Aluminum alloy material for high-toughness corrosion-resistant aluminum alloy cable, preparation method and power cable

Abstract

The invention discloses an aluminum alloy material for a high-toughness corrosion-resistant aluminum alloy cable, a preparation method and a power cable. The aluminum alloy material comprises, by weight, 0.60%-0.95% of Fe, 0.08%-0.18% of Si, 0.05%-0.20% of Cu, 0.02%-0.10% of Sn, 0.008%-0.05% of In, 0.08%-0.15% of Zr, 0.08%-0.20% of Er, 0.02%-0.10% of Yb, 0.03%-0.12% of Hf, 0.01%-0.08% of Ag, 0.003%-0.02% of B, smaller than or equal to 0.03% of Mg and the balance Al and inevitable impurities, and the content of Sc is smaller than or equal to 0.005%. The core-shell structure nanometer strengthening phase is constructed in the aluminum matrix, precise regulation and control of grain boundary components are synchronously achieved, and the comprehensive performance breakthrough of the tensile strength and the electric conductivity of the material is achieved.

Description

Technical Field

[0001] This invention relates to the field of power transmission technology, and in particular to aluminum alloy materials and preparation methods for high-strength, tough, and corrosion-resistant aluminum alloy cables, as well as power cables. Background Technology

[0002] In the field of power transmission, overhead conductors and cable conductors must simultaneously meet the comprehensive requirements of high strength, high conductivity, excellent corrosion resistance, and economy. Although pure aluminum (such as the 1350 series) has excellent conductivity (≥61% IACS), its mechanical properties are poor and it is prone to creep, making it difficult to meet the needs of long-span or heavy-load lines.

[0003] To improve the strength of aluminum alloy conductors, the industry has mainly adopted two technical approaches: One method is to strengthen the structure by adding alloying elements to form solid solutions or precipitates.

[0004] Traditional methods primarily involve adding elements such as Mg, Si, or Fe. For example, widely used 6000 series aluminum alloys (such as alloy 6201) improve strength through the precipitation of the Mg2Si phase. However, the addition of Mg and Si elements severely exacerbates lattice distortion in the aluminum matrix, leading to increased electron scattering and thus significantly sacrificing conductivity (typically <58% IACS). Although subsequent studies have attempted to improve performance by optimizing the Fe content, the "inverse relationship" between strength and conductivity remains a difficult bottleneck to overcome; high strength often comes at the cost of a significant decrease in conductivity.

[0005] Secondly, rare earth elements or foreign reinforcing phases are introduced.

[0006] In recent years, research has found that adding the rare earth element scandium (Sc) can form coherent Al3Sc nanoprecipitates in an aluminum matrix. This achieves significant grain refinement and precipitation strengthening while minimizing damage to conductivity, thus achieving a synergistic improvement in strength and conductivity to some extent. However, Sc is extremely rare in the Earth's crust and very expensive (typically exceeding $3,000 / kg), resulting in high costs for Sc-containing aluminum alloys and hindering their large-scale application in the cost-sensitive commodity sector of power cables. Another technological approach involves introducing carbon-based reinforcements such as carbon nanotubes and graphene, attempting to utilize their ultra-high strength and high conductivity to prepare composite materials. However, this technology faces two major challenges: first, achieving macroscopically uniform dispersion of the nano-reinforcement in the aluminum matrix is ​​extremely difficult; second, poor interfacial bonding between the reinforcement and the aluminum matrix easily leads to interfacial resistance, which may actually reduce the overall conductivity.

[0007] Furthermore, as power grids extend into highly corrosive environments such as coastal areas and industrial zones, the corrosion resistance of cables has become a key performance indicator. Traditional aluminum alloys with high Mg content tend to precipitate continuous Al3Mg2 phases at grain boundaries during service. These phases have a negative potential and easily act as anodes, initiating intergranular corrosion and leading to brittle fracture. While adding low-melting-point elements such as Sn and In can improve certain electrochemical properties, improper addition or uneven distribution can also impair conductivity and mechanical properties.

[0008] In summary, the existing technology lacks an aluminum alloy cable material and its efficient preparation method that can achieve a synergistic improvement in high strength (≥350MPa), high conductivity (≥60.5% IACS) and excellent corrosion resistance through internal microstructure design without relying on expensive Sc elements. Summary of the Invention

[0009] To address the aforementioned technical problems, the present invention aims to provide aluminum alloy materials and preparation methods for high-strength, tough, and corrosion-resistant aluminum alloy cables. Through the synergistic effect of multiple rare earth elements and the sequential regulation of composite physical fields, the present invention constructs a high-density, compositionally gradient core-shell nano-reinforcing phase within an aluminum matrix without relying on expensive scandium elements. Simultaneously, it achieves precise control of grain boundary composition. This results in a comprehensive performance breakthrough with a tensile strength ≥350MPa and a conductivity ≥60.5% IACS, all while remaining cost-effective.

[0010] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides an aluminum alloy material for high-strength, tough, and corrosion-resistant aluminum alloy cables, which does not contain artificially added scandium (Sc). By weight percentage, its composition includes: Fe 0.60-0.95%, Si 0.08-0.18%, Cu 0.05-0.20%, Sn 0.02-0.10%, In 0.008-0.05%, Zr 0.08-0.15%, Er 0.08-0.20%, Yb 0.02-0.10%, Hf 0.03-0.12%, Ag 0.01-0.08%, B 0.003-0.02%, Mg ≤ 0.03%, with the balance being Al and unavoidable impurities. The total impurity content is ≤0.10%, the content of any single impurity (excluding Sc) is ≤0.02%, and the content of Sc as an impurity is ≤0.005%.

[0011] Furthermore, in the aluminum alloy material, the weight ratio of Er to Yb is from 2:1 to 8:1. Within this preferred ratio range, Er dominates the formation of a high-density nucleation core, while Yb, with its larger atomic radius and slower diffusion rate, accumulates around the core. Together with the subsequently added Hf, Yb lays the compositional foundation for the formation of the nanoprecipitated phase.

[0012] Furthermore, the microstructure of the aluminum alloy material contains dispersed nano-precipitates with a gradient shell structure of Al3(Er,Yb,Zr) as the core and enriched with Hf on the periphery, exhibiting an electrical conductivity ≥60.5% IACS and a tensile strength ≥350MPa. This core-shell structure, formed through the synergistic ratio of Er-Yb-Hf-Zr multi-element rare earth elements and subsequent specific process induction, effectively pins grain boundaries and hinders dislocation movement while achieving grain refinement and precipitation strengthening.

[0013] Preferably, the composition range of the aluminum alloy material is: Fe 0.65-0.80%, Si 0.09-0.12%, Cu 0.08-0.15%, Sn 0.03-0.06%, In 0.01-0.04%, Zr 0.09-0.12%, Er 0.10-0.16%, Yb 0.04-0.08%, Hf 0.05-0.09%, Ag 0.02-0.05%, B 0.008-0.015%, Mg 0.005-0.015%. Within this preferred composition range, the synergistic effect of each element is more significant, which is beneficial for further optimizing the overall performance.

[0014] Core Mechanism Explanation: This invention utilizes a specific ratio of Er and Yb rare earth elements, combined with Hf and Zr, to construct a core-shell structured nanoprecipitate phase with a compositional gradient within an aluminum matrix. Er preferentially combines with Al and Zr to form a high-density core; Yb, due to its larger atomic radius and slower diffusion rate, accumulates around the core and synergizes with Hf to form a slowly diffusing "fence" shell, significantly improving the coarsening resistance of the nanophase at high temperatures. Simultaneously, low-melting-point elements such as Sn, In, and Ag migrate directionally to the grain boundaries under the drive of subsequent processes, achieving precise control of grain boundary composition. This avoids the formation of harmful phases and optimizes the electrochemical properties of the grain boundaries, fundamentally improving the corrosion resistance of the material.

[0015] Secondly, the present invention provides a method for preparing the above-mentioned high-strength, tough, and corrosion-resistant aluminum alloy cable material, comprising the following steps: S1. Melting and Dual-Frequency Electromagnetic Purification: Melting is carried out under a protective atmosphere, and rotary jet refining is adopted. At the same time, a composite frequency electromagnetic field is applied. After refining, the mixture is placed in a pulsed magnetic field and filtered. The composite frequency electromagnetic field consists of a superposition of low and high frequencies: the low frequency is 5-10 Hz, which acts as a stirrer; the high frequency is 50-200 Hz, which acts as an oscillation. The peak value of the pulsed magnetic field is 0.3-0.8 T, the frequency is 1-5 Hz, and the settling time is 15-25 minutes.

[0016] S2. Gradient cooling continuous casting and laser selective scanning: The melt is subjected to gradient cooling continuous casting, and the resulting billet is subjected to laser selective scanning processing; The gradient cooling continuous casting employs a three-zone cooling system: an upper zone cooling rate >100℃ / s, a middle zone cooling rate of 40-60℃ / s, and a lower zone cooling rate <20℃ / s. The laser selective scanning utilizes a high-energy laser beam with a power density of 10. 3 -10 4 W / cm 2 The scanning speed is 1-5 m / s, and it is performed immediately after the billet exits the continuous casting machine.

[0017] S3. Multi-pass variable temperature rolling and drawing: The billet is subjected to multi-pass variable temperature rolling, followed by drawing under a dynamic temperature field; In the multi-pass variable temperature rolling, the initial pass temperature is 500-520℃, and the final pass temperature is 280-320℃. In the dynamic temperature field drawing, the temperature fluctuates periodically between 180-250℃ at a rate of 1-5℃ / min, and the reduction of area is 60-75%.

[0018] S4. Asymmetric pulse current-ultrasonic coupling aging: Asymmetric bipolar pulse current coupled with ultrasonic aging is applied to the drawn monofilament. The asymmetric pulse current has a forward current density of 80-150 A / mm². 2 Pulse width 20-50ms; reverse current density 15-30A / mm 2 The pulse width is 5-15ms; the pulse frequency is 10-40Hz. The synchronously applied ultrasound frequency is 25-40kHz, and the power density is 0.5-2.0W / cm². 2 .

[0019] Preferably, the coupling aging treatment is carried out under a flowing inert gas protective atmosphere at a temperature of 280-320℃ for 20-50 minutes. This process uses directional electron wind generated by asymmetric pulsed current to drive solute atoms such as Sn, In, and Ag to migrate directionally towards the grain boundaries, achieving precise control of grain boundary composition; simultaneously, the cavitation and acoustic flow effects of ultrasound synergistically promote the uniform nucleation and dispersed distribution of nano-precipitates.

[0020] S5. Alternating tension relaxation stabilization treatment: The monofilament after coupling aging is subjected to alternating tension relaxation stabilization treatment.

[0021] The alternating tension relaxation and stabilization treatment is carried out at 90-120℃, with the applied tension amplitude alternating periodically. The average value is 12-18% of the yield strength of the single filament, the alternation amplitude is ±3-5%, the frequency is 0.01-0.1Hz, and the treatment time is 10-24 hours.

[0022] Thirdly, the present invention provides a power cable comprising a conductor made of multiple strands of monofilaments twisted together, wherein the monofilaments are made of the aluminum alloy material described in the first aspect above.

[0023] Furthermore, in the conductor, at least a portion of the monofilament surface has a ceramic oxide film generated by micro-arc oxidation, and the ceramic oxide film is doped with Sn, In, and Ag elements.

[0024] Preferably, the thickness of the ceramic oxide film is 1-5 μm. This surface modification layer can further improve the surface hardness and corrosion resistance of the monofilament while maintaining the high conductivity of the core.

[0025] Furthermore, the strand gaps of the conductor are filled with a composite anti-corrosion paste, which contains microcapsules carrying corrosion inhibitors and graphene-modified flake zinc powder.

[0026] Preferably, the corrosion inhibitor is benzotriazole (BTA), and the matrix of the composite anticorrosive paste is an ionic liquid with temperature-dependent viscosity, which can reduce viscosity when the conductor is heated, better fill micro-gaps, and achieve dynamic protection.

[0027] Furthermore, in the power cable, the core load-bearing monofilament undergoes complete S1-S5 steps; the outer conductive monofilament undergoes micro-arc oxidation surface modification treatment after step S4 to form the ceramic oxide film doped with Sn, In, and Ag elements.

[0028] The beneficial effects of this invention are as follows: (1) Innovative composition design: By synergistically combining Er-Yb-Hf-Zr multi-element rare earth elements, a core-shell structured nano-precipitate phase was constructed without relying on expensive Sc elements, achieving a strengthening effect superior to Sc-containing alloys and significantly reducing material costs.

[0029] (2) Dual regulation of intracrystalline and grain boundary: On the one hand, a high-density core-shell structure nanoprecipitates are formed in the crystal to achieve fine grain strengthening and precipitation strengthening; on the other hand, the grain boundary composition is precisely regulated by the directional migration of elements such as Sn, In, and Ag, which fundamentally improves the corrosion resistance of the material and solves the problem of intergranular corrosion of traditional Mg-containing alloys.

[0030] (3) Integrated innovation of preparation process: Dual-frequency electromagnetic purification: Through the synergy of low-frequency stirring and high-frequency oscillation, deep purification of the melt is achieved, which is more effective than single-frequency treatment; Laser Selective Scanning (LSS): Replacing traditional induction heating tempering, it uses a high-energy laser beam to achieve instantaneous surface melting and coagulation, resulting in more concentrated energy and more controllable tissue gradient; Asymmetric pulse-ultrasound coupled aging: Asymmetric pulsed current generates directional electron wind, which, in synergy with ultrasonic cavitation / acoustic flow effect, greatly promotes solute atom diffusion and nanophase nucleation. The mechanism and equipment are different from conventional pulsed current aging. Alternating tension relaxation: Dynamically eliminates microscopic residual stress by periodically alternating tension, thereby improving the dimensional stability of monofilaments.

[0031] (4) Excellent comprehensive performance: The aluminum alloy material has a tensile strength ≥350 MPa, conductivity ≥60.5% IACS, salt spray corrosion resistance is better than that of Sc alloy, and creep resistance is significantly improved, which can meet the long-term service requirements of power cables in harsh environments. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] This invention provides an aluminum alloy material for high-strength, tough, and corrosion-resistant aluminum alloy cables. This material does not contain artificially added scandium (Sc) element. Through the synergistic ratio of multiple rare earth elements Er-Yb-Hf-Zr, a nano-precipitated phase with a core-shell structure is constructed in the aluminum matrix, and the grain boundary composition is precisely controlled simultaneously.

[0034] The composition of the aluminum alloy material, by weight percentage, includes: Fe 0.60-0.95%, Si 0.08-0.18%, Cu 0.05-0.20%, Sn 0.02-0.10%, In 0.008-0.05%, Zr 0.08-0.15%, Er 0.08-0.20%, Yb 0.02-0.10%, Hf 0.03-0.12%, Ag 0.01-0.08%, B 0.003-0.02%, Mg≤0.03%, balance Al and unavoidable impurities.

[0035] The total impurity content is ≤0.10%, the content of any single impurity (excluding Sc) is ≤0.02%, and the content of Sc as an impurity is ≤0.005%. By strictly controlling the impurity content, especially Sc as the upper limit for impurities, the purity of the material is ensured while avoiding adverse effects on performance caused by excessive impurities.

[0036] The specific elemental combinations and their content ranges mentioned above can produce a synergistic effect: Fe and Si form dispersed fine second-phase particles, contributing a certain strengthening effect without excessively damaging conductivity; Cu, Ag, Sn, and In work synergistically to optimize precipitation behavior in subsequent aging treatment; the combination of Zr, Er, Yb, and Hf is the key to achieving high strength and high conductivity synergistically in this invention, forming nano-precipitates with special structures in the aluminum matrix; B is used to refine grains and improve processing performance; the Mg content is strictly controlled below 0.03% to avoid intergranular corrosion caused by the Al3Mg2 phase, which is prone to occur in traditional Mg-containing aluminum alloys.

[0037] Preferably, in the aluminum alloy material, the weight ratio of Er to Yb is between 2:1 and 8:1. Within this preferred ratio range, Er can dominate the formation of high-density nucleation cores, while Yb, due to its larger atomic radius and slower diffusion rate, tends to accumulate around the core during subsequent processing, synergistically interacting with the simultaneously added Hf to lay the compositional foundation for the final formation of nanoprecipitates with a special gradient structure. When the Er / Yb ratio is lower than 2:1, the relatively high Yb content may lead to insufficient nucleation core density; when it is higher than 8:1, the "fence" effect of Yb weakens, and the coarsening resistance of the nanophase decreases.

[0038] More preferably, the composition range of the aluminum alloy material is: Fe 0.65-0.80%, Si 0.09-0.12%, Cu 0.08-0.15%, Sn 0.03-0.06%, In 0.01-0.04%, Zr 0.09-0.12%, Er 0.10-0.16%, Yb 0.04-0.08%, Hf 0.05-0.09%, Ag 0.02-0.05%, B 0.008-0.015%, Mg 0.005-0.015%. Within this preferred composition range, the synergistic effect among the elements is more significant, the quantity and distribution of beneficial phases formed by Fe and Si are more ideal, the utilization rate of rare earth elements is higher, and the roles of Sn, In, and Ag in grain boundary regulation are more prominent, thus contributing to obtaining superior overall performance.

[0039] The aluminum alloy material contains dispersed nano-precipitates in its microstructure. These nano-precipitates possess a gradient shell structure with Al3(Er,Yb,Zr) as the core and Hf enriched on the periphery. This unique core-shell structure is a key feature of this invention: the core region is rich in Er, Yb, and Zr, forming a high-density, thermally stable, ordered phase; the shell region is enriched in Hf, which, due to its slow diffusion rate, forms a "fence" that effectively hinders the coarsening of the core phase. This structure allows the nano-precipitates to maintain a fine and dispersed distribution even under high-temperature service conditions, continuously playing a role in pinning grain boundaries and hindering dislocation movement.

[0040] Thanks to the aforementioned composition design and microstructure characteristics, in one specific embodiment, the aluminum alloy material exhibits a conductivity ≥60.5% IACS and a tensile strength ≥350 MPa. This performance specification overcomes the bottleneck of traditional aluminum alloy materials where strength and conductivity are difficult to balance, providing a material foundation for the long-term stable operation of power cables in harsh environments.

[0041] Core Mechanism Explanation: This invention constructs a core-shell nano-precipitate with a compositional gradient in an aluminum matrix by using a specific ratio of Er and Yb rare earth elements, combined with Hf and Zr. Er preferentially combines with Al and Zr to form a high-density core; Yb, due to its larger atomic radius and slower diffusion rate, accumulates around the core and works synergistically with Hf to form a slowly diffusing "fence" shell, significantly improving the coarsening resistance of the nano-phase at high temperatures. Simultaneously, low-melting-point elements such as Sn, In, and Ag migrate directionally to the grain boundaries under the drive of subsequent processes, achieving precise control of grain boundary composition. This grain boundary control mechanism, on the one hand, avoids the formation of harmful phases (such as the Al3Mg2 phase), and on the other hand, optimizes the electrochemical properties of the grain boundaries, making it difficult for corrosive media to spread along the grain boundaries, thereby fundamentally improving the corrosion resistance of the material.

[0042] This invention also provides a method for preparing the above-mentioned aluminum alloy material, which achieves precise control of the microstructure throughout the entire process from melt purification to final stabilization treatment through the sequential regulation of multiple physical fields. In one embodiment, the preparation method includes the following steps S1 to S5.

[0043] S1. Smelting and Dual-Frequency Electromagnetic Purification Melting is carried out under a protective atmosphere using a rotary jet refining process, while a composite frequency electromagnetic field is applied to assist refining. This composite frequency electromagnetic field is a superposition of low and high frequencies: the low frequency (5-10 Hz) primarily acts as a stirrer, promoting homogenization of the melt composition and enrichment of inclusions into the slag layer; the high frequency (50-200 Hz) primarily acts as an oscillator, generating cavitation in the melt, breaking up agglomerated inclusions and causing them to float. After refining, the melt is allowed to stand for 15-25 minutes in a pulsed magnetic field with a peak value of 0.3-0.8 T and a frequency of 1-5 Hz, followed by filtration.

[0044] Through the synergistic effect of low-frequency stirring and high-frequency oscillation, this step achieves deep purification of the melt, with a purification effect superior to single-frequency electromagnetic treatment. The pulsed magnetic field further promotes the collisional growth and flotation of residual inclusions, providing a high-purity melt for subsequent molding. This is fundamental to ensuring the conductivity and corrosion resistance of the final product.

[0045] S2. Gradient Cooling Continuous Casting and Laser Selective Scanning The purified melt is subjected to gradient cooling continuous casting using a three-zone cooling method: strong cooling in the upper zone (cooling rate >100℃ / s); moderate cooling in the middle zone (cooling rate 40-60℃ / s); and weak cooling in the lower zone (cooling rate <20℃ / s). Immediately after exiting the continuous casting machine, the surface of the billet is subjected to selective scanning (LSS) along a specific path using a high-energy laser beam with a laser power density of 10. 3 -10 4 W / cm 2 The scanning speed is 1-5 m / s.

[0046] Gradient cooling continuous casting enables the billet to achieve differentiated solidification structures in different thickness regions, providing a microstructural basis for subsequent processing. Laser selective scanning replaces traditional induction heating tempering or homogenization treatments, with a more concentrated energy input: high-power-density lasers induce instantaneous melting of surface micro-regions, followed by rapid solidification, forming an extremely fine recrystallized layer on the billet surface. Simultaneously, due to heat conduction, significant temperature and stress gradients are formed from the surface inwards. This gradient microstructure facilitates uniform and coordinated deformation during subsequent rolling and drawing processes, while the fine-grained surface structure helps improve the surface properties of the final product.

[0047] S3. Multi-pass variable temperature rolling and drawing The laser-scanned billet is subjected to multi-pass variable-temperature rolling, with the initial pass temperature at 500-520℃ and the final pass temperature reduced to 280-320℃. The resulting wire rod is then drawn under a dynamic temperature field, with the temperature fluctuating periodically between 180-250℃ at a rate of 1-5℃ / min, and the reduction of area is 60-75%.

[0048] The design of variable-temperature rolling, from high-temperature initial rolling to low-temperature final rolling, allows for gradual refinement of the deformed microstructure and control of internal stress. Drawing under a dynamic temperature field, through periodic temperature fluctuations, promotes dynamic recovery of dislocations during deformation, preventing excessive accumulation of work hardening and facilitating the acquisition of a uniform and fine fibrous microstructure, thus providing a good microstructure foundation for subsequent aging treatment.

[0049] S4. Asymmetric pulsed current-ultrasonic coupling aging The drawn monofilaments are subjected to asymmetric bipolar pulsed current coupled with ultrasonic aging treatment. The asymmetric pulsed current parameters are: forward current density 80-150 A / mm². 2 Pulse width 20-50ms; reverse current density 15-30A / mm 2 The pulse width is 5-15ms; the pulse frequency is 10-40Hz. The synchronously applied ultrasound frequency is 25-40kHz, and the power density is 0.5-2.0W / cm². 2 .

[0050] Preferably, the coupling aging treatment is carried out in a flowing inert gas protective atmosphere at a temperature of 280-320°C for 20-50 minutes.

[0051] The forward current density of the asymmetric pulsed current is much higher than that of the reverse current, generating a significant "directional electron wind" effect. This directional electron wind can drive specific solute atoms (especially Sn, In, Ag, and some rare earth elements with larger atomic radii) to migrate in a specific direction: on the one hand, it promotes the uniform nucleation of nano-precipitates, making the precipitate distribution more diffuse; on the other hand, it drives these elements to concentrate towards the grain boundaries, achieving precise control of grain boundary composition. Simultaneously applied ultrasound generates cavitation and acoustic flow effects within the material: the instantaneous high temperature and pressure generated by the collapse of cavitation bubbles promotes local atomic diffusion, and the acoustic flow effect enhances the transport process of solute atoms. These effects, combined with the directional electron wind, greatly promote solute atom diffusion and nano-phase nucleation, with significantly better results than single-physical-field treatment. This mechanism and equipment are distinct from conventional symmetric AC pulse or simple DC pulse aging.

[0052] S5. Alternating tension relaxation stabilization treatment The coupled-aged monofilaments are subjected to alternating tension relaxation stabilization treatment. The treatment temperature is 90-120℃, the applied tension amplitude is periodically alternating, the average value is 12-18% of the monofilament yield strength, the alternation amplitude is ±3-5%, the frequency is 0.01-0.1Hz, and the treatment time is 10-24 hours.

[0053] Traditional stabilization treatments often employ constant tension or simple thermal relaxation, which are insufficient to completely eliminate complex microscopic residual stress fields. This step introduces a dynamic load through alternating tension: the periodically alternating tension induces reciprocating slip and rearrangement of dislocations in areas of concentrated residual stress within the material, thereby releasing microscopic internal stress with lower energy consumption. This dynamic relaxation method can more effectively eliminate microscopic residual stress, significantly improving the dimensional stability and creep resistance of the monofilament during subsequent stranding and long-term service.

[0054] The present invention also provides a power cable comprising a conductor made of multiple strands of monofilaments twisted together, wherein the monofilaments are made of the aforementioned aluminum alloy material.

[0055] In a preferred embodiment, at least a portion of the monofilaments in the conductor have a ceramic oxide film formed by micro-arc oxidation, wherein the ceramic oxide film is doped with Sn, In, and Ag elements. The micro-arc oxidation treatment can be performed after step S4 and before stranding, adding this surface modification step for the outer conductive monofilaments.

[0056] For example, the thickness of the ceramic oxide film is 1-5 μm. This thickness range is set based on the following considerations: if it is too thin (<1 μm), it is difficult to form a continuous and complete protective layer, resulting in limited protective effect; if it is too thick (>5 μm), it may affect the flexibility and conductivity of the monofilament. By doping with Sn, In, and Ag elements, the conductivity and electrochemical properties of the ceramic film can be further optimized, so that the surface modification layer can significantly improve the surface hardness and corrosion resistance of the monofilament while maintaining the high conductivity of the core.

[0057] In another preferred embodiment, the strand gaps of the conductors are filled with a composite anti-corrosion paste. The composite anti-corrosion paste comprises microcapsules carrying corrosion inhibitors and graphene-modified flake zinc powder.

[0058] For example, the corrosion inhibitor is benzotriazole (BTA). The matrix of the composite anticorrosive paste is an ionic liquid with thermochromic viscosity, which can reduce viscosity when the conductor heats up, better fill micro-gaps, and achieve dynamic protection. This composite anticorrosive paste is designed with multiple protection mechanisms: microcapsules rupture to release the corrosion inhibitor when localized corrosion occurs, achieving active protection; graphene-modified sheet zinc powder provides cathodic protection, while the two-dimensional sheet structure of graphene can block the penetration of corrosive media; and the thermochromic viscosity matrix ensures the filling effect under different operating conditions.

[0059] In a specific cable structure design, the core load-bearing monofilament undergoes complete S1-S5 processing steps to ensure maximum strength and dimensional stability. The outer conductive monofilament undergoes micro-arc oxidation surface modification treatment after step S4 to form a ceramic oxide film doped with Sn, In, and Ag elements, thereby improving surface corrosion resistance. This functional division of labor between the inner and outer layers optimizes surface protection while ensuring the overall mechanical properties of the cable.

[0060] To better understand the beneficial effects of the technical solution of this invention, specific embodiments and comparative examples are provided below for comparison and illustration. Examples 1-3 were prepared according to the chemical composition range and preparation method described in this invention; Comparative Example 1 is a traditional 6201 series aluminum alloy, representing the existing Mg-Si strengthening route; Comparative Example 2 is a Sc-containing aluminum alloy, representing the existing rare earth strengthening route. The specific alloy composition of each embodiment and comparative example is shown in Table 1, where unmarked element contents indicate that they were not intentionally added or that the content was below the detection limit.

[0061] Table 1: Alloy composition design (wt%, balance is Al and impurities) The preparation method of the aluminum alloy material described in Example 1 is as follows: S1. Melting and Dual-Frequency Electromagnetic Purification: A combined low-frequency 8Hz and high-frequency 100Hz electromagnetic field is used for auxiliary refining, followed by standing in a pulsed magnetic field with a peak value of 0.5T and a frequency of 2Hz for 20 minutes and then filtering.

[0062] S2. Gradient Cooling Continuous Casting and Laser Selective Scanning: Continuous casting employs a three-zone gradient cooling system, with cooling rates of 100℃ / s in the upper zone, 50℃ / s in the middle zone, and 15℃ / s in the lower zone. Laser selective scanning is performed immediately after the billet exits the continuous casting machine, with a power density of 3×10⁻⁶. 3 W / cm 2 Scanning speed: 3 m / s.

[0063] S3, Multi-pass variable temperature rolling and drawing: The initial rolling pass temperature is 510℃, and the final rolling pass temperature is 300℃; then drawing is carried out under a dynamic temperature field with periodic fluctuations at a rate of 3℃ / min between 200-230℃.

[0064] S4. Asymmetric pulse current-ultrasonic coupling aging: The asymmetric pulse current parameter is 120A / mm in the positive direction. 2 / 30ms, reverse 25A / mm 2 / 10ms, frequency 25Hz, synchronous application frequency 30kHz, power 1.2W / cm 2 The ultrasound was treated at 300°C for 35 minutes under the protection of flowing inert gas.

[0065] S5. Alternating tension relaxation and stabilization treatment: Apply periodic alternating tension with an average value of 15% of the single filament yield strength, alternating amplitude ±4%, and frequency of 0.05Hz at 110℃ for 15h.

[0066] The preparation process parameters for Examples 2 and 3 are basically the same as those for Example 1, with only some parameters adjusted adaptively according to their respective compositional characteristics. Comparative Examples 1 and 2 employ conventional industrial preparation processes for the corresponding alloys.

[0067] Performance Tests and Results: The prepared Φ3.0 mm monofilament was tested, and the results are shown in Table 2.

[0068] Table 2: Comparison of Performance Test Results As can be seen from the test results in Table 2: First, the performance is superior without the addition of Sc. In the absence of any added scandium, the embodiments of this invention achieve a conductivity of 61.5-62.5% IACS and a tensile strength of 368-390 MPa. These core indicators are significantly better than Comparative Example 2 (conductivity 59.8% IACS, tensile strength 355 MPa) containing 0.12% Sc, demonstrating the superiority of the Er-Yb-Hf-Zr multi-element rare earth synergistic system.

[0069] Second, its overall performance is superior. Regarding corrosion resistance, the salt spray weight loss of this invention embodiment is 2.5-3.0 g / m³. 2 ) is only for comparative example 2 (8.5g / m 2 The creep rate was about 1 / 3 of that of Comparative Example 2 (0.095%); in terms of creep resistance, the creep rate at 120℃ / 1000h (0.055-0.065%) was reduced by about 40% compared with Comparative Example 2 (0.095%). This verifies the effectiveness of the dual mechanism of "core-shell structure strengthening" and "grain boundary composition regulation".

[0070] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0071] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An aluminum alloy material for high-strength, tough, and corrosion-resistant aluminum alloy cables, characterized in that, Excluding artificially added scandium (Sc), its composition by weight percentage includes: Fe 0.60-0.95%, Si 0.08-0.18%, Cu 0.05-0.20%, Sn 0.02-0.10%, In 0.008-0.05%, Zr 0.08-0.15%, Er 0.08-0.20%, Yb 0.02-0.10%, Hf 0.03-0.12%, Ag 0.01-0.08%, B 0.003-0.02%, Mg ≤ 0.03%, with the balance being Al and unavoidable impurities, of which Sc, as an impurity, has a content ≤ 0.005%.

2. The aluminum alloy material for high-strength, tough, and corrosion-resistant aluminum alloy cables according to claim 1, characterized in that, The weight ratio of Er to Yb is 2:1 to 8:

1.

3. The aluminum alloy material for high-strength, tough, and corrosion-resistant aluminum alloy cables according to claim 1, characterized in that, Its microstructure contains a nano-precipitated phase with a gradient shell structure of Al3(Er,Yb,Zr) as the core and Hf enriched on the periphery, and has a conductivity ≥60.5% IACS and a tensile strength ≥350MPa.

4. A method for preparing an aluminum alloy material for high-strength, tough, and corrosion-resistant aluminum alloy cables as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. The alloy melt is refined with the assistance of a dual-frequency electromagnetic field, and then allowed to stand and be filtered in a pulsed magnetic field; S2. The melt is subjected to gradient cooling continuous casting, and the resulting billet is subjected to laser selective area scanning processing; S3. The billet is subjected to multi-pass variable temperature rolling, followed by drawing under a dynamic temperature field; S4. Perform asymmetric pulse current and ultrasonic coupling aging treatment on the drawn monofilament; S5. Perform alternating tension relaxation stabilization treatment on the monofilament after coupling aging.

5. The preparation method according to claim 4, characterized in that, The laser selective scanning in step S2 uses a high-energy laser beam with a power density of 10. 3 -10 4 W / cm 2 The scanning speed is 1-5 m / s.

6. The preparation method according to claim 4, characterized in that, The asymmetric pulsed current coupled with ultrasonic waves in step S4 involves an asymmetric bipolar pulsed current with a forward current density of 80-150 A / mm². 2 The reverse current density is 15-30 A / mm. 2 The pulse frequency is 10-40Hz; the synchronously applied ultrasonic frequency is 25-40kHz.

7. The preparation method according to claim 4, characterized in that, The coupling aging treatment in step S4 is carried out under the protection of flowing inert gas, at a temperature of 280-320℃, for a time of 20-50 minutes.

8. A power cable comprising a conductor made of multiple strands of monofilament twisted together, characterized in that, The monofilament is made of the aluminum alloy material described in any one of claims 1-3, wherein a portion of the monofilament surface has a ceramic oxide film doped with Sn, In, and Ag elements generated by micro-arc oxidation.

9. The power cable according to claim 8, characterized in that, The strand gaps of the conductors are filled with a composite anti-corrosion paste, which contains microcapsules carrying corrosion inhibitors and graphene-modified flake zinc powder.

10. The power cable according to claim 8, characterized in that, The thickness of the ceramic oxide film is 1-5 μm.

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