A method for preparing high-temperature resistant, high-strength, high-electrical and thermally conductive copper-niobium heterostructured nanocomposite microfilaments

Abstract

The present invention discloses a method for preparing high-temperature resistant, high-strength, high-electrical and thermally conductive copper-niobium heterostructured nanocomposite microfilaments. The method comprises the following steps: 1. winding copper and niobium strips and placing them in a copper sheath, subjecting them to homogeneous heating and isothermal hot extrusion deformation, and then subjecting them to multiple straight drawing, intermediate annealing, and coiling to obtain a copper-niobium composite wire; 2. bundling and assembling the copper-niobium composite wires and placing them in a copper sheath, subjecting them to homogeneous heating and isothermal hot extrusion deformation, and then subjecting them to multiple straight drawing, intermediate annealing, and coiling to obtain a copper-niobium multi-core composite round wire; 3. sequentially subjecting the copper-niobium multi-core composite round wire to multiple drawing and vacuum annealing. The present invention adopts an extreme plastic deformation process of copper and niobium winding composite combined with bundle drawing to obtain microfilaments with high tensile strength and good bending and tensile plasticity, excellent high-temperature thermal stability and high-temperature stress relaxation resistance, as well as excellent radiation resistance and excellent strong electrical matching. The process is simple, easy to control, and easy to achieve industrial mass production.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-temperature resistant, high-strength and high-conductivity composite copper wires, and specifically relates to a method for preparing high-temperature resistant, high-strength and high-conductivity and thermally conductive copper-niobium heterostructured nanocomposite microfilaments. Background Art

[0002] High-performance copper-based microwires are a key foundational material for the development of high-tech fields such as nuclear power, optoelectronics, microelectronics, aviation, and aerospace. They also provide a crucial support for the development of advanced equipment and information technology. They are primarily used as signal transmission lines for sensor systems within pressurized water reactors, as bonding wires for semiconductors and integrated circuits, high-end medical electron beams, intelligent robotic arm connectors, aerospace signal transmission lines, and internal transmission lines for flexible electronic devices. They require high-temperature thermal stability, radiation resistance, high strength, high electrical conductivity, and high thermal conductivity. Currently, the copper-based microwires available on the domestic market are primarily copper, copper-silver, and copper-tin wires produced through the melting-and-drawing process. However, copper-based microwires produced through the melting-and-drawing process struggle to achieve a single-crystal structure within their interiors, thereby achieving high electrical conductivity. Furthermore, both pure copper and copper alloy wires suffer from poor thermal stability and resistance to high-temperature stress relaxation, making them difficult to use in nuclear radiation service environments. Furthermore, the purification of the melt and the uniform distribution of alloying elements during the melting process are difficult to achieve and require significant human, material, and financial resources.

[0003] Relevant academic research and field applications have shown that the current copper-based micro-wire preparation process faces the problems of uneven composition and the contradiction between strong plasticity and strong electrical matching. For pure copper micro-wires, their recrystallization temperature is relatively low (≤300°C), which makes them difficult to use in high-temperature environments. In addition, based on the principle of work hardening, the strength of pure copper wires is improved by drawing deformation while sacrificing the excellent electrical conductivity of pure copper. For copper-silver and copper-tin micro-wires, the recrystallization temperatures of silver and tin are relatively low, at 150°C and -71°C respectively. Although the addition of copper and tin elements provides electrical conductivity and thermal conductivity of copper-based micro-wires, their high-temperature thermal stability is further reduced. Therefore, the copper and copper-based micro-wires currently produced on the market are difficult to simultaneously meet the performance requirements of high-temperature thermal stability, radiation resistance, high strength, high electrical conductivity and high thermal conductivity, and are difficult to be applied in extremely demanding service environments, especially in the fields of nuclear power, aviation and aerospace.

[0004] Therefore, it is urgent to design new copper-based composite material structures and components, propose new copper-based micro-wire processing and forming processes, and develop new high-performance copper-based micro-wires, so that the prepared copper-based micro-wires can have high-temperature thermal stability, radiation resistance, high strength, high electrical conductivity and high thermal conductivity. This is an important issue that needs to be solved urgently. It is of great significance for realizing applications in extremely complex service environments such as nuclear reactors and aerospace, and solving the problem of poor high-temperature service performance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and provide a method for preparing high-temperature resistant, high-strength, high-conductivity and high-thermal conductivity copper-niobium heterostructured nanocomposite microfilaments. This method uses an extreme plastic deformation process of copper and niobium winding combined with bundle drawing to obtain copper-niobium heterostructured nanocomposite microfilaments with an internal structure consisting of alternating single-crystal-like, strongly textured copper and niobium ribbon-like core wires of several to more than ten nanometers and a low-energy copper-niobium amorphous interface. The microfilaments have high tensile strength and good bending and stretching plasticity, excellent high-temperature thermal stability and high-temperature stress relaxation resistance, as well as excellent radiation resistance and strong electrical matching, solving the problem that existing copper and copper alloy microfilaments cannot combine high-temperature thermal stability, high strength, high electrical conductivity, high thermal conductivity, radiation resistance, and good bending plasticity.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing high-temperature resistant, high-strength, high-electrical and thermally conductive copper-niobium heterostructured nanocomposite microfilaments, characterized in that the method comprises the following steps:

[0007] Step 1: Alternately arrange copper strips and niobium strips of the same thickness in layers and wind them into a cylinder, which is then placed in an oxygen-free copper sheath to obtain a copper-niobium wound composite sheath. The copper-niobium wound composite sheath is vacuum degassed and vacuum welded to render the interior of the oxygen-free copper sheath vacuum and oxygen-free. Homogenous heating and isothermal hot extrusion deformation are then performed to form a weak connection between the internal copper layer and the niobium layer, thereby obtaining a copper-niobium composite extruded rod. The copper-niobium composite extruded rod is then subjected to multiple straight drawing passes, intermediate annealing, and coil drawing to obtain a copper-niobium composite wire with a hexagonal cross-section.

[0008] Step 2: The copper-niobium composite wire with a hexagonal cross-section obtained in Step 1 is used as a core wire for bundle assembly and then placed in an oxygen-free copper sheath to obtain a multi-core structure copper-niobium bundle assembly composite sheath, and the multi-core structure copper-niobium bundle assembly composite sheath is vacuum degassed and vacuum welded to make the interior of the oxygen-free copper sheath present a vacuum and oxygen-free state, and then homogenized heating and isothermal hot extrusion deformation are performed to form a weak connection between the inner core wire and the outer copper layer to obtain a copper-niobium multi-core composite extruded rod, and then the copper-niobium multi-core composite extruded rod is subjected to multiple passes of straight drawing, intermediate annealing, and coil drawing to obtain a copper-niobium multi-core composite round wire;

[0009] Step 3: After vacuum heat treatment, the copper-niobium multi-core composite round wire obtained in step 2 is subjected to a first multi-pass drawing and a first vacuum annealing treatment in sequence, and then a second multi-pass drawing and a second vacuum annealing treatment are sequentially performed, and then a third multi-pass drawing is sequentially performed, and after a final annealing heat treatment, a copper-niobium heterogeneous nanocomposite fine wire is obtained.

[0010] The present invention prepares a copper-niobium composite extruded rod by winding copper and niobium strips and placing them in a sheath, and then subjecting them to homogeneous heating and isothermal hot extrusion deformation to obtain a copper-niobium composite extruded rod, and then drawing to obtain a copper-niobium composite wire with a hexagonal cross-section; then, the rods are bundled and assembled and placed in a sheath, and then subjecting them to homogeneous heating and isothermal hot extrusion deformation to obtain a copper-niobium multi-core composite extruded rod, and then drawing to obtain a copper-niobium multi-core composite round wire; and then, after multiple drawing passes, intermediate vacuum annealing treatment and final annealing heat treatment, a copper-niobium heterogeneous nanocomposite microfilament is obtained.

[0011] First, because niobium has a high melting point (~2468°C) and a high recrystallization temperature (~1200°C), as well as high strength and good plasticity, and also has an elastic modulus similar to that of copper (copper's elastic modulus is approximately 129 GPa, and niobium's elastic modulus is approximately 105 GPa), the present invention, through an extreme plastic deformation process involving copper and niobium winding and bundle drawing, produces a copper and niobium ribbon-like core wire with an internal structure of several to ten nanometers, strongly textured and oriented, similar to a single crystal, and a low-energy copper-niobium amorphous interface. Considerable geometrically required dislocations are induced on both sides of the interface. This structure simultaneously induces nanoscale effects, gradient effects, and interface effects, acting simultaneously on the copper-niobium heterogeneous nanocomposite microfilaments. This ensures that the strength of the copper-niobium heterogeneous nanocomposite microfilaments continues to increase while maintaining good plasticity, ensuring continuous and sustained deformation. Ultimately, the copper-niobium heterogeneous nanocomposite microfilaments prepared by the present invention exhibit high tensile strength and good bending and tensile plasticity, resolving the contradiction between strength and plasticity in metals.

[0012] In addition, the composite of niobium with high-temperature thermal stability and copper with excellent plasticity improves the strong plasticity and high-temperature thermal stability of the copper-niobium heterostructured nanocomposite microfilaments. In particular, the parallel and alternating distribution of copper and niobium strip-shaped core wires of several nanometers to more than ten nanometers makes the copper-niobium heterostructured nanocomposite microfilaments have excellent high-temperature thermal stability and high-temperature stress relaxation resistance. The geometrically required dislocation structure introduced by the low-energy copper-niobium amorphous interface and the gradient strain on both sides of the interface makes the movement and annihilation of dislocations in the copper-niobium heterostructured nanocomposite microfilaments slow under irradiation, thus giving it radiation resistance. After extreme plastic deformation, the copper core wire structure of several nanometers to more than ten nanometers with strong texture orientation close to that of a single crystal has very few grain boundaries inside, which makes it have higher electrical conductivity and achieves excellent strong electrical matching. The alternating distribution of copper core wires and niobium filaments makes the copper-niobium heterostructured nanocomposite microfilaments have thermal conductivity similar to that of copper. Under the above-mentioned combined effects, the copper-niobium heterogeneous nanocomposite microfilaments of the present invention have the characteristics of high temperature resistance, high strength and high plasticity, high electrical conductivity and high thermal conductivity, which solves the problem that existing copper and copper alloy microfilaments cannot have high temperature thermal stability, high strength, high electrical conductivity, high thermal conductivity, radiation resistance and good bending plasticity.

[0013] The above-mentioned method for preparing high-temperature-resistant, high-strength, high-electrical and thermally conductive copper-niobium heterostructured nanocomposite microfilaments is characterized in that, in step 1, the thickness of the copper and niobium strips is each 0.1 mm to 0.5 mm, the diameter of the cylinder is Φ95 mm to Φ115 mm, the inner diameter of the oxygen-free copper sheath is 100 mm to 120 mm, and the wall thickness is 15 mm to 30 mm; and the diameter of the copper-niobium composite extruded rod is Φ30 mm to Φ50 mm. By controlling the thickness of the winding copper and niobium strips, the diameter of the cylinder, and the inner diameter and wall thickness of the oxygen-free copper sheath, the present invention effectively regulates the niobium content, ensuring excellent strength / plasticity and strength / electrical matching between the copper and niobium strips. This, in turn, controls the niobium content, the size and degree of distortion of the niobium core wire, and regulates the internal dislocation type, density, and motion behavior, as well as the stress / strain distribution and level, resulting in the prepared copper-niobium heterostructured nanocomposite microfilaments having optimal plastic deformation capacity and achieving optimal matching of strength, electrical conductivity, high-temperature resistance, and radiation resistance.

[0014] The above-mentioned method for preparing high-temperature resistant, high-strength, high-electrical and thermally conductive copper-niobium heterostructured nanocomposite microfilaments is characterized in that the mass proportion of niobium element in the copper-niobium winding assembly composite sheath in step 1 is 20% to 25%, the vacuum degassing temperature is 300°C to 400°C, the time is 3h to 6h, the vacuum welding adopts vacuum electron beam sealing welding, and the vacuum degree is 1×10 -5 Pa~1×10 -4 Pa, the welding passes are 5 times; the temperature of the homogenizing heating is 680℃~720℃, the time is 2.5h~3.5h, the temperature of the isothermal hot extrusion deformation is 680℃~720℃, and the extrusion ratio is 7~9.

[0015] The above-mentioned method for preparing high-temperature resistant, high-strength, high-electrical and thermally conductive copper-niobium heterostructured nanocomposite microfilaments is characterized in that the deformation rate of the multiple passes of direct drawing in step one is 15% to 17%, the intermediate annealing temperature is 670°C to 720°C, the time is 2h to 4h, and the deformation rate of the disk drawing is 12% to 15%; the width across the hexagonal cross section is 4.5mm to 3.6mm.

[0016] Typically, in step 2 of the present invention, the number of cores assembled by bundling the copper-niobium composite wires with hexagonal cross-sections as core wires is 800 to 1200.

[0017] The present invention controls the size and number of the core wires in the bundled assembly, regulates the copper / niobium interface density and the size of the copper and niobium core wires in the microfilaments, and further regulates the influence of scale effect and interface effect on the strength and plasticity of the copper-niobium heterostructured nanocomposite microfilaments, thereby achieving continuous deformation of high-strength copper-niobium heterostructured nanocomposite microfilaments with excellent bending plasticity after deformation.

[0018] The above-mentioned method for preparing high-temperature resistant, high-strength, high-electrical and thermally conductive copper-niobium heterostructured nanocomposite microfilaments is characterized in that the inner diameter of the oxygen-free copper sheath in step 2 is 100mm to 120mm, and the diameter of the copper-niobium multi-core composite extruded rod is Φ30mm to Φ50mm.

[0019] The above-mentioned method for preparing high-temperature resistant, high-strength, high-electrical and thermally conductive copper-niobium heterostructured nanocomposite microfilaments is characterized in that the temperature of the vacuum degassing in step 2 is 300°C to 400°C, and the time is 3h to 6h; the temperature of the homogenizing heating is 700°C to 720°C, and the time is 2.5h to 3.5h; the temperature of the isothermal hot extrusion deformation is 700°C to 720°C, and the extrusion ratio is 7 to 9.

[0020] The above-mentioned method for preparing high-temperature resistant, high-strength, high-electrical and thermally conductive copper-niobium heterostructured nanocomposite microfilaments is characterized in that the deformation rate of the multi-pass straight drawing in step 2 is 15% to 17%, the intermediate annealing temperature is 670°C to 720°C, the time is 2h to 4h, and the deformation rate of the coil drawing is 12% to 15%; the diameter of the copper-niobium multi-core composite round wire is Φ4mm to Φ12mm.

[0021] The above-mentioned method for preparing high-temperature resistant, high-strength, high-conductivity and high-thermal conductivity copper-niobium heterostructured nanocomposite microfilaments is characterized in that the temperature of the vacuum heat treatment in step three is 650°C to 700°C, and the time is 2.5h to 3.5h; the total deformation rate of the first multi-pass drawing is 85% to 90%, the pass deformation rate is 7% to 10%, and the temperature of the first vacuum annealing treatment is 650°C to 700°C, and the time is 1h; the total deformation rate of the second multi-pass drawing is 95% to 98%, the pass deformation rate is 6% to 8%, the temperature of the second vacuum annealing treatment is 550°C to 600°C, and the time is 1h; the total deformation rate of the third multi-pass drawing is 85% to 90%, the pass deformation rate is 12% to 24%, and the temperature of the final annealing heat treatment is 200°C to 400°C, and the time is 1h to 3h.

[0022] The above-mentioned method for preparing high-temperature resistant, high-strength, high-electrical and thermally conductive copper-niobium heterostructured nanocomposite microfilaments is characterized in that the diameter of the copper-niobium heterostructured nanocomposite microfilaments in step three is 0.05 mm to 0.15 mm.

[0023] The present invention controls the niobium content by controlling the dimensions of the copper strip, niobium strip, and copper sheath, as well as the number of filaments used in the bundled structure, thereby ensuring excellent strong-plastic and strong-electrical matching. By controlling the dimensions of the wires at each step, combined with controlling each step of the annealing and drawing process, continuous deformation of the wires is achieved, resulting in copper-niobium heterostructured nanocomposite microfilaments with excellent performance.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. The present invention adopts the processes of winding composite-degassing-welding-extrusion-drawing deformation, cluster composite-degassing-welding-extrusion-drawing deformation, annealing-drawing deformation-annealing-drawing deformation-annealing-drawing deformation-annealing to obtain copper-niobium heterostructured nanocomposite microfilaments having an internal structure of alternating single crystal-like, strongly textured copper and niobium ribbon-shaped core wires of several to more than ten nanometers and a low-energy copper-niobium amorphous interface. The copper-niobium heterostructured nanocomposite microfilaments have high tensile strength (tensile strength of 1000 MPa to 1500 MPa) and good bending and tensile plasticity (elongation at break of 2% to 5%), excellent high-temperature thermal stability and high-temperature stress relaxation resistance (softening temperature of above 700°C), as well as excellent radiation resistance and excellent strong electrical matching (electrical conductivity of above 50% IACS).

[0026] 2. Compared with the copper wire, copper-silver wire and copper-tin wire prepared by the existing melting-drawing process, the purification treatment of the melt and the control of the uniform distribution of alloy elements in the melting process are difficult, and the uneven distribution of the precipitated phase, the internal defects introduced in the smelting and solidification process, and the uneven residual stress introduced in the wire deformation process easily cause the wire to break during the wire drawing process, making it difficult to prepare continuous kilometer-long copper-based micro-wires. The present invention uses niobium strips with good plasticity and copper strips for winding and compounding, which can easily achieve continuous and uniform deformation of continuous copper-niobium heterogeneous micro-wires. After extreme plastic deformation, a disordered amorphous interface is formed at the copper-niobium interface, which greatly reduces local stress and effectively solves the problem of residual stress inside the copper-niobium heterogeneous micro-wires causing their difficulty in deformation. At the same time, the preparation process of the present invention only involves extrusion, drawing and heat treatment, which is simpler and easier to control than melting-drawing, and the preparation process is safe and easy to operate.

[0027] 3. The extreme plastic deformation process of the present invention is simple and easy to implement in industrial mass production. At the same time, by stacking and winding copper strips and niobium strips to form a copper-niobium composite wire bundle assembly and then subjecting it to extreme plastic deformation, it is easy to achieve uniformity of the internal structure of the copper-niobium composite microfilaments and obtain core wires with a scale of more than ten nanometers to several nanometers. This solves the problems of structural segregation, uneven reinforcement phase scale, and uneven composition in the current preparation process of elastic copper-based microfilaments using smelting and powder metallurgy methods, and ensures the uniformity of the mechanical properties of the copper-niobium heterogeneous nanocomposite microfilaments. In addition, the niobium core wire structure with a scale of more than ten nanometers to several nanometers and the low-energy copper-niobium amorphous interface with a scale of several nanometers inside the copper-niobium heterogeneous nanocomposite microfilaments increase the recrystallization temperature of the microfilaments, giving them high temperature thermal stability and achieving their high temperature resistance. The alternating distribution of copper and niobium inside the microfilaments ensures that the thermal conductivity of the copper-niobium heterogeneous nanocomposite microfilaments is similar to that of pure copper, filling the technical effect gap that cannot be achieved by the smelting-drawing process.

[0028] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 These are some actual products with different diameters and corresponding measurement images during the preparation of copper-niobium heterogeneous nanocomposite microfilaments in Example 2 of the present invention.

[0030] Figure 2 This is a microstructure diagram of the copper-niobium heterogeneous nanocomposite microwires prepared in Example 2 of the present invention.

[0031] Figure 3 These are SEM images of the spheroidization of the internal niobium nanocore wires of the copper-niobium heterostructured nanocomposite microwires prepared in Example 2 of the present invention at room temperature (20°C) and when heated to 700°C, 800°C, and 900°C.

[0032] Figure 4 This is a tensile stress-strain curve of the copper-niobium heterogeneous nanocomposite microfilaments prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0033] Example 1

[0034] This embodiment includes the following steps:

[0035] Step 1: Copper strips and niobium strips with a thickness of 0.5 mm are alternately layered and wound into a cylinder with a diameter of Φ95 mm, and then placed in an oxygen-free copper sheath with an inner diameter of 100 mm and a wall thickness of 30 mm to obtain a copper-niobium wound composite sheath with a niobium element mass ratio of 25%. The copper-niobium wound composite sheath is vacuum degassed at a temperature of 300°C for 3 hours, and vacuum electron beam sealing is performed with a vacuum degree of 1×10 -5 Pa~1×10 -4 Pa, with 5 welding passes, so that the interior of the oxygen-free copper sheath is in a vacuum and oxygen-free state, followed by homogenization heating at a temperature of 680°C for 2.5 hours and isothermal hot extrusion deformation at a temperature of 680°C and an extrusion ratio of 7, so that the internal copper layer and the niobium layer form a weak connection, to obtain a copper-niobium composite extruded rod with a diameter of Φ30 mm. The copper-niobium composite extruded rod is then subjected to multi-pass straight drawing with a pass deformation rate of 15%, intermediate annealing at a temperature of 670°C for 2 hours, and coil drawing with a pass deformation rate of 12%, to obtain a copper-niobium composite wire with a hexagonal cross-section and a flat width of 3.6 mm.

[0036] Step 2: 1200 copper-niobium composite wires with a hexagonal cross-section obtained in step 1 are bundled and assembled as core wires and placed in an oxygen-free copper sheath with an inner diameter of 100 mm to obtain a multi-core copper-niobium bundled assembled composite sheath. The multi-core copper-niobium bundled assembled composite sheath is vacuum degassed at a temperature of 300° C. for 3 hours, and vacuum welded to make the interior of the oxygen-free copper sheath present a vacuum and oxygen-free state. Homogenizing heating at a temperature of 700° C. for 2.5 hours and isothermal hot extrusion deformation at a temperature of 700° C. and an extrusion ratio of 7 are then performed to form a weak connection between the outer copper layer of the inner core wire, thereby obtaining a copper-niobium multi-core composite extruded rod with a diameter of Φ30 mm. The copper-niobium multi-core composite extruded rod is then subjected to multi-pass straight drawing with a pass deformation rate of 15%, intermediate annealing at a temperature of 670° C. for 2 hours, and coil drawing with a pass deformation rate of 12%, to obtain a copper-niobium multi-core composite round wire with a diameter of Φ4 mm.

[0037] Step 3. The copper-niobium multi-core composite round wire obtained in step 2 is subjected to vacuum heat treatment at a temperature of 650°C for 2.5 hours, and then subjected to a first multi-pass drawing with a total deformation rate of 85% and a pass deformation rate of 7%, a first vacuum annealing treatment at a temperature of 650°C for 1 hour, followed by a second multi-pass drawing with a total deformation rate of 95% and a pass deformation rate of 6%, a second vacuum annealing treatment at a temperature of 550°C for 1 hour, and then a third multi-pass drawing with a total deformation rate of 85% and a pass deformation rate of 12%. After a final annealing heat treatment at a temperature of 200°C for 1 hour, a copper-niobium heterogeneous nanocomposite microwire with a wire diameter of 0.05 mm is obtained.

[0038] Example 2

[0039] This embodiment includes the following steps:

[0040] Step 1: Copper strips and niobium strips with a thickness of 0.25 mm are alternately layered and wound into a cylinder with a diameter of 100 mm, and then placed in an oxygen-free copper sheath with an inner diameter of 110 mm and a wall thickness of 25 mm to obtain a copper-niobium wound composite sheath with a niobium element mass ratio of 22.5%. The copper-niobium wound composite sheath is vacuum degassed at a temperature of 350°C for 4.5 hours, and vacuum electron beam sealing is performed with a vacuum degree of 1×10 -5 Pa~1×10 -4Pa, with 5 welding passes to achieve a vacuum and oxygen-free state inside the oxygen-free copper sheath, followed by homogenous heating at a temperature of 700°C for 3.5 hours and isothermal hot extrusion deformation at a temperature of 700°C and an extrusion ratio of 8 to form a weak connection between the internal copper layer and the niobium layer, thereby obtaining a copper-niobium composite extruded rod with a diameter of Φ45 mm. The copper-niobium composite extruded rod is then subjected to multi-pass straight drawing with a pass deformation rate of 16%, intermediate annealing at a temperature of 700°C for 3 hours, and coil drawing with a pass deformation rate of 13.5%, thereby obtaining a copper-niobium composite wire with a hexagonal cross-section and a flat width of 4 mm.

[0041] Step 2: 1000 copper-niobium composite wires with a hexagonal cross-section obtained in step 1 are bundled and assembled as core wires and placed in an oxygen-free copper sheath with an inner diameter of 110 mm to obtain a multi-core copper-niobium bundled assembled composite sheath. The multi-core copper-niobium bundled assembled composite sheath is vacuum degassed at a temperature of 350° C. for 4.5 hours, and vacuum welded to make the interior of the oxygen-free copper sheath present a vacuum and oxygen-free state. Homogenizing heating at a temperature of 710° C. for 3 hours and isothermal hot extrusion deformation at a temperature of 710° C. and an extrusion ratio of 8 are then performed to form a weak connection between the outer copper layer of the inner core wire, thereby obtaining a copper-niobium multi-core composite extruded rod with a diameter of Φ40 mm. The copper-niobium multi-core composite extruded rod is then subjected to multi-pass straight drawing with a pass deformation rate of 16%, intermediate annealing at a temperature of 700° C. for 3 hours, and coil drawing with a pass deformation rate of 13.5%, to obtain a copper-niobium multi-core composite round wire with a diameter of Φ5.5 mm.

[0042] Step 3. The copper-niobium multi-core composite round wire obtained in step 2 is subjected to vacuum heat treatment at a temperature of 680°C for 3 hours, and then subjected to a first multi-pass drawing with a total deformation rate of 87% and a pass deformation rate of 8%, a first vacuum annealing treatment at a temperature of 680°C for 1 hour, followed by a second multi-pass drawing with a total deformation rate of 96% and a pass deformation rate of 7%, a second vacuum annealing treatment at a temperature of 580°C for 1 hour, and then a third multi-pass drawing with a total deformation rate of 87% and a pass deformation rate of 18%. After a final annealing heat treatment at a temperature of 250°C for 1 hour, a copper-niobium heterogeneous nanocomposite microwire with a wire diameter of 0.113 mm is obtained.

[0043] Figure 1 These are some actual products with different diameters and corresponding measurement images during the preparation process of copper-niobium heterogeneous nanocomposite microwires in this embodiment.

[0044] Figure 2Figures (a) to (d) show the microstructure of the copper-niobium heterostructured nanocomposite microfilaments prepared in this embodiment, wherein Figure (a) is a TEM bright-field phase image of the copper-niobium heterostructured nanocomposite microfilaments, Figure (b) is a high-resolution image magnified within the elliptical frame in Figure (a), Figure (c) is a distribution diagram of the niobium lamellar core wires in the copper-niobium heterostructured nanocomposite microfilaments, and Figure (d) is an energy spectrum diagram of the copper-niobium heterostructured nanocomposite microfilaments. As can be seen from Figures (a) to (d), the sizes of the copper and niobium core wires in the copper-niobium heterostructured nanocomposite microfilaments are about a dozen nanometers, and the size of the copper-niobium interface is less than ten nanometers. A dragon-ridge-like pattern appears at the copper-niobium interface in Figure (b), indicating that the interface absorbs considerable geometric dislocations within the copper and niobium core wires, greatly reducing the distortion and dislocations of the copper and niobium core wires, and maintaining good thermal stability at high temperatures.

[0045] Figure 3 The SEM images of the spheroidization of the internal niobium nanocore wires of the copper-niobium heterogeneous nanocomposite microfilaments prepared in this example at room temperature (20°C) and heated to 700°C, 800°C and 900°C are shown. Figure 3 It can be seen that when the copper-niobium heterostructured nanocomposite microwires are heated to 700℃, the niobium nanowires begin to spheroidize, and the spheroidization phenomenon is not obvious; when the copper-niobium heterostructured nanocomposite microwires are heated to 800℃, the niobium nanowires begin to spheroidize obviously; when the copper-niobium heterostructured nanocomposite microwires are heated to 800℃, the niobium nanowires are completely spheroidized; it can be seen that the copper-niobium heterostructured nanocomposite microwires have good thermal resistance and their softening resistance temperature is above 700℃.

[0046] Figure 4 The tensile stress-strain curve of the copper-niobium heterogeneous nanocomposite microfilament prepared in this embodiment is shown in FIG. Figure 4 It can be seen that the tensile strength of the copper-niobium heterostructured nanocomposite microfilaments is greater than 1400 MPa, and the elongation at break is greater than 2.5%.

[0047] After testing, the thermal diffusivity and thermal conductivity of the copper-niobium heterogeneous nanocomposite microfilaments prepared in this embodiment are shown in Table 1 below.

[0048] Table 1

[0049]

[0050] As can be seen from Table 1, at different service temperatures, the thermal conductivity of the Cu-Nb heterogeneous nanocomposite microfilaments is approximately between 360 W / (m·K) and 370 W / (m·K), which is close to the thermal conductivity of pure copper, 400 W / (m·K). This indicates that the addition of the thermally stable niobium core wire has a relatively small weakening effect on the thermal conductivity of the Cu-Nb heterogeneous nanocomposite microfilaments, and the Cu-Nb heterogeneous nanocomposite microfilaments still have excellent thermal conductivity.

[0051] Example 3

[0052] This embodiment includes the following steps:

[0053] Step 1: Copper strips and niobium strips with a thickness of 0.1 mm are alternately layered and wound into a cylinder with a diameter of Φ115 mm, and then placed in an oxygen-free copper sheath with an inner diameter of 120 mm and a wall thickness of 15 mm to obtain a copper-niobium wound composite sheath with a niobium element mass ratio of 20%. The copper-niobium wound composite sheath is vacuum degassed at a temperature of 400°C for 6 hours, and vacuum electron beam sealing is performed with a vacuum degree of 1×10 -5 Pa~1×10 -4 Pa, with 5 welding passes, so that the interior of the oxygen-free copper sheath is in a vacuum and oxygen-free state, followed by homogenous heating at a temperature of 720°C for 3.5 hours and isothermal hot extrusion deformation at a temperature of 720°C and an extrusion ratio of 9, so that the internal copper layer and the niobium layer form a weak connection, thereby obtaining a copper-niobium composite extruded rod with a diameter of Φ50 mm. The copper-niobium composite extruded rod is then subjected to multi-pass straight drawing with a pass deformation rate of 17%, intermediate annealing at a temperature of 720°C for 4 hours, and coil drawing with a pass deformation rate of 15%, thereby obtaining a copper-niobium composite wire with a hexagonal cross-section and a flat width of 4.5 mm.

[0054] Step 2: 800 copper-niobium composite wires with a hexagonal cross-section obtained in step 1 are bundled and assembled as core wires and placed in an oxygen-free copper sheath with an inner diameter of 120 mm to obtain a multi-core copper-niobium bundled assembled composite sheath. The multi-core copper-niobium bundled assembled composite sheath is vacuum degassed at a temperature of 400° C. for 6 hours, and vacuum welded to make the interior of the oxygen-free copper sheath present a vacuum and oxygen-free state. Homogenizing heating at a temperature of 720° C. for 3.5 hours and isothermal hot extrusion deformation at a temperature of 720° C. and an extrusion ratio of 9 are then performed to form a weak connection between the outer copper layer of the inner core wire, thereby obtaining a copper-niobium multi-core composite extruded rod with a diameter of Φ50 mm. The copper-niobium multi-core composite extruded rod is then subjected to multi-pass straight drawing with a pass deformation rate of 17%, intermediate annealing at a temperature of 720° C. for 4 hours, and coil drawing with a pass deformation rate of 15%, to obtain a copper-niobium multi-core composite round wire with a diameter of Φ12 mm.

[0055] Step 3. The copper-niobium multi-core composite round wire obtained in step 2 is subjected to vacuum heat treatment at a temperature of 700°C for 3.5 hours, and then subjected to a first multi-pass drawing with a total deformation rate of 90% and a pass deformation rate of 10%, a first vacuum annealing treatment at a temperature of 700°C for 1 hour, followed by a second multi-pass drawing with a total deformation rate of 98% and a pass deformation rate of 8%, a second vacuum annealing treatment at a temperature of 600°C for 1 hour, and then a third multi-pass drawing with a total deformation rate of 90% and a pass deformation rate of 24%. After a final annealing heat treatment at a temperature of 400°C for 3 hours, a copper-niobium heterogeneous nanocomposite microwire with a wire diameter of 0.15 mm is obtained.

[0056] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the essence of the invention technology shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing high-temperature resistant, high-strength, high-electrical and thermally conductive copper-niobium heterogeneous nanocomposite microfilaments, characterized in that: The method comprises the following steps: Step 1: Alternately arrange copper strips and niobium strips of the same thickness in layers and wind them into a cylinder, which is then placed in an oxygen-free copper sheath to obtain a copper-niobium wound composite sheath. The copper-niobium wound composite sheath is vacuum degassed and vacuum welded to render the interior of the oxygen-free copper sheath vacuum and oxygen-free. Homogenous heating and isothermal hot extrusion deformation are then performed to form a weak connection between the internal copper layer and the niobium layer, thereby obtaining a copper-niobium composite extruded rod. The copper-niobium composite extruded rod is then subjected to multiple straight drawing passes, intermediate annealing, and coil drawing to obtain a copper-niobium composite wire with a hexagonal cross-section. The thickness of the copper strip and the niobium strip are both 0.1mm~0.5mm, and the diameter of the cylinder is 95mm~ 115mm, the inner diameter of the oxygen-free copper sheath is 100mm~120mm, and the wall thickness is 15mm~30mm; the diameter of the copper-niobium composite extruded rod is 30mm~ 50mm; The mass proportion of niobium element in the copper-niobium winding assembly composite sheath is 20% to 25%. The temperature of the vacuum degassing is 300°C to 400°C, and the time is 3h to 6h. The vacuum welding adopts vacuum electron beam sealing welding, and the vacuum degree is 1×10 -5 Pa~1×10 - 4 Pa, the welding passes are 5; the temperature of the homogenization heating is 680°C~720°C, the time is 2.5h~3.5h, the temperature of the isothermal hot extrusion deformation is 680°C~720°C, and the extrusion ratio is 7~9; Step 2: The copper-niobium composite wire with a hexagonal cross-section obtained in Step 1 is used as a core wire for bundle assembly and then placed in an oxygen-free copper sheath to obtain a multi-core structure copper-niobium bundle assembled composite sheath; the multi-core structure copper-niobium bundle assembled composite sheath is vacuum degassed and vacuum welded to make the interior of the oxygen-free copper sheath present a vacuum and oxygen-free state; then, homogenous heating and isothermal hot extrusion deformation are performed to form a weak connection between the internal core wire and the outer copper layer to obtain a copper-niobium multi-core composite extruded rod; and then, the copper-niobium multi-core composite extruded rod is subjected to multiple passes of straight drawing, intermediate annealing, and coil drawing to obtain a copper-niobium multi-core composite round wire; Step 3: After vacuum heat treatment, the copper-niobium multi-core composite round wire obtained in step 2 is subjected to a first multi-pass drawing and a first vacuum annealing treatment in sequence, and then a second multi-pass drawing and a second vacuum annealing treatment are sequentially performed. Then, a third multi-pass drawing is sequentially performed, and after final annealing heat treatment, a copper-niobium heterogeneous nanocomposite microfilament is obtained; the copper-niobium heterogeneous nanocomposite microfilament has a wire diameter of 0.05 mm to 0.15 mm.

2. The method for preparing a high-temperature resistant, high-strength, high-electrical and thermally conductive copper-niobium heterostructured nanocomposite microfilament according to claim 1, characterized in that: The deformation rate of the multi-pass straight drawing in step 1 is 15% to 17%, the intermediate annealing temperature is 670° C. to 720° C., the time is 2 h to 4 h, the deformation rate of the disk drawing is 12% to 15%; the width across the hexagonal cross section is 4.5 mm to 3.6 mm.

3. The method for preparing high-temperature resistant, high-strength, high-electrical and thermally conductive copper-niobium heterostructured nanocomposite microfilaments according to claim 1, characterized in that: The inner diameter of the oxygen-free copper sheath in step 2 is 100 mm to 120 mm, and the diameter of the copper-niobium multi-core composite extruded rod is 30mm~ 50mm.

4. The method for preparing high-temperature resistant, high-strength, high-electrical and thermally conductive copper-niobium heterostructured nanocomposite microfilaments according to claim 1, characterized in that: The temperature of the vacuum degassing in step 2 is 300°C~400°C, and the time is 3h~6h; the temperature of the homogenizing heating is 700°C~720°C, and the time is 2.5h~3.5h; the temperature of the isothermal hot extrusion deformation is 700°C~720°C, and the extrusion ratio is 7~9.

5. The method for preparing high-temperature resistant, high-strength, high-electrical and thermally conductive copper-niobium heterostructured nanocomposite microfilaments according to claim 1, characterized in that: The deformation rate of the multi-pass straight drawing in step 2 is 15% to 17%, the intermediate annealing temperature is 670°C to 720°C, the time is 2h to 4h, and the deformation rate of the coil drawing is 12% to 15%; the diameter of the copper-niobium multi-core composite round wire is 4mm~ 12mm.

6. The method for preparing high-temperature resistant, high-strength, high-electrical and thermally conductive copper-niobium heterostructured nanocomposite microfilaments according to claim 1, characterized in that: The temperature of the vacuum heat treatment in step 3 is 650°C~700°C, and the time is 2.5h~3.5h; the total deformation rate of the first multi-pass drawing is 85%~90%, the pass deformation rate is 7%~10%, and the temperature of the first vacuum annealing treatment is 650°C~700°C, and the time is 1h; the total deformation rate of the second multi-pass drawing is 95%~98%, the pass deformation rate is 6%~8%, and the temperature of the second vacuum annealing treatment is 550°C~600°C, and the time is 1h; the total deformation rate of the third multi-pass drawing is 85%~90%, the pass deformation rate is 12%~24%, and the temperature of the final annealing heat treatment is 200°C~400°C, and the time is 1h~3h.

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