High-strength, high-conductivity and high-temperature-resistant copper-based composite rod wire with nano structure and preparation method thereof

Abstract

The invention belongs to the technical field of copper-based composite materials, and particularly relates to a high-strength, high-conductivity and high-temperature-resistant copper-based composite rod wire with a nano structure and a preparation method thereof. The preparation method comprises the following steps: mixing nanoscale lanthanum hexaboride powder, nanoscale rare earth oxide powder and copper powder to obtain mixed powder, and carrying out plasma-assisted high-energy ball milling on the mixed powder to obtain composite powder; the composite powder is subjected to cold pressing forming, and a green body is obtained; sintering the green body in a reducing atmosphere to obtain a sintered blank; carrying out hot extrusion on the sintered blank to obtain a blank subjected to hot extrusion; continuously extruding the blank subjected to hot extrusion to obtain a wire blank; and the wire blank is sequentially subjected to cold drawing and annealing treatment, and the high-strength, high-conductivity and high-temperature-resistant copper-based composite rod wire is obtained. The high-strength, high-conductivity and high-temperature-resistant copper-based composite rod wire provided by the invention has ultrahigh strength, high electric conductivity and heat conductivity and excellent high-temperature stability.

Description

Technical Field

[0001] This invention belongs to the field of copper-based composite material technology, specifically relating to a high-strength, high-conductivity, and high-temperature resistant copper-based composite rod / wire with a nanostructure and its preparation method. Background Technology

[0002] Copper-based composite materials are an effective way to solve the problems of low strength and easy softening of pure copper. Lanthanum hexaboride (LaB6) is considered an ideal reinforcing phase due to its high melting point, high hardness, and good intrinsic conductivity. Existing technologies add micron-sized lanthanum hexaboride and rare earth elements through melting, which can improve the balance between strength and conductivity to some extent. However, the reinforcing phase is large in size and has limited uniformity of distribution. The improvement of interfacial bonding strength and high-temperature softening resistance has reached a bottleneck, making it difficult to meet the stringent requirements of ultra-high strength (>600MPa) and extremely high heat resistance (>900℃) for materials under extreme conditions such as aerospace and new-generation new energy vehicle motors. At the same time, the high-temperature process inherent in the melting process easily leads to coarsening, agglomeration, and interfacial reactions of lanthanum hexaboride particles, which seriously restricts its reinforcing efficiency. Although the powder metallurgy route can avoid melting defects, the traditional mechanical ball milling process is difficult to achieve a highly dispersed distribution of nanoscale reinforcing phase and a clean, strongly bonded interface.

[0003] In summary, existing copper-based composite materials cannot achieve uniform dispersion of lanthanum hexaboride at the nanoscale as the second phase, and therefore cannot further improve the strength and heat resistance of copper-based composite materials. Summary of the Invention

[0004] The purpose of this invention is to provide a high-strength, high-conductivity, and high-temperature resistant copper-based composite rod and wire with a nanostructure and its preparation method. The high-strength, high-conductivity, and high-temperature resistant copper-based composite rod and wire provided by this invention has ultra-high strength, high electrical and thermal conductivity, and excellent high-temperature stability.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing high-strength, high-conductivity, and high-temperature resistant copper-based composite rods and wires, comprising the following steps: (1) Lanthanum hexaboride powder, rare earth oxide powder and copper powder are mixed to obtain a mixed powder. The particle size of the lanthanum hexaboride powder and rare earth oxide powder is in the nanometer range. The mass percentage of lanthanum hexaboride powder in the mixed powder is 0.5~3.5% and the mass percentage of rare earth oxide powder is 0.01~1%. The mixed powder is subjected to plasma-assisted high-energy ball milling to obtain a composite powder. (2) The composite powder is cold-pressed to obtain a blank; the blank is sintered in a reducing atmosphere to obtain a sintered blank. (3) The sintered billet is hot-extruded to obtain a hot-extruded billet; the hot-extruded billet is continuously extruded to obtain a wire rod, wherein the number of passes of the continuous extrusion is 1 to 10. (4) The wire blank is subjected to cold drawing and annealing treatment in sequence to obtain the high-strength, high-conductivity, high-temperature resistant copper-based composite rod wire.

[0006] Preferably, the copper powder is electrolytic copper, and the mesh size of the copper powder is 50-200 mesh; the particle size of the lanthanum hexaboride powder is 50-500 nm; the rare earth oxide powder includes one or more of cerium oxide, lanthanum oxide and yttrium oxide.

[0007] Preferably, the plasma-assisted high-energy ball milling is carried out in an inert gas atmosphere, the inert gas including argon and / or helium; The conditions for plasma-assisted high-energy ball milling include: a grinding ball diameter of 3-10 mm, a ball-to-material ratio of 10-30:1, a rotation speed of 400-1200 r / min, and a milling time of 12-60 h.

[0008] Preferably, the cold pressing pressure is 150~250 MPa; the reducing atmosphere includes hydrogen; the sintering temperature is 850~950℃; the holding time is 1~2 h; and the relative density of the sintered blank is >98%.

[0009] Preferably, the hot extrusion temperature is 750~900℃, the holding time is 2~4 h, and the deformation of the hot extrusion is 80~95%.

[0010] Preferably, the continuous extrusion temperature is 350~500℃; the diameter of the wire rod is 2~12 mm.

[0011] Preferably, the reduction rate of a single cold drawing pass is ≤20%; the annealing temperature is 300~400℃ and the holding time is 10s~2min; the annealing temperature is 300~400℃ and the holding time is 10s~2min.

[0012] This invention provides a high-strength, high-conductivity, and high-temperature resistant copper-based composite rod and wire prepared by the preparation method described in the above technical solution.

[0013] Preferably, the high-strength, high-conductivity, and high-temperature resistant copper-based composite rod and wire has a (111) texture; the average grain size of the copper matrix of the high-strength, high-conductivity, and high-temperature resistant copper-based composite rod and wire is 100 nm to 1 μm; and the proportion of low ΣCSL special grain boundaries is >40%.

[0014] Preferably, the proportion of (111) texture in the high-strength, high-conductivity, high-temperature resistant copper-based composite rod and wire is >45%.

[0015] This invention provides a method for preparing high-strength, high-conductivity, and high-temperature resistant copper-based composite rods and wires, comprising the following steps: (1) mixing lanthanum hexaboride powder, rare earth oxide powder, and copper powder to obtain a mixed powder, wherein the particle size of the lanthanum hexaboride powder and rare earth oxide powder is nanoscale, and the mass percentage of the lanthanum hexaboride powder in the mixed powder is 0.5~3.5%, and the mass percentage of the rare earth oxide powder is 0.01~1%; the mixed powder is subjected to plasma-assisted high-energy ball milling to obtain a composite powder; (2) the composite powder is cold-pressed to obtain a blank; the blank is sintered in a reducing atmosphere to obtain a sintered blank; (3) the sintered blank is hot-extruded to obtain a hot-extruded blank; the hot-extruded blank is continuously extruded to obtain a wire blank, wherein the number of passes in the continuous extrusion is 1~10; (4) the wire blank is sequentially cold-drawn and annealed to obtain the high-strength, high-conductivity, and high-temperature resistant copper-based composite rods and wires. Compared with existing technologies, this invention has the following advantages: This invention adopts a powder metallurgy approach, obtaining composite powder through plasma-assisted high-energy ball milling. The core of plasma-assisted high-energy ball milling lies in utilizing the instantaneous high temperature of plasma to activate the surface of the raw material powder, and using high-energy mechanical force to force lanthanum hexaboride powder and rare earth oxide powder to form a composite with copper powder in an "embedding-coating" mode, fundamentally solving the technical problems of uneven dispersion of nano-reinforcing phases and interface wetting. Then, this invention uses cold pressing and reducing atmosphere-protected sintering to achieve a strong metallurgical bond between particles in the composite powder through atomic diffusion, obtaining a high-density sintered billet. After obtaining the sintered billet, this invention continues continuous extrusion after hot extrusion, using intense shear deformation to further break down the initial powder boundaries, forcing the sintered billet to undergo intense plastic deformation during continuous extrusion, refining the matrix grains, eliminating micropores, increasing density, and making the distribution of nano-reinforcing phases more uniform. Finally, this invention employs cold drawing and annealing to adjust the dislocation structure and recrystallization degree, optimizing the strength and conductivity matching of the copper-based composite material to obtain high-strength, high-conductivity, and high-temperature resistant copper-based composite rods and wires. In summary, the preparation method provided by this invention utilizes the synergistic effect of plasma-assisted high-energy ball milling and continuous extrusion, achieving precise control of the microstructure of copper-based materials from the nanometer to the micrometer scale, which is impossible with traditional smelting methods. Therefore, this invention solves the problems of nanoscale dispersion and interface control that cannot be addressed by existing smelting methods, avoiding agglomeration and interface contamination of nanopowder raw materials, and enhancing interfacial bonding. The preparation method provided by this invention, through nanostructure design, achieves uniform dispersion of the second phase at the nanoscale, atomic-level interfacial bonding, and precise control of matrix grains, thereby achieving a simultaneous leapfrog improvement in strength, conductivity, and heat resistance. Its high-temperature softening temperature (950℃), strength level (700MPa), and conductivity (97% IACS) are far superior to those of copper-based composite materials disclosed in existing technologies, meeting the application needs of cutting-edge fields.

[0016] Furthermore, in this invention, the cold drawing is a multi-pass cold drawing, and the area reduction rate of a single pass is ≤20%. This invention ensures the stability of the cold drawing process and reduces the risk of wire breakage by controlling the area reduction rate of a single pass. Attached Figure Description

[0017] Figure 1 Microstructure characterization diagram of the sample prepared in Example 1; Figure 1 (a) in the diagram is a grain diagram; Figure 1 (b) in the diagram is the grain orientation diagram. Detailed Implementation

[0018] This invention provides a method for preparing high-strength, high-conductivity, and high-temperature resistant copper-based composite rods and wires, comprising the following steps: (1) Lanthanum hexaboride powder, rare earth oxide powder and copper powder are mixed to obtain a mixed powder. The particle size of the lanthanum hexaboride powder and rare earth oxide powder is in the nanometer range. The mass percentage of lanthanum hexaboride powder in the mixed powder is 0.5~3.5% and the mass percentage of rare earth oxide powder is 0.01~1%. The mixed powder is subjected to plasma-assisted high-energy ball milling to obtain a composite powder. (2) The composite powder is cold-pressed to obtain a blank; the blank is sintered in a reducing atmosphere to obtain a sintered blank. (3) The sintered billet is hot-extruded to obtain a hot-extruded billet; the hot-extruded billet is continuously extruded to obtain a wire rod, wherein the number of passes of the continuous extrusion is 1 to 10. (4) The wire blank is subjected to cold drawing and annealing treatment in sequence to obtain the high-strength, high-conductivity, high-temperature resistant copper-based composite rod wire.

[0019] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0020] This invention mixes lanthanum hexaboride powder, rare earth oxide powder, and copper powder to obtain a mixed powder. The particle size of the lanthanum hexaboride powder and rare earth oxide powder is in the nanometer range. The mass percentage of lanthanum hexaboride powder in the mixed powder is 0.5-3.5%, and the mass percentage of rare earth oxide powder is 0.01-1%. In this invention, the particle size of the lanthanum hexaboride powder is preferably 50-500 nm, and in the embodiments it can be 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, or 500 nm. The rare earth oxide powder preferably includes one or more of cerium oxide (CeO2), lanthanum oxide (La2O3), and yttrium oxide (Y2O3), and in the embodiments it can be cerium oxide or lanthanum oxide. The copper powder is preferably electrolytic copper. The mesh size of the copper powder is preferably 50-200 mesh, and in the embodiments it can be 50 mesh, 200 mesh, or 125 mesh. The mass percentage of lanthanum hexaboride powder in the mixed powder is 0.5-3.5%, preferably 0.5-3%, and in the embodiments it can be 0.5%, 2%, 1% or 3%. The mass percentage of rare earth oxide powder in the mixed powder is 0.01-1%, preferably 0.05-1%. In the embodiments it can be 0.1%, 1%, 0.2% or 0.5%. The mixed powder also includes copper powder in the remaining mass percentage. The present invention does not have special requirements for the specific implementation of the mixing method; it is sufficient to ensure that the three raw materials are mixed evenly.

[0021] After obtaining the mixed powder, the present invention performs plasma-assisted high-energy ball milling on the mixed powder to obtain a composite powder. In the present invention, the plasma-assisted high-energy ball milling is preferably carried out in an inert gas atmosphere, which preferably includes argon and / or helium. Performing plasma-assisted high-energy ball milling in an inert gas atmosphere can effectively reduce the introduction of impurities during the plasma-assisted high-energy ball milling process. The plasma-assisted high-energy ball milling preferably uses grinding balls. The grinding balls are preferably cerium oxide grinding balls. The preferred conditions for the plasma-assisted high-energy ball milling include: the grinding ball diameter is preferably 3~10 mm, and in the examples, it can be 5 mm, 10 mm, 6 mm, or 8 mm. The ball-to-powder ratio is preferably 10~30:1, and in the examples, it can be 10:1, 30:1, or 20:1. The ball milling speed is preferably 400~1200 r / min, and in the examples, it can be 400 r / min, 1200 r / min, 600 r / min, or 1000 r / min. The ball milling time is preferably 12 to 60 hours, and in the examples it can be 48 hours, 60 hours or 12 hours.

[0022] This invention controls the conditions of plasma-assisted high-energy ball milling, utilizing the instantaneous high temperature of plasma to activate the powder surface, causing the raw material powder to undergo repeated welding, fracture, and refinement during plasma-assisted high-energy ball milling. With the help of high-energy mechanical force, lanthanum hexaboride and rare earth oxide nanoparticles are forced to form a composite with copper powder in an "embedding-coating" mode. Ultimately, lanthanum hexaboride particles are uniformly embedded in the interior of copper particles or firmly attached to their surface at the nano / submicron scale, forming a composite powder with a nanostructure.

[0023] After obtaining the composite powder, the present invention cold-presses the composite powder to obtain a green body; the green body is then sintered in a reducing atmosphere to obtain a sintered green body. In this invention, the cold-pressing pressure is preferably 150-250 MPa, and in embodiments it can be 220 MPa, 200 MPa, 250 MPa, or 150 MPa; the reducing atmosphere preferably includes hydrogen, and may also include nitrogen. In embodiments, the reducing atmosphere can be hydrogen. The sintering temperature is 850-950℃, and in embodiments it can be 925℃, 900℃, 950℃, or 850℃. The sintering holding time is preferably 1-2 h, and in embodiments it can be 1 h. The relative density of the sintered green body is preferably >98%. The diameter of the sintered green body is preferably 40-85 mm, and in embodiments it can be 60 mm, 40 mm, 83 mm, or 60 mm.

[0024] By controlling the pressure of the cold pressing and the temperature and time of sintering, this invention can further enable the powder particles to form a strong metallurgical bond through atomic diffusion, thereby improving densification.

[0025] After obtaining the sintered billet, the present invention performs hot extrusion on the sintered billet to obtain a hot-extruded billet; the hot-extruded billet is continuously extruded to obtain a wire rod, wherein the number of continuous extrusion passes is 1 to 10.

[0026] In this invention, the hot extrusion temperature is preferably 750~900℃, and in the embodiments it can be 800℃, 900℃ or 825℃. The holding time for hot extrusion is 2~4 h, and in the embodiments it can be 2 h or 3 h. The deformation amount of hot extrusion is preferably 80~95%, and in the embodiments it can be 91%, 94%, 84% or 88%.

[0027] In this invention, the continuous extrusion is preferably carried out in a continuous extrusion press using an extrusion die. The temperature of the continuous extrusion is the temperature of the extrusion die. In this invention, the temperature of the continuous extrusion is 350~500℃, and in the embodiments it can be 400℃ or 450℃. The number of passes in the continuous extrusion is preferably 4 passes, 6 passes, 1 pass, or 5 passes; the diameter of the wire rod is 2~12 mm, preferably 4~11 mm, and in the embodiments it can be 5 mm, 10 mm, 12 mm, or 8 mm.

[0028] This invention optimizes the conditions of hot extrusion, thereby further eliminating porosity, increasing density, and refining grain size.

[0029] This invention optimizes the conditions of continuous extrusion. The hot-extruded billet is placed in a continuous extruder. Under the high-speed shearing and friction of the extrusion rollers, the billet undergoes severe plastic deformation. The severe shear deformation further breaks down the initial powder boundaries, refines the matrix grains, eliminates micropores, and makes the distribution of the nano-reinforcing phase more uniform.

[0030] After obtaining the wire blank, the present invention performs cold drawing and annealing treatment on the wire blank in sequence to obtain the high-strength, high-conductivity, high-temperature resistant copper-based composite rod wire.

[0031] In this invention, the cold drawing is preferably performed in multiple passes, more preferably in 30 to 50 passes. In the embodiments, the multiple passes can be 50, 35, 40, or 45 passes. In this invention, the reduction rate of the surface area per pass is preferably ≤20%, and in the embodiments it can be 10 to 20%. In this invention, an initial wire is obtained after the cold drawing process. The diameter of the initial wire is preferably 0.1~1 mm, and in the embodiments it can be 0.1 mm, 1 mm, 0.8 mm or 0.2 mm.

[0032] In this invention, the annealing temperature is 300~400℃, and in the embodiments it can be 400℃ or 350℃. The holding time of the annealing is 10s~2min, and in the embodiments it can be 10s, 30s, 1min or 30s. The cooling method of the annealing is preferably air cooling.

[0033] By controlling the temperature and holding time of the annealing process, this invention can further adjust the dislocation structure and recrystallization degree, and optimize the matching of strength and conductivity.

[0034] This invention provides a high-strength, high-conductivity, and high-temperature resistant copper-based composite rod and wire prepared by the preparation method described in the above technical solution.

[0035] In this invention, the LaB6 reinforcing phase in the high-strength, high-conductivity, and high-temperature resistant copper-based composite rod and wire is highly dispersed at the nanoscale within and at the grain boundaries of the copper matrix. The high-strength, high-conductivity, and high-temperature resistant copper-based composite rod and wire has a (111) texture. The proportion of the (111) texture in the high-strength, high-conductivity, and high-temperature resistant copper-based composite rod and wire is preferably >45%. The average grain size of the copper matrix in the high-strength, high-conductivity, and high-temperature resistant copper-based composite rod and wire is preferably 100 nm to 1 μm. The proportion of low-ΣCSL special grain boundaries in the high-strength, high-conductivity, and high-temperature resistant copper-based composite rod and wire is preferably >40%.

[0036] In this invention, the high-strength, high-conductivity, and high-temperature resistant copper-based composite rod and wire has a tensile strength ≥700 MPa, a conductivity ≥90% (up to 97% IACS), a thermal conductivity ≥330 W / (m·K), and a high-temperature softening temperature ≥950℃.

[0037] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0038] Example 1 Step (1): Raw material preparation and plasma high-energy ball milling composite treatment: Select 50-mesh electrolytic copper powder and lanthanum hexaboride powder with a particle size of 50 nm, mix them at a ratio of 0.5 wt% lanthanum hexaboride, and add 0.1 wt% CeO2 powder. Mix the above raw materials thoroughly. Then, place the mixed powder in a plasma high-energy ball mill and ball mill it under an argon protective atmosphere. This process utilizes the instantaneous high temperature effect of plasma on the powder surface to achieve surface purification and activation. At the same time, high-energy mechanical collision (using high-purity cerium oxide grinding balls with a diameter of 5 mm, a ball-to-material ratio of 10:1, a rotation speed of 400 r / min, and a ball milling time of 48 h) causes the powder to undergo repeated welding, fracture, and refinement. Finally, lanthanum hexaboride particles are uniformly embedded in the interior of copper particles or firmly attached to their surface at the nano / submicron scale, forming a composite powder with a nanostructure.

[0039] Step (2): Cold pressing and atmosphere-protected sintering: The composite powder after ball milling in step (1) was cold pressed into a blank under a pressure of 150 MPa, and then sintered in a hydrogen reducing atmosphere. The sintering temperature was 850℃ and the holding time was 2 h, so that the powder particles formed a strong metallurgical bond through atomic diffusion, and a high-density sintered blank with a diameter of 60 mm was obtained.

[0040] Step (3): Hot extrusion / continuous extrusion densification and microstructure optimization: The sintered billet obtained in step (2) was held at 800℃ for 2 h and then subjected to hot extrusion deformation with an extrusion deformation amount of 91% to further eliminate porosity, increase density and refine grains. The hot-extruded billet was placed in a continuous extruder. Under the high-speed shearing and friction of the extrusion rollers, the billet underwent severe plastic deformation. The extrusion die was heated to 400℃ and the extrusion was performed in 4 passes to obtain a wire rod with a diameter of 5 mm.

[0041] Step (4): Multi-pass cold drawing and annealing: The wire blank obtained in step (3) is subjected to 50 passes of cold drawing deformation. The area reduction rate of a single pass of cold drawing is controlled at 10~20% to obtain a wire with a diameter of 0.1 mm. The wire is kept at 400℃ for 10s and then air-cooled to obtain Cu-LaB6 composite wire with high strength, high conductivity and excellent high temperature stability.

[0042] Figure 1 Microstructure of the Cu-LaB6 composite filament sample prepared in Example 1: Figure 1 (a) in the diagram is a grain diagram; Figure 1 (b) in the figure is the grain orientation diagram. The average grain size of the material prepared by this embodiment is 200 nm, the number of special grain boundaries (low ΣCSL) reaches 45%, and the (111) texture accounts for 57.5%. The performance of the prepared material was tested, and the results are shown in Table 1. The tensile strength test was conducted according to GB / T 228.1-2021, the electrical conductivity test was conducted according to GB / T 351-2019, the thermal conductivity test was conducted according to GB / T22588-2008, and the softening temperature test was conducted according to GB / T 33370-2016.

[0043] Example 2 Step (1): Raw material preparation and plasma high-energy ball milling composite treatment: Select 200-mesh electrolytic copper powder and lanthanum hexaboride powder with a particle size of 500 nm, mix them at a ratio of 2 wt% lanthanum hexaboride, and add 1 wt% CeO2 powder. Mix the above raw materials thoroughly. Then, place the mixed powder in a plasma high-energy ball mill and ball mill it under a helium protective atmosphere. This process utilizes the instantaneous high temperature effect of plasma on the powder surface to achieve surface purification and activation. At the same time, high-energy mechanical collision (using high-purity cerium oxide grinding balls with a diameter of 10 mm, a ball-to-material ratio of 30:1, a rotation speed of 1200 r / min, and a ball milling time of 60 h) causes the powder to undergo repeated welding, fracture, and refinement. Finally, lanthanum hexaboride particles are uniformly embedded in the interior of copper particles or firmly attached to their surface at the nano / submicron scale, forming a composite powder with a nanostructure.

[0044] Step (2): Cold pressing and atmosphere-protected sintering: The composite powder after ball milling in step (1) was cold pressed into a blank under a pressure of 250 MPa, and then sintered in a hydrogen reducing atmosphere. The sintering temperature was 950℃ and the holding time was 1 h, so that the powder particles formed a strong metallurgical bond through atomic diffusion, and a sintered blank with a diameter of 83 mm was obtained.

[0045] Step (3): Hot extrusion / continuous extrusion densification and microstructure optimization: The sintered billet obtained in step (2) was held at 900℃ for 2 h and then subjected to hot extrusion deformation. The extrusion deformation amount was controlled at 94% to further eliminate porosity, increase density and refine grains. The hot-extruded billet was placed in a continuous extruder. Under the high-speed shearing and friction of the extrusion rollers, the billet underwent severe plastic deformation. The extrusion die was heated to 450℃ and the extrusion passes were 6 times to obtain a wire rod with a diameter of 10 mm.

[0046] Step (4): Multi-pass cold drawing and annealing: The wire blank obtained in step (3) is subjected to 35 passes of cold drawing deformation. The area reduction rate of a single pass of cold drawing is controlled at 10~20%, and finally a wire with a diameter of 0.5 mm is obtained. The wire is kept at 400℃ for 30s and then air-cooled to obtain Cu-LaB6 composite wire with high strength, high conductivity and excellent high temperature stability.

[0047] The material prepared using this embodiment has an average grain size of 975 nm, a special grain boundary (low ΣCSL) quantity of 42.5%, and a (111) texture ratio of 45.5%. The prepared material was subjected to performance tests, and the results are shown in Table 1. The tensile strength test was conducted according to GB / T 228.1-2021, the electrical conductivity test was conducted according to GB / T 351-2019, the thermal conductivity test was conducted according to GB / T 22588-2008, and the softening temperature test was conducted according to GB / T 33370-2016.

[0048] Example 3 Step (1): Raw material preparation and plasma high-energy ball milling composite treatment: 125-mesh electrolytic copper powder and 100nm lanthanum hexaboride powder were selected and mixed at a ratio of 1 wt% lanthanum hexaboride, with 0.2 wt% La2O3 powder added. The raw materials were thoroughly mixed. Subsequently, the mixed powder was placed in a plasma high-energy ball mill and ball milled under an argon protective atmosphere. This process utilizes the instantaneous high temperature effect of plasma on the powder surface to achieve surface purification and activation. At the same time, high-energy mechanical collision (using high-purity cerium oxide grinding balls with a diameter of 6 mm, a ball-to-material ratio of 20:1, a rotation speed of 600 r / min, and a ball milling time of 12 h) causes the powder to undergo repeated welding, fracture, and refinement, ultimately achieving uniform embedding of lanthanum hexaboride particles into the interior of copper particles or firm adhesion to their surface at the nano / submicron scale, forming a composite powder with a nanostructure.

[0049] The core innovation of this step lies in completely solving the problem of uniform dispersion and strong interfacial bonding of the lanthanum hexaboride reinforcing phase in the copper matrix.

[0050] Step (2): Cold pressing and atmosphere-protected sintering: The composite powder after ball milling in step (1) was cold pressed into a blank under a pressure of 200 MPa, and then sintered in a hydrogen reducing atmosphere. The sintering temperature was 900℃ and the holding time was 1 h, so that the powder particles formed a strong metallurgical bond through atomic diffusion, and a sintered blank with a diameter of 40 mm was obtained.

[0051] Step (3): Hot extrusion / continuous extrusion densification and microstructure optimization: The sintered billet obtained in step (2) was held at 825℃ for 3 h and then subjected to hot extrusion deformation. The extrusion deformation amount was controlled at 84% to further eliminate porosity, increase density and refine grains. The hot-extruded billet was placed in a continuous extruder. Under the high-speed shearing and friction of the extrusion rollers, the billet underwent severe plastic deformation. The extrusion die was heated to 450℃ and the extrusion was performed in one pass to obtain a rod billet with a diameter of 12 mm.

[0052] Step (4): Multi-pass cold drawing and annealing treatment: The rod obtained in step (3) is subjected to 40 passes of cold drawing deformation. The reduction rate of the surface area of ​​each pass of cold drawing is controlled at 10~20% to obtain a wire with a diameter of 0.8 mm. The wire is then subjected to 350℃ heat treatment for 1 min and air-cooled annealing treatment to obtain Cu-LaB6 composite wire with high strength, high conductivity and excellent high temperature stability.

[0053] The material prepared using this embodiment has an average grain size of 735 nm, a special grain boundary number (low ΣCSL) of 43.5%, and a (111) texture ratio of 46.8%. The prepared material was subjected to performance tests, and the results are shown in Table 1. The tensile strength test was conducted according to GB / T 228.1-2021, the electrical conductivity test was conducted according to GB / T 351-2019, the thermal conductivity test was conducted according to GB / T 22588-2008, and the softening temperature test was conducted according to GB / T 33370-2016.

[0054] Example 4 Step (1): Raw material preparation and plasma high-energy ball milling composite treatment: 200-mesh electrolytic copper powder and lanthanum hexaboride powder with a particle size of 300 nm were selected and mixed at a ratio of 3 wt% lanthanum hexaboride, and 0.5 wt% CeO2 powder was added. The raw materials were thoroughly mixed. Then, the mixed powder was placed in a plasma high-energy ball mill and ball milled under a helium protective atmosphere. This process utilizes the instantaneous high temperature effect of plasma on the powder surface to achieve surface purification and activation. At the same time, high-energy mechanical collision (using high-purity cerium oxide grinding balls with a diameter of 8 mm, a ball-to-material ratio of 20:1, a rotation speed of 1000 r / min, and a ball milling time of 48 h) causes the powder to undergo repeated welding, fracture, and refinement, ultimately achieving that the lanthanum hexaboride particles are uniformly embedded in the interior of copper particles or firmly attached to their surface at the nano / submicron scale, forming a composite powder with a nanostructure.

[0055] Step (2): Cold pressing and atmosphere-protected sintering: The composite powder after ball milling in step (1) was cold pressed into a blank under a pressure of 220 MPa, and then sintered in a hydrogen reducing atmosphere. The sintering temperature was 925℃ and the holding time was 1 h, so that the powder particles formed a strong metallurgical bond through atomic diffusion, and a sintered blank with a diameter of 60 mm was obtained.

[0056] Step (3): Hot extrusion / continuous extrusion densification and microstructure optimization: The sintered billet obtained in step (2) was held at 900℃ for 2 h and then subjected to hot extrusion deformation. The extrusion deformation amount was controlled at 88% to further eliminate porosity, improve density and refine grains. The hot-extruded billet was placed in a continuous extruder. Under the high-speed shearing and friction of the extrusion rollers, the billet underwent severe plastic deformation. The extrusion die was heated to 400℃ and the extrusion passes were 5 times to obtain a wire rod with a diameter of 8 mm.

[0057] Step (4): Multi-pass cold drawing and annealing: The wire blank obtained in step (3) is subjected to 45 passes of cold drawing deformation. The reduction rate of the surface area of ​​a single pass of cold drawing is controlled at 10~20%, and finally a wire with a diameter of 0.2 mm is obtained. The wire is then subjected to 400℃ heat treatment for 30s and air cooling treatment to obtain Cu-LaB6 composite wire with high strength, high conductivity and excellent high temperature stability.

[0058] The material prepared using this embodiment has an average grain size of 326 nm, a special grain boundary number (low ΣCSL) of 46%, and a texture ratio of 55.8%. The prepared material was subjected to performance testing, and the results are shown in Table 1. The tensile strength test was conducted according to GB / T 228.1-2021, the electrical conductivity test was conducted according to GB / T 351-2019, the thermal conductivity test was conducted according to GB / T 22588-2008, and the softening temperature test was conducted according to GB / T 33370-2016.

[0059] Comparative Example 1: Lack of continuous extrusion Step (1): Raw material preparation and high-energy ball milling: 200-mesh electrolytic copper powder and 500 nm lanthanum hexaboride powder were selected and mixed at a ratio of 2 wt% lanthanum hexaboride, with 1 wt% CeO2 powder added. The raw materials were then thoroughly mixed. The mixed powder was then placed in a plasma high-energy ball mill and ball-milled under an argon protective atmosphere. High-purity cerium oxide grinding balls with a diameter of 10 mm were used, with a ball-to-material ratio of 30:1, a rotation speed of 1200 r / min, and a milling time of 60 h.

[0060] Step (2): Cold pressing and atmosphere-protected sintering: The composite powder after ball milling in step (1) was cold pressed into a blank under a pressure of 250 MPa, and then sintered in a hydrogen reducing atmosphere. The sintering temperature was 950℃ and the holding time was 1 h, so that the powder particles formed a strong metallurgical bond through atomic diffusion, and a sintered blank with a diameter of 83 mm was obtained.

[0061] Step (3): Hot extrusion densification and microstructure optimization: The sintered billet obtained in step (2) is heated at 900℃ for 2 hours and then subjected to hot extrusion deformation, with the extrusion deformation amount controlled at 94%.

[0062] Step (4): Multi-pass cold drawing and annealing treatment: The rod obtained in step (3) is subjected to multi-pass cold drawing deformation. The area reduction rate of a single pass of cold drawing is controlled at 10~20%, and finally a wire with a diameter of 1 mm is obtained. The wire is kept at 400℃ for 30s and then air-cooled to obtain Cu-LaB6 composite wire.

[0063] The material prepared using this comparative example has an average grain size of 10.5 μm, a special grain boundary (low ΣCSL) number of 26.2%, and a (111) texture ratio of 28.5%. The prepared material was subjected to performance tests, and the results are shown in Table 1. The tensile strength test was conducted according to GB / T 228.1-2021, the electrical conductivity test was conducted according to GB / T 351-2019, the thermal conductivity test was conducted according to GB / T 22588-2008, and the softening temperature test was conducted according to GB / T 33370-2016.

[0064] Comparative Example 2: Excessive addition of lanthanum hexaboride Step (1): Raw material preparation and plasma high-energy ball milling composite treatment: Select 125-mesh electrolytic copper powder and lanthanum hexaboride powder with a particle size of 200 nm, and mix the raw materials thoroughly at a ratio of 4 wt% lanthanum hexaboride. Then, place the mixed powder in a plasma high-energy ball mill and ball mill it under an argon protective atmosphere. This process utilizes the instantaneous high temperature effect of plasma on the powder surface to achieve surface purification and activation. At the same time, with the help of high-energy mechanical collision (using high-purity cerium oxide grinding balls with a diameter of 6 mm, a ball-to-material ratio of 20:1, a rotation speed of 600 r / min, and a ball milling time of 12 h), the powder undergoes repeated welding, fracture, and refinement, ultimately achieving that the lanthanum hexaboride particles are uniformly embedded in the interior of copper particles or firmly attached to their surface at the nano / submicron scale, forming a composite powder with a nanostructure.

[0065] Step (2): Cold pressing and atmosphere-protected sintering: The composite powder after ball milling in step (1) was cold pressed into a blank under a pressure of 200 MPa, and then sintered in a hydrogen reducing atmosphere. The sintering temperature was 900℃ and the holding time was 1 h, so that the powder particles formed a strong metallurgical bond through atomic diffusion, and a sintered blank with a diameter of 40 mm was obtained.

[0066] Step (3): Hot extrusion / continuous extrusion densification and microstructure optimization: The sintered billet obtained in step (2) was held at 825℃ for 3 h and then subjected to hot extrusion deformation. The extrusion deformation amount was controlled at 84% to further eliminate porosity, improve density and refine grains. The hot-extruded billet was placed in a continuous extruder. The extrusion die was heated to 450℃ and the extrusion was performed in one pass to obtain a rod billet with a diameter of 12 mm.

[0067] Step (4): Multi-pass cold drawing and annealing: The rod obtained in step (3) is subjected to multi-pass cold drawing deformation. The area reduction rate of a single pass cold drawing is controlled at 10~20%. Due to the excessive amount of lanthanum hexaboride added and the lack of rare earth oxides to refine the powder, lanthanum hexaboride agglomerates, resulting in poor material processing performance and wire breakage during the drawing process. It is impossible to obtain ultra-fine composite wire (in the continuous drawing process, after the diameter is less than 0.8 mm, the wire breakage rate increases during the drawing process, so 1 mm wire is selected for preparation in Comparative Example 2). The obtained wire with a diameter of 1 mm is kept at 350℃ for 1 min and then air-cooled to obtain Cu-LaB6 composite wire.

[0068] The material prepared using this comparative example has an average grain size of 4.5 μm, a special grain boundary (low ΣCSL) number of 36.5%, and a (111) texture ratio of 32.0%. The prepared material was subjected to performance tests, and the results are shown in Table 1. The tensile strength test was conducted according to GB / T 228.1-2021, the electrical conductivity test was conducted according to GB / T 351-2019, the thermal conductivity test was conducted according to GB / T 22588-2008, and the softening temperature test was conducted according to GB / T 33370-2016.

[0069] Comparative Example 3: Lanthanum hexaboride particles are too large Step (1): Raw material preparation and plasma high-energy ball milling composite treatment: 50-mesh electrolytic copper powder and lanthanum hexaboride powder with a particle size of 5 μm were selected and mixed at a ratio of 0.5 wt% lanthanum hexaboride mass fraction, and 0.1 wt% La2O3 was added. The raw materials were thoroughly mixed. Then, the mixed powder was placed in a plasma high-energy ball mill and ball milled under an argon protective atmosphere. This process utilizes the instantaneous high temperature effect of plasma on the powder surface to achieve surface purification and activation. At the same time, high-energy mechanical collision (using high-purity cerium oxide grinding balls with a diameter of 5 mm, a ball-to-material ratio of 10:1, a rotation speed of 400 r / min, and a ball milling time of 48 h) causes the powder to undergo repeated welding, fracture, and refinement. Due to the large particle size of the added lanthanum hexaboride powder, plasma high-energy ball milling could not completely break down the lanthanum hexaboride, and a nanostructured composite powder was not obtained.

[0070] Step (2): Cold pressing and atmosphere-protected sintering: The composite powder after ball milling in step (1) was cold pressed into a blank under a pressure of 150 MPa, and then sintered in a hydrogen reducing atmosphere. The sintering temperature was 850℃ and the holding time was 2 h, so that the powder particles formed a strong metallurgical bond through atomic diffusion, and a high-density sintered blank with a diameter of 60 mm was obtained.

[0071] Step (3): Hot extrusion / continuous extrusion densification and microstructure optimization: The sintered billet obtained in step (2) was held at 800℃ for 2 h and then subjected to hot extrusion deformation with an extrusion deformation amount of 91% to further eliminate porosity, increase density and refine grains. The hot-extruded billet was placed in a continuous extruder with the extrusion die heated to 400℃ and the extrusion passes being 4 to obtain a wire rod with a diameter of 5 mm.

[0072] Step (4): Multi-pass cold drawing and annealing: The wire obtained in step (3) is subjected to multi-pass cold drawing deformation. The area reduction rate of a single pass cold drawing is controlled at 10~20%. Due to the large particle size of the added lanthanum hexaboride, wire breakage occurs during the drawing process, and ultra-fine composite wire cannot be prepared. The obtained wire blank with a diameter of 3 mm is kept at 400℃ for 2 min and then air-cooled for annealing to obtain Cu-LaB6 composite wire.

[0073] The material prepared using this comparative example has an average grain size of 14.5 μm, a special grain boundary number (low ΣCSL) of 16.5%, and a (111) texture ratio of 33.0%. The prepared material was subjected to performance tests, and the results are shown in Table 1. The tensile strength test was conducted according to GB / T 228.1-2021, the electrical conductivity test was conducted according to GB / T 351-2019, the thermal conductivity test was conducted according to GB / T 22588-2008, and the softening temperature test was conducted according to GB / T 33370-2016.

[0074] Table 1. Properties of Cu-LaB6 composite rods and wires prepared in the examples and comparative examples.

[0075] As can be seen from the above embodiments, the preparation method provided by the present invention employs the synergistic effect of plasma-assisted high-energy ball milling and continuous extrusion, achieving precise control of the microstructure of copper-based materials from the nanometer to the micrometer scale, which is impossible with traditional smelting. Thus, the present invention solves the problems of nanoscale dispersion and interface control that cannot be addressed by smelting methods in the prior art, avoiding agglomeration and interface contamination of nanopowder raw materials, and achieving enhanced interfacial bonding. The preparation method provided by the present invention, through nanostructure design, achieves uniform dispersion of the second phase at the nanoscale, atomic-level interfacial bonding, and precise control of matrix grains, thereby achieving a simultaneous leapfrog improvement in strength, conductivity, and heat resistance. Its high-temperature softening temperature (950℃), strength level (700MPa), and conductivity (97% IACS) are far superior to those of copper-based composite materials disclosed in the prior art, meeting the application needs of cutting-edge fields.

[0076] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing high-strength high-conductivity high-temperature-resistant copper-based composite rod wire, characterized in that, The method comprises the following steps: (1) mixing lanthanum hexaboride powder, rare earth oxide powder and copper powder to obtain a mixed powder, wherein the particle size of the lanthanum hexaboride powder and the rare earth oxide powder is nanoscale, the mass percentage of the lanthanum hexaboride powder in the mixed powder is 0.5-3.5%, and the mass percentage of the rare earth oxide powder in the mixed powder is 0.01-1%; and the mixed powder is subjected to plasma-assisted high-energy ball milling to obtain a composite powder; (2) cold-pressing the composite powder to obtain a green body; and sintering the green body in a reducing atmosphere to obtain a sintered blank; (3) hot extruding the sintered blank to obtain a hot-extruded blank; and continuously extruding the hot-extruded blank to obtain a wire blank, wherein the pass number of the continuous extrusion is 1-10; (4) sequentially subjecting the wire blank to cold drawing and annealing treatment to obtain the high-strength high-conductivity high-temperature-resistant copper-based composite rod wire.

2. The production method according to claim 1, characterized by, The copper powder is electrolytic copper, and the mesh number of the copper powder is 50-200 mesh; the particle size of the lanthanum hexaboride powder is 50-500 nm; and the rare earth oxide powder comprises one or more of cerium oxide, lanthanum oxide and yttrium oxide.

3. The preparation method according to claim 1, characterized in that, The plasma-assisted high-energy ball milling is carried out in an inert gas atmosphere, and the inert gas comprises argon and / or helium; The conditions of the plasma-assisted high-energy ball milling include that the diameter of the milling ball is 3-10 mm, the ball-to-material ratio is 10-30:1, the rotation speed is 400-1200 r / min, and the ball milling time is 12-60 h.

4. The method of claim 1, wherein, The pressure of the cold-pressing is 150-250 MPa; the reducing atmosphere comprises hydrogen, the sintering temperature is 850-950 DEG C, and the holding time is 1-2 h; and the relative density of the sintered blank is > 98%.

5. The preparation method according to claim 1, characterized in that, The temperature of the hot extrusion is 750-900 DEG C, and the holding time is 2-4 h; and the deformation of the hot extrusion is 80-95%.

6. The production method according to claim 1 or 5, characterized by, The temperature of the continuous extrusion is 350-500 DEG C; and the diameter of the wire blank is 2-12 mm.

7. The preparation method according to claim 1, characterized in that, The cold drawing is multi-pass cold drawing, and the area reduction of single-pass cold drawing is ≤ 20%; and the annealing temperature is 300-400 DEG C, and the holding time is 10 s-2 min.

8. The high-strength high-conductivity high-temperature-resistant copper-based composite rod wire prepared by the preparation method in any one of claims 1-7.

9. The high-strength, high-conductivity, high-temperature-resistant copper-based composite rod wire according to claim 8, characterized in that, The high-strength high-conductivity high-temperature-resistant copper-based composite rod wire has (111) texture; the average grain size of the copper matrix of the high-strength high-conductivity high-temperature-resistant copper-based composite rod wire is 100 nm-1 μm; and the proportion of low ΣCSL special grain boundaries is > 40%.

10. The high-strength, high-conductivity, high-temperature-resistant copper-based composite rod wire according to claim 9, characterized by, The proportion of (111) texture in the high-strength high-conductivity high-temperature-resistant copper-based composite rod wire is > 45%.

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