A compositionally graded aluminum matrix composite wire and a method of making the same

Abstract

The present application relates to a kind of component gradient aluminum matrix composite wire and its preparation method, belong to high-performance wire technical field under alternating current environment, by powder metallurgy process, the aluminum alloy wire of component gradient change is quickly prepared, the outermost layer is Al2O3 Particle reinforced pure aluminum, and the electrical conductivity is excellent, the inner layer is carbon nanotube reinforced aluminum alloy, and provide mechanical properties for wire, under alternating current use environment, and the comprehensive performance is excellent, and product production process is simple, and quality is stable, can be used for industrial production.

Description

Technical Field

[0001] This invention relates to the field of high-performance conductor technology under alternating current conditions, specifically to a composition-gradient aluminum-based composite conductor and its preparation method. Background Technology

[0002] Aluminum and aluminum alloys are considered excellent conductors due to their advantages such as low density, high specific strength, high conductivity, and high economy, and are widely used in many fields.

[0003] Currently, high-strength aluminum alloy conductors are the most widely used type of aluminum alloy conductor. By adding elements such as magnesium and silicon to aluminum, and after processing, deformation, and heat treatment, sufficient strength, plasticity, and conductivity are obtained. Its strength is nearly twice that of ordinary aluminum conductors, with a single wire strength of over 300 MPa. However, its conductivity is relatively low, only ~53% IACS (International Annealed Copper Standard), resulting in high line losses, which restricts the further development of high-strength aluminum alloy conductors.

[0004] In metallic materials, there is a contradictory relationship between mechanical properties and electrical conductivity; that is, an increase in material strength usually leads to a decrease in electrical conductivity, and an increase in electrical conductivity leads to a decrease in strength. Simultaneously improving both the strength and electrical conductivity of a material is difficult.

[0005] In actual use, alternating current exhibits the "skin effect," meaning that the current distribution inside a conductor is uneven, with the current concentrated in a thin layer on the conductor's surface. The closer to the conductor's surface, the greater the current density, while the current inside the conductor is actually smaller, contributing less to the conductor's conductivity.

[0006] To address the aforementioned issues, existing technologies have developed wires with a compositional gradient, consisting of a pure aluminum exterior and an alloy interior. These wires are prepared using a casting method to produce cylindrical pure aluminum ingots and cylindrical aluminum alloy ingots. Then, machining equipment is used to remove the metal oxide scale from the surface of the cylindrical aluminum alloy ingot and the inner surface of the cylindrical pure aluminum ingot. The cylindrical pure aluminum ingot is then fitted over the alloy exterior, and the two are bonded together through a hot extrusion process. However, this method is cumbersome and results in poor bonding quality between the different components, making it difficult to meet engineering application standards. Summary of the Invention

[0007] In view of the above problems, the present invention provides a composition-gradient aluminum-based composite conductor and its preparation method, which is used to prepare composition-gradient aluminum-based composite conductors for AC power. Through powder metallurgy preparation process, high-performance composition-gradient aluminum alloy conductors can be quickly prepared, which solves the contradiction between the mechanical properties and conductivity of aluminum alloy conductors in the AC power environment in the prior art. Its comprehensive performance is excellent, the quality is stable, and the preparation process is simple and can be used for industrial production.

[0008] This invention provides a composition-gradient aluminum-based composite conductor and its preparation method, comprising:

[0009] Step 1: Prepare pure aluminum powder and aluminum alloy powder respectively, and pretreat the pure aluminum powder and aluminum alloy powder to obtain pure aluminum pre-oxidized powder and aluminum alloy pre-treated powder.

[0010] Preferably, the specific steps for obtaining pure aluminum pre-oxidized powder and aluminum alloy pre-treated powder include:

[0011] Pure aluminum powder was prepared using a gas atomization method; the pure aluminum powder had a particle size of 1–3 μm and a purity higher than 99.7%.

[0012] Pure aluminum powder is placed in a mixing tank and heated and stirred to fully oxidize the surface of the pure aluminum powder, thereby obtaining pure aluminum pretreated powder.

[0013] Aluminum alloy powder was prepared by gas atomization; the aluminum alloy powder and carbon nanotubes were ball-milled and mixed evenly to obtain pretreated aluminum alloy powder.

[0014] Furthermore, the mixing tank has a high-purity oxygen environment, the heating temperature is 200-300℃, the stirring speed is 50-100 r / min, and the stirring time is 2-4 h;

[0015] The carbon nanotubes have a length of 5–15 μm and a diameter of 40–60 nm, and the carbon nanotube content in the aluminum alloy pretreated powder is 0.3%–2%.

[0016] The ball mill used is a planetary ball mill. The ball-to-material ratio in the ball milling process is 5:1 to 10:1. 1 to 3 mm stainless steel balls are used. The rotation speed is 300 to 400 rpm and the ball milling time is 5 to 8 hours.

[0017] The technical solution of this invention generates nano-oxide particles in situ in pure aluminum. The nano-oxide particles not only improve the strength of pure aluminum, but also do not damage the conductivity of the matrix. Adding carbon nanotubes to the alloy can significantly improve the strength of the matrix. This invention designs two reinforcing phases to reinforce the inner and outer matrices respectively, thereby improving the overall strength while maintaining the conductivity of the wire under alternating current.

[0018] The pure aluminum oxide powder prepared by the technical solution of the present invention has a near-spherical shape. The powder surface is fully oxidized and covered with an amorphous Al2O3 film. During the subsequent sintering process, it is transformed into an Al2O3 particle reinforcement phase. The nano-Al2O3 particle reinforcement phase is introduced into the outer layer of pure Al. Its small size and directional distribution in the pure aluminum matrix increase the strength of pure aluminum on the one hand, and do not damage the conductivity of pure aluminum on the other hand, thereby improving the overall strength of the wire.

[0019] Step 2: The aluminum alloy pretreated powder and pure aluminum pre-oxidized powder described in Step 1 are subjected to a powder spreading process to obtain a composition gradient mixed powder;

[0020] The composition gradient mixed powder is sintered by setting the sintering temperature and time to obtain a composition gradient sintered blank.

[0021] Preferably, the specific steps for obtaining the composition gradient sintered blank in step two include:

[0022] Aluminum alloy pre-treated powder is cold-pressed to obtain cold-pressed blanks;

[0023] The cold-pressed blank and the pure aluminum pre-oxidized powder are placed into a hot isostatic pressing sleeve for powder spreading process to obtain the processed sleeve.

[0024] The processed casing is degassed at high temperature, a vacuum is set, and the casing is then sealed by welding.

[0025] The sealed sleeve is placed in a hot isostatic pressing furnace, and the sintering temperature and time are set for sintering.

[0026] After sintering, the furnace is cooled to the furnace opening temperature, and the sealed sleeve is removed from inside the furnace.

[0027] After removing the sealing sleeve, sintered blank material is obtained.

[0028] Furthermore, the pressure of the cold pressing treatment is 200-300 MPa, and the holding time is 10-20 min;

[0029] Furthermore, the degassing temperature is 200–300°C, and the vacuum degree is 0–10. -2 Pa;

[0030] Furthermore, the sintering temperature is 500-600℃, the sintering time is 6-8h, and the furnace opening temperature is 0-100℃.

[0031] The material prepared by the technical solution of this invention contains two metal components and two reinforcing phases. During the hot isostatic pressing powder spreading process, the two powders mentioned in step one are distributed in a gradient in the sintered blank through the powder spreading process. The outer layer of the conductor is pure aluminum with good conductivity, which provides conductivity. The inner layer of the conductor is aluminum alloy with high strength, which mainly provides strength. When the conductor is used in an alternating current environment, both conductivity and strength are taken into account.

[0032] The sintered blank obtained by this invention has a gradient structure, with an outer layer of pure aluminum reinforced by Al2O3 and an inner layer of aluminum alloy reinforced by carbon nanotubes. During the sintering process, the sintering temperature is set at 500-600℃ and the sintering time is 6-8h. Through the metal powder design in step one and the powder spreading process in step two, a composite material with gradient metal composition and gradient reinforcing phase composition is produced by hot isostatic pressing. It is a material with good interfacial bonding between the reinforcing phase and the metal, and the overall performance of the material is excellent. Under alternating current environment, it balances the strength and conductivity of the material, and solves the contradictory relationship between the strength and conductivity of the material.

[0033] Step 3: The composition gradient sintered blank is plastically deformed and heat-treated to prepare composition gradient aluminum-based composite wires.

[0034] Preferably, the plastic deformation includes: hot extrusion and cold drawing;

[0035] The specific steps for preparing the composition gradient aluminum-based composite conductor are as follows:

[0036] The composition gradient sintered billet is extruded into bars through a hot extrusion process; the hot extrusion processing temperature is 400-450℃.

[0037] Aluminum alloy wires are obtained by solution heat treatment of the rod and then cold drawing. The aluminum alloy wires are then subjected to aging heat treatment to obtain aluminum-based composite wires with different metal compositions and different types of reinforcing phases.

[0038] Preferably, the outer layer of the composition-gradient aluminum-based composite conductor is Al2O3-reinforced pure aluminum, and the inner layer is carbon nanotube-reinforced aluminum alloy; the diameter of the inner aluminum alloy layer accounts for 40% to 90% of the conductor diameter. The composition-gradient aluminum-based composite conductor prepared by this invention has a compositional gradient from the conductor core to the surface, with an outer layer of Al2O3-reinforced pure aluminum and an inner layer of carbon nanotube-reinforced aluminum alloy. The conductor strength is ≥350 MPa, the conductivity of the outer pure aluminum portion is ≥58% IACS, and the overall conductivity is ≥55% IACS.

[0039] This invention uses powder metallurgy to prepare raw materials, followed by plastic deformation and corresponding heat treatment processes, to quickly produce aluminum-based composite conductors with varying composition. When used in an alternating current environment, the outer part of the conductor bears more of the conductive function. Its outer component is pure aluminum with excellent conductivity, while the inner part is a high-strength, low-conductivity aluminum alloy that mainly bears the load. By combining high-conductivity, low-strength pure aluminum with high-strength, low-conductivity alloy, a conductor with excellent comprehensive performance is produced, reducing resistance while maintaining the strength advantages of high-strength aluminum conductors.

[0040] The preparation process of this invention overcomes the interface problems between metals of different compositions and the interface bonding between the reinforcing phase and the matrix, and solves the problem of uniform directional distribution of materials of different compositions in composite materials.

[0041] The preparation process of this invention is simple, and the prepared material has good bonding between the metals of different components and the reinforcing phase and the matrix. Moreover, the metals of different components are uniformly and oriented in the composite material. The types of alloying elements and their gradient state in the aluminum alloy wires can be adjusted and controlled, and it can be used for large-scale mechanized production.

[0042] The aluminum-based composite conductor with compositional gradient prepared by this invention, when used in an alternating current environment, effectively controls the internal composition and structure of the conductor. The material has good electrical conductivity on the conductor surface and provides mechanical properties inside the conductor, breaking the constraint relationship between strength and conductivity, and producing an aluminum conductor with excellent comprehensive performance.

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] (1) This invention uses powder metallurgy to directly prepare aluminum alloy sintered billets with composition gradients. The process is simple and the product quality is stable.

[0045] (2) The aluminum alloy wire prepared by the present invention has an outermost layer of pure aluminum reinforced with Al2O3 particles, which has excellent conductivity, and an inner layer of aluminum alloy reinforced with carbon nanotubes, which provides mechanical properties for the wire. Under AC power conditions, the overall performance is excellent.

[0046] (3) The preparation method of the present invention allows for the selection of alloy components according to actual usage requirements, making the performance of aluminum wires adjustable and controllable. Attached Figure Description

[0047] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0048] Figure 1 This is a schematic diagram of the conductor structure and skin effect in an alternating current environment according to the present invention. Detailed Implementation

[0049] To better understand the above-described objectives, features, and advantages of the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other. Furthermore, the present invention can be implemented in other ways different from those described herein; therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0050] A specific embodiment of the present invention, such as Figure 1This invention discloses a composition-gradient aluminum-based composite conductor and its preparation method. To illustrate the effectiveness of the method proposed in this invention, a specific embodiment is provided below for detailed explanation of the above technical solution. The specific implementation steps are as follows:

[0051] Example 1:

[0052] Step 1: Powder preparation and pretreatment

[0053] Pure aluminum powder was prepared using a gas atomization method, with a particle size of 1–3 μm and a purity of 99.7%. The pure aluminum powder was then placed in a stainless steel electrically heated stirring tank and stirred at 200°C in a high-purity oxygen atmosphere to ensure complete oxidation of the powder surface.

[0054] The stirring speed was 50 r / min and the stirring time was 4 h to obtain pure aluminum pre-oxidized powder;

[0055] 6201 aluminum alloy powder with a particle size of 5-10 μm was prepared by gas atomization; then the alloy powder was mixed with carbon nanotubes by ball milling to prepare composite powder.

[0056] The carbon nanotubes are 5-10 μm in length and 40-50 nm in diameter. The equipment used is a planetary ball mill. The mass fraction of carbon nanotubes is 0.3% of the aluminum alloy powder. The ball milling process is a ball-to-material ratio of 10:1, using 3 mm stainless steel balls, a rotation speed of 300 rpm, and a time of 6 hours.

[0057] Step 2: Preparation of sintered raw material

[0058] First, the alloy powder prepared in the first step is placed into a cylindrical mold and cold-pressed. The diameter of the cold-pressed blank is 50% of the inner diameter of the hot isostatic pressing sleeve. The cold pressing parameters are: pressure 200MPa, holding time 20min.

[0059] Then, the cold-pressed blank is placed in the middle of the hot isostatic pressing sleeve, and the pure aluminum pre-oxidized powder prepared in the first step is placed in the gap between the sleeve and the cold-pressed blank; after the powder filling is completed, the sleeve is degassed at a high temperature of 200℃, and the vacuum degree inside the sleeve is less than 10. -2 When Pa is applied, the sleeve is sealed by welding.

[0060] The shroud is then placed in a hot isostatic pressing furnace for sintering at a temperature of 500°C for 6 hours. After sintering, the shroud is cooled to below 100°C in the furnace and then removed.

[0061] The outer casing was then removed to obtain the sintered raw material.

[0062] Step 3: Hot extrusion, cold drawing, and heat treatment

[0063] The sintered billet is extruded into rods through a hot extrusion process at a temperature of 450℃. The rods are then subjected to solution heat treatment at 500℃ for 4 hours, followed by cold drawing to prepare aluminum alloy wires. Subsequently, the wires are subjected to aging heat treatment at 170℃ for 8 hours. The wires prepared in this third step are characterized by a compositional gradient material from the core to the surface. The overall strength of the wire is 350MPa, the conductivity of the outer pure aluminum layer is ≥58% IACS, and the overall conductivity is 57% IACS.

[0064] Compared to 6201 aluminum alloy conductors prepared by traditional methods, the strength is increased from 260MPa to 350MPa, a 35% improvement; the overall conductivity is increased from 54% IACS to 57% IACS. Since the outer pure aluminum layer has a conductivity ≥58% IACS, the conductivity is even higher under AC power conditions.

[0065] Example 2:

[0066] Step 1: Preparation and pre-oxidation of pure aluminum powder

[0067] Pure aluminum powder with a particle size of 1–3 μm and a purity of 99.9% was prepared using a gas atomization method. The pure aluminum powder was then placed in a stainless steel electrically heated stirring vessel and stirred at 200°C in a high-purity oxygen atmosphere to ensure complete surface oxidation. The stirring speed was 50 r / min, and the stirring time was 4 h, yielding pre-oxidized pure aluminum powder.

[0068] 6201 aluminum alloy powder with a particle size of 5–10 μm was prepared by gas atomization. Then, the alloy powder was mixed with carbon nanotubes by ball milling to prepare a composite powder. The carbon nanotubes had a length of 5–10 μm and a diameter of 40–50 nm. A planetary ball mill was used, with the carbon nanotubes accounting for 0.3% of the aluminum alloy powder by mass. The ball milling process used a ball-to-powder ratio of 10:1, 3 mm stainless steel balls, a rotation speed of 300 rpm, and a time of 6 hours.

[0069] Step 2: Preparation of sintered raw material

[0070] Sintered blanks were prepared using a hot isostatic pressing (HIP) process. First, the alloy powder prepared in the first step was placed in a cylindrical mold and cold-pressed, with the diameter of the cold-pressed blank occupying 80% of the inner diameter of the HIP sleeve. The cold-pressing parameters were a pressure of 200 MPa and a holding time of 20 min. Then, the cold-pressed blank was placed in the middle of the HIP sleeve, and the pure aluminum pre-oxidized powder prepared in the first step was placed in the gap between the sleeve and the cold-pressed blank. After powder filling, the sleeve was degassed at a high temperature of 200℃, with the vacuum degree inside the sleeve being less than 10... -2At Pa, the cladding is sealed by welding. Then, the cladding is placed in a hot isostatic pressing furnace for sintering at 500℃ for 6 hours. After sintering, it is cooled to below 100℃ in the furnace, and the cladding is removed. The cladding is then machined off to obtain the sintered blank.

[0071] Step 3: Hot extrusion, cold drawing, and heat treatment

[0072] The sintered billet is extruded into rods using a hot extrusion process at 450℃. The rods are then subjected to solution heat treatment at 500℃ for 4 hours, followed by cold drawing to produce a conductor. This is followed by aging heat treatment at 170℃ for 8 hours. The conductor prepared in this third step is characterized by a compositional gradient from the core to the surface. The overall strength of the conductor is 400 MPa, and the conductivity of the outer pure aluminum layer is ≥59% IACS, with an overall conductivity of 55% IACS. Compared to 6201 aluminum alloy conductors prepared using traditional methods, the strength is increased from 260 MPa to 400 MPa, a 54% improvement; the overall conductivity is increased from 54% IACS to 55% IACS. Because the outer pure aluminum layer has a conductivity of ≥59% IACS, the conductivity is even higher under AC power conditions.

[0073] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a composition-gradient aluminum-based composite conductor, characterized in that, include: Step 1: Prepare pure aluminum powder and aluminum alloy powder respectively, and pretreat the pure aluminum powder and aluminum alloy powder to obtain pure aluminum pre-oxidized powder and aluminum alloy pre-treated powder. Step 2: The aluminum alloy pretreated powder and pure aluminum pre-oxidized powder described in Step 1 are subjected to a powder spreading process to obtain a composition gradient mixed powder; The composition gradient mixed powder is sintered by setting the sintering temperature and time to obtain a composition gradient sintered billet. Step 3: The composition gradient sintered billet is subjected to plastic treatment to prepare composition gradient aluminum-based composite wires; The carbon nanotube content in the aluminum alloy pretreated powder is 0.3%~2%; The specific steps for obtaining the composition gradient sintered billet include: Aluminum alloy pre-treated powder is cold-pressed to obtain cold-pressed billets; The cold-pressed billet and the pure aluminum pre-oxidized powder are placed into a hot isostatic pressing sleeve for powder spreading process to obtain the processed sleeve. The processed casing is degassed at high temperature, a vacuum is set, and the casing is then sealed by welding. The sealed sleeve is placed in a hot isostatic pressing furnace, and the sintering temperature and time are set for sintering. After sintering, the furnace is cooled to the furnace opening temperature, and the sealed sleeve is removed from inside the furnace. Remove the sealing sleeve to obtain the sintered billet; The powder spreading process specifically includes: The aluminum alloy pre-treated powder is cold-pressed to form a billet, which is then placed in the middle of a hot isostatic pressing (HIP) sleeve. The height of the cold-pressed billet is equal to the height of the HIP sleeve, and the diameter of the cold-pressed billet accounts for 50-80% of the inner diameter of the sleeve. Pure aluminum pre-oxidized powder is then laid into the remaining gaps in the HIP sleeve. The composition gradient aluminum-based composite conductor has an outer layer of reinforced pure aluminum and an inner layer of carbon nanotube-reinforced aluminum alloy. The ratio of the diameter of the inner layer of the composition gradient aluminum composite conductor to the diameter of the composition gradient aluminum composite conductor is 0.4-0.9:

1.

2. The preparation method according to claim 1, characterized in that, The specific steps for obtaining the pure aluminum pre-oxidized powder and the aluminum alloy pre-treated powder include: Pure aluminum powder and aluminum alloy powder were prepared using a gas atomization method; Pure aluminum powder is placed in a mixing tank and heated and stirred to obtain pure aluminum pre-oxidized powder. Aluminum alloy powder and carbon nanotubes were ball-milled to obtain pretreated aluminum alloy powder.

3. The preparation method according to claim 2, characterized in that, The pure aluminum powder has a particle size of 1~3μm and a purity higher than 99.7%.

4. The preparation method according to claim 1, characterized in that, The sintering temperature is 500~600℃, and the sintering time is 6~8h.

5. The preparation method according to claim 1, characterized in that, The specific steps for preparing the composition gradient aluminum-based composite conductor are as follows: The composition gradient sintered billet is extruded into bars through a hot extrusion process; Aluminum alloy wires are obtained by solution heat treatment of the rod and then cold drawing. The aluminum alloy wires are then subjected to aging heat treatment to obtain aluminum-based composite wires with different metal compositions and different types of reinforcing phases.

6. A composition-gradient aluminum-based composite conductor, characterized in that, The composition gradient aluminum-based composite conductor is prepared by any one of the preparation methods described in claims 1-5.

Images