A method for simultaneously improving the mechanical properties and electrical conductivity of Cu-Ni-Si-Co copper alloy

Abstract

The present invention discloses a method for simultaneously improving the mechanical properties and electrical conductivity of Cu‑Ni‑Si‑Co copper alloy, and belongs to the technical field of lead frame material production process. The rare earth Cu‑Ni‑Si‑Co alloy described in the present invention contains 1.0-3.5% Ni, 2.0-4.0% Si, 0.1-0.35% Co, 0.01-0.07% La, 0.01-0.07% Ce and 0.01-0.07% Y by mass percentage, with the remainder being copper and some inevitable impurity elements. The present invention is prepared by a cyclic “slow heating-multiple doping-rapid cooling” treatment method. The high-density twinned rare earth Cu‑Ni‑Si‑Co copper alloy obtained by the present invention can effectively improve the strength of C7035 copper alloy while reducing the loss of electrical conductivity. In order to adapt to the future development of integrated circuits, the design and preparation of high-strength and high-conductivity copper alloys have important guiding significance and have very good industrial application prospects.

Description

Technical Field

[0001] The invention relates to a method for simultaneously improving the mechanical properties and electrical conductivity of a Cu-Ni-Si-Co copper alloy, belonging to the technical field of high-strength and high-conductivity copper alloy processes. Background Art

[0002] High-strength conductive copper alloys are not only fundamental materials for economic development, but also key materials used in numerous high-tech fields. They are widely used in industries such as aerospace, microelectronics, rail transportation, and communications. With the development of industry, higher requirements are being placed on the high strength and high conductivity of copper alloys. Cu-Ni-Co-Si alloy (C7035) has the characteristics of high strength (yield 800-850 MPa) and high conductivity (40% IACS-45% IACS), making it a research hotspot for high-strength and high-conductivity materials. However, to adapt to the development of integrated circuits, the strength and conductivity of C7035 need to be further improved.

[0003] Patent CN116287856A discloses a high-strength and high-elasticity quaternary copper-nickel-tin-chromium alloy and its preparation method; the copper alloy is composed of Cu, Ni, Sn, and Cr elements, with the following contents: Ni: 7wt.% to 11wt.%; Sn: 3wt.% to 9wt.%; Cr: 0.3wt.% to 1.0wt.%, and the balance is Cu; the preparation method is: preparing a Cu-Ni-Sn-Cr alloy ingot in a medium-frequency induction furnace, and then homogenizing, rolling, solid solutionizing, and isothermal aging the ingot; compared with Cu-Be beryllium copper alloy, its advantages are that Cu-Ni-Sn- Finished Cr alloy strips have high tensile strength and elastic modulus, but their electrical conductivity can only reach 12-20% IASC. Patent CN116136003A discloses a method for preparing a high-conductivity, easy-cutting, and highly weather-resistant copper alloy. The Zr element is introduced into the copper alloy through the preparation of an intermediate alloy. After multiple furnace baking, the ingot is water-cooled and cast into an ingot. The ingot is then extruded, pickled, and hydraulically drawn to obtain the high-conductivity, easy-cutting, and highly weather-resistant copper alloy. The copper alloy obtained by this method can have a conductivity of over 90%, but its tensile strength can only reach approximately 375 MPa.

[0004] The copper alloy material obtained by the above process has extremely low conductivity when the strength of the copper alloy is increased through the operation described, while increasing the conductivity significantly reduces the strength, making it impossible to achieve both strength and conductivity. Therefore, it is necessary to provide a preparation method that can improve the strength and conductivity of C7035-based copper alloys to meet the future development requirements of high-strength and high-conductivity copper alloys and further expand the application of high-strength and high-conductivity copper alloys in various industries. Summary of the Invention

[0005] In view of the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a preparation process for a high-density twinned rare earth Cu-Ni-Si-Co copper alloy, which adopts the method of adding La, Ce and Y rare earth elements to Cu-Ni-Si-Co in small amounts and multiple times, cyclically performing a "slow heating-doping-rapid cooling" treatment process, and performing a cyclic cold deformation + heat treatment process to produce a high-density twinned microstructure, thereby achieving the processing goal of taking into account both the mechanical properties and the conductive properties of the copper alloy.

[0006] The technical solution of the present invention is as follows: a method for preparing a high-density twinned Cu-Ni-Si-Co copper alloy, the specific steps are as follows:

[0007] (1) The Cu-Ni-Si-Co alloy matrix is ​​subjected to homogenization heat treatment, including preheating, heat preservation, and rapid cooling processes.

[0008] (2) The Cu-Ni-Si-Co alloy matrix obtained in step (1) is subjected to a "slow heating-multiple doping-rapid cooling" treatment process, with a total number of cycles of not less than 5 times; the Cu alloy matrix is ​​slowly heated to 1300°C at a heating rate of 50°C / min, and then La, Ce and Y rare earth elements are added to the alloy in small amounts and multiple times, and after homogenization treatment, the matrix is ​​rapidly cooled to room temperature, wherein the cooling rate is not less than 20°C / s.

[0009] (3) Hot rolling is first performed, and then a cyclic cold rolling + heat treatment process is performed, wherein the cold rolling deformation is gradually reduced, and the number of cycles is not less than 3 times; in order to eliminate the residual stress of the alloy and improve the mechanical properties of the alloy.

[0010] Preferably, the composition and mass percentage of the Cu-Ni-Si-Co copper alloy of the present invention are: 1.0-3.5% Ni, 2.0-4.0% Si, 1.0-3.5% Co, 0.01-0.07% La, 0.01-0.07% Ce and 0.01-0.07% Y, with the remainder being copper and some inevitable impurity elements; an appropriate ratio of the Cu-Ni-Si-Co copper alloy components is selected to ensure that the alloy has good basic properties.

[0011] Preferably, the preheating temperature in step (1) of the present invention is 900°C, and the preheating rate is 50°C / min to achieve a uniform thermal equilibrium state; the holding temperature is 700-800°C to refine the alloy grains, and the holding time is 2-4h, wherein the cooling rate is 10°C / s to cool to room temperature to fix the microstructure of the alloy.

[0012] Preferably, the heating temperature in each step (2) of the present invention decreases smoothly with the increase in the number of cycles to ensure that the rare earth elements are better doped into the copper alloy.

[0013] Preferably, the specific process parameters of hot rolling in step (3) of the present invention are: the starting rolling temperature is 800-850° C., and the total cumulative deformation during rolling is 60%-70%.

[0014] Preferably, the hot rolling of the present invention is divided into three rolling passes, and the distribution ratios of the reduction amounts are 65%, 55% and 45% respectively.

[0015] Preferably, the cumulative deformation of cold rolling in step (3) of the present invention is 40% to 50%; in order to further improve the microstructure of the alloy and make it reach a more uniform state, wherein the specific process parameters of annealing are: annealing temperature is 400°C to 600°C, and annealing holding time is 1 to 2 hours.

[0016] Principle of the present invention:

[0017] Copper alloys can be strengthened through solid solution, second phase, deformation, and grain refinement. However, these strengthening methods all reduce their electrical conductivity, and conventional strengthening techniques often lead to a significant reduction in the electrical conductivity of metal materials. This is because these strengthening techniques essentially introduce various defects into the material, such as grain refinement, which introduces more grain boundaries, and processing strengthening, which introduces a large number of dislocations. These defects significantly increase electron scattering, thereby reducing electrical conductivity. All of these strengthening methods introduce various defects, which in turn increase the scattering of conduction electrons on these defects, increasing the metal's electrical resistance. The impact of twinning on the strength and electrical properties of copper is also discussed.

[0018] The addition of La, Ce and Y elements to the Cu-Ni-Si-Co copper alloy can effectively improve the performance of the alloy, enabling the alloy to maintain stable material performance in high-temperature environments, improve the corrosion resistance of the alloy, and make it have better durability in harsh environments and better heat dissipation performance under high-temperature conditions; the addition of La, Ce and Y elements can produce a synergistic effect and further improve the performance of the material.

[0019] The present invention introduces the excellent properties of rare earth elements into the copper alloy by adding La, Ce and Y rare earth elements in small amounts and multiple times after homogenization treatment. These rare earth elements can not only form a solid solution with the Cu-Ni-Si-Co matrix to enhance the strength and hardness of the alloy, but also form stable oxide and nitride phases to improve the oxidation resistance and wear resistance of the alloy. By cyclically adopting a "slow heating-multiple doping-rapid cooling" treatment process, the Cu-Ni-Si-Co copper alloy forms a high-density twin structure with a smaller grain size and a higher grain boundary density, thereby minimizing the reduction in electrical conductivity while improving the strength and hardness of the alloy. Finally, a cyclic cold rolling + heat treatment process can be used to further improve the structure and performance of the alloy. The cold rolling deformation refines the grains and increases the strength and hardness of the alloy. The heat treatment eliminates the residual stress of the alloy and improves the mechanical properties and stability of the alloy.

[0020] Beneficial effects of the present invention:

[0021] The present invention adds rare earth elements Co, La, Ce and Y to a general C7035 copper alloy, and cyclically performs a "slow heating-multiple doping-rapid cooling" heat treatment process, wherein the heating and holding temperatures of each time decrease smoothly with increasing number of cycles, and finally performs hot rolling and then cold rolling and annealing steps to ultimately obtain a rare earth Cu-Ni-Si-Co copper alloy with a high-density Luan microstructure; by obtaining high-density twins, both high strength and high conductivity are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of part of the production process of the high-density twinned rare earth Cu-Ni-Si-Co copper alloy plate of the present invention. DETAILED DESCRIPTION

[0023] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below with reference to specific embodiments; however, the protection scope of the present invention is not limited to the contents described.

[0024] Example 1

[0025] The chemical composition of the high-density twinned rare earth Cu-Ni-Si-Co copper alloy described in this embodiment is shown in Table 1.

[0026] Table 1 Chemical composition (wt%) of rare earth Cu-Ni-Si-Co copper alloy according to a specific embodiment of the present invention

[0027] Ni Si Co La Ce Y margin 3.5 2.0 3.5 0.07 0.07 0.07 Cu and inevitable impurities

[0028] The preparation method of the Cu-Ni-Si-Co copper alloy described in this embodiment specifically includes the following steps:

[0029] (1) A raw material of a copper alloy having the composition shown in Table 1 was prepared, and Cu, Ni, Si and Co were smelted according to the contents shown in Table 1 to obtain a Cu alloy matrix.

[0030] (2) The Cu alloy substrate was subjected to homogenization heat treatment: preheating temperature was 900 °C, preheating rate was 50 °C / min, holding temperature was 700 °C, holding time was 3 h, and cooling rate was 10 °C / s to room temperature.

[0031] (3) The Cu alloy matrix is ​​then slowly heated to 1300°C at a heating rate of 50°C / min, and rare earth elements La, Ce, and Y are added in small amounts and multiple times. After homogenization, the matrix is ​​rapidly cooled to room temperature at a cooling rate of 20°C / s. The above-mentioned "slow heating-multiple doping-rapid cooling" treatment process is cycled 5 times, and the heating temperature of each time decreases smoothly with the increase in the number of cycles. The heating temperatures of the 5 cycles are 1300°C, 1250°C, 1200°C, 1150°C and 1100°C, respectively, to obtain a rare earth Cu-Ni-Si-Co copper alloy.

[0032] (4) The rare earth Cu-Ni-Si-Co copper alloy is then rolled at an initial rolling temperature of 830°C until the cumulative total deformation reaches 60%. The rare earth Cu-Ni-Si-Co copper alloy after hot rolling is cold rolled until the cumulative deformation reaches 40%, and then annealed at a temperature of 400°C and an annealing holding time of 1 h. The above "cold rolling-annealing" process is cycled three times, wherein the cold rolling deformation gradually decreases, and the cold rolling deformations of the three cycles are 20%, 12%, and 8%, respectively.

[0033] The yield strength and conductivity of the high-density twinned rare earth Cu-Ni-Si-Co copper alloy are shown in Table 2:

[0034] Table 2 Performance test results of rare earth Cu-Ni-Si-Co copper alloy according to specific embodiments of the present invention

[0035] Yield strength / MPa Electrical conductivity / IACS 1014.3 42.3

[0036] Example 2

[0037] The chemical composition of the high-density twinned rare earth Cu-Ni-Si-Co copper alloy described in this embodiment is shown in Table 3.

[0038] Table 3 Chemical composition (wt%) of rare earth Cu-Ni-Si-Co copper alloy according to a specific embodiment of the present invention

[0039] Ni Si Co La Ce Y margin 2.0 3.0 2.5 0.04 0.04 0.04 Cu and inevitable impurities

[0040] The preparation method of the Cu-Ni-Si-Co copper alloy described in this embodiment specifically includes the following steps:

[0041] (1) A raw material of a copper alloy having the composition shown in Table 3 was prepared, and Cu, Ni, Si and Co were smelted according to the contents shown in Table 3 to obtain a Cu alloy matrix.

[0042] (2) The Cu alloy substrate was subjected to homogenization heat treatment: preheating temperature was 900 °C, preheating rate was 50 °C / min, holding temperature was 750 °C, holding time was 4 h, and cooling rate was 10 °C / s to room temperature.

[0043] (3) The Cu alloy matrix is ​​then slowly heated to 1300°C at a heating rate of 50°C / min, and rare earth elements La, Ce, and Y are added in small amounts and multiple times. After homogenization, the matrix is ​​rapidly cooled to room temperature at a cooling rate of 20°C / s. The above "slow heating-multiple doping-rapid cooling" treatment process is cycled 5 times, and the heating temperature of each cycle decreases smoothly with the increase in the number of cycles. The heating temperatures of the 5 cycles are 1300°C, 1250°C, 1200°C, 1150°C, and 1100°C, respectively, to obtain a rare earth Cu-Ni-Si-Co copper alloy.

[0044] (4) The rare earth Cu-Ni-Si-Co copper alloy is then rolled at an initial rolling temperature of 850°C until the cumulative total deformation reaches 60%. The rare earth Cu-Ni-Si-Co copper alloy that has completed hot rolling is then cold rolled until the cumulative deformation reaches 40%, and then annealed at a temperature of 600°C for 1 hour. The above "cold rolling-annealing" process is repeated three times, wherein the cold rolling deformation gradually decreases. The cold rolling deformations of the three cycles are 20%, 12%, and 8%, respectively.

[0045] The yield strength and conductivity of the high-density twinned rare earth Cu-Ni-Si-Co copper alloy are shown in Table 4:

[0046] Table 4 Performance test results of rare earth Cu-Ni-Si-Co copper alloy according to specific embodiments of the present invention

[0047] Yield strength / MPa Electrical conductivity / IACS 945.4 56.4

[0048] Example 3

[0049] The chemical composition of the high-density twinned rare earth Cu-Ni-Si-Co copper alloy described in this embodiment is shown in Table 5.

[0050] Table 5 Chemical composition (wt%) of rare earth Cu-Ni-Si-Co copper alloy according to a specific embodiment of the present invention

[0051] Ni Si Co La Ce Y margin 1.0 4 1.0 0.02 0.02 0.02 Cu and inevitable impurities

[0052] The preparation method of the Cu-Ni-Si-Co copper alloy described in this embodiment specifically includes the following steps:

[0053] (1) Prepare a raw material of a copper alloy with the composition shown in Table 5, and melt Cu, Ni, Si and Co according to the contents shown in Table 5 to obtain a Cu alloy matrix; perform a homogenization heat treatment on the Cu alloy matrix: preheating temperature is 900°C, preheating rate is 50°C / min, holding temperature is 800°C, holding time is 2h, and cooling rate is 10°C / s to room temperature.

[0054] (2) The Cu alloy matrix is ​​then slowly heated to 1300°C at a heating rate of 50°C / min, and rare earth elements La, Ce, and Y are added in small amounts and multiple times. After homogenization, the matrix is ​​rapidly cooled to room temperature at a cooling rate of 20°C / s. The above-mentioned "slow heating-multiple doping-rapid cooling" treatment process is cycled 5 times, and the heating temperature of each time decreases smoothly with the increase in the number of cycles. The heating temperatures of the 5 cycles are 1300°C, 1250°C, 1200°C, 1150°C and 1100°C, respectively, to obtain a rare earth Cu-Ni-Si-Co copper alloy.

[0055] (3) The rare earth Cu-Ni-Si-Co copper alloy is then rolled at an initial rolling temperature of 800°C until the cumulative total deformation reaches 60%; the rare earth Cu-Ni-Si-Co copper alloy after hot rolling is cold rolled until the cumulative deformation reaches 40%, and then annealed at a temperature of 500°C and an annealing holding time of 2 h; the above "cold rolling-annealing" process is cycled three times, wherein the cold rolling deformation gradually decreases, and the deformations of the three cold rolling cycles are 20%, 12% and 8%, respectively.

[0056] The yield strength and conductivity of the high-density twinned rare earth Cu-Ni-Si-Co copper alloy are shown in Table 6:

[0057] Table 6 Performance test results of rare earth Cu-Ni-Si-Co copper alloy according to specific embodiments of the present invention

[0058] Yield strength / MPa Electrical conductivity / IACS 869.4 70.5

[0059] Comparative Example 1

[0060] The chemical composition of the high-density twinned rare earth Cu-Ni-Si copper alloy described in this embodiment is shown in Table 7.

[0061] Table 7 Chemical composition (wt%) of Cu-Ni-Si copper alloy of the comparative example of the present invention

[0062] Ni Si margin 2.0 3.0 Cu and inevitable impurities

[0063] The preparation method of the Cu-Ni-Si copper alloy described in this embodiment specifically includes the following steps:

[0064] (1) Prepare a raw material of a copper alloy having the composition shown in Table 7, and melt Cu, Ni, and Si according to the contents shown in Table 7 to obtain a Cu alloy matrix; perform a homogenization heat treatment on the Cu alloy matrix: preheating temperature is 900°C, preheating rate is 50°C / min, holding temperature is 700°C, and cooling rate is 10°C / s to room temperature.

[0065] (2) The Cu-Ni-Si alloy is then rolled at an initial rolling temperature of 800°C until the cumulative total deformation reaches 60%.

[0066] (3) The Cu-Ni-Si copper alloy after hot rolling is cold rolled until the cumulative deformation reaches 40%, and then annealing is performed. The annealing temperature is 400°C and the annealing holding time is 1 hour.

[0067] The yield strength and conductivity of the Cu-Ni-Si copper alloy are shown in Table 8:

[0068] Table 8 Performance test results of rare earth Cu-Ni-Si copper alloy of comparative example of the present invention

[0069] Yield strength / MPa Electrical conductivity / IACS 811.4 39.5

[0070] By comparison, it can be seen that the yield strength and electrical conductivity of copper alloy plates are significantly improved after homogenization treatment, multiple "slow heating-multiple doping-rapid cooling" treatment processes, hot rolling, and cyclic "cold deformation + heat treatment process".

[0071] The addition of rare earth elements can improve the strength and hardness of the alloy, increase the tensile strength and yield strength of the alloy; rare earth elements form a solid solution with the base metal, strengthen the lattice structure of the alloy, and improve the heat resistance and wear resistance of the alloy; the addition of rare earth elements can improve the thermal stability of the alloy, reduce the grain growth and grain boundary migration of the alloy, prevent the loosening of the grain boundaries and grain degradation of the alloy, thereby achieving the stability of high-density twins; in addition, the addition of rare earth elements can change the phase composition of the alloy, promote the formation of precipitation phases and phase transformation behavior of the alloy; the addition of rare earth elements can adjust the grain size and grain boundary characteristics of the alloy, optimize the microstructure of the alloy, and improve the comprehensive performance of the alloy.

[0072] Comparative Example 2

[0073] The method and parameters of this embodiment are the same as those of Example 1, except that in step (3), the Cu alloy substrate is slowly heated to 1300°C at a heating rate of 50°C / min, La, Ce, and Y are added at one time, and after homogenization treatment, it is rapidly cooled to room temperature at a cooling rate of 20°C / s.

[0074] The yield strength and conductivity of the rare earth Cu-Ni-Si-Co copper alloy are shown in Table 9:

[0075] Table 9 Performance test results of rare earth Cu-Ni-Si-Co copper alloy

[0076] Yield strength / MPa Electrical conductivity / IACS 847.8 45.0

[0077] By comparing the test results of the performance of the material in Example 1 and the material in Comparative Example 1, it can be found that slow heating, adding rare earth elements, homogenization treatment and rapid cooling processes all improve the yield strength and conductivity of the material to a certain extent; this is because the rare earth elements are added after slow heating and homogenization treatment is performed, so that the rare earth elements are dissolved into the alloy material; and the doping of rare earth elements triggers the precipitation phase and phase change behavior in the alloy material, thereby improving the strength of the material; in addition, the addition of rare earth elements and rapid cooling also cause the alloy material to form more twin boundaries, making the grain size smaller and more numerous, thereby enhancing the conductive properties of the material.

[0078] In summary, the process method of the present invention is easy to operate, can effectively improve the twin characteristics in the copper alloy matrix, obtain rare earth copper alloy plates with high-density twins, and effectively improve the electrical conductivity of the aluminum alloy while ensuring that the strength of the copper alloy meets the alloy performance requirements. It is suitable for industrial applications and provides a practical technical solution for the preparation of high-strength and high-conductivity copper alloy materials for aerospace, microelectronics, rail transportation, communications and other industries.

[0079] Finally, it should be noted that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

Claims

1. A method for simultaneously improving the mechanical properties and electrical conductivity of a Cu-Ni-Si-Co copper alloy, characterized in that: La, Ce, and Y elements are added to Cu-Ni-Si-Co, and a "slow heating-multiple doping-rapid cooling" treatment process is used in a coordinated cycle. The specific steps are as follows: (1) Homogenization heat treatment of the Cu-Ni-Si-Co alloy matrix: including preheating, holding, and rapid cooling processes; (2) The Cu-Ni-Si-Co alloy matrix obtained in step (1) is subjected to a "slow heating-multiple doping-rapid cooling" treatment process for a total of not less than 5 cycles: the Cu-Ni-Si-Co alloy matrix is ​​slowly heated to 1300°C at a heating rate of 50°C / min, and then La, Ce and Y rare earth elements are added to the alloy in small amounts and multiple times, and then rapidly cooled to room temperature after homogenization treatment, wherein the cooling rate is not less than 20°C / s; (3) First hot rolling, then cyclic cold rolling + heat treatment process, wherein the cold rolling deformation gradually decreases, and the number of cycles is not less than 3; The heating temperature in each step (2) decreases as the number of cycles increases to ensure that the rare earth elements are better doped into the copper alloy.

2. The method for simultaneously improving the mechanical properties and electrical conductivity of a Cu-Ni-Si-Co copper alloy according to claim 1, characterized in that: The Cu-Ni-Si-Co copper alloy composition and its mass percentage are: 1.0-3.5% Ni, 2.0-4.0% Si, 1.0-3.5% Co, 0.01-0.07% La, 0.01-0.07% Ce and 0.01-0.07% Y, with the balance being copper and some inevitable impurity elements.

3. The method for simultaneously improving the mechanical properties and electrical conductivity of a Cu-Ni-Si-Co copper alloy according to claim 1, characterized in that: In step (1), the preheating temperature is 900°C, the preheating rate is 50°C / min, the holding temperature is 700~800°C, the holding time is 2~4h, and the cooling rate is 10°C / s to cool to room temperature.

4. The method for simultaneously improving the mechanical properties and electrical conductivity of a Cu-Ni-Si-Co copper alloy according to claim 1, characterized in that: The specific process parameters of hot rolling in step (3) are as follows: the starting rolling temperature is 800~850℃, and the total cumulative deformation during rolling is 60%~70%.

5. The method for simultaneously improving the mechanical properties and electrical conductivity of a Cu-Ni-Si-Co copper alloy according to claim 1, characterized in that: The cumulative deformation of cold rolling in step (3) is 40% to 50%. The specific process parameters of the heat treatment are: temperature of 400°C to 600°C, and holding time of 1 to 2 hours.

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