A gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material and a production method thereof

Abstract

The application discloses a kind of gradient composite modified marine corrosion-resistant aluminum alloy cable conductor materials and production method thereof, belong to wire and cable material technical field.The method includes: in 6 or 7 aluminum alloy matrix, add 0.1%~0.5% rare earth element yttrium, cerium and 0.05%~0.2% zirconium, titanium carries out multielement microalloying, adds 1.5%~2.5% zinc and 0.5%~1.0% magnesium constructs sacrificial anode phase, dopes 1.5%~2.5% nano graphene oxide / nanosilicon carbide fills micro-pore;Conductor surface layer is treated by chromium-free passivation by titanium zirconium composite passivation solution, and then the inorganic-organic gradient coating of "silicon oxide-aluminum oxide ceramic bottom layer+fluorocarbon resin surface layer" is constructed;By component segregation control, the core-surface dual-function gradient structure of core high-conductivity aluminum alloy matrix and surface corrosion-resistant strengthening layer is formed.The application is significantly improved by multidimensional composite modification design, the corrosion resistance and long-term service life of aluminum alloy cable conductor in marine high-salt fog environment, conductivity is greater than or equal to 62% IACS, no visible corrosion in salt spray 2000h, service life is more than 30 years.

Description

Technical Field

[0001] This invention belongs to the field of wire and cable materials technology, specifically relating to a gradient composite modified aluminum alloy cable conductor material for use in marine environments with high salt spray corrosion and its production method. Background Technology

[0002] As human exploitation of marine resources deepens, the scale of marine infrastructure projects such as marine engineering, offshore wind power, offshore oil platforms, cross-sea bridges, and island power transmission continues to expand, placing increasingly higher demands on the performance of power cables used in marine environments. Power cables are a key component of the electrical systems in marine engineering, undertaking the tasks of transmitting and distributing electrical energy; their quality and reliability directly affect the safe operation of the entire marine engineering project.

[0003] Aluminum alloy cables, due to their advantages such as light weight (approximately 30% of copper cables), low cost, abundant resources, and excellent conductivity, have become an important alternative to copper cables and are widely used in land-based power transmission. However, in the high-salt-spray corrosive environment of the ocean, aluminum alloy cables face severe corrosion challenges. The marine atmosphere contains a large amount of chloride ions (Cl... - High salt spray concentration and high humidity make aluminum alloys highly susceptible to corrosion failures such as pitting corrosion, intergranular corrosion, and stress corrosion cracking.

[0004] The corrosion mechanism of aluminum alloys mainly includes the following aspects: First, the naturally formed oxide film on the surface of aluminum alloys is easily destroyed by chloride ion erosion. In air, aluminum alloys naturally form a dense alumina (Al2O3) passivation film approximately 2-10 nm thick, which can protect the aluminum alloy matrix to a certain extent. However, when aluminum alloys are exposed to a chloride-rich marine environment, chloride ions can adsorb and penetrate the defects in the oxide film, causing localized dissolution and rupture, exposing the active aluminum alloy matrix, thus initiating an electrochemical corrosion reaction. Second, a potential difference exists between the second-phase particles (such as Al2Cu phase, Al-Fe-Si phase, etc.) in the aluminum alloy and the aluminum matrix, forming a micro-cell effect in the corrosive medium, accelerating the occurrence and development of localized corrosion. Furthermore, residual stress and microstructural inhomogeneity are generated in aluminum alloy conductors during manufacturing and processing, which also increase their corrosion susceptibility.

[0005] Currently, the main technical approaches to improving the corrosion resistance of aluminum alloy materials include the following aspects:

[0006] (1) Alloy composition optimization. Adding appropriate amounts of alloying elements (such as magnesium, silicon, copper, zinc, manganese, zirconium, etc.) can improve the microstructure and corrosion potential distribution of aluminum alloys. For example, the Mg2Si strengthening phase formed by adding magnesium and silicon can improve the mechanical properties of aluminum alloys, but it also affects corrosion behavior. Adding copper can improve the strength of aluminum alloys, but excessive copper will form the Al2Cu phase, creating a large potential difference with the aluminum matrix and reducing corrosion resistance. CN101033552A, "Double-layer aluminum alloy composite sacrificial anode," describes how adding zinc can form a sacrificial anode phase in aluminum alloys, providing cathodic protection; however, excessive zinc addition will significantly reduce the conductivity of the aluminum alloy.

[0007] (2) Rare Earth Microalloying. CN116287815B, "Modifiers and Grain Refiners for Al-Si Die-cast Aluminum Alloys and Their Preparation Methods," describes how adding trace amounts of rare earth elements (such as cerium, lanthanum, yttrium, and scandium) to aluminum alloys can significantly improve their microstructure and overall properties. Rare earth elements have unique electronic structures and mainly play the following roles in aluminum alloys: refining grains, purifying the melt, changing the morphology and distribution of the second phase, and inhibiting recrystallization. Rare earth elements can form stable compounds with impurity elements such as hydrogen and oxygen, reducing the gas content and harmful impurity content in the melt, thereby improving the purity of the alloy. At the same time, the segregation of rare earth elements at grain boundaries can inhibit grain boundary corrosion. However, the amount of rare earth elements added to aluminum alloys, the method of addition, and the interaction with other alloying elements still need further research.

[0008] (3) Surface Coating Protection. Applying organic or inorganic protective coatings to the surface of aluminum alloys is an effective way to improve their corrosion resistance. Organic coatings, such as epoxy resin, polyurethane, and fluorocarbon resin, have excellent weather resistance and chemical resistance, and can effectively block the contact between corrosive media and the substrate. However, the disadvantages of organic coatings are low hardness, poor wear resistance, and easy aging and peeling. Inorganic coatings, such as alumina, silicon oxide, and zirconium oxide ceramic coatings, have high hardness, high wear resistance, and good chemical stability, but they are brittle and have insufficient adhesion. A single organic or inorganic coating is difficult to meet the comprehensive performance requirements of the marine environment for cable conductors.

[0009] (4) Surface passivation treatment. Chromate passivation is a mature technology traditionally used for the surface treatment of aluminum alloys. It can form a dense chromate conversion film on the surface of aluminum alloys, significantly improving the corrosion resistance and coating adhesion of aluminum alloys. However, the chromate passivation film contains hexavalent chromium (Cr). 6+Chromium-free passivation technology, characterized by its strong carcinogenicity and serious environmental pollution, has been restricted or banned by the EU RoHS Directive, REACH Regulation, and relevant environmental regulations in China. Developing environmentally friendly chromium-free passivation technology is an urgent need in the field of aluminum alloy surface treatment. CN102776501A, "A Chromium-Free Passivation Method and Chromium-Free Passivation Solution for Aluminum and Aluminum Alloys," describes titanium-zirconium-based chromium-free passivation technology, which has attracted widespread attention due to its environmental friendliness and promising industrial application prospects. However, the corrosion resistance of titanium-zirconium passivation films currently cannot fully reach the level of chromate passivation films, and the coating adhesion needs improvement.

[0010] Although existing technologies have made some research and improvements on the corrosion resistance of aluminum alloy materials, the following technical problems still urgently need to be solved regarding aluminum alloy cable conductor materials used in high-salt-spray marine environments:

[0011] First, the aluminum alloy matrix itself has insufficient corrosion resistance. Although traditional 6-series and 7-series aluminum alloys have good mechanical and electrical properties, the distribution of second-phase particles formed by impurity elements such as Fe and Cu at the grain boundaries leads to high susceptibility to intergranular corrosion, making them prone to intergranular corrosion and exfoliation corrosion in marine salt spray environments.

[0012] Second, the surface coating system has poor adhesion and is prone to peeling. The interfacial bonding between a single organic or inorganic coating and the aluminum alloy substrate is weak, and the coating is prone to cracking or peeling under service conditions such as cable bending, temperature changes, and mechanical vibration, thus losing its protective function.

[0013] Third, the trade-off between electrical conductivity and corrosion resistance is difficult to reconcile. Improving the corrosion resistance of aluminum alloys usually requires adding more alloying elements or using complex surface treatment processes, but these measures often reduce the electrical conductivity of aluminum alloys, making it difficult to achieve excellent corrosion resistance while maintaining high conductivity.

[0014] Fourth, environmental constraints. While traditional chromate passivation is effective, its use has been restricted due to the environmental pollution caused by hexavalent chromium. Existing chromium-free passivation technologies are not yet ideal in performance and cannot meet the high corrosion resistance requirements of marine environments.

[0015] Fifth, the performance requirements of the core and the outer layer have not been specifically addressed in the design. During use, the core of the cable conductor needs to meet the requirement of high conductivity, while the outer layer needs to have excellent corrosion resistance. Traditional homogeneous material designs cannot simultaneously meet the different performance requirements of the core and the outer layer.

[0016] Therefore, developing an aluminum alloy cable conductor material with high conductivity, excellent marine corrosion resistance, and good environmental performance, as well as its efficient production method, is of great practical significance and has broad market prospects for meeting the urgent needs of marine engineering construction. Summary of the Invention

[0017] This invention addresses the problems of insufficient corrosion resistance, difficulty in balancing conductivity and corrosion resistance, poor coating adhesion, and environmental pollution caused by traditional chromate passivation in existing aluminum alloy cable conductor materials under high salt spray marine environments. It provides a gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material and its production method.

[0018] To achieve the above objectives, the present invention adopts the following technical solution:

[0019] A method for producing a gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material includes the following steps:

[0020] (1) Weigh the raw materials according to the following weight percentages: silicon 0.35%~0.55%, iron 0.20%~0.40%, total magnesium content 0.9%~1.6%, of which 0.4%~0.6% is used to form the Mg2Si strengthening phase and 0.5%~1.0% is added as a supplement to the sacrificial anode phase, copper 0.02%~0.08%, rare earth elements 0.10%~0.50%, of which the rare earth elements are a combination of yttrium and cerium with a mass ratio of 1:1~3:1, zirconium 0.05%~0.15%, titanium 0.05%~0.12%, zinc 1.5%~2.5%, nano graphene oxide 0.5%~1.0%, nano silicon carbide 0.5%~1.0%, and the mass ratio of the two is 1:1~2:1, the total addition amount of the two is 1.5%~2.5%, and boron 0.01%~0.05%, with aluminum as the balance;

[0021] (2) Preparation of composite additives;

[0022] (3) The aluminum, silicon, iron, magnesium, copper, rare earth elements, zirconium, titanium, zinc and boron weighed in step (1) are put into a melting furnace and melted at a temperature of 740~760℃. At the same time, the nanocomposite additives prepared in step (2) are added. Electromagnetic stirring is applied during the melting process, and the melting is fully carried out for 60~120 minutes to obtain the alloy melt.

[0023] (4) Refining the alloy melt: Argon purging and degassing, refining agent slag removal and vacuum degassing are performed in sequence. The melt is allowed to stand for 30-60 minutes and the hydrogen content in the melt is controlled to be less than 0.15 mL / 100g.

[0024] (5) The refined melt is cast into aluminum alloy ingots using horizontal continuous casting process, with the casting temperature controlled at 700~740℃, the cooling water flow rate of the crystallizer at 80~120L / min, and the ingot drawing speed at 80~120mm / min.

[0025] (6) Homogenize the ingots: Heat the ingots to 530~560℃ and hold for 8~12 hours, then quickly water cool to room temperature;

[0026] (7) The homogenized ingot is hot extruded and formed at an extrusion temperature of 440~480℃, an extrusion ratio of 20~40:1, and an extrusion speed of 1.5~3.0m / min to obtain an aluminum alloy conductor billet;

[0027] (8) The extruded blank is cold-drawn using a multi-pass drawing process with a total deformation of 60% to 85% and a drawing speed of 5 to 15 m / min to obtain aluminum alloy conductor monofilament;

[0028] (9) The aluminum alloy conductor single wire is subjected to intermediate annealing: the annealing temperature is 320~380℃, the holding time is 2~4h, and the protective atmosphere is nitrogen atmosphere;

[0029] (10) Pretreatment of the conductor single wire surface: Alkali washing to remove oil, acid washing to activate, deionized water cleaning in sequence, and then impregnation passivation treatment with titanium zirconium composite passivation solution. The passivation temperature is 30~50℃, the passivation time is 3~8min, and the pH value is 3.0~3.8 to form a passivation film on the conductor surface.

[0030] (11) An inorganic-organic gradient coating was prepared on the surface of the conductor after passivation treatment: First, a silicon oxide-alumina composite ceramic phase coating was deposited on the surface of the conductor by sol-gel method. The coating thickness was 20~40μm. After drying and curing, a fluorocarbon resin surface layer was coated on the surface of the ceramic coating. The surface layer thickness was 10~20μm. Finally, it was cured at 120~180℃ for 30~60min to obtain the gradient coating.

[0031] (12) The coated conductor filaments are twisted into a cable to obtain aluminum alloy cable conductor material.

[0032] Further, the composite additive in step (2) is prepared as follows: nano-graphene oxide and nano-silicon carbide are mixed at a mass ratio of 1:1 to 2:1, and silane coupling agent, dispersant stabilizer and pH adjuster are added for surface modification. After ultrasonic dispersion and ball milling, the composite additive is obtained.

[0033] Furthermore, in the production method of the gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material, the electromagnetic stirring frequency in step (3) is 5~20Hz and the stirring current is 50~200A.

[0034] Furthermore, in the production method of the gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material, the total deformation of the cold drawing process in step (8) is 70%~80%, the number of drawing passes is 8~15, and the deformation of each pass is 8%~15%.

[0035] Furthermore, in the production method of the gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material, the titanium-zirconium composite passivation solution in step (10) is composed of the following components by weight percentage: 0.05%~0.15% fluorotitanic acid, 0.01%~0.05% fluorozirconic acid, 0.02%~0.10% organic phosphoric acid, and the balance being deionized water.

[0036] Furthermore, in the production method of the gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material, the silica-alumina composite ceramic phase coating in step (11) is prepared by the following method: tetraethyl orthosilicate and aluminum isopropoxide are dissolved in anhydrous ethanol, deionized water and nitric acid are added to adjust the pH value to 2.5~3.5, and the mixture is stirred and hydrolyzed in a water bath at 40~60℃ for 2~4h to form a sol solution. The sol solution is coated onto the conductor surface by dip-coating method, dried at 80~120℃ for 30~60min, and the coating is repeated 2~5 times. Finally, the coating is heat-treated at 400~500℃ for 1~2h.

[0037] Furthermore, in the production method of the gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material, the mass ratio of tetraethyl orthosilicate to aluminum isopropoxide is 1:1 to 4:1.

[0038] Furthermore, in the production method of the gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material, the fluorocarbon resin surface layer in step (11) uses polyvinylidene fluoride resin or fluorinated acrylic resin as the film-forming substance, adds curing agent and leveling agent, and is coated onto the ceramic phase coating surface by spraying or dipping.

[0039] Furthermore, in the aforementioned gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material, the surface layer of the core aluminum alloy substrate forms a corrosion-resistant reinforcing layer with a thickness of 30~50μm, and the zinc and magnesium content in the surface layer is 1.5~3 times that of the core.

[0040] Compared with the prior art, the technical advantages of this invention are:

[0041] 1. Multi-component microalloying synergistically enhances overall performance

[0042] This invention is based on 6-series and 7-series aluminum alloys and employs a multi-element microalloying design to precisely match the content and ratio of various microalloying elements, achieving synergistic effects. This invention incorporates yttrium and cerium rare earth elements, zirconium and titanium transition elements, and metallic elements such as magnesium and zinc, each playing a specific role and forming a synergistic effect. Specifically, yttrium and cerium can segregate at grain boundaries, reducing grain boundary energy and inhibiting grain growth. They can also bind to impurities in the melt, purifying the melt and refining the microstructure. Zirconium and titanium can generate thermally stable nano-Al3Zr and Al3Ti dispersed phases in the aluminum matrix, effectively pinning grain boundaries and dislocations and hindering grain recrystallization and growth.

[0043] When rare earth elements are combined with zirconium and titanium, the matrix can form multiple dispersed intermetallic compounds and refining phases of 10-100 nm, constructing a three-dimensional network structure and refining the grains to 20-50 μm. Simultaneously, the dispersed phases distributed within and at grain boundaries can block corrosion channels, uniformize the matrix electrode potential, prevent localized macrocell corrosion, and significantly reduce the sensitivity of aluminum alloys to pitting and intergranular corrosion. This invention, by optimizing the multi-element microalloying system, significantly improves the corrosion resistance of aluminum alloys while ensuring material conductivity, and also takes into account excellent hot working and forming properties.

[0044] 2. Inorganic-organic gradient coating resolves the conflict between adhesion and flexibility.

[0045] Traditional single organic coatings, while exhibiting good flexibility and density, suffer from low hardness and wear resistance, and are prone to aging and failure with prolonged use. Single inorganic ceramic coatings, on the other hand, possess high hardness, good chemical stability, and strong corrosion resistance, but are brittle, have poor adhesion, and exhibit a significant difference in thermal expansion coefficients with the aluminum alloy substrate, making them susceptible to cracking and peeling under temperature fluctuations, mechanical vibrations, and cable bending conditions, resulting in insufficient protective reliability. To address these technical bottlenecks, this invention innovatively employs an inorganic-organic gradient composite coating design, constructing a two-layer gradient protective structure on the aluminum alloy conductor surface: a silica-alumina ceramic underlayer combined with a fluorocarbon resin top layer.

[0046] The ceramic substrate is generated in situ using a sol-gel method, forming stable Al-O-Si and Al-O-Al covalent bonds with the aluminum matrix, thus significantly improving coating adhesion. Simultaneously, its dense inorganic structure effectively blocks the penetration of corrosive media such as seawater and salt spray, forming a rigid anti-corrosion barrier. The surface fluorocarbon resin possesses low surface energy, self-cleaning properties, and excellent flexibility, dispersing stress through elastic deformation and preventing cracking of the ceramic layer. The two layers are tightly bonded by hydrogen bonds, achieving a synergistic effect of rigid corrosion protection and flexible buffering, effectively solving the industry challenge of simultaneously achieving high adhesion, high corrosion resistance, and high flexibility with a single coating.

[0047] 3. Core-surface dual-functional gradient structure balances high conductivity and high corrosion resistance

[0048] In marine environments, the performance requirements for the conductor core and surface of aluminum alloy cables differ significantly: the core, responsible for power transmission, requires high conductivity to reduce energy loss; the surface, in direct contact with corrosive media such as salt spray, demands stringent corrosion resistance. Traditional homogeneous aluminum alloys cannot meet both requirements simultaneously; the addition or subtraction of alloying elements creates a trade-off between conductivity and corrosion resistance.

[0049] This invention constructs a gradient cooling field for melt solidification by precisely matching casting temperature, cooling water flow rate, and billet pulling speed. Utilizing the low partition coefficients of zinc and magnesium, it promotes continuous segregation of elements towards the ingot surface at the solid-liquid interface. Through compositional segregation and micro-alloying technology, a gradient distribution of material composition and microstructure is achieved. Subsequent hot extrusion and cold drawing further induce secondary element enrichment, stably forming a 30-50 μm corrosion-resistant strengthening layer. This achieves a controllable gradient structure where the zinc and magnesium content on the surface is 1.5-3 times that of the core, resulting in high batch-production stability. The MgZn2 phase generated on the surface can serve as a micro-anode, protecting the matrix through a sacrificial anode effect. The core, with its low alloy element content, exhibits minimal lattice distortion and a conductivity of at least 62% IACS. This design effectively resolves the contradiction between conductivity and corrosion resistance, enabling the conductor to operate efficiently and stably for extended periods in corrosive marine environments.

[0050] 4. Composite additives fill pores to form a physical barrier.

[0051] Aluminum alloys are prone to defects such as micropores and microcracks during casting and processing, which can become channels for corrosive media, inducing pitting corrosion and stress corrosion. Traditional processes can only reduce defects, but cannot completely eliminate them. This invention incorporates nano-graphene oxide and nano-silicon carbide composite additives, which are then uniformly dispersed in the matrix through ultrasonication and ball milling.

[0052] Two-dimensional sheet-like graphene oxide can cover grain boundaries and defects, forming a physical barrier; granular nano-silicon carbide has high hardness and good chemical stability, and can fill tiny pores. The two form a synergistic protective network of "surface coverage + point filling," blocking the penetration path of corrosive media, and the protective effect is far superior to that of a single filler. At the same time, graphene oxide has good electrical conductivity, which can compensate for the conductive loss caused by alloying elements.

[0053] By adding 1% to 3% of this composite additive, a three-dimensional nano-protective network is constructed in the aluminum matrix, which can reduce the corrosion current density by more than 50%, significantly hinder the intrusion of media such as chloride ions and moisture, and effectively improve the overall corrosion resistance of aluminum alloys.

[0054] 5. Sacrificial anode alloy system achieves long-term cathodic protection

[0055] In seawater environments, aluminum alloys are primarily subject to electrochemical corrosion. Chloride ions easily damage the surface oxide film, leading to anodic dissolution of the substrate. Conventional cathodic protection and external sacrificial anodes are difficult to implement and have high maintenance costs when applied to cable conductors.

[0056] This invention adds 1.5%~2.5% zinc and 0.5%~1.0% magnesium to the matrix to construct a uniformly distributed sacrificial anode phase in situ. The electrode potentials of magnesium and zinc are much lower than those of aluminum, and corrosion and dissolution preferentially occur in magnesium- and zinc-rich areas. This process also increases the local pH value, promoting the regeneration and thickening of the surface oxide film, forming a self-healing protective mechanism.

[0057] Even if the coating is damaged, the internal sacrificial anolyte phase can activate its protective function in time, preventing further localized corrosion. This alloy system significantly improves the material's corrosion resistance. According to GB / T 10125-2021, the surface showed no corrosion after 2000 hours of neutral salt spray testing, with a conductivity retention rate of ≥95%, and the corrosion current density in electrochemical testing was ≤4.5μA / cm². 2 Based on Faraday's law to calculate the corrosion rate and considering the actual operating environment of marine engineering cables, it is estimated that this product can extend the service life of cables under marine conditions to more than 30 years.

[0058] 6. Environmentally friendly titanium-zirconium chromium-free passivation achieves a balance between environmental friendliness and high performance.

[0059] Traditional chromate passivation offers excellent corrosion resistance and adhesion, but hexavalent chromium is highly toxic and causes severe pollution, leading to its strict restriction and gradual phase-out by numerous domestic and international environmental regulations. Chromium-free passivation technology has become a necessity for industry development. This invention employs a titanium-zirconium composite chromium-free passivation system to replace the traditional chromate process. By precisely proportioning fluorotitanic acid, fluorozirconic acid, and organic phosphoric acid and optimizing process parameters, a uniform and dense environmentally friendly conversion film is constructed on the aluminum alloy surface. During passivation, fluoride ions break down the natural oxide film on the substrate, and titanium and zirconium ions undergo a displacement reaction with the aluminum substrate, generating an inorganic oxide film containing Ti-O-Al and Zr-O-Al. Simultaneously, organic phosphoric acid forms an organic-inorganic hybrid structure through coordination bonds, imparting hydrophobicity to the film and providing active binding sites for subsequent coatings. This passivation film is dense and stable, with corrosion resistance comparable to traditional chromate passivation films, and is completely chromium-free, environmentally friendly, and the treatment solution is recyclable. Compared to traditional processes, the adhesion between the passivation film and the gradient coating of this invention is improved by more than 40%, combining excellent performance with economic and environmental benefits. Detailed Implementation

[0060] In this embodiment of the invention, the method for producing the gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material includes the following steps:

[0061] (1) Weigh the raw materials according to the following weight percentages: silicon 0.35%~0.55%, iron 0.20%~0.40%, total magnesium content 0.9%~1.6%, of which 0.4%~0.6% is used to form the Mg2Si strengthening phase and 0.5%~1.0% is added as a supplement to the sacrificial anode phase, copper 0.02%~0.08%, rare earth elements 0.10%~0.50%, of which the rare earth elements are a combination of yttrium and cerium with a mass ratio of 1:1~3:1, zirconium 0.05%~0.15%, titanium 0.05%~0.12%, zinc 1.5%~2.5%, nano graphene oxide 0.5%~1.0%, nano silicon carbide 0.5%~1.0%, and the mass ratio of the two is 1:1~2:1, the total addition amount of the two is 1.5%~2.5%, and boron 0.01%~0.05%, with aluminum as the balance;

[0062] (2) Preparation of composite additives: (a) Weigh nano-graphene oxide and nano-silicon carbide in a mass ratio of 1:1 to 2:1. The nano-graphene oxide has a sheet diameter of 0.5 to 5 μm and a layer count of 1 to 10. The nano-silicon carbide has a particle size of 20 to 80 nm. (b) Disperse the nano-graphene oxide in a mixed solvent of ethanol and deionized water. Add γ-aminopropyltriethoxysilane KH550 as a silane coupling agent. The amount of the coupling agent added is 1% to 5% of the mass of the nano-graphene oxide. At the same time, add polyvinylpyrrolidone as a dispersion stabilizer. The amount added is 0.5% to 2% of the mass of the nano-graphene oxide. Adjust the pH to 6 to 7 as a pH adjuster. Stir the reaction at 40 to 60 °C for 1 to 3 h to obtain a modified nano-graphene oxide dispersion. (c) Disperse the nano-silicon carbide in anhydrous ethanol. Add γ-aminopropyltriethoxysilane KH550 as a dispersion stabilizer. A silane coupling agent, KH560, is used as a silane coupling agent, with an addition amount of 1% to 5% of the mass of nano-silicon carbide. Simultaneously, polyvinylpyrrolidone (PVP) is added as a dispersant stabilizer, with an addition amount of 0.5% to 2% of the mass of nano-silicon carbide. The mixture is stirred at 40 to 60°C for 1 to 3 hours to obtain a modified nano-silicon carbide dispersion. (d) The modified nano-graphene oxide dispersion is mixed with the modified nano-silicon carbide dispersion and ultrasonically dispersed at an ultrasonic power of 200 to 500 W for 30 to 60 minutes to obtain a composite dispersion. (e) The composite dispersion is ball-milled in a ball mill at a speed of 200 to 400 rpm for 4 to 8 hours, with a ball-to-material ratio of 10:1 to 20:1. After ball milling, the mixture is vacuum-dried at 60 to 80°C for 12 to 24 hours to obtain the composite additive.

[0063] (3) The aluminum, silicon, iron, magnesium, copper, rare earth elements, zirconium, titanium, zinc, and boron weighed in step (2) are added into a melting furnace and melted at a temperature of 740~760℃. At the same time, the nanocomposite additives prepared in step (2) are added. During the melting process, electromagnetic stirring is applied at a frequency of 5~20Hz and a stirring current of 50~200A. Melt for 60~120min to obtain an alloy melt.

[0064] (4) Refining the alloy melt: Argon purging and degassing, refining agent slag removal and vacuum degassing are performed in sequence. The melt is allowed to stand for 30-60 minutes and the hydrogen content in the melt is controlled to be less than 0.15 mL / 100g.

[0065] (5) The refined melt is cast into aluminum alloy ingots using horizontal continuous casting process, with the casting temperature controlled at 700~740℃, the cooling water flow rate of the crystallizer at 80~120L / min, and the ingot drawing speed at 80~120mm / min.

[0066] (6) Homogenize the ingots: Heat the ingots to 530~560℃ and hold for 8~12 hours, then quickly water cool to room temperature;

[0067] (7) The homogenized ingot is hot extruded and formed at an extrusion temperature of 440~480℃, an extrusion ratio of 20~40:1, and an extrusion speed of 1.5~3.0m / min to obtain an aluminum alloy conductor billet;

[0068] (8) The extruded billet is cold-drawn using a multi-pass drawing process. The total deformation is 60% to 85%, and the number of drawing passes is 8 to 15, with a deformation of 8% to 15% per pass. The drawing speed is 5 to 15 m / min to obtain aluminum alloy conductor monofilaments.

[0069] (9) The aluminum alloy conductor single wire is subjected to intermediate annealing: the annealing temperature is 320~380℃, the holding time is 2~4h, and the protective atmosphere is nitrogen atmosphere;

[0070] (10) Pretreatment of the conductor monofilament surface: Alkali washing to remove oil, acid washing to activate, deionized water cleaning in sequence, and then impregnation passivation treatment with titanium-zirconium composite passivation solution (0.05%~0.15% fluorotitanic acid, 0.01%~0.05% fluorozirconic acid, 0.02%~0.10% organic phosphoric acid, and the remainder is deionized water). The passivation temperature is 30~50℃, the passivation time is 3~8min, and the pH value is 3.0~3.8 to form a passivation film on the conductor surface.

[0071] (11) An inorganic-organic gradient coating is prepared on the surface of the conductor after passivation treatment: First, tetraethyl orthosilicate and aluminum isopropoxide are dissolved in anhydrous ethanol at a mass ratio of 1:1 to 4:1. Deionized water and nitric acid are added to adjust the pH value to 2.5 to 3.5. The solution is stirred and hydrolyzed in a water bath at 40 to 60°C for 2 to 4 hours to form a sol solution. The sol solution is coated on the surface of the conductor by dip-coating method. The coating is dried at 80 to 120°C for 30 to 60 minutes. The coating is repeated 2 to 5 times. Finally, the silicon oxide-alumina composite ceramic phase coating is obtained after heat treatment at 400 to 500°C for 1 to 2 hours. (The heat treatment at 400 to 500°C in this invention only affects the cross-linking and densification of the surface ceramic coating. The heat treatment time is controllable and will not cause coarsening of the aluminum alloy matrix grains, nor will it damage the conductivity and mechanical properties of the matrix.) A silica-alumina composite ceramic phase coating with a thickness of 20-40 μm is deposited on the conductor surface using the sol-gel method. After drying and curing, polyvinylidene fluoride resin or fluorinated acrylic resin is used as the film-forming substance on the ceramic coating surface, with the addition of curing agent and leveling agent. The coating is applied to the ceramic phase coating surface by spraying or dip coating, with a surface layer thickness of 10-20 μm. Finally, it is cured at 120-180℃ for 30-60 min to obtain a gradient coating.

[0072] (12) The coated conductor filaments are twisted into a cable to obtain aluminum alloy cable conductor material.

[0073] Technical principle of the invention:

[0074] 1. Principles of Composite Additive Preparation Technology

[0075] This invention uses two-dimensional layered graphene oxide with a specific sheet size and number of layers. Its layered structure can closely fit the defect areas such as grain boundaries and microcracks of aluminum alloys, forming a continuous and dense physical barrier layer that prevents corrosive media such as moisture and chloride ions from diffusing and migrating along the defect channels. At the same time, the material has excellent electrical conductivity, which can reconstruct the internal conductive pathways of the alloy, compensate for the conductive losses caused by alloying elements such as silicon, magnesium, rare earth, and zinc, and maintain the stability of the conductivity of aluminum alloys.

[0076] This invention uses nano-silicon carbide particles of a specific size. This material has high hardness and excellent chemical stability, and can accurately fill the micropores inside the aluminum alloy matrix, sealing the micropores that allow corrosive media to penetrate. It is also chemically inert and not easily corroded in corrosive environments, thus maintaining the integrity of the matrix structure for a long time and helping to block the continuous progress of corrosion reactions.

[0077] When nano-graphene oxide and nano-silicon carbide are combined, a complete three-dimensional nano-synergistic protective network is constructed within the aluminum alloy matrix, leveraging the complementary properties of layered coverage and particle filling. Compared to single fillers, the two work synergistically, maximizing their advantages to comprehensively seal various corrosion channels such as micro-cracks, pores, and grain boundaries, significantly reducing the intrusion efficiency of corrosive media. Adding this composite additive to aluminum alloys at a ratio of 1% to 3% can reduce the alloy's corrosion current density by more than 50%, significantly inhibiting pitting corrosion, stress corrosion, and other corrosion behaviors, fundamentally improving the corrosion resistance of aluminum alloys while simultaneously maintaining the material's electrical conductivity, achieving simultaneous optimization of corrosion resistance and electrical conductivity.

[0078] 2. Principles of Aluminum Alloy Cable Conductor Material Preparation Technology

[0079] (1) Mechanism of action of each raw material component

[0080] Aluminum: The matrix; high-purity aluminum ensures conductivity. Silicon 0.35%~0.55%: Forms a Mg2Si strengthening phase with magnesium; too low a concentration results in insufficient strength, while too high a concentration forms a hard, brittle phase, reducing conductivity. Iron 0.20%~0.40%: Forms an Al-Fe-Si phase, pinning grain boundaries; excessive iron forms a needle-like β phase, initiating corrosion. Total Magnesium 0.9%~1.6%: Partly forms a strengthening phase with silicon, partly acts as a sacrificial anode, balancing mechanical properties and corrosion resistance. Copper 0.02%~0.08%: Low concentration provides strengthening; excessive copper forms an Al2Cu cathode phase, exacerbating corrosion. Rare Earth 0.1%~0.5%: Purifies the melt, refines grains, modifies the second phase, and improves oxide film stability. Zirconium 0.05%~0.15%, Titanium 0.05%~0.12%: Form dispersed Al3Zr and Al3Ti phases, pinning grain boundaries and inhibiting recrystallization. Zinc 1.5%~2.5%: Forms a sacrificial anolyte phase of MgZn2 with magnesium, dissolving preferentially due to its more negative potential. Boron 0.01%~0.05%: Forms boride precipitation with impurities such as V and Ti, improving conductivity. Nano GO / SiC: Two-dimensional sheets + zero-dimensional particles, forming a "surface + point" barrier network. Fluorotitanic acid / fluorozirconic acid / organophosphoric acid: Forms a chromium-free passivation film, with Ti-O-Al / Zr-O-Al chemical bonding. Tetraethyl orthosilicate / aluminum isopropoxide: Prepares a SiO2-Al2O2 ceramic coating using the sol-gel method. Fluorocarbon resin: Low surface energy surface layer, weather-resistant and hydrophobic.

[0081] (2) The synergistic mechanism among the components

[0082] Synergistic effects of rare earth elements with zirconium and titanium: Rare earth elements promote the dispersed precipitation of zirconium and titanium, and the dispersed phase provides an interface for rare earth agglomeration, resulting in a grain refinement effect far exceeding that of adding them alone. Synergistic effects of magnesium and zinc: The electrode potential of the MgZn2 phase is more negative than that of either magnesium or zinc-containing phases alone, resulting in stronger sacrificial anode protection. Simultaneously, the dissolution of magnesium and zinc promotes a local pH increase, accelerating oxide film regeneration. Synergistic effects of nano-GO and SiC: GO sheets form a two-dimensional barrier, while SiC particles fill the gaps between the sheets, forming a three-dimensional dense protective network. Synergistic effects of titanium-zirconium passivation film and gradient coating: Hydroxyl groups on the passivation film surface condense with silanol and aluminol groups in the sol, forming Ti-O-Si and Zr-O-Al chemical bonds, significantly enhancing the coating bonding strength.

[0083] (3) Necessity and importance of process parameter selection

[0084] Melting temperature 730~780℃: If it is too low, the alloying elements and nano-additives will dissolve and disperse poorly; if it is too high, oxidation, gas absorption, and rare earth loss will be severe. This range ensures sufficient dissolution and low impurities.

[0085] Electromagnetic stirring frequency 5~20Hz, current 50~200A: too low a frequency results in insufficient stirring, while too high a frequency generates turbulence and increases gas intake. This range yields optimal melt flow and compositional homogeneity.

[0086] Casting temperature 700~740℃ (30~50℃ above the liquidus): Too high a temperature results in coarse grains, while too low a temperature leads to cold shuts and incomplete filling. This ensures filling quality and achieves rapid solidification and fine grains.

[0087] Homogenization heat treatment at 530~560℃ for 8~12h: too low a temperature results in slow diffusion and difficulty in eliminating segregation; too high a temperature leads to overheating. Homogenization efficiency is maximized by heating at 30~50℃ below the overheating temperature.

[0088] Extrusion temperature 430~480℃: too low a temperature results in poor plasticity and easy cracking; too high a temperature leads to coarsening of the grains due to dynamic recrystallization. This ensures extrudability and achieves an ideal fibrous structure.

[0089] Intermediate annealing at 320~380℃: Too low a temperature results in insufficient recrystallization and residual work hardening; too high a temperature leads to grain growth and decreased conductivity. Complete recovery recrystallization is achieved to obtain fine equiaxed crystals.

[0090] Titanium-zirconium passivation: Temperature 30~50℃ (too low a temperature results in slow film formation, too high a temperature results in a porous film), time 3~8 min (too short a time results in a thin film, too long a time affects adhesion), pH 3.0~3.8 (too low a temperature leads to excessive corrosion and a rough film, too high a temperature leads to hydrolysis and precipitation). Within this range, a continuous and dense passivation film is obtained.

[0091] Gradient coating: Ceramic substrate heat-treated at 400~500℃—below 400℃, polycondensation is incomplete and micropores are present; above 500℃, the substrate softens. Fluorocarbon topcoat cured at 120~150℃—ensuring full cross-linking without damaging the substrate.

[0092] Through the optimization of the above parameters, this invention enables the synergistic effect of multi-element microalloying, nano-barrier network and chemical bonding interface to play a full role, resulting in significant improvements in product conductivity, corrosion resistance, coating adhesion and environmental friendliness compared with the prior art.

[0093] To make the present invention more fully disclosed, more specific embodiments are described below.

[0094] Example 1

[0095] A method for producing a gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material, comprising the following specific steps:

[0096] (1) Weigh the raw materials according to the following weight percentages (total amount is 1000 kg): silicon (Si) 3.5 kg (0.35%), iron (Fe) 2.0 kg (0.20%), magnesium (Mg) total content 9.0 kg (0.9%), of which 4.0 kg (0.40%) is used to form the Mg2Si strengthening phase and 5.0 kg (0.5%) is added as a supplement to the sacrificial anode phase, copper (Cu) 0.2 kg (0.02%), rare earth elements (RE) 1.0 kg (0.10%), of which rare earth elements include 0.5 kg of yttrium (Y), 0.5 kg of cerium (Ce), 0.5 kg of zirconium (Zr) (0.05%), 0.5 kg of titanium (Ti) (0.05%), 15.0 kg of zinc (Zn) (1.5%), 10.0 kg of nano-graphene oxide (GO) (1.0%), 5.0 kg of nano-silicon carbide (SiC) (0.5%), 0.1 kg of boron (B) (0.01%), and the balance being aluminum.

[0097] (2) Preparation of composite additives: The nano-graphene oxide (1μm, 10 layers) weighed in step (1) and nano-silicon carbide (particle size 20nm) were mixed at a mass ratio of 2:1. The nano-graphene oxide was dispersed in a mixed solvent of ethanol and deionized water (volume ratio 1:1), and γ-aminopropyltriethoxysilane KH550 (2% of the mass of nano-graphene oxide) was added. At the same time, polyvinylpyrrolidone (PVP) (1% of the mass of nano-graphene oxide) and citric acid were added to adjust the pH to 6.0. The mixture was stirred at 45℃ for 2h to obtain a modified nano-graphene oxide dispersion. The nano-silicon carbide was dispersed in anhydrous ethanol, and γ-glycidoxypropyltrimethoxysilane KH560 (2% of the mass of nano-silicon carbide) was added. At the same time, polyvinylpyrrolidone (PVP) (1% of the mass of nano-silicon carbide) was added. The mixture was stirred at 45℃ for 2h to obtain a modified nano-silicon carbide dispersion. The modified nano-graphene oxide dispersion and the modified nano-silicon carbide dispersion were mixed and ultrasonically dispersed for 60 min at an ultrasonic power of 200 W to obtain a composite dispersion. The composite dispersion was then ball-milled at 250 rpm for 7 h with a ball-to-material ratio of 10:1. After ball milling, the mixture was vacuum-dried at 60 °C for 22 h to obtain the composite additive.

[0098] (3) Weigh out aluminum, silicon, iron, magnesium, copper, rare earth elements, zirconium, titanium, zinc and boron and put them into a melting furnace. Melt them at 740°C. At the same time, add 10.0 kg (1.0%) of the composite additives obtained in step (2). Apply electromagnetic stirring (frequency 10 Hz, stirring current 100 A) during the melting process and melt them for 120 min to obtain the alloy melt.

[0099] (4) Refining the alloy melt: purging with argon gas for 15 min, adding refining agent to remove slag, then vacuum degassing for 30 min, letting the melt stand for 60 min, and controlling the hydrogen content in the melt to be less than 0.12 mL / 100 g.

[0100] (5) The refined melt is cast into an aluminum alloy ingot with a diameter of 100 mm by using a horizontal continuous casting process. The casting temperature is controlled at 700℃, the flow rate of the cooling water in the crystallizer is 100L / min, and the ingot pulling speed is 100mm / min.

[0101] (6) Homogenize the ingot: Heat the ingot to 530℃ and hold for 12 hours, then quickly cool it to room temperature with water.

[0102] (7) The homogenized ingot is hot extruded and formed at an extrusion temperature of 450°C, an extrusion ratio of 25:1, and an extrusion speed of 2.0 m / min to obtain an aluminum alloy conductor blank with a diameter of 18 mm.

[0103] (8) The extruded blank is cold-drawn using a 10-pass drawing process with a total deformation of 70% and a drawing speed of 8m / min to obtain an aluminum alloy conductor monofilament with a diameter of 9mm.

[0104] (9) The aluminum alloy conductor single wire is subjected to intermediate annealing: the annealing temperature is 320℃, the holding time is 3h, and the protective atmosphere is nitrogen atmosphere.

[0105] (10) Pretreatment of the conductor monofilament surface: Alkali washing for degreasing (5% NaOH solution, immersion at 50℃ for 5 min), acid washing for activation (10% HNO3 solution, immersion at room temperature for 2 min), and deionized water rinsing (3 times). Then, impregnation passivation treatment was performed using a titanium-zirconium composite passivation solution, which consisted of 0.05% fluorotitanic acid, 0.01% fluorozirconic acid, 0.03% organic phosphoric acid, and the remainder being deionized water. The passivation temperature was 30℃, the passivation time was 8 min, and the pH value was 3.0, forming a passivation film on the conductor surface.

[0106] (11) An inorganic-organic gradient coating was prepared on the passivated conductor surface. First, a silica-alumina composite ceramic phase coating was prepared: tetraethyl orthosilicate and aluminum isopropoxide were dissolved in anhydrous ethanol at a mass ratio of 2:1. Deionized water and nitric acid were added to adjust the pH to 3.0. The solution was stirred and hydrolyzed in a 50°C water bath for 3 hours to form a sol. The sol was coated onto the conductor surface using the dip-coating method and dried at 100°C for 40 minutes. The coating was repeated 3 times. Finally, the surface was heat-treated at 420°C for 1.5 hours to obtain a ceramic phase coating with a thickness of about 25 μm. Then, a fluorocarbon resin topcoat was coated on the ceramic coating surface: polyvinylidene fluoride resin (PVDF) was used as the film-forming substance. A coating was prepared by adding a curing agent and a leveling agent. The coating was applied to the ceramic phase coating surface by spraying. The coating thickness was about 10 μm. The coating was cured at 125°C for 30 minutes to obtain a gradient coating.

[0107] (12) The coated conductor filaments are twisted into cables to obtain aluminum alloy cable conductor material.

[0108] The aluminum alloy cable conductor material prepared in this embodiment has a core conductivity of 62.8% IACS, a corrosion-resistant reinforcement layer with a thickness of about 35μm is formed on the surface, the surface gradient coating adhesion reaches level 0, there are no obvious corrosion spots on the surface after 2000h of neutral salt spray test, the conductivity retention rate is 97.2%, and the expected service life is more than 35 years.

[0109] Example 2

[0110] A method for producing a gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material, comprising the following specific steps:

[0111] (1) Weigh the raw materials according to the following weight percentages (total amount is 1000 kg): silicon 0.45%, iron 0.30%, total magnesium content 1.3% (of which 0.5% is used to form Mg2Si strengthening phase and 0.8% is used as a sacrificial anode phase supplement), copper 0.05%, rare earth elements 0.30% (of which yttrium 0.20% and cerium 0.10%), zirconium 0.10%, titanium 0.08%, zinc 2.0%, nano graphene oxide 1.0%, nano silicon carbide 1.0%, boron 0.03%, and aluminum as the balance.

[0112] (2) Preparation of composite additive: The nano-graphene oxide (3μm, 5 layers) weighed in step (1) and nano-silicon carbide (50nm) were mixed at a mass ratio of 1:1. The nano-graphene oxide was dispersed in a mixed solvent of ethanol and deionized water (volume ratio 1:1), and γ-aminopropyltriethoxysilane KH550 (3% of the mass of nano-graphene oxide) was added. At the same time, polyvinylpyrrolidone (PVP) (1% of the mass of nano-graphene oxide) and citric acid were added to adjust the pH to 6.5. The mixture was stirred at 50℃ for 1.5h to obtain a modified nano-graphene oxide dispersion. Nano-silicon carbide was dispersed in anhydrous ethanol, and γ-glycidyl etheroxypropyltrimethoxysilane KH560 (3% of the mass of nano-silicon carbide) and polyvinylpyrrolidone (PVP) (1.5% of the mass of nano-silicon carbide) were added. The mixture was stirred at 45℃ for 2 hours to obtain a modified nano-silicon carbide dispersion. The modified nano-graphene oxide dispersion was mixed with the modified nano-silicon carbide dispersion and ultrasonically dispersed at 300W for 45 minutes to obtain a composite dispersion. The composite dispersion was ball-milled at 300 rpm for 6 hours at a ball-to-material ratio of 15:1. After ball milling, the mixture was vacuum-dried at 70℃ for 18 hours to obtain a composite additive.

[0113] (3) Weigh out aluminum, silicon, iron, magnesium, copper, rare earth elements, zirconium, titanium, zinc and boron and put them into a melting furnace. Melt them at 750°C. At the same time, add 20.0 kg (2.0%) of the composite additives obtained in step (2). Apply electromagnetic stirring (frequency 10 Hz, stirring current 100 A) during the melting process and melt them for 100 min to obtain the alloy melt.

[0114] (4) Refining the alloy melt: purging with argon gas for 15 min, adding refining agent to remove slag, then vacuum degassing for 30 min, letting the melt stand for 45 min, and controlling the hydrogen content in the melt to be less than 0.12 mL / 100 g.

[0115] (5) The refined melt is cast into an aluminum alloy ingot with a diameter of 100 mm by horizontal continuous casting process, the casting temperature is controlled at 720℃, the flow rate of cooling water in the crystallizer is 110L / min, and the ingot pulling speed is 110mm / min.

[0116] (6) Homogenize the ingot: Heat the ingot to 540℃ and hold for 10 hours, then quickly cool it to room temperature with water.

[0117] (7) The homogenized ingot is hot extruded at a temperature of 460°C, an extrusion ratio of 30:1, and an extrusion speed of 2.0 m / min to obtain an aluminum alloy conductor blank with a diameter of 18 mm.

[0118] (8) The extruded blank is cold-drawn using a 10-pass drawing process with a total deformation of 75% and a drawing speed of 10m / min to obtain an aluminum alloy conductor monofilament with a diameter of 9mm.

[0119] (9) The aluminum alloy conductor single wire is subjected to intermediate annealing: the annealing temperature is 350℃, the holding time is 3h, and the protective atmosphere is nitrogen atmosphere.

[0120] (10) Pretreatment of the conductor monofilament surface: Alkali washing for degreasing (5% NaOH solution, immersion at 50℃ for 5 min), acid washing for activation (10% HNO3 solution, immersion at room temperature for 2 min), and deionized water rinsing (3 times). Then, impregnation passivation treatment was performed using a titanium-zirconium composite passivation solution, which consisted of 0.10% fluorotitanic acid, 0.03% fluorozirconic acid, 0.05% organic phosphoric acid, and the remainder being deionized water. The passivation temperature was 40℃, the passivation time was 6 min, and the pH value was 3.5, forming a passivation film on the conductor surface.

[0121] (11) An inorganic-organic gradient coating was prepared on the passivated conductor surface. First, a silica-alumina composite ceramic phase coating was prepared: tetraethyl orthosilicate and aluminum isopropoxide were dissolved in anhydrous ethanol at a mass ratio of 2:1. Deionized water and nitric acid were added to adjust the pH to 3.0. The solution was stirred and hydrolyzed in a 50°C water bath for 3 hours to form a sol. The sol was coated onto the conductor surface using the dip-coating method and dried at 100°C for 40 minutes. The coating was repeated 3 times. Finally, the surface was heat-treated at 450°C for 1.5 hours to obtain a ceramic phase coating with a thickness of about 30 μm. Then, a fluorocarbon resin topcoat was coated onto the ceramic coating surface: polyvinylidene fluoride resin (PVDF) was used as the film-forming substance. A coating was prepared by adding a curing agent and a leveling agent. The coating was applied to the ceramic phase coating surface by spraying. The coating thickness was about 15 μm. The coating was cured at 135°C for 20 minutes to obtain a gradient coating.

[0122] (12) The coated conductor filaments are twisted into cables to obtain aluminum alloy cable conductor material.

[0123] The aluminum alloy cable conductor material prepared in this embodiment has a core conductivity of 63.2% IACS, a corrosion-resistant reinforcement layer with a thickness of about 40μm on the surface, a surface gradient coating adhesion of level 0, no obvious corrosion spots on the surface after 2000h of neutral salt spray test, a conductivity retention rate of 97.6%, and an expected service life of more than 38 years.

[0124] Single-factor experiment for screening key process parameters

[0125] 1. Single-factor experiment on melting temperature

[0126] The process is basically the same as in Example 2, except that the melting temperature is set to 700℃, 720℃, 740℃, 750℃, 760℃, 770℃ and 790℃ respectively. The results are shown in Table 1.

[0127]

[0128] Experimental conclusions: As shown in Table 1, when the melting temperature is below 740℃, insufficient temperature leads to incomplete dissolution of alloying elements, poor dispersion of nanofillers, low conductivity, and material exhibiting compositional segregation and uneven microstructure. When the melting temperature is above 760℃, melt oxidation intensifies, rare earth element loss increases, nanofillers are partially burned off, and conductivity decreases. The preferred melting temperature for this invention is 740~760℃, with an optimal value of 750℃.

[0129] 2. Single-factor experiment on the amount of rare earth elements added

[0130] The process is basically the same as in Example 2, except that the amount of rare earth elements added is set to 0%, 0.05%, 0.10%, 0.20%, 0.30%, 0.50%, and 0.60%, respectively. The results are shown in Table 2.

[0131]

[0132] Experimental conclusions: As shown in Table 2, when the rare earth element addition is below 0.1%, the grain refinement effect is insufficient, the second phase still mainly exhibits a harmful needle-like morphology, and the corrosion resistance is poor. When the rare earth element addition is above 0.5%, the rare earth compounds coarsen, which reduces mechanical properties and has a significant adverse effect on conductivity. The preferred rare earth element addition amount in this invention is 0.1%~0.5%, with an optimal value of 0.30%.

[0133] 3. Single-factor experiment on the amount of compound additives added.

[0134] The process is basically the same as in Example 2, except that the amount of composite additive added is set to 0%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, and 3.0%, respectively. The results are shown in Table 3.

[0135]

[0136] Experimental conclusions: As shown in Table 3, when the amount of composite additive is less than 1.0%, the micropores are not fully filled, the physical barrier effect is insufficient, and the improvement in corrosion resistance is limited. When the amount is greater than 2.5%, the nanofiller is prone to agglomeration in the aluminum matrix, forming new defect sources. At the same time, the limited conductivity of the nanofiller itself leads to a significant decrease in overall conductivity. The preferred amount of additive in this invention is 1.0%~2.5%, with an optimal value of 2.0%.

[0137] 4. Single-factor experiment on zinc addition amount

[0138] The process was basically the same as in Example 2, except that the amount of zinc added was set to 0%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, and 3.0%, respectively. The results are shown in Table 4.

[0139]

[0140] Experimental conclusions: Table 4 shows that when the zinc addition is below 1.5%, the sacrificial anode phase is insufficient, the corrosion potential shifts positively, and the corrosion rate is relatively fast. When the zinc addition is above 2.5%, excessive zinc dissolves in the aluminum matrix, leading to a significant decrease in conductivity. Simultaneously, the excessively negative shift in corrosion potential causes the sacrificial anode phase itself to corrode too quickly, shortening the sacrificial anode's lifespan. The preferred zinc addition amount in this invention is 1.5%~2.5%, with an optimal value of 2.0%.

[0141] 5. Single-factor experiment on extrusion temperature

[0142] The process is basically the same as in Example 2, except that the extrusion temperature is set to 400℃, 420℃, 440℃, 460℃, 480℃, 500℃ and 520℃ respectively. The results are shown in Table 5.

[0143]

[0144] Experimental conclusions: As shown in Table 5, when the extrusion temperature is below 440℃, the aluminum alloy exhibits poor plasticity and high extrusion pressure, making it prone to surface cracks and internal defects during extrusion. These defects severely impair the material's conductivity and corrosion resistance. When the extrusion temperature is above 500℃, significant dynamic recrystallization and grain growth occur during extrusion, disrupting the extruded fibrous structure and reducing conductivity. The preferred extrusion temperature of this invention is 440~500℃, with an optimal value of 460℃.

[0145] 6. Single-factor experiment on pH value of titanium-zirconium passivation solution

[0146] The process was basically the same as in Example 2, except that the pH value of the titanium-zirconium passivation solution was set to 2.0, 2.5, 3.0, 3.5, 3.8, 4.0, and 4.5, respectively. The results are shown in Table 6.

[0147]

[0148] Experimental conclusions: As shown in Table 6, when the pH value is below 3.0, the fluoride ion concentration is too high, leading to excessive dissolution of the aluminum alloy surface during passivation. The resulting passivation film is thick but porous and cannot provide effective protection. When the pH value is above 3.8, titanium and zirconium ions easily hydrolyze to form precipitates instead of forming a conversion film on the aluminum substrate surface, resulting in a thin and discontinuous passivation film. The preferred passivation solution pH value of this invention is 3.0~3.8, with the optimal value being 3.5.

[0149] 7. Single-factor experiment on intermediate annealing temperature

[0150] The process is basically the same as in Example 2, except that the intermediate annealing temperature is set to 250℃, 290℃, 320℃, 350℃, 380℃, 410℃ and 440℃ respectively. The results are shown in Table 7.

[0151]

[0152] Experimental conclusions: As shown in Table 7, when the annealing temperature is below 320℃, recrystallization is insufficient, residual stress and work hardening are not completely eliminated, the grain structure is fine but unstable, and the conductivity is low. When the annealing temperature is above 380℃, significant grain coarsening occurs, and grain growth leads to increased electron scattering, resulting in decreased conductivity. The preferred annealing temperature of this invention is 320~380℃, with an optimal value of 350℃.

[0153] Example 3

[0154] A method for producing a gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material, comprising the following specific steps:

[0155] (1) Weigh the raw materials according to the following weight percentages (total amount is 1000 kg): silicon 0.55%, iron 0.40%, magnesium total content 1.6% (of which 0.6% is used to form Mg2Si strengthening phase and 1.0% is used as sacrificial anode phase supplement), copper 0.08%, rare earth elements 0.50% (of which yttrium 0.35% and cerium 0.15%), zirconium 0.15%, titanium 0.1%, zinc 2.5%, nano graphene oxide 1.0%, nano silicon carbide 1.0%, boron 0.05%, and aluminum as balance.

[0156] (2) Preparation of composite additives: The nano-graphene oxide (5μm, 3 layers) weighed in step (1) and nano-silicon carbide (80nm) were mixed at a mass ratio of 1:1. The nano-graphene oxide was dispersed in a mixed solvent of ethanol and deionized water (volume ratio 1:1), and γ-aminopropyltriethoxysilane KH550 (4% of the mass of nano-graphene oxide) was added. At the same time, polyvinylpyrrolidone (PVP) (1.5% of the mass of nano-graphene oxide) and citric acid were added to adjust the pH to 7. The mixture was stirred at 55℃ for 1 h to obtain a modified nano-graphene oxide dispersion. The nano-silicon carbide was dispersed in anhydrous ethanol, and γ-glycidoxypropyltrimethoxysilane KH560 (2% of the mass of nano-silicon carbide) was added. At the same time, polyvinylpyrrolidone (PVP) (1% of the mass of nano-silicon carbide) was added. The mixture was stirred at 55℃ for 1 h to obtain a modified nano-silicon carbide dispersion. The modified nano-graphene oxide dispersion and the modified nano-silicon carbide dispersion were mixed and ultrasonically dispersed for 40 min at an ultrasonic power of 450 W to obtain a composite dispersion. The composite dispersion was then ball-milled at 300 rpm for 6 h with a ball-to-material ratio of 20:1. After ball milling, the mixture was vacuum-dried at 80 °C for 12 h to obtain the composite additive.

[0157] (3) Weigh out aluminum, silicon, iron, magnesium, copper, rare earth elements, zirconium, titanium, zinc and boron and put them into a melting furnace. Melt them at 780°C. At the same time, add 15.0 kg (1.5%) of the composite additives obtained in step (2). Apply electromagnetic stirring (frequency 10 Hz, stirring current 100 A) during the melting process and melt them for 90 min to obtain the alloy melt.

[0158] (4) Refining the alloy melt: purging with argon gas for 15 min, adding refining agent to remove slag, then vacuum degassing for 30 min, letting the melt stand for 60 min, and controlling the hydrogen content in the melt to be less than 0.12 mL / 100 g.

[0159] (5) The refined melt is cast into an aluminum alloy ingot with a diameter of 100 mm by horizontal continuous casting process, the casting temperature is controlled at 740℃, the flow rate of cooling water in the crystallizer is 120 L / min, and the ingot pulling speed is 100 mm / min.

[0160] (6) Homogenize the ingot: Heat the ingot to 560℃ and hold for 8 hours, then quickly water cool to room temperature.

[0161] (7) The homogenized ingot is hot extruded and formed at an extrusion temperature of 470℃, an extrusion ratio of 35:1, and an extrusion speed of 3.0m / min to obtain an aluminum alloy conductor blank with a diameter of 18mm.

[0162] (8) The extruded blank is cold-drawn using a 15-pass drawing process with a total deformation of 85% and a drawing speed of 15m / min to produce an aluminum alloy conductor monofilament with a diameter of 9mm.

[0163] (9) The aluminum alloy conductor single wire is subjected to intermediate annealing: the annealing temperature is 375℃, the holding time is 2h, and the protective atmosphere is nitrogen atmosphere.

[0164] (10) Pretreatment of the conductor monofilament surface: Alkali washing for degreasing (5% NaOH solution, immersion at 50℃ for 5 min), acid washing for activation (10% HNO3 solution, immersion at room temperature for 2 min), and deionized water rinsing (3 times). Then, impregnation passivation treatment was performed using a titanium-zirconium composite passivation solution, which consisted of 0.15% fluorotitanic acid, 0.05% fluorozirconic acid, 0.10% organic phosphoric acid, and the remainder being deionized water. The passivation temperature was 50℃, the passivation time was 4 min, and the pH value was 3.8, forming a passivation film on the conductor surface.

[0165] (11) An inorganic-organic gradient coating was prepared on the passivated conductor surface. First, a silica-alumina composite ceramic phase coating was prepared: tetraethyl orthosilicate and aluminum isopropoxide were dissolved in anhydrous ethanol at a mass ratio of 2:1. Deionized water and nitric acid were added to adjust the pH to 3.0. The solution was stirred and hydrolyzed in a 50°C water bath for 3 hours to form a sol. The sol was coated onto the conductor surface using the dip-coating method and dried at 100°C for 40 minutes. The coating was repeated 3 times. Finally, the surface was heat-treated at 420°C for 1.5 hours to obtain a ceramic phase coating with a thickness of about 40 μm. Then, a fluorocarbon resin topcoat was coated on the ceramic coating surface: polyvinylidene fluoride resin (PVDF) was used as the film-forming substance. A coating was prepared by adding a curing agent and a leveling agent. The coating was applied to the ceramic phase coating surface by spraying. The coating thickness was about 20 μm. The coating was cured at 150°C for 15 minutes to obtain a gradient coating.

[0166] (12) The coated conductor filaments are twisted into cables to obtain aluminum alloy cable conductor material.

[0167] The aluminum alloy cable conductor material prepared in this embodiment has a core conductivity of 62.5% IACS, a corrosion-resistant reinforcement layer with a thickness of about 45μm is formed on the surface, the surface gradient coating adhesion reaches level 0, there are no obvious corrosion spots on the surface after 2000h of neutral salt spray test, the conductivity retention rate is 97.0%, and the expected service life is more than 40 years.

[0168] Example 4

[0169] This embodiment is basically the same as Embodiment 2, except that the composition parameters of the titanium-zirconium composite passivation solution are different. In this embodiment, the titanium-zirconium composite passivation solution consists of 0.15% fluorotitanic acid, 0.05% fluorozirconic acid, 0.08% organic phosphoric acid, and the balance being deionized water. The passivation temperature is 50℃, the passivation time is 8 min, and the pH value is 3.0.

[0170] The remaining process steps and parameters are the same as in Example 2.

[0171] The aluminum alloy cable conductor material prepared in this embodiment has a denser surface passivation film, higher bonding strength with the gradient coating, and a more complete chemical bonding interface between the ceramic substrate and the aluminum matrix. After 3000 hours of neutral salt spray testing, no visible corrosion points were observed on the surface, the conductivity retention rate was 97.8%, and the expected service life exceeds 42 years.

[0172] Example 5

[0173] This embodiment is basically the same as Embodiment 2, except that the preparation parameters of the gradient coating are different. In this embodiment, the mass ratio of tetraethyl orthosilicate to aluminum isopropoxide is 3:1, the sol coating is applied 4 times, and the thickness of the ceramic substrate is approximately 40 μm. The fluorocarbon resin surface layer uses fluorinated acrylic resin as the film-forming material, with a curing temperature of 140°C and a curing time of 25 min. The remaining process steps and parameters are the same as in Embodiment 2.

[0174] The gradient coating structure of the aluminum alloy cable conductor material prepared in this embodiment is more dense, and the low surface energy characteristics of the fluorocarbon surface layer are more prominent. Water contact angle testing shows that the water contact angle on the coating surface reaches 115°, and corrosive droplets are difficult to adhere to and remain on the coating surface during salt spray testing. After 2500 hours of neutral salt spray testing, there are no obvious corrosion points on the surface, the conductivity retention rate is 97.5%, and the expected service life exceeds 40 years.

[0175] Example 6

[0176] This embodiment is basically the same as Embodiment 2, except that the process parameters for homogenization heat treatment and intermediate annealing are different. In this embodiment, the homogenization heat treatment temperature is 550℃ and the holding time is 12h. The intermediate annealing temperature is 370℃ and the holding time is 4h. The remaining process steps and parameters are the same as in Embodiment 2.

[0177] The aluminum alloy cable conductor material prepared in this embodiment has a finer and more uniform grain structure, with a more uniform distribution of Al3r and Al3i dispersed phases, resulting in superior thermal stability. After exposure to 300℃ for 100 hours, the conductivity decay rate is only 3.2%, demonstrating excellent resistance to thermal degradation. After 2000 hours of neutral salt spray testing, no obvious corrosion points were observed on the surface, and the conductivity retention rate is 97.4%, with an expected service life exceeding 38 years.

[0178] Comparative Example 1

[0179] This comparative example is basically the same as Example 2, except that the rare earth elements yttrium and cerium are not added. Other components and process steps are the same as in Example 2.

[0180] Due to the lack of rare earth elements to refine grains and purify the melt, the aluminum alloy cable conductor material prepared in this comparative example has significantly coarser grains, with an average grain size of approximately 120 μm (compared to only 48 μm in Example 2). The second phase in the alloy exhibits a needle-like distribution, resulting in poor microstructure uniformity. The coating adhesion test result was level 4, and the conductivity was 62.1% IACS, slightly lower than that of Example 2. During the neutral salt spray test, pitting corrosion began to appear on the conductor surface after 600 hours; at 1000 hours, pitting corrosion increased significantly, with corrosion pit depths exceeding 30 μm; after 1500 hours, a large number of corrosion products appeared on the surface, and the conductivity decreased to 86% of the initial value. The salt spray resistance of this comparative example was significantly lower than that of Example 2, indicating that rare earth elements play a crucial role in improving the corrosion resistance of aluminum alloys.

[0181] Comparative Example 2

[0182] This comparative example is basically the same as Example 2, except that zirconium and titanium are not added, while other components and process steps are the same as in Example 2.

[0183] Due to the lack of dispersed phase pinning effect of zirconium and titanium, the aluminum alloy cable conductor material prepared in this comparative example underwent significant grain growth during hot extrusion and cold drawing, resulting in uneven recrystallized grain size. The coating adhesion test result was level 5, and the conductivity was 62.3% IACS. After 800 hours of neutral salt spray testing, corrosion grooves began to appear at the grain boundaries; after 1200 hours, intergranular corrosion became significant, with some grains showing a tendency to peel off; after 1800 hours, the conductivity decreased to 82% of the initial value. The intergranular corrosion resistance of this comparative example is far lower than that of Example 2, indicating that zirconium and titanium play an important role in inhibiting intergranular corrosion.

[0184] Comparative Example 3

[0185] This comparative example is basically the same as Example 2, except that zinc and sacrificial anode supplementary magnesium are not added (i.e., the total magnesium content is only 0.4% for the formation of Mg2Si, and no additional magnesium is added). Other components and process steps are the same as in Example 2.

[0186] Due to the lack of cathodic protection from the sacrificial anode phase, the aluminum alloy cable conductor material prepared in this comparative example exhibited a significantly accelerated corrosion rate in a chloride ion environment. The coating adhesion test result was level 2, and the conductivity was 63.5% IACS (slightly higher due to the absence of zinc). After 400 hours of neutral salt spray testing, uniformly distributed corrosion spots appeared on the conductor surface; after 800 hours, the corrosion spots coalesced into patches, and corrosion products were evident; after 1200 hours, the conductivity dropped to 70% of the initial value, rendering the material unusable. Although this comparative example showed slightly higher conductivity, its corrosion resistance was severely inadequate, demonstrating the crucial importance of the sacrificial anode system for corrosion resistance in marine environments.

[0187] Comparative Example 4

[0188] This comparative example is basically the same as Example 2, except that no nano-graphene oxide and nano-silicon carbide composite additives are added. Other components and process steps are the same as in Example 2.

[0189] Due to the lack of physical barrier effect from nanomaterials filling the micropores, the micropores and defects in the aluminum alloy cable conductor material prepared in this comparative example cannot be effectively filled, allowing for a more unobstructed penetration path of the corrosive medium. The conductivity is 62.8% IACS. During the neutral salt spray test, pitting corrosion began to appear at the micro-defects on the conductor surface after 700 hours; after 1100 hours, the pitting corrosion became more concentrated, and the corrosion rate accelerated; after 1500 hours, the conductivity decreased to 78% of the initial value. The salt spray resistance of this comparative example is significantly lower than that of Example 2, indicating that the nanocomposite additive plays an important role in blocking the penetration of corrosive media.

[0190] Comparative Example 5

[0191] This comparative example is basically the same as Example 2, except that titanium zirconium passivation treatment is not performed, and a gradient coating is directly prepared on the surface of the pretreated conductor. Other process steps are the same as in Example 2.

[0192] Due to the lack of a chemical bonding interface provided by the titanium-zirconium passivation film, the interfacial bonding between the ceramic substrate and the aluminum matrix in the aluminum alloy cable conductor material prepared in this comparative example is mainly based on physical adsorption, resulting in insufficient bonding strength. The coating adhesion test result was level 3, significantly lower than level 0 in Example 2. After 500 hours of neutral salt spray testing, localized cracking and blistering of the coating occurred; after 800 hours, the coating began to peel off; and after 1200 hours, the exposed aluminum alloy matrix suffered severe corrosion. The coating stability and corrosion resistance of this comparative example were significantly lower than those of Example 2, indicating that titanium-zirconium passivation treatment plays a crucial role in improving coating adhesion and overall corrosion resistance.

[0193] Comparative Example 6

[0194] This comparative example is basically the same as Example 2, except that only a single fluorocarbon resin organic coating is used for surface protection, and no ceramic phase underlayer is prepared. Other process steps are the same as in Example 2.

[0195] Due to the lack of a rigid barrier provided by the ceramic substrate, the organic coating on the surface of the aluminum alloy cable conductor material prepared in this comparative example, while exhibiting good flexibility, suffers from poor scratch and abrasion resistance, making it prone to damage during processing and use. The coating hardness is HB grade (the coating hardness in Example 2 is ≥5H), and the coating adhesion test result is grade 2. After 300 hours of neutral salt spray testing, corrosion began to appear at localized damaged areas on the coating surface; after 600 hours, the corrosion range expanded, with filamentary corrosion occurring beneath the coating; and after 1000 hours, the conductivity decreased to 75% of the initial value. The corrosion resistance of this comparative example is significantly lower than that of Example 2, indicating that the dual-layer structure design of the inorganic-organic gradient coating is of significant value in improving corrosion resistance.

[0196] Comparative Example 7

[0197] This comparative example is basically the same as Example 2, except that only a single silicon oxide-alumina ceramic coating is used for surface protection, and no fluorocarbon resin surface layer is prepared. Other process steps are the same as in Example 2.

[0198] Due to the lack of a flexible fluorocarbon resin surface layer as a stress buffer, the ceramic coating on the surface of the aluminum alloy cable conductor material prepared in this comparative example is hard and brittle, easily developing microcracks when the cable is bent. The coating adhesion test result was Grade 1. After 800 hours of neutral salt spray testing, fine microcracks appeared in the coating at the bending area; after 1100 hours, chloride ions penetrated along the microcracks to the aluminum substrate surface, initiating localized corrosion; after 1500 hours, the conductivity decreased to 72% of the initial value. The corrosion resistance of this comparative example is significantly lower than that of Example 2, indicating that the flexible buffering effect of the fluorocarbon resin surface layer is very important for maintaining the integrity of the coating.

[0199] Comparative Example 8

[0200] This comparative example is basically the same as Example 2, except that the melting temperature is set to 700℃ (lower than the range of this invention), and the other process steps are the same as in Example 2.

[0201] Due to the excessively low melting temperature, alloying elements and nanocomposite additives could not be fully melted and dispersed, resulting in poor alloy composition uniformity and severe agglomeration of nanofillers. The conductivity was only 60.5% IACS. Significant component segregation was observed within the material, with nanofiller agglomerates reaching tens of micrometers in size. Corrosion began to appear around the nanofiller agglomerates after 400 hours of neutral salt spray testing; corrosion accelerated after 800 hours, and the conductivity decreased to 68% of its initial value. The conductivity and corrosion resistance of this comparative example were both lower than those of Example 2, demonstrating the crucial importance of a suitable melting temperature for ensuring product quality.

[0202] Comparative Example 9

[0203] This comparative example is basically the same as Example 2, except that the pH value of the passivation solution is set to 2.5 (below the range of the present invention), and the other process steps are the same as those in Example 2.

[0204] Due to the excessively low pH value and high fluoride ion concentration of the passivation solution, the aluminum alloy surface was excessively corroded during the passivation process, resulting in a rough, porous, and unevenly thick passivation film. The coating adhesion test result was grade 2. During the neutral salt spray test, blistering occurred in the thinner areas of the passivation film after 300 hours; after 700 hours, the coating peeled off over a large area; and after 1000 hours, the aluminum alloy conductor showed severe corrosion. The coating adhesion and corrosion resistance of this comparative example were both lower than those of Example 2, indicating that controlling the pH value of the passivation solution within an appropriate range is crucial for obtaining a high-quality passivation film.

[0205] Comparative Example 10

[0206] This comparative example is basically the same as Example 2, except that the heat treatment temperature of the ceramic coating is set to 600℃ (higher than the range of this invention), and the other process steps are the same as in Example 2.

[0207] Due to the excessively high heat treatment temperature of the ceramic coating (significant recrystallization and grain growth occurred in the aluminum alloy substrate at 600℃), the mechanical properties and conductivity of the aluminum substrate were adversely affected. The grain size of the aluminum substrate increased significantly to approximately 150 μm, and the conductivity decreased to 60.8% IACS. After 500 hours of neutral salt spray testing, the thermal stress at the interface between the coating and the substrate increased due to the difference in thermal expansion coefficients, and interface debonding began to occur; after 900 hours, the coating partially peeled off; and after 1300 hours, the conductivity decreased to 70% of the initial value. The conductivity and corrosion resistance of this comparative example were both lower than those of Example 2, indicating that controlling the heat treatment temperature of the ceramic coating to not exceed 500℃ is of great significance for protecting the properties of the aluminum substrate.

[0208] VI. Performance Testing and Result Analysis

[0209] 1. Testing methods and standards

[0210] (1) Conductivity test: The volume resistivity was determined in accordance with GB / T 3048.2-2007 "Test methods for electrical properties of wires and cables - Part 2: Test for resistivity of metallic materials", and the conductivity (%IACS) was calculated. The test instrument was a QJ57 type DC double-arm bridge, the test environment temperature was (20±0.5)℃, the sample length was 1000mm, and the cross-section was uniform.

[0211] (2) Salt spray corrosion resistance test: The test was conducted according to the neutral salt spray test (NSS) method in GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test". Test conditions: 5% NaCl solution, pH value 6.5~7.2, test temperature (35±2)℃, salt spray deposition 1.5mL / 80cm 2 • h. The test cycle is 2000h. After the test, the surface corrosion level is evaluated according to GB / T 6461-2002 standard.

[0212] (3) Coating adhesion test: The adhesion test shall be conducted in accordance with the relevant cross-cut adhesion test method in GB / T 12967.3-2022 "Test methods for anodic oxide films and organic polymer films of aluminum and aluminum alloys - Part 3: Salt spray test". The cross-cut adhesion test shall be used and the rating shall be 0 to 5, with 0 being the best (smooth cut edge without peeling).

[0213] (4) Corrosion depth detection: The corrosion morphology of the sample cross section was observed using an Olympus BX51 metallographic microscope, and the maximum depth of corrosion pits and the average corrosion depth were measured. Five fields of view were measured, and the average value was taken.

[0214] (5) Corrosion rate determination: Corrosion products were removed according to the standard method of GB / T 16545-2025 "Corrosion of metals and alloys - Removal of corrosion products from corrosion test specimens". The corrosion rate was calculated by weighing method, in mm / year.

[0215] (6) Grain size determination: The average grain size was determined by the cut-off method in GB / T 6394-2017 "Method for determination of average grain size of metal".

[0216] (7) Electrochemical performance test: According to GB / T 17848-2019 "Test method for electrochemical performance of sacrificial anode", polarization curve test was performed using CHI660E electrochemical workstation. The medium was 3.5% NaCl solution, the scan rate was 0.5mV / s, and the potential range was -1.0V to +0.5V (vs SCE). The corrosion current density and corrosion potential were calculated.

[0217] 2. Comparative Analysis of Performance Test Results between Example 2 and the Comparative Example

[0218] (I) Conductivity Comparison Analysis

[0219]

[0220] As shown in Table 8, the conductivity of this embodiment is 63.2% IACS, exceeding the design target of 62% IACS. Example 2 has the highest conductivity at 63.2% IACS, which is due to its relatively low alloying element content (0.3% rare earth, 2.0% zinc, and 2.0% nanocomposite additives), resulting in less electron scattering.

[0221] Comparing the comparative examples: Comparative example 3 (without zinc addition) had the highest conductivity (63.5% IACS), but its corrosion resistance was extremely poor; Comparative example 8 (melting temperature 700℃) had a conductivity of only 60.5% IACS, indicating that the melting temperature was too low, leading to uneven composition and agglomeration of nanofillers; Comparative example 10 (ceramic coating heat treatment at 600℃) had a conductivity of 60.8% IACS, due to coarsening of the aluminum matrix grains caused by the high temperature. These results indicate that the process window design of this invention is reasonable, maximizing high conductivity while ensuring excellent corrosion resistance.

[0222] (II) Comparative Analysis of Salt Spray Corrosion Resistance

[0223]

[0224] As shown in Table 9, after 2000 hours of neutral salt spray testing, the surface corrosion level of all examples reached 9.8 or higher (the highest being 9.9), the corrosion area was less than 0.1%, and there were almost no visible corrosion points. The conductivity retention rate all exceeded 96%, with Example 2 reaching 97.6%. This indicates that the multi-protection system constructed in this invention—multi-element microalloying + nanocomposite filling + sacrificial anode + gradient coating—played a synergistic protective role in the harsh salt spray environment of 2000 hours.

[0225] Comparing the salt spray test results of the comparative examples: Comparative Example 1 (without rare earth) showed a conductivity retention rate of 86% after 1500h, with severe surface corrosion; Comparative Example 2 (without zirconium and titanium) showed a conductivity retention rate of 82% after 1800h, with obvious intergranular corrosion; Comparative Example 3 (without sacrificial anode) showed a conductivity retention rate of 70% after only 1200h, with the most severe corrosion; Comparative Example 4 (without nano-additives) showed a conductivity retention rate of 78% after 1500h; Comparative Example 5 (without passivation) showed coating peeling off within 1200h, leading to severe corrosion of the substrate; Comparative Example 6 (organic coating only) showed a conductivity retention rate of 75% after 1000h, and Comparative Example 7 (ceramic coating only) showed a conductivity retention rate of 72% after 1500h. The corrosion resistance of both examples was far lower than that of the examples. These comparisons fully demonstrate that the multi-dimensional composite modification strategy of the present invention, consisting of "multi-element micro-alloying + nano-composite additives + sacrificial anode + titanium-zirconium passivation + gradient coating", is indispensable, and the synergistic effect of each technical feature produces a synergistic effect of 1+1>2.

[0226] (III) Comparative Analysis of Coating Adhesion

[0227]

[0228] As shown in Table 10, the coating adhesion in this embodiment is all grade 0 (optimal grade), indicating that a strong chemical bond interface is formed between the titanium-zirconium passivation film and the gradient coating, and the inorganic-organic gradient structure design effectively avoids interlayer stress concentration. The coating adhesion of Comparative Example 5 (no passivation treatment) is grade 3, Comparative Example 6 (organic coating only) is grade 2, Comparative Example 7 (ceramic coating only) is grade 1, and Comparative Example 9 (passivation pH 2.5) is grade 2, all significantly lower than the embodiments. This indicates that the optimal pH range (3.0~3.8) for titanium-zirconium passivation treatment is crucial for the formation of a dense passivation film and the bonding of subsequent coatings; deviations from this range lead to a decrease in passivation film quality. According to GB / T 12967.3-2022 testing verification, the adhesion of traditional chromate passivation coatings is grade 2, while the adhesion of the titanium-zirconium organic hybrid passivation film coating of this invention reaches grade 0, significantly improving interfacial bonding stability. Quantitative comparison shows an overall improvement in adhesion of over 40%.

[0229] (iv) Comparative analysis of corrosion current density and service life

[0230]

[0231] As shown in Table 11, the corrosion current density in this embodiment is 3.8 μA / cm. 2 The comparative values ​​are generally between 9.6 and 18.5 μA / cm. 2 The corrosion current density is positively correlated with the corrosion rate, therefore, the corrosion rate of this invention is estimated to be only 1 / 3 to 1 / 5 of that of the comparative example. According to GB / T 10125-2021, the surface showed no corrosion after 2000 hours of neutral salt spray testing, with a conductivity retention rate ≥95%, and the electrochemical test showed a corrosion current density ≤4.5 μA / cm². 2 Based on Faraday's law to calculate the corrosion rate and considering the actual operating environment of marine engineering cables, the estimated service life of this product in a marine environment is 35-42 years, while comparative examples generally range from 5-18 years. In particular, the service lives of comparative examples 5 (no passivation), 9 (inappropriate passivation pH), and 3 (no sacrificial anode) are less than 10 years. This demonstrates that the technical solution of this invention has achieved a breakthrough in long-term corrosion resistance.

[0232] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for producing a gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material, characterized in that, Includes the following steps: (1) Weigh the raw materials according to the following weight percentages: silicon 0.35%~0.55%, iron 0.20%~0.40%, total magnesium content 0.9%~1.6%, of which 0.4%~0.6% is used to form the Mg2Si strengthening phase and 0.5%~1.0% is added as a supplement to the sacrificial anode phase, copper 0.02%~0.08%, rare earth elements 0.10%~0.50%, of which the rare earth elements are a combination of yttrium and cerium with a mass ratio of 1:1~3:1, zirconium 0.05%~0.15%, titanium 0.05%~0.12%, zinc 1.5%~2.5%, nano graphene oxide 0.5%~1.0%, nano silicon carbide 0.5%~1.0%, and the mass ratio of the two is 1:1~2:1, the total addition amount of the two is 1.5%~2.5%, and boron 0.01%~0.05%, with aluminum as the balance; (2) Preparation of composite additives; (3) The aluminum, silicon, iron, magnesium, copper, rare earth elements, zirconium, titanium, zinc and boron weighed in step (1) are put into a melting furnace and melted at a temperature of 740~760℃. At the same time, the composite additives prepared in step (2) are added. Electromagnetic stirring is applied during the melting process, and the melting is fully carried out for 60~120 minutes to obtain the alloy melt. (4) Refining the alloy melt: Argon purging and degassing, refining agent slag removal and vacuum degassing are performed in sequence. The melt is allowed to stand for 30-60 minutes and the hydrogen content in the melt is controlled to be less than 0.15 mL / 100g. (5) The refined melt is cast into aluminum alloy ingots using horizontal continuous casting process, with the casting temperature controlled at 700~740℃, the cooling water flow rate of the crystallizer at 80~120L / min, and the ingot drawing speed at 80~120mm / min. (6) Homogenize the ingots: Heat the ingots to 530~560℃ and hold for 8~12 hours, then quickly water cool to room temperature; (7) The homogenized ingot is hot extruded and formed at an extrusion temperature of 440~480℃, an extrusion ratio of 20~40:1, and an extrusion speed of 1.5~3.0m / min to obtain an aluminum alloy conductor billet; (8) The extruded blank is cold-drawn using a multi-pass drawing process with a total deformation of 60% to 85% and a drawing speed of 5 to 15 m / min to obtain aluminum alloy conductor monofilament; (9) The aluminum alloy conductor single wire is subjected to intermediate annealing: the annealing temperature is 320~380℃, the holding time is 2~4h, and the protective atmosphere is nitrogen atmosphere; (10) Pretreatment of the conductor single wire surface: Alkali washing to remove oil, acid washing to activate, deionized water cleaning in sequence, and then impregnation passivation treatment with titanium zirconium composite passivation solution. The passivation temperature is 30~50℃, the passivation time is 3~8min, and the pH value is 3.0~3.8 to form a passivation film on the conductor surface. (11) An inorganic-organic gradient coating is prepared on the surface of the conductor after passivation: First, a silicon oxide-alumina composite ceramic phase coating is deposited on the surface of the conductor by sol-gel method. The coating thickness is 20~40μm. After drying and curing, a fluorocarbon resin surface layer with a thickness of 10~20μm is coated on the surface of the ceramic coating. After curing at 120~150℃ for 15~30min, a gradient coating is obtained. (12) The coated conductor filaments are twisted into a cable to obtain aluminum alloy cable conductor material.

2. The method for producing gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material according to claim 1, characterized in that, The composite additive described in step (2) is prepared as follows: Nano-graphene oxide and nano-silicon carbide are mixed at a mass ratio of 1:1 to 2:1, and silane coupling agent, dispersant stabilizer and pH adjuster are added for surface modification. After ultrasonic dispersion and ball milling, the composite additive is obtained.

3. The method for producing gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material according to claim 1, characterized in that, The electromagnetic stirring frequency in step (3) is 5~20Hz and the stirring current is 50~200A.

4. The method for producing gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material according to claim 1, characterized in that, The total deformation of the cold drawing process in step (8) is 70%~80%, the number of drawing passes is 8~15, and the deformation of each pass is 8%~15%.

5. The method for producing gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material according to claim 1, characterized in that, The titanium-zirconium composite passivation solution in step (10) is composed of the following components in weight percentage: 0.05%~0.15% fluorotitanic acid, 0.01%~0.05% fluorozirconic acid, 0.02%~0.10% organic phosphoric acid, and the balance being deionized water.

6. The method for producing gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material according to claim 1, characterized in that, The silica-alumina composite ceramic phase coating described in step (11) is prepared by the following method: tetraethyl orthosilicate and aluminum isopropoxide are dissolved in anhydrous ethanol, deionized water and nitric acid are added to adjust the pH value to 2.5~3.5, and the mixture is stirred and hydrolyzed in a water bath at 40~60℃ for 2~4h to form a sol solution. The sol solution is coated onto the conductor surface by dip-coating method, and dried at 80~120℃ for 30~60min. The thickness of a single dip-coating is 5~8μm, and the cumulative thickness reaches 20~40μm after 2~5 coatings. Finally, the coating is cured at 120~180℃ for 30~60min.

7. The method for producing the gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material according to claim 6, characterized in that, The mass ratio of tetraethyl orthosilicate to aluminum isopropoxide is 1:1 to 4:

1.

8. The method for producing gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material according to claim 1, characterized in that, In step (11), the fluorocarbon resin surface layer uses polyvinylidene fluoride resin or fluorinated acrylic resin as the film-forming substance, adds curing agent and leveling agent, and is coated onto the surface of ceramic phase coating by spraying or dipping.

9. A gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material, characterized in that, The aluminum alloy cable conductor material is prepared by the production method of the gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material according to any one of claims 1 to 8.

10. The gradient composite modified marine corrosion-resistant aluminum alloy cable conductor material according to claim 9, characterized in that, In the aluminum alloy cable conductor material prepared by the method, a corrosion-resistant reinforcing layer with a thickness of 30~50μm is formed on the surface of the core aluminum alloy substrate, and the zinc and magnesium content in the surface layer is 1.5~3 times that of the core.

Images