Ultrahigh-strength nano layered copper-iron composite material and preparation method thereof

Abstract

The invention discloses an ultrahigh-strength nanometer layered copper-iron composite material and a preparation method thereof.The material is of a sandwich-like structure, the sandwich-like structure is composed of continuous iron phase nanometer layers and continuous copper phase nanometer layers which are alternately distributed, interlayer interfaces are mechanically combined, and a dislocation strengthening effect exists. The preparation method comprises the following steps: weighing iron powder and copper powder according to a designed ratio, carrying out ball milling and mixing, and carrying out primary cold press molding and vacuum hot pressed sintering to obtain an ingot-shaped copper-iron blank; the ingot-shaped copper-iron blank is subjected to hot extrusion forming, and a strip-shaped composite copper-iron material is obtained; the strip-shaped composite copper-iron material is obtained through accumulative cold rolling and pack rolling after stress relief annealing. The powder metallurgy method is adopted, the influence of composition segregation of a high-iron-content material on the performance of the material is avoided, the nanometer layered copper-iron composite material is obtained in combination with accumulated cold rolling and ply rolling, and the strength and toughness of the material are greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metal-based composite materials, and in particular relates to the preparation of an ultra-high-strength nano-layered copper-iron composite material. Background Art

[0002] Copper-iron alloy is a kind of insoluble solid solution alloy. Even at a high temperature of 1094℃, the solid solubility is less than 5%. Copper-iron alloy with high iron content can be regarded as a metal-based composite material. Pure copper has high electrical and thermal conductivity and excellent ductility, but lacks strength. Adding iron to copper can effectively improve the strength of copper alloys. Iron is cheaper than other metals, and the cost of preparing alloys is low. Copper-iron composite materials have great application prospects in electronic communications, transportation rails, aerospace, national defense and military fields due to their high electrical and thermal conductivity, good plasticity and excellent electromagnetic shielding properties.

[0003] At present, the preparation method of copper-iron composite materials with high iron content is not mature yet, and has the following problems:

[0004] (1) Copper and iron are completely immiscible at room temperature. Even at a high temperature of 1094°C, the solid solubility is less than 5%. Therefore, when preparing copper-iron alloy, the iron phase with a higher melting point will solidify earlier than the copper phase, forming a coarse iron phase, which will seriously affect the strength and conductivity of the material and seriously reduce its performance.

[0005] (2) The higher the iron content, the more likely it is that composition segregation will occur, and there will be large composition deviations in the center and edge areas of the sample. Copper-iron alloy is a typical peritectic system. There are metastable immiscible gaps in the liquid state. Below the liquidus line, the supercooled solution will undergo liquid phase separation. The originally uniform solution will separate into two liquid phases, making the composition of each part of the material very uneven, seriously affecting the performance of the material. It has been applied.

[0006] At present, there are mainly the following methods for preparing copper-iron alloys:

[0007] Traditional casting method: melt copper and iron blocks in a smelting furnace in turn, cast them into ingots by casting, semi-continuous casting, or horizontal continuous casting, and then improve the performance through cold or hot processing and aging. The traditional casting method is not suitable for the manufacture of copper-iron composite materials with high iron content, and it is easy to cause component segregation.

[0008] Deformation in-situ composite method: Copper and iron are melted using an electric arc furnace or an induction furnace, and after cooling, they are solidified into a preliminary alloy. Heat treatment is carried out to promote the homogenization of the alloy, followed by hot working or cold working to introduce stress into the alloy, promoting the plastic deformation of the material, and causing phase transformation or inducing new microstructure evolution under an external stress. Finally, heat treatment is performed to optimize the mechanical properties. This method can control the microstructure of the alloy through deformation and phase transformation, improving its mechanical properties. However, the complexity, crack problems, difficulty in microstructure control, and equipment and time requirements during the process are all challenges that need to be overcome.

[0009] In summary, due to the liquid phase separation phenomenon, traditional casting methods cannot be used to prepare copper-iron composites with high iron content; the deformation in-situ composite method has complex processes, crack problems, difficult microstructure control, and strict requirements for equipment and time. Summary of the Invention

[0010] Aiming at the above problems that occur in the preparation of copper-iron composites with high iron content in the prior art, the first object of the present invention is to provide a super-high-strength nano-layered copper-iron composite material. The special distribution form of the iron phase layer and the copper phase layer and the interlayer interface dislocation strengthening effect in this composite material endow the composite material with a high electrical conductivity, while also having excellent strength and toughness.

[0011] The second object of the present invention is to provide a preparation method for a super-high-strength nano-layered copper-iron composite material. By using the powder metallurgy method, the influence of composition segregation on the material properties of high-iron-content materials is avoided, and a nano-layered copper-iron composite material is obtained by combining accumulative cold rolling and overlay rolling, greatly improving the strength and toughness of the material.

[0012] To achieve the above technical objectives, the present invention provides a super-high-strength nano-layered copper-iron composite material, which has a sandwich-like structure. The sandwich-like structure is composed of continuously alternating iron phase nano-layers and copper phase nano-layers, and the interlayer interface is mechanically bonded, with a dislocation strengthening effect.

[0013] In the composite material of the present invention, the continuously distributed continuous iron phase nano-layers and continuous copper phase nano-layers form a large number of nano-scale heterogeneous interfaces through mechanically bonded interfaces (no solid solution is formed between copper and iron at the interfaces, and the lattice distortion is small). These interfaces serve as effective barriers to dislocation movement when the material is stressed. During the process of dislocation slip, when the dislocation encounters the grain boundary, due to the orientation difference, significant pile-up occurs at the interface, significantly enhancing the strength of the material. At the same time, the high strength of the iron phase and the excellent ductility of the copper phase form a complementarity at the nano-scale: the iron layer enhances the overall load-bearing capacity by restricting the plastic deformation region, while the copper layer absorbs energy through its own plastic deformation and delays crack propagation, thereby enhancing toughness. In addition, the copper and iron phases are arranged in parallel layers along the rolling direction, similar to a "sandwich" structure. The iron layer is thicker and continuous, while the copper layer is thinner and dispersed. Moreover, the nano-layered structure itself strengthens the deflection or bifurcation of the crack path during crack propagation by refining the grain size, further enhancing the fracture toughness and the life of the material under cyclic loading. Finally, the simultaneous improvement of the strength and toughness of the composite material of the present invention is achieved. In addition, the overall "sandwich-like" structure presented by the composite material of the present invention, and the layered arrangement along the rolling direction can optimize the current path, reduce the transverse grain boundary scattering, and improve the longitudinal electrical conductivity. At the same time, the copper phase in the copper phase nano-layer remains continuously distributed, providing a low-resistance path for electrons and reducing the interface resistance. The lattice distortion at the interface is small (non-solid solution), reducing electron scattering; at the same time, the nano-layered structure shortens the mean free path of electrons and reduces the resistivity, thus ensuring the overall electrical conductivity performance of the composite material.

[0014] As a preferred solution, the continuous iron phase nano-layer is a single layer or multiple layers.

[0015] As a preferred solution, the single-layer thickness of the continuous iron phase nano-layer is 100 - 200 nm, and the thickness of the copper phase nano-layer is 10 - 100 nm; the total thickness of the nano-layered copper-iron composite material is 1 - 2 mm. In the present invention, if the single-layer thickness of the continuous iron phase nano-layer is too large, it will lead to an increase in the brittleness of the material and a decrease in toughness. And the iron phase has poor ductility, and too thick an iron layer will hinder the plastic deformation ability of the copper phase, making the crack more likely to expand. While a relatively thin single-layer thickness of the continuous iron phase nano-layer cannot play a role in strengthening the overall tensile strength. And too small a thickness of the copper phase nano-layer is not conducive to improving the electrical conductivity of the composite material, while too large a thickness will reduce the proportion of the iron layer, weaken the overall strength, and cause plastic collapse of the material under high pressure.

[0016] As a preferred solution, the mass percentage content of iron in the nano-layered copper-iron composite material is 40% - 60%, and the balance is copper. The copper-iron composite material of the present invention belongs to a high-iron-content material, which is beneficial to improving the strength of the composite material.

[0017] The present invention also provides a method for preparing an ultra-high-strength nano-layered copper-iron composite material. In this method, iron powder and copper powder are weighed according to a designed ratio, ball-milled and mixed, and then preliminarily cold-pressed and vacuum hot-pressed and sintered to obtain an ingot-shaped copper-iron blank; the ingot-shaped copper-iron blank is hot-extruded to obtain a strip-shaped composite copper-iron material; the strip-shaped composite copper-iron material is subjected to stress-relieving annealing and then accumulative cold-rolling and stacking rolling to obtain the desired product; the temperature of the vacuum hot-pressing and sintering is 900-1000 °C.

[0018] The key to the preparation method of the present invention lies in adopting the powder metallurgy method combined with the solid-state processing path, which avoids the problem of composition segregation caused by liquid-phase separation in the traditional casting method. First, in the present invention, copper powder and iron powder are fully mixed by high-energy ball milling, and oxidation is prevented under argon protection to ensure composition uniformity; during vacuum hot-pressing and sintering, copper and iron do not melt and undergo phase transformation, and copper and iron still maintain their respective independent phases, avoiding segregation caused by liquid-phase separation; at the same time, high pressure and high temperature promote inter-particle diffusion bonding, reducing pores and impurities. Then, hot extrusion is used to densify the material, initially forming a strip-shaped structure along the extrusion direction, and at this time, the grains are partially refined; at this time, annealing can release internal stress, avoid cracks, and at the same time, partial recrystallization refines the grains. Finally, during the process of accumulative stacking rolling, shear stress is introduced during each cold rolling, causing the copper-iron phases to be elongated and broken along the rolling direction, and the copper-iron phases are forced to be arranged in layers, ultimately forming alternating nano-layers. At the same time, the preparation method of the present invention can reduce oxidation impurities, further reduce the resistance of the composite material, and improve the electrical conductivity of the composite material.

[0019] It should be noted that during the processes of hot extrusion and accumulative cold-rolling and stacking rolling of the present invention, they are all carried out in the solid state, and the microstructure is regulated through mechanical deformation rather than in a molten state, completely avoiding the risk of composition segregation caused by liquid separation.

[0020] When the temperature of the vacuum hot-pressing and sintering of the present invention is too high, the copper phase will melt, resulting in the phenomenon of composition segregation. If the sintering temperature is too low, the sintering density is insufficient, there are pores, and the mechanical properties of the material are reduced.

[0021] As a preferred solution, the iron powder is high-purity water atomized iron powder with a purity ≥ 99.9%, and the particle size is 20-50 μm; the copper powder is high-purity water atomized copper powder with a purity ≥ 99.9%, and the particle size is 20-50 μm.

[0022] As a preferred solution, the process of ball milling is as follows: evacuate the ball milling tank, then introduce argon for 30 s, then evacuate and introduce argon again, repeat 4-6 times, and then ball mill for 8-16 h. Further, multiple ball milling tanks can be used for ball milling during the ball milling process to make it more uniform.

[0023] The present invention selects high-purity water atomized copper powder and high-purity water atomized iron powder, which can effectively improve the compactness of powder pressing, reduce the gas content, and prevent oxidation of copper and iron during ball milling in an argon atmosphere.

[0024] As a preferred solution, the temperature of the preliminary cold pressing and forming is room temperature, and the pressure is 5 - 10 MPa.

[0025] As a preferred solution, the conditions for vacuum hot pressing and sintering are: the vacuum degree is 0.01 - 0.02 MPa, the pressure is 10 - 30 MPa, and the sintering time is 30 - 120 min.

[0026] First, perform preliminary cold pressing and forming at room temperature to make the powder have a certain shape stability and compactness. Then, in a high-vacuum environment, perform hot pressing and sintering to reduce oxidation and gas pollution. The pressure is between 10 - 30 MPa, and applying pressure helps to improve the compactness and mechanical strength of the material. The sintering time should not be too long to avoid over-sintering and affecting the final performance of the material.

[0027] As a preferred solution, the process of hot extrusion forming is as follows: Before extrusion, put the ingot-shaped copper-iron billet into a vacuum heating furnace and keep it at a temperature of 950 - 1000 °C for 0.5 - 1 h; put the extrusion nozzle into a heating furnace with an actual temperature of 400 - 600 °C and keep it for 0.5 - 1 h, and then perform hot extrusion to obtain a strip-shaped composite material. Further, the width of the strip-shaped composite material is 40 - 60 mm, the extrusion ratio is 22 - 26, and further, the extrusion speed is 1.5 - 2.5 mm / s.

[0028] Under the hot extrusion temperature of the present invention, it is beneficial for extrusion deformation, and the grains will not grow too large; within the extrusion ratio range of the present invention, the grains can be effectively refined.

[0029] As a preferred solution, the temperature of stress relief annealing is 300 - 500 °C, and the annealing time is 0.5 - 1 h. Although dislocation pinning will increase the strength of the material, a large amount of dislocation pile-up will cause stress concentration and lead to material fracture. However, through stress relief annealing treatment in the present invention, some dislocation defects can be reduced, a part of dislocations can be released, thereby improving the plasticity of the material, reducing internal stress, and making the material uniform.

[0030] As a preferred solution, the number of times of cumulative cold rolling and laminating is 4 - 6 times, and the total deformation amount is 60% - 90%. Through cumulative cold rolling and laminating in the present invention, excessive damage of the material during single rolling can be prevented, residual stress can be released to avoid cracks in the material during subsequent processing, and the grains can be refined, increasing the strength and toughness of the material. And when the number of times of cumulative cold rolling and laminating is too small: the layered structure is not fully refined, the dislocation density is insufficient, and the strengthening effect is weak; while when the number of times is too large, residual stress accumulates, cracks are easily caused, and the toughness is reduced.

[0031] As a preferred solution, during the process of cumulative cold rolling and lamination, the interlayer direction of the strip-shaped composite copper-iron material during single cold rolling needs to be consistent with the rolling direction. The inventor found that when the interlayer direction is inconsistent with the rolling direction, it will not only lead to uneven structure of the composite material, but also result in excessive dislocation structures in the composite material.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) By selecting iron powder and copper powder and pre-treating the powder before ball milling, the present invention can greatly reduce the oxygen content, reduce the oxidation reaction during sintering, and reduce the porosity to obtain a sintered body with a tight combination.

[0034] (2) Through vacuum sintering, the present invention can effectively reduce impurities, reduce the oxidation reaction during sintering, obtain a relatively uniform structure, refine grains, and obtain better material properties.

[0035] (3) Through stress relief annealing, the present invention can reduce some dislocation defects, improve the plasticity of the material, reduce internal stress, and homogenize the material. At the same time, through cumulative cold rolling and lamination, it can prevent excessive damage to the material during single cold rolling, release residual stress to avoid cracks in the material during subsequent processing, and refine grains, increase the strength and toughness of the material. Obtain a nano-layered structure and greatly improve the mechanical properties of the material.

[0036] (4) The special distribution form of the iron phase layer and the copper phase layer and the interlayer interface dislocation strengthening effect in the ultra-high strength nano-layered copper-iron composite material provided by the present invention enable the composite material to have a high electrical conductivity, and at the same time have excellent strength and toughness.

[0037] (5) The present invention adopts powder metallurgy combined with a solid-state processing route, avoiding the problem of composition segregation caused by liquid phase separation in the traditional casting method. Description of the Drawings

[0038] Figure 1 is the transmission diagram of the nano-layered copper-iron composite material prepared in Example 1. Detailed Embodiments

[0039] To facilitate the understanding of the present invention, the following will describe the present invention in a more comprehensive and detailed manner in combination with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0040] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0041] Unless otherwise specified, all reagents and raw materials used in the present invention are commercially available products or products that can be prepared by known methods.

[0042] Example 1

[0043] A method for preparing an ultra-high-strength nano-layered copper-iron composite material, comprising the following steps:

[0044] S1. Preparation of raw materials:

[0045] According to the mass percentage, the iron content is 40%, and the balance is copper;

[0046] Among them, the copper powder has a purity of ≥99.9%, the copper powder is high-purity water atomized copper, and the powder particle size is 10-20 μm; the iron powder purity is ≥99.9%, the iron powder is high-purity water atomized iron powder, and the powder particle size is 20-50 μm.

[0047] S2. Mixing of raw materials:

[0048] The copper-iron mixed powder is evenly divided and filled into four ball milling jars. The ball milling jars are evacuated, then argon is introduced for 30 s, then evacuated and argon is introduced again. After repeating 4 times, ball milling is started, and the ball milling time is 8 h.

[0049] S3. Vacuum hot pressing and sintering:

[0050] The mixed powder obtained in S2 is loaded into a hot pressing die, and a preliminary cold pressing is carried out at room temperature under a pressure of 8 MPa, and then put into a vacuum hot pressing furnace for sintering. The vacuum degree is 0.01 MPa, the sintering temperature is 950 °C, a pressure of 25 MPa is applied, and sintering is carried out for 60 min, and it is cooled with the furnace to obtain an ingot-shaped copper-iron blank.

[0051] S4. Hot extrusion forming:

[0052] The copper-iron blank obtained in S3 is kept warm in a vacuum furnace for 30 min at a temperature of 950 °C, and the extrusion ratio is 25, and hot extrusion is carried out to obtain a strip-shaped composite material.

[0053] S5. Accumulative roll bonding:

[0054] The strip-shaped composite material obtained in S4 is put into a vacuum furnace at 500 °C for annealing for 30 min. The annealed sample is cold-rolled and roll-bonded 6 times using a rolling mill (when roll-bonding, the interlayer direction of the strip-shaped composite copper-iron material is the same as the rolling direction), and the total deformation amount is 90%. After rolling, a copper-iron composite material with a nano-layered structure and a total thickness of about 1 mm is obtained. The single-layer thickness of the continuous iron-phase nano-layer is 100-150 nm, and the thickness of the copper-phase nano-layer is 10-50 nm.

[0055] Example 2

[0056] A preparation method of an ultra-high strength nano-layered copper-iron composite material, comprising the following steps:

[0057] S1. Raw material preparation:

[0058] According to the mass percentage, the iron content is 50%, and the balance is copper;

[0059] Among them, the purity of copper powder is ≥99.9%, the copper powder is high-purity water atomized copper, and the powder particle size is 10-20μm; the purity of iron powder is ≥99.9%, the iron powder is high-purity water atomized iron powder, and the powder particle size is 20-50μm.

[0060] S2. Mixing raw materials:

[0061] Uniformly divide the copper-iron mixed powder into four ball milling jars, evacuate the ball milling jars, then introduce argon for 30s, evacuate again and introduce argon. After repeating 4 times, start ball milling, and the ball milling time is 8h.

[0062] S3. Vacuum hot pressing and sintering:

[0063] Put the mixed powder obtained in S2 into a hot pressing mold, apply a pressure of 5MPa at room temperature for preliminary cold pressing and forming, then put it into a vacuum hot pressing furnace for sintering, the vacuum degree is 0.01MPa, the sintering temperature is 1000℃, apply a pressure of 10MPa, sinter for 30min, and cool with the furnace to obtain an ingot-shaped copper-iron blank.

[0064] S4. Hot extrusion forming:

[0065] Keep the copper-iron blank obtained in S3 in a vacuum furnace for 30min at a temperature of 950℃, with an extrusion ratio of 25, and perform hot extrusion to obtain a strip-shaped composite material.

[0066] S5. Accumulative roll bonding:

[0067] Put the strip-shaped composite material obtained in S4 into a vacuum furnace at 500℃ for annealing for 30min. Use a rolling mill to perform 5 times of cold rolling and roll bonding on the annealed sample (when roll bonding, the interlayer direction of the strip-shaped composite copper-iron material is consistent with the rolling direction), the total deformation amount is 85%, and after rolling, a copper-iron composite material with a nano-layered structure and a total thickness of about 1.5 mm is obtained. The single-layer thickness of the continuous iron phase nano-layer is 100-180nm, and the thickness of the copper phase nano-layer is 10-80nm.

[0068] Example 3

[0069] A preparation method of an ultra-high strength nano-layered copper-iron composite material, comprising the following steps:

[0070] S1. Raw material preparation:

[0071] According to the mass percentage, the iron content is 60%, and the balance is copper;

[0072] Among them, the purity of the copper powder is ≥99.9%, the copper powder is high-purity water atomized copper, and the powder particle size is 10 - 20μm; the purity of the iron powder is ≥99.9%, the iron powder is high-purity water atomized iron powder, and the powder particle size is 20 - 50μm.

[0073] S2. Mixing raw materials:

[0074] Evenly divide the copper-iron mixed powder into four ball-milling jars, evacuate the ball-milling jars, then introduce argon for 30s, evacuate again and introduce argon, repeat 4 times and then start ball-milling, and the ball-milling time is 8h.

[0075] S3. Vacuum hot pressing and sintering:

[0076] Load the mixed powder obtained in S2 into a hot pressing mold, apply a pressure of 10MPa at room temperature for preliminary cold pressing and forming, then put it into a vacuum hot pressing furnace for sintering, the vacuum degree is 0.01MPa, the sintering temperature is 1000°C, apply a pressure of 10MPa, sinter for 30min, and cool with the furnace to obtain an ingot-shaped copper-iron blank.

[0077] S4. Hot extrusion forming:

[0078] Keep the copper-iron blank obtained in S3 in a vacuum furnace for 30min at a temperature of 1000°C, with an extrusion ratio of 25, and perform hot extrusion to obtain a strip-shaped composite material.

[0079] S5. Accumulative roll bonding:

[0080] Put the strip-shaped composite material obtained in S4 into a vacuum furnace at 500°C for annealing for 30min, and use a rolling mill to perform cold rolling and roll bonding on the annealed sample 4 times (when roll bonding, the interlayer direction of the strip-shaped copper-iron composite material is consistent with the rolling direction), with a total deformation amount of 80%, and a copper-iron composite material with a nano-layered structure and a thickness of about 2mm is obtained after rolling. The single-layer thickness of the continuous iron-phase nano-layer is 100 - 150nm, and the thickness of the copper-phase nano-layer is 10 - 50nm.

[0081] Example 4

[0082] A preparation method of an ultra-high-strength nano-layered copper-iron composite material, comprising the following steps:

[0083] S1. Preparation of raw materials:

[0084] According to the mass percentage, the iron content is 60%, and the balance is copper;

[0085] Among them, the purity of the copper powder is ≥99.9%, the copper powder is high-purity water atomized copper, and the powder particle size is 10 - 20μm; the purity of the iron powder is ≥99.9%, the iron powder is high-purity water atomized iron powder, and the powder particle size is 20 - 50μm.

[0086] S2. Mixing raw materials:

[0087] The copper-iron mixed powder is evenly divided and filled into four ball milling jars. The ball milling jars are evacuated, then argon gas is introduced for 30 s, then evacuated again and argon gas is introduced. After repeating this 6 times, ball milling is started, and the ball milling time is 16 h.

[0088] S3. Vacuum hot pressing and sintering:

[0089] The mixed powder obtained in S2 is loaded into a hot pressing die, and a preliminary cold pressing is carried out at room temperature under a pressure of 10 MPa. Then it is put into a vacuum hot pressing furnace for sintering. The vacuum degree is 0.01 MPa, the sintering temperature is 1000 °C, a pressure of 30 MPa is applied, and sintering is carried out for 120 min, and it is cooled with the furnace to obtain an ingot-shaped copper-iron blank.

[0090] S4. Hot extrusion forming:

[0091] The copper-iron blank obtained in S3 is kept warm in a vacuum furnace for 30 min at a temperature of 1000 °C, and hot extrusion is carried out with an extrusion ratio of 22 to obtain a strip-shaped composite material.

[0092] S5. Accumulative roll bonding:

[0093] The strip-shaped composite material obtained in S4 is put into a vacuum furnace at 500 °C for annealing for 30 min. The annealed sample is cold rolled and roll bonded 4 times using a rolling mill (when roll bonding, the interlayer direction of the strip-shaped composite copper-iron material is consistent with the rolling direction), and the total deformation amount is 80%. After rolling, a copper-iron composite material with a nano-layered structure and a thickness of about 2 mm is obtained.

[0094] Example 5

[0095] A preparation method of an ultra-high-strength nano-layered copper-iron composite material, comprising the following steps:

[0096] S1. Raw material preparation:

[0097] According to the mass percentage, the iron content is 60%, and the balance is copper;

[0098] Among them, the purity of the copper powder is ≥99.9%, the copper powder is high-purity water atomized copper, and the powder particle size is 10 - 20 μm; the purity of the iron powder is ≥99.9%, the iron powder is high-purity water atomized iron powder, and the powder particle size is 20 - 50 μm.

[0099] S2. Mixing raw materials:

[0100] The copper-iron mixed powder is evenly divided and filled into four ball milling jars. The ball milling jars are evacuated, then argon gas is introduced for 30 s, then evacuated again and argon gas is introduced. After repeating this 5 times, ball milling is started, and the ball milling time is 12 h.

[0101] S3. Vacuum hot pressing and sintering:

[0102] Load the mixed powder obtained in S2 into a hot pressing mold, apply a pressure of 10 MPa at room temperature for preliminary cold pressing and forming, then put it into a vacuum hot pressing furnace for sintering. The vacuum degree is 0.01 MPa, the sintering temperature is 900 °C, apply a pressure of 15 MPa, sinter for 60 min, and cool with the furnace to obtain an ingot-shaped copper-iron blank.

[0103] S4. Hot extrusion forming:

[0104] Keep the copper-iron blank obtained in S3 in a vacuum furnace for 30 min at a temperature of 950 °C, with an extrusion ratio of 24, and perform hot extrusion to obtain a strip-shaped composite material.

[0105] S5. Accumulative roll bonding:

[0106] Put the strip-shaped composite material obtained in S4 into a vacuum furnace at 500 °C for annealing for 30 min. Use a rolling mill to perform 5 times of cold rolling and accumulative roll bonding on the annealed sample (when accumulatively roll bonding the strip-shaped copper-iron composite material, the interlayer direction is consistent with the rolling direction). The total deformation amount is 80%, and after rolling, a copper-iron composite material with a nano-layered structure and a thickness of about 2 mm is obtained.

[0107] Comparative example 1

[0108] The difference between this comparative example and Example 1 is that in step S3, the vacuum hot pressing sintering temperature is 1500 °C and the applied pressure is 30 MPa.

[0109] Comparative example 2

[0110] The difference between this comparative example and Example 2 is that in step S3, the vacuum hot pressing sintering temperature is 1500 °C and the applied pressure is 30 MPa.

[0111] Comparative example 3

[0112] The difference between this comparative example and Example 3 is that in step S3, the sintering temperature is 1100 °C and the applied pressure is 30 MPa.

[0113] Comparative example 4

[0114] The difference between this comparative example and Example 1 is only that step 5 is changed to 1 time of cold rolling, controlling the total deformation amount to be 80%. The other steps are the same. The obtained copper-iron composite material is damaged due to excessive single rolling, and cracks appear on the surface.

[0115] Comparative example 5

[0116] The difference between this comparative example and Example 1 is only that in step 5, the strip-shaped sample is directly subjected to 6 times of cold rolling and accumulative roll bonding without annealing treatment to obtain a copper-iron composite material.

[0117] Comparative example 6

[0118] The difference between this comparative example and Example 1 lies only in that the interlayer direction of the strip composite copper-iron material is inconsistent with the rolling direction during cumulative roll bonding in Step 5, resulting in a copper-iron composite material.

[0119] The copper-iron composite materials obtained in Examples 1 to 5 were respectively subjected to performance tests to explore the effects of different component contents and preparation parameters on the performance. The results are shown in Table 1.

[0120] Table 1

[0121] Number Tensile strength (MPa) Conductivity (%IACS) Elongation at break (%) Example 1 1035 38.6 6.8 Example 2 1109 34.3 5.6 Example 3 1150 29.9 4.2 Example 4 1095 32.4 5.2 Example 5 1119 33.5 4.9 Comparative Example 1 817 37 7.6 Comparative Example 2 904 32.3 6.6 Comparative Example 3 1117 26.6 4.5 Comparative Example 5 1132 28.6 2.4 Comparative Example 6 597 20.6 5.6

[0122] By comparing Examples 1 to 3, it was found that the higher the iron content, the higher the tensile strength, while the electrical conductivity and elongation decreased. By comparing Examples 1 to 3 and Comparative Examples 1 to 3, it was found that increasing the vacuum hot pressing sintering temperature and sintering pressure resulted in a decrease in the tensile strength of the material, while the electrical conductivity and elongation increased.

Claims

1. An ultra-high strength nano-layered copper-iron composite material, characterized in that: The quasi-sandwich structure is composed of alternatingly distributed continuous iron phase nanolayers and continuous copper phase nanolayers, and the interface between the layers is mechanically bonded, and there is a dislocation strengthening effect.

2. The ultra-high strength nano-layered copper-iron composite material according to claim 1, characterized in that: The continuous iron phase nanolayer is a single layer or multiple layers.

3. The ultra-high strength nano-layered copper-iron composite material according to claim 2, characterized in that: The single layer thickness of the continuous iron phase nanolayer is 100-200 nm, the thickness of the copper phase nanolayer is 10-100 nm; the total thickness of the nano-layered copper-iron composite material is 1-2 mm; The mass percentage of iron in the nano-layered copper-iron composite material is 40% to 60%, and the balance is copper.

4. The method for preparing an ultra-high strength nano-layered copper-iron composite material according to any one of claims 1 to 3, characterized in that: The iron powder and the copper powder are weighed and mixed according to the designed ratio, and then subjected to preliminary cold pressing and vacuum hot pressing sintering to obtain an ingot-shaped copper-iron billet; the ingot-shaped copper-iron billet is formed by hot extrusion to obtain a strip-shaped composite copper-iron material; the strip-shaped composite copper-iron material is subjected to stress relief annealing and then cumulative cold rolling and stack rolling to obtain the composite copper-iron material; The temperature of the vacuum hot pressing sintering is 900-1000°C.

5. The method for preparing an ultra-high strength nano-layered copper-iron composite material according to claim 4, characterized in that: The iron powder is high-purity water-atomized iron powder with a purity of ≥99.9% and a particle size of 20 to 50 μm; The copper powder is high-purity water-atomized copper powder with a purity of ≥99.9% and a particle size of 10 to 50 μm.

6. The method for preparing an ultra-high strength nano-layered copper-iron composite material according to claim 5, characterized in that: The ball milling process is as follows: evacuate the ball mill, then introduce argon for 30 seconds, evacuate again and introduce argon, repeat 4 to 6 times, and then ball mill for 8 to 16 hours; The temperature of the preliminary cold pressing is room temperature, and the pressure is 5-10 MPa.

7. The method for preparing an ultra-high strength nano-layered copper-iron composite material according to claim 4 or 6, characterized in that: The vacuum hot pressing sintering conditions are: vacuum degree of 0.01-0.02 MPa, pressure of 10-30 MPa, and sintering time of 30-120 min.

8. The method for preparing an ultra-high strength nano-layered copper-iron composite material according to claim 7, characterized in that: The hot extrusion forming process is as follows: before extrusion, the ingot copper iron billet is placed in a vacuum heating furnace and kept warm at a temperature of 950-1000°C for 0.5-1h; the extrusion nozzle is placed in a heating furnace at an actual temperature of 400-600°C and kept warm for 0.5-1h, and then hot extrusion is performed to obtain a strip composite material, wherein the extrusion ratio is 22-26; The stress relief annealing temperature is 300-500° C., and the annealing time is 0.5-1 hour.

9. The method for preparing an ultra-high strength nano-layered copper-iron composite material according to claim 4, characterized in that: The cumulative cold rolling and lap rolling are performed 4 to 6 times, and the total deformation is 60% to 90%.

10. The method for preparing an ultra-high strength nano-layered copper-iron composite material according to claim 4 or 9, characterized in that: In the process of cumulative cold rolling and bundling, the interlayer direction of the strip-shaped composite copper-iron material during a single cold rolling must be consistent with the rolling direction.

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