Molding deformation method for improving strength of copper-tungsten composite material by inducing nano twin crystals

Abstract

The invention provides a plastic deformation method for improving the strength of a copper-tungsten composite material by inducing nano twin crystals. The method comprises the following steps: mixing and ball-milling copper powder and tungsten powder, carrying out spark plasma sintering, carrying out low-temperature dynamic plastic deformation and annealing. According to the method, crystal grains are effectively refined, generation of a large number of nano twin crystals in the material is promoted, the strength of the obtained copper-tungsten composite material is remarkably improved, and the room-temperature average tensile strength of the finally obtained high-strength copper-tungsten composite material with the nano twin crystal structure is larger than 500 MPa, the yield strength is larger than 450 MPa, and the ductility is larger than 10%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal material processing, and particularly relates to a plastic deformation method for improving the strength of copper-tungsten composite material by inducing nanotwins. BACKGROUND

[0002] With the rapid development of modern industry, higher requirements are put forward for the comprehensive performance of materials in terms of high conductivity, high strength and high temperature resistance, etc. The copper-tungsten composite material is composed of copper phase and tungsten phase which are not mutually soluble, and has the advantages of high conductivity of copper and high melting point and high strength of tungsten, and is widely used in the fields of electric power, electronics, aerospace and rail transportation. However, due to the characteristics of the material system, the traditional preparation and processing method is difficult to further improve the mechanical properties while ensuring the high conductivity. SUMMARY

[0003] The technical problem to be solved by the application is to provide a plastic deformation method for improving the strength of copper-tungsten composite material by inducing nanotwins, which effectively refines the grains, promotes the generation of a large number of nanotwins in the material, and significantly improves the strength of the copper-tungsten composite material. The high-strength copper-tungsten composite material with nanotwin structure finally obtained has an average tensile strength of >500MPa, a yield strength of >450MPa, and an elongation of >10% at room temperature.

[0004] The method promotes the generation of a large number of nanotwins in the material matrix, realizes the improvement of the strength of the copper-tungsten composite material and the maintenance of the conductivity.

[0005] To solve the above technical problems, the technical scheme adopted by the application is as follows: a plastic deformation method for improving the strength of copper-tungsten composite material by inducing nanotwins, which comprises the following steps: S1. Ball milling copper powder and tungsten powder under a protective atmosphere to obtain mixed powder; The application ball mills the copper powder and the tungsten powder under a protective atmosphere to make the two-phase raw materials fully contact and uniformly disperse, effectively improves the dispersion uniformity of copper and tungsten on a microscale, lays a foundation for forming a stable and continuous composite structure in the subsequent sintering process, and guarantees the consistency of the copper-tungsten composite material structure and the stability of the performance from the source; S2. Sintering: discharging the mixed powder obtained in S1 to perform plasma sintering to obtain sintered copper-tungsten composite material; The conditions of the discharge plasma sintering are: first, the longitudinal pressure is increased to 25 MPa and maintained for 2 min; then, the temperature is increased from room temperature to 650-700 DEG C at a temperature increasing rate of 100 DEG C / min, low-temperature densification is realized under the condition that the longitudinal pressure is 50 MPa, and the temperature is maintained for 15-30 min; then, the temperature is increased to 950 DEG C at a temperature increasing rate of 100 DEG C / min, high-temperature sintering is realized under the condition that the longitudinal pressure is 50 MPa, and the temperature is maintained for 5-20 min; then, the temperature is decreased to 550-600 DEG C at a temperature decreasing rate of 10 DEG C / min, the sintering is ended under the condition that the longitudinal pressure is 50 MPa, the furnace is cooled to room temperature, and the longitudinal pressure is decreased to 5 MPa, and the obtained sintered copper-tungsten composite material has high density; In the sintering densification process, the discharge plasma sintering process is adopted, the sintering temperature and sintering pressure are accurately controlled, the composite powder is rapidly densified in a short time, the porosity in the material is effectively reduced, the abnormal growth of the crystal grains is inhibited, and therefore, the copper-tungsten composite material blank with dense structure and good interface combination is obtained, and a good initial organization state is provided for subsequent plastic deformation processing; After the sintering is completed, the material is cooled to room temperature in the furnace, which effectively slows down the thermal stress concentration phenomenon caused by the difference in the thermal expansion coefficients of copper and tungsten, avoids the generation of cracks or other organization defects in the material, and further improves the structural integrity and stability of the sintered copper-tungsten composite material, thereby creating favorable conditions for the subsequent processing process; S3, low-temperature dynamic plastic deformation: the sintered copper-tungsten composite material obtained in S2 is subjected to dynamic plastic deformation, and the material is immersed in liquid nitrogen for 5-10 min before and after each dynamic plastic deformation, and the nanotwin structure is generated in the matrix, so that the plate material exhibits uniform nanotwin structure from the surface layer to the intermediate layer, and the copper-tungsten composite material after dynamic plastic deformation is obtained. The copper-tungsten composite material prepared by the method is in a low-temperature state as a whole; the low-temperature environment can significantly inhibit the dynamic recovery and climbing behavior of dislocations in the material during the subsequent deformation process, and provides favorable conditions for the refinement of the microstructure and the formation of a special interface structure; In the low-temperature dynamic plastic deformation stage, high-strain-rate dynamic load is applied to the copper-tungsten composite material in a low-temperature state, so that the material bears a large shear stress and undergoes severe plastic deformation in a short time, thereby forming a large amount of nanotwin structure in the copper-tungsten composite material. The nanotwin structure is continuously distributed from the surface layer to the inside of the material, and the copper matrix structure is significantly refined; The application breaks through the technical limitation that the traditional plastic processing method is difficult to introduce high-density nanotwin structure in copper-tungsten composite material by the synergistic effect of low-temperature condition and high strain rate dynamic plastic deformation, so that the proportion of nanotwin formation and the uniformity of distribution are significantly improved. S4, annealing treatment: under the protection atmosphere, the copper-tungsten composite material after dynamic plastic deformation in S4 is subjected to annealing treatment at a temperature of 200-350 DEG C for 10-30 min to eliminate the internal residual stress of the material and stabilize the microstructure, and then naturally cooled to room temperature to obtain high-strength copper-tungsten composite material with nanotwin structure.

[0006] After the low-temperature dynamic plastic deformation is completed, the internal residual stress of the material is eliminated by the annealing treatment process, and the nanotwin structure formed is subjected to stabilization treatment, so that the copper-tungsten composite material maintains high strength while considering good structural stability and service reliability.

[0007] The high-strength copper-tungsten composite material prepared by the application forms a high-density and uniformly distributed nanotwin structure. The nanotwin structure can effectively hinder dislocation movement, improve the yield strength and tensile strength of the material, and has less effect on the electrical conductivity compared with ordinary grain boundaries, thereby realizing the synergistic improvement of the strength and functional performance of the copper-tungsten composite material.

[0008] Preferably, the purity of the copper powder in S1 is ≥99.9%, and the particle size is 1-3 µm; the purity of the tungsten powder is ≥99.9%, and the particle size is 20-100 nm.

[0009] Preferably, the high-purity argon gas with purity ≥99.9% is used as the protection atmosphere in S1; the ball milling conditions are as follows: the mass ratio of ball powder is 5:1, the rotation speed is 50-80 rpm, and the ball milling time is 6-8 h; the grinding ball is a copper ball.

[0010] Preferably, the copper ball is a mixture of two kinds of copper balls with diameters of 7 mm and 3 mm in a mass ratio of 2:1.

[0011] Preferably, the mass fraction of tungsten powder in the mixed powder in S1 is 5-10%.

[0012] Preferably, the vacuum degree of the spark plasma sintering in S2 is <1×10 -3 Pa.

[0013] Preferably, the specific method of the low-temperature dynamic plastic deformation in S3 is: using multi-pass dynamic impact loading to a cumulative total down pressure of >70%.

[0014] Preferably, the high strain rate dynamic load in the multi-pass dynamic impact loading corresponds to a strain rate of not less than 10 2 s -1 .

[0015] Preferably, the high-purity argon gas with a purity of ≥99.9% under the protective atmosphere in S4.

[0016] Preferably, the high-strength copper-tungsten composite material with a nano-twin structure in S4 has an average tensile strength at room temperature of >500MPa, a yield strength of >450MPa, and an elongation of >10%.

[0017] Compared with the prior art, the present application has the following advantages: The present application effectively refines the grains, promotes the generation of a large number of nano-twins in the material, and significantly improves the strength of the copper-tungsten composite material. The high-strength copper-tungsten composite material with a nano-twin structure obtained finally has an average tensile strength at room temperature of >500MPa, a yield strength of >450MPa, and an elongation of >10%.

[0018] The present application will be further described in detail below with reference to the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a nano-twin micro-morphology diagram of the high-strength copper-tungsten composite material with a nano-twin structure prepared in Example 1 of the present application.

[0020] Figure 2 is a high-resolution TEM image of the nano-twin of the high-strength copper-tungsten composite material with a nano-twin structure prepared in Example 1 of the present application. (a) is a high-resolution transmission electron microscope image of the nano-twin sheet layer structure in the copper matrix, and (b) is Figure 2 (a) is a fast Fourier transform (FFT) pattern corresponding to the selected red region in (a). DETAILED DESCRIPTION

[0021] Example 1 The plastic deformation method for inducing nano-twins to improve the strength of the copper-tungsten composite material is as follows: S1, put the copper powder and tungsten powder into a ball mill jar, and add two kinds of copper balls with diameters of 7mm and 3mm as grinding media, wherein the mass ratio of the ball powder is 5:1, and the mass ratio of the large ball to the small ball is 2:1, then fill the ball mill jar with high-purity argon gas with a purity of ≥99.9% and seal, and carry out ball milling treatment at a speed of 80rpm for 6h to fully mix the powders and obtain a mixed powder; the mass fraction of tungsten powder in the mixed powder is 5%; The purity of the copper powder is ≥99.9%, and the particle size is 1µm~3µm; the purity of the tungsten powder is ≥99.9%, and the particle size is 20nm~100nm; The embodiment effectively improves the dispersion uniformity of copper and tungsten on a micro scale by ball-milling copper powder and tungsten powder under a protective atmosphere to make the two-phase raw materials fully contact and uniformly disperse, lays a foundation for forming a stable and continuous composite structure in a subsequent sintering process, and guarantees the consistency of the copper-tungsten composite structure and the stability of the performance from the source; S2, sintering: the mixed powder obtained in S1 is loaded into a graphite mold, and the graphite mold is placed in an FHP-828 rapid hot-pressing sintering furnace to perform discharge plasma sintering under the condition that the vacuum degree is < 1 x 10 -3 Pa to obtain a sintered copper-tungsten composite material in the form of a cylinder with a size of about 30 mm (diameter) x 15 mm (height); The discharge plasma sintering condition is that the longitudinal pressure is first increased to 25 MPa and maintained for 2 min; then the temperature is increased from room temperature to 700℃ at a rate of 100℃ / min, and the low-temperature densification is realized under the condition that the longitudinal pressure is 50 MPa and the temperature is maintained for 15 min; then the temperature is increased to 950℃ at a rate of 100℃ / min, and the high-temperature sintering is realized under the condition that the longitudinal pressure is 50 MPa and the temperature is maintained for 5 min; then the temperature is decreased to 550℃ at a rate of 10℃ / min, and the sintering is ended when the pressure is 50 MPa, the mold is cooled to room temperature with the furnace, and the longitudinal pressure is decreased to 5 MPa, and the sintered copper-tungsten composite material has a high density of 98%; In the sintering densification process, the discharge plasma sintering process is adopted to realize rapid densification of the composite powder in a short time through accurate control of the sintering temperature and sintering pressure, effectively reduces the porosity in the material, and at the same time inhibits the abnormal growth of the grains, so as to obtain a copper-tungsten composite material blank with a dense structure and good interface bonding, and provide a good initial organizational state for the subsequent plastic deformation processing; After sintering is completed, the furnace is cooled to room temperature with the furnace, which effectively slows down the thermal stress concentration phenomenon caused by the difference in the thermal expansion coefficients of copper and tungsten, avoids the generation of cracks or other organizational defects in the material, and further improves the structural integrity and stability of the sintered copper-tungsten composite material, creating favorable conditions for the subsequent processing process; S3, low-temperature dynamic plastic deformation: the sintered copper-tungsten composite material obtained in S2 is cut by wire cutting to form a cylindrical sample with a size of 10 mm in diameter and 12 mm in height, and then dynamic plastic deformation is performed, and the sample is soaked in liquid nitrogen at a temperature of -196℃ for 5 min before and after each dynamic plastic deformation to completely cool the inside, and finally a large number of nano-twin structures are generated in the matrix, so that the plate material exhibits uniform nano-twin structures from the surface layer to the intermediate layer, and a copper-tungsten composite material after dynamic plastic deformation is obtained; The specific method of the low-temperature dynamic plastic deformation is: adopting multi-pass dynamic impact loading, a total of 6 passes, and the strain rate corresponding to the high strain rate dynamic load in the multi-pass dynamic impact loading is not less than 10 2 s -1 , and the thickness reduction is about 80%; In this embodiment, the sample is subjected to severe plastic deformation through multi-pass dynamic impact loading, and the final sample thickness is reduced to about 2mm, the total deformation (thickness reduction) is about 80%, and a sheet-shaped copper-tungsten composite material with a diameter of about 25mm is formed, i.e., the copper-tungsten composite material after dynamic plastic deformation; In this embodiment, low-temperature (liquid nitrogen) treatment is performed before and after dynamic plastic deformation, and the prepared copper-tungsten composite material is in a low-temperature state as a whole; the low-temperature environment can significantly inhibit the dynamic recovery and climb behavior of dislocations in the subsequent deformation process, providing favorable conditions for microstructure refinement and formation of special interface structure; Before and after impact deformation in each pass, the sample is subjected to low-temperature treatment, so that the sample as a whole remains in a low-temperature state, thereby avoiding the influence of temperature rise during deformation on the low-temperature deformation condition.

[0022] In this embodiment, high strain rate dynamic load corresponding to a strain rate of not less than 10 2 s -1 is applied to the copper-tungsten composite material in a low-temperature state during the low-temperature dynamic plastic deformation stage, and severe plastic deformation occurs, thereby forming a large number of nanotwin structures in the copper-tungsten composite material. The nanotwins exhibit a continuous distribution feature from the surface layer to the interior of the material, which significantly refines the copper matrix structure; In this embodiment, through the synergistic effect of low-temperature conditions and high strain rate dynamic plastic deformation, the material is always in a limited recovery state during the entire deformation process, which significantly improves the formation proportion and distribution uniformity of nanotwins, thereby breaking through the technical limitation that traditional plastic processing methods are difficult to introduce high-density nanotwin structures into copper-tungsten composite materials; S4, annealing treatment: under a protective atmosphere (high-purity argon with a purity of ≥99.9%), the copper-tungsten composite material after dynamic plastic deformation obtained in S3 is subjected to annealing treatment at a temperature of 200°C for 20min to eliminate internal residual stress and stabilize the microstructure, and then naturally cooled to room temperature to obtain a high-strength copper-tungsten composite material with nanotwin structure.

[0023] In this embodiment, after completing the low-temperature dynamic plastic deformation, the internal residual stress of the material is eliminated through the annealing treatment process, and the nanotwin structure formed is subjected to stabilization treatment, so that the copper-tungsten composite material maintains high strength while considering good structural stability and service reliability.

[0024] In this embodiment, a high-strength copper-tungsten composite material was prepared, forming a high-density, uniformly distributed nanotwin structure. This nanotwin structure effectively hinders dislocation movement, improves the yield strength and tensile strength of the material, and has less impact on electrical conductivity compared to ordinary grain boundaries, thereby achieving a synergistic improvement in the strength and functional properties of the copper-tungsten composite material.

[0025] The nanotwin microstructure of the high-strength copper-tungsten composite material with a nanotwin structure prepared in this embodiment is as follows: Figure 1 The image shows a transmission electron microscope (TEM) image of a copper-tungsten composite material after low-temperature dynamic plastic deformation treatment. The "W particles" labeled in the image represent tungsten particles dispersed in the copper matrix, appearing as dark areas with high contrast in the TEM image. The area indicated by the arrow and labeled "Multilayer twinned wafers" represents a multilayer nanotwinned wafer structure formed in the copper matrix. This structure consists of multiple sets of parallel-arranged thin-layered structures with interlaminar spacing in the nanoscale range and continuous distribution over a large area, indicating that low-temperature dynamic plastic deformation can induce the formation of high-density nanotwins in the copper matrix. The area circled by the dashed line in the image highlights the typical distribution location of the tungsten particles and their surrounding morphology. It can be observed that a significant nanotwin structure also exists in the vicinity of the tungsten particles, indicating that the presence of the tungsten phase does not hinder the formation of twin structures in the copper matrix.

[0026] The high-resolution TEM image of the nanotwins in the high-strength copper-tungsten composite material with a nanotwin structure prepared in this embodiment is shown below. Figure 2 (a) shows a high-resolution transmission electron microscope image of the copper substrate region. The lattice fringes in the image are continuous and clear, indicating that the crystal structure in this region is complete. The white dashed lines are used to mark the boundaries of twin-related regions, the yellow dashed lines are used to indicate the spatial extension contours of the twin lamellae, and the red dashed boxes are typical regions selected for crystallographic analysis.

[0027] like Figure 2 As shown in (b), Figure 2 (a) shows the Fast Fourier Transform pattern corresponding to the area within the red dashed box. Two sets of diffraction spots with mirror symmetry can be observed, marked by the red and yellow dashed boxes respectively, corresponding to the {111} and {002} crystal planes. This diffraction characteristic is consistent with the crystallographic characteristics of {111} nanotwins in face-centered cubic copper. Combined with... Figure 2 (a) and Figure 2 (b) It can be seen that after low-temperature dynamic plastic deformation treatment, nanotwin boundaries with clear crystal orientation relationship and stable structure are formed in the copper matrix.

[0028] The high-strength copper-tungsten composite material with nanotwin structure prepared in the embodiment is subjected to mechanical property test, and the test result shows that the tensile strength of the material is 562.1 MPa, the yield strength is 462.8 MPa, the elongation is 11%, and the conductivity is 81% under room temperature condition, and the material exhibits good strength and plasticity matching characteristics and good conductivity.

[0029] Embodiment 2 The plastic deformation method for inducing nanotwin to improve the strength of the copper-tungsten composite material in the embodiment is as follows: S1, the copper powder and the tungsten powder are put into a ball mill tank, and two copper balls with diameters of 7 mm and 3 mm are added as grinding media, wherein the mass ratio of the copper powder to the tungsten powder is 5:1, and the mass ratio of the large ball to the small ball is 2:1, then high-purity argon with a purity of ≥99.9% is filled into the ball mill tank and sealed, and the ball milling treatment is carried out at a speed of 50 rpm for 8 h to fully mix the powders, and a mixed powder is obtained; the mass fraction of the tungsten powder in the mixed powder is 7%; The purity of the copper powder is ≥99.9%, and the particle size is 1 µm ~3 µm; the purity of the tungsten powder is ≥99.9%, and the particle size is 20 nm~100 nm; S2, sintering: the mixed powder obtained in S1 is loaded into a graphite mold, and the graphite mold is placed into an FHP-828 rapid hot-pressing sintering furnace, and discharge plasma sintering is carried out under the condition that the vacuum degree is <1×10 -3 Pa, and a cylindrical copper-tungsten composite material after sintering with a size of about 30 mm (diameter) × 15 mm (height) is obtained; The conditions of the discharge plasma sintering are as follows: first, the longitudinal pressure is increased to 25 MPa and maintained for 2 min; then, the temperature is increased from room temperature to 650℃ at a rate of 100℃ / min, and the temperature is maintained for 30 min under the condition that the pressure is 50 MPa; then, the temperature is increased to 950℃ at a rate of 100℃ / min, and the temperature is maintained for 20 min under the condition that the pressure is 50 MPa; then, the temperature is decreased to 650℃ at a rate of 10℃ / min, and the sintering is ended when the pressure is 50 MPa, the mold is cooled to room temperature with the furnace, and the longitudinal pressure is decreased to 5 MPa; the obtained copper-tungsten composite material after sintering has a high density of 98.5%; S3, low-temperature dynamic plastic deformation: the copper-tungsten composite material after sintering obtained in S2 is subjected to wire cutting, and is cut into a cylindrical sample with a size of 10 mm in diameter and 12 mm in height, and then is subjected to dynamic plastic deformation, and is soaked in liquid nitrogen at a temperature of -196℃ for 10 min before and after each dynamic plastic deformation to completely cool the inside, and finally a large number of nanotwin structures are generated in the matrix, and the plate material exhibits uniform nanotwin structures from the surface layer to the middle layer, and a copper-tungsten composite material after dynamic plastic deformation is obtained; The specific method of the low-temperature dynamic plastic deformation is: adopting multi-pass dynamic impact loading, a total of 7 passes, the strain rate corresponding to the high strain rate dynamic load is not less than 10 2 s -1 , and the total deformation (thickness reduction) is about 75%; In this embodiment, the sample is subjected to severe plastic deformation through multi-pass dynamic impact loading, and the thickness of the final sample is reduced to about 3 mm, the thickness reduction is about 75%, and a bulk sheet-shaped copper-tungsten composite material with a diameter of about 25 mm is formed, i.e., the copper-tungsten composite material after dynamic plastic deformation; S4, annealing treatment: under a protective atmosphere (high-purity argon with a purity of ≥99.9%), the copper-tungsten composite material after dynamic plastic deformation obtained in S3 is subjected to annealing treatment at a temperature of 350℃ for 10 min, and then naturally cooled to room temperature to obtain a high-strength copper-tungsten composite material with a nano-twin structure.

[0030] The high-strength copper-tungsten composite material with a nano-twin structure prepared in this embodiment is subjected to mechanical property testing, and the test results show that the tensile strength of the material at room temperature is 581 MPa, the yield strength is 563 MPa, the elongation is 11%, and the electrical conductivity is 75%, which exhibits good strength and plasticity matching characteristics and good electrical conductivity.

[0031] Embodiment 3 The plastic deformation method for inducing nano-twins to improve the strength of the copper-tungsten composite material in this embodiment is as follows: S1, the copper powder and tungsten powder are put into a ball mill jar, and two copper balls with diameters of 7 mm and 3 mm are added as grinding media, wherein the mass ratio of the ball powder is 5:1, and the mass ratio of the large ball to the small ball is 2:1, then high-purity argon with a purity of ≥99.9% is filled into the ball mill jar and sealed, and the ball milling treatment is carried out at a speed of 70 rpm for 7 h to fully mix the powders, and a mixed powder is obtained; the mass fraction of tungsten powder in the mixed powder is 10%; The purity of the copper powder is ≥99.9%, and the particle size is 1 µm ~3 µm; the purity of the tungsten powder is ≥99.9%, and the particle size is 20 nm~100 nm; S2, sintering: the mixed powder obtained in S1 is loaded into a graphite mold, and the graphite mold is placed in an FHP-828 rapid hot-pressing sintering furnace, and discharge plasma sintering is carried out under the condition that the vacuum degree is <1×10 -3 Pa, and a cylindrical copper-tungsten composite material after sintering with a size of about 30 mm (diameter) × 15 mm (height) is obtained; The conditions of the spark plasma sintering are: first, the longitudinal pressure is increased to 25 MPa and maintained for 2 min; then, the temperature is increased from room temperature to 680 DEG C at a rate of 100 DEG C / min, and the sintering is performed at a pressure of 50 MPa for 20 min; then, the temperature is increased to 950 DEG C at a rate of 100 DEG C / min, and the sintering is performed at a pressure of 50 MPa for 15 min; then, the temperature is decreased to 650 DEG C at a rate of 10 DEG C / min, and the sintering is ended at a pressure of 50 MPa, and the mold is cooled to room temperature in the furnace, and the pressure is reduced to 5 MPa; the obtained sintered copper-tungsten composite material has a high density of 98.3%; S3, low-temperature dynamic plastic deformation: the sintered copper-tungsten composite material obtained in S2 is cut by wire cutting to form a cylindrical sample with a size of 10 mm in diameter and 12 mm in height, and then dynamic plastic deformation is performed; before and after each dynamic plastic deformation, the sample is immersed in liquid nitrogen at a temperature of -196 DEG C for 8 min for complete cooling, and finally a large number of nanotwin structures are generated in the matrix, so that the plate material exhibits uniform nanotwin structures from the surface layer to the intermediate layer, and a dynamic plastic deformation copper-tungsten composite material is obtained; The specific method of the low-temperature dynamic plastic deformation is: multi-pass dynamic impact loading is adopted, a total of 8 passes, and the strain rate corresponding to the high strain rate dynamic load is not less than 10 2 s -1 , and the total deformation is about 80%; The thickness reduction of the low-temperature dynamic plastic deformation copper-tungsten composite material is greater than 70%; In this embodiment, the sample is subjected to severe plastic deformation through multi-pass dynamic impact loading, and the thickness of the sample is finally reduced to about 2.5 mm, the thickness reduction is about 80%, and a bulk piece-shaped copper-tungsten composite material with a diameter of about 25 mm, i.e., a dynamic plastic deformation copper-tungsten composite material, is formed; S4, annealing treatment: the dynamic plastic deformation copper-tungsten composite material obtained in S3 is subjected to annealing treatment at a temperature of 300 DEG C for 15 min in a protective atmosphere (high-purity argon gas with a purity of greater than or equal to 99.9%), and then naturally cooled to room temperature to obtain a high-strength copper-tungsten composite material with a nanotwin structure.

[0032] The high-strength copper-tungsten composite material with a nanotwin structure prepared in this embodiment is subjected to mechanical property testing, and the test results show that the tensile strength of the material at room temperature is 595 MPa, the yield strength is 589 MPa, the elongation is 10.5%, and the electrical conductivity is 73%, which exhibits good strength and plasticity matching characteristics and good electrical conductivity.

[0033] The above merely describes preferred embodiments of the present application, and is not intended to limit the present application. Any simple modification, change and equivalent variation of the above embodiments according to the technical essence of the present application are still within the protection scope of the technical scheme of the present application.

Claims

1. A method for inducing nanotwinning to enhance the strength of a copper-tungsten composite material by plastic deformation, characterized by, The method comprises the following steps: S1, ball milling copper powder and tungsten powder in a protective atmosphere to obtain a mixed powder; S2, sintering: discharging plasma sintering the mixed powder obtained in S1 to obtain a sintered copper-tungsten composite material; The discharging plasma sintering condition is: first, increasing the longitudinal pressure to 25 MPa and maintaining for 2 min; then, increasing the temperature from room temperature to 650-700℃ at a rate of 100℃ / min, maintaining for 15-30 min under the condition of longitudinal pressure of 50 MPa; then, increasing the temperature to 950℃ at a rate of 100℃ / min, maintaining for 5-20 min under the condition of longitudinal pressure of 50 MPa; then, decreasing the temperature to 550-600℃ at a rate of 10℃ / min, ending the sintering under the condition of longitudinal pressure of 50 MPa, and cooling to room temperature in the furnace, and decreasing the longitudinal pressure to 5 MPa; S3, low-temperature dynamic plastic deformation: dynamic plastic deformation of the sintered copper-tungsten composite material obtained in S2, and soaking in liquid nitrogen for 5-10 min before and after each dynamic plastic deformation to generate nanotwin structure in the matrix to obtain a dynamic plastic deformation copper-tungsten composite material; S4, annealing treatment: annealing treatment of the dynamic plastic deformation copper-tungsten composite material obtained in S3 under the condition of temperature of 200-350℃ in a protective atmosphere for 10-30 min, and then naturally cooling to room temperature to obtain a high-strength copper-tungsten composite material with nanotwin structure.

2. The method of claim 1, wherein the plastic deformation is performed by one of rolling, extrusion, and drawing. The purity of the copper powder in S1 is ≥99.9%, and the particle size is 1-3 µm; the purity of the tungsten powder is ≥99.9%, and the particle size is 20-100 nm.

3. The method of claim 1, wherein the plastic deformation is performed by one of rolling, extrusion, and drawing. The protective atmosphere in S1 is high-purity argon with purity ≥99.9%; the ball milling condition is: ball powder mass ratio of 5:1, rotation speed of 50-80 rpm, and ball milling time of 6-8 h; the grinding ball is a copper ball.

4. The method of claim 3, wherein the plastic deformation is performed by one of rolling, extrusion, and drawing. The copper ball is a mixture of two kinds of copper balls with diameters of 7 mm and 3 mm in a mass ratio of 2:

1.

5. The method of claim 1, wherein the plastic deformation is performed by one of rolling, extrusion, and drawing. The mass fraction of tungsten powder in the mixed powder in S1 is 5-10%.

6. The method of claim 1, wherein the plastic deformation is performed by one of rolling, extrusion, and drawing. The vacuum degree of the spark plasma sintering in S2 is <1x10 -3 Pa.

7. The method of claim 1, wherein the plastic deformation is performed by one of rolling, extrusion, and drawing. The specific method of the low-temperature dynamic plastic deformation in S3 is: multi-pass dynamic impact loading to a cumulative total down pressure of >70%.

8. The method of claim 7, wherein the plastic deformation is performed by one of rolling, extrusion, and drawing. The high strain rate dynamic load corresponding to the multi-pass dynamic impact loading is not less than 10 2 s -1 .

9. The method of claim 1, wherein the plastic deformation is performed by one of rolling, extrusion, and drawing. The protective atmosphere in S4 is high-purity argon with purity ≥99.9%.

10. The method of claim 1, wherein the plastic deformation is performed by one of rolling, extrusion, and drawing. The high-strength copper-tungsten composite material with nanotwin structure in S4 has an average tensile strength of >500 MPa at room temperature, a yield strength of >450 MPa, and an elongation of >10%.

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