: Er 0.5 - 0.6 wt%, Yb 0.1 - 0.3 wt%, Ce 0.1 - 0.15 wt%, Mg 0.35 - 0.5 wt%, Cu 0.2 - 1.5 wt%, nano SiC particles 0.1 - 2 wt%, and the graphene content is less than 0.01 wt%, and the balance is Al and unavoidable impurities.

[0006] In one of the schemes, the ratio H2 / H3 of the average thickness H2 of the middle layer to the average thickness H3 of the core layer is 3:1 - 1:3.

[0007] In one of the schemes, the surface roughness Ra of the cable material is 0.5 - 1.5 μm.

[0008] The present invention also discloses a preparation method of the rare earth aluminum alloy cable material of the present invention, including the following steps: (1)Core layer preparation: Under an argon protection environment, place 0.5 - 0.6 wt% Er ingot, 0.1 - 0.3 wt% Yb ingot, 0.1 - 0.15 wt% Ce ingot, 0.35 - 0.6 wt% Mg ingot, 0.2 - 1.5 wt% Cu ingot, 0.1 - 2 wt% nano - SiC particles, and the balance Al ingot in a vacuum induction furnace according to the core layer composition of the present invention. Control the melt temperature at 750 - 850 °C, and simultaneously perform ultrasonic dispersion treatment at 100 - 150 kHz / 500 W for 10 - 60 minutes, then rapidly solidify and form at a cooling rate of 30 - 100 °C / s to obtain the first aluminum alloy matrix of the core layer; (2)Intermediate layer preparation: Under an argon protection environment, place 0.1 - 0.2 wt% Er ingot, 0.1 - 0.3 wt% Yb ingot, 0.05 - 0.1 wt% Ce ingot, 0.35 - 0.6 wt% Mg ingot, 0.2 - 1.5 wt% Cu ingot, 0.1 - 2 wt% nano - SiC particles, 0.01 - 0.2 wt% graphene, and the balance Al ingot in a vacuum induction furnace according to the intermediate layer composition of the present invention. Control the melt temperature at 750 - 850 °C, and simultaneously perform ultrasonic dispersion treatment at 100 - 150 kHz / 500 W for 10 - 60 minutes, then rapidly solidify and form at a cooling rate of 30 - 100 °C / s to obtain the second aluminum alloy matrix of the intermediate layer; (3)Co - extrusion: Co - extrude the second aluminum alloy matrix of the intermediate layer and the first aluminum alloy matrix of the core layer at 450 - 580 °C, and the co - extrusion pressure is 80 - 120 MPa to form a co - extruded composite wire of the core layer and the intermediate layer; (4)Outer layer deposition: Perform plasma activation treatment on the surface of the composite wire with an Ar / O2 mixed gas, and then form a 1 - 5 μm SiC / graphene composite coating by plasma - enhanced chemical vapor deposition; thus obtaining the rare - earth aluminum alloy cable material described in the present invention.

[0009] In one of the schemes, in step (3), the second aluminum alloy matrix of the intermediate layer and the first aluminum alloy matrix of the core layer are co - extruded and compounded to form a composite structure with a thickness ratio H2 / H3 of 3:1 - 1:3.

[0010] In one of the schemes, in step (3), while co - extruding, apply a 1 - 2 T static magnetic field perpendicular to the co - extrusion direction to form a concentration gradient distribution of Er element from the core layer to the intermediate layer within each layer.

[0011] In one of the schemes, in step (4), it further includes a micro - arc oxidation treatment step to make the surface roughness Ra of the cable material 0.5 - 1.5 μm, specifically: Using a mixed electrolyte of sodium silicate - sodium phosphate (concentration 15 ± 5 g / L), the cable material is treated for 5 - 15 minutes under the conditions of pulsed current density of 6 - 10 A / dm², voltage of 150 - 200 V, and frequency of 500 - 1000 Hz. By controlling the arc discharge intensity at 1.2 - 2.5 V / μm, a microporous structure with a diameter of 2 - 5 μm is formed on the surface of the cable material. After being cleaned with deionized water and dried with hot air, the target roughness is obtained.

[0012] Moreover, the present invention also provides the application of the rare earth aluminum alloy cable material on transmission lines.

[0013] The beneficial effects of the present invention are as follows. Through the SiC / graphene composite coating by plasma enhanced chemical vapor deposition on the outer layer, and simultaneously forming a gradient distribution of rare earth aluminum alloy from the inside to the outside, the synergistic improvement of the dynamic fatigue performance, electromagnetic compatibility, and surface adhesion of the rare earth aluminum alloy cable material is achieved, while maintaining excellent comprehensive mechanical - electrical properties. Specifically: The SiC / graphene composite coating by plasma enhanced chemical vapor deposition on the outer layer forms a ceramic - like protective structure through nano - scale interface coupling. Among them, the two - dimensional network of graphene constructs a conductive channel at the SiC grain boundaries, reducing the surface sheet resistance to the order of 10 -4 Ω·cm. An electromagnetic shielding effectiveness of more than 60 dB can be achieved within the thickness range of 1 - 5 μm. At the same time, the dense SiC skeleton also has a good inhibitory effect on the penetration rate of corrosive media, and the comprehensive performance is significantly superior to the rare earth oxide film formed in the prior art.

[0014] The high Er content (0.5 - 0.6 wt%) in the core layer promotes the preferential orientation of the Al3Er precipitation phase along the <110> crystal direction, effectively improving the tensile strength. The decreasing gradient of the Er content in the intermediate layer (0.1 - 0.2 wt%) effectively alleviates the difference in the coefficient of thermal expansion between layers, avoiding dynamic fatigue caused by high - temperature thermal expansion in high - power transmission lines.

[0015] At the same time, graphene is mainly distributed in the outer layer and the intermediate layer rather than the core layer, which not only utilizes the coupling of its edge π - electron cloud with the sp³ hybrid orbit of SiC to enhance the interfacial bonding force, but also avoids the lattice distortion caused by excessive carbon elements in the core layer.

[0016] The nano - SiC particles are also uniformly dispersed in the intermediate layer and the core layer. In the core layer, they inhibit dislocation movement and improve the high - temperature creep resistance. In the intermediate layer, they jointly construct a multi - scale interface with graphene, forming a three - dimensional reinforcement network through the synergistic effect with rare earth elements, inhibiting the crack propagation caused by bending, and further improving the dynamic fatigue performance.

[0017] Furthermore, by implementing the micro-arc oxidation treatment step to control the surface roughness, micropores can be formed on the surface of the SiC / graphene composite coating, providing harder anchor points for the physical embedding of the outer skin, thereby further enhancing the bonding strength. Description of the Drawings

[0018] Figure 1 It is a schematic diagram of the overall cross-section of the cable material.

[0019] Figure 2 It is a cross-sectional view of the outer layer - intermediate layer of the cable material in Example 1.

[0020] Figure 3 It is a SEM image of the surface of the cable material in Example 1.

[0021] Figure 4 It is the radial Er / Si / C concentration distribution of the cable material in Example 1 along the material cross-section.

[0022] 1 - outer layer, 2 - intermediate layer, 3 - core layer. Detailed Embodiments

[0023] Although the present invention has been described to a certain extent, obviously, appropriate changes can be made to various conditions without departing from the spirit and scope of the present invention. It can be understood that the present invention is not limited to the described embodiments, but falls within the scope of the claims, which includes equivalent substitutions for each element described.

[0024] The terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality" means two or more unless otherwise specifically defined.

[0025] The present invention provides a rare earth aluminum alloy cable material, which, based on the total weight of the cable material, includes the following components: Er 0.3 - 0.6 wt%, Yb 0.1 - 0.3 wt%, Ce 0.05 - 0.15 wt%, Mg 0.35 - 0.5 wt%, Cu 0.2 - 1.5 wt%, nano - SiC particles 0.1 - 2.5 wt%, graphene 0.1 - 0.3 wt%, and the balance is Al and inevitable impurities. The cable material includes a three - layer structure, namely: The outer layer, which is a SiC / graphene composite coating formed by plasma - enhanced chemical vapor deposition, with an average thickness H1 of 1 - 5 μm. In this layer, no metal elements are contained; The intermediate layer, based on the total weight of this layer, includes the following components: Er 0.1 - 0.2 wt%, Yb 0.1 - 0.3 wt%, Ce 0.05 - 0.1 wt%, Mg 0.35 - 0.5 wt%, Cu 0.2 - 1.5 wt%, nano - SiC particles 0.1 - 2 wt%, graphene 0.01 - 0.2 wt%, and the balance is Al and unavoidable impurities; The core layer, based on the total weight of this layer, includes the following components: Er 0.5 - 0.6 wt%, Yb 0.1 - 0.3 wt%, Ce 0.1 - 0.15 wt%, Mg 0.35 - 0.5 wt%, Cu 0.2 - 1.5 wt%, nano - SiC particles 0.1 - 2 wt%, and the graphene content is less than 0.01 wt%, and the balance is Al and unavoidable impurities.

[0026] Here, "free of metal elements" means that the outer - layer metal elements are only impurities, and their content is trace, less than 0.01 wt%; "unavoidable impurities" means non - deliberately added elements that cannot be completely removed during the raw material and process. For the present invention, the impurities include Fe, O, and elemental Si, and their total content is less than 0.01 wt%.

[0027] In the present invention, the rare - earth aluminum alloy cable material is arranged in a radial distribution order as follows: the outer layer coats the intermediate layer, and the intermediate layer coats the core layer, forming a coaxial composite structure from the outside to the inside. The outer layer is directly attached to the outer surface of the intermediate layer through a plasma - enhanced chemical vapor deposition process, and its thickness direction is perpendicular to the axial direction of the cable material; the boundary between the intermediate layer and the core layer is defined by the following characteristics: ① Composition gradient mutation: The Er content in the core layer (0.5 - 0.6 wt%) shows a step - like increase compared with that in the intermediate layer (0.1 - 0.2 wt%); ② Graphene phase - distribution demarcation: The graphene content in the intermediate layer (0.01 - 0.2 wt%) and that in the core layer (<0.01 wt%) form an obvious phase - separation interface. It can be observed by scanning electron microscopy (SEM) combined with energy - dispersive spectroscopy (EDS) that the graphene content cannot be detected in the core layer.

[0028] In the present invention, the definitions and measurement methods of the average thickness H1 of the outer - layer coating, the average thickness H2 of the intermediate layer, and the average thickness H3 of the core layer are as follows (in accordance with the metal coating thickness measurement standard GB / T 6462 - 2005): H1 is defined as the radial thickness of the plasma - enhanced chemical vapor deposition layer perpendicular to the axial direction of the cable material. When measuring, the cross - section of the cable material is observed by scanning electron microscopy (SEM), and the arithmetic average of the thicknesses of at least 5 equally - spaced measurement points (interval angle 72°) is selected; H2 and H3 respectively refer to the thickness of the alloy matrix along the radial direction on the cross-section of the cable material for the intermediate layer and the core layer. After the samples are embedded with epoxy resin, mechanically polished and corroded with Keller reagent (2 mL HF + 3 mL HCl + 5 mL HNO3 + 190 mL H2O), they are observed with a metallurgical microscope, and the average value is taken after measuring along three directions of 0°, 120° and 240° with the center of the circle as the reference.

[0029] The cross-sectional schematic diagram of the cable material of the present invention is as Figure 1 shown, which can reflect the positional relationship between the outer layer 1, the intermediate layer 2 and the core layer 3 and their radial thicknesses.

[0030] In the present invention, the addition of Er can form an Al3Er strengthening phase with Al, refine the grains to be oriented along the <110> crystal direction and inhibit grain boundary slip, which can effectively improve the tensile strength and also significantly improve the dynamic fatigue performance; form high-melting-point compounds with Cu (such as Al-Er-Cu), reduce impurity segregation and improve electromagnetic compatibility. As a key technical point in the present invention, the content of Er in the core layer and the intermediate layer is different. The content in the core layer is 0.5-0.6 wt%, preferably 0.52-0.58 wt%, and further preferably 0.54-0.56 wt%. In the core layer, if the content of Er is less than 0.5 wt%, the precipitation of the Al3Er strengthening phase is insufficient, and the tensile strength and dynamic fatigue performance will decrease significantly; if it is higher than 0.6 wt%, brittle phases at the grain boundaries will be induced, reducing the fracture toughness. The content of Er in the intermediate layer is 0.1-0.2 wt%, preferably 0.12-0.18 wt%, and further preferably 0.14-0.16 wt%. In the intermediate layer, if the content of Er is less than 0.1 wt%, the grain boundary strengthening is insufficient, and the dislocation movement in the intermediate layer cannot be effectively inhibited, weakening the overall dynamic fatigue performance; if the content is higher than 0.2 wt%, excessive strengthening phases will cause interfacial stress concentration, reduce the interlayer bonding force and trigger crack propagation.

[0031] In the present invention, rare earth elements Yb and Ce are used as co-strengthening elements to optimize the performance. Yb forms an Al2Yb strengthening phase with Al in the core layer and the intermediate layer, significantly improving the heat resistance and creep resistance. Ce acts as a deoxidizer in the core layer to purify the melt and forms an Al4Ce strengthening phase to refine the grains, thereby enhancing the mechanical strength of the aluminum alloy; at the same time, it can also combine with Cu to form an Al-Cu-Ce compound, reducing the influence of impurity segregation on the conductivity; in the intermediate layer, it alleviates the difference in the coefficient of thermal expansion between layers through a gradient decreasing distribution, avoiding interface peeling. The content of Yb in the intermediate layer and the core layer is 0.1-0.3 wt%, preferably 0.15-0.25 wt%, and more preferably 0.18-0.22 wt%. The content of Ce in the intermediate layer is 0.05-0.1 wt%, preferably 0.06-0.09 wt%, and more preferably 0.07-0.08 wt%. The content of Ce in the core layer is 0.1-0.15 wt%, preferably 0.11-0.14 wt%, and more preferably 0.12-0.13 wt%.

[0032] In the present invention, the addition of metal Mg can reduce the surface tension of the aluminum melt at high temperatures and form a eutectic with low melting point with Al, reducing the extrusion temperature and extrusion pressure during co-extrusion. While avoiding high temperatures, it improves the extrusion efficiency. The addition of metal Cu can enhance the mechanical strength of the intermediate layer and the core layer and is beneficial to the improvement of the electrical conductivity. The content of Mg in the intermediate layer and the core layer is 0.35-0.5 wt%, preferably 0.38-0.45 wt%, and more preferably 0.4-0.42 wt%. The content of Cu in the intermediate layer and the core layer is 0.2-1.5 wt%, preferably 0.3-1.2 wt%, and more preferably 0.5-1.0 wt%.

[0033] In the present invention, the traditional rare earth oxide film is replaced by a SiC / graphene composite coating prepared by outer layer plasma enhanced chemical vapor deposition. While retaining the SiC skeleton that can inhibit the corrosion medium penetration rate below 10 -6 g / (m²·h), it also has properties that the rare earth oxide film does not have, that is, a ceramic-like protective structure is formed through nano-scale interface coupling. The two-dimensional network of graphene constructs a conductive channel at the SiC grain boundaries, reducing the surface sheet resistance to the order of 10 -4 Ω·cm and achieving an electromagnetic shielding effectiveness of more than 60 dB. To achieve the above effects, the SiC / graphene composite coating is formed by plasma enhanced chemical vapor deposition to a thickness of 1-5 μm, preferably 2-4 μm, and more preferably 2.5-3.5 μm.

[0034] In the present invention, graphene and SiC can also be distributed in an intermediate layer with aluminum alloy as the main matrix. A multi-scale interface is constructed jointly by SiC and graphene, and a three-dimensional reinforcement network is formed through the synergistic effect with rare earth elements, which inhibits crack propagation caused by bending. At the interface between the intermediate layer and the outer layer, the coupling of the π electron cloud at the edge of graphene and the sp³ hybrid orbitals of SiC can enhance the interfacial bonding force, ensuring the bonding effect of plasma-enhanced chemical vapor deposition. And through repeated experiments, it is proved that when graphene is basically absent in the core layer, the mechanical strength, such as the tensile strength, is higher than that when graphene is present. A logical speculation is that the content of rare earth elements in the core layer is relatively high, forming Re-Al strengthened phase grains with Al. When graphene particles appear, it causes lattice distortion of the strengthened phase grains, thereby affecting the mechanical strength of the core layer.

[0035] Regarding the content, in the core layer and the intermediate layer, the content of nano-SiC particles is 0.1 - 2.5 wt%, preferably 0.5 - 2.0 wt%, and further preferably 0.8 - 1.5 wt%. If the content of nano-SiC particles is lower than 0.1 wt%, the tensile strength and dynamic fatigue performance will decrease significantly. When the content of nano-SiC particles is higher than 2.5 wt%, there is insufficient grain boundary strengthening and the conductivity decreases. In the core layer, the content of graphene is less than 0.01 wt%, existing in an almost non-existent situation. Therefore, it is also necessary to control the co-extrusion pressure and temperature to prevent it from diffusing from the second aluminum alloy matrix in the intermediate layer to the first aluminum alloy matrix layer in the core layer. In the intermediate layer, the content of graphene is 0.1 - 2 wt%, preferably 0.2 - 1.5 wt%, and further preferably 0.5 - 1.2 wt%. If the content of graphene is lower than 0.1 wt%, the bonding force between the outer layer and the intermediate layer cannot be guaranteed, and at the same time, the tensile strength and dynamic fatigue performance also decrease; if it is higher than 2.0 wt%, it will also cause brittle phases at the grain boundaries, reducing the fracture toughness.

[0036] After the components and contents of each layer are limited, the overall composition of the rare earth aluminum alloy cable is as follows: based on the total weight of the cable material, it includes the following components: Er 0.3-0.6wt%, Yb 0.1-0.3wt%, Ce 0.05-0.15wt%, Mg 0.35-0.5wt%, Cu 0.2-1.5wt%, nano-SiC particles 0.1-2.5wt%, graphene 0.1-0.3wt%, and the balance is Al and unavoidable impurities; preferably, Er 0.35-0.4wt%, Yb 0.15-0.25wt%, Ce 0.08-0.13wt%, Mg 0.38-0.45wt%, Cu 0.3-1.2wt%, nano-SiC particles 0.3-2wt%, graphene 0.15-0.25wt%, and the balance is Al and unavoidable impurities; more preferably, Er 0.4-0.45wt%, Yb 0.18-0.22wt%, Ce 0.1-0.12wt%, Mg 0.4-0.42wt%, Cu 0.5-1.0wt%, nano-SiC particles 0.5-1.5wt%, graphene 0.18-0.22wt%, and the balance is Al and unavoidable impurities.

[0037] In one preferred embodiment of the present invention, the ratio H2 / H3 of the average thickness H2 of the intermediate layer to the average thickness H3 of the core layer is 3:1-1:3. By controlling the thickness ratio, the flow stresses of the two layers of materials can be balanced during hot extrusion, avoiding interface instability caused by excessive thickness differences, such as core layer bulging or intermediate layer tearing, and achieving a stable gradient composition distribution. By reasonably designing the thickness of the intermediate layer, the concentration of thermal expansion stress can also be alleviated, thereby improving the dynamic fatigue life.

[0038] In one preferred embodiment of the present invention, the surface roughness Ra of the cable material shown is 0.5-1.5μm, preferably Ra = 0.7-1.3μm, and more preferably Ra = 0.8-1.2μm. By forming a SiC / graphene composite coating with a certain surface roughness, harder anchor points are provided, enabling the cable material outer skin (such as the cable insulation protection skin) to physically embed, thereby further enhancing the bonding strength.

[0039] The present invention also discloses a preparation method of the rare earth aluminum alloy cable material of the present invention, including the following steps: (1)Preparation of the core layer: Under an argon protection environment, place Er ingots, Yb ingots, Ce ingots, Mg ingots, Cu ingots, nano-SiC particles, and the remaining Al ingots in a vacuum induction furnace for melting according to the core layer composition mentioned above in the present invention. Control the melt temperature at 750 - 850 °C, preferably 780 - 830 °C. At the same time, perform ultrasonic dispersion treatment at 100 - 150 kHz / 500 W, preferably 110 - 140 kHz / 500 W for 10 - 60 minutes, preferably 20 - 50 minutes. Then, rapidly solidify and form at a cooling rate of 30 - 100 °C / s, preferably 50 - 80 °C / s, to obtain the first aluminum alloy matrix of the core layer; (2)Preparation of the intermediate layer: Under an argon protection environment, place Er ingots, Yb ingots, Ce ingots, Mg ingots, Cu ingots, nano-SiC particles, graphene, and the remaining Al ingots in a vacuum induction furnace for melting according to the intermediate layer composition of the present invention. The temperature is preferably 780 - 830 °C. At the same time, perform ultrasonic dispersion treatment at 100 - 150 kHz / 500 W, preferably 110 - 140 kHz / 500 W for 10 - 60 minutes, preferably 20 - 50 minutes. Then, rapidly solidify and form at a cooling rate of 30 - 100 °C / s, preferably 50 - 80 °C / s, to obtain the second aluminum alloy matrix of the intermediate layer; (3)Co-extrusion: Co-extrude the second aluminum alloy matrix of the intermediate layer and the first aluminum alloy of the core layer at 450 - 580 °C, preferably 480 - 550 °C. The co-extrusion pressure is 80 - 120 MPa, preferably 90 - 110 MPa, to form a co-extruded composite wire of the core layer and the intermediate layer; (4)Outer layer deposition: Perform plasma activation treatment on the surface of the composite wire with a mixed gas of Ar / O2. Subsequently, form a SiC / graphene composite coating with a thickness of 1 - 5 μm through plasma-enhanced chemical vapor deposition; preferably 2 - 4 μm, more preferably 2.5 - 3.5 μm, thereby obtaining the rare earth aluminum alloy cable material described in the present invention.

[0040] In the present invention, nano-SiC particles (50 - 200 nm) are prone to agglomeration in the aluminum melt, and it is difficult to achieve uniform dispersion by traditional stirring. By using ultrasonic waves at 100 - 150 kHz / 500 W to generate microbubbles in the melt, local high temperature and high pressure are released when the bubbles burst, thereby enabling the fragmentation of particle agglomerates in a high-viscosity melt; The cooling rate is set at 30 - 100 °C / s, which can affect the size and distribution of the Re-Al strengthening phase grains. Too fast is likely to cause cracks, and too slow will result in grain coarsening.

[0041] Set the process conditions for co-extrusion at 450 - 580 °C / 80 - 120 MPa. If the temperature is too low or the pressure is too high, the flow stress difference is large, which easily leads to interface instability; if the temperature is too high, the interface diffusion effect is obvious, resulting in insufficient tensile strength after forming, and if the pressure is too small, the co-extrusion efficiency is low.

[0042] In one preferred embodiment of the present invention, in step (3), the second aluminum alloy matrix of the intermediate layer and the first aluminum alloy matrix of the core layer are co-extruded and compounded to form a composite structure with a thickness ratio H2 / H3 of 3:1 - 1:3.

[0043] In one preferred embodiment of the present invention, in step (3), while co-extruding, a static magnetic field of 1 - 2 T is applied perpendicular to the co-extrusion direction, so that the Er element forms a concentration gradient distribution within each layer from the core layer to the intermediate layer. This gradient distribution can avoid dynamic fatigue caused by high-temperature thermal expansion, reduce the possibility of crack generation, and improve the overall mechanical stability of the cable material.

[0044] In one preferred embodiment of the present invention, in step (4), a micro-arc oxidation treatment step is further included to make the surface roughness Ra of the cable material 0.5 - 1.5 μm, preferably Ra = 0.7 - 1.3 μm, and more preferably Ra = 0.8 - 1.2 μm. Specifically: Using a mixed electrolyte of sodium silicate - sodium phosphate (concentration 15 ± 5 g / L), treating the cable material for 5 - 15 minutes under the conditions of a pulsed current density of 6 - 10 A / dm², a voltage of 150 - 200 V, and a frequency of 500 - 1000 Hz. By controlling the arc discharge intensity at 1.2 - 2.5 V / μm, a microporous structure with a diameter of 2 - 5 μm, preferably 2.5 - 4.5 μm, and more preferably 3 - 4 μm is formed on the surface of the cable material. After being washed with deionized water and dried with hot air, the target roughness is obtained.

[0045] The present invention also provides the application of the rare earth aluminum alloy cable material on transmission lines. Due to the excellent dynamic fatigue performance, electromagnetic shielding resistance, and chemical corrosion resistance of the rare earth aluminum alloy cable material of the present invention, it can be used in transmission lines in areas with high electromagnetic interference, frequent typhoons, and humid and hot climates.

[0046] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with examples. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0047] Example 1 ① Preparation of the core layer: Based on a total weight of 100 kg, 0.55 kg of Er ingot, 0.2 kg of Yb ingot, 0.13 kg of Ce ingot, 0.41 kg of Mg ingot, 0.8 kg of Cu ingot, 1.2 kg of nano-SiC particles (50 - 200 nm), and 96.71 kg of Al ingot are melted in a vacuum induction furnace under argon protection. The melt temperature is controlled at 800 °C, ultrasonic dispersion is carried out at 140 kHz / 500W for 40 minutes, and then rapid solidification is carried out at a cooling rate of 70 °C / s to obtain the core layer matrix.

[0048] ② Preparation of the intermediate layer: Based on a total weight of 100 kg, 0.15 kg of Er ingot, 0.2 kg of Yb ingot, 0.08 kg of Ce ingot, 0.41 kg of Mg ingot, 0.8 kg of Cu ingot, 1.0 kg of nano-SiC particles, 0.5 kg of graphene, and 96.86 kg of Al ingot are melted in a vacuum induction furnace under argon protection. The melt temperature is controlled at 800 °C, ultrasonic dispersion is carried out at 140 kHz / 500W for 40 minutes, and then rapid solidification is carried out at a cooling rate of 70 °C / s to obtain the intermediate layer matrix.

[0049] ③ Co-extrusion: The core layer and the intermediate layer matrix are preheated to 520 °C and co-extruded under a pressure of 100 MPa with the assistance of a 1.5T vertical static magnetic field, and the thickness ratio H2 / H3 = 1:1 (5 mm each) is controlled.

[0050] ④ Outer layer deposition: After the co-extruded wire is activated by Ar / O2 plasma, a 3 μm thick SiC / graphene composite coating (22.5 g of nano-SiC particles and 7.5 g of graphene) is deposited by PECVD with a flow ratio of SiH4 / CH4 = 3:1. Finally, a pulse voltage of 180V is applied in a sodium silicate - sodium phosphate electrolyte (15 g / L) for 10 minutes to form a SiC / graphene composite coating with a surface roughness Ra = 1.1 μm.

[0051] In Example 1, the SEN diagram of the outer layer - intermediate layer cross-section of the cable material is as Figure 2 shown, and the SEM diagram of the cable material surface is as Figure 3 shown. The radial Er / Si / C concentration distribution in the middle cross-section of the cable material is quantitatively detected based on scanning electron microscopy - energy dispersive spectrometer, as Figure 4 shown.

[0052] Example 2 Compared with Example 1, the Er ingot in the core layer is adjusted to 0.6 kg, and the Er ingot in the intermediate layer is adjusted to 0.12 kg, and the Al ingot content in each layer is adjusted accordingly to make the total weight of each layer 100 kg. Other conditions remain unchanged.

[0053] Example 3 Compared with Example 1, the graphene in the intermediate layer was adjusted to 1.5 kg, the nano-SiC particles were adjusted to 0.5 kg, and the content of Al ingots in the intermediate layer was adaptively adjusted to 96.86 kg. Other conditions remained unchanged.

[0054] Example 4 Compared with Example 1, the nano-SiC particles in the core layer were adjusted to 0.5 kg, the nano-SiC particles in the intermediate layer were adjusted to 0.5 kg, the graphene was adjusted to 0.1 kg, the core layer Al ingots were adjusted to 97.41 kg, and the intermediate layer Al ingots were adjusted to 97.36 kg. Other conditions remained unchanged.

[0055] Example 5 Compared with Example 1, a static magnetic field of 2 T was applied during co-extrusion, the co-extrusion temperature was adjusted to 550 °C, and the pressure was adjusted to 110 MPa. Other conditions remained unchanged.

[0056] Example 6 Compared with Example 1, the micro-arc oxidation voltage was adjusted to 200 V, and the treatment time was extended to 15 minutes to make the surface roughness Ra of the coating = 1.5 μm. Other conditions remained unchanged.

[0057] Example 7 Compared with Example 1, the Yb ingots in the core layer were adjusted to 0.25 kg, the Ce ingots were adjusted to 0.14 kg, and the Al ingots in the core layer were adaptively adjusted to 96.36 kg; the Yb ingots in the intermediate layer were adjusted to 0.25 kg, the Ce ingots were adjusted to 0.08 kg, and the intermediate layer Al ingots were adjusted to 96.27 kg. Other conditions remained unchanged.

[0058] Example 8 Compared with Example 1, the co-extrusion pressure was adjusted to 120 MPa, and the cooling rate was adjusted to 100 °C / s. Other conditions remained unchanged.

[0059] Example 9 Compared with Example 1, the Er ingots in the core layer were adjusted to 0.56 kg, the Yb ingots were adjusted to 0.2 kg, the Ce ingots were adjusted to 0.12 kg, the nano-SiC particles were adjusted to 1.5 kg, and the Al ingots in the core layer were adaptively adjusted to 96.62 kg; the Er ingots in the intermediate layer were adjusted to 0.14 kg, the graphene was adjusted to 0.18 kg, and the intermediate layer Al ingots were adjusted to 96.28 kg; the outer layer coating was adjusted to 2.5 μm. Other conditions remained unchanged.

[0060] Example 10 Compared with Example 1, no static magnetic field was applied during co-extrusion. Other conditions remained unchanged.

[0061] Example 11 Compared with Example 1, the micro-arc oxidation step is cancelled, and the surface roughness Ra = 0.2 μm. Other conditions remain unchanged.

[0062] Comparative Example 1 Compared with Example 1, the Er ingots in the core layer and the intermediate layer are both adjusted to 0.3 kg, and the Al ingots in the core layer and the intermediate layer are adaptively adjusted to 97.05 kg. Other conditions remain unchanged.

[0063] Comparative Example 2 Compared with Example 1, no Er ingots are added to the core layer and the intermediate layer, and the Al ingots in the core layer and the intermediate layer are adaptively adjusted to 97.35 kg. Other conditions remain unchanged.

[0064] Comparative Example 3 Compared with Example 1, 0.05 kg of graphene is added to the core layer, and the Al ingot in the core layer is adaptively adjusted to 96.66 kg. Other conditions remain unchanged.

[0065] Comparative Example 4 Compared with Example 1, the co-extrusion thickness ratio is adjusted to H2 / H3 = 5:1 (intermediate layer 8.3 mm, core layer 1.7 mm). Other conditions remain unchanged.

[0066] Comparative Example 5 Compared with Example 1, the addition of Yb and Ce is cancelled in the core layer and the intermediate layer, and only the Er ingot is retained. The Al ingot in the core layer is adaptively adjusted to 98.85 kg, and the Al ingot in the intermediate layer is 98.85 kg. Other conditions remain unchanged.

[0067] Comparative Example 6 Compared with Example 1, the outer coating thickness is adjusted to 8 μm (including 60 g of SiC and 20 g of graphene). Other conditions remain unchanged.

[0068] Comparative Example 7 Compared with Example 1, the co-extrusion temperature is adjusted to 430 °C, and the co-extrusion pressure is adjusted to 140 MPa. Other conditions remain unchanged.

[0069] Comparative Example 8 Compared with Example 1, the co-extrusion temperature is adjusted to 600 °C, and the co-extrusion pressure is adjusted to 60 MPa. Other conditions remain unchanged.

[0070] Comparative Example 9 Compared with Example 1, only the surface of the composite wire is treated with a plasma of an Ar / O2 mixed gas for 10 min to form a dense layer of certain Al and Re oxides, and no subsequent plasma-enhanced chemical vapor deposition of the SiC / graphene composite coating is carried out. Other conditions remain unchanged.

[0071] Comparative Example 10 Compared with Example 1, no nano-SiC particles are added to the core layer and the intermediate layer, and the Al ingots in the core layer are adjusted to 98.71 kg and the Al ingots in the intermediate layer are adjusted to 98.86 kg adaptively. Other conditions remain unchanged.

[0072] Reserve the rare earth aluminum alloy cable materials obtained in Examples 1-11 and Comparative Examples 1-10 for performance tests in terms of tensile strength, electrical conductivity, dynamic fatigue times, electromagnetic shielding effectiveness, salt spray corrosion rate, and the bonding force between the outer layer of the cable wire and the insulating material.

[0073] <Test Method> - Tensile Strength According to the basic process and parameter requirements of GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Method of test at room temperature", apply axial tension to the cable material specimen by a universal material testing machine until fracture, and record the maximum load and the original cross-sectional area to calculate the tensile strength (unit: MPa). - Electrical Conductivity According to the eddy current detection process of the electrical conductivity of aluminum alloy conductors specified in GB / T 12966-2022 "Eddy current test method for electrical conductivity of aluminum and aluminum alloys", use an eddy current conductivity meter to measure the electrical conductivity of the cable conductor (unit: %IACS), and evaluate the electrical conductivity performance by comparing with the electrical conductivity of standard copper (100% IACS).

[0074] - Dynamic Fatigue Times Cut a 20-cm long sample cable material with a shaft diameter of 1 cm, fix the midpoint, and repeatedly bend both ends by 90° through a high-power bending testing machine, and calculate the number of bends at fracture.

[0075] - Electromagnetic Shielding Effectiveness Cut a 1.2-m long sample cable material with a shaft diameter of 1 cm, and conduct tests according to the test process specified in GJB 6190-2008 "Test method for electromagnetic shielding performance of cables".

[0076] - Bonding Force between the Outer Layer of the Cable Material and the Insulating Material According to the test method of the cable sheath adhesion test (Sheath Adherence Test) in Section 31 of ASTM D4565-20, use a universal material testing machine equipped with a ring fixture for testing, where the peeling speed is 50 mm / min.

[0077] Peeling strength (N / mm) = average peeling force (N) / wire circumference (mm).

[0078] - Salt Spray Corrosion Rate According to the test process specified in GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test", a salt spray test chamber is used to simulate the marine or industrial corrosion environment. The neutral salt spray test (NSS) is adopted to evaluate the corrosion rate of cable materials, observe the surface state of the coating, and record the time when red rust appears on the sample panel.

[0079] <Test Results> The test results of Examples 1-11 and Comparative Examples 1-10 are shown in the following table:

[0080] It can be seen from the data of the above examples and comparative examples that the performance of each item in the examples is good. By comparing with the comparative examples, it can be known that the presence or absence, content change of key elements, and adjustment of process links will have obvious effects on the tensile strength, conductivity, dynamic fatigue times, electromagnetic shielding effectiveness, salt spray corrosion situation, and the bonding force between the outer layer and the insulating material of the cable material. Examples 1-11 achieve the balanced optimization of various performances. In Comparative Example 1, there is no difference in the Er concentration in the core layer and the intermediate layer. In Comparative Example 2, Er is not added. In Comparative Example 3, graphene is added to the core layer. In Comparative Example 4, the thickness ratio is unbalanced. In Comparative Example 5, Yb / Ce is not added. In Comparative Example 6, a thicker SiC / graphene coating is used. In Comparative Examples 7 and 8, the co-extrusion process settings are changed. In Comparative Example 9, there is no SiC / graphene coating. In Comparative Example 10, nano-SiC particles are not added. All of the above result in the inability to simultaneously meet the tensile strength, conductivity, dynamic fatigue times, electromagnetic shielding effect, and corrosion resistance.

[0081] Further, Examples 10 and 11 also show that the control of surface roughness and the application of a static magnetic field during the co-extrusion process further promote the improvement of the overall effect.

[0082] It should be noted that this specific embodiment is only an explanation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications without creative contributions to this embodiment as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A rare earth aluminum alloy cable material, characterized in that: Based on the total weight of the cable material, the following components are included: Er 0.3-0.6wt%, Yb 0.1-0.3wt%, Ce 0.05-0.15wt%, Mg 0.35-0.5wt%, Cu 0.2-1.5wt%, nano-SiC particles 0.1-2.5wt%, graphene 0.1-0.3wt%, and the balance is Al and unavoidable impurities. The cable material includes a three-layer structure, which are: The outer layer is a SiC / graphene composite coating deposited by plasma enhanced chemical vapor deposition, with an average thickness H1 of 1-5 μm, and no metal element is contained in the layer; The middle layer, based on the total weight of the layer, comprises the following components: Er 0.1-0.2wt%, Yb 0.1-0.3wt%, Ce 0.05-0.1wt%, Mg 0.35-0.5wt%, Cu 0.2-1.5wt%, nano-SiC particles 0.1-2wt%, graphene 0.01-0.2wt%, and the balance is Al and unavoidable impurities; The core layer comprises the following components, based on the total weight of the layer: Er 0.5-0.6wt%, Yb 0.1-0.3wt%, Ce 0.1-0.15wt%, Mg 0.35-0.5wt%, Cu 0.2-1.5wt%, nano-SiC particles 0.1-2wt%, graphene content less than 0.01wt%, and the balance Al and unavoidable impurities.

2. The rare earth aluminum alloy cable material according to claim 1, characterized in that: The ratio H2 / H3 of the average thickness H2 of the intermediate layer to the average thickness H3 of the core layer is 3:1-1:

3.

3. The rare earth aluminum alloy cable material according to claim 1, characterized in that: The surface roughness of the cable material is Ra=0.5-1.5μm.

4. The method for preparing a rare earth aluminum alloy cable material according to claim 1, characterized in that: The following steps are involved: (1) Preparation of core layer: Under argon protection environment, 0.5-0.6wt% Er ingot, 0.1-0.3wt% Yb ingot, 0.1-0.15wt% Ce ingot, 0.35-0.6wt% Mg ingot, 0.2-1.5wt% Cu ingot, 0.1-2wt% nano-SiC particles and the remaining Al ingot are placed in a vacuum induction furnace for melting according to the composition of the core layer, and the melt temperature is controlled to be 750-850°C. At the same time, ultrasonic dispersion treatment is performed at 100-150kHz / 500W for 10-60 minutes, and then rapid solidification is performed at a cooling rate of 30-100°C / s to obtain a first aluminum alloy matrix of the core layer; (2) Preparation of intermediate layer: Under argon protection environment, 0.1-0.2wt% Er ingot, 0.1-0.3wt% Yb ingot, 0.05-0.1wt% Ce ingot, 0.35-0.6wt% Mg ingot, 0.2-1.5wt% Cu ingot, 0.1-2wt% nano-SiC particles, 0.01-0.2wt% graphene and the remaining Al ingot are placed in a vacuum induction furnace for melting according to the composition of the intermediate layer, and the melt temperature is controlled to be 750-850°C. At the same time, ultrasonic dispersion treatment is carried out at 100-150kHz / 500W for 10-60 minutes, and then rapid solidification is carried out at a cooling rate of 30-100°C / s to obtain a second aluminum alloy matrix of the intermediate layer; (3) Co-extrusion: The second aluminum alloy matrix of the middle layer and the first aluminum alloy matrix of the core layer are co-extruded at 450-580°C and the co-extrusion pressure is 80-120 MPa to form a co-extruded composite wire of the core layer and the middle layer; (4) Outer layer deposition: The surface of the composite wire is subjected to plasma activation treatment with an Ar / O2 mixed gas, and then a 1-5 μm SiC / graphene composite coating is formed by plasma enhanced chemical vapor deposition, thereby obtaining the rare earth aluminum alloy cable material.

5. The preparation method according to claim 4, characterized in that: In step (3), the second aluminum alloy matrix of the intermediate layer and the first aluminum alloy matrix of the core layer are co-extruded and composited to form a composite structure with a thickness ratio H2 / H3 of 3:1-1:

3.

6. The preparation method according to claim 4, characterized in that: In step (3), a static magnetic field of 1-2 T is applied perpendicular to the co-extrusion direction during co-extrusion, so that the Er element forms a concentration gradient distribution in each layer from the core layer to the middle layer.

7. The preparation method according to claim 4, characterized in that: In step (4), a micro-arc oxidation treatment step is also included to make the surface roughness of the cable material Ra = 0.5-1.5 μm, specifically: The cable material is treated with a sodium silicate-sodium phosphate mixed electrolyte with a concentration of 15±5g / L for 5-15 minutes under the conditions of a pulse current density of 6-10A / dm², a voltage of 150-200V, and a frequency of 500-1000Hz. By controlling the arc discharge intensity at 1.2-2.5V / μm, a microporous structure with a diameter of 2-5μm is formed on the surface of the cable material. The target roughness is obtained after washing with deionized water and drying with hot air.

8. Use of the rare earth aluminum alloy cable material according to any one of claims 1 to 3 in transmission lines.

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