A high-strength and high-ductility Cu-Ni-Si alloy plate and a preparation method thereof

Abstract

The application provides a high-strength and high-ductility Cu-Ni-Si alloy plate and a preparation method thereof, and belongs to the technical field of copper alloys. The preparation method comprises the following steps: first cryogenic rolling, intermediate aging treatment and second cryogenic rolling are performed on a hot-rolled Cu-Ni-Si alloy to obtain a cryogenic-rolled plate; the total deformation after the first cryogenic rolling is 40-45% of the initial thickness of the hot-rolled Cu-Ni-Si alloy; the total deformation after the second cryogenic rolling is 70-80% of the initial thickness of the hot-rolled Cu-Ni-Si alloy; and the cryogenic-rolled plate is subjected to staged aging treatment to obtain the high-strength and high-ductility Cu-Ni-Si alloy plate. The preparation method of the Cu-Ni-Si alloy plate provided by the application can improve the plasticity of the Cu-Ni-Si alloy plate on the basis of maintaining high strength and excellent conductivity by adopting rolling with a medium deformation (70-80%).

Description

Technical Field

[0001] This invention relates to the field of copper alloy technology, and in particular to a high-strength, high-ductility Cu-Ni-Si alloy sheet and its preparation method. Background Technology

[0002] With the rapid development of integrated circuit technology, especially its penetration into large-scale and very large-scale integrated circuits, the performance requirements for leadframes are becoming increasingly stringent. Cu-Ni-Si alloys, due to their excellent comprehensive properties such as high strength and good conductivity, have become the preferred material for leadframe manufacturing in the integrated circuit field.

[0003] In traditional processing techniques, Cu-Ni-Si alloys exhibit unsatisfactory control over grain size, morphology, and precipitation behavior during conventional room temperature rolling followed by routine aging. This affects the alloy's strength and conductivity, limiting its potential in high-end applications. To address this issue, cryogenic rolling has been developed for alloy processing in recent years. However, current methods typically employ large deformation rolling (exceeding 90% deformation), resulting in significant work hardening, severely reducing the sheet's plasticity. Furthermore, this method involves a long processing flow, accompanied by high energy consumption and production costs. Summary of the Invention

[0004] To address one or more technical problems existing in the prior art, the present invention provides a high-strength and high-ductility Cu-Ni-Si alloy sheet and its preparation method. The preparation method of the Cu-Ni-Si alloy sheet provided by the present invention can improve the plasticity of the Cu-Ni-Si alloy sheet while maintaining high strength and excellent electrical conductivity by rolling with a moderate deformation amount (70-80%), thus obtaining a Cu-Ni-Si alloy sheet with excellent comprehensive performance.

[0005] The present invention provides a method for preparing a high-strength, high-ductility Cu-Ni-Si alloy plate in a first aspect, the method comprising:

[0006] A hot-rolled Cu-Ni-Si alloy is subjected to a first deep cryogenic rolling, an intermediate aging treatment, and a second deep cryogenic rolling to obtain a cryogenically rolled sheet. The total deformation after the first deep cryogenic rolling is 40-45% of the initial thickness of the hot-rolled Cu-Ni-Si alloy, and the total deformation after the second deep cryogenic rolling is 70-80% of the initial thickness of the hot-rolled Cu-Ni-Si alloy.

[0007] The cryogenically rolled sheet is subjected to graded aging treatment to obtain a high-strength, high-ductility Cu-Ni-Si alloy sheet.

[0008] Preferably, the hot-rolled Cu-Ni-Si alloy is obtained by solution treatment and hot rolling of a cast Cu-Ni-Si alloy;

[0009] Preferably, the solution treatment temperature is the same as the hot rolling temperature;

[0010] More preferably, the solution treatment and the hot rolling temperature are 850–950°C; and / or the solution treatment time is 1–2 hours.

[0011] Preferably, the total deformation after hot rolling is 70-80% of the initial thickness of the as-cast Cu-Ni-Si alloy;

[0012] The deformation amount in each pass during the hot rolling process is 15-25% of the initial thickness of the as-cast Cu-Ni-Si alloy; and / or

[0013] The holding time between each pass during the hot rolling process is 5 to 10 minutes.

[0014] Preferably, the deformation amount in each pass of the first cryogenic rolling process is 5 to 10% of the initial thickness of the hot-rolled Cu-Ni-Si alloy.

[0015] Preferably, the intermediate aging treatment temperature is 400–500°C, more preferably 425–475°C; and / or

[0016] The intermediate aging process takes 60–120 minutes.

[0017] Preferably, the second cryogenic rolling process includes a first stage and a second stage, wherein the deformation amount per pass in the second stage is less than the deformation amount per pass in the first stage.

[0018] Preferably, the deformation amount per pass in the first stage is 8-10% of the initial thickness of the hot-rolled Cu-Ni-Si alloy; and / or

[0019] The deformation amount per pass in the second stage is 3 to 5% of the initial thickness of the hot-rolled Cu-Ni-Si alloy.

[0020] Preferably, the graded aging treatment includes a primary aging treatment and a secondary aging treatment, wherein the temperature of the secondary aging treatment is higher than the temperature of the primary aging treatment.

[0021] Preferably, the temperature of the first-stage aging treatment is 150–250°C; and / or

[0022] The temperature of the secondary aging treatment is not higher than the temperature of the intermediate aging treatment.

[0023] In a second aspect, the present invention provides a high-strength, high-ductility Cu-Ni-Si alloy sheet, which is prepared using the preparation method described in the first aspect.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects:

[0025] This invention first involves a small-deformation deep cryogenic rolling process to introduce deformation twins, thereby achieving an initial increase in material strength. Simultaneously, it effectively reduces dislocation proliferation during rolling, decreases internal stress concentration, helps maintain the material's plasticity, enhances its formability at low temperatures, and reduces the likelihood of fracture. Next, an intermediate aging treatment is performed. While maintaining the deformation twins, this process promotes the formation of fine and uniformly distributed precipitates in the alloy matrix, effectively hindering dislocation movement and further increasing material strength. It also mitigates the softening effect caused by precipitation. Finally, a second deep cryogenic rolling process is performed, utilizing the effects of the intermediate aging treatment to promote the formation of more dense deformation twins, further enhancing the material's strength. This two-step deep cryogenic rolling process achieves the desired result. This invention achieves grain refinement of the Cu-Ni-Si alloy sheet under moderate deformation (70-80%), thereby enhancing its plasticity. It also promotes the uniform distribution of nano-precipitates in the alloy, significantly improving the strength of the Cu-Ni-Si alloy sheet while maintaining its electrical conductivity. Finally, through graded aging treatment, the precipitation process in the alloy is precisely controlled while maintaining deformation twinning, resulting in a more uniform precipitate distribution. This effectively reduces the negative impact of dislocations on plasticity, while also reducing precipitate aggregation and grain coarsening, maintaining the uniformity and stability of the material's microstructure, and improving the uniformity of the material during plastic deformation, thus increasing elongation and further enhancing the comprehensive mechanical properties of the Cu-Ni-Si alloy sheet. The Cu-Ni-Si alloy sheet preparation method provided by this invention achieves improved plasticity of the Cu-Ni-Si alloy sheet while maintaining high strength and excellent electrical conductivity through rolling with moderate deformation (70-80%), resulting in Cu-Ni-Si alloy sheets with excellent comprehensive properties.

[0026] The method for preparing Cu-Ni-Si alloy plates provided by the present invention can improve the plasticity of Cu-Ni-Si alloy plates while maintaining high strength and excellent electrical conductivity by rolling with a medium deformation amount (70-80%), thus obtaining Cu-Ni-Si alloy plates with excellent comprehensive properties. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram illustrating the preparation process of the high-strength, high-ductility Cu-Ni-Si alloy sheet of the present invention;

[0029] Figure 2 This is a diagram illustrating the mechanism by which the preparation method of the high-strength and high-ductility Cu-Ni-Si alloy sheet provided by this invention improves the mechanical properties of the Cu-Ni-Si alloy sheet.

[0030] Figure 3 This is a metallographic diagram of the hot-rolled Cu-Ni-Si alloy provided in Example 1 of the present invention;

[0031] Figure 4 These are the grain boundary distribution diagram (left) and KAM diagram (right) of the first cryogenically rolled plate provided in Embodiment 1 of the present invention;

[0032] Figure 5 These are the grain boundary distribution map (left) and SEM image (right) of the plate after intermediate aging treatment provided in Embodiment 1 of the present invention;

[0033] Figure 6 This is a TEM-EDS image of the high-strength, high-ductility Cu-Ni-Si alloy sheet provided in Embodiment 1 of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0035] The present invention provides a method for preparing a high-strength, high-ductility Cu-Ni-Si alloy plate in a first aspect, the method comprising:

[0036] A hot-rolled Cu-Ni-Si alloy is subjected to a first cryogenic rolling, an intermediate aging treatment, and a second cryogenic rolling to obtain a cryogenically rolled sheet. The total deformation after the first cryogenic rolling is 40-45% of the initial thickness of the hot-rolled Cu-Ni-Si alloy (e.g., 40%, 41%, 42%, 43%, 44%, or 45%). The total deformation after the second cryogenic rolling is 70-80% of the initial thickness of the hot-rolled Cu-Ni-Si alloy (e.g., 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, or 80%).

[0037] The cryogenically rolled sheet is subjected to graded aging treatment to obtain a high-strength, high-ductility Cu-Ni-Si alloy sheet.

[0038] This invention first involves a small-deformation deep cryogenic rolling process to introduce deformation twins, thereby achieving an initial increase in material strength. Simultaneously, it effectively reduces dislocation proliferation during rolling, decreases internal stress concentration, helps maintain the material's plasticity, enhances its formability at low temperatures, and reduces the likelihood of fracture. Next, an intermediate aging treatment is performed. While maintaining the deformation twins, this process promotes the formation of fine and uniformly distributed precipitates in the alloy matrix, effectively hindering dislocation movement and further increasing material strength. It also mitigates the softening effect caused by precipitation. Finally, a second deep cryogenic rolling process is performed, utilizing the effects of the intermediate aging treatment to promote the formation of more dense deformation twins, further enhancing the material's strength. This two-step deep cryogenic rolling process achieves the desired result. This process achieves grain refinement of the alloy under moderate deformation (70-80%), thereby enhancing the plasticity of Cu-Ni-Si alloy sheets. It also promotes the uniform distribution of nano-precipitates in the alloy, significantly improving the strength of Cu-Ni-Si alloy sheets while maintaining their electrical conductivity. Finally, through graded aging treatment, the precipitation process in the alloy is precisely controlled while maintaining deformation twins, resulting in a more uniform distribution of precipitates. This effectively reduces the negative impact of dislocations on plasticity, while also reducing precipitate aggregation and grain coarsening, maintaining the uniformity and stability of the material's microstructure, and improving the uniformity of the material during plastic deformation, thus increasing elongation and further enhancing the comprehensive mechanical properties of Cu-Ni-Si alloy sheets.

[0039] The method for preparing Cu-Ni-Si alloy plates provided by the present invention can improve the plasticity of Cu-Ni-Si alloy plates while maintaining high strength and excellent electrical conductivity by rolling with a medium deformation amount (70-80%), thus obtaining Cu-Ni-Si alloy plates with excellent comprehensive properties.

[0040] The inventors discovered that, when the total deformation is constant, if the deformation in the first cryogenic rolling process is too large, the deformation in the subsequent second cryogenic rolling process will be smaller, resulting in fewer deformation twins generated during rolling and ultimately reducing the strength of the sheet. Furthermore, insufficient deformation in the second cryogenic rolling process reduces the number of precipitates during the graded aging process, leading to a decrease in both the sheet's strength and electrical conductivity. If the total deformation after the second cryogenic rolling process is too small, the material has low internal energy storage, resulting in a reduced number of precipitates after subsequent graded aging treatment, leading to lower strength and electrical conductivity, failing to meet practical application requirements. Conversely, if the total deformation after the second cryogenic rolling process is too large, self-annealing is prone to occur during the second cryogenic rolling process, causing the material to recrystallize and reducing strength. Even without self-annealing, cryogenic rolling significantly increases the dislocation density of the material, leading to a decrease in the plasticity of the final sheet.

[0041] According to some preferred embodiments, the hot-rolled Cu-Ni-Si alloy is obtained by solution treatment and hot rolling of a cast Cu-Ni-Si alloy;

[0042] Preferably, the solution treatment temperature is the same as the hot rolling temperature;

[0043] More preferably, the solution treatment and the hot rolling temperature is 850–950°C (e.g., 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C, or 950°C); and / or, the solution treatment time is 1–2 hours (e.g., 1 hour, 1.2 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.8 hours, or 2 hours).

[0044] To promote the recrystallization process of the material and eliminate lattice distortion caused by deformation, the present invention selects the same temperature for solution treatment and hot rolling, and controls the temperatures of solution treatment and hot rolling within the aforementioned range. Hot rolling improves the coarse grains of the initial cast Cu-Ni-Si alloy, promotes the uniform distribution of alloying elements, and reduces compositional segregation. The Cu-Ni-Si alloy used in this invention is selected from, but is not limited to, C70250 copper alloy, MAX251 copper alloy, KLFA85 copper alloy (Cu-3.2Ni-0.7Si-1.1Zn), CuNi2Si alloy, and CuNiSi-(Cr,Zr) alloy. According to some preferred embodiments, the total deformation after hot rolling is 70-80% of the initial thickness of the cast Cu-Ni-Si alloy (e.g., 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, or 80%).

[0045] According to some preferred embodiments, the deformation amount per pass during the hot rolling process is 15% to 25% of the initial thickness of the as-cast Cu-Ni-Si alloy (for example, it can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24% or 25%).

[0046] According to some preferred embodiments, the holding time between each pass in the hot rolling process is 5 to 10 minutes (for example, it can be 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes or 10 minutes).

[0047] In order to ensure uniform temperature inside the material and consistent temperature distribution during rolling, and to avoid uneven deformation caused by temperature differences, the material needs to be kept warm for 5 to 10 minutes between each pass. After the last pass of rolling, the material is cooled with water and no further heat preservation is required.

[0048] According to some preferred embodiments, the deformation amount per pass in the first cryogenic rolling process is 5 to 10% of the initial thickness of the hot-rolled Cu-Ni-Si alloy (for example, it can be 5%, 6%, 7%, 8%, 9% or 10%).

[0049] According to some preferred embodiments, the intermediate aging treatment temperature is 400–500°C (e.g., 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, or 500°C), preferably 425–475°C (e.g., 425°C, 430°C, 435°C, 440°C, 445°C, 450°C, 455°C, 460°C, 465°C, 470°C, or 475°C). Performing intermediate aging treatment within the above temperature range facilitates the formation of fine and uniformly distributed precipitates in the alloy matrix. These fine, dispersed precipitates effectively hinder dislocation movement, thereby improving the material's strength. Simultaneously, performing aging treatment within the aforementioned lower temperature range can mitigate the effects of recovery softening caused by precipitation in the alloy.

[0050] According to some preferred embodiments, the intermediate aging process takes 60 to 120 minutes (for example, it can be 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes or 120 minutes).

[0051] According to some preferred embodiments, the second cryogenic rolling includes a first stage and a second stage, wherein the deformation per pass in the second stage is less than the deformation per pass in the first stage. The later stage (second stage) of the second cryogenic rolling process of this invention employs a smaller reduction in rolling weight, which can reduce the risk of surface cracking and avoid material hardening or cracking due to excessive deformation, resulting in a smoother and more even surface. Furthermore, the smaller deformation in the later stage (second stage) allows for precise control of the final material thickness, ensuring consistency and accuracy in product dimensions.

[0052] According to some preferred embodiments, the deformation amount per pass in the first stage is 8 to 10% of the initial thickness of the hot-rolled Cu-Ni-Si alloy (e.g., 8%, 9%, or 10%); and / or

[0053] The deformation amount per pass in the second stage is 3 to 5% of the initial thickness of the hot-rolled Cu-Ni-Si alloy (for example, it can be 3%, 4% or 5%).

[0054] According to some preferred embodiments, the graded aging process includes a first-level aging process and a second-level aging process, wherein the temperature of the second-level aging process is higher than the temperature of the first-level aging process.

[0055] This invention utilizes graded aging to enhance the overall properties of materials. In the low-temperature aging stage of graded aging, solute atoms aggregate in the crystal lattice, forming GP regions (atomic segregation regions). These GP regions maintain a coherent relationship with the matrix, leading to lattice distortion and laying the foundation for improved alloy strength. The formed GP regions act as precursors for precipitates, locally pinning dislocations and slowing their movement, thereby reducing the overall dislocation density and helping to maintain the material's plasticity. Subsequently, in the high-temperature aging stage, the GP regions gradually transform into more stable precipitates. These precipitates remain small and dispersed during high-temperature aging, preventing excessive growth. The small and uniformly distributed precipitates significantly hinder dislocation movement, thereby increasing the material's strength and effectively maintaining the balance between strength and plasticity. The high-temperature aging stage also helps relax internal stresses and reduce work hardening effects, which not only improves the material's plastic deformation capacity but also further reduces dislocation accumulation. Furthermore, the staged aging treatment, through phased temperature control, promotes the release of internal stress in the material, helps alleviate work hardening effects and internal residual stress, and thus significantly improves the material's plastic deformation capacity. The precipitates obtained through staged aging treatment are more uniformly distributed, reducing precipitate aggregation and grain coarsening, maintaining the uniformity and stability of the material's microstructure, and improving the uniformity of the material during plastic deformation, thereby increasing elongation.

[0056] Regarding electrical conductivity, the scattering effect of solid solution atoms on electrons is more significant than that of precipitated phases, while twin boundaries have low scattering characteristics. The deformation twins introduced by the second cryogenic rolling process have a negligible impact on electrical conductivity. Therefore, the overall conductivity of the material increases after the formation of precipitated phases. The precipitated phases after graded aging are even finer and pose less obstruction to electron transport paths, thus maintaining a high conductivity.

[0057] The inventors discovered that using conventional methods instead of staged aging treatment after the second cryogenic rolling process results in coarser precipitates that tend to aggregate, forming localized concentrated areas and leading to inhomogeneities in material properties. These coarse precipitates, acting as obstacles to dislocation movement, increase work hardening and thus reduce the material's plastic deformation capacity. Furthermore, larger precipitates increase electron scattering, making it difficult to maintain high electrical conductivity.

[0058] According to some preferred embodiments, the temperature of the primary aging treatment is 150–250°C (e.g., 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, or 250°C). If the temperature of the primary aging treatment is too low, the atomic segregation regions (GP regions) will form slowly or incompletely, which is detrimental to the gradual transformation of the GP regions into more stable precipitates during the secondary aging treatment. Furthermore, if the temperature of the primary aging treatment is too low, residual stress cannot be released, resulting in a decrease in the elongation of the rolled sheet; if the temperature of the primary aging treatment is too high, the atomic segregation regions will form too quickly and become too large, directly precipitating coarse, stable precipitates, thus reducing the strength of the rolled sheet.

[0059] According to some preferred embodiments, after the first-stage aging treatment, the temperature is increased to the temperature of the second-stage aging treatment at a heating rate of 30–40 °C / min (e.g., 30 °C / min, 32 °C / min, 34 °C / min, 35 °C / min, 36 °C / min, 38 °C / min, or 40 °C / min). To ensure a uniform temperature distribution within the material and avoid twin boundary migration due to localized overheating, the heating rate should not be too fast; therefore, the present invention preferably uses the heating rate within the above-mentioned range.

[0060] According to some preferred embodiments, the temperature of the secondary aging treatment is not higher than the temperature of the intermediate aging treatment.

[0061] If the temperature of the secondary aging treatment in this invention is too high, it will cause the matrix grains to grow and the size of the precipitated phases to increase, resulting in a decrease in the strength of the rolled sheet. At the same time, it will also cause the precipitated phases to precipitate at the grain boundaries of the matrix grains, resulting in a decrease in the elongation of the rolled sheet.

[0062] The mechanical property improvement mechanism of Cu-Ni-Si alloy using the "first deep cold rolling - intermediate aging treatment - second deep cold rolling - staged aging treatment" process is as follows: Figure 2 During the intermediate aging stage, a large number of fine and dispersed precipitates have formed inside the alloy. These precipitates effectively hinder dislocation movement during the second cryogenic rolling process, enhancing the driving force for twin nucleation and thus significantly increasing the content of deformed twins. The refinement of the deformed twin bundles caused by the second cryogenic rolling further strengthens the hindering effect on dislocations, increasing the dislocation density and promoting the subsequent precipitation process. Therefore, by employing the "first cryogenic rolling - intermediate aging treatment - second cryogenic rolling - staged aging treatment" method of this invention, it is possible to achieve or even surpass the strength level obtained by the traditional process with 90% deformation at a relatively low deformation amount (70-80%).

[0063] In a second aspect, the present invention provides a high-strength, high-ductility Cu-Ni-Si alloy sheet, which is prepared using the preparation method described in the first aspect.

[0064] To more clearly illustrate the technical solution and advantages of the present invention, the present invention will be further described below with reference to embodiments. The present invention does not specifically limit the source of the reagents used in the embodiments and comparative examples; they can be directly purchased or synthesized in-house. The examples of C70250 copper alloy (chemical analysis shows that the copper alloy has a Ni content of 2.56 wt.%, a Si content of 0.54 wt.%, a Mg content of 0.16 wt.%, and the remainder is Cu), MAX251 copper alloy (chemical analysis shows that the copper alloy has a Ni content of 2 wt.%, a Si content of 0.5 wt.%, a Sn content of 0.5 wt.%, a Zn content of 1 wt.%, and the remainder is Cu), and KLFA85 copper alloy (chemical analysis shows that the copper alloy has a Ni content of 3.2 wt.%, a Si content of 0.7 wt.%, a Zn content of 1.1 wt.%, and the remainder is Cu) are used to illustrate the technical solution of the present invention and are not intended to limit it. The rolling of other Cu-Ni-Si alloys (e.g., CuNi2Si alloy, CuNiSi-(Cr,Zr) alloy, etc.) plates is also applicable to the preparation method of the present invention. It should be noted that the cryogenic rolling process of the present invention involves immersion in liquid nitrogen (-196°C) first, followed by rapid removal and rolling at room temperature. Heat loss is unavoidable during this process and cannot be precisely controlled. Therefore, the temperature of cryogenic rolling in the embodiments of the present invention is a range.

[0065] Example 1

[0066] A method for preparing a high-strength, high-ductility Cu-Ni-Si alloy sheet includes:

[0067] S1. The as-cast Cu-Ni-Si alloy (C70250 copper alloy) with an initial thickness of 30 mm is solution treated at 900℃ for 1 h, and then hot-rolled at 900℃ for 4 passes with a deformation of 20% of the initial thickness. Each pass is held for 5 min. After the last pass, the material is water-cooled without holding, and a hot-rolled Cu-Ni-Si alloy with a thickness of 6 mm is obtained. At this time, the total deformation of hot rolling is 80% of the initial thickness.

[0068] S2. The hot-rolled Cu-Ni-Si alloy with a thickness of 6 mm is immersed in liquid nitrogen (-196℃) for 30 min, and then subjected to deep cryogenic rolling at -196 to -150℃ for 4 times with a deformation amount of 10% of the initial thickness of the hot-rolled Cu-Ni-Si alloy. The alloy is immersed in liquid nitrogen for 10 min between each pass to obtain the first deep cryogenic rolled plate with a thickness of 3.6 mm. At this time, the total deformation amount is 40% of the initial thickness of the hot-rolled Cu-Ni-Si alloy.

[0069] S3. The first cryogenically rolled sheet with a thickness of 3.6 mm is aged at 450℃ for 90 min, and then the aged material is immersed in liquid nitrogen for 30 min. Then, the second cryogenically rolled sheet is subjected to a temperature range of -196 to -150℃. First, three passes of cryogenic rolling with a deformation amount of 10% of the initial thickness of the hot-rolled Cu-Ni-Si alloy are performed, followed by two passes of cryogenic rolling with a deformation amount of 5% of the initial thickness of the hot-rolled Cu-Ni-Si alloy. The sheet is immersed in liquid nitrogen for 10 min between each pass to obtain a second cryogenically rolled sheet with a thickness of 1.2 mm. At this time, the total deformation amount is 80% of the initial thickness of the hot-rolled Cu-Ni-Si alloy.

[0070] S4. After the second cryogenically rolled plate is water-cooled, it is first subjected to low-temperature aging treatment at 200℃ for 1 hour, and then subjected to high-temperature aging treatment at 450℃ for 30 minutes at a heating rate of 35℃ / min to obtain a high-strength and high-ductility Cu-Ni-Si alloy plate. Its performance data are shown in Table 1.

[0071] Metallographic image of the hot-rolled Cu-Ni-Si alloy in this embodiment ( Figure 3 As can be seen, the microstructure is mostly equiaxed, which helps improve the material's processing performance and ensures good plastic deformation capacity, making it less prone to fracture under external forces. Furthermore, annealing twins appeared during the annealing process, with a grain size of approximately 79.3 μm. Overall, the microstructure exhibits good homogeneity, ensuring consistent initial properties in different directions and laying the foundation for subsequent cryogenic rolling.

[0072] Microstructure diagram of the first cryogenically rolled sheet in this embodiment ( Figure 4As can be seen, the grains exhibit significant elongation along the rolling direction. During cryogenic rolling, the low-temperature environment suppresses dislocation slip and climb mechanisms, and the plastic deformation within the material is mainly achieved through the formation of deformation twins. Twin boundaries effectively hinder dislocation movement, thus achieving a significant increase in material strength with relatively low deformation. The formation of twin boundaries also provides favorable nucleation sites for the nucleation and growth of precipitates during post-aging treatment. In the intermediate aging treatment after cryogenic rolling, the high-density dislocations near these twin boundaries provide favorable nucleation sites for the nucleation and growth of precipitates, promoting the uniform distribution of precipitates and thus optimizing the overall mechanical properties of the material.

[0073] Grain boundary distribution diagram of the plate microstructure after intermediate aging treatment in this embodiment. Figure 5 (Left) As can be seen, the deformed twins still exist and exhibit thermal stability; no significant twin boundary migration or merging occurred at the aging temperature of 450℃. SEM image of the microstructure of the plate after intermediate aging treatment in this embodiment ( Figure 5 (Right) It can be seen that during the intermediate aging process, the alloy precipitated more fully after the first deep cryogenic rolling. In addition to accumulation along ordinary grain boundaries, fine precipitates were also observed in the vicinity of the deformed twin bundles. These precipitates not only hinder dislocation movement, further improving the material's strength, but also help to impede grain boundary migration, suppress grain coarsening, and maintain the material's microstructural stability. These precipitates, together with the twins, significantly enhance the material's strength by hindering dislocation movement. It should be noted that... Figure 4 and Figure 5 In the middle, RD is the rolling direction, ND is the normal direction, TD is the transverse direction, and Σ3grain boundary represents Σ3 type grain boundary (which can be used to represent twin boundaries in the material of this invention).

[0074] In this embodiment, the TEM-EDS of Cu-Ni-Si alloy sheet after "first deep cold rolling - intermediate aging treatment - second deep cold rolling - graded aging treatment" is... Figure 6 As can be seen from the diagram, the precipitates (indicated by arrows) exhibit fine size and multi-scale distribution. Precipitates of different sizes can achieve a balance between strength and plasticity; fine precipitates contribute to increased strength, while larger precipitates help maintain plasticity. The elemental distribution diagram shows a consistent enrichment of nickel and silicon (Si) in the magnified local area, suggesting that the precipitates are mainly composed of Ni and Si.

[0075] Example 2

[0076] A method for preparing a high-strength, high-ductility Cu-Ni-Si alloy sheet includes:

[0077] S1. The as-cast Cu-Ni-Si alloy (MAX251 copper alloy) with an initial thickness of 30 mm was solution treated at 900℃ for 1 h, and then hot-rolled at 900℃ for 4 passes with a deformation of 20% of the initial thickness. Each pass was held for 5 min. After the last pass, the material was water-cooled without holding, and a hot-rolled Cu-Ni-Si alloy with a thickness of 6 mm was obtained. At this time, the total deformation of hot rolling was 80% of the initial thickness.

[0078] S2. The hot-rolled Cu-Ni-Si alloy with a thickness of 6 mm is immersed in liquid nitrogen for 30 min, and then subjected to deep cryogenic rolling at -196 to -150℃ for 4 times with a deformation amount of 10% of the initial thickness of the hot-rolled Cu-Ni-Si alloy. The alloy is immersed in liquid nitrogen for 10 min between each pass to obtain the first deep cryogenic rolled plate with a thickness of 3.6 mm. At this time, the total deformation amount is 40% of the initial thickness of the hot-rolled Cu-Ni-Si alloy.

[0079] S3. The first cryogenically rolled sheet with a thickness of 3.6 mm is aged at 500℃ for 90 min, then the aged material is immersed in liquid nitrogen for 30 min, and then subjected to a second cryogenic rolling at -196 to -150℃. First, two passes of cryogenic rolling with a deformation amount of 10% of the initial thickness of the hot-rolled Cu-Ni-Si alloy are performed, followed by two passes of cryogenic rolling with a deformation amount of 5% of the initial thickness of the hot-rolled Cu-Ni-Si alloy. The sheet is immersed in liquid nitrogen for 10 min between each pass to obtain a second cryogenically rolled sheet with a thickness of 1.8 mm. At this time, the total deformation amount is 70% of the initial thickness of the hot-rolled Cu-Ni-Si alloy.

[0080] S4. After the second cryogenically rolled plate is water-cooled, it is first subjected to low-temperature aging treatment at 250℃ for 1 hour, and then the temperature is increased to 450℃ at a heating rate of 35℃ / min for high-temperature aging treatment for 30 minutes to obtain a high-strength and high-ductility Cu-Ni-Si alloy plate. Its performance data are shown in Table 1.

[0081] Example 3

[0082] A method for preparing a high-strength, high-ductility Cu-Ni-Si alloy sheet includes:

[0083] S1. The as-cast Cu-Ni-Si alloy (KLFA85 copper alloy) with an initial thickness of 30 mm was solution treated at 900℃ for 1 h, and then hot-rolled at 900℃ for 4 passes with a deformation of 20% of the initial thickness. Each pass was held for 5 min. After the last pass, the material was water-cooled without holding, resulting in a hot-rolled Cu-Ni-Si alloy with a thickness of 6 mm. At this point, the total deformation of the hot rolling was 80% of the initial thickness.

[0084] S2. The hot-rolled Cu-Ni-Si alloy with a thickness of 6 mm is immersed in liquid nitrogen for 30 min, and then subjected to deep cryogenic rolling at -196 to -150℃ for 4 times with a deformation amount of 10% of the initial thickness of the hot-rolled Cu-Ni-Si alloy. The alloy is immersed in liquid nitrogen for 10 min between each pass to obtain the first deep cryogenic rolled plate with a thickness of 3.6 mm. At this time, the total deformation amount is 40% of the initial thickness of the hot-rolled Cu-Ni-Si alloy.

[0085] S3. The first cryogenically rolled sheet with a thickness of 3.6 mm is aged at 400℃ for 90 min, then the aged material is immersed in liquid nitrogen for 30 min, and then subjected to a second cryogenic rolling at -196 to -150℃. First, three passes of cryogenic rolling with a deformation amount of 10% of the initial thickness of the hot-rolled Cu-Ni-Si alloy are performed, followed by one pass of cryogenic rolling with a deformation amount of 5% of the initial thickness of the hot-rolled Cu-Ni-Si alloy. The sheet is immersed in liquid nitrogen for 10 min between each pass to obtain a second cryogenically rolled sheet with a thickness of 1.5 mm. At this time, the total deformation amount is 75% of the initial thickness of the hot-rolled Cu-Ni-Si alloy.

[0086] S4. After the second cryogenically rolled plate is water-cooled, it is first subjected to low-temperature aging treatment at 150℃ for 1 hour, and then heated to 450℃ at a heating rate of 35℃ / min for high-temperature aging treatment for 30 minutes to obtain a high-strength and high-ductility Cu-Ni-Si alloy plate. Its performance data are shown in Table 1.

[0087] Comparative Example 1

[0088] The process is basically the same as in Example 1, except that: S4. After the second cryogenic rolled plate is water-cooled, it is subjected to high-temperature aging treatment at 450°C for 30 minutes to obtain Cu-Ni-Si alloy plate, the performance data of which are shown in Table 1.

[0089] Comparative Example 2

[0090] A method for preparing Cu-Ni-Si alloy plate, comprising:

[0091] S1. The as-cast Cu-Ni-Si alloy (C70250 copper alloy) with an initial thickness of 30 mm is solution treated at 900℃, and then hot-rolled at 900℃ for 4 passes with a deformation of 20% of the initial thickness. Each pass is held for 5 minutes. After the last pass, the material is water-cooled without holding, resulting in a hot-rolled Cu-Ni-Si alloy with a thickness of 6 mm. At this point, the total deformation is 80% of the initial thickness.

[0092] S2. A hot-rolled Cu-Ni-Si alloy with a thickness of 6 mm is subjected to room temperature rolling with a total deformation of 90% of the initial thickness of the hot-rolled Cu-Ni-Si alloy. The deformation of each pass is 10% of the deformation of the previous pass, to obtain a room temperature rolled plate.

[0093] S3. The room temperature rolled plate was aged at 450℃ for 90 min to obtain Cu-Ni-Si alloy plate, and its performance data are shown in Table 1.

[0094] Comparative Example 3

[0095] A method for preparing Cu-Ni-Si alloy plate, comprising:

[0096] S1. The as-cast Cu-Ni-Si alloy (C70250 copper alloy) with an initial thickness of 30 mm is solution treated at 900℃ for 1 h, and then hot-rolled at 900℃ for 4 passes with a deformation of 20% of the initial thickness. Each pass is held for 5 min. After the last pass, the material is water-cooled without holding, and a hot-rolled Cu-Ni-Si alloy with a thickness of 6 mm is obtained. At this time, the total deformation of hot rolling is 80% of the initial thickness.

[0097] S2. A 6mm thick hot-rolled Cu-Ni-Si alloy was subjected to 4 passes of room temperature rolling with a deformation amount of 10% of the initial thickness of the hot-rolled Cu-Ni-Si alloy, followed by aging treatment at 450℃ for 90 minutes. Then, it was subjected to 4 passes of room temperature rolling with a deformation amount of 10% of the initial thickness of the hot-rolled Cu-Ni-Si alloy, followed by aging treatment at 450℃ for 90 minutes to obtain a Cu-Ni-Si alloy sheet with a thickness of 1.2mm. At this time, the total deformation amount was 80% of the initial thickness of the hot-rolled Cu-Ni-Si alloy. Its performance data are shown in Table 1.

[0098] Comparative Example 4

[0099] The process is basically the same as in Example 1, except that: S3. The first cryogenically rolled sheet with a thickness of 3.6 mm is aged at 450°C for 90 min, and then the aged material is immersed in liquid nitrogen for 30 min. The second cryogenically rolled sheet is then subjected to a process at -196 to -150°C. The first process involves two passes of cryogenic rolling with a deformation amount of 10% of the initial thickness of the hot-rolled Cu-Ni-Si alloy, and the second process involves one pass of cryogenic rolling with a deformation amount of 5% of the initial thickness of the hot-rolled Cu-Ni-Si alloy. The sheet is immersed in liquid nitrogen for 10 min between each pass to obtain a second cryogenically rolled sheet with a thickness of 2.1 mm. At this time, the total deformation amount is 65% of the initial thickness of the hot-rolled Cu-Ni-Si alloy. The performance data are shown in Table 1.

[0100] Comparative Example 5

[0101] The process is basically the same as in Example 1, except that: S3. The first cryogenically rolled sheet with a thickness of 3.6 mm is aged at 450°C for 90 min, and then the aged material is immersed in liquid nitrogen for 30 min. The second cryogenically rolled sheet is then subjected to a process at -196 to -150°C. First, four passes of cryogenic rolling with a deformation amount of 10% of the initial thickness of the hot-rolled Cu-Ni-Si alloy are performed, followed by two passes of cryogenic rolling with a deformation amount of 5% of the initial thickness of the hot-rolled Cu-Ni-Si alloy. The sheet is immersed in liquid nitrogen for 10 min between each pass to obtain a second cryogenically rolled sheet with a thickness of 0.6 mm. At this time, the total deformation amount is 90% of the initial thickness of the hot-rolled Cu-Ni-Si alloy. Its performance data is shown in Table 1.

[0102] Comparative Example 6

[0103] The process is basically the same as in Example 1, except that: S4. After the second cryogenic rolled plate is water-cooled, it is first subjected to low-temperature aging treatment at 200°C for 1 hour, and then heated to 550°C at a heating rate of 35°C / min for high-temperature aging treatment for 30 minutes to obtain a high-strength and high-ductility Cu-Ni-Si alloy plate. Its performance data are shown in Table 1.

[0104] Table 1. Performance data of Cu-Ni-Si alloy plates prepared in the embodiments and comparative examples of the present invention.

[0105] Hardness / HV Tensile strength / MPa Elongation / % Conductivity / % IACS Example 1 265.3 892 11.7 37.3 Example 2 252.8 840 11.0 37.1 Example 3 261.2 877 11.6 36.9 Comparative Example 1 242.5 799 9.5 36.1 Comparative Example 2 230.1 728 10.1 26.6 Comparative Example 3 218.4 708 9.8 36.2 Comparative Example 4 231.3 736 9.2 34.3 Comparative Example 5 238.6 762 10.2 36.3 Comparative Example 6 234.1 745 11.5 37.4

[0106] The mechanical properties and electrical conductivity of Cu-Ni-Si alloy sheets obtained under different rolling-aging processes are shown in Table 1. Compared with the alloy sheet with 90% deformation obtained by the traditional "one-step room temperature rolling-ordinary aging treatment" in Comparative Example 2, the alloy sheet obtained by the "first cryogenic rolling-intermediate aging treatment-second cryogenic rolling-ordinary aging treatment" in Comparative Example 1 showed an increase of 71 MPa in tensile strength and 9.5% IACS in electrical conductivity. Compared with the alloy sheet with 80% deformation obtained by the "room temperature rolling-ordinary aging treatment-room temperature rolling-ordinary aging treatment" in Comparative Example 3, the alloy sheet obtained by the "first cryogenic rolling-intermediate aging treatment-second cryogenic rolling-ordinary aging treatment" in Comparative Example 1 showed little difference in elongation and electrical conductivity, but a significant increase in tensile strength. It is evident that using two cryogenic rolling processes is beneficial for a significant increase in the tensile strength of the alloy sheet. Compared to Comparative Example 1, the alloy sheet obtained in Example 1 through "first cryogenic rolling - intermediate aging treatment - second cryogenic rolling - staged aging treatment" showed an increase in tensile strength of 93 MPa, an increase in elongation of 2.2%, and an increase in electrical conductivity to 37.3% IACS. This demonstrates that staged aging treatment after two cryogenic rolling processes is beneficial for further improving tensile strength, elongation, and electrical conductivity, significantly enhancing the overall performance of the alloy sheet. Compared to Example 1, the excessively small total deformation in Comparative Example 4 led to a reduction in internal energy storage. After staged aging treatment, the number of precipitated phases decreased, resulting in a significant decrease in the tensile strength, electrical conductivity, and elongation of the final Cu-Ni-Si alloy sheet. The tensile strength decreased by 156 MPa, the electrical conductivity decreased by 3% IACS, and the elongation decreased by 2.5%. Compared to Example 1, Comparative Example 5, due to its excessive total deformation, experienced self-annealing during the secondary cryogenic rolling process. This resulted in a reduction in the number of precipitates during the subsequent graded aging process, leading to a significant decrease in the tensile strength, electrical conductivity, and elongation of the final Cu-Ni-Si alloy sheet. The tensile strength decreased by 130 MPa, the electrical conductivity decreased by 1% IACS, and the elongation decreased by 1.5%. Compared to Example 1, Comparative Example 6, with its increased high-temperature stage of graded aging, experienced recrystallization of the alloy, resulting in coarser precipitates. The final Cu-Ni-Si alloy sheet showed little difference in electrical conductivity and elongation, but a significant decrease in tensile strength (by 147 MPa).

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-strength, high-ductility Cu-Ni-Si alloy sheet, characterized in that, The preparation method includes: A hot-rolled Cu-Ni-Si alloy is subjected to a first cryogenic rolling, an intermediate aging treatment, and a second cryogenic rolling to obtain a cryogenically rolled sheet. The total deformation after the first cryogenic rolling is 40-45% of the initial thickness of the hot-rolled Cu-Ni-Si alloy; the total deformation after the second cryogenic rolling is 70-80% of the initial thickness of the hot-rolled Cu-Ni-Si alloy. The second cryogenic rolling includes a first stage and a second stage, with the deformation per pass in the second stage being less than the deformation per pass in the first stage. The deformation per pass in the first stage is 8-10% of the initial thickness of the hot-rolled Cu-Ni-Si alloy; the deformation per pass in the second stage is 3-5% of the initial thickness of the hot-rolled Cu-Ni-Si alloy. The cryogenically rolled sheet is subjected to graded aging treatment to obtain a high-strength, high-ductility Cu-Ni-Si alloy sheet. The graded aging treatment includes a first-stage aging treatment and a second-stage aging treatment, wherein the temperature of the second-stage aging treatment is higher than that of the first-stage aging treatment. After the first-stage aging treatment, the temperature is increased to the temperature of the second-stage aging treatment at a heating rate of 30–40 °C / min. The temperature of the first-stage aging treatment is 150–250 °C. The temperature of the second-stage aging treatment is not higher than that of the intermediate aging treatment.

2. The preparation method according to claim 1, characterized in that, The hot-rolled Cu-Ni-Si alloy is obtained by solution treatment and hot rolling of the cast Cu-Ni-Si alloy.

3. The preparation method according to claim 2, characterized in that, The solution treatment temperature is the same as the hot rolling temperature. The solution treatment and hot rolling temperatures are 850~950℃; and / or the solution treatment time is 1~2h.

4. The preparation method according to claim 2, characterized in that, The total deformation after hot rolling is 70-80% of the initial thickness of the as-cast Cu-Ni-Si alloy; The deformation amount in each pass of the hot rolling process is 15-25% of the initial thickness of the as-cast Cu-Ni-Si alloy; and / or The heat preservation time between each pass during the hot rolling process is 5-10 minutes.

5. The preparation method according to claim 1, characterized in that, The deformation amount in each pass of the first deep cold rolling process is 5 to 10% of the initial thickness of the hot-rolled Cu-Ni-Si alloy.

6. The preparation method according to claim 1, characterized in that, The intermediate aging treatment is performed at a temperature of 400~500℃; and / or The intermediate aging process takes 60-120 minutes.

7. The preparation method according to claim 6, characterized in that, The intermediate aging treatment temperature is 425~475℃.

8. A high-strength, high-ductility Cu-Ni-Si alloy sheet, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

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