Copper metal complex and preparation method

Abstract

The invention discloses a copper metal complex and a preparation method thereof. The copper metal complex is prepared by mixing copper powder and refractory metal powder, adding a dispersing agent and graphite and carrying out compression and vacuum sintering. The outer layer of the complex structure is copper foil, the inner layer is uniform alloy powder, the complex structure can be used as intermediate alloy for subsequent smelting, the smelting temperature is remarkably reduced, element oxidation is inhibited, and the component uniformity is improved; the method is suitable for preparing the copper-based complexes of various high-melting-point and easily-oxidized elements.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metallurgy, in particular to a copper metal composite and a preparation method thereof. BACKGROUND

[0002] Copper alloy has become a core material supporting the development of high-end equipment, electronic information, aerospace and new energy industries due to its excellent comprehensive performance such as high strength, high electrical conductivity and thermal conductivity, and fatigue resistance. By reasonably controlling the composition and optimizing the preparation process, its application scenarios in extreme working conditions can be further expanded to meet the stringent requirements of high-end fields on material performance.

[0003] However, the traditional preparation process has problems such as high melting temperature, serious element segregation, difficult-to-control oxidation, and low production efficiency. Meanwhile, in the prior art, when directly melting high-melting-point elements (such as chromium, zirconium, beryllium, etc.) and copper to prepare intermediate alloy, the energy consumption is large, the element volatilization is serious, and the composition is not uniform during the solidification process, which affects the performance of the final product.

[0004] To solve the above problems, there is an urgent need in the field for a new intermediate alloy preparation method to reduce the melting difficulty and improve the composition uniformity and production efficiency. SUMMARY

[0005] To solve the problem of preparing high-melting-point and easily-oxidized elements with copper in the prior art, the present application provides a copper metal composite and a preparation method thereof. By combining powder metallurgy and vacuum sintering technology, and using specific dispersants and reducing agents, the element is uniformly distributed, the melting temperature is reduced, and the oxidation reaction is inhibited.

[0006] To achieve the above purpose, the present application provides a metal composite in a first aspect, comprising:

[0007] The outer layer of copper foil and the inner layer of powder mixture are tightly wrapped by the outer layer of copper foil;

[0008] The inner layer of powder mixture is composed of copper powder, refractory metal or easily-oxidized metal powder, dispersant and graphite;

[0009] The refractory metal or easily-oxidized metal powder is one or a combination of zirconium, beryllium, boron, magnesium, silicon, calcium, lithium, iron, manganese, phosphorus, titanium, tungsten, molybdenum, chromium, niobium;

[0010] The dispersant is one or a combination of alcohol, water-based dispersant, non-ionic surfactant or solid organic dispersant;

[0011] The addition amount of graphite is 0.1% to 5% of the total mass of the powder mixture.

[0012] The beneficial effects of the present application are: through the structural design of "outer copper foil wrapping + inner layer powder synergistic matching", combined with the combination of dispersant and graphite, the technical pain points of serious oxidation, composition segregation and high smelting temperature of traditional high melting point and easily oxidized metals during copper compounding are solved; the composite can be directly used as an intermediate alloy for subsequent copper alloy smelting, without additional pretreatment, significantly simplifying the process and reducing energy consumption; at the same time, it is suitable for various refractory / easily oxidized metals, and has strong universality, and can stably improve the composition uniformity and mechanical / electrical / thermal conductivity of the final copper alloy product.

[0013] In the optional embodiment according to the first aspect, the thickness of the outer copper foil is 0.1-2mm, and the outer copper foil is a high-purity copper foil.

[0014] The further technical solution can effectively: control the structural strength and protection performance of the copper foil, avoid damage, impurity introduction during subsequent sintering or smelting, or resource waste and smelting efficiency reduction caused by excessive thickness; the high-purity characteristic further reduces impurity pollution, ensures the purity of the inner layer powder, and the copper foil can be well integrated with the inner layer powder and the subsequent smelting system, avoiding the influence of interface reaction on product performance.

[0015] In the optional embodiment according to the first aspect, the particle size of the copper powder is 1-1000μm, and the particle size of the refractory metal or easily oxidized metal powder is 10-500μm.

[0016] The further technical solution can effectively: realize the close packing and uniform mixing of the two kinds of metal powders, avoid the risk of increased oxidation and increased mixing difficulty caused by excessive particle size difference, and ensure the formation of good combination between powders during sintering, improve the density and structural stability of the composite, and lay a foundation for rapid dissolution during subsequent smelting.

[0017] In the optional embodiment according to the first aspect, the alcohol dispersant is ethanol or isopropyl alcohol;

[0018] The water-based dispersant is sodium polyacrylate or sodium hexametaphosphate;

[0019] The non-ionic surfactant is polyethylene glycol or Tween 80;

[0020] The solid organic dispersant is zinc stearate or polyvinyl alcohol.

[0021] The further technical solution can effectively: select a suitable dispersant for the characteristics of the metal powder, solve the powder agglomeration problem in different systems - alcohol, water-based dispersant for wet mixing, solid organic dispersant for dry mixing, ensure uniform dispersion of the inner layer powder under different process conditions, and provide protection for the composition uniformity and performance stability of the composite.

[0022] In an optional embodiment according to the first aspect, in the inner layer powder mixture, the mass percentage of copper powder is 50% to 95%, the mass percentage of refractory metal or oxidizable metal powder is 5% to 50%, and the mass percentage of dispersant is 0.05% to 3%.

[0023] The further technical solution can effectively: by controlling the proportion of each component, ensure that the refractory / oxidizable metal powder is uniformly distributed in the copper-based system, both meet the performance requirements (such as strength, electrical conductivity) of the subsequent alloy, and avoid mixing unevenly, sintering difficulty caused by too high alloy powder ratio, or too low ratio to achieve the expected alloying effect; the trace amount of dispersant is designed to ensure the dispersion effect while avoiding excessive residues affecting the purity and sintering quality of the composite.

[0024] The second aspect of the present application also provides a preparation method, which is applied to the preparation of the above-mentioned metal composite, comprising the following steps:

[0025] S1: weigh the copper powder, refractory metal or oxidizable metal powder, dispersant and graphite according to the proportion;

[0026] S2: uniformly mix the above-mentioned components by wet ball milling or dry mechanical mixing method to obtain an inner layer powder mixture;

[0027] S3: place the inner layer powder mixture in the outer copper foil and press it into a predetermined shape;

[0028] S4: sintering under vacuum or inert atmosphere, sintering temperature is 600-1100℃, holding time is 1-48 hours;

[0029] S5: cool to room temperature to obtain a metal composite.

[0030] The present application has the following advantages: the process combining powder metallurgy and vacuum / inert atmosphere sintering avoids the problems of high energy consumption, serious element volatilization and segregation, and easy oxidation caused by traditional high-temperature smelting; through the wet / dry mixing method, combined with precise pressing and sintering parameter control, the inner layer powder is uniformly dispersed and the composite has high density; the process steps are simple and controllable, no complex equipment is needed, batch production is possible, and it can be adapted to the compounding of various refractory / oxidizable metals and copper, significantly improving production efficiency and product stability, and reducing industrial application cost.

[0031] In an optional embodiment according to the second aspect, in step S2, when wet ball milling, add ethanol as a solvent and add 0.1-2wt% of sodium polyacrylate; when dry mechanical mixing, add zinc stearate and graphite, the mixing speed is 20-50rpm, and the mixing time is 10-60 minutes.

[0032] Adopting the further technical scheme can effectively: for different mixing process, adapt to special dispersing system - in wet method, ethanol as solvent reduces the resistance of powder agglomeration, sodium polyacrylate enhances the dispersion stability; in dry method, zinc stearate and graphite play a synergistic role in dispersion and lubrication, combined with accurate rotation speed and time parameters, to ensure that the powder can realize deep and uniform mixing in solvent-free or solvent system, avoid local component enrichment, lay a foundation for subsequent sintering and uniformity of composite performance.

[0033] In the optional embodiment according to the second aspect, in step S3, the pressing pressure of the press forming is 10-6000 Mpa, the pressure holding time is 5-300 s, and the preset shape is a cylinder, a cuboid or a special-shaped structure.

[0034] Adopting the further technical scheme can effectively: through the synergistic control of pressure and pressure holding time, the inner layer powder forms a dense blank in the copper foil, avoiding high porosity of the blank due to insufficient pressure and short pressure holding time, or copper foil damage caused by excessive pressure and long pressure holding time; diversified preset shape design can adapt to the feeding requirements of different subsequent melting scenes, improve the practicality and adaptability of the product, and no additional processing is needed.

[0035] In the optional embodiment according to the second aspect, in step S4, the vacuum degree is ≤1 Pa, and the inert atmosphere is argon or nitrogen; the sintering adopts a segmented heating mode, and the heating rate is 5-15 ℃ / min, and the temperature is kept after rising to the sintering temperature.

[0036] Adopting the further technical scheme can effectively: high vacuum degree or inert atmosphere can maximize the isolation of oxygen and inhibit the oxidation reaction of refractory / easy-oxidizing metal powder, ensuring product purity; segmented heating and precise heating rate control can avoid copper foil and inner layer powder thermal expansion inconsistency, blank cracking caused by excessive heating, or element volatilization caused by local high temperature; combined with the preset sintering temperature and holding time, it can promote the diffusion and combination between the powders, improve the structural strength and density of the composite, and ensure its subsequent rapid dissolution performance as an intermediate alloy. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a structure diagram of the outer layer copper foil and the inner layer powder mixture in the metal composite of the application;

[0038] Figure 2 is a sectional view of the internal structure of the outer layer copper foil in the metal composite of the application;

[0039] Figure 3 is a step flow chart of the metal composite preparation method of the application.

[0040] In the figure, the correspondence between the component names and the reference signs is as follows:

[0041] 1 - outer layer copper foil; 2 - inner layer powder mixture; 11 - groove. DETAILED DESCRIPTION

[0042] The embodiments of the present application will be further described in details below with reference to the accompanying drawings and examples. The following examples are used to illustrate the technical solutions of the present application, but cannot be used to limit the protection scope of the present application.

[0043] Referring to Figure 1 , 2 As shown in the figure, the present application provides a metal composite, which comprises an outer layer copper foil 11 and an inner layer powder mixture 2, and the outer layer copper foil 11 wraps the inner layer powder mixture 2 so that the inner layer powder mixture 2 is in a closed space.

[0044] The outer layer copper foil 11 has the following functions: isolating the inner layer powder mixture 2 from the external air to reduce the oxidation of the inner layer powder during storage and subsequent processing; serving as a structural carrier of the metal composite to provide support for the inner layer powder mixture 2, facilitating subsequent forming, sintering and feeding operations; and being quickly melted during subsequent copper alloy smelting, fusing with the inner layer powder mixture 2 and the smelting system to avoid splashing and loss when the inner layer powder is directly fed.

[0045] The inner layer powder mixture 2 is composed of copper powder, refractory metal or oxidizable metal powder, dispersant and graphite, and each component is mixed uniformly according to a set proportion.

[0046] The copper powder has the following functions: serving as a base component of the inner layer powder mixture 2 to provide a dispersion carrier for the refractory metal or oxidizable metal powder, ensuring that each alloying element can be uniformly distributed in the copper-based system during subsequent smelting; and being consistent with the material of the outer layer copper foil 11 to improve the compatibility of the overall metal composite and form a continuous copper phase structure during sintering and smelting.

[0047] The refractory metal or oxidizable metal powder is one or a combination of multiple of zirconium, beryllium, boron, magnesium, silicon, calcium, lithium, iron, manganese, phosphorus, titanium, tungsten, molybdenum, chromium, niobium.

[0048] The refractory metal or oxidizable metal powder has the following functions: serving as a functional alloying element, which can form a solid solution or intermetallic compound with the copper matrix during subsequent copper alloy smelting, thereby regulating the core indicators such as mechanical properties, electrical and thermal conductivity, corrosion resistance of the copper alloy; and different types of metal powder can be selected according to the performance requirements of the target copper alloy, for example, zirconium and titanium can refine the copper alloy grain and improve the strength; silicon and phosphorus can purify the copper alloy melt and remove impurities; chromium can improve the strength and hardness of the copper alloy, while reducing the electrical conductivity of the alloy.

[0049] The dispersant is one or a combination of alcohol, water-based dispersant, non-ionic surfactant or solid organic dispersant.

[0050] The dispersant reduces the agglomeration force between the copper powder and the refractory metal or oxidizable metal powder, realizes uniform dispersion of the two powders during mixing, and avoids local composition enrichment or segregation.

[0051] The graphite is added in an amount of 0.1% to 5% of the total mass of the powder mixture 2.

[0052] The graphite forms a lubricating layer on the surface of the powder particles during pressing and sintering, reduces the frictional resistance between the particles, and promotes the densification of the powder. The graphite has reducing properties and can reduce the oxide film on the surface of the powder in a high-temperature environment, reducing the generation of oxidized impurities. In the subsequent melting process, the graphite can act as a carbon source to control the carbon content of the copper alloy or form carbides with some metal elements to further optimize the performance of the copper alloy.

[0053] Referring to Figure 2 As shown in the figure, a plurality of grooves 11 are formed on the inner surface of the outer copper foil 11 based on the above-mentioned metal composite, the depth of the grooves 11 is 1 / 3 to 2 / 3 of the thickness of the outer copper foil 11, and the distribution density of the grooves 11 is 1 to 10 per square centimeter.

[0054] Through the setting of technical point one, the grooves 11 can effectively increase the contact area between the outer copper foil 11 and the inner powder mixture 2, improve the bonding strength of the two in the sintering process, and avoid the separation of the inner powder and the outer copper foil 1 during subsequent handling or feeding. At the same time, the grooves 11 can act as a positioning structure for the powder, reducing the flow deviation of the mixed powder during forming and maintaining the uniformity of the internal composition of the composite.

[0055] The metal composite of the present application can effectively solve the problems of oxidation of the inner functional powder, large feeding loss, uneven alloy composition, etc.

[0056] For example, in the preparation of high-strength high-conductivity copper alloy, the metal composite is used, the suitable refractory metal powder is selected as the functional component, and after the preset process treatment, it is put into the melting system, and the final copper alloy has effectively improved tensile strength, high conductivity, and lower powder feeding loss rate than traditional process.

[0057] In the prior art, copper alloy is prepared by directly feeding mixed powder into a melting furnace, which not only easily causes severe oxidation of the powder at high temperature, resulting in failure of the functional elements, but also produces a large amount of loss due to powder splashing; at the same time, direct feeding cannot guarantee uniform dispersion of the functional powder in the copper base, which easily causes composition segregation, resulting in large fluctuations in alloy performance, and additional antioxidants and stirring equipment are needed, increasing production procedures and costs.

[0058] The present application avoids powder oxidation and splashing loss from the source through the sealing protection and structural support of the outer copper foil 1, and realizes uniform dispersion of functional elements by combining the reasonable component design of the inner layer, without the need for additional antioxidants and complex stirring devices, thereby simplifying the production process and reducing the cost; compared with the prior art, the present application can better control the composition and performance of copper alloy, improve the consistency and stability of the product, and is suitable for different performance requirements of copper alloy preparation scenes, especially in the field of high-end precision copper alloy.

[0059] Further optimization at technical point one: filling metal filler in the groove 11, the melting point of the metal filler is lower than the melting point of the outer copper foil 11, and higher than the sintering temperature (600-1100℃) set by the present application, forming technical point two through the above technical design.

[0060] The separate effect of technical point two: when only technical point two is used without technical point one (i.e. no groove 11 on the inner surface of the outer copper foil 1, and the metal filler is directly laid), the metal filler can partially melt during the sintering process, filling the gap between the outer copper foil 11 and the inner powder mixture 2, and improving the interfacial bonding strength of the two; during the subsequent melting process, the metal filler can reduce the melting temperature of the inner powder mixture 2, promoting the rapid dissolution of the powder in the copper alloy melt.

[0061] When technical point one and technical point two are used at the same time, they can produce different effects of synergistic effect, specifically: the groove 11 is filled with metal filler, the metal filler is in full contact with the inner wall of the groove 11 and the inner powder mixture 2, forming technical point three.

[0062] Synergistic effect of technical point three: the groove 11 can play a positioning role on the metal filler, avoiding the aggregation of the filler during the sintering process; at the same time, the groove 11 increases the contact area between the filler and the inner layer powder, so that the filler can more uniformly penetrate into the powder gap, further improving the bonding strength between the outer layer copper foil 1 and the inner layer powder; during subsequent melting, the filler can quickly diffuse along the channel formed by the groove 11, driving the inner layer powder to melt synchronously, significantly shortening the melting time and improving the melting efficiency.

[0063] Compared with the use of technical point one and technical point two alone, technical point three can improve the structural stability and melting efficiency of the metal composite, forming a 1+1>2 technical effect.

[0064] The addition amount of graphite is 0.1% to 5% of the total mass of the inner layer powder mixture 2. This addition amount range is not arbitrarily set, but is derived based on the multiple roles of graphite in the metal composite: when the addition amount is less than 0.1%, it is difficult for graphite to form a continuous lubricating layer on the surface of the powder particles, and the frictional resistance between the particles during pressing cannot be effectively reduced, resulting in poor powder densification effect;

[0065] At the same time, a small amount of graphite has limited reducing ability and is difficult to fully reduce the oxide film on the surface of the powder, increasing the residual amount of oxidized impurities. When the addition amount is higher than 5%, excessive graphite cannot be completely reacted during subsequent melting, and a large amount of carbon elements remain in the copper alloy, which can damage the electrical conductivity of the copper alloy and cause a significant decrease in electrical conductivity;

[0066] In addition, excessive graphite may form excessive carbides with some metal elements, increasing the brittleness of the copper alloy. The range of 0.1% to 5% can balance the functions of graphite such as lubrication, reduction, and carbon source regulation, ensuring that it can fully play its auxiliary role without affecting the core performance of the copper alloy. As one of the components of the inner layer powder mixture 2, graphite works synergistically with other components to ensure the performance of the composite.

[0067] In the embodiment, the thickness of the outer layer copper foil 11 is 0.1 to 2 mm, and the outer layer copper foil 11 is a high-purity copper foil. The thickness needs to be set to balance the protection effect and melting adaptability: when the thickness is less than 0.1 mm, the structural strength of the copper foil is insufficient, and it is easy to break during storage, transportation, and forming, resulting in the scattering of the inner layer powder mixture 2;

[0068] When the thickness is greater than 2 mm, the melting time of the copper foil will be significantly prolonged, and it will be difficult to quickly fuse with the inner layer powder and other components in the melting system, which may cause local overheating or uneven composition. In addition, the excessive thickness of the copper foil will increase the cost of raw materials, and the excessive amount of copper may change the preset composition ratio of the target copper alloy.

[0069] The high-purity copper foil has a copper element mass fraction of 99.9% or more, and a mass fraction of a single impurity element (such as iron, lead, tin, sulfur, phosphorus, etc.) of 0.05% or less, and a total impurity content of 0.1% or less. The above purity indexes can be confirmed by inductively coupled plasma mass spectrometry (ICP-MS) or atomic absorption spectrometry (AAS) detection. High-purity copper foil is used because copper foil with low impurity content does not introduce additional impurities into the smelting system, avoiding affecting the purity and performance of the copper alloy. At the same time, the melting characteristics of high-purity copper foil are more stable, ensuring uniform melting at a set temperature and forming a continuous copper phase structure with the inner layer copper powder and other components, ensuring the overall compatibility of the metal composite.

[0070] At the same time, the particle size of the copper powder is 1-1000 μm, and the particle size of the refractory metal or easily oxidizable metal powder is 10-500 μm. The particle size of the copper powder needs to be set to adapt to its substrate carrier function: when the particle size is less than 1 μm, the agglomeration force between copper powder particles is strong, and it is difficult to achieve uniform dispersion even with the addition of a dispersant, and agglomerates are easily formed; when the particle size is greater than 1000 μm, the specific surface area of the copper powder is too small, and the contact area with the refractory metal or easily oxidizable metal powder is insufficient, which cannot provide sufficient dispersion sites for the functional powder, resulting in uneven distribution of the functional powder. The particle size range of 1-1000 μm can ensure that the copper powder has a certain specific surface area and dispersibility, and can avoid the agglomeration problem caused by too small particle size, ensuring its carrying effect as a substrate component.

[0071] The particle size of the refractory metal or easily oxidizable metal powder needs to be set in combination with its function and dispersion requirements: when the particle size is less than 10 μm, the activity of such powder is very high, and oxidation is easy to occur during mixing and storage, and there is also a risk of agglomeration; when the particle size is greater than 500 μm, the sintering temperature of the powder and the copper powder is greatly increased, and the sintering density and strength are low, and at the same time the dissolution speed is reduced when used for smelting, and it is difficult to completely fuse with the copper matrix during the smelting process, and it is easy to form unsolved particles, affecting the mechanical properties and uniformity of the copper alloy. The particle size range of 10-500 μm can balance the oxidation stability and smelting dissolution efficiency, and at the same time form an adaptation with the particle size of the copper powder, ensuring that the two powders can be uniformly distributed after mixing, avoiding local component enrichment.

[0072] The alcohol dispersant is ethanol or isopropyl alcohol, and such dispersant is suitable for wet mixing process, and the core advantage lies in strong solubility and good volatility.

[0073] Ethanol or isopropanol can quickly penetrate into the interstitial space between copper powder and refractory metal or easily oxidizable metal powder, reduce the van der Waals force between particles, destroy the agglomerate structure, and make the two powders uniformly dispersed in the dispersion medium; at the same time, its boiling point is relatively low, and it can quickly volatilize in the subsequent drying process, so as to avoid introducing additional impurities. Compared with other alcohols, ethanol and isopropanol have low toxicity, high safety and controllable cost, and are more suitable for industrial production scenes, which can meet the core needs of wet mixing of dispersants.

[0074] The water-based dispersant is sodium polyacrylate or sodium hexametaphosphate;

[0075] Specifically, as a water-soluble dispersant, such substances are suitable for wet mixing processes sensitive to organic solvents, and the mechanism of action is that the ions produced by dissociation are adsorbed on the surface of the powder particles, so that the particles have the same charge, and the charge repulsion prevents particle agglomeration. The dispersion effect of sodium polyacrylate and sodium hexametaphosphate is stable, can work in a wide pH range, and has no chemical reaction with copper powder, refractory metal or easily oxidizable metal powder, and will not change the chemical properties of the powder; at the same time, the residue of such dispersants can be easily removed by water washing, or decomposed and volatilized in the high-temperature sintering process, which will not have a negative impact on the performance of the subsequent copper alloy, and is suitable for production processes with high environmental requirements.

[0076] The non-ionic surfactant is polyethylene glycol or Tween 80;

[0077] Specifically, the advantage of such dispersants is wide applicability, which can be used in wet mixing and also in some semi-dry mixing processes. The molecular structure contains both hydrophilic and hydrophobic groups, which can form an adsorption layer on the surface of the powder particles through adsorption, reduce the interfacial tension between particles, and destroy the agglomerates; and the non-ionic surfactant is not affected by the ionic strength of the system like ionic dispersants, and has stronger dispersion stability. Polyethylene glycol and Tween 80 have stable chemical properties and no adverse reactions with various powder components, and can be decomposed into harmless substances at high temperatures, which will not be left in the copper alloy, and can meet the needs of various mixing process scenes.

[0078] The solid organic dispersant is zinc stearate or polyvinyl alcohol;

[0079] Specifically, this kind of dispersant is specially adapted to the dry mixing process, which acts by uniformly adhering to the surface of copper powder and refractory metal or easily oxidizable metal powder through mechanical force during powder mixing, forming a lubricating layer to reduce the frictional resistance and agglomeration force between particles. The melting point of zinc stearate and polyvinyl alcohol is relatively low, and it will melt before the powder particles in the subsequent sintering process, further playing a lubricating role and promoting powder densification; at the same time, this kind of dispersant will completely decompose and volatilize during high-temperature smelting, and will not introduce impurities into the copper alloy. Compared with liquid dispersants, solid organic dispersants do not require a subsequent drying step, which can simplify the process of dry mixing process and improve production efficiency.

[0080] In the inner layer powder mixture 2, the mass percentage of copper powder is 50% to 95%, the mass percentage of refractory metal or easily oxidizable metal powder is 5% to 50%, and the mass percentage of dispersant is 0.05% to 3%.

[0081] The mass percentage of copper powder is set based on its matrix core position: when the percentage is less than 50%, the content of copper powder is insufficient to form a continuous matrix structure, which cannot provide sufficient dispersion carrier for refractory metal or easily oxidizable metal powder, resulting in discontinuous copper phase in the alloy;

[0082] When the percentage is higher than 95%, the content of refractory metal or easily oxidizable metal powder is too low, and its role in regulating the performance of copper alloy cannot be fully played, making it difficult to achieve the performance indicators of the target alloy.

[0083] The percentage range of 50% to 95% can ensure the dominant role of copper powder as the matrix, while reserving sufficient content space for functional powder 4.

[0084] The percentage of refractory metal or easily oxidizable metal powder needs to be combined with its functional strength: when the percentage is less than 5%, the content of functional elements is insufficient to form sufficient solid solution or intermetallic compound with the copper matrix, which cannot effectively regulate the alloy performance;

[0085] When the percentage is higher than 50%, the content of such powder is too high, which may cause a significant decrease in the electrical and thermal conductivity of the alloy, making it difficult to sinter in solid-liquid phase, and easily forming excessive intermetallic compounds, increasing the brittleness of the alloy and making it difficult to form. The percentage range of 5% to 50% can be adjusted according to the performance requirements of the target copper alloy to ensure that the functional elements fully play their role.

[0086] The percentage of dispersant needs to balance the dispersion effect and residual risk: when the percentage is less than 0.05%, the amount of dispersant is insufficient to effectively reduce the agglomeration force between powder particles, and the dispersion effect is not good;

[0087] When the proportion is higher than 3%, excessive dispersant is difficult to be completely removed in subsequent processing, and residual dispersant will decompose to produce gas or impurities at high temperature, thereby affecting the sintering densification of the powder and the performance of the copper alloy.

[0088] In the proportion range of 0.05% to 3%, the negative influence caused by the residual dispersant can be minimized on the premise of ensuring the dispersing effect.

[0089] Referring to Figure 3 The preparation method provided by the present application is applied to the preparation of the metal composite, and through step-by-step control of process parameters and operation details, the product performance is ensured to be stable, and the specific steps are as follows:

[0090] Step S1: weighing of raw materials;

[0091] The copper powder, refractory metal or oxidizable metal powder, dispersant and graphite are weighed according to the preset proportion, wherein the refractory metal or oxidizable metal powder is selected in a "graded particle size proportioning" manner, that is, the metal powder is divided into a fine particle size section (10-50 μm), a medium particle size section (50-200 μm) and a coarse particle size section (200-500 μm), and the mass proportions of the three particle size powders are (30-40%): (40-50%): (20-30%).

[0092] This step is the basis for subsequent mixing and forming, and the accuracy of the raw material proportion directly affects the uniformity of the composition of the inner layer powder mixture 2, and further determines the alloying effect of the metal composite and the final use performance. The design of the graded particle size proportioning can make the refractory metal or oxidizable metal powder form a "close-packed structure" in the copper powder matrix, the fine particle size powder can fill the gaps between the medium and coarse particle size powders, and the porosity inside the powder mixture is reduced, thereby creating more favorable contact conditions for atomic diffusion between particles in the subsequent pressing and sintering processes.

[0093] The proportioning of different raw materials needs to be adjusted according to the composition requirements of the target copper alloy to ensure that the refractory metal or oxidizable metal powder can achieve the expected alloying proportion in the copper matrix, and the amount of dispersant and graphite needs to match the powder mixing demand and the oxidation resistance demand. At the same time, the proportion of the graded particle size can be adjusted according to the characteristics of the specific metal powder: for metal powders with high density (such as zirconium powder and titanium powder), the proportion of the coarse particle size section can be appropriately increased to enhance the stability of the powder packing; for metal powders with low density and easy agglomeration (such as boron powder), the proportion of the fine particle size section can be increased to improve the uniformity of the dispersion in the copper powder.

[0094] Step S2: powder mixing;

[0095] The above components are mixed uniformly by wet ball milling or dry mechanical mixing to obtain the inner layer powder mixture 2.

[0096] When wet ball milling, add ethanol as a solvent, and add 0.1-2wt% sodium polyacrylate. Ethanol as a solvent can reduce the adhesion between powder particles, reduce the generation of agglomeration phenomenon, and provide a favorable environment for uniform dispersion of particles; sodium polyacrylate as a water-based dispersant can form a charge barrier by adsorbing on the surface of the powder particles, further preventing particles from aggregating with each other, ensuring that the copper powder and refractory metal or easily oxidizable metal powder achieve full and uniform contact in the liquid medium.

[0097] Wet ball milling can effectively adapt to the mixing needs of fine particle size powder (especially 10-50μm refractory metal powder), and the wrapping effect of the liquid medium can reduce the oxidation risk of the powder during the mixing process, while the mechanical impact force in the ball milling process can further refine part of the agglomerated coarse particles, making the particle size distribution of the powder mixture more uniform; in addition, the ethanol solvent is volatile and can be removed by subsequent vacuum drying, without leaving impurities in the powder, ensuring the purity of the inner powder mixture 2.

[0098] When dry mechanical mixing, add zinc stearate and graphite, control the mixing speed at 20-50rpm, and the mixing time at 10-60 minutes. Zinc stearate as a solid organic dispersant can form a lubricating layer on the surface of the powder particles, reducing the frictional resistance between the particles and promoting the dispersion and mixing of the particles; graphite can assist in dispersion in this process and also play a reducing role in subsequent processes.

[0099] The control of mixing speed and time needs to consider both mixing effect and production efficiency. Too low speed and too short time will lead to insufficient mixing and local component enrichment; too high speed and too long time may cause excessive fragmentation or oxidation of powder particles, affecting the subsequent sintering effect. By selecting the above two mixing methods, the characteristics of different raw material systems can be adapted to ensure the consistency of the components of the inner powder mixture 2.

[0100] Dry mechanical mixing can avoid the time-consuming problem of drying process caused by liquid solvent, and the production process is more simple and efficient, especially suitable for metal powders sensitive to humidity or easily dissolved in solvent (such as lithium powder, magnesium powder); at the same time, the solid lubrication system of zinc stearate and graphite can reduce the wear of the mixing equipment and reduce the probability of excessive fragmentation of the powder particles, preserving the original particle size characteristics of the powder, and providing protection for the green body density during subsequent pressing.

[0101] Step S3: pressing forming;

[0102] The inner powder mixture 2 is placed in the outer copper foil 1 and pressed into a predetermined shape. The pressing pressure is controlled at 10-6000Mpa, and the holding time is 5-300s. The predetermined shape includes a cylinder, a cuboid or a special-shaped structure.

[0103] The synergistic control of pressure and holding time can make the inner layer powder form a dense green body in the copper foil. Suitable pressure can make the powder particles closely contact, reducing the porosity of the green body; sufficient holding time can make the pressure uniformly transmitted to each part of the green body, avoiding insufficient local density. If the pressure is insufficient or the holding time is too short, the porosity of the green body is too high, which will affect the combination between particles in the subsequent sintering process; if the pressure is too large or the holding time is too long, it may cause the outer copper foil 1 to be damaged, which cannot play the role of protecting the inner layer powder.

[0104] The preset various shape designs can meet the feeding requirements of different melting scenes, without the need for subsequent additional processing and shaping, improving the consistency and convenience of the production process. The inner layer powder mixture 2 is placed in the outer copper foil 1 for pressing, and the copper foil can play a restraining and protecting role during the pressing process to prevent powder leakage, and at the same time provide a stable forming boundary for the green body.

[0105] Step S4: sintering treatment;

[0106] The sintering is carried out under vacuum or inert atmosphere, the sintering temperature is 600-1100°C, and the holding time is 1-48 hours.

[0107] Among them, the vacuum degree is controlled to be ≤1 Pa, and the inert atmosphere is selected to be argon or nitrogen. The high vacuum environment can effectively exhaust the oxygen in the sintering space, and the inert atmosphere can isolate the external oxygen from entering, both of which can maximize the inhibition of the oxidation reaction of refractory metal or easily oxidized metal powder, avoiding the generation of oxidation impurities to affect the purity of the product.

[0108] The sintering adopts a segmented heating mode, and the heating rate is 5-15°C / min, and the temperature is kept after rising to the sintering temperature. The segmented heating and precise control of the heating rate can avoid the inconsistency of the thermal expansion rate of the copper foil and the inner layer powder due to the rapid heating, which in turn causes the green body to crack or the copper foil and the powder to separate; at the same time, it can prevent the loss of part of the easily volatile elements caused by the sudden rise of local temperature, and ensure the stability of the proportion of each component.

[0109] The setting of sintering temperature and holding time needs to be adjusted according to the characteristics of raw materials. Suitable temperature can promote the atomic diffusion between powder particles, making the particles combine with each other to form a stable structure; sufficient holding time can ensure that the diffusion process is fully carried out, improving the density and structural strength of the composite, and providing protection for the rapid dissolution performance when used as an intermediate alloy in the future.

[0110] Step S5: cooling forming;

[0111] Cooling to room temperature to obtain the metal composite. The slow cooling process can avoid the generation of thermal stress inside the composite due to sudden temperature drop, prevent defects such as cracks and deformation, and ensure the structural integrity and dimensional stability of the composite. The cooled composite retains the uniform distribution of the inner layer powder composition and the protective structure of the outer copper foil 1, and can be directly used as an intermediate alloy in the subsequent copper alloy smelting process.

[0112] On the basis of the above preparation method, the mixing and sintering process is further optimized to form a new improvement point: 1. In the mixing process of step S2, a composite dispersing system of "main dispersant + auxiliary dispersant" is used;

[0113] The body is: when wet ball milling, in addition to adding sodium polyacrylate, 0.05-0.2wt% of polyethylene glycol is additionally added, and the polyethylene glycol can synergistically act with the sodium polyacrylate to further optimize the dispersing effect, especially for small particle size refractory metal powders (such as boron powder, lithium powder), to avoid excessive agglomeration in the liquid medium; when dry mechanical mixing, 0.1-0.3wt% of polyvinyl alcohol is added on the basis of zinc stearate, and the viscosity of polyvinyl alcohol can enhance the adsorption stability of the dispersant on the surface of the powder particles, and improve the flowability and forming effect of the mixed powder.

[0114] 2. In the sintering process of step S4, a gradient sintering process is used instead of a single temperature holding;

[0115] Specifically: in the first stage, the temperature is raised to 800℃ at a rate of 5-8℃ / min, and the temperature is held for 2-4 hours, so that the inner layer powder particles are preliminarily diffused and combined, and at the same time, the residual trace amount of solvent or gas in the powder is discharged; in the second stage, the temperature is raised to the target sintering temperature (600-1100℃) at a rate of 8-12℃ / min, and the temperature is held for 1-48 hours, to promote deep combination between the particles; in the third stage, the temperature is lowered to 500℃ at a rate of 3-5℃ / min, and then naturally cooled to room temperature, to further reduce the generation of thermal stress.

[0116] The difference between this improvement point and the prior art is:

[0117] The prior art mostly uses a single dispersant and a single temperature sintering, without considering the dispersion requirement differences of powders with different particle sizes and different characteristics, and without controlling the gas discharge and thermal stress release in the sintering process. This improvement adapts to more diverse raw material combinations through a composite dispersing system, and the gradient sintering process takes into account the powder combination effect and structural stability, further improving the composition uniformity, density and mechanical properties of the metal composite, while expanding the adaptation range of the method to different refractory metals and easily oxidizable metals.

[0118] The preparation method of the present application can also be used in the preparation of other composites, for example:

[0119] Specific Example 1: Preparation of copper-chromium composite;

[0120] A1: Weigh out 84wt% copper powder, 15wt% chromium powder, 1wt% graphite, and 0.1wt% zinc stearate;

[0121] Among them, the copper powder selected is electrolytic copper powder with a particle size of 1~100μm and a purity of ≥99.7%, which can provide a stable copper matrix for the composite and ensure the basic performance of subsequent alloying.

[0122] The chromium powder is graded by particle size distribution: 35% fine particles (10~50μm), 45% medium particles (50~200μm), and 20% coarse particles (200~500μm). This distribution allows for the close packing of chromium powder in copper powder, reducing the gaps between powder particles. The graphite used is natural flake graphite with a particle size of 1~20μm and a carbon content of ≥99%. It can assist in dispersion during mixing and play a reducing role during sintering. Zinc stearate, as a solid organic dispersant, has a purity of ≥98%, which can reduce the frictional resistance between powder particles and prevent agglomeration during mixing.

[0123] A2: After dry mechanical mixing, it is pressed into a cylinder;

[0124] The dry mechanical mixing process is carried out in a sealed mixing tank, with argon gas introduced for protection to isolate the chromium powder from the air and prevent oxidation of the chromium powder during the mixing process. The mixing speed is set to 30 rpm and the mixing time is controlled to 40 minutes. This combination of parameters allows the copper powder, chromium powder, graphite and zinc stearate to come into full contact, ensuring that the components are evenly distributed and there is no local enrichment of components.

[0125] After mixing, the powder mixture is placed in a cylindrical mold and pressed into shape. The pressing pressure is 300 MPa, and the holding time is 60 seconds. The synergistic effect of the pressure and holding time ensures that the powder particles are in close contact, resulting in a density ≥8.1 g / cm³. 3 The cylindrical blank is designed to meet the feeding requirements of most industrial smelting equipment and can be used directly without additional processing. At the same time, the cylindrical structure allows for uniform heat transfer during sintering, avoiding incomplete sintering in certain areas.

[0126] A3: Vacuum sintering (1050℃, 48 hours);

[0127] The sintering process is carried out in a vacuum sintering furnace. First, the vacuum degree in the furnace is evacuated to ≤1Pa to remove the oxygen in the furnace. Then, the temperature is raised in stages: the temperature is raised to 800℃ at a rate of 10℃ / min and held for 2 hours to remove the trace gases and zinc stearate decomposition products remaining in the powder. Then, the temperature is raised to 1050℃ at a rate of 8℃ / min and held for 48 hours.

[0128] The sintering temperature of 1050℃ is lower than the melting point of copper (1083℃) and higher than the diffusion temperature of chromium, which can promote the atomic diffusion between copper powder and chromium powder, form a stable bond between particles, and avoid composition segregation caused by excessive melting of copper matrix; the holding time of 48 hours can ensure that the diffusion process is fully carried out, improve the density and structural stability of the composite, and finally make the density of the composite reach 8.6g / cm 3 The above.

[0129] In the embodiment, the oxygen content of the alloy is less than 50ppm, which is much lower than the case without reducing agent; chromium as an easily oxidized metal, is easy to react with oxygen to form chromium oxide impurities in high temperature environment, affecting the performance of the alloy. In this embodiment, graphite will slowly release carbon elements during sintering, which will react with residual oxygen in the furnace and the oxide film on the surface of chromium powder to generate carbon dioxide gas, thereby effectively inhibiting the oxidation of chromium powder; at the same time, the vacuum environment isolates the entry of external oxygen, further reducing the occurrence of oxidation reaction. Inductively coupled plasma mass spectrometry (ICP-MS) detection shows that the oxygen content of the obtained copper-chromium composite is less than 50ppm, while the oxygen content in the comparative case without adding graphite is usually more than 1000ppm, and the oxidation inhibition effect of this embodiment is significant, which ensures the purity of the composite.

[0130] The obtained composite is used for subsequent smelting of copper-chromium alloy, and the smelting temperature is reduced to 1300℃, and the composition uniformity is significantly improved; the above copper-chromium composite is used as an intermediate alloy and put into a 1-ton vacuum smelting furnace to prepare a copper-chromium alloy.

[0131] Because the chromium powder in the composite has formed a uniformly dispersed premixed structure with the copper powder, and the chromium powder has been combined with the sintering through the classification of particle size ratio, it can be quickly dissolved at a smelting temperature of 1300℃, which is more than 200℃ lower than the traditional direct smelting process (more than 1500℃), greatly reducing energy consumption.

[0132] Specific embodiment two: preparation of copper-niobium composite;

[0133] B1: weigh 89wt% of copper powder, 10wt% of niobium powder, isopropyl alcohol as solvent, and add 1wt% of polyethylene glycol;

[0134] The copper powder is selected from atomized copper powder with a particle size of 1-100 pm, a purity of ≥99.7%, high sphericity and good fluidity, which can provide a uniform dispersion matrix for the niobium powder; the niobium powder is selected from a graded particle size ratio, a fine particle size section (10-50 pm) accounting for 30%, a medium particle size section (50-200 pm) accounting for 50%, and a coarse particle size section (200-500 pm) accounting for 20%, which can reduce the agglomeration of the niobium powder in the copper powder and improve the bulk density of the mixed powder; the isopropyl alcohol is selected from an industrial grade solvent with a purity of ≥99.5%, which is volatile and chemically stable, can reduce the adhesion between the powder particles, and will not react with the raw materials;

[0135] The polyethylene glycol is selected from a type with a molecular weight of 2000-6000 and a purity of ≥99%, which can be adsorbed on the surface of the copper powder and niobium powder particles as a non-ionic surfactant, forming a steric hindrance effect to prevent the particles from gathering together.

[0136] B2: vacuum drying after wet ball milling;

[0137] The wet ball milling is carried out in a planetary ball mill, the ball milling tank is made of polyurethane, the grinding balls are niobium oxide balls with a diameter of 5-10 mm, and the ball-to-material ratio is 10:1, which can ensure that the powder particles are subjected to sufficient mechanical impact force and grinding force during ball milling;

[0138] The ball milling speed is set to 200 rpm, and the ball milling time is controlled to 6 hours, which can further refine the powder particles and promote the uniform dispersion of the components, avoiding local enrichment of the components.

[0139] After ball milling, the powder slurry containing the solvent is transferred to a vacuum drying oven for drying, the drying temperature is set to 80°C, the vacuum degree is ≤1×10 -2 Pa, and the drying time is 12 hours; this drying condition can quickly remove the isopropyl alcohol solvent in the slurry, while avoiding oxidation of the niobium powder or decomposition of the polyethylene glycol due to high temperature, ensuring the purity and dispersion of the powder mixture after drying, and the water content of the dried powder is ≤0.1%.

[0140] B3: sintering in an inert atmosphere after pressing (1070°C, 24 hours);

[0141] The dried powder mixture is placed in a cuboid mold during the pressing process, and a hydraulic press is used for pressing and forming, the pressing pressure is 500 Mpa, and the pressure holding time is 90 s, which can make the powder particles fully contact to form a cuboid blank with a density of ≥8.0 g / cm 3 ;

[0142] The cuboid shape facilitates subsequent batch stacking sintering, and can improve the uniformity of heat transfer in the sintering process. The sintering is performed in a tube-type sintering furnace. First, argon gas (purity ≥ 99.99%) is introduced into the furnace to replace the air in the furnace. The flow rate of the argon gas is controlled to be 0.5 L / min. After 30 minutes of continuous replacement, the temperature is raised.

[0143] The temperature is raised to 600°C at a rate of 8°C / min, and the powder is kept at this temperature for 1 hour to discharge the trace amount of gas remaining in the powder. Then, the temperature is raised to 1070°C at a rate of 10°C / min, and the powder is kept at this temperature for 24 hours.

[0144] The sintering temperature of 1070°C is lower than the melting point of copper, which can promote the atomic diffusion between the copper powder and the niobium powder, so that stable bonding is formed between the particles, and segregation caused by copper-based melting is avoided. The 24-hour holding time can ensure that the diffusion process is fully performed, and the density and structural stability of the composite are improved. The density of the final composite reaches 8.7 g / cm 3 Above; the argon atmosphere can continuously isolate external oxygen and inhibit the oxidation of the niobium powder.

[0145] The oxidation rate of the product is less than 0.5%, and the niobium element is uniformly distributed. Niobium is an easily oxidized metal, which can react with oxygen to form niobium oxide in a high-temperature environment, affecting the performance of the composite and the subsequent alloy.

[0146] In this embodiment, the liquid medium wrapping of wet ball milling, the low-oxygen environment of vacuum drying, and the argon protection in the sintering process form an anti-oxidation system throughout the process, effectively reducing the contact between the niobium powder and oxygen. At the same time, the improvement of the uniformity of the powder mixture also avoids the intensification of oxidation caused by the local aggregation of the niobium powder.

[0147] The oxidation rate of the copper-niobium composite obtained by the oxygen-nitrogen-hydrogen analyzer is less than 0.5%, which is much lower than the 300 ppm of the copper-niobium intermediate alloy prepared by the traditional process. Through scanning electron microscopy (SEM) observation and energy spectrum analysis (EDS), the niobium element is uniformly distributed in the copper matrix without obvious agglomeration or segregation. The relative deviation of the niobium element content in 10 randomly selected detection areas is ≤±0.3%, which provides a guarantee for the composition uniformity of the subsequent smelting of copper-niobium alloy.

[0148] It should be noted that, in order to simplify the description of the present disclosure and help understand one or more embodiments of the present disclosure, in the foregoing description of embodiments of the present disclosure, various features are sometimes combined into one embodiment, figure or description thereof.

Claims

1. A metal composite, characterized in that, include: An outer layer of copper foil and an inner layer of powder mixture, with the outer layer of copper foil tightly wrapping the inner layer of powder mixture; The inner layer powder mixture consists of copper powder, refractory or easily oxidizable metal powder, dispersant and graphite; The refractory or easily oxidized metal powder is one or more combinations of zirconium, beryllium, boron, magnesium, silicon, calcium, lithium, iron, manganese, phosphorus, titanium, tungsten, molybdenum, chromium, and niobium; The dispersant is one or a combination of alcohols, water-based dispersants, nonionic surfactants, or solid organic dispersants; The amount of graphite added is 0.1% to 5% of the total mass of the powder mixture.

2. The metal composite according to claim 1, characterized in that: The outer copper foil has a thickness of 0.1~2mm and is made of high-purity copper foil.

3. The metal composite according to claim 2, characterized in that: The particle size of copper powder is 1~1000μm, and the particle size of refractory metal or easily oxidized metal powder is 10~500μm.

4. The metal composite according to claim 1, characterized in that: The alcohol dispersant is ethanol or isopropanol; The water-based dispersant is sodium polyacrylate or sodium hexametaphosphate; The nonionic surfactant is polyethylene glycol or Tween 80; The solid organic dispersant is zinc stearate or polyvinyl alcohol.

5. The metal composite according to claim 1, characterized in that: In the inner layer powder mixture, the mass percentage of copper powder is 50% to 95%, the mass percentage of refractory metal or easily oxidized metal powder is 5% to 50%, and the mass percentage of dispersant is 0.05% to 3%.

6. A preparation method, characterized in that, It is used in the preparation of the metal composite according to any one of claims 1-5. Includes the following steps: S1: Weigh out copper powder, refractory or easily oxidized metal powder, dispersant and graphite according to the specified ratio; S2: The above components are mixed evenly using wet ball milling or dry mechanical mixing to obtain an inner layer powder mixture; S3: Place the inner layer powder mixture inside the outer layer copper foil and press it into a preset shape; S4: Sintering is carried out under vacuum or inert atmosphere at a temperature of 600~1100℃ and a holding time of 1~48 hours. S5: Cool to room temperature to obtain the metal composite.

7. The preparation method according to claim 6, characterized in that: In step S2, ethanol is added as a solvent during wet ball milling, and 0.1~2wt% of sodium polyacrylate is added; zinc stearate and graphite are added during dry mechanical mixing, the mixing speed is 20~50 rpm, and the mixing time is 10~60 minutes.

8. The preparation method according to claim 6, characterized in that: In step S3, the pressing pressure is 10~6000Mpa, the holding time is 5~300s, and the preset shape is a cylinder, cuboid or irregular structure.

9. The preparation method according to claim 6, characterized in that: In step S4, the vacuum degree is ≤1Pa, and the inert atmosphere is argon or nitrogen; the sintering adopts a segmented heating method with a heating rate of 5~15℃ / min, and the temperature is held after reaching the sintering temperature.

Images