High-strength high-thermal-stability copper alloy and preparation method thereof

Abstract

The invention relates to a high-strength high-thermal-stability copper alloy and a preparation method thereof, the high-strength high-thermal-stability copper alloy is a Cu-Ni-Si-Cr alloy, and the high-strength high-thermal-stability copper alloy comprises the following components in percentage by mass: 0.20-0.50% of Cr element, 0.33-2.80% of Ni element, 0.053-0.66% of Si element, and the balance of Cu and inevitable impurities; the preparation method comprises the following steps: selecting Cu-Ni-Si alloy powder and Cu-Cr alloy powder as raw materials; the Cu-Cr alloy powder is subjected to mechanical alloying in a ball mill, so that Cr is completely dissolved into Cu crystal lattices, and Cr solid solution Cu powder is obtained; the temperature of the Cr solid solution Cu powder is reduced to-100 DEG C to 0 DEG C to continue mixing, after the powder recovers to the room temperature, Cu-Ni-Si alloy powder is added, then a binder is added, and mixed powder is obtained through mixing; the mixed powder is sintered and formed, and a sintered part is obtained; and carrying out solid solution on the sintered part, then carrying out cold rolling, recrystallizing to different degrees, then aging to a peak aging state, and finally preparing the Cu-Ni-Si-Cr alloy with high strength and high thermal stability. The method has the characteristics of high designability of microscopic components and tissues, multi-level regulation, good high-temperature stability, large performance regulation space, high level and the like.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy materials technology, specifically relating to a high-strength, high-thermal-stability copper alloy and its preparation method. Background Technology

[0002] CuNiSi alloys are precipitation-strength, high-strength, medium-conductivity alloys widely used in integrated circuit lead frames, high-speed railway contact wires, and other fields. In these alloys, the strengthening effect is primarily due to Ni-Si precipitates. However, these precipitates dissolve at temperatures above 700℃, making it difficult to meet the increasingly demanding requirements for temperature resistance, strength, and conductivity of copper alloys in the miniaturization and high-power applications of devices. Introducing Cr into CuNiSi alloys helps improve this problem. Because Cr has low solid solubility in Cu and the Cr3Si phase is highly stable, the Cr3Si phase, which forms in large quantities during conventional smelting, can pin grain boundaries at high temperatures, stabilizing the microstructure and improving high-temperature strength. However, these Cr3Si phases are generally micron-sized and prone to agglomeration. The copper alloy matrix structure correspondingly to their pinning effect is also relatively coarse, and their coarseness prevents them from providing further strengthening. Furthermore, the high melting point of the Cr3Si phase makes further control during subsequent heat treatment impossible. Currently, traditional smelting and casting methods struggle to simultaneously address issues such as the easy precipitation, large size, and agglomeration of Cr, and CuNiSi alloys exhibit poor high-temperature structural stability and low performance, severely limiting their application temperature range. There is an urgent need for a preparation method that can fully utilize the properties of Cr and its compounds while simultaneously improving the material's room-temperature and high-temperature structural stability and overall performance.

[0003] Patent application number 202410633795.3 discloses a near-net-shape forming method for preparing complex-shaped parts from ferrite-based ODS alloys. The method employs mechanical alloying, encapsulated hot isostatic pressing, and aging treatment to prepare a ferrite-based ODS alloy strengthened by both B2 and nano-oxides. This alloy exhibits strong compositional designability, minimal or even no segregation of alloying elements, a B2 phase volume fraction >35% after aging, and coarse-grained... This method offers numerous advantages, including a heterogeneous grain structure with fine grains, excellent mechanical properties, and near-net-shape forming. However, because it controls the transformation of residual austenite into a fine-grained region through cooling rate and maintains a coarse-grained region through high-temperature stable δ-phase to form a coarse-fine grain mixed heterostructure with little or no segregation of alloying elements, it lacks the chemical composition and the resulting gradients in micro-precipitates, hardness, and other distributions. Furthermore, it cannot form stable and continuously distributed macro-micro heterogeneous characteristics with multiple scales and sources of grain size. Its heterogeneous hierarchy, characteristics, and connotations are not rich enough, its tunability is insufficient, and its controllability is affected as the sample size increases. Summary of the Invention

[0004] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a high-strength and high-thermal-stability copper alloy and its preparation method. By mechanical alloying, the solubility of Cr in the Cu matrix is effectively increased, the grains are refined, and a large number of dislocations and other defects are introduced. Under normal conditions, the solubility of Cr in the Cu matrix is low and it is easy to precipitate, but it is thermally stable at high temperatures. The diffusion rate difference between Ni and Si in Cu is extremely large, and Cr and Si have high reactivity and Cr3Si is extremely stable at high temperatures. Through the design and utilization of these characteristics, a multi-scale continuous distribution and controllable, highly stable multi-macro and micro heterogeneous structure can be formed, which simultaneously has second phases with different types, sizes and distributions and corresponding non-uniform hardness distributions. Under the action of external loads and temperatures, the heterogeneous characteristics can continue to evolve. It has the characteristics of strong designability of micro-composition and structure, multi-level controllability, good high-temperature stability, large performance regulation space and high level.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is: A high-strength and high-thermal-stability copper alloy, the high-strength and high-thermal-stability copper alloy is a Cu-Ni-Si-Cr alloy, including the following components in mass percentage: Cr element is 0.20-0.50%, Ni element is 0.33-2.80%, Si element is 0.053-0.66%, and the balance is Cu and inevitable impurities.

[0006] A preparation method of a high-strength and high-thermal-stability copper alloy, including the following steps: Step 1, select Cu-Ni-Si alloy powder with a particle size distribution of 1-50 μm and Cu-Cr alloy powder with a particle size of 100-200 μm as raw materials; In the Cu-Ni-Si alloy powder, the mass ratio of Ni:Si is (4.2-6.3):1, and the ratio within the particle size distribution range can be adjusted. The mass fraction of Ni element is 2.00-3.00%, the mass fraction of Si element is 0.32-0.71%, and the mass fraction of Cu element is 97.68-96.29%; In the Cu-Cr alloy powder, the mass fraction of Cr element is 0.60-3.00%, and the mass fraction of Cu element is 99.40-97.00%; In the alloy prepared from Cu-Ni-Si alloy powder and Cu-Cr alloy powder, the mass fraction of Cr element satisfies 0.20-0.50%; Step 2: Mechanically alloy the Cu-Cr alloy powder in a ball mill to completely dissolve Cr into the Cu lattice, obtaining Cr-solidified Cu powder; lower the temperature of the Cr-solidified Cu powder to -100℃~0℃ and continue mixing for 1-10 hours. After the mixture is finished, wait for the powder to return to room temperature, add the corresponding Cu-Ni-Si alloy powder to obtain metal powder, then add a binder with a total mass fraction of 0.5% of the metal powder, and continue mixing for 0.5-5 hours to obtain mixed powder; the mass ratio of Cu-Cr alloy powder to Cu-Ni-Si alloy powder is (1-70):14. Step 3, sintering the mixed powder into shape: First, raise the temperature to 400-600℃ and the pressure to 1-5MPa, and hold for 30-100min to completely remove the binder by heat. Then, sinter at 850-1000℃ and 10-50MPa for 10-300min to obtain the sintered part. Step 4: The sintered part is solution-treated at 920-1000℃ for 1-2 hours, then cold-rolled by 50-80%, and recrystallized at 870-950℃ for 5-60 minutes to ensure that the recrystallization volume ratio of the alloy meets the requirement of 10%≤recrystallization volume ratio<100%. Then, it is aged at 450-600℃ for 0.7-6 hours to reach the peak aging state, and finally a high-strength and high-thermal-stability Cu-Ni-Si-Cr alloy is prepared.

[0007] The specific process of step 2 includes: In a ball mill at a speed of 500-1000 r / min, Cu-Cr alloy powder is mechanically alloyed at a ball-to-powder ratio of (9-50):1 under an argon atmosphere, so that Cr is completely dissolved into the Cu lattice to obtain Cr-solidified Cu powder. The temperature of the Cr-solidified Cu powder is lowered to -100℃~0℃, and mixing is continued for 1-10 h at a speed of 200-500 r / min, a ball-to-powder ratio of (9-50):1, and an argon atmosphere. After the mixing is completed, the powder is allowed to return to room temperature, and the corresponding Cu-Ni-Si alloy powder is added to obtain metal powder. Then, 0.5% of the total mass fraction of the metal powder is added as a binder, and mixing is continued for 0.5-5 h at a speed of 100-300 r / min, a ball-to-powder ratio of (9-30):1, and an argon atmosphere to obtain mixed powder. The mass ratio of Cu-Cr alloy powder to Cu-Ni-Si alloy powder is (1-70):14.

[0008] The adhesive used in step 2 is polyacrylamide.

[0009] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a microstructure design and powder metallurgy preparation method for a high-strength, high-thermal-stability copper alloy. By controlling the existence form of Cr element in the initial Cu-Cr alloy raw material powder and the manner and process of its introduction into the final alloy, the following is achieved: 1) The present invention fully refines copper powder through mechanical alloying in step 2, and utilizes the low solid solubility and high stability of Cr in Cu, so that its micro-nano size structure can be self-stabilized in the subsequent high temperature process.

[0010] 2) In steps 3 and 4, in the contact area with Cu-Ni-Si alloy powder, the Cu-Cr alloy powder that has been mechanically alloyed and dissolved in Cr in step 2 will become a micro Cr source donor, reacting with it to generate nano-scale Cr3Si, which provides high-temperature structural stability to the Cu-Ni-Si alloy powder with a wide and controllable particle size distribution selected in step 1. All of the above factors can effectively improve the strength of the material, and form a continuous macro-micro heterostructure of copper alloy matrix grains with high temperature stability and high basic strength from nano to micro scale.

[0011] 3) This invention introduces high-density defects and differences in alloy element concentration and diffusion ability between Cu-Ni-Si and Cu-Cr powders through low-temperature ball milling (-100℃~0℃) in step 2. During sintering in step 3, this promotes interdiffusion, controlling the formation of a non-uniform micro-heterogeneous structure with adjustable element and compound types, quantities, positions, distributions, and hardness through controlled sintering conditions. For example, the advantages of low-temperature, short-time densification using activated plasma sintering can better preserve fine-grained structures and fine precipitates (such as Cr particles and Cr-Ni phases), reduce the interdiffusion depth of alloy elements between Cu-Ni-Si and Cu-Cr powders, and enhance gradients in composition and hardness. This allows for control over the range and evolution of microstructure and properties during subsequent processing in step 4. In contrast, hot pressing requires higher sintering temperatures and longer times, resulting in greater diffusion depth, a wider range of influence, and smaller gradients in composition and hardness. Consequently, the microstructure and properties of the material will exhibit different response behaviors during subsequent processing in step 4. Based on this, by utilizing the differentiated response behavior of the macro- and micro-heterogeneous structures to external loads, the multi-directional evolution of successive recrystallization and aging behavior in different regions is promoted in step 4, thereby achieving a higher level and more complex level of heterogeneous structure control. Based on the existing high-temperature strengthening and microstructure stability mechanisms, and by leveraging the principles of heterogeneous deformation-induced strengthening and work hardening, a high-strength, high-thermal-stability, high-performance powder metallurgy copper alloy is prepared. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the sintering and control principle of the present invention. The diagram does not fully represent the actual multi-scale distribution of powder and grains, and is only a brief description of the principle of the present invention.

[0013] Figure 2 Transmission images of the adjacent positions of Cu-Ni-Si and Cu-Cr grains in Example 7.

[0014] Figure 3 This is a diagram showing the elemental distribution on both sides of the interface of a pure copper / Cu-Ni-Si-Cr alloy composite plate after diffusion. Detailed Implementation

[0015] The technical solution adopted by the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0016] like Figure 1As shown, the purpose of this invention is to directly design the multi-level microstructure of Cu-Ni-Si-Cr alloys through microstructure design and powder metallurgy preparation methods. This involves multi-level control over the type, size, distribution, and quantity of precipitated phases, as well as other microstructure characteristics, to solve problems such as easy precipitation, large size, and easy agglomeration of Cr in this type of alloy. First, low-cost, coarse Cu-Cr alloy powder is used as raw material. Since Cr has low solid solubility in Cu, a mechanical alloying method is further employed to ensure that even high-content Cr can be completely dissolved and incorporated into the Cu lattice. This will form the basis for the stability and high strength of the microstructure during subsequent sintering and heat treatment. Furthermore, a low-temperature ball milling method is used to effectively refine the Cr-dissolved Cu powder and introduce high-density defects and strain energy, aiming for a final macroscopic particle size (the alloy powder will have micro / nano-scale sub-structures) of no more than 20 μm or even submicron (which can be adjusted according to the diffusion ability of Si at the subsequent solid solution temperature), while simultaneously promoting the improvement of element diffusion ability. Finally, a binder is added while mixing with other powders for surface passivation and protection, reducing the risk of highly activated powder after ball milling. During sintering, chromium precipitates from the copper matrix of the original Cu-Cr alloy powder. This not only enables the self-stabilization of the micro-nano scale substructure in the original Cu-Cr alloy powder, but also forms a highly stable nanoscale Cr3Si phase at the interface with the Cu-Ni-Si alloy on the surface. This effectively stabilizes the microstructure of the initial Cu-Ni-Si alloy powder after sintering. Compared with the micron-scale Cr3Si phase in the traditional casting path, it provides additional strengthening to the copper matrix. Combined with the adjustable wide distribution of the original powder at the micron scale, a high-temperature stable, high-basic-strength multi-scale grain distribution heterostructure is formed with a continuous distribution from the micro-nano to the micron scale. Meanwhile, due to the elemental concentration gradient in Cu-Cr and Cu-Ni-Si alloy powders, interdiffusion will occur. However, the diffusion ability of Cr and Si in copper is relatively weak (far lower than that of Ni), especially after Cr precipitates, the diffusion ability is even worse. However, the high strain energy introduced by ball milling can appropriately promote diffusion. Therefore, a gradient distribution of elemental concentration and corresponding precipitate types (such as Cr-Ni or Cr-Ni-Si phases that would not be generated in Cu-Ni-Si-Cr alloys under conventional heat treatment) will be formed inside the original powder. The content, size, and corresponding hardness changes will be formed. By controlling the sintering conditions, a controllable micro-heterogeneous structure can be further formed. Based on this, cold deformation and different degrees of recrystallization treatment are applied to sintered parts. By utilizing the differences in macro- and micro-precipitates and hardness distribution, different responses to external loads are induced, and differentiated recrystallization and aging behaviors are stimulated (e.g., regions with high precipitate content can induce strain accumulation and recrystallization nucleation of the second phase; regions with high second phase and alloy element content have slow recrystallization rates and grain coarsening rates; regions with high alloy element content, defects such as dislocations and grain boundaries have fast precipitation and coarsening rates, etc.), thus promoting the controllable multi-level evolution of the material's heterostructure.Under the combined effect of the above factors, by introducing heterogeneous deformation-induced strengthening and work hardening through multi-level heterostructure, the properties of high-temperature stable Cr and its compounds are fully and efficiently utilized, comprehensively improving the strength, plasticity and other properties of Cu-Ni-Si-Cr alloys prepared by this method, and exhibiting high high-temperature structural stability.

[0017] Example 1 A method for preparing a high-strength, high-thermal-stability copper alloy includes the following steps: Step 1: Select Cu-Ni-Si alloy powder with a particle size distribution of 1-50 μm, wherein the Ni:Si mass ratio is 6.3:1, the Ni element mass fraction is 2.00%, the Si element mass fraction is 0.32%, and the Cu element mass fraction is 97.68%. Select Cu-Cr alloy powder with a particle size distribution of 100-200 μm, wherein the mass fraction of Cr element is 0.60% and the mass fraction of Cu element is 99.40%; Step 2: In a ball mill at a speed of 500 r / min, Cu-Cr alloy powder is mechanically alloyed at a ball-to-powder ratio of 9:1 under an argon atmosphere, so that Cr is completely dissolved in the Cu lattice instead of existing as a second-phase particle, resulting in Cr-solidified Cu powder. The temperature of the Cr-solidified Cu powder is lowered to 0℃ by repeatedly injecting and venting argon into the ball mill jar. Mixing continues for 1 hour at a speed of 200 r / min, a ball-to-powder ratio of 9:1, and an argon atmosphere. After the mixing is completed, the powder is allowed to return to room temperature. Cu-Ni-Si alloy powder is added according to a Cu-Cr alloy powder:Cu-Ni-Si alloy powder mass ratio of 7:14 to obtain metal powder. Then, 0.5% of polyacrylamide binder is added to the total mass fraction of the metal powder, and mixing continues for 0.5 hours at a speed of 100 r / min, a ball-to-powder ratio of 9:1, and an argon atmosphere to obtain mixed powder. Step 3: The mixed powder is sintered into shape using activated plasma sintering: First, the temperature is raised to 400℃ and the pressure is 5MPa, and the temperature is held for 100min to completely remove the polyacrylamide binder. Then, the mixture is sintered at 850℃ and 10MPa for 10min to obtain the sintered part. Step 4: The sintered part is solution-treated at 920℃ for 1 hour, then cold-rolled by 80%, and recrystallized at 870℃ for 5 minutes, so that the recrystallized grain volume accounts for 10% of the total grain volume of the alloy. Then, it is aged at 450℃ for 6 hours to reach the peak aging state, and finally a high-strength and high-thermal-stability Cu-Ni-Si-Cr alloy is prepared. Among them, Cr element accounts for 0.20wt% of the final Cu-Ni-Si-Cr alloy, Ni element accounts for 1.33wt% of the final Cu-Ni-Si-Cr alloy, Si element accounts for 0.21wt% of the final Cu-Ni-Si-Cr alloy, and the balance is Cu and unavoidable impurities.

[0018] The Cu-1.33Ni-0.21Si-0.20Cr(wt%) alloy has a yield strength of 400MPa, a tensile strength of 600MPa, and a heat resistance temperature of 500℃, which is higher than the 400℃ of the cast alloy of the same composition.

[0019] Example 2 A method for preparing a high-strength, high-thermal-stability copper alloy includes the following steps: Step 1: Select Cu-Ni-Si alloy powder with a particle size distribution of 1-50 μm, wherein the Ni:Si mass ratio is 4.2:1, the Ni element mass fraction is 3.00%, the Si element mass fraction is 0.71%, and the Cu element mass fraction is 96.29%. Select Cu-Cr alloy powder with a particle size distribution of 100-200 μm, wherein the mass fraction of Cr is 3.00% and the mass fraction of Cu is 97.00%. Step 2: In a ball mill at a speed of 1000 r / min, Cu-Cr alloy powder is mechanically alloyed at a ball-to-powder ratio of 50:1 under an argon atmosphere, so that Cr is completely dissolved in the Cu lattice instead of existing as a second-phase particle, resulting in Cr-solidified Cu powder. The temperature of the Cr-solidified Cu powder is lowered to -100℃ by repeatedly injecting and venting argon into the ball mill jar. Mixing continues for 10 hours at a speed of 500 r / min, a ball-to-powder ratio of 50:1, and an argon atmosphere. After the mixing is completed, the powder is allowed to return to room temperature. Cu-Cr alloy powder: Cu-Ni-Si alloy powder is added at a mass ratio of 1:14 to obtain metal powder. Then, 0.5% of the total mass fraction of the metal powder is added as a polyacrylamide binder. Mixing continues for 5 hours at a speed of 300 r / min, a ball-to-powder ratio of 30:1, and an argon atmosphere to obtain mixed powder. Step 3: The mixed powder is sintered into shape by hot pressing: First, the temperature is raised to 600℃ and the pressure is 1MPa, and the temperature is held for 30 minutes to completely remove the polyacrylamide binder. Then, the mixture is sintered at 1000℃ and 50MPa for 300 minutes to obtain the sintered part. Step 4: The sintered part is solution-treated at 1000℃ for 2 hours, then cold-rolled by 50%, and recrystallized at 950℃ for 60 minutes, so that the recrystallized grain volume of the alloy accounts for 95% of the total grain volume of the alloy. Then it is aged at 600℃ for 0.7 hours to the peak aging state, and finally a high-strength and high-thermal-stability Cu-Ni-Si-Cr alloy is prepared. Of the final Cu-Ni-Si-Cr alloy, Cr accounts for 0.20 wt%, Ni accounts for 2.80 wt%, Si accounts for 0.66 wt%, and the balance is Cu and unavoidable impurities.

[0020] The Cu-2.80Ni-0.66Si-0.20Cr(wt%) alloy has a yield strength of 750MPa, a tensile strength of 820MPa, and a heat resistance temperature of 500℃, which is higher than the 400℃ of the cast alloy of the same composition.

[0021] Example 3 A method for preparing a high-strength, high-thermal-stability copper alloy includes the following steps: Step 1: Select Cu-Ni-Si alloy powder with a particle size distribution of 1-50 μm, wherein the Ni:Si mass ratio is 5.0:1, the Ni element mass fraction is 2.50%, the Si element mass fraction is 0.50%, and the Cu element mass fraction is 97.00%. Select Cu-Cr alloy powder with a particle size distribution of 100-200 μm, wherein the mass fraction of Cr is 1.50% and the mass fraction of Cu is 98.50%. Step 2: In a ball mill at 700 r / min, Cu-Cr alloy powder is mechanically alloyed at a ball-to-powder ratio of 30:1 under an argon atmosphere, so that Cr is completely dissolved in the Cu lattice instead of existing as a second-phase particle, resulting in Cr-solidified Cu powder. The temperature of the Cr-solidified Cu powder is lowered to -80℃ by repeatedly injecting and venting argon into the ball mill jar. Mixing continues for 5 hours at 300 r / min, a ball-to-powder ratio of 40:1, and an argon atmosphere. After the mixing is completed, the powder is allowed to return to room temperature. Cu-Cr alloy powder: Cu-Ni-Si alloy powder mass ratio of 5.4:14 is added to obtain metal powder. Then, 0.5% of the total mass fraction of the metal powder is added as a polyacrylamide binder. Mixing continues for 2 hours at 200 r / min, a ball-to-powder ratio of 20:1, and an argon atmosphere to obtain mixed powder. Step 3, sinter the mixed powder into a formed part by hot press sintering: First, raise the temperature to 500 °C and the pressure to 3 MPa, and keep the temperature for 50 min to completely remove the polyacrylamide binder. Then sinter at a temperature of 900 °C and a pressure of 40 MPa for 240 min to obtain a sintered part; Step 4, solutionize the sintered part at 950 °C for 1.5 h, then cold roll it by 70%, recrystallize it at 920 °C for 40 min, so that the volume of the recrystallized grains of the alloy accounts for 80% of the total grain volume of the alloy. Then age it at 510 °C for 2.5 h to the peak aging state, and finally prepare a high-strength and high-thermal stability Cu-Ni-Si-Cr alloy; among them, the Cr element accounts for 0.42 wt% of the finally prepared Cu-Ni-Si-Cr alloy, the Ni element accounts for 1.80 wt% of the finally prepared Cu-Ni-Si-Cr alloy, the Si element accounts for 0.36 wt% of the finally prepared Cu-Ni-Si-Cr alloy, and the balance is Cu and unavoidable impurities.

[0022] The yield strength of the Cu-1.80Ni-0.36Si-0.42Cr (wt%) alloy is 420 MPa, the tensile strength is 610 MPa, and the heat-resistant temperature is 550 °C, which is higher than 400 °C of the cast alloy with the same composition.

[0023] Example 4 A preparation method of a high-strength and high-thermal stability copper alloy, comprising the following steps: Step 1, select Cu-Ni-Si alloy powder with a particle size distribution of 1-50 μm, wherein the mass ratio of Ni:Si is 5.0:1, the mass fraction of Ni element is 2.80%, the mass fraction of Si element is 0.56%, and the mass fraction of Cu element is 96.64%; Select Cu-Cr alloy powder with a particle size distribution of 100-200 μm, wherein the mass fraction of Cr element is 2.00%, and the mass fraction of Cu element is 98.00%; Step 2, in a ball mill with a rotation speed of 600 r / min, carry out mechanical alloying on the Cu-Cr alloy powder under an argon atmosphere with a ball-to-material ratio of 30:1, so that Cr is completely dissolved into the Cu lattice instead of existing as second-phase particles, and obtain Cr-dissolved Cu powder. By the form of reciprocally charging and discharging argon into and out of the ball mill tank, lower the temperature of the Cr-dissolved Cu powder to -50 °C, and continue to mix for 4 h under a rotation speed of 350 r / min, a ball-to-material ratio of 20:1, and an argon atmosphere. After completion, wait for the powder to return to room temperature, and add the corresponding Cu-Ni-Si alloy powder according to the mass ratio of Cu-Cr alloy powder:Cu-Ni-Si alloy powder of 2.5:14 to obtain metal powder. Then add a polyacrylamide binder with a total mass fraction of 0.5% of the metal powder, and continue to mix for 2 h under a rotation speed of 150 r / min, a ball-to-material ratio of 15:1, and an argon atmosphere to obtain a mixed powder; Step 3: Sinter the mixed powder into a formed part by using activated plasma sintering. First, raise the temperature to 500 °C and the pressure to 2 MPa, and keep the temperature for 40 min to completely remove the polyacrylamide binder. Then, sinter at a temperature of 900 °C and a pressure of 20 MPa for 30 min to obtain a sintered part. Step 4: Solutionize the sintered part at a temperature of 970 °C for 1 h, then cold roll it by 55%, and recrystallize it at a temperature of 900 °C for 60 min to make the volume of the recrystallized grains of the alloy account for 90% of the total grain volume of the alloy. Then, age it at a temperature of 550 °C for 2 h to the peak aging state. Finally, a high-strength and high-thermal-stability Cu-Ni-Si-Cr alloy is prepared. Among them, the Cr element accounts for 0.30 wt% of the finally prepared Cu-Ni-Si-Cr alloy, the Ni element accounts for 2.38 wt% of the finally prepared Cu-Ni-Si-Cr alloy, the Si element accounts for 0.48 wt% of the finally prepared Cu-Ni-Si-Cr alloy, and the balance is Cu and inevitable impurities.

[0024] The yield strength of the Cu-2.38Ni-0.48Si-0.30Cr (wt%) alloy is 560 MPa, the tensile strength is 670 MPa, and the heat-resistant temperature is 520 °C, which is higher than 400 °C of the casting alloy with the same composition.

[0025] Example 5 A preparation method of a high-strength and high-thermal-stability copper alloy, comprising the following steps: Step 1: Select Cu-Ni-Si alloy powder with a particle size distribution of 1 - 50 μm. Among them, the mass ratio of Ni:Si is 4.2:1, the mass fraction of the Ni element is 2.50%, the mass fraction of the Si element is 0.59%, and the mass fraction of the Cu element is 96.91%. Select Cu-Cr alloy powder with a particle size distribution of 100 - 200 μm. Among them, the mass fraction of the Cr element is 0.60%, and the mass fraction of the Cu element is 99.40%. Step 2: In a ball mill with a rotational speed of 900 r / min, under an argon atmosphere with a ball-to-material ratio of 40:1, mechanical alloying of the Cu-Cr alloy powder is carried out to completely dissolve Cr into the Cu lattice rather than exist in the form of second-phase particles, obtaining Cr-dissolved Cu powder. By reciprocally charging and discharging argon into the ball mill tank, the temperature of the Cr-dissolved Cu powder is reduced to -90 °C. At a rotational speed of 400 r / min, a ball-to-material ratio of 50:1, and under an argon atmosphere, mixing continues for 8 h. After completion, when the powder returns to room temperature, according to the mass ratio of Cu-Cr alloy powder:Cu-Ni-Si alloy powder of 70:14, the corresponding Cu-Ni-Si alloy powder is added to obtain metal powder. Then, a polyacrylamide binder with a mass fraction of 0.5% of the total mass of the metal powder is added, and mixing continues for 5 h at a rotational speed of 300 r / min, a ball-to-material ratio of 20:1, and under an argon atmosphere to obtain a mixed powder; Step 3: The mixed powder is sintered and formed by hot pressing sintering: First, the temperature is raised to 550 °C and the pressure is 3 MPa, and heat preservation is carried out for 60 min to completely remove the polyacrylamide binder. Sintering is carried out at a temperature of 1000 °C and a pressure of 40 MPa for 200 min to obtain a sintered part; Step 4: The sintered part is solid-solved at a temperature of 950 °C for 1.5 h, then cold-rolled by 60%, recrystallized at a temperature of 915 °C for 45 min, with a recrystallization degree of 92%. Then, aging is carried out at a temperature of 550 °C for 4 h to reach the peak aging state. Finally, a high-strength and high-thermal stability Cu-Ni-Si-Cr alloy is prepared; among them, the Cr element accounts for 0.50 wt% of the finally prepared Cu-Ni-Si-Cr alloy, the Ni element accounts for 0.42 wt% of the finally prepared Cu-Ni-Si-Cr alloy, the Si element accounts for 0.10 wt% of the finally prepared Cu-Ni-Si-Cr alloy, and the balance is Cu and unavoidable impurities.

[0026] The yield strength of the Cu-0.42Ni-0.10Si-0.50Cr (wt%) alloy is 200 MPa, the tensile strength is 450 MPa, and the heat-resistant temperature is 500 °C, which is higher than 400 °C of the cast alloy with the same composition.

[0027] Example 6 A preparation method of a high-strength and high-thermal stability copper alloy includes the following steps: Step 1: Select Cu-Ni-Si alloy powder with a particle size distribution of 1 - 50 μm, where the mass ratio of Ni:Si is 6.2:1, the mass fraction of the Ni element is 2.00%, the mass fraction of the Si element is 0.32%, and the mass fraction of the Cu element is 97.68%; Select Cu-Cr alloy powder with a particle size distribution of 100 - 20 μm, where the mass fraction of the Cr element is 0.60% and the mass fraction of the Cu element is 99.40%; Step 2: In a ball mill at 1000 r / min, Cu-Cr alloy powder is mechanically alloyed at a ball-to-powder ratio of 40:1 under an argon atmosphere, so that Cr is completely dissolved in the Cu lattice instead of existing as a second-phase particle, resulting in Cr-solidified Cu powder. The temperature of the Cr-solidified Cu powder is lowered to -100℃ by repeatedly injecting and venting argon into the ball mill jar. Mixing continues for 2 hours at 400 r / min, a ball-to-powder ratio of 30:1, and an argon atmosphere. After the mixing is completed, the powder is allowed to return to room temperature. Cu-Ni-Si alloy powder is added at a mass ratio of Cu-Cr alloy powder to Cu-Ni-Si alloy powder of 70:14 to obtain metal powder. Then, 0.5% of the total mass fraction of the metal powder is added as a polyacrylamide binder, and mixing continues for 2 hours at 300 r / min, a ball-to-powder ratio of 30:1, and an argon atmosphere to obtain mixed powder. Step 3: The mixed powder is sintered into shape using activated plasma sintering: First, the temperature is raised to 450℃ and the pressure is 1MPa, and the temperature is held for 75 minutes to completely remove the polyacrylamide binder. Then, the mixture is sintered at 850℃ and 10MPa for 10 minutes to obtain the sintered part. Step 4: The sintered part is solution-treated at 920℃ for 1 hour, then cold-rolled by 50%, and recrystallized at 870℃ for 10 minutes, so that the recrystallized grain volume accounts for 60% of the total grain volume of the alloy. Then, it is aged at 500℃ for 3 hours to reach the peak aging state, and finally a high-strength and high-thermal-stability Cu-Ni-Si-Cr alloy is prepared. Among them, Cr element accounts for 0.50wt% of the final Cu-Ni-Si-Cr alloy, Ni element accounts for 0.33wt% of the final Cu-Ni-Si-Cr alloy, Si element accounts for 0.053wt% of the final Cu-Ni-Si-Cr alloy, and the balance is Cu and unavoidable impurities.

[0028] The Cu-0.33Ni-0.053Si-0.50Cr (wt%) alloy has a yield strength of 180 MPa, a tensile strength of 420 MPa, and a heat resistance temperature of 450℃, which is higher than the 400℃ of the cast alloy of the same composition.

[0029] Example 7 A method for preparing a high-strength, high-thermal-stability copper alloy includes the following steps: Step 1: Select Cu-Ni-Si alloy powder with a particle size distribution of 1-50 μm, wherein the Ni:Si mass ratio is 4.4:1, the Ni element mass fraction is 3.00%, the Si element mass fraction is 0.68%, and the Cu element mass fraction is 96.32%. Select Cu-Cr alloy powder with a particle size distribution of 100-200 μm, wherein the mass fraction of Cr is 3.00% and the mass fraction of Cu is 97.00%. Step 2: In a ball mill at 800 r / min, Cu-Cr alloy powder is mechanically alloyed at a ball-to-powder ratio of 20:1 under an argon atmosphere, so that Cr is completely dissolved in the Cu lattice instead of existing as a second-phase particle, resulting in Cr-solidified Cu powder. The temperature of the Cr-solidified Cu powder is lowered to -80℃ by repeatedly injecting and venting argon into the ball mill jar. Mixing continues for 6 hours at 400 r / min, a ball-to-powder ratio of 40:1, and an argon atmosphere. After the mixing is completed, the powder is allowed to return to room temperature. Cu-Cr alloy powder: Cu-Ni-Si alloy powder mass ratio of 2.8:14 is added to obtain metal powder. Then, 0.5% of the total mass fraction of the metal powder is added as a polyacrylamide binder. Mixing continues for 4 hours at 250 r / min, a ball-to-powder ratio of 15:1, and an argon atmosphere to obtain mixed powder. Step 3: The mixed powder is sintered into shape by hot pressing: First, the temperature is raised to 500℃ and the pressure is 2MPa, and the temperature is held for 40min to completely remove the polyacrylamide binder. Then, it is sintered at 950℃ and 40MPa for 180min to obtain the sintered part. Step 4: The sintered part is solution-treated at 920℃ for 1 hour, then cold-rolled by 55%, recrystallized at 920℃ for 60 minutes to achieve a recrystallization degree of 95%, and then aged at 510℃ for 3 hours to reach the peak aging state, finally producing a high-strength, high-thermal-stability Cu-Ni-Si-Cr alloy. The alloy composition is as follows: Cr accounts for 0.50 wt%, Ni accounts for 2.50 wt%, Si accounts for 0.57 wt%, and the balance is Cu and unavoidable impurities. This achieves a yield strength of 700 MPa, a tensile strength of 850 MPa, and an elongation of 12% for the Cu-2.50Ni-0.57Si-0.50Cr (wt%) alloy, with the softening temperature increased from approximately 400℃ for conventionally cast alloys of the same composition to over 600℃.

[0030] Figure 2 The transmission results of the alloy in the solid solution state prepared in this embodiment are shown. It can be seen that there are few precipitates on the Cu-Ni-Si powder side, while the Cu-Cr powder side and the boundaries of the two original powders benefit from element diffusion and the thermal stability of different precipitates, forming a variety of nanoscale precipitates, which stabilize the original powder boundaries (thus exhibiting high high-temperature microstructure and performance stability), showing obvious heterogeneous structure characteristics, and achieving the design effect of this invention.

[0031] like Figure 3As shown, the elemental distribution on both sides of the interface between a pure Cu plate and the Cu-Ni-Si-Cr alloy plate involved in this invention after diffusion at 900℃ for 1 hour is illustrated. It is evident that Ni's diffusion ability in the pure copper matrix is ​​far stronger than that of Si and Cr (Ni's diffusion distance is 25 μm, Si's is 2 μm, and Cr is close to 0 μm). This forms a crucial basis for the microstructure design and control in this invention. Specifically, by controlling the temperature and time during sintering and solution treatment, and considering the initial powder particle size, the diffusion distance and concentration of alloying elements in the copper matrix can be directly controlled by utilizing the differences in their diffusion abilities. This allows for the control of heterogeneous structural characteristics such as microstructure, grain size, and the range and gradient of non-uniform hardness distribution. This, in turn, influences the evolution of heterogeneous characteristics under subsequent thermomechanical treatment.

[0032] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A high-strength, high-thermal-stability copper alloy, characterized in that, The high-strength, high-thermal-stability copper alloy is a Cu-Ni-Si-Cr alloy, comprising the following components by mass percentage: Cr 0.20-0.50%, Ni 0.33-2.80%, Si 0.053-0.66%, with the balance being Cu and unavoidable impurities.

2. A method for preparing a high-strength, high-thermal-stability copper alloy, characterized in that, Includes the following steps: Step 1: Select Cu-Ni-Si alloy powder with a particle size distribution of 1-50μm and Cu-Cr alloy powder with a particle size distribution of 100-200μm as raw materials; In the Cu-Ni-Si alloy powder, the Ni:Si mass ratio is (4.2-6.3):1, and the proportion can be adjusted within the particle size distribution range. The mass fraction of Ni element is 2.00-3.00%, the mass fraction of Si element is 0.32-0.71%, and the mass fraction of Cu element is 97.68-96.29%. In the Cu-Cr alloy powder, the mass fraction of Cr is 0.60-3.00%, and the mass fraction of Cu is 99.40-97.00%. Alloys prepared from Cu-Ni-Si alloy powder and Cu-Cr alloy powder contain a Cr element mass fraction of 0.20-0.50%. Step 2: Mechanically alloy the Cu-Cr alloy powder in a ball mill to completely dissolve Cr into the Cu lattice, obtaining Cr-solidified Cu powder; lower the temperature of the Cr-solidified Cu powder to -100℃~0℃ and continue mixing for 1-10 hours. After the mixture is finished, wait for the powder to return to room temperature, add the corresponding Cu-Ni-Si alloy powder to obtain metal powder, then add a binder with a total mass fraction of 0.5% of the metal powder, and continue mixing for 0.5-5 hours to obtain mixed powder; the mass ratio of Cu-Cr alloy powder to Cu-Ni-Si alloy powder is (1-70):

14. Step 3, sintering the mixed powder into shape: First, raise the temperature to 400-600℃ and the pressure to 1-5MPa, and hold for 30-100min to completely remove the binder by heat. Then, sinter at 850-1000℃ and 10-50MPa for 10-300min to obtain the sintered part. Step 4: The sintered part is solution-treated at 920-1000℃ for 1-2 hours, then cold-rolled by 50-80%, and recrystallized at 870-950℃ for 5-60 minutes to ensure that the recrystallization volume ratio of the alloy meets the requirement of 10%≤recrystallization volume ratio<100%. Then, it is aged at 450-600℃ for 0.7-6 hours to reach the peak aging state, and finally a high-strength and high-thermal-stability Cu-Ni-Si-Cr alloy is prepared.

3. The method for preparing a high-strength, high-thermal-stability copper alloy according to claim 1, characterized in that, The specific process of step 2 includes: In a ball mill at a speed of 500-1000 r / min, Cu-Cr alloy powder is mechanically alloyed at a ball-to-powder ratio of (9-50):1 under an argon atmosphere, so that Cr is completely dissolved into the Cu lattice to obtain Cr-solidified Cu powder. The temperature of the Cr-solidified Cu powder is lowered to -100℃~0℃, and mixing is continued for 1-10 h at a speed of 200-500 r / min, a ball-to-powder ratio of (9-50):1, and an argon atmosphere. After the mixing is completed, the powder is allowed to return to room temperature, and the corresponding Cu-Ni-Si alloy powder is added to obtain metal powder. Then, 0.5% of the total mass fraction of the metal powder is added as a binder, and mixing is continued for 0.5-5 h at a speed of 100-300 r / min, a ball-to-powder ratio of (9-30):1, and an argon atmosphere to obtain mixed powder. The mass ratio of Cu-Cr alloy powder to Cu-Ni-Si alloy powder is (1-70):

14.

4. The method for preparing a high-strength, high-thermal-stability copper alloy according to claim 2 or 3, characterized in that, The adhesive used in step 2 is polyacrylamide.

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