A manufacturing method of high-conductivity copper-clad aluminum flat wire

Abstract

The present invention discloses a manufacturing method of high-conductivity copper-clad aluminum flat wire, which relates to the technical field of electrical metal flat wire. First, the present invention uses the femtosecond laser surface modification technology for metal aluminum to generate a super-clean amorphous layer through non-thermal melting-solidification, greatly reducing the diffusion activation energy of subsequent cold pressure welding. Secondly, a micro-nano porous structure is induced on the aluminum surface during femtosecond laser treatment, and then a copper layer is deposited on the aluminum surface with nano-copper particles by gas deposition. The micron pits of the metal aluminum and the pores infiltrated by the nano-copper gas deposition form a "barb" structure to achieve atomic-level interdiffusion of copper and aluminum. Finally, a strong transverse magnetic field is applied during the cold pressure welding process to induce the preferred orientation of copper grains along the crystal plane; then, the copper-clad aluminum flat wire is prepared through cold pressing treatment. Dense forming and surface polishing can maximize the effective utilization of the conductive cross-section, avoid grain growth caused by high temperature, retain the fine-grained structure, and improve the material strength. The copper-clad aluminum flat wire prepared by the present invention has the effects of high strength and high conductivity.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive metal flat wires, and specifically to a manufacturing method for high-conductivity copper-clad aluminum flat wires. Background Art

[0002] In the field of electrical equipment manufacturing, traditional copper wires are widely used due to their excellent electrical conductivity. However, with the continuous improvement of material performance requirements and cost control needs, the limitations of traditional copper wires are gradually emerging. Copper-clad aluminum flat wires, as a new type of composite material, have emerged. Their core advantages lie in low density, good electrical conductivity, and high mechanical strength. In terms of electrical conductivity, by optimizing the bonding process between the copper layer and the aluminum core, such as using argon arc welding to form a strong metallurgical bond, good electrical conductivity is ensured, and the resistivity can be controlled at a low level. In terms of mechanical strength, copper-clad aluminum flat wires not only have the flexibility of the aluminum core but also the high strength of the copper layer.

[0003] In the manufacturing process, from the early cladding welding to the current advanced processes such as continuous casting and rolling, the production of copper-clad aluminum flat wires has become more efficient and precise, capable of meeting the order requirements of different specifications and performance. These background factors have jointly promoted the continuous innovation and development of the manufacturing method for high-conductivity copper-clad aluminum flat wires, making it play an increasingly important role in the manufacturing of electrical equipment such as transformers and motors.

[0004] During the manufacturing process of high-conductivity copper-clad aluminum flat wires, in terms of electrical conductivity, since copper-clad aluminum flat wires are composite materials of a copper layer and an aluminum core, their electrical conductivity is affected by various factors such as the thickness of the copper layer, the bonding quality of the copper-aluminum interface, and the manufacturing process. If the copper layer is too thin, the electrical conductivity may decrease, while if the copper layer is too thick, the cost will increase. In addition, if there is an oxide layer or poor bonding at the copper-aluminum interface, it will also hinder the flow of electrons and reduce the electrical conductivity. During the high-temperature annealing process, although annealing can eliminate the internal stress generated by cold working and improve the ductility and electrical conductivity of the material, there are also some defects. High-temperature annealing may cause the formation of an intermetallic compound layer at the copper-aluminum interface. When the thickness of this layer exceeds a certain limit, the interface bonding strength will be significantly reduced, making the material prone to fracture during use. At the same time, high-temperature annealing may also cause the grain growth of the material, affecting the stability of its mechanical properties and electrical conductivity. Summary of the Invention

[0005] The purpose of the present invention is to provide a manufacturing method for high-conductivity copper-clad aluminum flat wires to solve the problems existing in the prior art.

[0006] To solve the above technical problems, the present invention provides the following technical solution: A preparation method for high-conductivity copper-clad aluminum flat wires, including the following preparation steps:

[0007] (1) Using a femtosecond laser, under argon protection, at 2 - 3 J / cm 2Irradiate the surface of a high-purity aluminum rod with a diameter of 3.0 - 5.0 mm with an energy density. Through electron instantaneous excitation and ultrafast cooling, the cooling rate is 10 12 -10 13 K / s, to generate a 50 - 100 nm thick ultra-clean amorphous layer on the surface of the high-purity aluminum rod. Subsequently, increase the energy density to 3 - 5 J / cm 2 , and adopt a spiral scanning path to form a porous structure intertwined with micron-sized pits with a diameter of 2 - 5 μm and edge nanowires with a diameter of 50 - 200 nm, thus obtaining a femtosecond laser pre-treated high-purity aluminum rod;

[0008] (2) First, pre-treat the high-purity aluminum rod with an argon plasma cleaning at 160 - 200 W for 3 - 5 min to remove subsurface impurities. Then, perform in-situ vacuum preheating on the cleaned high-purity aluminum rod. The vacuum degree is 0.5 MPa, the temperature is 150 °C, and the time is 1 h to remove water vapor. Deposit a 10 - 20 μm copper layer through PVD. Then, use a hot-wall ALD system equipped with a copper precursor transport module to deposit a copper layer by ALD. Adjust the copper / aluminum cycle ratio to achieve a composition gradient. Deposit at 150 - 250 °C with a copper / aluminum precursor pulse time of 0.1 - 1 s and a hydrogen pulse time of 0.5 - 2 s. Purge with high-purity argon for 10 - 20 s to form a 3 - 5 μm thick gradient transition layer, thus obtaining a gradient high-purity aluminum rod;

[0009] (3) Cold-bend a copper sheet and the gradient high-purity aluminum rod into a copper sleeve with an aluminum core in the middle through a set of hole-shaped rollers, and perform multi-pass drawing processing at a speed of 60 - 600 m / min and a pass reduction rate of 10 - 20% to prepare a round thin wire with a diameter of 0.3 - 3.0 mm. Apply a pressure of 80 - 120 MPa through a hydraulic press under a 1 - 2 T transverse magnetic field, and keep the pressure for 10 - 20 s. Prevent oxidation in a nitrogen atmosphere, and obtain a copper-clad aluminum wire through cold pressure welding. Finally, cold press with a four-roll precision rolling mill and then perform low-temperature annealing to obtain a high-conductivity copper-clad aluminum flat wire.

[0010] Further, the area ratio of the copper sheet coating layer in the cross-section of the copper-clad aluminum flat wire is 15% - 40%, the thickness is 0.02 - 0.05 mm, and the maximum width-to-thickness ratio of the flat wire is 10:1.

[0011] Further, in the step (1), the femtosecond laser has a wavelength of 1030 nm and a pulse width of 300 fs.

[0012] Further, in the step (1), the scanning speed of the spiral scanning is 500 mm / s, and the overlap rate is 15%.

[0013] Further, in step (2), for PVD deposition, argon gas is turned on with a flow rate of 20 sccm, the pressure is adjusted to 5 - 10 mTorr, copper is used as the target, and low - power sputtering is carried out at 50 W for 5 min, then the power is increased to 300 - 400 W to start deposition.

[0014] Further, in step (2), copper bis(hexafluoroacetylacetonate) (II) is used as the copper source, trimethylaluminum is used as the aluminum source, and hydrogen is used as the reducing agent.

[0015] Further, in step (2), during gradient deposition, in the initial stage, 100% copper cycle is carried out, and the proportion of aluminum cycle is gradually increased to 5 - 10%, while the proportion of copper cycle is decreased, keeping the total proportion of aluminum and copper at 100%.

[0016] Further, in step (2), the single - cycle thickness is 0.05 - 0.1 nm / cycle.

[0017] Further, in step (3), the thickness of the thick copper sheet is 0.1 - 0.16 mm.

[0018] Further, in step (3), the cold - pressing conditions are as follows: the surface of the rolling rolls is plated with hard chromium, the initial rolling pressure is 50 MPa and is gradually increased to 100 MPa; the width - thickness ratio is gradually pressed from 3:1 to 10:1, and the rolling speed is 100 - 300 m / min.

[0019] Further, in step (3), the annealing conditions are as follows: an Ar / H2 mixed gas is introduced into a tube - type annealing furnace with a flow rate of 10 - 20 L / min, where the volume ratio of Ar:H2 = 19:1, and it is kept at 80 - 120 °C for 30 - 60 min to release residual stress.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0021] The present invention uses femtosecond - laser pretreatment, gas - phase deposition line infiltration combined with cold - pressing magnetic field forming to prepare high - conductivity copper - clad aluminum flat wires, so as to achieve the effects of high strength and high conductivity.

[0022] Firstly, the pulse energy of the femtosecond laser is instantaneously absorbed by the free electrons on the surface layer of metallic aluminum for the surface modification technology of metallic aluminum. Through the non - linear interaction between the extremely short pulse and the material, non - thermal melting - solidification is carried out on the surface of metallic aluminum before cold - pressure welding, generating a super - clean amorphous layer without oxidation and grain boundaries, greatly reducing the diffusion activation energy of subsequent cold - pressure welding, realizing low - temperature and high - efficiency atomic bonding, that is, full diffusion can be achieved without annealing, thus avoiding the generation of brittle phases (such as CuAl2) caused by high - temperature annealing and reducing the ductility of the flat wire; at the same time, the femtosecond - laser pulse instantaneously vaporizes the surface - layer oxides, reducing the hindrance of oxides to atomic diffusion and enhancing the bonding strength at the copper - aluminum interface;

[0023] Secondly, when using femtosecond laser treatment, a micro-nano porous structure is induced on the aluminum surface. Subsequently, a copper layer is deposited on the aluminum surface by physical vapor deposition (PVD). The micron pits of metallic aluminum and the copper infiltrated into the pore lines by atomic layer deposition form a "barb" structure, generating three-dimensional mechanical interlocking. The micron pits serve as mechanical anchors, combined with the nano-network structure of the diffusion channels. Together with the ALD atomic layer deposition gradient layer, the gradient composition of aluminum-aluminum copper-copper acts on stress buffering, realizing atomic-level interdiffusion of copper and aluminum, avoiding the concentration of brittle phases, achieving "macro-micro-nano" three-level synergistic strengthening, and improving the conductivity of the flat wire.

[0024] Finally, a copper sheet is coated on a high-purity aluminum rod by cold pressure welding to ensure atomic-level clean bonding at the copper-aluminum interface and eliminate resistance jump. During the cold pressure welding process, a strong transverse magnetic field is applied to induce the preferred orientation of copper grains along the crystal plane, improving the conductivity of the flat wire. Then, a copper-clad aluminum flat wire is prepared through cold pressing treatment. Dense forming and surface polishing can maximize the effective utilization of the conductive cross-section, avoid grain growth caused by high temperature, retain the fine-grained structure, and improve the material strength. Specific embodiments

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0026] Example 1: (1) A femtosecond laser with a wavelength of 1030 nm and a pulse width of 300 fs is used to irradiate the surface of a high-purity aluminum rod with a diameter of 3.0 mm under argon protection at an energy density of 2 J / cm². Through instantaneous electron excitation and ultrafast cooling, the cooling rate is 10 12 K / s, and a 50-nm-thick ultra-clean amorphous layer is formed on the surface of the high-purity aluminum rod. Subsequently, the energy density is increased to 3 J / cm 2 , and a spiral scanning path is adopted with a scanning speed of 500 mm / s and an overlap rate of 15% to form a porous structure with micron pits with a diameter of 2 μm and intertwined edge nanowires with a thickness of 50 nm, obtaining a femtosecond laser-pretreated high-purity aluminum rod.

[0027] (2) First, pretreat the high-purity aluminum rod with 160 W argon plasma cleaning for 3 min to remove subsurface impurities. Then, subject the cleaned high-purity aluminum rod to in-situ vacuum preheating with a vacuum degree of 0.5 MPa, a temperature of 150 °C, and a time of 1 h to remove water vapor. Turn on the argon gas with a flow rate of 20 sccm, adjust the air pressure to 5 mTorr, use copper as the target, apply low-power sputtering at 50 W for 5 min, then increase the power to 300 W and start deposition until a 10-μm copper layer is deposited. Then, use a hot-wall ALD system equipped with a copper precursor transport module to deposit a copper layer by ALD. Use bis(hexafluoroacetylacetonate)copper(II) as the copper source, trimethylaluminum as the aluminum source, and hydrogen as the reducing agent. By adjusting the copper / aluminum cycle ratio, achieve a composition gradient. In the initial stage, 100% copper cycle, gradually increase the proportion of aluminum cycle to 5%, reduce the copper cycle ratio, and keep the total ratio of aluminum and copper at 100%. Deposit at 150 °C with a precursor pulse time of 0.1 s for the copper / aluminum precursor and a 0.5-s hydrogen pulse; use high-purity argon for purging for 10 s; the single-cycle thickness is 0.05 nm / cycle to form a 3-μm thick gradient transition layer, and obtain a gradient high-purity aluminum rod;

[0028] (3) Cold-bend a 0.1-mm thick copper sheet and the gradient high-purity aluminum rod into a copper sleeve with an aluminum core in the middle by a set of grooved rolls, and perform multi-pass drawing processing at a speed of 60 m / min and a pass reduction rate of 10% to prepare a round fine wire with a diameter of 0.3 mm. Apply a pressure of 80 MPa through hydraulic pressure under a 1-T transverse magnetic field for a holding time of 10 s, and use a nitrogen atmosphere to prevent oxidation to obtain copper-clad aluminum wire by cold pressure welding; finally, use a four-roll precision rolling mill with the roll surface plated with hard chromium, an initial rolling pressure of 50 MPa, gradually increasing to 100 MPa; the width-to-thickness ratio is gradually pressed from 3:1 to 10:1, the rolling speed is 100 m / min, and then pass Ar / H2 mixed gas into a tube annealing furnace with a flow rate of 10 L / min, where the volume ratio of Ar:H2 = 19:1, hold at 80 °C for 30 min to release residual stress, and obtain a high-conductivity copper-clad aluminum flat wire with a copper sheet coating area ratio of 15%, a thickness of 0.02 mm, and a flat wire width-to-thickness ratio of 10:1.

[0029] Example 2: (1) Use a femtosecond laser with a wavelength of 1030 nm and a pulse width of 300 fs to irradiate the surface of a high-purity aluminum rod with a diameter of 4.0 mm under argon protection at an energy density of 2.5 J / cm 2 . Through electron instantaneous excitation and ultrafast cooling, with a cooling rate of 10 12 K / s, a 75-nm thick ultra-clean amorphous layer is formed on the surface of the high-purity aluminum rod. Subsequently, increase the energy density to 4 J / cm 2, a spiral scanning path is adopted, the scanning speed is 500 mm / s, and the overlap rate is 15%. A porous structure intertwined with micron-sized pits with a diameter of 3.5 μm and edge nanowires of 125 nm is formed to obtain a femtosecond laser-pretreated high-purity aluminum rod;

[0030] (2) First, the high-purity aluminum rod is pretreated by argon plasma cleaning at 180 W for 4 min to remove subsurface impurities. The cleaned high-purity aluminum rod is preheated in situ under vacuum, with a vacuum degree of 0.5 MPa, a temperature of 150 °C, and a time of 1 h to remove water vapor. Argon is turned on with a flow rate of 20 sccm, the pressure is adjusted to 7.5 mTorr, copper is used as the target, and low-power sputtering is carried out at 50 W for 5 min. Then the power is increased to 350 W to start deposition until a 15-μm copper layer is deposited. Then, a hot-wall ALD system equipped with a copper precursor transport module is used for ALD deposition of the copper layer. Bis(hexafluoroacetylacetonato)copper(II) is used as the copper source, trimethylaluminum is used as the aluminum source, and hydrogen is used as the reducing agent. By adjusting the copper / aluminum cycle ratio, a composition gradient is achieved. In the initial stage, 100% copper cycle is used, and the proportion of aluminum cycle is gradually increased to 7.5%, while the copper cycle ratio is decreased, keeping the total ratio of aluminum and copper at 100%. Deposition is carried out at 200 °C, with a precursor pulse time of 0.55 s for the copper / aluminum precursor and 1.25 s for the hydrogen pulse. Purge is carried out with high-purity argon for 15 s. The single-cycle thickness is 0.075 nm / cycle to form a 4-μm-thick gradient transition layer, obtaining a gradient high-purity aluminum rod;

[0031] (3) A copper sheet with a thickness of 0.13 mm and the gradient high-purity aluminum rod are cold-bent by a set of grooved rollers into a copper sleeve with an aluminum core in the middle, and multi-pass drawing is carried out at a speed of 60 m / min and a pass reduction rate of 10% to prepare a round thin wire with a diameter of 0.3 mm. Under a 1.5-T transverse magnetic field, a pressure of 100 MPa is applied hydraulically for 15 s, and a nitrogen atmosphere is used to prevent oxidation. A copper-clad aluminum wire is obtained by cold pressure welding. Finally, a four-roll precision rolling mill with a hard chromium plating on the roll surface is used. The initial rolling pressure is 50 MPa and is gradually increased to 100 MPa; the width-to-thickness ratio is gradually pressed from 3:1 to 10:1, and the rolling speed is 200 m / min. Then, a mixed gas of Ar / H2 is introduced into a tube-type annealing furnace with a flow rate of 15 L / min, where the volume ratio of Ar:H2 = 19:1, and it is kept at 100 °C for 45 min to release residual stress, obtaining a high-conductivity copper-clad aluminum flat wire. The area ratio of the copper sheet coating layer is 25%, the thickness is 0.035 mm, and the width-to-thickness ratio of the flat wire is 5:1.

[0032] Example 3: (1) Using a femtosecond laser with a wavelength of 1030 nm and a pulse width of 300 fs, under argon protection, irradiate the surface of a high-purity aluminum rod with a diameter of 5.0 mm at an energy density of 3 J / cm 2 through electron instantaneous excitation and ultrafast cooling, and the cooling rate is 10 13K / s, a 100-nm-thick ultra-clean amorphous layer is formed on the surface of the high-purity aluminum rod. Subsequently, the energy density is increased to 5 J / cm 2 , using a spiral scanning path, the scanning speed is 500 mm / s, the overlap rate is 15%, a porous structure composed of micron-sized pits with a diameter of 5 μm and intertwined edge nanowires of 200 nm is formed, and a femtosecond laser-pretreated high-purity aluminum rod is prepared;

[0033] (2) First, the pre-treated high-purity aluminum rod is cleaned by 200-W argon plasma for 5 min to remove subsurface impurities. The cleaned high-purity aluminum rod is preheated in situ under vacuum, with a vacuum degree of 0.5 MPa, a temperature of 150 °C, and a time of 1 h to remove water vapor. Argon is turned on, with a flow rate of 20 sccm, the pressure is adjusted to 10 mTorr, using copper as the target, a low power of 50 W is applied for sputtering for 5 min, the power is increased to 400 W, and deposition begins until a 20-μm copper layer is deposited. Then, a hot-wall ALD system equipped with a copper precursor transport module is used for ALD deposition of the copper layer. Bis(hexafluoroacetylacetonato)copper(II) is used as the copper source, trimethylaluminum is used as the aluminum source, and hydrogen is used as the reducing agent. By adjusting the copper / aluminum cycle ratio, a composition gradient is achieved. In the initial stage, 100% copper cycle, and the proportion of aluminum cycle is gradually increased to 10%, and the copper cycle ratio is decreased while maintaining the total ratio of aluminum and copper at 100%. Deposition is carried out at 250 °C, with a precursor pulse time of 1 s for the copper / aluminum precursor and a 2-s hydrogen pulse. Purge is carried out using high-purity argon for 20 s. The single-cycle thickness is 0.1 nm / cycle, and a 5-μm-thick gradient transition layer is formed to obtain a gradient high-purity aluminum rod;

[0034] (3) A copper sheet with a thickness of 0.16 mm and the gradient high-purity aluminum rod are cold-bent by a set of grooved rolls into a copper sleeve with an aluminum core in the middle, and multi-pass drawing is carried out at a speed of 60 m / min and a pass reduction rate of 10% to prepare a round fine wire with a diameter of 0.3 mm. Under a 2-T transverse magnetic field, a pressure of 120 MPa is applied hydraulically, and the pressure holding time is 20 s. A nitrogen atmosphere is used to prevent oxidation, and a copper-clad aluminum wire is obtained by cold pressure welding. Finally, a four-high precision rolling mill with a hard chromium plating on the roll surface is used. The initial rolling pressure is 50 MPa and is gradually increased to 100 MPa. The width-to-thickness ratio is gradually pressed from 3:1 to 10:1, and the rolling speed is 300 m / min. Then, a mixed gas of Ar / H2 is introduced into a tube-type annealing furnace with a flow rate of 20 L / min, where the volume ratio of Ar:H2 = 19:1, and it is kept at 120 °C for 60 min to release residual stress, obtaining a high-conductivity copper-clad aluminum flat wire. The area ratio of the copper sheet coating layer is 40%, the thickness is 0.05 mm, and the maximum width-to-thickness ratio of the flat wire is 4:1.

[0035] Comparative Example 1: (1) Using a femtosecond laser with a wavelength of 1030 nm and a pulse width of 300 fs, under argon protection, at 4 J / cm 2The energy density is adopted, with a spiral scanning path, a scanning speed of 500 mm / s, an overlap rate of 15%, to form a porous structure with micron-sized pits of 3.5 μm in diameter and intertwined edge nanowires of 125 nm, and a femtosecond laser-pretreated high-purity aluminum rod is prepared.

[0036] (2) First, the high-purity aluminum rod is pretreated by argon plasma cleaning at 180 W for 4 min to remove subsurface impurities. The cleaned high-purity aluminum rod is then preheated in situ under vacuum, with a vacuum degree of 0.5 MPa, a temperature of 150 °C, and a time of 1 h to remove water vapor. Argon is turned on with a flow rate of 20 sccm, the air pressure is adjusted to 7.5 mTorr, copper is used as the target, and low-power sputtering is carried out at 50 W for 5 min. Then the power is increased to 350 W to start deposition until a 15-μm copper layer is deposited. Then, a thermal-wall type ALD system equipped with a copper precursor transport module is used for ALD deposition of the copper layer. Bis(hexafluoroacetylacetonato)copper(II) is used as the copper source, trimethylaluminum is used as the aluminum source, and hydrogen is used as the reducing agent. By adjusting the copper / aluminum cycle ratio, a composition gradient is achieved. In the initial stage, 100% copper cycle is carried out, and the proportion of aluminum cycle is gradually increased to 7.5%, while the copper cycle ratio is decreased, keeping the total ratio of aluminum and copper at 100%. Deposition is carried out at 200 °C, with a precursor pulse time of 0.55 s for the copper / aluminum precursor and a 1.25-s hydrogen pulse. Purge is carried out with high-purity argon for 15 s. The single-cycle thickness is 0.075 nm / cycle to form a 4-μm-thick gradient transition layer, and a gradient high-purity aluminum rod is prepared.

[0037] (3) A copper sheet with a thickness of 0.13 mm and the gradient high-purity aluminum rod are cold-bent by a set of grooved rolls into a copper sleeve with an aluminum core in the middle, and multi-pass drawing is carried out at a speed of 60 m / min and a pass reduction rate of 10% to prepare a round thin wire with a diameter of 0.3 mm. A pressure of 100 MPa is applied hydraulically under a 1.5-T transverse magnetic field, and the pressure is maintained for 15 s. A nitrogen atmosphere is used to prevent oxidation, and a copper-clad aluminum wire is obtained by cold pressure welding. Finally, a four-roll precision rolling mill with hard chromium plating on the roll surface is used. The initial rolling pressure is 50 MPa and is gradually increased to 100 MPa. The width-thickness ratio is gradually pressed from 3:1 to 10:1, and the rolling speed is 200 m / min. Then, an Ar / H2 mixed gas is introduced into a tube-type annealing furnace with a flow rate of 15 L / min, where the volume ratio of Ar:H2 = 19:1, and the temperature is maintained at 100 °C for 45 min to release residual stress, and a high-conductivity copper-clad aluminum flat wire is prepared.

[0038] Comparative Example 2: (1) A femtosecond laser with a wavelength of 1030 nm and a pulse width of 300 fs is used to irradiate the surface of a high-purity aluminum rod with a diameter of 4.0 mm under argon protection at an energy density of 2.5 J / cm 2 through electron instantaneous excitation and ultrafast cooling, and the cooling rate is 10 12K / s, generate a 75-nm-thick ultra-clean amorphous layer on the surface of a high-purity aluminum rod to obtain a femtosecond laser-pretreated high-purity aluminum rod;

[0039] (2) First, pre-treat the high-purity aluminum rod with 180 W argon plasma cleaning for 4 min to remove subsurface impurities. Then, in-situ vacuum preheat the cleaned high-purity aluminum rod. The vacuum degree is 0.5 MPa, the temperature is 150 °C, and the time is 1 h to remove water vapor. Turn on the argon gas with a flow rate of 20 sccm, adjust the pressure to 7.5 mTorr, use copper as the target, apply low-power sputtering of 50 W for 5 min, then increase the power to 350 W and start deposition until a 15-μm copper layer is deposited. Then, use a hot-wall ALD system equipped with a copper precursor transport module to deposit a copper layer by ALD. Use bis(hexafluoroacetylacetonato)copper(II) as the copper source, trimethylaluminum as the aluminum source, and hydrogen as the reducing agent. By adjusting the copper / aluminum cycle ratio, achieve a composition gradient. In the initial stage, 100% copper cycle, gradually increase the proportion of aluminum cycle to 7.5%, reduce the copper cycle ratio, and keep the total ratio of aluminum and copper at 100%. Deposit at 200 °C with a precursor pulse time of 0.55 s for the copper / aluminum precursor and a 1.25-s hydrogen pulse. Purge with high-purity argon for 15 s. The single-cycle thickness is 0.075 nm / cycle to form a 4-μm-thick gradient transition layer to obtain a gradient high-purity aluminum rod;

[0040] (3) Cold-bend a 0.13-mm-thick copper sheet and the gradient high-purity aluminum rod into a copper sleeve with an aluminum core in the middle by a set of grooved rolls, and perform multi-pass drawing processing at a speed of 60 m / min and a pass reduction rate of 10% to prepare a round fine wire with a diameter of 0.3 mm. Apply a pressure of 100 MPa by hydraulic pressure under a 1.5-T transverse magnetic field, and the pressure holding time is 15 s. Prevent oxidation in a nitrogen atmosphere, and obtain a copper-clad aluminum wire by cold pressure welding. Finally, use a four-roll precision rolling mill with hard chromium plating on the roll surface. The initial rolling pressure is 50 MPa and gradually increases to 100 MPa. The width-thickness ratio is gradually pressed from 3:1 to 10:1, and the rolling speed is 200 m / min. Then, in a tube annealing furnace, introduce an Ar / H2 mixed gas with a flow rate of 15 L / min, where the volume ratio of Ar:H2 = 19:1, and hold at 100 °C for 45 min to release residual stress to obtain a high-conductivity copper-clad aluminum flat wire.

[0041] Comparative Example 3: (1) Use a femtosecond laser with a wavelength of 1030 nm and a pulse width of 300 fs to irradiate the surface of a high-purity aluminum rod with a diameter of 4.0 mm under argon protection at an energy density of 2.5 J / cm 2 of, through electron instantaneous excitation and ultrafast cooling, the cooling rate is 10 12 K / s, generate a 75-nm-thick ultra-clean amorphous layer on the surface of the high-purity aluminum rod, and then increase the energy density to 4 J / cm 2, a spiral scanning path is adopted, the scanning speed is 500 mm / s, the overlap rate is 15%, a porous structure intertwined with micron-sized pits with a diameter of 3.5 μm and edge nanowires of 125 nm is formed, and a femtosecond laser-pretreated high-purity aluminum rod is prepared;

[0042] (2) A copper sheet with a thickness of 0.13 mm and a femtosecond laser-pretreated high-purity aluminum rod are cold-formed into a copper sleeve with an aluminum core in the middle by a set of hole-shaped rollers, and multi-pass drawing is carried out at a speed of 60 m / min and a pass reduction rate of 10% to prepare a round fine wire with a diameter of 0.3 mm. Under a 1.5 T transverse magnetic field, a pressure of 100 MPa is applied hydraulically, the pressure holding time is 15 s, and a nitrogen atmosphere is used to prevent oxidation. A copper-clad aluminum wire is obtained by cold pressure welding; finally, a four-roll precision rolling mill is used, the surface of the rolling rolls is coated with hard chromium, the initial rolling pressure is 50 MPa, and it is gradually increased to 100 MPa; the width-thickness ratio is gradually pressed from 3:1 to 10:1, the rolling speed is 200 m / min, and then an Ar / H2 mixed gas is introduced into a tube-type annealing furnace, the flow rate is 15 L / min, where the volume ratio of Ar:H2 = 19:1, and the residual stress is released by holding at 100 °C for 45 min to obtain a high-conductivity copper-clad aluminum flat wire.

[0043] Comparative Example 4: (1) A femtosecond laser with a wavelength of 1030 nm and a pulse width of 300 fs is used to irradiate the surface of a high-purity aluminum rod with a diameter of 4.0 mm under argon protection at an energy density of 2.5 J / cm 2 . Through electron instantaneous excitation and ultrafast cooling, the cooling rate is 10 12 K / s, and a 75-nm-thick ultra-clean amorphous layer is formed on the surface of the high-purity aluminum rod. Subsequently, the energy density is increased to 4 J / cm 2 , a spiral scanning path is adopted, the scanning speed is 500 mm / s, the overlap rate is 15%, a porous structure intertwined with micron-sized pits with a diameter of 3.5 μm and edge nanowires of 125 nm is formed, and a femtosecond laser-pretreated high-purity aluminum rod is prepared;

[0044] (2) First, the high-purity aluminum rod is pretreated by argon plasma cleaning with 180 W for 4 min to remove subsurface impurities. The cleaned high-purity aluminum rod is subjected to in-situ vacuum preheating, with a vacuum degree of 0.5 MPa, a temperature of 150 °C, and a time of 1 h to remove water vapor; argon is turned on, the flow rate is 20 sccm, the air pressure is adjusted to 7.5 mTorr, copper is used as the target, and low-power sputtering is carried out at 50 W for 5 min, then the power is increased to 350 W and deposition starts. A 15-μm copper layer is deposited to obtain a deposited copper high-purity aluminum rod;

[0045] (3) A copper sheet with a thickness of 0.13 mm and a deposited copper high-purity aluminum rod are cold-bent by a set of grooved rolls into a copper sleeve with an aluminum core in the middle. Multi-pass drawing is carried out at a speed of 60 m / min and a pass reduction rate of 10% to prepare a round fine wire with a diameter of 0.3 mm. Under a 1.5 T transverse magnetic field, a pressure of 100 MPa is applied hydraulically, and the pressure holding time is 15 s. A nitrogen atmosphere is used to prevent oxidation, and copper-clad aluminum wire is obtained by cold pressure welding; finally, a four-roll precision rolling mill is used, the surface of the rolling rolls is plated with hard chromium, the initial rolling pressure is 50 MPa, and it is gradually increased to 100 MPa; the width-thickness ratio is gradually pressed from 3:1 to 10:1, the rolling speed is 200 m / min, and then an Ar / H2 mixed gas is introduced into a tube annealing furnace, the flow rate is 15 L / min, where the volume ratio of Ar:H2 = 19:1, and it is kept at 100 °C for 45 min to release residual stress, and high-conductivity copper-clad aluminum flat wire is obtained.

[0046] Comparative Example 5: (1) A femtosecond laser with a wavelength of 1030 nm and a pulse width of 300 fs is used to irradiate the surface of a high-purity aluminum rod with a diameter of 4.0 mm under argon protection at an energy density of 2.5 J / cm 2 . Through electron instantaneous excitation and ultrafast cooling, the cooling rate is 10 12 K / s, and a 75-nm-thick ultra-clean amorphous layer is formed on the surface of the high-purity aluminum rod. Subsequently, the energy density is increased to 4 J / cm 2 , a spiral scanning path is adopted, the scanning speed is 500 mm / s, and the overlap rate is 15%, to form a porous structure intertwined with micron-sized pits with a diameter of 3.5 μm and edge nanowires with a thickness of 125 nm, and a femtosecond laser-pretreated high-purity aluminum rod is obtained;

[0047] (2) First, the pre-treated high-purity aluminum rod is cleaned by an argon plasma with 180 W for 4 min to remove subsurface impurities. The cleaned high-purity aluminum rod is preheated in situ in a vacuum, the vacuum degree is 0.5 MPa, the temperature is 150 °C, and the time is 1 h to remove water vapor; argon is turned on, the flow rate is 20 sccm, the air pressure is adjusted to 7.5 mTorr, copper is used as the target, and low-power sputtering is carried out at 50 W for 5 min, then the power is increased to 350 W to start deposition until a 15-μm copper layer is deposited; then a thermal-wall type ALD system equipped with a copper precursor transport module is used for ALD deposition of a copper layer. Bis(hexafluoroacetylacetonate)copper(II) is used as the copper source, trimethylaluminum is used as the aluminum source, and hydrogen is used as the reducing agent. By adjusting the copper / aluminum cycle ratio, a composition gradient is achieved. In the initial stage, 100% copper cycle, and the proportion of aluminum cycle is gradually increased to 7.5%, and the copper cycle ratio is reduced, while keeping the total ratio of aluminum and copper at 100%; deposition is carried out at 200 °C, and the pulse time of the copper / aluminum precursor is 0.55 s and the hydrogen pulse is 1.25 s; purging is carried out with high-purity argon for 15 s; the single-cycle thickness is 0.075 nm per cycle to form a 4-μm-thick gradient transition layer, and a gradient high-purity aluminum rod is obtained.

[0048] (3) A copper sheet with a thickness of 0.13 mm and a gradient high-purity aluminum rod are cold-bent by a set of grooved rolls into a copper sleeve with an aluminum core in the middle. A pressure of 100 MPa is applied hydraulically, and the pressure holding time is 15 s. A nitrogen atmosphere is used to prevent oxidation, and copper-clad aluminum wire is obtained by cold pressure welding. Finally, a four-roll precision rolling mill is used, the surface of the rolling rolls is plated with hard chromium, the initial rolling pressure is 50 MPa, and it is gradually increased to 100 MPa; the width-thickness ratio is gradually pressed from 3:1 to 10:1, the rolling speed is 200 m / min, and then an Ar / H2 mixed gas is introduced into a tube-type annealing furnace with a flow rate of 15 L / min, where the volume ratio of Ar:H2 = 19:1, and the residual stress is released by holding at 100 °C for 45 min to obtain a high-conductivity copper-clad aluminum flat wire.

[0049] Effect Example

[0050] The following Table 1 shows the performance analysis results of a high-conductivity copper-clad aluminum flat wire using Examples 1 to 3 and Comparative Examples 1 to 5 of the present invention.

[0051] Table 1

[0052]

[0053] From the comparison of the experimental data of the elongation at break between the examples and the comparative examples, it can be found that the present invention utilizes the fact that the pulse energy of femtosecond laser is instantaneously absorbed by the free electrons on the surface layer of metallic aluminum, and a surface modification technology for metallic aluminum. Through the non-linear interaction between the extremely short pulse and the material, non-thermal melting-solidification is carried out on the surface of metallic aluminum before cold pressure welding, generating a super-clean amorphous layer without oxidation and grain boundaries, greatly reducing the diffusion activation energy of subsequent cold pressure welding, and realizing low-temperature and high-efficiency atomic bonding, that is, sufficient diffusion can be achieved without annealing, thus avoiding the generation of brittle phases caused by high-temperature annealing and reducing the ductility of the flat wire. From the comparison of the experimental data of the tensile strength between the examples and the comparative examples, it can be found that the present invention induces the formation of a micro-nano porous structure on the aluminum surface during femtosecond laser treatment, and then deposits a copper layer on the aluminum surface by physical vapor deposition (PVD). The micron pits of metallic aluminum and the atomic layer deposited copper penetrate into the pore lines to form a "barb" structure, generating three-dimensional mechanical interlocking. From the comparison of the experimental data of the resistivity between the examples and the comparative examples, it can be found that the micron pits of the present invention serve as mechanical anchors, combined with the nano-network structure of the diffusion channels, and together with the ALD atomic layer deposited gradient layer, act on stress buffering with a gradient composition of aluminum-aluminum copper-copper, realizing atomic-level interdiffusion of copper and aluminum, avoiding the concentration of brittle phases, achieving "macro-micro-nano" three-level synergistic strengthening, and improving the conductivity of the flat wire. The copper sheet is coated on the high-purity aluminum rod by cold pressure welding to ensure atomic-level clean bonding at the copper-aluminum interface and eliminate the resistance jump; a strong transverse magnetic field is applied during the cold pressure welding process to induce the preferred orientation of copper grains along the crystal plane, improving the conductivity of the flat wire; then the copper-clad aluminum flat wire is prepared through cold pressure treatment. Dense forming and surface polishing can maximize the effective utilization of the conductive cross-section, avoid grain growth caused by high temperature, retain the fine-grained structure, and improve the material strength.

[0054] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, in any regard, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be construed as limiting the claimed claim.

Claims

1. A preparation method of a high-conductivity copper-clad aluminum flat wire, characterized in that, It includes the following preparation steps: (1) Using a femtosecond laser, irradiate the surface of a high-purity aluminum rod with a diameter of 3.0 - 5.0 mm under argon protection at an energy density of 2 - 3 J / cm². Through instantaneous electron excitation and ultrafast cooling, the cooling rate is 10 12 -10 13 K / s, and a 50 - 100 nm thick ultra-clean amorphous layer is formed on the surface of the high-purity aluminum rod. Subsequently, the energy density is increased to 3 - 5 J / cm 2 . Adopt a spiral scanning path to form a porous structure with micron-sized pits with a diameter of 2 - 5 μm and intertwined edge nanowires of 50 - 200 nm, and obtain a femtosecond laser-pretreated high-purity aluminum rod; (2) First, pretreat the high-purity aluminum rod with argon plasma cleaning at 160 - 200W for 3 - 5 minutes to remove subsurface impurities. Then, in-situ vacuum preheat the cleaned high-purity aluminum rod with a vacuum degree of 0.5MPa, a temperature of 150°C, and a time of 1h to remove water vapor. Deposit a copper layer of 10 - 20μm through PVD. Then, use a hot-wall ALD system equipped with a copper precursor transport module to deposit a copper layer by ALD. By adjusting the copper / aluminum cycle ratio, achieve a composition gradient. Deposit at 150 - 250°C with a copper / aluminum precursor pulse time of 0.1 - 1s and a hydrogen pulse of 0.5 - 2s. Purge with high-purity argon for 10 - 20s to form a gradient transition layer with a thickness of 3 - 5μm, thus obtaining a gradient high-purity aluminum rod; (3) Cold-bend the copper sheet and the gradient high-purity aluminum rod into a copper sleeve with an aluminum core in the middle by a set of grooved rolls, and perform multi-pass drawing processing at a speed of 60 - 600m / min and a pass reduction rate of 10 - 20% to prepare a round fine wire with a diameter of 0.3 - 3.0mm. Apply a pressure of 80 - 120MPa by hydraulic pressure under a 1 - 2T transverse magnetic field for a holding time of 10 - 20s, and use a nitrogen atmosphere to prevent oxidation. Obtain a copper-clad aluminum wire by cold pressure welding. Finally, cold press with a four-high precision rolling mill and then perform low-temperature annealing to obtain a high-conductivity copper-clad aluminum flat wire.

2. The preparation method of a high-conductivity copper-clad aluminum flat wire according to claim 1, characterized in that, In the step (1), the femtosecond laser has a wavelength of 1030nm and a pulse width of 300fs.

3. The preparation method of a high-conductivity copper-clad aluminum flat wire according to claim 1, characterized in that, In the step (1), the scanning speed of the spiral scanning is 500mm / s, and the overlap rate is 15%.

4. The preparation method of a high-conductivity copper-clad aluminum flat wire according to claim 1, characterized in that, In the step (2), for PVD deposition, turn on argon with a flow rate of 20sccm, adjust the air pressure to 5 - 10mTorr, use copper as the target, apply a low power of 50W for sputtering for 5 minutes, then increase the power to 300 - 400W and start deposition.

5. The preparation method of a high-conductivity copper-clad aluminum flat wire according to claim 1, characterized in that, In the step (2), bis(hexafluoroacetylacetonato)copper(II) is used as the copper source, trimethylaluminum is used as the aluminum source, and hydrogen is used as the reducing agent.

6. The preparation method of a high-conductivity copper-clad aluminum flat wire according to claim 1, characterized in that, In the step (2), during gradient deposition, in the initial stage, 100% copper cycle, and gradually increase the proportion of aluminum cycle to 5 - 10%.

7. The preparation method of a high-conductivity copper-clad aluminum flat wire according to claim 1, characterized in that, In the step (2), the single-cycle thickness is 0.05 - 0.1nm / cycle.

8. The preparation method of a high-conductivity copper-clad aluminum flat wire according to claim 1, wherein, In the step (3), the thickness of the copper sheet is 0.1 - 0.16mm.

9. The preparation method of a high-conductivity copper-clad aluminum flat wire according to claim 1, characterized in that, In the step (3), the cold pressing conditions are: the surface of the rolling rolls is plated with hard chromium, the initial rolling pressure is 50MPa, and it is gradually increased to 100MPa; the width-to-thickness ratio is gradually pressed from 3:1 to 10:1, and the rolling speed is 100 - 300m / min.

10. The preparation method of a high-conductivity copper-clad aluminum flat wire according to claim 1, wherein, In the step (3), the annealing conditions are: introduce an Ar / H2 mixed gas into a tube annealing furnace with a flow rate of 10 - 20L / min, where the volume ratio of Ar:H2 = 19:1, and hold at 80 - 120°C for 30 - 60min to release residual stress.

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