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

Abstract

The invention discloses a high-strength high-thermal-stability copper alloy and a smelting preparation method thereof, and belongs to the technical field of alloy smelting, and the method comprises the following steps: taking high-purity Cu, high-purity Ni, high-purity Si and high-purity Cr as raw materials, smelting the raw materials until the raw materials are molten into a liquid phase and uniformly mixed, performing spray casting or die casting, and performing water-cooling forming to obtain a copper alloy ingot; and the high-strength high-thermal-stability copper alloy is obtained after homogenization heat treatment, water-cooling quenching and thermal mechanical treatment. The purity of the raw materials is 99.9%; the smelting temperature ranges from 1800 DEG C to 2000 DEG C. The temperature is higher than the melting point of Cr3Si to ensure that Cr and compounds thereof are completely molten into a liquid phase to be uniformly distributed in the alloy, and is lower than the boiling point of Cu, so that evaporation loss of Cu is avoided. The premature precipitation of the Cr element in the conventional smelting process is effectively prevented, and the problems that the Cr and the compound thereof are thick and easy to agglomerate and the strength improvement effect is limited in the traditional smelting process are solved. The material structure is refined, the high-temperature structure stability of the material is improved, the problem that a dominant strengthening phase is prone to redissolution in a high-temperature environment is solved, and the strength and the conductivity are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of alloy smelting, and in particular relates to a high-strength and high-thermal stability copper alloy and a smelting preparation method thereof. Background Art

[0002] Copper alloys are widely used in electronics, communications, transportation, and other fields due to their excellent electrical, thermal, and mechanical properties. CuNiSi alloys, as a typical precipitation-strengthened alloy, are widely used in integrated circuit lead frames, high-speed railway contact wires, and other fields. However, with the rapid development of the electronic information industry, the performance requirements for copper alloy materials are constantly increasing, especially in terms of strength, conductivity, and high-temperature performance.

[0003] CuNiSi alloy is a high-strength medium-conductivity alloy, but its dominant Ni-Si precipitated phase, which plays a strengthening role, will quickly dissolve back after 600°C, resulting in unstable and low-level high-temperature microstructure and performance. Usually, the introduction of a fourth component Cr into CuNiSi alloys helps to improve this problem. That is, by utilizing the low solubility of Cr in Cu and the extremely high stability of the Cr3Si phase, a Cr3Si phase is formed during conventional smelting, thereby playing a role in heterogeneous phase nucleation, pinning grain boundary movement, and refining the solidification structure. According to Zener pinning theory, these Cr3Si phases formed in this process are generally on the micron scale, and the copper alloy matrix structure that matches its pinning effect is also relatively coarse, that is, its stabilizing effect on the structure is actually relatively limited and cannot provide a strengthening effect. The Cr3Si phase has a high melting point and is difficult to dissolve back during the subsequent homogenization heat treatment process. If the temperature can be precisely controlled during the initial smelting process to ensure complete melting of the Cr phase and sufficient mixing of the liquid phases of various elements, and then rapid cooling is performed, it is expected that the Cr element will be precipitated in the form of a nanoscale phase, which can continue to transform into a high-temperature stable phase after thermomechanical treatment. This will greatly improve the stability and level of the high-temperature structure and mechanical properties of this series of alloys.

[0004] CN107119247A discloses a heat treatment method that can improve the performance stability of medium- and high-tonnage smelting CuNiSiCr alloys. This method utilizes a reasonable combination of sufficient solution temperature and time, as well as appropriate cold deformation and recrystallization temperature, to promote the compositional uniformity of large parts and reduce the extent of material performance degradation caused by grain and precipitate coarsening. This process can ensure a high solution temperature and a long solution time, fully promoting the composition and structural uniformity within large structural parts. However, there is still the problem of not being able to rationally utilize the characteristics of the Cr3Si phase in the alloy and not being able to solve the problem of coarse Cr3Si phases that are easy to agglomerate to obtain better room temperature high temperature structural performance uniformity and level. CN117626050A proposes a high-strength conductive copper alloy that mainly contains four elements: Cu, Ni, Si, and Cr. By precisely controlling the mass fraction and atomic ratio of each element, multiple precipitate phases are formed to improve the overall performance of the alloy. However, there is still the problem of how to further optimize the process parameters to improve the overall performance of the alloy.

[0005] Currently, traditional melting and casting methods are unable to simultaneously address the problems of Cr element precipitation, coarse size, and easy agglomeration. In addition, CuNiSi alloys have poor high-temperature microstructure stability, low performance level, and severely limited application temperature range. Although high-temperature and long-term homogenization annealing can alleviate the unevenness of casting composition and structure to a certain extent, it often results in excessively coarse structure and still cannot solve the low high-temperature microstructure and performance stability of such alloys. Therefore, there is an urgent need for a new melting and heat treatment method that can achieve the rational utilization of the characteristics of Cr elements and their compounds while improving the room temperature and high-temperature microstructure stability of the material. Summary of the Invention

[0006] In order to overcome the shortcomings 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 a smelting preparation method thereof, so as to solve the technical problems of the existing CuNiSi alloys such as coarse and easy agglomeration of Cr elements and their compounds, unstable structure and low performance level.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention discloses a smelting preparation method of a high-strength and high-thermal stability copper alloy, comprising: High-purity Cu, high-purity Ni, high-purity Si and high-purity Cr are used as raw materials, smelted until the raw materials are melted into a liquid phase and mixed evenly, then spray-casted or die-cast and water-cooled to obtain a copper alloy ingot; after homogenization heat treatment, water-cooling quenching and thermo-mechanical treatment, a high-strength and high-thermal-stability copper alloy is obtained; the purity of the raw materials is 99.9%; the smelting temperature is 1800-2000°C.

[0008] Preferably, the raw material includes Ni: 2-3wt%, Cr: 0.3-0.6wt% in mass percentage; according to the specific Ni and Cr masses, the total Si mass in the raw material is obtained by converting and adding them according to the atomic ratio of Ni2Si and Cr3Si.

[0009] Preferably, the melting method includes vacuum induction melting or electron beam melting.

[0010] Preferably, the uniform heat treatment conditions include: heat treatment at 900-950° C. for 1-12 hours.

[0011] Preferably, the thermomechanical treatment conditions include: deformation recrystallization treatment and deformation aging treatment.

[0012] Further preferably, the conditions of the deformation recrystallization treatment include: a deformation amount of 0.5-2; a crystallization temperature of 900-930° C.; and a crystallization time of 0.5-2 h.

[0013] More preferably, the deformation recrystallization treatment is carried out by cold rolling, cold heading and cold forging in 3-4 passes.

[0014] Further preferably, the conditions of the deformation aging treatment include: a deformation amount of 0.2-0.4; an aging temperature of 450-550° C.; and an aging time of 0.5-6 h.

[0015] Further preferably, the deformation method of the deformation aging treatment is: cold rolling, cold heading and cold forging, which are completed in 1-2 passes.

[0016] The present invention also discloses a high-strength and high-thermal stability copper alloy, which is prepared by adopting the above-mentioned smelting preparation method of the high-strength and high-thermal stability copper alloy.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present application discloses a smelting preparation method for a high-strength and high-thermal-stability copper alloy. During the smelting stage, when the temperature exceeds the melting point of the chromium-silicon compound, the chromium element can be fully dissolved in the liquid alloy. During the rapid solidification process, nickel, chromium, and silicon elements form a metastable phase in a non-equilibrium state. Such nanoscale precipitates undergo element migration and reorganization during the subsequent homogenization heat treatment process. The water-cooling quenching process effectively fixes the high-temperature organizational state, inhibits element segregation and coarsening and agglomeration of the second phase, and ensures the formation of a uniformly distributed nanoscale complex second phase. Thermomechanical treatment introduces crystal defects such as dislocations through plastic deformation, and cooperates with the existing nanoscale complex second phase to provide nucleation sites and additional high-temperature stability for organizational refinement and precipitation phase formation during subsequent recrystallization and aging. The present invention adopts a vacuum induction melting or electron beam melting process with precise temperature control to melt the raw materials to prepare alloy ingots. The temperature of the smelting process is controlled to be in the range of 1800~2000℃. This temperature range is higher than the melting point of Cr3Si (about 1770℃), which can ensure that Cr and its compounds are completely melted into a liquid phase with sufficient fluidity and evenly distributed in the alloy. At the same time, it should be as low as possible below the boiling point of Cu (about 2562℃) to avoid evaporation loss of Cu. After smelting, the initial alloy ingot is obtained by spray casting or die casting and water cooling. Rapid cooling can produce dispersed nano-scale Ni-Cr-Si precipitation phase in the alloy, that is, the initial phase is close to Ni 31 Si 12 During further high-temperature homogenization, recrystallization, and aging treatments, Cr gradually migrates and dissolves, allowing this complex phase to continue evolving to a Cr:Si atomic ratio close to 3, resulting in extremely high thermal stability (exceeding the melting point of copper alloys). During deformation recrystallization, these nanoscale complex Ni-Cr-Si precipitates exert a strong pinning effect on the recrystallized and refined matrix, ensuring full microstructure refinement and high-temperature stability. During deformation and aging, these phases, along with deformation-induced defects such as dislocations, act as nanoscale heterogeneous nucleation sites, promoting the precipitation of conventional Ni2Si and providing additional high-temperature stabilization to these newly formed NiSi phases. Together, they strengthen the matrix, improving both the material's strength and high-temperature stability. This achieves a uniform distribution of alloying elements in the liquid phase, effectively inhibiting premature precipitation and coarsening of chromium during solidification. The resulting nanoscale composite precipitates are structurally stable at high temperatures, significantly enhancing the material's high-temperature strength retention. The synergistic effect of the multi-stage hot working process results in full microstructure refinement and significantly enhanced precipitation strengthening, resulting in excellent mechanical properties while maintaining high electrical conductivity.

[0018] Furthermore, by limiting the addition ratio of nickel and chromium and establishing a dynamic calculation mechanism for silicon content, the generation ratio of nickel-silicon phase and chromium-silicon phase can be precisely controlled before smelting. When the nickel content is 2-3%, it can ensure the formation of sufficient Ni2Si phase as a matrix strengthening phase; when the chromium content is 0.3-0.6%, it can generate Cr3Si phase without exceeding the solid solubility of the copper matrix. According to the actual content of nickel and chromium, the corresponding silicon demand is calculated respectively, so that the silicon element can fully meet the demand for the formation of intermediate compounds, avoiding the excess silicon element causing the solid-solution silicon atoms to reduce conductivity or the insufficient silicon element causing incomplete compound formation, and ensuring that the alloy has a high electrical conductivity after aging. This dynamic matching method based on atomic ratio establishes the chemical equilibrium relationship between nickel, chromium and silicon in the composition design stage, laying the foundation for the formation of uniformly distributed composite precipitation phases in the subsequent smelting process. Precise control of the alloy composition is achieved, forming a fine and stable Ni-Cr-Si phase composite structure during the rapid solidification stage, so that the nanoscale precipitated phase is evenly distributed in the matrix, thereby significantly improving the material's organizational stability and mechanical properties in high-temperature environments.

[0019] Furthermore, vacuum induction melting uses electromagnetic fields to create forced convection in the melt, promoting the diffusion and mixing of nickel, chromium, and silicon elements. The vacuum environment eliminates the interference of gas inclusions on the uniformity of the melt, achieving complete melting and uniform distribution of each element in the copper matrix.

[0020] Furthermore, during the casting process, the heat dissipation conditions of the mold match the solidification shrinkage behavior of the alloy liquid, promoting the rapid formation of nanoscale complex precipitate phases and their uniform distribution in space. Traditional gravity casting is prone to premature precipitation, severe coarsening and agglomeration of Cr and its compounds due to insufficient cooling rate, and although continuous casting can increase the cooling rate, it is limited by equipment conditions and difficult to flexibly adjust the molding parameters. The present invention retains the adaptability of spray casting and die casting processes to complex shapes by selecting two molding methods in parallel, and its forced solidification characteristics achieve precise control of the microstructure. It effectively solves the problem of premature precipitation, coarsening and agglomeration of Cr elements and their compounds caused by insufficient cooling rate in the alloy liquid after smelting during the molding process.

[0021] Furthermore, by controlling the homogenization temperature at 900~950℃, the Cr element inside the alloy gradually diffuses into the Ni-Cr-Si phase at high temperature, while suppressing the excessive growth of grains and precipitates. The heat treatment time is limited to 1-12 hours. Under the premise of ensuring the appropriate degree of atomic migration of the Ni-Cr-Si composite phase, the loss of control of the precipitate size caused by long-term high-temperature treatment is avoided. The problem of coarsening of grains and precipitates caused by traditional high-temperature annealing is solved, so that the alloy ingot treated by homogenization can maintain a fine-grained structure during subsequent cold deformation and aging. At the same time, it is beneficial to provide additional high-temperature stability from the existing Ni-Cr-Si phase to the newly generated nickel-silicon phase through heterogeneous nucleation, providing the necessary organizational conditions for obtaining high-strength and high-thermal stability copper alloys.

[0022] Furthermore, the deformation recrystallization treatment drives dynamic recrystallization through the deformation energy stored during cold deformation, significantly reducing the matrix grain size. Simultaneously, the Ni-Cr-Si complex phase formed during melting remains stable at high temperatures and pins grain boundaries, inhibiting grain coarsening. The deformation aging treatment, through the dislocations generated by pre-deformation, provides rapid diffusion channels for the migration of elements such as Ni and Si. These dislocations, combined with the existing nano-dispersed Ni-Cr-Si phase, form heterogeneous nucleation sites. During aging, nano-sized Ni2Si precipitates rapidly form, interacting with the existing complex second phase to achieve enhanced high-temperature stability and multi-scale strengthening. This approach addresses the structural instability and performance degradation associated with the dissolution of the dominant nickel-silicon precipitates in Cu-Ni-Si-Cr alloys at high temperatures. It also avoids the large equilibrium microstructure and poor performance (especially plasticity) of the copper matrix caused by the coarseness and agglomeration of Cr and its compounds. Through this dual microstructural control mechanism, the matrix grain size is significantly refined and multiple, uniformly distributed, high-stability nano-precipitates are formed, significantly improving the alloy's high-temperature stability and mechanical properties.

[0023] Furthermore, under deformation conditions of 0.5-2 hours, dislocations generated by cold working provide nucleation sites for recrystallization. When heated to 900-930°C, enhanced atomic migration promotes the nucleation and growth of new grains within the deformed matrix. Within this temperature range, the stability of the nanoscale Ni-Cr-Si phase is maintained, and its pinning effect effectively inhibits excessive grain growth. A holding time of 0.5-2 hours allows the recrystallization process to fully proceed to a state of grain boundary migration equilibrium, at which point the matrix forms a uniform, fine, equiaxed structure, while the precipitates exhibit no significant coarsening. The synergistic effect of these three factors allows the material to simultaneously achieve matrix refinement and precipitate stabilization during the recrystallization phase, providing an optimized microstructural foundation for subsequent aging treatment. This effectively addresses the technical issue of grain coarsening during thermomechanical treatment, achieving simultaneous matrix refinement and precipitate stabilization during the recrystallization phase. This provides uniformly dispersed heterogeneous nucleation sites and a stable phase interface structure for subsequent aging strengthening, ultimately resulting in a copper alloy with both high strength and high thermal stability.

[0024] Furthermore, by controlling the aging temperature to 450-550°C, building on the high-density dislocations generated by cold deformation, the nickel-silicon phase rapidly diffuses and migrates through channels such as defects, forming nanoscale nickel-silicon phases on existing nanoscale Ni-Cr-Si phases and dislocations. This helps improve the high-temperature stability of these newly formed nickel-silicon phases. A pre-deformation treatment with a deformation range of 0.2-0.4 provides uniformly distributed nucleation sites for the precipitates, while an aging treatment of 0.5-6 hours allows for the full precipitation of the precipitates. During this process, the combined action of dislocations and existing precipitates ensures a high degree of dispersion and high-temperature stability of the precipitates. This achieves the co-precipitation and structural stabilization of the nanoscale nickel-chromium-silicon complex phase and nickel-silicon phase, effectively improving the alloy's resistance to softening in high-temperature environments. At the same time, the synergistic effects of dislocation strengthening and multiple precipitation strengthening enhance the material's strength.

[0025] Furthermore, a combined deformation method of cold rolling, cold heading and cold forging is adopted in the recrystallization treatment stage, and a multi-dimensional stress field is formed through 3-4 step-by-step processing. After each processing, a dislocation structure with a specific orientation is generated inside the material. The alternating implementation of different processing methods can make the dislocations present a three-dimensional distribution feature. The problems of coarse grains and uneven distribution of precipitated phases caused by improper deformation process are solved. The staged deformation strategy not only ensures the dislocation density gradient required for recrystallization, but also maintains the stability of the primary nano-precipitated phase. The multi-dimensional stress field generated by the combined processing method promotes the spatial uniform distribution of Ni-Cr-Si phases, effectively suppresses the phase coarsening phenomenon under high temperature conditions, and enables the material to have the synergistic effects of fine grain strengthening and precipitation strengthening.

[0026] The present invention also discloses a high-strength and high-thermal stability copper alloy prepared by the above-mentioned preparation method. The high-precision control of the melting temperature enables the Cr element to be completely dissolved in the liquid phase, avoiding the premature precipitation, excessive coarsening and agglomeration of Cr and its compounds caused by insufficient temperature in traditional processes; rapid cooling forms a nanometer-level uniformly distributed Ni-Cr-Si metastable phase by inhibiting element diffusion, providing a basis for subsequent phase transformation; homogenization heat treatment promotes the migration of Cr elements to the metastable phase above the solid solution temperature, and staged deformation treatment refines the grains through recrystallization and pins dislocations using the precipitated phase, finally forming a microstructure strengthened by the stable Ni-Cr-Si metastable phase and a partially Cr-stabilized nanoscale Ni2Si phase after peak aging. While conventional Cu-Ni-Si-Cr alloys melt at temperatures below the melting point of Cr3Si, resulting in coarse and unevenly distributed precipitates after solidification, the present invention combines high-temperature melting with rapid cooling to form uniformly distributed nano-Ni-Cr-Si phases. While existing technologies employ a single annealing process, which can easily lead to microstructure coarsening, the present invention achieves a synergistic effect of precipitate stabilization and grain refinement through a staged deformation process, overcoming the technical drawback of microstructure instability at high temperatures. This eliminates the negative impact of premature formation, coarsening, and agglomeration of Cr3Si phases on material properties in conventional processes, resulting in a microstructure that combines nano-precipitate strengthening with high-temperature phase stability. This allows the alloy to maintain stable mechanical and electrical properties even at temperatures below 600°C (the maximum recommended aging temperature for CuNiSi alloys). BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic flow chart of the smelting preparation method of the high-strength and high-thermal stability copper alloy disclosed in the present invention; Figure 2 This is a diagram of the explosive welding composite interface disclosed in the present invention, where the local temperature exceeds the melting point of the material to form a teardrop-shaped melting zone; wherein (a) is the metallographic structure of the melting zone of the explosive welding interface; (b) is a partial enlarged view of the melting zone in (a); Figure 3 The metallographic images of the interface of the composite plate at different recrystallization times at 900°C disclosed in the present invention; (a) to (d) are 5, 15, 30, and 60 min, respectively; the arrows indicate the melting zone inherited from the welded state; Figure 4 The TEM photo of the interface melting zone after recrystallization at 900°C for 60 minutes and the corresponding EDS analysis diagram disclosed in the present invention; wherein, (a) is the TEM photo, (b) is the EDS analysis, (b-1) is the Ni element, (b-2) is the Si element, and (b-3) is the Cr element. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] In the present invention, unless otherwise specified, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

[0030] In the present invention, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0031] In the present invention, unless otherwise specified, percentages (%) or parts refer to percentages by weight or parts by weight relative to the composition.

[0032] In the present invention, unless otherwise specified, the components or preferred components involved can be combined with each other to form a new technical solution.

[0033] In this disclosure, unless otherwise specified, the numerical range "a-b" is an abbreviation for any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "6-22" indicates that all real numbers between "6-22" are listed herein, and "6-22" is merely an abbreviation for these numerical combinations.

[0034] The "range" disclosed in the present invention is in the form of lower limit and upper limit, which can be one or more lower limits, and one or more upper limits respectively.

[0035] In the present invention, the term "and / or" used herein refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0036] In the present invention, unless otherwise specified, each reaction or operation step can be carried out sequentially or in accordance with the sequence. Preferably, the reaction method herein is carried out sequentially.

[0037] Unless otherwise indicated, the professional and scientific terms used herein are the same as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content can also be applied to the present invention.

[0038] In traditional Cu-Ni-Si alloys, the dominant precipitate phase, Ni-Si, rapidly dissolves back under high-temperature conditions (above 600°C), leading to structural instability and performance degradation, making it difficult to meet the high demands on material properties. When existing technologies introduce Cr into Cu-Ni-Si alloys, due to the low solubility of Cr and its compounds in the Cu matrix, the Cr-Si phase is ultra-stable at high temperatures and easily grows and agglomerates. Conventional melting and casting methods are unable to fully utilize the Cr3Si phase's ability to stabilize and enhance high-temperature structural properties. Instead, the coarsening and agglomeration of the Cr3Si phase worsens the plasticity of the CuNiSi alloy, greatly limiting the alloy's applicable temperature range. While traditional high-temperature, long-term homogenization annealing processes can alleviate the problem of uneven structural composition in castings to a certain extent, they often result in overly coarse structural components and the inability of the high-melting-point, micron-sized Cr3Si phase to dissolve back, limiting the high-temperature structural and performance levels of the alloy.

[0039] In a first aspect, the present application proposes a smelting preparation method for a high-strength and high-thermal-stability copper alloy, comprising: High-purity (≥99.9%) Cu, Ni, Si, and Cr raw materials are selected and melted using vacuum induction melting or electron beam melting processes, and poured into a mold for casting or die-casting to obtain an initial copper alloy ingot. The content range is Ni: 2-3wt%, Cr: 0.3-0.6wt%. The total Si content in the material is calculated and added according to the specific Ni and Si contents, according to the Ni2Si and Cr3Si atomic ratios. performing homogenization heat treatment on the initial copper alloy ingot to obtain a homogenous alloy ingot; Water cooling quenching eliminates component segregation, and the uniform alloy ingot is subjected to thermomechanical treatment to obtain a high-performance copper alloy ingot.

[0040] The melting process is carried out using vacuum induction melting or electron beam melting, including: the melting temperature needs to be precisely controlled between 1800℃ and 2000℃ (i.e., between the melting point of Cr3Si, 1770℃, and the boiling point of Cu, 2562℃); the melting process needs to be repeated multiple times to ensure that all elements are melted into liquid phase and mixed evenly.

[0041] The initial copper alloy ingot is subjected to homogenization heat treatment, including: the homogenization heat treatment temperature is above the solid solution temperature of the copper alloy, about 900°C to 950°C, the time is 1-12 hours, and quenching is performed after the end.

[0042] The temperature of heat treatment was determined according to ASM Handbook Volume 4 Heat Treatment.

[0043] The homogenized alloy ingot is subjected to thermomechanical treatment, including deformation recrystallization treatment and deformation aging treatment.

[0044] The deformation method for deformation recrystallization and deformation aging treatment is cold deformation, including cold rolling, cold heading, and cold forging. The recrystallization deformation is 0.5-2, completed in 3-4 passes, at a recrystallization temperature of 900-930°C for 0.5-2 hours, followed by quenching. The aging deformation is 0.2-0.4, completed in 1-2 passes, at an aging temperature of 450-550°C for 0.5-6 hours. The recrystallization temperature matches the deformation, and the recrystallization temperature and recrystallization time are determined according to the ASM Handbook, Volume 4, Heat Treatment. The aging temperature and aging time are also determined according to the ASM Handbook, Volume 4, Heat Treatment.

[0045] In a second aspect, the present application proposes a high-strength and high-thermal stability copper alloy obtained by the above-mentioned preparation process.

[0046] The present invention discloses a high-strength and high-thermal stability copper alloy and a smelting preparation method thereof. The vacuum induction melting or electron beam melting process is used to precisely melt the raw materials to prepare alloy ingots. By precisely controlling the melting temperature (1800-2000°C), the Cr element is effectively prevented from forming a coarse primary phase and agglomerating during the melting process. Through rapid cooling molding and homogenization heat treatment (900~950℃), the dispersion precipitation and stabilization of nano-scale Ni-Cr-Si complex phases are promoted, effectively improving the high-temperature strength and organizational stability of the material. It can also act as a heterogeneous nucleating agent to induce the nucleation of a large number of nickel-silicon precipitates that play a dominant strengthening role, and provide high-temperature stability to these new phases through the interaction between elements and phase interfaces (inhibiting coarsening and dissolution), overcoming the problem of easy dissolution of the dominant strengthening phase under high-temperature environment in the existing technology; a multi-stage thermomechanical treatment process, including deformation recrystallization treatment and deformation aging treatment, is adopted to utilize the synergistic effect of multiple processing techniques to refine the matrix structure and form multiple high-stability dispersed precipitates, significantly improving the room temperature strength, plasticity and electrical conductivity of the material, and effectively solving the problem of material performance degradation under high-temperature environment in the existing technology; the smelting process parameters and heat treatment process parameters are optimized to ensure the uniformity of the material composition and avoid the defect of overly coarse organization in traditional methods, effectively improving the comprehensive performance of the material.

[0047] In order to make the purpose, 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 in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0048] Example 1 A smelting preparation method for a high-strength and high-thermal stability copper alloy, comprising: A Cu-2.5Ni-0.67Si-0.4Cr alloy was induction melted at 1900°C, spray-casted, and water-cooled. The alloy was homogenized at 930°C for 6 hours, water-quenched, and then 100% cold-deformed. Recrystallized at 920°C for 0.5 hours and water-quenched. The peak-aged alloy was then directly aged at 500°C for 3 hours.

[0049] Example 2 A smelting preparation method for a high-strength and high-thermal stability copper alloy, comprising: A Cu-2Ni-0.53Si-0.3Cr alloy was melted at 1800°C using vacuum induction melting, die-cast, and water-cooled. The alloy then underwent homogenization heat treatment at 900°C for 1 hour, followed by water quenching. The alloy was then cold-deformed to 50%, recrystallized at 900°C for 2 hours, and water-quenched. The peak-aged alloy was then directly aged at 450°C for 6 hours.

[0050] Example 3 A smelting preparation method for a high-strength and high-thermal stability copper alloy, comprising: A Cu-3Ni-0.83Si-0.6Cr alloy was melted at 2000°C using vacuum induction melting, die-cast, and water-cooled. The alloy was homogenized at 950°C for 12 hours, water-quenched, and then cold-deformed for 2 seconds. The alloy was recrystallized at 930°C for 1 hour and water-quenched. The alloy was then cold-rolled 40% and aged directly at 550°C for 0.5 hours to obtain the peak-aged alloy.

[0051] Example 4 A smelting preparation method for a high-strength and high-thermal stability copper alloy, comprising: A Cu-3Ni-0.83Si-0.6Cr alloy was melted at 2000°C using electron beam melting, spray-casted, and water-cooled. The alloy was homogenized at 950°C for 10 hours, water-quenched, and then cold-deformed for 2 seconds. Recrystallized at 930°C for 2 hours, and water-quenched. It was cold-rolled 30% and then aged at 530°C for 1.5 hours to obtain the peak-aged alloy.

[0052] Figure 1 The present invention discloses a method for preparing a high-strength and high-thermal-stability copper alloy by smelting. The method comprises the following steps: using high-purity Cu, Ni, Si, and Cr as raw materials, forming a uniform liquid phase through vacuum induction or electron beam melting (1800-2000°C) to ensure that the alloy elements are fully melted and evenly mixed; then forming the liquid phase by spray casting or die casting, and performing a homogenizing heat treatment to form a dispersed nano-scale ultra-stable complex Ni-Cr-Si phase, thereby laying a foundation for a uniform structure for subsequent cold deformation and heat treatment; and then regulating the performance through two thermomechanical treatment paths. Path one is cold deformation (0.5-2h), followed by recrystallization at 900-930°C (0.5-2h), and using the nano-scale Ni-Cr-Si phase to pin the crystals. The first path refines the grain size while improving the alloy's thermal stability. The second path involves cold deformation (0.2-0.4°C) followed by aging at 450-550°C (0.5-6h). Leveraging crystal defects introduced by cold deformation and nucleation sites provided by the Ni-Cr-Si phase, a strengthening phase dominated by Ni2Si precipitates within the microstructure. This phase, through elemental and interfacial interactions with the complex Ni-Cr-Si phase, achieves high-temperature stability exceeding that of conventional precipitates, significantly improving the alloy's high-temperature strength and electrical conductivity, while also exhibiting superior plasticity compared to conventional alloys aggregated with Cr3Si. This dual-path design, combined with optimized parameter matching, precisely achieves the synergistic performance of "high strength and high thermal stability."

[0053] Figure 2 This is the explosive welding composite interface disclosed in the present invention, where the local temperature exceeds the melting point of the material to form a teardrop-shaped melting zone; (a) is the metallographic structure of the melting zone of the explosive welding interface; (b) is a partial enlarged view of the melting zone in (a); the present invention uses explosive welding technology to weld two CuNiSiCr alloy plates with the same microstructure to form a composite plate. During this process, a transient high temperature and high pressure environment is generated in the local area of ​​the welding interface, with a temperature of about 2000°C (within the melting temperature range of the present invention), causing part of the metal to melt and form a teardrop-shaped area ( Figure 2 , indicated by the blue arrow).

[0054] Figure 3The metallographic images of the interface of the composite plate at different recrystallization times at 900°C disclosed in the present invention; (a) to (d) are 5, 15, 30, and 60 minutes, respectively; the arrows indicate the melting zone inherited from the welded state; the composite plate was cold deformed by 60% and recrystallized at 900°C. The weld interface microstructures at different recrystallization times are as follows Figure 3 As shown, it can be seen that the original melting zone indicated by the blue arrow has a much smaller structure than other areas, showing extremely high high-temperature stability.

[0055] Figure 4 The TEM photo of the interface melting zone after 60 minutes of recrystallization at 900 ° C disclosed in the present invention and the corresponding EDS analysis diagram; wherein, (a) is a TEM photo, (b) is an EDS analysis, (b-1) is Ni element, (b-2) is Si element, and (b-3) is Cr element; the interface melting zone of the composite plate after 60 minutes of recrystallization at 900 ° C is further observed under TEM. Figure 4 As shown, a large number of nano-sized particles were found.

[0056] Table 1 is Figure 4 b Element composition of the EDS point scanning position; the EDS analysis results of the corresponding points are listed in Table 1. These particles are mainly metastable Ni 31 Si 12 The above results indicate that the high temperature of 2000℃ generated by explosive welding melts the Cr3Si in the CuNiSiCr alloy and regenerates Ni 31 Si 12 During the subsequent evolution process, the Cr element is gradually absorbed, and the size can continue to remain at the nanometer level. This can significantly refine the material structure, improve the material strength, and provide the corresponding high-temperature structure and performance stability and level. Inspired by the above process, as long as the Cr3Si phase is melted, cast and rapidly cooled above the melting point, an environment equivalent to the explosive welding melting zone can be achieved, thereby forming a nanoscale Ni-Cr-Si complex phase and improving the structure and performance of CuNiSiCr alloys (especially under high temperature conditions).

[0057] Table 1 Figure 4 b Elemental composition of EDS point scanning position

[0058] In summary, the present invention discloses a high-strength and high-thermal-stability copper alloy and its smelting preparation method. Due to the low solubility of Cr in the Cu matrix and the excessive thermal stability of the Cr3Si phase, Cr and its compounds will precipitate and coarsen prematurely during the smelting process of the Cu-Ni-Si-Cr alloy, which can neither provide a strengthening effect nor stabilize the structure, resulting in poor high-temperature structural stability and low performance of such alloys. A smelting and heat treatment method for a Cu-Ni-Si-Cr alloy that can achieve stable and strengthened nanoscale complex Ni-Cr-Si phases is provided. Induction melting or electron beam melting technology is used to precisely control the working temperature range, so that the alloy melting temperature is between the melting point of Cr3Si (about 1770°C) and the boiling point of Cu (about 2562°C), ensuring that all elements remain in a liquid state and are fully mixed. The alloy is then rapidly cooled to obtain an alloy ingot with uniform composition and a large distribution of nanoscale Ni-Cr-Si phases. The material has good room temperature and high-temperature structural stability and high strength.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for smelting and preparing a high-strength and high-thermal stability copper alloy, characterized in that: include: High-purity Cu, high-purity Ni, high-purity Si and high-purity Cr are used as raw materials, smelted until the raw materials are melted into a liquid phase and mixed evenly, then spray-casted or die-cast and water-cooled to obtain a copper alloy ingot; after homogenization heat treatment, water-cooling quenching and thermo-mechanical treatment, a high-strength and high-thermal-stability copper alloy is obtained; the purity of the raw materials is 99.9%; the smelting temperature is 1800-2000°C.

2. The method for preparing a high-strength and high-thermal-stability copper alloy by smelting according to claim 1, characterized in that: The raw materials include, by mass percentage, 2-3 wt% Ni and 0.3-0.6 wt% Cr. The total Si mass in the raw materials is obtained by converting and adding the specific Ni and Cr masses according to the atomic ratio of Ni2Si and Cr3Si.

3. The method for smelting and preparing a high-strength and high-thermal-stability copper alloy according to claim 1, characterized in that: The melting method includes vacuum induction melting or electron beam melting.

4. The method for smelting and preparing a high-strength and high-thermal-stability copper alloy according to claim 1, characterized in that: The conditions for the uniform heat treatment include: heat treatment at 900-950° C. for 1-12 hours.

5. The method for smelting and preparing a high-strength and high-thermal-stability copper alloy according to claim 1, characterized in that: The conditions of the thermomechanical treatment include: deformation recrystallization treatment and deformation aging treatment.

6. The method for smelting and preparing a high-strength and high-thermal-stability copper alloy according to claim 5, characterized in that: The conditions of the deformation recrystallization treatment include: a deformation amount of 0.5-2; a crystallization temperature of 900-930° C.; and a crystallization time of 0.5-2 h.

7. The method for smelting and preparing a high-strength and high-thermal-stability copper alloy according to claim 5, characterized in that: The deformation recrystallization treatment is carried out by cold rolling, cold heading and cold forging in 3-4 steps.

8. The method for smelting and preparing a high-strength and high-thermal-stability copper alloy according to claim 5, characterized in that: The conditions of the deformation aging treatment include: a deformation amount of 0.2-0.4; an aging temperature of 450-550° C.; and an aging time of 0.5-6 hours.

9. The method for smelting and preparing a high-strength and high-thermal-stability copper alloy according to claim 5, characterized in that: The deformation aging treatment is carried out by cold rolling, cold heading and cold forging in 1-2 steps.

10. A high-strength and high-thermal-stability copper alloy, characterized in that: The high-strength and high-thermal-stability copper alloy is prepared by the smelting preparation method according to any one of claims 1 to 9.

Images