A high-strength anti-softening copper-tantalum composite material with a bimodal grain structure and a preparation method thereof

Abstract

The application discloses a high-strength softening-resistant copper-tantalum composite material with a bimodal grain structure and a preparation method thereof, and the method comprises the following steps: firstly, according to the design composition of the target product copper-tantalum composite material, different sizes of copper powder and tantalum powder are mixed and high-energy ball-milled to obtain a multi-element structure copper / tantalum composite powder; secondly, the multi-element structure copper / tantalum composite powder is pre-densified and sintered to obtain a composite blank; and thirdly, the composite blank is rolled or / and extruded to obtain the copper-tantalum composite material. Based on the composite configuration design of the bimodal grain structure, the coarse-fine grain regions are used to form a non-local strain gradient induced back stress strengthening effect, local stress concentration and strain mismatch are relieved, the strength and plasticity of the copper-tantalum composite material are simultaneously improved, and the alloying method is used to introduce a double-scale nano tantalum phase, so that the high-temperature softening resistance of the composite material is improved, and the composite material is suitable for the fields of electronic packaging, heat sinks and electric contact materials.

Description

Technical Field

[0001] This invention belongs to the field of metal matrix composite technology, specifically relating to a high-strength, anti-softening copper-tantalum composite material with a bimodal grain structure and its preparation method. Background Technology

[0002] Copper-tantalum alloys, as important structural materials developed in recent years, possess high mechanical strength, high electrical and thermal conductivity, excellent resistance to arc erosion, and high-temperature softening resistance. They have broad application potential in power electronics, rail transportation, defense, and medical fields, and can be used in current-carrying devices, high-temperature corrosion-resistant electrodes, armor protection, and bio-implants. Metal forming processes play a crucial role in the manufacturing and application of copper-tantalum alloys. However, due to the extremely low miscibility between copper and tantalum (only 0.009 at%) at 1200℃, it is difficult to prepare copper-tantalum alloys with uniform microstructure using traditional casting processes. Therefore, methods such as severe plastic deformation and powder metallurgy are commonly used to prepare copper-tantalum alloys. These structural composite methods can improve the mechanical properties and functional characteristics of the material. However, due to factors such as the Cu / Ta interfacial bonding characteristics and the difference in thermal expansion coefficients, their actual performance is lower than theoretical predictions. For example, Srinivasan et al. (S. Srinivasan, et al. Acta Materialia. 2021,208: 116706.) found that when forming Cu-10at.%Ta alloy using the equal diameter angular extrusion method, the contribution of the interface coherent mode to the strength differed significantly, with the classical mixing criterion contributing only about 20% to the strength; at the same time, while achieving a high strength of 1 GPa, the elongation was only 1%. This problem of "high strength but poor plasticity" is a common challenge faced by copper-tantalum composites, which seriously restricts their application in a wider range of engineering fields.

[0003] To address this issue, researchers have conducted extensive studies on composite configuration designs (such as gradient, layered, brickwork, and micro / nano hybrid structures) to alleviate localized stress concentration and strain mismatch between the reinforcing phase and the metal matrix. These structural designs are based on the principle that gradient microstructures induce geometrically necessary dislocation multiplication and back stress strengthening effects during plastic deformation, thereby improving plasticity by reducing stress concentration at the interface between the soft and hard heterogeneous phases. For copper-tantalum material systems, some scholars have attempted related configuration designs: Vidal et al. (V. Vidal et al., Acta Materialia. 2006, 54: 1063–1075.) prepared Cu-13vol.%Ta multi-scale structure wires (Φ=2.41mm) by bundle drawing, with a tensile strength of 634MPa, but the core of the wire was prone to brittle fracture after further processing; Zeng et al. (LF Zeng et al., Acta Materialia. 2016, 110: 341–351.) prepared Cu / Ta layered composite materials by cross-cumulative rolling, with a tensile strength of 950MPa but an elongation of only 4%; Cao et al. (ZH Cao et al., Acta Materialia. 2020, 195: 240–251.) used magnetron sputtering to prepare Cu / Ta films with customized layer thicknesses, achieving a good match between a compressive yield strength of 1GPa and 70% plastic strain. In summary, while existing processes have improved the strength-ductility balance of copper-tantalum composites to some extent, they still face challenges such as complex configuration design and insufficient synergistic control of strength and ductility. Furthermore, the high-temperature softening resistance of copper-tantalum composites is a key factor limiting their application. Therefore, achieving a balance between high strength and ductility and excellent high-temperature stability in copper-tantalum systems remains a critical issue that urgently needs to be addressed. Summary of the Invention

[0004] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a method for preparing a high-strength, soften-resistant copper-tantalum composite material with a bimodal grain structure. This method involves high-energy ball milling and mixing of copper powder and tantalum powder of different sizes, followed by sintering and deformation, to obtain a copper-tantalum composite material with a microstructure featuring a coarse-fine bimodal grain structure copper matrix and a dual-scale nano-tantalum phase. Utilizing the multi-component composite structure composed of a high volume fraction, small-sized nano-reinforcing phase, and a bimodal grain structure matrix, the back stress strengthening effect, dispersion pinning effect, nano-effect, and interface effect are induced to work together on the copper-tantalum composite material, improving the strength-ductility balance and achieving excellent high-temperature softening resistance. This solves the problem of copper-tantalum composite materials struggling to simultaneously possess high strength, ductility, toughness, and high thermal stability.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing a high-strength, anti-softening copper-tantalum composite material with a bimodal grain structure, characterized in that the method includes the following steps:

[0006] Step 1: According to the design composition of the target product copper-tantalum composite material, copper powder and tantalum powder of different sizes, including particle size I and particle size II, are mixed and then subjected to high-energy ball milling to obtain multi-component copper / tantalum composite powder.

[0007] Step 2: The multi-component copper / tantalum composite powder obtained in Step 1 is pre-densified and sintered to form a composite ingot.

[0008] Step 3: Roll and / or extrude the composite billet obtained in Step 2 to obtain a high-strength, anti-softening copper-tantalum composite material with a bimodal grain structure.

[0009] This invention is based on a composite configuration design with a bimodal grain structure. Copper powder and tantalum powder of different sizes are mixed and then ball-milled at high energy. This allows the copper-tantalum powder to promote solid-state diffusion through periodic cold welding-deformation-crushing, achieving particle refinement and expansion of solid solubility. Then, pre-densification and sintering are carried out. Through the rearrangement and diffusion creep of powder particles under high temperature and high pressure, a composite structure is formed between a bimodal nano-tantalum phase (large size originates from powder refinement, and small size originates from copper-tantalum micro-solid solution precipitation) and a copper matrix with a bimodal grain structure. Finally, the density and mechanical properties of the copper-tantalum composite material are improved through a deformation process.

[0010] The copper-tantalum composite material of this invention exhibits a bimodal grain structure. It utilizes the nonlocal strain gradient formed by the coarse-fine grain regions to induce a back stress strengthening effect, along with dispersed pinning, nano-effects, and interface effects. Numerous geometrically necessary dislocations are nucleated at the copper / tantalum interface, thereby alleviating local stress concentration and strain mismatch between the reinforcing phase and the matrix, improving interfacial load transfer capacity, and inhibiting crack initiation, thus achieving a synergistic improvement in the strength and plasticity of the copper-tantalum composite material. Simultaneously, the copper-tantalum composite material of this invention contains a dual-scale nano-tantalum phase. The pinning and dragging effect of the dual-scale nano-phase on the copper grain boundaries enhances the high-temperature softening resistance of the copper-tantalum composite material.

[0011] The above-mentioned method for preparing a high-strength, anti-softening copper-tantalum composite material with a bimodal grain structure is characterized in that the designed composition of the target product copper-tantalum composite material in step one is, by mass percentage: Ta 5%~25%, with the balance being Cu and unavoidable impurities.

[0012] The above-mentioned method for preparing a high-strength, softening-resistant copper-tantalum composite material with a bimodal grain structure is characterized in that, in step one, the copper powder has a particle size of 10 μm to 45 μm, and particle size I is more than twice that of particle size II; the mass ratio of copper powder with particle size I to copper powder with particle size II is 9:1 to 7:3; the tantalum powder has a particle size of 3 μm to 20 μm. By limiting the particle size of the raw materials, the formation of a bimodal grain structure in the copper-tantalum composite material is ensured, and it has an ultrafine or nanocrystalline scale.

[0013] The above-mentioned method for preparing a high-strength, softening-resistant copper-tantalum composite material with a bimodal grain structure is characterized in that, in step one, the high-energy ball milling speed is 350 rpm to 450 rpm, the time is 10 h to 40 h, the ball-to-material ratio is 10:1 to 15:1, and the protective atmosphere during ball milling is argon. By controlling the process parameters of mechanical alloying, i.e., high-energy ball milling, the full refinement and trace supersaturated solid solution of the multi-component copper powder and tantalum powder are promoted.

[0014] The above-mentioned method for preparing a high-strength, soften-resistant copper-tantalum composite material with a bimodal grain structure is characterized in that the pre-densification method in step two is cold pressing or cold isostatic pressing, and the sintering is spark plasma sintering or hot pressing sintering. Specifically, the spark plasma sintering temperature is 850℃~900℃, the holding time is 5min~10min, and the pressure is 30MPa~50MPa; the hot pressing sintering temperature is 850℃~900℃, the holding time is 120min, and the pressure is 30MPa~50MPa. This invention significantly reduces sintering time and avoids grain growth by using spark plasma sintering; and it allows for precise control of sintering temperature and pressure by using hot pressing sintering, eliminating porosity defects in the copper-tantalum composite material and improving the uniformity of the microstructure.

[0015] The method for preparing a high-strength, soften-resistant copper-tantalum composite material with a bimodal grain structure, as described above, is characterized in that the sintering in step two is performed under vacuum, and the vacuum degree inside the sintering equipment cavity does not exceed 6.7 × 10⁻⁶. -3 Pa.

[0016] The above-mentioned method for preparing a high-strength, softening-resistant copper-tantalum composite material with a bimodal grain structure is characterized in that, in step three, the deformation amount during rolling is 50%~70%, the deformation ratio during extrusion is 9:1~18:1, and the deformation temperature is 900℃, with the material held at 900℃ for 30 minutes before deformation. By controlling the deformation process parameters, it is beneficial to improve the density and mechanical properties of the copper-tantalum composite material.

[0017] Meanwhile, the present invention also discloses a high-strength, anti-softening copper-tantalum composite material with a bimodal grain structure, characterized in that it is prepared by the above-described method.

[0018] The aforementioned high-strength, softening-resistant copper-tantalum composite material with a bimodal grain structure is characterized in that the coarse grain size in the bimodal grain structure is less than 2 μm, and the fine grain size is less than 0.5 μm. The tensile strength σ of the copper-tantalum composite material is... b ≥400MPa, elongation A≥4%, softening temperature above 650℃.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. This invention obtains a multi-component copper / tantalum composite powder by high-energy ball milling of copper powder and tantalum powder of different sizes. Combined with sintering and deformation processes, a copper-tantalum composite material with bimodal grain structure and dual-scale nanophase reinforcement is obtained. This copper-tantalum composite material has both high strength and high plasticity, and also has the ability to resist high temperature softening. It can significantly improve the strength-plasticity matching and high temperature thermal stability of copper-tantalum composite material, and effectively expand its application value under extreme working conditions.

[0021] 2. This invention obtains a bimodal grain structure of copper matrix in copper-tantalum composite material by using copper powder of different scales and high-temperature sintering, which alleviates local stress concentration and strain mismatch between the reinforcing phase and the matrix, and achieves synergistic improvement of strength and plasticity of copper-tantalum composite material. By introducing a dual-scale nano tantalum phase through mechanical alloying, i.e., high-energy ball milling combined with high-temperature sintering, the high-temperature softening resistance of copper-tantalum composite material is improved. The process is simple and easy to implement.

[0022] 3. The high-energy ball milling, sintering and deformation processes in the preparation process of this invention are simple and controllable. Moreover, by simply adjusting the particle size of the raw copper powder, bimodal copper grain structures of different sizes can be obtained through subsequent processes. The grain structure is easy to control and is suitable for large-scale production.

[0023] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation

[0024] Example 1

[0025] This embodiment includes the following steps:

[0026] Step 1: According to the design nominal composition of the target product, copper-tantalum composite material, Cu-5wt.%Ta, that is, Ta is 5% by mass, and the balance is Cu and unavoidable impurities, copper powder of different sizes, including 42.75g of copper powder with a particle size of 45μm and 4.75g of copper powder with a particle size of 10μm, and 2.5g of tantalum powder with a particle size of 3μm, are mixed and then subjected to high-energy ball milling to obtain multi-component copper / tantalum composite powder; the high-energy ball milling speed is 350rpm, the time is 10h, the ball-to-material ratio is 10:1, and the protective atmosphere during ball milling is argon.

[0027] Step 2: The multi-component copper / tantalum composite powder obtained in Step 1 is subjected to cold pressing and spark plasma sintering to form a composite ingot with a diameter of Φ30mm. The spark plasma sintering temperature is 850℃, the holding time is 5min, the pressure is 30MPa, and the process is carried out under vacuum, with a vacuum degree of 6.7×10⁻⁶ within the sintering equipment chamber. -3 Pa;

[0028] Step 3: Roll the composite billet obtained in Step 2 to obtain a high-strength, anti-softening copper-tantalum composite material with a bimodal grain structure; the rolling temperature is 900℃, and the billet is held at 900℃ for 30 minutes before rolling, and the deformation during rolling is 70%.

[0029] Testing revealed that the copper-tantalum composite material prepared in this embodiment exhibits a bimodal grain structure with coarse grains smaller than 2 μm and fine grains smaller than 0.5 μm. Furthermore, the composite material contains bi-scale nano-tantalum phases dispersed within the grains and at grain boundaries, with sizes ranging from 30 nm to 100 nm and less than 6 nm, respectively. The tensile strength σ of this copper-tantalum composite material is [not specified in the original text]. b =453MPa, elongation A=15.3%, softening temperature is 684℃.

[0030] Example 2

[0031] This embodiment includes the following steps:

[0032] Step 1: According to the design nominal composition of the target product, copper-tantalum composite material, Cu-10wt.%Ta, that is, Ta is 10% by mass, and the balance is Cu and unavoidable impurities, copper powder of different sizes, including 38.25g of copper powder with a particle size of 45μm and 6.75g of copper powder with a particle size of 10μm, are mixed with 5g of tantalum powder with a particle size of 3μm and then subjected to high-energy ball milling to obtain multi-component copper / tantalum composite powder; the high-energy ball milling speed is 400rpm, the time is 20h, the ball-to-material ratio is 10:1, and the protective atmosphere during ball milling is argon.

[0033] Step 2: The multi-component copper / tantalum composite powder obtained in Step 1 is subjected to cold pressing and spark plasma sintering to form a composite ingot with a diameter of Φ30mm. The spark plasma sintering temperature is 850℃, the holding time is 5min, the pressure is 30MPa, and the process is carried out under vacuum, with a vacuum degree of 6.7×10⁻⁶ within the sintering equipment chamber. -3 Pa;

[0034] Step 3: Roll the composite billet obtained in Step 2 to obtain a high-strength, anti-softening copper-tantalum composite material with a bimodal grain structure; the rolling temperature is 900℃, and the billet is held at 900℃ for 30 minutes before rolling, and the deformation during rolling is 70%.

[0035] Testing revealed that the copper-tantalum composite material prepared in this embodiment exhibits a bimodal grain structure with coarse grains smaller than 2 μm and fine grains smaller than 0.5 μm. Furthermore, the composite material contains bi-scale nano-tantalum phases dispersed within the grains and at grain boundaries, with sizes ranging from 30 nm to 100 nm and less than 6 nm, respectively. The tensile strength σ of this copper-tantalum composite material is [not specified in the original text]. b =583MPa, elongation A=12.6%, softening temperature is 740℃.

[0036] Comparative Example 1

[0037] The difference between this comparative example and Example 2 is that in step one, 45g of copper powder with a particle size of 45μm and 5g of tantalum powder with a particle size of 3μm were mixed and then subjected to high-energy ball milling to obtain copper / tantalum composite powder.

[0038] Testing revealed that the copper-tantalum composite material prepared in this comparative example possessed only a single coarse-grained structure, with a grain size of less than 5 μm; the tensile strength σ of this copper-tantalum composite material was [missing information]. b =615MPa, elongation A=7.3%, softening temperature is 710℃.

[0039] Example 3

[0040] This embodiment includes the following steps:

[0041] Step 1: According to the design nominal composition of the target product, copper-tantalum composite material, Cu-15wt.%Ta, that is, Ta is 15% by mass, with the balance being Cu and unavoidable impurities, copper powder of different sizes, including 108.8g of copper powder with a particle size of 45μm and 27.2g of copper powder with a particle size of 10μm, and 24g of tantalum powder with a particle size of 20μm, are mixed and then subjected to high-energy ball milling to obtain multi-component copper / tantalum composite powder; the high-energy ball milling speed is 400rpm, the time is 20h, the ball-to-material ratio is 15:1, and the protective atmosphere during ball milling is argon.

[0042] Step 2: The multi-component copper / tantalum composite powder obtained in Step 1 is subjected to cold isostatic pressing and hot pressing sintering to obtain a composite ingot with a diameter of Φ30mm. The hot pressing sintering temperature is 850℃, the holding time is 120min, the pressure is 30MPa, and the process is carried out under vacuum, with a vacuum degree of 6.7×10⁻⁶ inside the sintering equipment chamber. -3 Pa;

[0043] Step 3: The composite billet obtained in Step 2 is extruded and deformed to a diameter of Φ7mm. Then, the bar obtained by extrusion deformation is rolled and deformed to obtain a high-strength, anti-softening copper-tantalum composite material with a bimodal grain structure. The extrusion and rolling temperature is 900℃, and the temperature is kept at 900℃ for 30 minutes before extrusion and rolling. The deformation ratio of extrusion is 18:1, and the deformation amount of rolling is 50%.

[0044] Testing revealed that the copper-tantalum composite material prepared in this embodiment exhibits a bimodal grain structure with coarse grains smaller than 2 μm and fine grains smaller than 0.5 μm. Furthermore, the composite material contains bi-scale nano-tantalum phases dispersed within the grains and at grain boundaries, with sizes ranging from 30 nm to 100 nm and less than 6 nm, respectively. The tensile strength σ of this copper-tantalum composite material is [not specified in the original text]. b =654MPa, elongation A=10.1%, softening temperature is 854℃.

[0045] Example 4

[0046] This embodiment includes the following steps:

[0047] Step 1: According to the design nominal composition of the target product, copper-tantalum composite material, Cu-20wt.%Ta, that is, Ta by mass percentage is 20%, with the balance being Cu and unavoidable impurities, copper powder of different sizes, including 102.4g of copper powder with a particle size of 45μm and 25.6g of copper powder with a particle size of 10μm, and tantalum powder with a particle size of 20μm, are mixed and then subjected to high-energy ball milling to obtain multi-component copper / tantalum composite powder; the high-energy ball milling speed is 450rpm, the time is 40h, the ball-to-material ratio is 15:1, and the protective atmosphere during ball milling is argon.

[0048] Step 2: The multi-component copper / tantalum composite powder obtained in Step 1 is subjected to cold pressing and spark plasma sintering to form a composite ingot with a diameter of Φ30mm. The spark plasma sintering temperature is 900℃, the holding time is 10min, the pressure is 50MPa, and the process is carried out under vacuum, with a vacuum degree of 6.7×10⁻⁶ within the sintering equipment chamber. -3 Pa;

[0049] Step 3: The composite billet obtained in Step 2 is extruded and deformed to a diameter of Φ7mm. Then, the extruded bar is rolled to obtain a high-strength, softening-resistant copper-tantalum composite material with a bimodal grain structure. The extrusion and rolling temperatures are 900℃, and both are held at 900℃ for 30 minutes before extrusion and rolling. The extrusion deformation ratio is 18:1, and the rolling deformation is 50%.

[0050] Testing revealed that the copper-tantalum composite material prepared in this embodiment exhibits a bimodal grain structure with coarse grains smaller than 2 μm and fine grains smaller than 0.5 μm. Furthermore, the composite material contains bi-scale nano-tantalum phases dispersed within the grains and at grain boundaries, with sizes ranging from 30 nm to 100 nm and less than 6 nm, respectively. The tensile strength σ of this copper-tantalum composite material is [not specified in the original text]. b =805MPa, elongation A=6.5%, softening temperature is 930℃.

[0051] Example 5

[0052] This embodiment includes the following steps:

[0053] Step 1: According to the design nominal composition of the target product, copper-tantalum composite material, Cu-25wt.%Ta, that is, Ta by mass percentage is 25%, with the balance being Cu and unavoidable impurities, different sizes of copper powder, including 84g of copper powder with a particle size of 45μm and 36g of copper powder with a particle size of 10μm, are mixed with 40g of tantalum powder with a particle size of 20μm and then subjected to high-energy ball milling to obtain multi-component copper / tantalum composite powder; the high-energy ball milling speed is 450rpm, the time is 40h, the ball-to-material ratio is 15:1, and the protective atmosphere during ball milling is argon.

[0054] Step 2: The multi-component copper / tantalum composite powder obtained in Step 1 is subjected to cold isostatic pressing and hot pressing sintering to obtain a composite ingot with a diameter of Φ30mm. The hot pressing sintering temperature is 900℃, the holding time is 120min, the pressure is 50MPa, and the process is carried out under vacuum, with a vacuum degree of 6.7×10⁻⁶ inside the sintering equipment cavity. -3 Pa;

[0055] Step 3: The composite billet obtained in Step 2 is extruded and deformed to a diameter of Φ7mm. Then, the bar obtained by extrusion deformation is rolled and deformed to obtain a high-strength, anti-softening copper-tantalum composite material with a bimodal grain structure. The extrusion and rolling temperature is 900℃, and the temperature is kept at 900℃ for 30 minutes before extrusion and rolling. The deformation ratio of extrusion is 9:1, and the deformation amount of rolling is 50%.

[0056] Testing revealed that the copper-tantalum composite material prepared in this embodiment exhibits a bimodal grain structure with coarse grains smaller than 2 μm and fine grains smaller than 0.5 μm. Furthermore, the composite material contains bi-scale nano-tantalum phases dispersed within the grains and at grain boundaries, with sizes ranging from 30 nm to 100 nm and less than 6 nm, respectively. The tensile strength σ of this copper-tantalum composite material is [not specified in the original text]. b =910MPa, elongation A=4.1%, softening temperature is 981℃.

[0057] The tensile strength, elongation, and softening temperature of the copper-tantalum composite materials prepared in Examples 1-5 and Comparative Example 1 of this invention are shown in Table 1 below.

[0058] Table 1

[0059]

[0060] As can be seen from Table 1, the tensile strength σ of the copper-tantalum composite materials prepared in Examples 1-5 of this invention is... bWith a strength ≥400MPa, elongation A ≥4%, and softening resistance temperature above 650℃, this invention exhibits high strength and resistance to softening. Comparing Example 2 with Comparative Example 1, it can be seen that this invention achieves a synergistic improvement in the strength and plasticity of copper-tantalum composite materials by using copper powder of different sizes combined with subsequent sintering processes to construct a bimodal grain structure.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-strength, softening-resistant copper-tantalum composite material with a bimodal grain structure, characterized in that, The method includes the following steps: Step 1: According to the designed composition of the target product, copper-tantalum composite material, copper powder and tantalum powder of different sizes, including particle size I and particle size II, are mixed and then subjected to high-energy ball milling to obtain multi-component copper / tantalum composite powder. The designed composition of the target product, copper-tantalum composite material, is as follows (by mass percentage): Ta 5%~25%, with the balance being Cu and unavoidable impurities. The particle size of the copper powder is 10μm~45μm, and particle size I is more than twice that of particle size II. The mass ratio of copper powder with particle size I to copper powder with particle size II is 9:1~7:

3. The particle size of the tantalum powder is 3μm~20μm. The high-energy ball milling speed is 350rpm~450rpm, the time is 10h~40h, the ball-to-material ratio is 10:1~15:1, and the protective atmosphere during ball milling is argon. Step 2: The multi-component copper / tantalum composite powder obtained in Step 1 is pre-densified and sintered to form a composite ingot. Step 3: Roll and / or extrude the composite billet obtained in Step 2 to obtain a high-strength, anti-softening copper-tantalum composite material with a bimodal grain structure.

2. The method for preparing a high-strength, anti-softening copper-tantalum composite material with a bimodal grain structure according to claim 1, characterized in that, The pre-densification method in step two is cold pressing or cold isostatic pressing, and the sintering is spark plasma sintering or hot pressing sintering. Specifically, the temperature of spark plasma sintering is 850℃~900℃, the holding time is 5min~10min, and the pressure is 30MPa~50MPa; the temperature of hot pressing sintering is 850℃~900℃, the holding time is 120min, and the pressure is 30MPa~50MPa.

3. The method for preparing a high-strength, anti-softening copper-tantalum composite material with a bimodal grain structure according to claim 1, characterized in that, The sintering described in step two is carried out under vacuum, and the vacuum level inside the sintering equipment cavity does not exceed 6.7 × 10⁻⁶. -3 Pa.

4. The method for preparing a high-strength, anti-softening copper-tantalum composite material with a bimodal grain structure according to claim 1, characterized in that, In step three, the deformation amount of rolling is 50%~70%, the deformation ratio of extrusion is 9:1~18:1, and the deformation temperature is 900℃. Before deformation, the material is held at 900℃ for 30 minutes.

5. A high-strength, anti-softening copper-tantalum composite material with a bimodal grain structure, characterized in that, Prepared by the method described in any one of claims 1 to 4.

6. The high-strength, anti-softening copper-tantalum composite material with a bimodal grain structure according to claim 5, characterized in that, In the bimodal grain structure, the coarse grain size is less than 2 μm, and the fine grain size is less than 0.5 μm. The tensile strength σ of the copper-tantalum composite material is... b ≥400MPa, elongation A≥4%, softening temperature above 650℃.

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