A method for preparing a high-strength high-toughness high-conductivity copper material with coherent nano precipitates

Abstract

The application relates to the field of advanced materials and processing thereof, in particular to a preparation method of a coherent nano-precipitation high-strength high-toughness high-conductivity copper material, which is composed of Cr: 0.2-0.6%, Zr: 0.01-0.05% and the rest of Cu and inevitable impurities. The preparation method comprises smelting, homogenization treatment, blooming, solid solution quenching treatment, primary cold deformation, short-time aging pretreatment, secondary cold deformation and low-temperature aging treatment. Through the method, two kinds of high-density coherent nano-precipitation ultra-fine grain microstructures can be obtained, and the obtained copper alloy plate has high strength, high conductivity and high plasticity. Compared with the prior art, the alloy composition adopted by the application is simple and low in cost, and the obtained copper material has obvious advantages in conductivity and plasticity. Meanwhile, the preparation process adopted by the application is easy to implement and can be used for industrialized preparation of large-size bulk high-performance copper material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of copper alloy material processing, and particularly relates to a preparation method of a coherent nano-precipitation high-strength high-toughness high-conductivity copper material. BACKGROUND

[0002] High-strength conductive copper alloy is one of the most important components of high-performance copper alloys. According to the strength and conductivity level, it can be mainly divided into two categories: high-strength high-conductivity copper alloy (strength higher than 600 MPa, conductivity higher than 60% IACS) and high-elasticity conductive copper alloy (strength higher than 1.0 GPa, conductivity higher than 10% IACS). Among them, high-strength high-conductivity copper alloy is widely used in a large number of emerging industries and technologies, and is the basic material in the fields of 450 km / h high-speed rail contact line, super-large integrated circuit lead frame and high-level electrical components. Due to the rapid development of the related industry volume and the rapid progress of technology, the demand for the development of new copper materials and the improvement of the organization and performance is very urgent. The high-strength high-conductivity copper alloy that has been widely used mainly includes Cu-Fe-P, Cu-Ni-Si and Cu-Cr-Zr three systems. The early high-strength high-conductivity copper alloy mainly refers to Cu-Fe-P alloy. The conductive performance of this kind of alloy is good, and the low alloy system can reach 80~90% ICAS, but the strength is low, generally in 300~400 MPa, and it is difficult to exceed 600 MPa under the condition of high alloy content system and optimized processing, so the use scene is limited. The high-strength high-conductivity bulk copper material that is widely used at present mainly includes Cu-Ni-Si and Cu-Cr-Zr alloy. Among them, Cu-Ni-Si alloy can achieve high strength, and can reach 800~1000 MPa after optimization, but the conductivity is relatively low compared with Cu-Ag, Cu-Fe-P and Cu-Cr-Zr system, generally only in 40~60% ICAS, and usually only about 20% ICAS under the extremely high strength close to 1000 MPa. Since the most important use scene of high-strength high-conductivity copper alloy is the new generation of integrated circuit lead frame, the performance requirements of copper material are that the strength is more than 600 MPa, the conductivity is not less than 80% ICAS, and good toughness and plasticity are also required to meet the processing requirements. The above two kinds of alloys are difficult to meet the related requirements.

[0003] Currently, the Cu-Cr-Zr alloy has the best comprehensive performance of strength and electrical conductivity. Through special plastic deformation processing and heat treatment, the electrical conductivity of the material can be close to 80% I CAS, and the tensile strength can reach a level close to 600 MPa or even higher. However, the existing technologies have problems such as complex processing method, limited sample size, and difficulty in industrial production. At the same time, the high-strength Cu-Cr-Zr alloy prepared by the existing technologies often has the problem of insufficient toughness and plasticity. Sun et al. prepared ultra-high strength small-size samples by low-temperature dynamic strong plastic deformation method based on Cu-1.2Cr-0.3Zr alloy, and the tensile strength can exceed 700 MPa, and the electrical conductivity is increased to 78.7% I CAS. L. X. Sun, N. R. Tao, K. Lu. Scripta Materialia, 2015, 99: 73-6 Vinogradov et al. prepared a low-alloy Cu-0.44Cr-0.2Zr alloy with a tensile strength of 700 MPa and an electrical conductivity of 80% I CAS by equal-channel angular extrusion and low-temperature aging, but the preparation method is relatively complex, and the plasticity is only 1.1%. A. Vinogradov, V. Patlan, Y. Suzuki, K. Kitagawa, V. Kopylov, Acta materialia 50(7) (2002) 1639-1651 Patent CN110055479A discloses an 800MPa-grade high-conductivity copper-chromium-zirconium alloy and a preparation method thereof, which adopts equal-channel angular extrusion and ultra-large deformation low-temperature rolling, etc. The required deformation amount is large, which is difficult to apply to industrial production, and the prepared material has poor plasticity and is not easy to process. Patent CN116083827A discloses a method for preparing a high-strength high-conductivity nano-heterogeneous copper-chromium-zirconium alloy by multi-stage deformation and multi-stage aging. This method also needs to use special deformation methods such as equal-channel angular extrusion and deformation below room temperature, which is not conducive to processing, and the plasticity of the prepared material is not considered. Patent CN110835699A discloses a new type of micro-alloyed Cu-Cr-Zr alloy, which can obtain good performance by using a relatively conventional processing method, but the alloy contains Mg, Si, Fe, Ti, La, B, Ca and other alloying elements, and needs to be cooled in a hydrogen-nitrogen mixed atmosphere, which is difficult to implement when producing bulk materials. At the same time, this method also does not pay attention to the toughness and plasticity of the prepared material. SUMMARY

[0004] The purpose of the present application is to overcome the defects of the existing methods and provide a preparation method of coherent nano-precipitation high-strength high-toughness high-conductivity copper material. The present application adopts a low-alloy design concept, reduces the content of Cr and Zr elements compared with other commercial alloys, does not add other alloying elements, and obtains multi-scale nano-coherent precipitates in the alloy through an adaptive multi-step cold rolling-aging process, realizes the simultaneous improvement of strength, electrical conductivity, plasticity and work hardening ability, and has the characteristics of simple production process, low alloy cost, easy industrial production and excellent comprehensive performance.

[0005] The object of the present application can be achieved by the following technical solution: a preparation method of a coherent nano-precipitation high-strength and high-ductility high-conductivity copper material, mainly comprising the following process steps of smelting, homogenization treatment and blooming, solid solution heat preservation, primary cold deformation treatment, primary aging pretreatment, secondary strong cold deformation treatment, secondary aging treatment, and the like, and the specific steps are as follows:

[0006] (1) Smelting: according to the copper alloy component, a certain amount of pure copper, copper-chromium intermediate alloy and copper-zirconium intermediate alloy are added in a non-vacuum induction furnace, and smelting is uniformly stirred to form an ingot;

[0007] (2) Homogenization treatment and blooming: the ingot obtained in step (1) is kept at 920-960℃ for not less than 4.0h to eliminate component segregation and obtain a microstructure uniform cast blank, which is immediately bloomed in a hot forging manner after being discharged, and then air-cooled to room temperature;

[0008] (3) Solid solution heat preservation: the forged material obtained in step (2) is kept at 930-950℃ for 10.0-15.0h to ensure that the Cr and Zr elements precipitated in the homogenization and blooming treatment process are all dissolved into the matrix, and then the forged material is water-cooled to room temperature;

[0009] (4) Primary cold deformation treatment: the forged material obtained in step (3) is subjected to multi-pass rolling at room temperature, and the total deformation is not more than 40%;

[0010] (5) Primary aging pretreatment: the plate obtained in step (4) is subjected to short-time aging heat treatment at 450-480℃, and the holding time is 5-10min, and then water-cooled to room temperature;

[0011] (6) Secondary strong cold deformation treatment: the plate obtained in step (5) is subjected to multi-pass synchronous rolling at room temperature, and the total deformation is 80-95%;

[0012] (7) Secondary aging treatment: the plate obtained in step (6) is subjected to aging heat treatment at 350-380℃, and the holding time is 2.0-5.0h, and then air-cooled to room temperature.

[0013] Further, the copper material contains the following components by mass percentage: Cr: 0.2-0.8%, Zr: 0.02-0.08%, and the rest is Cu and unavoidable impurities. Preferably, the component mass percentage is: Cr: 0.2-0.4%, Zr: 0.02-0.04%, and the rest is Cu and unavoidable impurities.

[0014] The alloy design principle of the coherent nano-precipitation strengthened high-strength high-conductivity high-plasticity low-alloy copper material is as follows:

[0015] Compared with dislocations, grain boundaries, vacancies and the like, solid solution atoms are the most important microstructure factors of metal materials affecting the electrical conductivity of alloys. Numerous studies have shown that reducing the total alloy content is the most effective composition design strategy to improve the electrical conductivity of alloys. Therefore, in the alloy disclosed in the present application, the contents of the two main alloying elements Cr and Zr are as low as possible, and no other alloying elements are added. Under such a premise, a processing method suitable for the alloy composition needs to be adopted to as far as possible increase the number density of nano-precipitates, appropriately reduce the size of nano-precipitates, and optimize the interface structure thereof with the matrix, so as to ensure that the prepared material has high electrical conductivity while having excellent comprehensive mechanical properties.

[0016] Further, the order of adding raw materials in the step (1) melting is to add pure copper and copper-chromium intermediate alloy first, and then add copper-zirconium intermediate alloy after the molten body is completely melted, and the content is consistent with the designed content.

[0017] Further, the rolling adopted in the step (4) primary cold deformation treatment is multi-pass asynchronous rolling, the linear speed ratio of the upper and lower surfaces of the plate is 1.2-2.5:1, and the deformation amount of each pass is 3-5%; the rolling adopted in the step (6) secondary strong cold deformation treatment is synchronous rolling, the diameter and rotating speed of the roller are the same, the deformation amount of each pass is not less than 4%, and the rolling is not less than 20 passes.

[0018] Further, the thickness of the forged material obtained by the hot forging in the step (2) is 30-40 mm.

[0019] Further, the microstructure of the material after the step (5) primary cold deformation and aging pretreatment is ultra-fine grain matrix structure and high-density dislocation structure and Cr-rich nano-precursor dispersedly distributed on the matrix. The average grain size of the matrix structure is 200-500 nm, and the particle size of the nano-precursor is 0.5-4.0 nm.

[0020] Further, the yield strength of the copper material prepared by the present application is not less than 600 MPa, the tensile strength is not less than 650 MPa, the fracture elongation is not less than 9.0%, and the electrical conductivity is not less than 85% IACS. The microstructure of the copper material includes an incomplete recrystallized ultra-fine grain matrix structure and two high-density nano-precipitates with different particle sizes dispersedly distributed on the matrix. The grain size of the ultra-fine grain matrix structure is 200-800 nm. The two high-density nano-precipitates with different particle sizes are: Cu5Zr-shaped Cr-rich precipitates with a particle size in the range of 10-100 nm, which maintain a semi-coherent relationship with the ultra-fine grain matrix structure; and FCC structure Cu and Cr-rich precipitates with a Cu and Cr atomic ratio of about 3.0-5.0 and a particle size of less than 10 nm, which maintain a complete coherent relationship with the ultra-fine grain matrix structure.

[0021] The preparation process path adopted in the present application is closely adapted to the composition of the alloy. By melting, high-temperature solid solution, and two-stage step-by-step rolling and aging, a large number of nanometer precipitates with high-density coherent interfaces with the matrix can be obtained in the alloy, which is the most important microstructure factor for the copper material prepared by the present application to simultaneously have high strength, high electrical conductivity and high plasticity. In the melting process, since the melting point of zirconium element is relatively high and the element content is relatively low, copper-chromium and copper-zirconium intermediate alloys are sequentially added in the melting process to ensure that the alloying elements are uniformly dispersed. The importance of the used two-stage aging process lies in that the first stage of multi-pass asynchronous cold rolling treatment can introduce more defects in the matrix, and the shear stress brought by asynchronous rolling can make the distribution of these high-density defects more uniform. The first step of short-time aging treatment can promote the rapid nucleation of a large number of precursors near the uniform high-density defects, and the 5-10 min holding time avoids the excessive growth of these precursors. In the second stage of cold deformation, a strong deformation amount can introduce a higher density of defects in the matrix. The hard nanometer precursors introduced in the first stage can also hinder dislocation movement during deformation, intensify the deformation effect, and thus introduce a higher density of dislocation organization. In the subsequent aging and precipitation process, the high-density defects and deformation energy brought by the second stage of rolling can improve the nucleation rate of precipitation, and thus reduce the average particle size of the nanometer precipitates through the competitive growth mechanism, which is beneficial to obtaining high-coherent nanometer precipitates.

[0022] A feature of the copper material prepared by the present application is that a high-density ultra-fine coherent nanometer precipitate can be obtained, which is also the implementation effect of the alloy composition design strategy and the processing technology. The low lattice mismatch degree and small particle size of the nanometer precipitate with the matrix are effective reasons for achieving coherence. In the alloy used in the present application, the composition of Cr and Zr is as low as possible. From the perspective of thermodynamics, Cu, Cr nanometer precipitates rich in Cu will reach an energy priority state. Therefore, in the present alloy, the proportion of Cu atoms in the nanometer precipitate below 10 nm is 60-80%, and the proportion of Cr atoms is relatively small, and the 10-100 nm Cu5Zr phase is rich in Cu. Therefore, the lattice mismatch degree of the nanometer precipitate with the pure Cu matrix is low. After two-stage cold rolling and aging treatment, a high-density nanometer nucleation point is introduced in the matrix, and the average grain size of the precipitate can be reduced through the competitive growth mechanism, which is beneficial to the formation of coherent structure at the interface between the precipitate and the matrix. The high-density coherent nanometer precipitate is the most important factor for the material prepared by the present application to have excellent plasticity.

[0023] Compared with the prior art, the present application has the following advantages:

[0024] 1、The prepared alloy has very excellent comprehensive performance, the yield strength can exceed 600MPa, the tensile strength can exceed 650MPa, and the conductivity can reach 90%IACS, so that the use demand of a new generation of lead frame material can be met, and there is a surplus in the conductivity, which can support the development of new generation technology and equipment. More importantly, compared with other alloys of the same system with strength above 600MPa and elongation at break only 1-2%, the alloy prepared by the application also has plasticity close to 10%, and the plate can be subjected to various plastic deformation processing, realizing complex forming, so that the application scene of the material is greatly widened.

[0025] 2、The alloy composition adopted in the application is simple, compared with the alloys disclosed in the same kind of technology, the content of Cr and Zr elements is very low, and the content of Zr element is only about 0.03%, so that the alloy composition can make the melting process easier to realize uniform dispersion, and the alloy cost is very low. In addition, the alloy does not contain other elements, the alloy cost is very low, the melting technology is simple, and many production and processing units can also entrust the upstream unit to customize the alloy, and then implement the processing technology to realize excellent comprehensive performance.

[0026] 3、The processing and preparation means adopted in the application is relatively simple, compared with the special processing means such as equal channel angular extrusion, low temperature dynamic deformation and low temperature strong deformation rolling used in other similar technologies, the room temperature rolling means adopted in the application is easier to implement and has lower production cost, and is suitable for producing large block materials and is easy to put into industrialized production. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is the process route map adopted in the application;

[0028] Figure 2 It is the ultra-fine grain microstructure of the high strength and toughness high conductivity copper material prepared in the application;

[0029] Figure 3 It is the high density coherent nanometer precipitation (TEM dark field image) of the high strength and toughness high conductivity copper material prepared in the application;

[0030] Figure 4 It is the APT characterization result of the high density Cr-rich nanometer precipitation in the high strength and toughness high conductivity copper material prepared in the application. DETAILED DESCRIPTION

[0031] The application will be described in detail below in combination with the drawings and examples. It should be pointed out that those skilled in the art can make some changes and improvements without departing from the concept of the application. These all belong to the protection scope of the application.

[0032] Example 1

[0033] A preparation method of a high-strength high-toughness high-conductivity copper material with coherent nano precipitation, as shown in Figure 1 The steps are as follows:

[0034] Step one, non-vacuum induction melting: the chemical composition of the alloy is as follows: Cr: 0.2%, Zr: 0.04%, the rest is Cu and inevitable impurities; according to the above composition, a certain amount of pure copper, copper-chromium intermediate alloy and copper-zirconium intermediate alloy are added in a non-vacuum induction furnace, and the molten metal is stirred uniformly and cast into an ingot;

[0035] Step two, homogenization treatment and breakdown: the ingot obtained in step one is subjected to homogenization treatment at 920℃ for 6.0h to eliminate composition segregation and obtain a cast blank with uniform structure and properties, and then hot working breakdown is carried out to eliminate casting defects and obtain a plate blank with a final thickness of 40mm;

[0036] Step three, solution heat preservation: the forged material obtained in step two is preserved at 930℃ for 15.0h to ensure that all the Cr and Zr elements precipitated in the homogenization and breakdown treatment processes are dissolved into the matrix, and then the forged material is water-cooled to room temperature;

[0037] Step four, primary cold deformation treatment: the forged material obtained in step three is subjected to multi-pass asynchronous rolling at room temperature, the line speed ratio of the upper and lower surfaces of the plate is 1.5:1, the deformation amount of each pass is 5%, and the total deformation amount is 20%;

[0038] Step five, primary aging pretreatment: the plate obtained in step four is subjected to short-time aging heat treatment at 450℃ for 10min, and then water-cooled to room temperature;

[0039] Step six, secondary strong cold deformation treatment: the plate obtained in step five is subjected to multi-pass synchronous rolling at room temperature, the deformation amount of each pass is 4%, and the total deformation amount is 80%;

[0040] Step seven, secondary aging treatment: the plate obtained in step six is subjected to aging heat treatment at 350℃ for 5.0h, and air-cooled to room temperature. Figure 2 The electron microscope photograph of the coherent nano precipitation strengthened high-strength high-conductivity high-plasticity low-alloy copper material, the microstructure of the prepared plate is composed of an ultra-fine grain matrix structure with incomplete recrystallization and a high-density nano precipitate phase with two different particle sizes dispersed in the matrix, the yield strength of the plate is 620MPa, the tensile strength is 675MPa, the elongation is 9.5%, the electrical conductivity is 87%IACS, and the average grain size of the ultra-fine grain matrix is 400~500nm. As shown in Figure 3Cu5Zr shaped Cr-rich precipitates, with particle size in the range of 10-100 nm; FCC structure Cu, Cr-rich precipitates, with particle size below 10 nm. These high density coherent nanometer precipitates are the key to the excellent plasticity of the material produced by the present application.

[0041] Example 2

[0042] A method for preparing a coherent nanometer precipitate high strength and toughness high conductivity copper material, the steps are as follows:

[0043] Step one, non-vacuum induction melting: the chemical composition of the alloy is as follows: Cr: 0.2%, Zr: 0.02%, the rest is Cu and inevitable impurities; according to the above composition, a certain amount of pure copper, copper chromium intermediate alloy and copper zirconium intermediate alloy are added in a non-vacuum induction furnace, and the molten metal is stirred uniformly and cast into ingots;

[0044] Step two, homogenization treatment and breakdown: the ingot obtained in step one is subjected to homogenization treatment at 960℃ for 4.0h to eliminate composition segregation, and a uniform structure and performance of the cast blank is obtained, and then hot working is carried out to eliminate casting defects and obtain a plate blank with a final thickness of 30mm;

[0045] Step three, solution heat preservation: the forged material obtained in step two is heat treated at 950℃ for 10.0h to ensure that the Cr and Zr elements precipitated in the homogenization and breakdown treatment process are completely dissolved into the matrix, and then the forged material is water cooled to room temperature;

[0046] Step four, primary cold deformation treatment: the forged material obtained in step three is subjected to multi-pass asynchronous rolling at room temperature, the line speed ratio of the upper and lower surfaces of the plate is 1.5:1, the deformation amount of each pass is 5%, and the total deformation amount is 20%;

[0047] Step five, primary aging pretreatment: the plate obtained in step four is subjected to short-time aging heat treatment at 480℃ for 5min, and then water cooled to room temperature;

[0048] Step six, secondary strong cold deformation treatment: the plate obtained in step five is subjected to multi-pass synchronous rolling at room temperature, with a deformation amount of 4% per pass and a total deformation amount of 80%;

[0049] Step seven, secondary aging treatment: the plate obtained in step six is subjected to aging heat treatment at 380℃ for 2.0h, and air cooled to room temperature. The microstructure of the prepared plate is composed of a microstructure of incomplete recrystallized ultra-fine grain matrix and two different particle sizes of high-density nanometer precipitates dispersed on the matrix. The yield strength of the plate is 610MPa, the tensile strength is 655MPa, the elongation is 11.2%, and the electrical conductivity is 92% IACS.

[0050] Example 3

[0051] A method for preparing a coherent nano-precipitation high strength and toughness high conductivity copper material, the steps of which are as follows:

[0052] Step one, non-vacuum induction melting: the chemical composition of the alloy is as follows: Cr: 0.4%, Zr: 0.04%, the rest being Cu and unavoidable impurities; according to the above composition, a certain amount of pure copper, copper-chromium intermediate alloy and copper-zirconium intermediate alloy are added in a non-vacuum induction furnace, and the melt is stirred uniformly and cast into ingots;

[0053] Step two, homogenization treatment and breakdown: the ingots obtained in step one are subjected to homogenization treatment at 950℃ for 5.0h to eliminate composition segregation, and a cast blank with uniform structure and properties is obtained, followed by hot working and breakdown to eliminate casting defects and obtain a plate blank with a final thickness of 30mm;

[0054] Step three, solution heat preservation: the forged material obtained in step two is heat treated at 950℃ for 10.0h to ensure that the Cr and Zr elements precipitated in the homogenization and breakdown treatment processes are completely dissolved into the matrix, and then the forged material is water cooled to room temperature;

[0055] Step four, primary cold deformation treatment: the forged material obtained in step three is subjected to multi-pass asynchronous rolling at room temperature, the line speed ratio of the upper and lower surfaces of the plate is 2:1, the deformation amount of each pass is 5%, and the total deformation amount is 30%;

[0056] Step five, primary aging pretreatment: the plate obtained in step four is subjected to short-time aging heat treatment at 480℃ for 5min, and then water cooled to room temperature;

[0057] Step six, secondary strong cold deformation treatment: the plate obtained in step five is subjected to multi-pass synchronous rolling at room temperature, the deformation amount of each pass is 4%, and the total deformation amount is 92%;

[0058] Step seven, secondary aging treatment: the plate obtained in step six is subjected to aging heat treatment at 380℃ for 2.0h, and air cooled to room temperature. The prepared plate has a microstructure composed of a microstructure of incomplete recrystallized ultra-fine grain matrix and a high-density nano-precipitation phase with two different particle sizes dispersed in the matrix. The yield strength of the plate is 635MPa, the tensile strength is 687MPa, the elongation is 9.2%, and the electrical conductivity is 86%IACS.

[0059] Example 4

[0060] A method for preparing a coherent nano-precipitation high strength and toughness high conductivity copper material, the steps of which are as follows:

[0061] Step one, step two, step three, step four process is same as example 3;

[0062] Step five, the first aging pretreatment heat treatment temperature is adjusted to 450℃, the holding time is 5min, and water cooling to the greenhouse;

[0063] Step six, the second strong cold deformation treatment process is adjusted, the deformation amount of each pass is 4.0%, and the total deformation amount is 80%;

[0064] Step seven process is same as example 3; the prepared microstructure of the obtained plate is composed of ultra-fine grain matrix structure and high-density nano-precipitated phase with two different particle sizes dispersed on the matrix, the yield strength of the plate is 615MPa, the tensile strength is 658MPa, the elongation at break is 11.0%, and the electrical conductivity is 90%IACS.

[0065] Example 5

[0066] A method for preparing a coherent nano-precipitated high-strength and high-toughness high-conductivity copper material, comprising the following steps:

[0067] Step one, non-vacuum induction melting: the chemical composition of the alloy is as follows: Cr: 0.4%, Zr: 0.02%, the rest is Cu and inevitable impurities; according to the above composition, a certain amount of pure copper, copper-chromium intermediate alloy and copper-zirconium intermediate alloy are added in a non-vacuum induction furnace, and the molten copper is stirred uniformly and cast into ingots;

[0068] Step two, homogenization treatment and breakdown: the ingot obtained in step one is subjected to homogenization treatment at 950℃ for 5.0h to eliminate composition segregation, and a uniform structure and performance of the cast blank is obtained, and then hot working is carried out to eliminate casting defects, and a plate blank with a final thickness of 40mm is obtained;

[0069] Step three, solution heat preservation: the forged material obtained in step two is heated at 930℃ for 15.0h to ensure that the Cr and Zr elements precipitated in the homogenization and breakdown treatment process are completely dissolved into the matrix, and then the forged material is water cooled to room temperature;

[0070] Step four, first cold deformation treatment: the forged material obtained in step three is subjected to multi-pass asynchronous rolling at room temperature, the linear speed ratio of the upper and lower surfaces of the plate is 2:1, the deformation amount of each pass is 5%, and the total deformation amount is 25%;

[0071] Step five, first aging pretreatment: the plate obtained in step four is subjected to short-time aging heat treatment at 450℃, and the holding time is 10min, and then water cooled to room temperature;

[0072] Step six, secondary strong cold deformation treatment: the plate obtained in step five is subjected to multi-pass synchronous rolling at room temperature, and the deformation amount of each pass is 4%, and the total deformation amount is 88%;

[0073] Step seven, secondary aging treatment: the plate obtained in step six is subjected to aging heat treatment at 350°C, and the holding time is 5.0h, and air cooling is performed until the temperature in the room. The prepared plate is composed of a microstructure of an ultra-fine grain matrix organization and a high-density nano-precipitated phase with two different particle sizes dispersed on the matrix. The yield strength of the plate is 632MPa, the tensile strength is 680MPa, the elongation at break is 9.4%, and the electrical conductivity is 86%IACS.

[0074] Example 6

[0075] A method for preparing a coherent nano-precipitated high-strength and high-ductility high-conductivity copper material, comprising the following steps:

[0076] Step one, non-vacuum induction melting: the chemical composition of the alloy is as follows: Cr: 0.3%, Zr: 0.04%, and the rest is Cu and inevitable impurities; according to the above composition, a certain amount of pure copper, copper-chromium intermediate alloy and copper-zirconium intermediate alloy are added in a non-vacuum induction furnace, and the molten metal is stirred uniformly and cast into an ingot;

[0077] Step two, homogenization treatment and breakdown: the ingot obtained in step one is subjected to homogenization treatment at 920°C for 6.0h to eliminate composition segregation, and a cast blank with uniform organization and performance is obtained, and then hot working is performed to eliminate casting defects, and a plate blank with a final thickness of 40mm is obtained;

[0078] Step three, solution heat preservation: the forged material obtained in step two is preserved at 950°C for 10.0h to ensure that the Cr and Zr elements precipitated in the homogenization and breakdown treatment processes are completely dissolved into the matrix, and then the forged material is water-cooled to room temperature;

[0079] Step four, primary cold deformation treatment: the forged material obtained in step three is subjected to multi-pass asynchronous rolling at room temperature, and the linear speed ratio of the upper and lower surfaces of the plate is 2:1, the deformation amount of each pass is 5%, and the total deformation amount is 20%;

[0080] Step five, primary aging pretreatment: the plate obtained in step four is subjected to short-time aging heat treatment at 480°C, and the holding time is 5min, and then water-cooled to room temperature;

[0081] Step six, secondary strong cold deformation treatment: the plate obtained in step five is subjected to multi-pass synchronous rolling at room temperature, and the deformation amount of each pass is 4%, and the total deformation amount is 80%;

[0082] Step seven, secondary aging treatment: the plate obtained in step six is aged at 380℃, the holding time is 2.0h, and air cooling is performed until the temperature of the room. The microstructure of the prepared plate is composed of ultra-fine grain matrix structure with incomplete recrystallization and high-density nano-precipitates with two different particle sizes dispersed in the matrix, the yield strength of the plate is 617MPa, the tensile strength is 669MPa, the elongation at break is 10.4%, and the electrical conductivity is 89%IACS.

[0083] Example 7

[0084] A method for preparing a coherent nano-precipitation high strength and toughness high conductivity copper material, the steps are as follows:

[0085] Step one, non-vacuum induction melting: the chemical composition of the alloy is as follows: Cr: 0.3%, Zr: 0.02%, the rest is Cu and inevitable impurities; according to the above composition, a certain amount of pure copper, copper-chromium intermediate alloy and copper-zirconium intermediate alloy are added in a non-vacuum induction furnace, and the molten metal is stirred uniformly and cast into ingots;

[0086] Step two, homogenization treatment and breakdown: the ingot obtained in step one is homogenized at 920℃ for 6.0h to eliminate composition segregation and obtain a cast blank with uniform structure and properties, and then hot working is carried out to eliminate casting defects and obtain a plate blank with a final thickness of 30mm;

[0087] Step three, solution treatment: the forged material obtained in step two is soaked at 930℃ for 15.0h to ensure that the Cr and Zr elements precipitated in the homogenization and breakdown treatment processes are completely dissolved into the matrix, and then the forged material is water cooled to room temperature;

[0088] Step four, primary cold deformation treatment: the forged material obtained in step three is subjected to multi-pass asynchronous rolling at room temperature, the linear speed ratio of the upper and lower surfaces of the plate is 1.8:1, the deformation amount of each pass is 5%, and the total deformation amount is 20%;

[0089] Step five, primary aging pretreatment: the plate obtained in step four is subjected to short-time aging heat treatment at 460℃, the holding time is 8min, and then water cooling is performed to room temperature;

[0090] Step six, secondary strong cold deformation treatment: the plate obtained in step five is subjected to multi-pass synchronous rolling at room temperature, the deformation amount of each pass is 4%, and the total deformation amount is 88%;

[0091] Step 7, Secondary Aging Treatment: The plate obtained in Step 6 is subjected to aging heat treatment at 360℃ for 4.0 hours, followed by air cooling to room temperature. The microstructure of the prepared plate consists of an ultrafine crystalline matrix with incomplete recrystallization and two high-density nano-precipitates of different particle sizes dispersed on the matrix. The yield strength of the plate is 624 MPa, the tensile strength is 670 MPa, the elongation at break is 10.2%, and the electrical conductivity is 88% IACS.

[0092] Example 8

[0093] A method for preparing a coherent nano-precipitated high-strength, high-toughness, and high-conductivity copper material, comprising the following steps:

[0094] Step 1, Non-vacuum induction melting: The chemical composition of the alloy by mass percentage is: Cr: 0.4%, Zr: 0.03%, with the remainder being Cu and unavoidable impurities; according to the above composition, add a certain amount of pure copper, copper-chromium master alloy and copper-zirconium master alloy to a non-vacuum induction furnace, stir and melt evenly, and cast into ingots.

[0095] Step 2, Homogenization and Billet Opening: The ingot obtained in Step 1 is homogenized at 950℃ for 5.0h to eliminate component segregation and obtain a billet with uniform structure and properties. Then, hot working is performed to open the billet to eliminate casting defects and obtain a slab with a final thickness of 40mm.

[0096] Step 3, solution treatment and heat preservation: The forging obtained in step 2 is kept at 950℃ for 10.0h to ensure that all Cr and Zr elements precipitated in the matrix during the homogenization and billet processing are dissolved back into the matrix. Then the forging is cooled to room temperature by water cooling.

[0097] Step 4, Primary Cold Deformation Treatment: The forging obtained in Step 3 is subjected to multi-pass asynchronous rolling at room temperature. The linear speed ratio of the rolls on the upper and lower surfaces of the sheet is 1.8:1, the deformation amount per pass is 5%, and the total deformation amount is 30%.

[0098] Step 5, First-level aging pretreatment: The board obtained in Step 4 is subjected to short-term aging heat treatment at 460℃ for 8 minutes, and then water-cooled to room temperature;

[0099] Step Six, Secondary Intense Cold Deformation Treatment: The sheet obtained in Step Five is subjected to multi-pass synchronous rolling at room temperature, with a deformation amount of 4% per pass and a total deformation amount of 80%.

[0100] Step seven, secondary aging treatment: the plate obtained in step six is aged at 360℃, the holding time is 3.0h, and air cooling is performed until the temperature of the room. The microstructure of the obtained plate consists of an ultra-fine grain matrix structure with incomplete recrystallization and high-density nano-precipitates with two different particle sizes dispersed in the matrix. The yield strength of the plate is 628MPa, the tensile strength is 676MPa, the elongation at break is 9.8%, and the electrical conductivity is 87%IACS.

Claims

1. A method for preparing a coherent nano-precipitated high-strength, high-toughness, and high-conductivity copper material, characterized in that, Includes the following steps: (1) Smelting: According to the composition of copper alloy, a certain amount of pure copper, copper-chromium master alloy and copper-zirconium master alloy are added in a non-vacuum induction furnace, stirred and smelted evenly, and cast into ingots; the mass percentage composition of the raw materials added in the smelting is: Cr: 0.2~0.8%, Zr: 0.02~0.08%, and the remainder is Cu and unavoidable impurities; (2) Homogenization and billet opening: The ingot obtained in step (1) is kept at 920~960℃ for no less than 4.0h to eliminate component segregation and obtain a billet with uniform microstructure. After being taken out of the furnace, it is immediately opened by hot forging and then air-cooled to room temperature. (3) Solution treatment and heat preservation: The forging obtained in step (2) is kept at 930~950℃ for 10.0~15.0h to ensure that all Cr and Zr elements precipitated in the matrix during the homogenization and billet processing are dissolved back into the matrix. Then the forging is cooled to room temperature by water cooling. (4) First-level cold deformation treatment: The forging obtained in step (3) is rolled in multiple passes at room temperature, with a total deformation of no more than 40%; (5) First-level aging pretreatment: The board obtained in step (4) is subjected to short-term aging heat treatment at 450~480℃ for 5~10 minutes, and then cooled to room temperature by water. (6) Secondary severe cold deformation treatment: The plate obtained in step (5) is subjected to multiple passes of synchronous rolling at room temperature, with a total deformation of 80~95%; (7) Secondary aging treatment: The board obtained in step (6) is subjected to aging heat treatment at 350~380℃ for 2.0~5.0h, and then air-cooled to a greenhouse.

2. The method for preparing a coherent nano-precipitated high-strength, high-toughness, and high-conductivity copper material according to claim 1, characterized in that, The mass percentage composition of the raw materials added in the smelting process of step (1) is: Cr: 0.2~0.4%, Zr: 0.02~0.04%.

3. The method for preparing a coherent nano-precipitated high-strength, high-toughness, and high-conductivity copper material according to claim 1, characterized in that, In step (1), the order of adding raw materials during smelting is as follows: first add pure copper and copper-chromium master alloy, and after the melt is completely melted, add copper-zirconium master alloy, the content of which is consistent with the design content.

4. The method for preparing a coherent nano-precipitated high-strength, high-toughness, and high-conductivity copper material according to claim 1, characterized in that, Step (4) The rolling process used for the first-level cold deformation treatment is multi-pass asynchronous rolling, with the linear speed ratio of the rolls on the upper and lower surfaces of the plate being 1.2~2.5:1, and the deformation amount per pass being 3~5%; Step (6) The rolling process used for the second-level intense cold deformation treatment is synchronous rolling, with the same diameter and rotation speed of the rolls, and the deformation amount per pass being not less than 4%, and the rolling process being not less than 20 passes.

5. The method for preparing a coherent nano-precipitated high-strength, high-toughness, and high-conductivity copper material according to claim 1, characterized in that, The thickness of the forging obtained by hot forging in step (2) is 30~40mm.

6. The method for preparing a coherent nano-precipitated high-strength, high-toughness, and high-conductivity copper material according to claim 1, characterized in that, The microstructure of the material after the first-stage cold deformation and aging pretreatment in step (5) is an ultrafine crystalline matrix structure and Cr-rich nano-precursors and high-density dislocation structures dispersed on the matrix; the average grain size of the matrix structure is 200~500nm, and the particle size of the nano-precursors is 0.5~4.0nm.

7. The method for preparing a coherent nano-precipitated high-strength, high-toughness, and high-conductivity copper material according to claim 1, characterized in that, The microstructure of the copper material includes an incompletely recrystallized ultrafine crystalline matrix and two high-density nano-precipitates of different particle sizes dispersed on the matrix.

8. The method for preparing a coherent nano-precipitated high-strength, high-toughness, and high-conductivity copper material according to claim 7, characterized in that, The grain size of the ultrafine crystalline matrix is ​​200~800 nm.

9. The method for preparing a coherent nano-precipitated high-strength, high-toughness, and high-conductivity copper material according to claim 7, characterized in that, The two high-density nano-precipitates with different particle sizes are as follows: Cu5Zr-shaped Cr-rich precipitates, with particle sizes in the range of 10-100 nm, maintain a semi-coherent relationship with the ultrafine-grained matrix; and The FCC structure contains Cu and Cr precipitates with an atomic ratio of Cu to Cr of 3.0 to 5.0 and a particle size of less than 10 nm, which are completely coherent with the ultrafine crystalline matrix.

10. The method for preparing a coherent nano-precipitated high-strength, high-toughness, and high-conductivity copper material according to claim 1, characterized in that: The prepared copper material has a yield strength of not less than 600 MPa, a tensile strength of not less than 650 MPa, an elongation at break of not less than 9.0%, and an electrical conductivity of not less than 85% IACS.

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