A heat-resistant creep-resistant aluminum alloy wire and a method for manufacturing the same

Abstract

The application discloses a heat-resistant and creep-resistant aluminum alloy wire and a preparation method thereof, and belongs to the field of aluminum alloy conductive cable material preparation. The aluminum alloy wire is composed of the following components in percentage by mass: Fe 0.25-0.75%, Ni 0.25-0.75%, Me 0.2-1%, and the balance of aluminum and inevitable impurities; the Me is composed of La, Nd, Sc, Zr and Ce. The application introduces fixed proportions of Fe and Ni into an aluminum matrix, simultaneously introduces specific types of mixed rare earth elements, Sc and Zr elements, and utilizes large-strain extrusion, multi-pass continuous drawing, deep cryogenic treatment and continuous heat treatment technology, so that multiple nanoscale precipitated phases are precipitated in the aluminum matrix grain and micron-sized dispersion strengthening phases are formed at the grain boundaries, and the strength, elongation, electrical conductivity and creep resistance of the aluminum alloy wire are improved in a multi-scale and multi-type alloy phase synergy.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy conductive cable material preparation technology, and relates to a heat-resistant and creep-resistant aluminum alloy wire and its preparation method. Background Technology

[0002] Faced with the urgent needs of major infrastructure construction such as ultra-high voltage power transmission and high-speed railways, aluminum alloy conductive cables, with their lightweight, resource self-sufficiency and controllability, and excellent comprehensive performance, have become the most promising cable material for saving copper conductors. However, their development is fundamentally limited by the challenge of balancing the strength and conductivity of aluminum alloy materials themselves. Traditional techniques for the composition design and forming of aluminum alloy cable materials, in order to improve the mechanical strength and heat resistance of aluminum alloy cables, have added alloying elements that cause lattice distortion of the aluminum matrix and increase the solute atomic content. This leads to a sharp decrease in the conductivity of aluminum alloy cable materials, thus creating a contradiction between the two key performance characteristics of strength and conductivity.

[0003] There are reports on methods to improve certain aspects of the performance of aluminum alloy cables. For example, Chinese patent application CN108893660A discloses a high-conductivity aluminum alloy conductor and its preparation process. This aluminum alloy conductor improves its conductivity by adding various alloying elements such as Mg, Si, Cu and rare earth elements. Its preparation process involves multiple steps such as vacuum melting, element addition, composition detection, casting, rolling, heat treatment and wire drawing. It achieves a conductivity of up to 62.1% IACS and an alloy strength of 175 MPa for the aluminum alloy conductive cable material, but its elongation is only 5.1%.

[0004] In addition, patents related to aluminum alloy conductors with excellent comprehensive performance have maintained high popularity. For example, Chinese patent application CN121467690A discloses a high-modulus, high-conductivity, heat-resistant aluminum alloy material, aluminum conductor, preparation method, and power transmission cable. It employs a multi-stage plastic processing method of hot extrusion, continuous rolling, drawing, and surface treatment, refining the grain structure through dynamic recrystallization during processing. Meanwhile, Chinese patent application CN 118531244A discloses an aluminum alloy conductor, its preparation method, and applications. This method improves the uniformity and density of the material's microstructure by incorporating Si, Fe, Mg, Zr, Cu, and Cr into aluminum, combined with hot drawing, cold drawing, and cryogenic treatment. The aluminum alloy conductors obtained by these methods exhibit good strength and conductivity, but poor elongation and lack heat resistance and creep resistance.

[0005] However, as the power industry continues to increase its requirements for the comprehensive physical and mechanical properties of aluminum alloy conductors during application, there is an urgent need for aluminum alloy conductors to not only ensure high conductivity but also have better mechanical strength, especially excellent creep resistance under long-term high temperature and low stress conditions. Summary of the Invention

[0006] To address the problems existing in the prior art, the first objective of this invention is to provide a heat-resistant and creep-resistant aluminum alloy wire. By introducing a fixed proportion of Fe and Ni into the matrix, and simultaneously introducing specific types of rare earth elements and Zr elements, a variety of nanoscale precipitates and micron-scale dispersed strengthening phases are formed at the grain boundaries and within the matrix, ultimately synergistically improving the strength, conductivity, elongation, and creep resistance of the aluminum alloy wire.

[0007] The second objective of this invention is to provide a method for preparing heat-resistant and creep-resistant aluminum alloy wires. This method utilizes high-strain extrusion and multi-pass continuous drawing to fully break down the internal grains and coarse second phases of the aluminum alloy matrix. This allows fine, micron-scale dispersed strengthening phases Al9 (Fe, Ni) to be distributed at the grain boundaries to resist high-temperature creep. In conjunction with cryogenic treatment and continuous heat treatment, nanoscale rare-earth-containing second phases precipitated within the aluminum matrix grains stabilize the internal microstructure of the aluminum alloy and guide the precipitation sequence of the alloy's second phases, reducing lattice distortion. This improves the mechanical properties of the aluminum alloy wires while maintaining high conductivity.

[0008] To achieve the above technical objectives, this invention provides a heat-resistant and creep-resistant aluminum alloy conductor. The material, by mass percentage, has the following composition: Fe 0.25~0.75%, Ni 0.25~0.75%, Me 0.2~1%, with the balance being aluminum and unavoidable impurities. The Me, by mass percentage, has the following composition: La 20~25%, Nd 10~15%, Sc 3~5%, Zr 3~5%, with the balance being Ce. The ratio of Fe to Ni is 1:(1~1.05), and the ratio of Sc to Zr is 1:(1~1.05). The aluminum alloy conductor contains nano-sized Al. 11 Ce3 precipitates, nano-sized Al 11 La3 precipitates, nano-sized Al 11 The mixture comprises Nd3 precipitates, nanoscale Al3(Sc,Zr) precipitates, and micron-scale Al9(Fe,Ni) dispersed phases; wherein the nanoscale Al3(Sc,Zr) precipitates are coherent with the aluminum matrix.

[0009] In the technical solution of this invention, Al-Me, which has the effect of grain refinement and precipitation strengthening, is added to the aluminum matrix through alloy composition design, thereby forming nanoscale Al in the aluminum matrix. 11 Ce3 precipitates, nano-sized Al 11 La3 precipitates, nano-sized Al 11Nd3 precipitates, these rare earth precipitates, possess high thermal stability and can effectively improve the strength and thermal stability of aluminum alloys. Nanoscale Al3(Sc,Zr) precipitates, formed by adding them in a specific ratio, are coherent with the aluminum matrix and do not cause severe lattice distortion. They effectively control the recrystallization process of the aluminum matrix during high-temperature heat treatment, playing a role in grain refinement and stabilizing the microstructure, further improving the mechanical properties of the aluminum alloy. Meanwhile, micron-sized Al9(Fe,Ni) dispersed phases, formed by adding them in a specific ratio and breaking them down during large strain deformation, exhibit excellent thermal stability and dispersion strengthening effects, stabilizing the grain boundaries of the aluminum matrix at high temperatures. The synergistic effect of these micron-sized Al9(Fe,Ni) dispersed phases and the rare earth-containing nanoscale precipitates can effectively improve the strength and creep resistance of aluminum alloy conductors at high temperatures. Because the types and sizes of nano- and micro-phases in the alloy have been effectively controlled, the nano-phases are mainly distributed within the grains while the micro-phases are distributed at the grain boundaries. The various second phases do not disrupt the continuity of the aluminum matrix, thus ensuring that the aluminum alloy has high elongation and excellent electrical conductivity.

[0010] In this invention, "Fe 0.25~0.75%, Ni 0.25~0.75%" is intended to indicate that both Fe and Ni can be selected within this content range, but the ratio of Fe to Ni must be 1:(1~1.05). Similarly, the same applies to Sc and Zr.

[0011] Furthermore, in the combination of Me selected in this invention, the synergistic use of Ce, La, Nd, Sc and Zr can improve the elongation and creep resistance of aluminum alloys while reducing the raw material cost of the alloys.

[0012] As a preferred embodiment, the aluminum alloy wire has the following composition by mass percentage: Fe 0.5~0.6%, Ni 0.5~0.6%, Me 0.6~1%, with the balance being aluminum and unavoidable impurities.

[0013] Further preferably, the composition of Me by mass percentage is as follows: Ce 50%, La 25%, Nd 15%, Sc 5%, Zr 5%. Within the further preferred composition range, aluminum alloy wires with finer and more uniformly distributed precipitated and dispersed phases and superior overall performance can be obtained.

[0014] As a preferred option, Al9(Fe,Ni) can be fully broken down into micron-sized dispersed phases through large strain plastic deformation, which are distributed on the grain boundaries of the aluminum alloy matrix. This can effectively suppress grain boundary movement at high temperatures, thereby giving the aluminum matrix good creep resistance.

[0015] This invention also provides a method for preparing a heat-resistant and creep-resistant aluminum alloy wire, the method comprising the following steps:

[0016] S1 Weigh each component raw material according to the designed aluminum alloy wire assembly ratio and melt it. After all the raw materials have melted, add refining agent to refine and degas the material to obtain aluminum alloy melt.

[0017] S2 Adjust the temperature of the aluminum alloy melt to 700~720℃ and then cast it to obtain an aluminum alloy ingot;

[0018] S3 The aluminum alloy ingot is subjected to heat treatment, hot extrusion plastic deformation with an extrusion ratio ≥30 and a first deep cryogenic treatment in sequence to obtain an aluminum alloy round rod;

[0019] The aluminum alloy round rod described in S4 is subjected to multiple continuous drawing passes at room temperature. The resulting wire undergoes a second cryogenic treatment and continuous heat treatment. After cooling, the aluminum alloy wire is obtained.

[0020] Under the alloy system design of this invention, when the preparation method of this invention is adopted, a special precipitate structure and distribution can be obtained, thereby enabling aluminum alloy wires to simultaneously possess good mechanical strength, electrical conductivity, elongation and creep resistance.

[0021] The principle of the preparation process of this invention is as follows: First, during the heat treatment of the ingot, the added alloying elements, especially rare earth elements, can be fully dissolved in the aluminum matrix to form a solid solution at high temperature. With rapid cooling, a supersaturated solid solution is formed, which is beneficial for the precipitation of nano-sized rare earth-containing and metallographic phases from the aluminum matrix during subsequent continuous heat treatment to form a strengthening phase, thereby improving the mechanical properties of the aluminum alloy, such as room temperature strength. Subsequently, hot extrusion plastic deformation with a high extrusion ratio is used to apply strong shear force and compressive stress to the aluminum alloy ingot, causing the coarse grains in the as-cast structure to undergo severe fragmentation and dynamic recrystallization, thereby generating a large number of microstructures such as vacancies, dislocations, subgrain boundaries, and grain boundaries in the aluminum matrix. At the same time, the Al9(Fe,Ni) phase is fully fragmented and forms a micron-sized dispersed phase, distributed on the grain boundaries of the aluminum alloy matrix, while ensuring that the nano-sized Al3(Sc,Zr) precipitates are coherently distributed with the aluminum matrix. The subsequent first cryogenic treatment uses an extremely low temperature environment to suppress the thermal movement of dislocations, stabilizing the microstructure and grain structure formed after extrusion. During the multi-pass continuous drawing process, the aluminum alloy rod further accumulates strain, and the grains are continuously refined to the submicron or even nanometer level, further increasing the dislocation density. The second cryogenic treatment introduced at this point not only effectively freezes the concentration and distribution of vacancies, dislocations, and grain boundaries in the material, but more importantly, through ultra-low temperature induction, guides the precipitation sequence of the alloy's second phase during subsequent continuous heat treatment aging. This promotes the uniform precipitation of the strengthening phase in a finer, more dispersed form, which is beneficial for improving the conductivity of the aluminum matrix. This not only more efficiently improves the material's strength and heat resistance, but also reduces the scattering of electrons by lattice distortion by promoting the complete extrusion of solute atoms from the aluminum matrix, thereby maintaining or improving conductivity at higher strength levels.

[0022] In this invention, the extrusion ratio of hot extrusion plastic deformation needs to meet the requirement of ≥30. If the extrusion ratio is too small, the amount of plastic deformation is too small to ensure that the internal microstructure configuration required by the aluminum alloy of this invention can be obtained.

[0023] As a preferred embodiment, the raw materials are aluminum ingots, Al-Fe master alloys, Al-Ni master alloys and Al-Me master alloys with a purity of ≥99.9%. During the melting process, the aluminum ingots are first heated to 730~750℃ to melt, and then the Al-Fe master alloy, Al-Ni master alloy and Al-Me master alloy are added sequentially to melt.

[0024] Furthermore, after all the alloy raw materials are added, the aluminum alloy melt is ultrasonically stirred at 2 / 3 depth using an ultrasonic generator for 10-15 minutes.

[0025] As a preferred embodiment, the refining agent is hexachloroethane, and its dosage is 1 to 3 wt% of the total weight of the melt.

[0026] Furthermore, the melt is allowed to stand for 10-20 minutes before temperature adjustment.

[0027] As a preferred embodiment, the surface oxide layer of the aluminum alloy ingot is removed by turning before heat treatment.

[0028] As a preferred embodiment, the heat treatment process involves first holding the ingot at 480-500℃ for 4-6 hours, then raising the temperature to 520-530℃ and holding for another 4-6 hours. This invention employs a two-stage homogenization heat treatment process, allowing sufficient diffusion time for the alloying elements to dissolve into the matrix. Furthermore, the two-stage heating effectively avoids the "overheating" phenomenon that can occur when directly heating to a higher temperature, leading to partial or complete ingot burn-out and rendering the entire ingot unusable.

[0029] As a preferred embodiment, the casting temperature is above 700°C.

[0030] As a preferred embodiment, the temperature of the hot extrusion plastic deformation is 400~420℃, and the preheating time is 1~1.5h.

[0031] As a preferred embodiment, the diameter of the aluminum alloy round rod is 6~10mm.

[0032] As a preferred embodiment, the temperature of the first cryogenic treatment is less than or equal to -196°C, the duration is 0.5 to 2 hours, and the temperature is raised to room temperature after the first cryogenic treatment is completed. Further, the heating time is controlled to be 0.5 to 1 hour.

[0033] As a preferred embodiment, the deformation amount of a single pass in the multi-pass continuous drawing is 20-30%, and the total deformation amount is more than 80%.

[0034] As a preferred embodiment, the temperature of the second cryogenic treatment is less than or equal to -196°C, the time is 0.5 to 2 hours, and the temperature is raised to room temperature after the second cryogenic treatment is completed. Further, the heating time is controlled to be 0.5 to 1 hour.

[0035] As a preferred embodiment, the temperature of the continuous heat treatment tube furnace is controlled at 475~500℃, and the residence time in the tube furnace is 15~60s.

[0036] As a preferred option, the cooling method is air cooling or water cooling.

[0037] In actual operation, continuous heat treatment involves feeding the wire into the tubular furnace from one end via an unwinding mechanism and receiving it from the other end via a winding mechanism. The wire is kept in the tubular furnace for 15 to 60 seconds. After the wire is heated in the tubular furnace, it is cooled by blowing cold air or spraying room temperature water mist. After cooling, aluminum alloy wire is obtained.

[0038] As a preferred embodiment, cryogenic treatment is performed between passes during the multi-pass continuous drawing process. Experiments have shown that this alternating drawing and cryogenic treatment can further improve the stability of microstructures such as vacancies, dislocations, subgrain boundaries, and grain boundaries within the aluminum matrix. In actual operation, after each wire exits the die, the wire is directly immersed in a liquid nitrogen container for approximately 30 seconds during the winding process, and then quickly returned to room temperature for the next drawing pass, thus repeating the cycle.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) This invention, through alloy composition design, adds Al-Me to the aluminum matrix to achieve grain refinement and precipitation strengthening effects, thereby forming nanoscale Al in the matrix. 11 Ce3 precipitates, nano-sized Al 11 La3 precipitates, nano-sized Al 11 Nd3 precipitates, along with the three rare earth precipitates, exhibit high thermal stability and do not coarsen below 300℃, thus enhancing the strength and creep resistance of aluminum alloys. Nanoscale Al3(Sc,Zr) precipitates, formed by adding them in specific proportions, are coherent with the aluminum matrix and do not cause severe lattice distortion. They effectively control the recrystallization process of the aluminum matrix during high-temperature heat treatment, refining grains and stabilizing the microstructure, further improving the mechanical properties of the aluminum alloy. Micron-sized Al9(Fe,Ni) dispersed phases, formed by adding them in specific proportions and breaking them down under large strain deformation, possess excellent thermal stability and dispersion strengthening effects, stabilizing the grain boundaries of the aluminum matrix at high temperatures. The synergistic effect of these micron-sized Al9(Fe,Ni) dispersed phases and the rare earth-containing nanoscale precipitates effectively enhances the strength and creep resistance of aluminum alloy conductors at high temperatures. Because the types and sizes of nano- and micro-phases in the alloy have been effectively controlled, the nano-phases are mainly distributed within the grains while the micro-phases are distributed at the grain boundaries. The various second phases do not disrupt the continuity of the aluminum matrix, thus ensuring that the aluminum alloy has high elongation and excellent electrical conductivity.

[0041] (2) The present invention generates a large number of microstructures such as vacancies, dislocations, subgrain boundaries and grain boundaries in the aluminum matrix through large strain extrusion and multi-pass continuous drawing. When large strain plastic deformation and deep cryogenic treatment are applied alternately, the stability of these microstructures can be improved. Finally, when subjected to continuous high temperature and rapid heating, they can be quickly transformed into aluminum matrix grains with small and uniform grain size. Such grain morphology is beneficial to improving the conductivity of the aluminum matrix.

[0042] (3) By performing continuous heat treatment after cryogenic treatment, the present invention can effectively freeze and regulate the concentration and distribution of vacancies, dislocations, and grain boundaries in the material through an extremely low-temperature process, thereby guiding the precipitation sequence of the alloy second phase during subsequent heat treatment aging, and promoting the uniform precipitation of the strengthening phase in a finer and more dispersed form. This operation can improve the strength and heat resistance of the material more efficiently; on the other hand, by promoting the full precipitation of solute atoms from the aluminum matrix, it can reduce the scattering of electrons by lattice distortion, providing the possibility of maintaining or even improving conductivity at a higher strength level.

[0043] (4) The preparation method of the present invention enables Al9(Fe,Ni) to be fully broken into micron-level dispersed phases when subjected to large strain plastic deformation, which are distributed on the grain boundaries of the aluminum alloy matrix, effectively suppressing the movement of grain boundaries at high temperature, thereby giving the aluminum matrix good anti-creep properties. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments and comparative examples of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a microstructure diagram showing the distribution of precipitated phases in the aluminum alloy wire prepared in Example 1 of the present invention.

[0046] Figure 2 This is a microstructure diagram showing the distribution of precipitated phases in the aluminum alloy wire prepared in Example 2 of the present invention.

[0047] Figure 3 This is a microstructure diagram showing the distribution of precipitated phases in the aluminum alloy wire prepared in Example 3 of the present invention.

[0048] Figure 4 This is a microstructure diagram of the aluminum alloy wire material after multiple plastic deformations in Embodiment 1 of the present invention.

[0049] Figure 5 This is a microstructure image of the aluminum alloy wire material after a second cryogenic treatment and subsequent continuous heat treatment, as shown in Embodiment 1 of the present invention.

[0050] Figure 6 The Al3(Sc,Zr) precipitate is the aluminum alloy wire prepared in Example 3 of this invention.

[0051] Figure 7 This is a distribution diagram of rare earth-containing precipitates in the aluminum alloy wire prepared in Example 3 of the present invention.

[0052] Figure 8 This is a distribution diagram of the dispersed strengthening phase Al9(Fe,Ni) in the aluminum alloy wire prepared in Example 3 of the present invention. Detailed Implementation

[0053] To enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, and to make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described below.

[0054] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0055] The following detailed embodiments illustrate the preparation method of the high-strength, high-conductivity, and creep-resistant aluminum alloy wire of the present invention.

[0056] The Al-Me rare earth master alloy used in the embodiments and comparative examples of the present invention is a cerium-rich mixed rare earth alloy, wherein Me is composed of Ce, La, Nd, Sc and Zr; the aluminum-containing master alloys are melted together at 775℃~800℃ to obtain the Al-Ce-La-Nd-Sc-Zr mixed rare earth master alloy.

[0057] Example 1

[0058] S1: Design a heat-resistant and creep-resistant aluminum alloy conductor alloy composition, including the following alloying elements by mass percentage: 0.25% Fe content, 0.25% Ni content, with Fe and Ni content added in a 1:1 ratio, 0.2% Me added to the alloy in the following composition ratio: 50wt% Ce, 25wt% La, 15wt% Nd, 5wt% Sc, 5wt% Zr, with a total impurity content of less than 0.1%, and the balance being aluminum.

[0059] S2: Based on the composition and mass percentage of the designed aluminum alloy conductor, select aluminum ingots with a purity of ≥99.9%, and use Al-Fe master alloy, Al-Ni master alloy, and Al-Me master alloy as the corresponding alloying elements for batching.

[0060] S3: Heat the aluminum ingot to 730℃ in a resistance furnace and melt it. Then, add the Al-Fe master alloy, Al-Ni master alloy, and Al-Me master alloy in sequence and melt them.

[0061] S4: After all the alloys are added, ultrasonic stirring is required. Place the aluminum alloy melt with an ultrasonic generator at 2 / 3 depth of the aluminum alloy melt for ultrasonic stirring for 15 minutes.

[0062] S5: Prepare hexachloroethane powder at 1 wt% of the total melt weight, wrap it in aluminum foil, and press it into the bottom of the molten aluminum alloy using a graphite bell jar to vent and slag. After the venting reaction is complete, slowly remove the bell jar and skim off the slag generated on the surface of the molten aluminum alloy. After skimming, close the furnace door and allow the molten aluminum alloy to stand for 10 minutes. Adjust the furnace temperature to 700℃ and wait for the melt to reach the desired temperature. After standing, open the furnace lid and remove any remaining slag from the surface. The molten aluminum alloy can then be cast. After casting, allow the aluminum alloy ingot to cool naturally.

[0063] S6: Remove the surface oxide layer of the aluminum alloy ingot by turning, perform heat treatment on the ingot, hold the ingot at 480℃ for 6 hours, and then heat it to 520℃ in the furnace and hold it for 6 hours.

[0064] S7: Hot extrusion plastic deformation of the ingot. After preheating the ingot at 420℃ for 1.5 hours, hot extrusion is performed to form a round rod with a diameter of 6mm, ensuring an extrusion ratio of ≥30, followed by air cooling.

[0065] S8: The extruded aluminum alloy rod is subjected to a first cryogenic treatment by immersing it in a container filled with liquid nitrogen from room temperature and keeping it at a temperature of -196°C for 0.5 hours. Then, the rod is gradually heated to room temperature along with the container at a rate of 0.5 hours, and then the aluminum alloy rod is removed.

[0066] S9: The extruded and cryogenically treated aluminum alloy round rod is subjected to multiple continuous drawing at room temperature. The deformation of each drawing is controlled at 20%. After multiple drawing processes, the plastically deformed aluminum alloy wire material with a diameter of about 1 mm and a total deformation of more than 80% is obtained.

[0067] S10: The drawn aluminum alloy wire is subjected to a second cryogenic treatment. The wire is placed from room temperature into a container filled with liquid nitrogen and kept at a temperature of -196°C for 0.5 hours. Then, the temperature is gradually increased along with the container, and the temperature is increased back to room temperature in 0.5-hour increments. The aluminum alloy wire is then removed.

[0068] S11: The aluminum alloy wire treated with liquid nitrogen undergoes continuous heat treatment. The wire enters from one end of a tubular furnace at a temperature of 475°C through an unwinding mechanism, and then exits from the other end of the tubular furnace through a winding mechanism. The dwell time of the wire in the tubular furnace is controlled to be 15 seconds. After the wire is heated in the tubular furnace, it is cooled by water spraying. After cooling, the aluminum alloy wire is obtained.

[0069] Example 2

[0070] S1: Design a heat-resistant and creep-resistant aluminum alloy conductor alloy composition, including the following alloying elements by mass percentage: Fe content 0.75%, Ni content 0.75%, with Fe and Ni added in a 1:1 ratio, Me added in the alloy according to the composition ratio of 50wt%Ce, 25wt%La, 15wt%Nd, 5wt%Sc, and 5%Zr, with the total impurity content less than 0.1%, and the balance being aluminum.

[0071] S2: Based on the composition and mass percentage of the designed aluminum alloy conductor, select aluminum ingots with a purity of ≥99.9%, and use Al-Fe master alloy, Al-Ni master alloy, and Al-Me master alloy as the corresponding alloying elements for batching.

[0072] S3: Heat the aluminum ingot to 750℃ in a resistance furnace and melt it. Then, add the Al-Fe master alloy, Al-Ni master alloy, and Al-Me master alloy in sequence and melt them.

[0073] S4: After all the alloys are added, ultrasonic stirring is required. Place the aluminum alloy melt with an ultrasonic generator at 2 / 3 depth of the aluminum alloy melt for ultrasonic stirring for 15 minutes.

[0074] S5: Prepare hexachloroethane powder at 3 wt% of the total melt weight, wrap it in aluminum foil, and press it into the bottom of the molten aluminum alloy using a graphite bell jar to vent and slag. After the venting reaction is complete, slowly remove the bell jar and skim off the slag generated on the surface of the molten aluminum alloy. After skimming, close the furnace door and allow the molten aluminum alloy to stand for 20 minutes. Adjust the furnace temperature to 720℃ and wait for the melt to reach the desired temperature. After standing, open the furnace lid and remove any remaining slag from the surface. The molten aluminum alloy can then be cast. After casting, allow the aluminum alloy ingot to cool naturally.

[0075] S6: Remove the surface oxide layer of the aluminum alloy ingot by turning, perform heat treatment on the ingot, hold the ingot at 500℃ for 6 hours, and then heat it to 530℃ in the furnace and hold it for 6 hours.

[0076] S7: Hot extrusion plastic deformation of the ingot. After preheating the ingot at 410℃ for 1.5 hours, hot extrusion is performed to form a round rod with a diameter of 10mm, ensuring an extrusion ratio of ≥30, followed by air cooling.

[0077] S8: The extruded aluminum alloy rod is subjected to a first cryogenic treatment by immersing it in a container filled with liquid nitrogen from room temperature and keeping it at a temperature of -196°C for 2 hours. Then, it is gradually heated to room temperature along with the container at a rate of 1 hour, and the aluminum alloy rod is then removed.

[0078] S9: The extruded and cryogenically treated aluminum alloy round rod is subjected to multiple continuous drawing at room temperature. The deformation of each drawing is controlled at 30%. After multiple drawing processes, the plastically deformed aluminum alloy wire material with a diameter of about 3mm is obtained, and the total deformation exceeds 80%.

[0079] S10: The drawn aluminum alloy wire undergoes a second cryogenic treatment. After all the drawing processes in S9, the aluminum alloy wire is moved from room temperature into a container filled with liquid nitrogen and kept at a temperature of -196°C for 2 hours. Then, the temperature is gradually increased along with the container, and the temperature is increased to room temperature over 1 hour. The aluminum alloy wire is then removed.

[0080] S11: The aluminum alloy wire treated with liquid nitrogen undergoes continuous heat treatment. The wire enters from one end of a tubular furnace at 480°C through an unwinding mechanism, and then exits from the other end through a winding mechanism. The dwell time of the wire in the tubular furnace is controlled to be 60 seconds. After the wire is heated in the tubular furnace, it is sprayed with room temperature water mist for water cooling. After cooling, the aluminum alloy wire is obtained.

[0081] Example 3

[0082] S1: Design a heat-resistant and creep-resistant aluminum alloy conductor alloy composition, including the following alloying elements by mass percentage: Fe content 0.5%, Ni content 0.5%, with Fe and Ni added in a 1:1 ratio, Me added in the alloy in the following proportions: 50wt%Ce, 25wt%La, 15wt%Nd, 5wt%Sc, 5wt%Zr, with a total impurity content of less than 0.1%, and the balance being aluminum.

[0083] S2: Based on the composition and mass percentage of the designed aluminum alloy conductor, select aluminum ingots with a purity of ≥99.9%, and use Al-Fe master alloy, Al-Ni master alloy, and Al-Me master alloy as the corresponding alloying elements for batching.

[0084] S3: Heat the aluminum ingot to 740℃ in a resistance furnace to melt it, and then add the Al-Fe master alloy, Al-Ni master alloy and Al-Me master alloy in sequence to melt it.

[0085] S4: After all the alloys are added, ultrasonic stirring is required. Place the aluminum alloy melt with an ultrasonic generator at 2 / 3 depth of the aluminum alloy melt for ultrasonic stirring for 15 minutes.

[0086] S5: Prepare hexachloroethane powder at 2 wt% of the total melt weight, wrap it in aluminum foil, and press it into the bottom of the molten aluminum alloy using a graphite bell jar to vent and slag. After the venting reaction is complete, slowly remove the bell jar and skim off the slag generated on the surface of the molten aluminum alloy. After skimming, close the furnace door and allow the molten aluminum alloy to settle, generally for 15 minutes. Adjust the furnace temperature to 710℃ and wait for the melt to reach the set temperature. After settling, open the furnace lid and remove any remaining slag from the surface. The molten aluminum alloy can then be cast. After casting, allow the aluminum alloy ingot to cool naturally.

[0087] S6: Remove the surface oxide layer of the aluminum alloy ingot by turning, perform heat treatment on the ingot, hold the ingot at 490℃ for 6 hours, and then heat it to 525℃ in the furnace and hold it for 6 hours.

[0088] S7: Hot extrusion plastic deformation of the ingot. After preheating the ingot at 400℃ for 1.5 hours, hot extrusion is performed to form a round rod with a diameter of 8mm, ensuring an extrusion ratio of ≥30, followed by air cooling.

[0089] S8: The extruded aluminum alloy rod is subjected to a first cryogenic treatment by immersing it in a container filled with liquid nitrogen from room temperature and keeping it at a temperature of -196°C for 1 hour. Then, the rod is gradually heated to room temperature along with the container at a rate of 0.75 hours before being removed.

[0090] S9: The extruded and cryogenically treated aluminum alloy round rod is subjected to multiple continuous drawing passes at room temperature. The deformation of each drawing pass is controlled at 25%. The drawn aluminum alloy wire is subjected to a second cryogenic treatment using an online liquid nitrogen cryogenic treatment method. That is, after each wire is drawn out of the die hole, it is directly immersed in the liquid nitrogen container for 30 seconds in the winding mechanism, and then quickly returned to room temperature for the next drawing pass. This cycle is repeated. After multiple drawing passes, a plastically deformed aluminum alloy wire with a diameter of about 2mm and a total deformation of more than 80% is obtained. After the last online cryogenic treatment, the temperature is gradually increased along with the container and brought back to room temperature over 1 hour. The aluminum alloy wire is then taken out.

[0091] S10: The aluminum alloy wire is subjected to continuous heat treatment. The wire enters from one end of a tubular furnace at a temperature of 500°C through an unwinding mechanism, and then exits from the other end of the tubular furnace through a winding mechanism. The dwell time of the wire in the tubular furnace is controlled to be 45 seconds. After the wire is heated in the tubular furnace, it is cooled by blowing cold air. After cooling, the aluminum alloy wire is obtained.

[0092] Comparative Example 1

[0093] The only difference between this comparative example and Example 3 is that Sc and Zr are not added. All other steps and conditions are the same, and an aluminum alloy wire is obtained. The performance of the obtained aluminum alloy wire is shown in Table 1.

[0094] Comparative Example 2

[0095] The only difference between this comparative example and Example 3 is that Me is not added, only Fe and Ni are added. All other steps and conditions are the same, and aluminum alloy wires are obtained. The performance of the obtained aluminum alloy wires is shown in Table 1.

[0096] Comparative Example 3

[0097] The only difference between this comparative example and Example 3 is that continuous heat treatment is not performed after the second cryogenic treatment. All other steps and conditions are the same, and aluminum alloy wires are obtained. The properties of the obtained aluminum alloy wires are shown in Table 1.

[0098] Comparative Example 4

[0099] The only difference between this comparative example and Example 3 is that the Fe content is changed to 0.5%, the Ni content is 0%, and the ratio of Fe to Ni is not 1:1. All other steps and conditions are the same, and an aluminum alloy wire is obtained.

[0100] Comparative Example 5

[0101] The only difference between this comparative example and Example 3 is that all the cryogenic treatment steps are removed, while other processing and heat treatment steps and conditions remain unchanged, resulting in aluminum alloy wires.

[0102] Figures 1-3 The figures show the microstructure of the precipitated phase distribution in the aluminum alloy wires obtained in Examples 1-3 of this invention. As can be seen from the figures, the number of precipitated phases is relatively small in Example 1, while it is relatively large in Example 2. In Example 3, the number of precipitated phases is large and evenly distributed, and the precipitated phase distribution is more diffuse than that in Example 2 at the same magnification.

[0103] Figure 4 In Embodiment 1 of the present invention, after multiple plastic deformations, a large number of microstructures such as vacancies, dislocations, subgrain boundaries, and grain boundaries are generated in the aluminum matrix. These structures can improve its stability during subsequent cryogenic treatment.

[0104] Figure 5In Embodiment 1 of the present invention, after a second cryogenic treatment and then continuous heat treatment, the aluminum matrix grains are rapidly transformed into small, uniform, and dispersed grains. This grain morphology is beneficial to improving the conductivity of the aluminum matrix.

[0105] from Figure 6 The Al3(Sc,Zr) precipitate formed after the addition of Sc and Zr can be seen. This phase is coherent with the aluminum matrix (it exhibits a bean-shaped morphology in the microstructure, which proves that the Al3(Sc,Zr) precipitate is coherent with the aluminum matrix). Therefore, it has a good strengthening effect and does not cause large distortion of the aluminum matrix lattice, which is beneficial to improving conductivity.

[0106] Figure 7 The addition of rare earth elements Ce, La, and Nd results in the precipitation of nanoscale Al in the aluminum alloy wires of this invention. 11 Ce3 precipitates, nano-sized Al 11 La3 precipitates, nano-sized Al 11 The Nd3 precipitates exhibit rod-shaped and dot-shaped morphologies (indicated by arrows), with sizes ranging from tens of nanometers.

[0107] Figure 8 It can be seen that the fragmented Al9(Fe,Ni) dispersed phase is uniformly distributed on the grain boundaries, which effectively improves high-temperature stability and grain boundary creep resistance.

[0108] Table 1 shows the comprehensive performance of the aluminum alloy conductors in Examples 1-3 and Comparative Examples 1-5.

[0109] Examples 1-3 describe the tensile strength, elongation after fracture, electrical conductivity, and steady-state creep rate of the aluminum alloy wires obtained. It can be seen that the different amounts of added elements in the examples resulted in varying precipitate content, leading to different properties. Generally, increased precipitate content increases strength but decreases electrical conductivity. Since the solubility of a certain phase in the matrix alloy at room temperature is constant, increasing the element content leads to an increase in the content of the precipitated second phase. Increased precipitate content improves material strength and hinders dislocation movement. However, it also increases electron scattering during transport, reducing electrical conductivity. In Example 3 of this invention, the tensile strength of the material was significantly increased while only slightly reducing electrical conductivity and elongation.

[0110] The comparison sample has obvious defects in various performance aspects, and its overall performance cannot meet the requirements for use with aluminum alloy wires.

[0111] Table 1 Performance of Aluminum Alloy Conductors in Examples and Comparative Examples

[0112]

[0113] Note: The steady-state creep rate test conditions in Table 1 are 70 MPa and 150 °C; tensile strength, elongation after fracture, and electrical conductivity were all obtained at room temperature.

Claims

1. A heat-resistant and creep-resistant aluminum alloy conductor, characterized in that: The composition by mass percentage is as follows: Fe 0.25~0.75%, Ni 0.25~0.75%, Me 0.2~1%, with the balance being aluminum and unavoidable impurities; The composition of Me by mass percentage is as follows: La 20~25%, Nd 10~15%, Sc 3~5%, Zr 3~5%, with the balance being Ce; The ratio of Fe to Ni is 1:(1~1.05), and the ratio of Sc to Zr is 1:(1~1.05). The aluminum alloy wire contains nanoscale Al 11 Ce3 precipitates, nanoscale Al 11 La3 precipitates, nanoscale Al 11 Nd3 precipitates, nanoscale Al3(Sc,Zr) precipitates, and micrometer-scale Al9(Fe,Ni) dispersoids; and the nanoscale Al3(Sc,Zr) precipitates are coherent with the aluminum matrix.

2. The heat-resistant and creep-resistant aluminum alloy conductor according to claim 1, characterized in that: The composition by mass percentage is as follows: Fe 0.5~0.6%, Ni 0.5~0.6%, Me 0.6~1%, with the balance being aluminum and unavoidable impurities.

3. The heat-resistant and creep-resistant aluminum alloy wire according to claim 1 or 2, characterized in that: The micron-sized Al9(Fe,Ni) dispersed phase is distributed on the grain boundaries of the aluminum alloy matrix.

4. A method for preparing a heat-resistant and creep-resistant aluminum alloy conductor as described in any one of claims 1 to 3, characterized in that: Includes the following steps: S1 Weigh each component raw material according to the designed aluminum alloy wire assembly ratio and melt it. After all the raw materials have melted, add refining agent to refine and degas the material to obtain aluminum alloy melt. S2 adjusts the temperature of the aluminum alloy melt to 700~720℃ and then casts it to obtain an aluminum alloy ingot. S3 The aluminum alloy ingot is subjected to heat treatment, hot extrusion plastic deformation with an extrusion ratio ≥30 and first deep cryogenic treatment in sequence to obtain an aluminum alloy round rod; The aluminum alloy round rod described in S4 is subjected to multiple continuous drawing processes at room temperature. The resulting wire undergoes a second cryogenic treatment and continuous heat treatment. After cooling, the aluminum alloy wire is obtained.

5. The method for preparing a heat-resistant and creep-resistant aluminum alloy conductor according to claim 4, characterized in that: The raw materials used are aluminum ingots with a purity of ≥99.9%, Al-Fe master alloy, Al-Ni master alloy and Al-Me master alloy. During the melting process, the aluminum ingots are first heated to 730~750℃ to melt, and then Al-Fe master alloy, Al-Ni master alloy and Al-Me master alloy are added in sequence to melt.

6. The method for preparing a heat-resistant and creep-resistant aluminum alloy conductor according to claim 4, characterized in that: The heat treatment process involves first holding the temperature at 480~500℃ for 4~6 hours, and then raising the temperature to 520~530℃ and holding it for 4~6 hours.

7. A method for preparing a heat-resistant and creep-resistant aluminum alloy conductor according to claim 5 or 6, characterized in that: The temperature for hot extrusion plastic deformation is 400~420℃, and the preheating time is 1~1.5h; The diameter of the aluminum alloy round rod is 6~10mm.

8. The method for preparing a heat-resistant and creep-resistant aluminum alloy conductor according to claim 7, characterized in that: The temperature of the first cryogenic treatment is less than or equal to -196°C, and the time is 0.5 to 2 hours. After the first cryogenic treatment is completed, the temperature is raised to room temperature.

9. The method for preparing a heat-resistant and creep-resistant aluminum alloy conductor according to claim 4, characterized in that: The deformation amount of each pass in the multi-pass continuous drawing is 20-30%, and the total deformation amount exceeds 80%; the temperature of the second cryogenic treatment is less than or equal to -196℃, the time is 0.5-2h, and the temperature is raised to room temperature after the second cryogenic treatment is completed. The temperature of the continuous heat treatment tube furnace is controlled at 475℃~500℃, and the residence time in the tube furnace is 15~60s; The cooling method is either air cooling or water cooling.

10. The method for preparing a heat-resistant and creep-resistant aluminum alloy conductor according to claim 9, characterized in that: During the multi-pass continuous drawing process, deep cryogenic treatment is performed between passes.

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