A method for preparing high-strength, high-conductivity copper alloy by injection molding

Abstract

A method for preparing a high-strength, high-conductivity copper alloy by injection molding belongs to the field of powder metallurgy copper alloy preparation technology. The method includes: S1, preparing 50-500 nm nanoscale ultrafine copper composite powder using a chemical co-precipitation method; S2, mixing the ultrafine copper composite powder obtained in step S1 with polyvinyl butyral (PVB), granulating the mixture, and passing it through a 600-mesh sieve to obtain near-spherical hydroxide coarse composite powder with a particle size ≤23 μm; S3, subjecting the coarse composite powder to hydrogen calcination and reduction treatment to obtain near-spherical atomically mixed copper composite powder with a particle size ≤23 μm; S4, kneading and granulating the powder with a polyoxymethylene binder to prepare a feedstock; S5, obtaining a high-strength, high-conductivity copper alloy after injection molding, acid removal, and sintering. This invention achieves atomic-level mixing of powders through a chemical co-precipitation-hydrogen reduction process, which significantly reduces the sintering temperature and increases the density. The sintering temperature is reduced by about 100 °C, and the product has a relative density of ≥98%, electrical conductivity of ≥85% IACS, thermal conductivity of ≥350 W / (m·K), and tensile strength of 540–620 MPa, exhibiting excellent overall performance.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy copper alloy material preparation technology, specifically to a method for preparing a high-strength, high-conductivity copper alloy by injection molding and its ultrafine powder. Background Technology

[0002] High-strength, high-conductivity copper alloys, possessing both excellent electrical and thermal conductivity and high strength, have become indispensable key materials in fields such as electronics and information technology, new energy vehicles, aerospace, and high-end equipment. Their electrical and thermal conductivity far surpasses that of traditional structural materials, exceeding that of mold steel by 3 to 9 times. They achieve a balance between high strength and good plasticity, while also exhibiting advantages such as wear resistance and fatigue resistance. They are widely used in core applications such as integrated circuit lead frames, high-voltage connectors for new energy vehicles, lightweight structural components for aerospace, and traction motor components for rail transit, and have already achieved domestic substitution in some areas.

[0003] As modern high-end equipment rapidly develops towards miniaturization, lightweighting, integration, and structural complexity, higher demands are placed on the performance and manufacturing processes of high-strength, high-conductivity copper alloys. For example, 5G / 6G communication equipment requires miniaturized components that simultaneously meet the requirements of high-frequency signal transmission and efficient heat dissipation; new energy vehicle power battery systems require materials that can withstand complex operating loads while achieving high current conduction; and aerospace lightweight design necessitates high-performance materials with multiple functions to replace traditional composite solutions. Traditional processing methods such as rolling and forging, limited by their process characteristics, are unable to produce structurally complex components and can no longer meet the development needs of high-end equipment.

[0004] Metal injection molding (MIM) technology combines the complex shape manufacturing capabilities of plastic injection molding with the material versatility of powder metallurgy, providing an ideal solution for the efficient preparation of high-strength, high-conductivity copper alloys. This technology boasts near-net-shape advantages, enabling one-step molding of parts with complex structures such as internal channels, thin walls, and threads, reducing machining by over 90%; production accuracy can reach ±0.05 mm, with good batch consistency, making it suitable for large-scale industrial production; material utilization exceeds 95%, far superior to traditional machining, and it offers great design freedom, breaking through the limitations of traditional manufacturing processes. However, current commercial copper alloy powders used in injection molding face numerous key challenges, severely restricting the preparation of high-performance copper alloy products. On the one hand, commercial copper alloy powders have large particle sizes (usually greater than 10 μm) and uneven particle size distribution, resulting in a small specific surface area and insufficient sintering driving force. Sintering must be carried out at high temperatures of 1000–1050 ℃, which is close to the melting point of copper (1085 ℃). This not only consumes a lot of energy, but also easily leads to coarse grains and an increased risk of product deformation. On the other hand, traditional mechanical mixing methods are difficult to achieve atomic-level uniform distribution of alloying elements, which easily leads to compositional segregation. Furthermore, oxides on the powder surface can hinder atomic diffusion between particles, increase the sintering activation energy, and ultimately make it difficult to densify the products. The relative density is usually below 95%, and the core indicators such as electrical conductivity, thermal conductivity, and mechanical properties cannot meet the requirements of high-end equipment.

[0005] Therefore, developing a method for preparing copper alloy powder that can reduce sintering temperature, activate sintering to promote densification, and achieve uniform mixing of atomic-level components, and combining it with injection molding technology to prepare high-performance, high-strength, and high-conductivity copper alloys, has become a pressing technical challenge in this field. Summary of the Invention

[0006] To address the problems of uneven alloy element mixing, low sintering densification, and the inability of the final product to meet high-end requirements in existing injection-molded copper alloy preparation processes, this invention provides a method for preparing high-strength, high-conductivity copper alloys and their ultrafine powders via injection molding. By combining a chemical co-precipitation process with suitable granulation, reduction, and sintering processes, 50-500 nm nanoscale ultrafine copper composite powders are prepared. Simultaneously, the powders are modified for MIM process adaptability and sintering activation are achieved, ultimately yielding copper alloy products with high density, high strength, and high conductivity.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a high-strength, high-conductivity copper alloy by injection molding, characterized by comprising the following steps:

[0009] S1. 50-500 nm nanoscale ultrafine copper composite powder was prepared by chemical co-precipitation method;

[0010] S2. The ultrafine copper composite powder obtained in step S1 is mixed with polyvinyl butyral (PVB) and granulated, then sieved to obtain a near-spherical hydroxide coarse composite powder with a particle size ≤23 μm.

[0011] S3. The coarse composite powder is subjected to hydrogen calcination and reduction treatment to obtain a copper composite powder with a particle size ≤23 μm and near-spherical atomic-level mixture after calcination.

[0012] S4. The calcined copper composite powder with a particle size ≤23 μm and near-spherical atomic-level mixture obtained in step S3 is kneaded and crushed with a binder to obtain copper metal injection molding feed.

[0013] S5. Injection molding and sintering: The copper metal injection molding feedstock is injection molded to obtain a green blank. After degreasing treatment, the green blank is sintered in a hydrogen atmosphere to obtain a high-strength and high-conductivity copper alloy.

[0014] Further, the chemical coprecipitation method in step S1 includes: dissolving copper nitrate with one or more selected from zirconium oxychloride, yttrium nitrate, chromium nitrate, and ammonium paratungstate in deionized water; adding ammonium nitrate to the solution pH of 9–10 under stirring conditions of 60–80 °C and 600–1000 r / min; collecting the precipitate and washing and filtering it to neutrality; wherein the amounts of zirconium oxychloride, yttrium nitrate, chromium nitrate, and ammonium paratungstate added are 0.5–5%, 0–1.5%, 0–2%, and 0–10% of the mass of copper nitrate (calculated as copper), respectively; the concentration of copper nitrate is 0.5–1.5 mol / L; and the addition rate of ammonium nitrate is 0.5–2 mL / min.

[0015] Further, in step S2, the amount of polyvinyl butyral used is 0.35–1.5% of the mass of the ultrafine copper composite powder. It is first dissolved in hot anhydrous ethanol and then mixed with the powder. After granulation, it is passed through a 600-mesh sieve, and the resulting near-spherical hydroxide coarse composite powder has a particle size ≤23μm.

[0016] Further, in step S3, the calcination and hydrogen reduction treatment specifically involves: placing the coarse composite powder in a hydrogen atmosphere, heating it to 500–600 ℃ at a rate of 5–10 ℃ / min, holding it at that temperature for 30–90 min, and then cooling it with the furnace. The purity of the hydrogen used is not less than 99.99%, and the flow rate is 2 m³ / h.

[0017] Further, in step S4, the volume fraction of the copper composite powder is 55–70%, with the remainder being a binder; the binder is a polyoxymethylene-based binder, the composition of which, by mass percentage, includes: 5–15% polypropylene, 5–15% stearic acid, 5–15% ethylene-vinyl acetate copolymer, with the remainder being polyoxymethylene.

[0018] Further, in step S4, the kneading is carried out at 170–190 °C for 1–2 h; the granulation is carried out at 175–190 °C, with an extrusion speed of 10–20 Hz, a feeding speed of 5–10 Hz, a cutting speed of 5–10 Hz, and the resulting feed particle size of 2–3 mm and length of 2–5 mm.

[0019] Further, in step S5: the injection molding process parameters are: injection temperature 180–195 ℃, injection pressure 180–195 bar, mold temperature 110–135 ℃; the degreasing treatment is oxalic acid degreasing + thermal degreasing, wherein the oxalic acid degreasing process parameters are: furnace temperature 110–140 ℃, degreasing time 10–18 h, and after oxalic acid degreasing, the temperature is increased to 350–450 ℃ at 5–10 ℃ / min and held for 1–2 h for thermal degreasing to remove residual adhesives; the sintering process parameters are: heating at 5–8 ℃ / min to 900–950 ℃, holding for 2–4 h, hydrogen purity not less than 99.99%, flow rate 1.5–2.5 m³ / h, and cooling to room temperature with the furnace after sintering. During the sintering process, the atomically mixed powder achieves efficient densification due to its high activity, and the porosity is significantly reduced. After sintering, the copper alloy is cooled to room temperature in the furnace to obtain a high-strength, high-conductivity copper alloy product.

[0020] Furthermore, the copper alloy uses copper as a matrix and contains at least two of ZrO2, Y2O3, Cr2O3, and W, which are uniformly distributed in the copper matrix in the form of a dispersed phase.

[0021] Furthermore, the copper alloy has a relative density ≥98%, electrical conductivity at room temperature ≥85% IACS, tensile strength of 540–620 MPa, hardness ≥145 HV, and thermal conductivity ≥350 W / (m·K).

[0022] S5. Injection Molding and Sintering: Set the injection temperature to 180–195 ℃, injection pressure to 180–195 bar, and mold temperature to 110–135 ℃. Demold to obtain the green body. Degrease the green body: first, perform oxalic acid degreasing, controlling the furnace temperature at 110–140 ℃ for 10–18 h; after oxalic acid degreasing, perform thermal degreasing, heating at 5–10 ℃ / min to 350–450 ℃ and holding for 1–2 h.

[0023] The core process mechanism of this invention is a continuous synergistic process of PVB coating granulation and hydrogen calcination reduction, which solves the core problems of MIM process adaptability of 50-500 nm nanoscale ultrafine copper composite powder, insufficient powder sintering activity, and uneven mixing of alloying elements. PVB coating granulation optimizes the process performance of ultrafine powder, agglomerating it into a near-spherical hydroxide coarse composite powder with a particle size ≤23 μm suitable for MIM process, while forming a coating layer to prevent secondary agglomeration and oxidation. Hydrogen calcination reduction realizes the metallization of the near-spherical hydroxide coarse composite powder, eliminates surface oxides, and decomposes the alloying element hydroxide into a 50-500 nm nanoscale dispersed phase and achieves atomic-level uniform dispersion, while retaining fine grain characteristics to improve sintering activity, finally obtaining a near-spherical atomic-level mixed copper composite powder with a particle size ≤23 μm. The two processes complement each other and synergistically realize the modification of the MIM process adaptability of ultrafine powder and atomic-level mixing + sintering activity activation, ultimately achieving low-temperature sintering and high density, allowing the product to have both high strength and high electrical and thermal conductivity.

[0024] Compared with the prior art, the present invention has the following significant advantages:

[0025] 1. This invention uses a chemical co-precipitation method to prepare 50-500 nm nanoscale ultrafine copper composite powder. Combined with PVB granulation and hydrogen reduction treatment, the ultrafine powder is prepared into a near-spherical hydroxide coarse composite powder and then reduced to a near-spherical atomic-level mixed copper composite powder with a particle size ≤23 μm. This achieves atomic-level mixing of ZrO2, Y2O3, Cr2O3, W and copper, which solves the problem of component segregation caused by traditional mechanical mixing and the problem that ultrafine powder is not suitable for injection molding. At the same time, the ultrafine powder has a larger specific surface area and higher sintering activity, laying the foundation for subsequent efficient densification.

[0026] 2. The copper alloy products prepared by this invention have excellent comprehensive properties, with a relative density ≥98%, electrical conductivity ≥85% IACS, tensile strength ≥500 MPa, and thermal conductivity ≥350 W / (m·K), which can meet the stringent requirements of high-strength and high-conductivity copper alloys in high-end fields such as electronics and aerospace. Attached Figure Description

[0027] Figure 1 Scanning electron microscope (SEM) image of the ultrafine copper alloy powder prepared in Example 1. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0029] Example 1

[0030] A method for preparing a high-strength, high-conductivity copper alloy and its ultrafine powder by injection molding, comprising the following specific steps:

[0031] S1. Preparation of 50-500 nm nanoscale ultrafine copper composite powder: Copper nitrate, zirconium oxychloride, and yttrium nitrate were dissolved in deionized water, wherein the concentration of copper nitrate was 1 mol / L, the amount of zirconium oxychloride added was 2% of the mass of copper nitrate (calculated as copper), and the amount of yttrium nitrate added was 0.8% of the mass of copper nitrate; the mixed solution was heated to 70 ℃, stirred at 800 r / min, and ammonium nitrate was added at a rate of 1 mL / min until the pH of the solution was 9.5. After the reaction was completed, the solution was washed and filtered until neutral to obtain 50-500 nm nanoscale ultrafine copper composite powder.

[0032] S2. Granulation treatment: Weigh 1.0% of the mass of ultrafine copper composite powder, dissolve it in hot anhydrous ethanol, mix it with the powder until the ethanol evaporates, granulate it and pass it through a 600-mesh sieve to obtain a near-spherical hydroxide coarse composite powder with a particle size ≤23μm.

[0033] S3. Calcination and reduction: Near-spherical hydroxide coarse composite powder was placed in a hydrogen atmosphere (purity 99.99%, flow rate 2 m³ / h), heated to 550 ℃ at 8 ℃ / min, held for 60 min and then cooled with the furnace to obtain calcined copper composite powder with a particle size ≤23 μm and near-spherical atomic-level mixture.

[0034] S4. Preparation of feedstock: The volume fraction of calcined near-spherical copper composite powder with a particle size ≤23 μm is 65%, and the volume fraction of binder (polypropylene 10%, stearic acid 10%, ethylene-vinyl acetate copolymer 10%, polyoxymethylene 70%) is 35%. Knead at 180 ℃ for 1.5 h, and granulate at 185 ℃ (extrusion speed 15 Hz, feeding speed 8 Hz, cutting speed 8 Hz) to obtain feedstock with a particle size of 2–3 mm and a length of 2–5 mm.

[0035] S5. Injection Molding and Sintering: Injection temperature 185 ℃, injection pressure 190 bar, mold temperature 120 ℃ to obtain a green compact; the green compact is first degreased with oxalic acid, the furnace temperature is controlled at 125 ℃, the degreasing time is 14 h, then the temperature is increased to 400 ℃ at 8 ℃ / min and held for 1 h for hot degreasing; finally, in a hydrogen atmosphere (flow rate 2 m³ / h), the temperature is increased to 920 ℃ at 6 ℃ / min and held for 3 h for sintering, and then cooled with the furnace. In this embodiment, the sintering temperature is 920 ℃, which is 130 ℃ lower than the traditional process of 1050 ℃ in the background technology. The prepared copper alloy product has a relative density of 98.5%, an electrical conductivity of 88% IACS, a tensile strength of 580 MPa, a hardness of 150 HV, and a thermal conductivity of 362 W / (m·K).

[0036] Example 2

[0037] A method for preparing a high-strength, high-conductivity copper alloy and its ultrafine powder by injection molding, comprising the following specific steps:

[0038] S1. Preparation of 50-500 nm nanoscale ultrafine copper composite powder: Copper nitrate, chromium nitrate, and ammonium paratungstate are dissolved in deionized water, wherein the concentration of copper nitrate is 1.5 mol / L, the amount of chromium nitrate added is 1% of the mass of copper nitrate (calculated as copper), and the amount of ammonium paratungstate added is 5% of the mass of copper nitrate (calculated as copper). The mixed solution is heated to 65 °C, stirred at 700 r / min, and ammonium nitrate is added at a rate of 1 mL / min until pH=9.2. The solution is washed and filtered until neutral to obtain 50-500 nm nanoscale ultrafine copper composite powder.

[0039] S2. Granulation treatment: PVB is used at 0.8% of the powder mass, dissolved in hot anhydrous ethanol and mixed with the powder. After granulation, it is passed through a 600-mesh sieve to obtain a near-spherical hydroxide coarse composite powder with a particle size ≤23 μm.

[0040] S3. Calcination and reduction: Under a hydrogen atmosphere (purity 99.99%, flow rate 2 m³ / h), the temperature was increased to 520 ℃ at 6 ℃ / min, held for 80 min, and then cooled with the furnace to obtain a calcined copper composite powder with a particle size ≤23μm and near-spherical atomic-level mixture.

[0041] S4. Preparation of feedstock: The volume fraction of calcined near-spherical copper composite powder with a particle size ≤23 μm is 60%, and the volume fraction of binder (polypropylene 8%, stearic acid 12%, ethylene-vinyl acetate copolymer 10%, polyoxymethylene 70%) is 40%; knead at 175 ℃ for 2 h, and granulate at 180 ℃ (extrusion speed 12 Hz, feeding speed 6 Hz, cutting speed 6 Hz).

[0042] S5. Injection Molding and Sintering: Injection temperature 190 ℃, injection pressure 185 bar, mold temperature 130 ℃ to obtain a green compact; the green compact is first degreased with oxalic acid, the furnace temperature is controlled at 130 ℃, the degreasing time is 12 h, and then the temperature is increased to 380 ℃ at 7 ℃ / min and held for 2 h for hot degreasing; sintering is carried out in a hydrogen atmosphere, the temperature is increased to 930 ℃ at 5 ℃ / min and held for 3.5 h. In this embodiment, the sintering temperature is 930 ℃, which is 120 ℃ lower than the traditional sintering temperature of 1050 ℃. The prepared copper alloy product has a relative density of 98.2%, an electrical conductivity of 86% IACS, a tensile strength of 565 MPa, a hardness of 148 HV, and a thermal conductivity of 366 W / (m·K), achieving the dual effects of efficient densification and significant energy saving.

[0043] Example 3

[0044] A method for preparing a high-strength, high-conductivity copper alloy and its ultrafine powder by injection molding, comprising the following specific steps:

[0045] S1. Preparation of 50-500 nm nanoscale ultrafine copper composite powder: Copper nitrate, zirconium oxychloride, and chromium nitrate were dissolved in deionized water, wherein the concentration of copper nitrate was 1 mol / L, the amount of zirconium oxychloride added was 2% of the mass of copper nitrate (calculated as copper), and the amount of chromium nitrate added was 1% of the mass of copper nitrate (calculated as copper). The mixed solution was heated to 75 °C, stirred at 900 r / min, and ammonium nitrate was added at a rate of 2 mL / min until pH=9.8. The solution was washed and filtered until neutral to obtain 50-500 nm nanoscale ultrafine copper composite powder.

[0046] S2. Granulation treatment: PVB is used at 0.75% of the mass of ultrafine copper composite powder. It is dissolved in hot anhydrous ethanol and mixed. The mixture is then granulated and passed through a 600-mesh sieve to obtain near-spherical hydroxide coarse composite powder with a particle size ≤23 μm.

[0047] S3. Calcination and reduction: Under a hydrogen atmosphere (purity 99.99%, flow rate 2 m³ / h), the temperature was increased to 580 ℃ at 7℃ / min, held for 70 min, and then cooled with the furnace to obtain a calcined copper composite powder with a particle size ≤23μm and near-spherical atomic-level mixture.

[0048] S4. Preparation of feedstock: Calcinated copper composite powder with a volume fraction of 62%, binder (polypropylene 12%, stearic acid 8%, ethylene-vinyl acetate copolymer 10%, polyoxymethylene 70%), kneaded at 185 °C for 1.2 h, and granulated at 188 °C (parameters same as in Example 1).

[0049] S5. Injection Molding and Sintering: Injection temperature 192 ℃, injection pressure 192 bar, mold temperature 125 ℃; oxalic acid degreasing (furnace 135 ℃, time 16 h) + hot degreasing (heating at 9 ℃ / min to 420 ℃, holding for 1.5 h); sintering in a hydrogen atmosphere at 7 ℃ / min to 900 ℃, holding for 4 h. Performance tests show that the ZrO2-Cr2O3 composite addition combined with low-temperature ultra-long-time sintering achieves peak density. The prepared copper alloy product has a relative density of 99.0%, electrical conductivity of 89% IACS, tensile strength of 595 MPa, hardness of 152 HV, and thermal conductivity of 369 W / (m·K), exhibiting the best overall performance.

[0050] Example 4

[0051] A method for preparing a high-strength, high-conductivity copper alloy and its ultrafine powder by injection molding, comprising the following specific steps:

[0052] S1. Preparation of 50-500 nm nanoscale ultrafine copper composite powder: Copper nitrate, ammonium paratungstate, and yttrium nitrate were dissolved in deionized water, wherein the concentration of copper nitrate was 0.5 mol / L, the amount of ammonium paratungstate added was 5% of the mass of copper nitrate (calculated as copper), and the amount of yttrium nitrate added was 0.75% of the mass of copper nitrate (calculated as copper); the mixed solution was heated to 68 ℃, stirred at 850 r / min, and ammonium nitrate was added at a rate of 1 mL / min until pH=9.3, and then washed and filtered until neutral.

[0053] S2. Granulation treatment: PVB is used at 0.35% of the mass of ultrafine copper composite powder. It is dissolved in hot anhydrous ethanol and mixed. The mixture is then granulated and passed through a 600-mesh sieve to obtain near-spherical hydroxide coarse composite powder with a particle size ≤23 μm.

[0054] S3. Calcination and reduction: Under a hydrogen atmosphere (purity 99.99%, flow rate 2 m³ / h), the temperature was increased to 520 ℃ at 9 ℃ / min, held for 85 min, and then cooled with the furnace to obtain a calcined copper composite powder with a particle size ≤23μm and near-spherical atomic-level mixture.

[0055] S4. Preparation of feedstock: Calcinated copper composite powder with a volume fraction of 68%, binder (polypropylene 8%, stearic acid 12%, ethylene-vinyl acetate copolymer 12%, polyoxymethylene 68%), kneaded at 178 ℃ for 1.8 h, and granulated at 190 ℃ (parameters same as in Example 1).

[0056] S5. Injection Molding and Sintering: Injection temperature 188 ℃, injection pressure 188 bar, mold temperature 115 ℃; oxalic acid degreasing (furnace 115 ℃, time 18 h) + hot degreasing (heating at 6 ℃ / min to 390 ℃, holding for 2 h); sintering in a hydrogen atmosphere at 5 ℃ / min to 950 ℃, holding for 2 h. The W-Y2O3 composite addition still achieves high strength under high-temperature short-time sintering, meeting the needs of efficient industrial production. The prepared copper alloy products have a relative density of 98.1%, electrical conductivity of 85% IACS, tensile strength of 610 MPa, hardness of 155 HV, and thermal conductivity of 360 W / (m·K).

[0057] Example 5

[0058] A method for preparing a high-strength, high-conductivity copper alloy and its ultrafine powder by injection molding, comprising the following specific steps:

[0059] S1. Preparation of 50-500 nm nanoscale ultrafine copper composite powder: Copper nitrate, zirconium oxychloride, and ammonium paratungstate were dissolved in deionized water, wherein the concentration of copper nitrate was 1 mol / L, the amount of zirconium oxychloride added was 1.5% of the mass of copper nitrate (calculated as copper), and the amount of ammonium paratungstate added was 3% of the mass of copper nitrate (calculated as copper). The mixed solution was heated to 72 °C and stirred at 820 r / min. Ammonium nitrate was added at a rate of 2 mL / min until the pH of the solution was 9.6. After the reaction was completed, the solution was washed and filtered until neutral to obtain 50-500 nm nanoscale ultrafine copper composite powder.

[0060] S2. Granulation treatment: Weigh 0.9% of the mass of ultrafine copper composite powder, dissolve it in hot anhydrous ethanol, mix it with the powder until the ethanol evaporates, granulate it and pass it through a 600-mesh sieve to obtain a near-spherical hydroxide coarse composite powder with a particle size ≤23 μm.

[0061] S3. Calcination and reduction: The coarse composite powder was placed in a hydrogen atmosphere (purity 99.99%, flow rate 2 m³ / h), heated to 540 ℃ at 7.5℃ / min, held for 75 min and then cooled with the furnace to obtain a calcined copper composite powder with a particle size ≤23μm and near-spherical atomic-level mixture.

[0062] S4. Preparation of feedstock: The volume fraction of the calcined copper composite powder is 64%, and the volume fraction of the binder (polypropylene 11%, stearic acid 9%, ethylene-vinyl acetate copolymer 10%, polyoxymethylene 70%) is 36%. The powder is kneaded at 182 °C for 1.6 h and granulated at 186 °C (extrusion speed 14 Hz, feeding speed 7 Hz, cutting speed 7 Hz) to obtain feedstock with a particle size of 2–3 mm and a length of 2–5 mm.

[0063] S5. Injection Molding and Sintering: Injection temperature 187 ℃, injection pressure 191 bar, mold temperature 122 ℃, to obtain a green compact; the green compact is first degreased with oxalic acid, the furnace temperature is controlled at 128 ℃, the degreasing time is 15 h, then the temperature is increased to 395 ℃ at 7.5 ℃ / min and held for 1.2 h for hot degreasing; finally, in a hydrogen atmosphere (flow rate 2 m³ / h), the temperature is increased to 910 ℃ at 6.5 ℃ / min and held for 3.5 h for sintering, and then cooled with the furnace. In this embodiment, ZrO2-W composite additive is used, which takes into account both strength and thermal conductivity. The sintering temperature is reduced by 140 ℃ compared with the traditional process. The prepared copper alloy product has a relative density of 98.7%, electrical conductivity of 87% IACS, tensile strength of 575 MPa, hardness of 149 HV, and thermal conductivity of 365 W / (m·K).

[0064] Comparative Example 1

[0065] Commercial copper powder (particle size > 10 μm) was mechanically mixed with 2% ZrO2 and 0.8% Y2O3. Green bodies (without granulation or sintering reduction) were prepared using the feed ratio and injection molding process as described in Example 1. Oxalic acid degreasing was performed (furnace temperature 125 ℃, degreasing time 14 h), followed by sintering at 1050 ℃ (conventional standard sintering temperature) under a hydrogen atmosphere for 2 h. Other sintering parameters were consistent with Example 1. Performance test results: relative density 94.5%, electrical conductivity 76% IACS, tensile strength 420 MPa, hardness 125 HV, thermal conductivity 320 W / (m·K).

[0066] Comparative Example 2

[0067] The 50-500 nm nanoscale ultrafine copper composite powder (Cu + 2% ZrO2 + 0.8% Y2O3, atomically mixed) from Example 1 was used, along with the feeding preparation process, injection parameters, and oxalic acid degreasing + thermal degreasing process (without granulation or sintering reduction). Only the sintering holding time was adjusted to 1 h (other sintering parameters were the same as in Example 1: 920 ℃, hydrogen atmosphere). Performance test results: relative density 92.3%, electrical conductivity 79% IACS, tensile strength 460 MPa, hardness 130 HV, thermal conductivity 335 W / (m·K).

[0068] The detailed description of the disclosed embodiments is sufficient to enable those skilled in the art to implement or use the present invention. It will be apparent to those skilled in the art that various modifications, adjustments, or adaptations can be made to these embodiments, and the core principles defined herein can be applied to other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention should not be limited to the specific embodiments shown herein, but should be accorded the widest scope consistent with the principles, technical solutions, and novel features disclosed herein.

Claims

1. A method for preparing a high-strength, high-conductivity copper alloy by injection molding, characterized in that, Includes the following steps: S1. 50-500 nm nanoscale ultrafine copper composite powder was prepared by chemical co-precipitation method; S2. The ultrafine copper composite powder obtained in step S1 is mixed with polyvinyl butyral (PVB) and granulated, then sieved to obtain a near-spherical hydroxide coarse composite powder with a particle size ≤23 μm. S3. The coarse composite powder is subjected to hydrogen calcination and reduction treatment to obtain a copper composite powder with a particle size ≤23 μm and near-spherical atomic-level mixture after calcination. S4. The calcined copper composite powder with a particle size ≤23 μm and near-spherical atomic-level mixture obtained in step S3 is kneaded and crushed with a binder to obtain copper metal injection molding feed. S5. Injection molding and sintering: The copper metal injection molding feedstock is injection molded to obtain a green blank. After degreasing treatment, the green blank is sintered in a hydrogen atmosphere to obtain a high-strength and high-conductivity copper alloy.

2. The preparation method according to claim 1, characterized in that, The chemical coprecipitation method in step S1 includes: dissolving copper nitrate with one or more of zirconium oxychloride, yttrium nitrate, chromium nitrate, and ammonium paratungstate in deionized water; adding ammonium nitrate to the solution pH of 9–10 under stirring conditions of 60–80 °C and 600–1000 r / min; collecting the precipitate and washing and filtering it to neutral; the amounts of zirconium oxychloride, yttrium nitrate, chromium nitrate, and ammonium paratungstate added are 0.5–5%, 0–1.5%, 0–2%, and 0–10% of the mass of copper nitrate (calculated as copper), respectively; the concentration of copper nitrate is 0.5–1.5 mol / L; and the addition rate of ammonium nitrate is 0.5–2 mL / min.

3. The preparation method according to claim 1, characterized in that, In step S2, the amount of polyvinyl butyral used is 0.35–1.5% of the mass of the ultrafine copper composite powder. It is first dissolved in hot anhydrous ethanol and then mixed with the powder. After granulation, it is passed through a 600-mesh sieve. The resulting near-spherical hydroxide coarse composite powder has a particle size ≤23μm.

4. The preparation method according to claim 1, characterized in that, In step S3, the calcination and hydrogen reduction treatment specifically involves: placing the coarse composite powder in a hydrogen atmosphere, heating it to 500–600 ℃ at a rate of 5–10 ℃ / min, holding it at that temperature for 30–90 min, and then cooling it with the furnace. The purity of the hydrogen used is not less than 99.99%, and the flow rate is 2 m³ / h.

5. The preparation method according to claim 1, characterized in that, In step S4, the volume fraction of the copper composite powder is 55–70%, with the remainder being a binder; the binder is a polyoxymethylene-based binder, and its composition by mass percentage includes: 5–15% polypropylene, 5–15% stearic acid, 5–15% ethylene-vinyl acetate copolymer, with the remainder being polyoxymethylene.

6. The preparation method according to claim 1, characterized in that, In step S4, the kneading is carried out at 170–190 ℃ for 1–2 h; the granulation is carried out at 175–190 ℃, the extrusion speed is 10–20 Hz, the feeding speed is 5–10 Hz, the cutting speed is 5–10 Hz, and the resulting feed particle size is 2–3 mm and the length is 2–5 mm.

7. The preparation method according to claim 1, characterized in that, In step S5: the injection molding process parameters are: injection temperature 180–195 ℃, injection pressure 180–195 bar, mold temperature 110–135 ℃; the degreasing treatment is oxalic acid degreasing + thermal degreasing, wherein the oxalic acid degreasing process parameters are: furnace temperature 110–140 ℃, degreasing time 10–18 h, and after oxalic acid degreasing, the temperature is increased to 350–450 ℃ at 5–10 ℃ / min and held for 1–2 h for thermal degreasing to remove residual adhesives; the sintering process parameters are: the temperature is increased to 900–950 ℃ at 5–8 ℃ / min and held for 2–4 h, the hydrogen purity is not less than 99.99%, the flow rate is 1.5–2.5 m³ / h, and after sintering, the furnace is cooled to room temperature.

8. The injection-molded high-strength, high-conductivity copper alloy prepared by the preparation method according to any one of claims 1-7, characterized in that, The copper alloy uses copper as a matrix and contains at least two of ZrO2, Y2O3, Cr2O3, and W, which are uniformly distributed in the copper matrix in the form of dispersed phases.

9. The injection-molded high-strength, high-conductivity copper alloy prepared by the preparation method according to any one of claims 1-7, characterized in that, The copper alloy has a relative density ≥98%, electrical conductivity ≥85% IACS at room temperature, tensile strength of 540–620 MPa, hardness ≥145 HV, and thermal conductivity ≥350 W / (m·K).

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