Preparation method of dispersion copper with high density and low free oxygen content

Abstract

The invention relates to the technical field of copper alloy preparation, in particular to a preparation method of high-density low-free-oxygen-content dispersed copper, which comprises the following steps: preparing copper-aluminum powder through atomization powder preparation, carrying out internal oxidation and reduction by using the oxidized powder of the copper-aluminum powder as an oxygen source to obtain aluminum oxide / copper powder, filling the aluminum oxide / copper powder into a steel ladle sleeve, vacuumizing, introducing hydrogen, and carrying out high-density low-free-oxygen-content dispersed copper. Aluminum oxide / copper powder is subjected to on-line reduction at a high temperature, a powder ingot with low free oxygen is obtained after high-temperature hot degassing, and then hot isostatic pressing and hot extrusion are performed to obtain the dispersion copper with high density and low free oxygen content. The relative density of the obtained dispersion copper is larger than or equal to 98%, and the free oxygen content is smaller than or equal to 20 ppm. According to the method, a solid reducing agent is not introduced, external elements are not introduced, the high-density and low-free-oxygen-content dispersed copper is obtained through hydrogen online reduction, and the use requirement of a divertor is met.

Description

Technical Field

[0001] This invention relates to the field of copper alloy preparation technology, and in particular to a method for preparing high-density, low-free-oxygen-content dispersed copper. Background Technology

[0002] Dispersed copper is a material in which nanoscale, thermally stable dispersed phases are introduced into a copper matrix. By pinning grain boundaries and hindering dislocation movement, it enhances the strength and high-temperature resistance of the copper matrix. Dispersed copper is widely used in aerospace, electronics, and nuclear energy fields. Especially in the field of nuclear fusion, dispersed copper is considered the primary, or even the only, candidate material for heat sinks in water-cooled divertors. However, nuclear fusion divertors have very high requirements for dispersed copper, especially in that the free oxygen content must be as low as possible.

[0003] If copper contains oxygen, at high temperatures, hydrogen will react with cuprous oxide at the grain boundaries to generate high-pressure water vapor, causing the material to expand, crack, or even fail—this is known as "hydrogen sickness." Fusion reactors contain hydrogen isotopes such as deuterium and tritium, requiring the free oxygen content in the dispersed copper to be reduced to extremely low levels before they can be used.

[0004] The preparation of low-oxygen-grade dispersed copper typically involves adding boron as a reducing agent. However, boron is a neutron absorber, which does not meet the requirements for divertor applications. Publication No. CN109897982A discloses a high-airtightness, low-free-oxygen-content nano-dispersed copper alloy and its short-process preparation method, yielding dispersed copper with a free oxygen content ≤15ppm. However, it still requires a secondary reduction using Ca and La as solid reducing agents.

[0005] Publication No.: CN101195879A A method for preparing an Al2O3 dispersion-strengthened copper alloy involves using copper containing 0.05–0.6 wt% aluminum as the matrix. All copper-aluminum alloy powder is surface-oxidized and oxygenated at 150°C–500°C; cold isostatic pressing is then performed; internal oxidation is carried out at 700°C–950°C under nitrogen protection; the atmosphere is changed, and reduction and sintering are performed in hydrogen at 750°C–1000°C; finally, the mixture is heated to 750–950°C for extrusion and drawing to obtain the finished product. However, this process cannot guarantee extremely low free oxygen content, and the multiple contacts between the material and air during the process increase the risk of impurity introduction.

[0006] Therefore, there is an urgent need to propose a new method for preparing high-density, low-free-oxygen-content dispersed copper, which can reduce the free oxygen content in dispersed copper without introducing solid reducing agents and foreign elements, and solve the problems of hydrogen expansion and cracking of dispersed copper. Summary of the Invention

[0007] In view of this, the present invention aims to propose a method for preparing high-density, low-free-oxygen-content dispersed copper, which reduces the free oxygen content in dispersed copper without introducing solid reducing agents and foreign elements, thereby solving the problems of hydrogen expansion and cracking of dispersed copper.

[0008] This invention obtains copper-aluminum powder through atomization, uses the oxidized copper-aluminum powder as an oxygen source for internal oxidation and reduction to obtain alumina / copper powder, loads the alumina / copper powder into a steel liner, evacuates the liner, and then introduces hydrogen gas for online reduction of the alumina / copper powder at high temperature. After high-temperature thermal degassing, a powder ingot with low free oxygen is obtained. This ingot is then subjected to hot isostatic pressing and hot extrusion to obtain dispersed copper with high density and low free oxygen content. The dispersed copper obtained by this invention has a relative density ≥98% and a free oxygen content ≤20ppm. Essentially, this technology solves the problem of soft phase formation when copper oxide is used as an oxygen source by oxidizing copper and aluminum powder, thus improving the uniformity of the dispersed phase distribution. A steel cladding capable of simultaneous reduction and vacuuming is designed. Online reduction of alumina / copper powder within the steel cladding reduces the free oxygen content. Immediate vacuum sealing after reduction prevents the later introduction of oxygen, effectively controlling the free oxygen content. Densification of alumina / copper powder is achieved through hot isostatic pressing, and the density of dispersed copper is further improved through hot extrusion. Ultimately, high-density dispersed copper with low free oxygen content is obtained, with a relative density ≥98% and a free oxygen content ≤20ppm.

[0009] The technical solution of this invention is implemented as follows:

[0010] One object of the present invention is to disclose a method for preparing high-density, low-free-oxygen-content dispersed copper, comprising the following steps:

[0011] S1: Copper-aluminum alloy powder is prepared by water atomization or gas atomization.

[0012] S2: Take a portion of the copper-aluminum alloy powder from step S1 and oxidize it into copper oxide in an oxygen atmosphere;

[0013] S3: Mix the remaining copper-aluminum alloy powder with the copper oxide obtained in step S2 in a certain proportion, and then perform internal oxidation.

[0014] S4: The powder after internal oxidation is crushed, then reduced and crushed again to obtain aluminum oxide / copper powder;

[0015] S5: Lay heat insulation felt at the bottom of the steel cladding, fill the steel cladding with the alumina / copper powder obtained in S4 and compact it, then cover the surface of the alumina / copper powder with the heat insulation felt and seal the top cover. The bottom and top of the steel cladding are each connected to a vacuum pipe. Close the bottom vacuum pipe and use the top vacuum pipe to evacuate the interior of the steel cladding to a high vacuum.

[0016] S6: Place the steel cladding into a heating furnace, heat it to the set temperature, open the bottom exhaust pipe, introduce hydrogen gas, and simultaneously extract gas through the top exhaust pipe to reduce the alumina / copper powder inside the steel cladding online.

[0017] S7: Keep the temperature constant, close the bottom suction pipe, evacuate the inside of the steel cladding to a high vacuum through the top suction pipe, seal the bottom and top suction pipes, and perform hot isostatic pressing to obtain a dispersed copper ingot billet.

[0018] S8: Vacuum encapsulate the dispersed copper ingot obtained by hot isostatic pressing, and obtain high-density dispersed copper with low free oxygen content through hot extrusion.

[0019] Furthermore, in step S1, the aluminum content in the copper-aluminum alloy powder is 0.01–3 wt%, with the remainder being pure copper.

[0020] Furthermore, in step S2, the oxidation temperature of CuAl powder is 200–800°C.

[0021] Furthermore, in step S3, the amount of copper oxide added is calculated to be 1 to 3 times the amount of oxygen required for the complete oxidation of Al, and the internal oxidation temperature is 700 to 1000°C.

[0022] Furthermore, in step S4, the reduction temperature is 700–1000°C, and the holding time is 2–8 hours.

[0023] Furthermore, in step S5, the air extraction pipes at the bottom and top of the steel cladding are made of steel pipes with an inner diameter of 1-10 mm and a length of 1-5 meters.

[0024] Furthermore, in step S6, the flow rate of the high-purity hydrogen is 0.1–10 L / min, the reduction temperature is 700–900 °C, and the reduction time is 5–10 hours; and the reduction temperature is not higher than 900 °C.

[0025] Furthermore, in step S7, the temperature of hot isostatic pressing is 800–1000°C, the pressure is 50–200 MPa, and the holding time is 2–6 hours.

[0026] Furthermore, in step S8, the steel sleeve on the surface of the hot isostatically pressed dispersed copper ingot blank is removed first, and then vacuum sealed; the hot extrusion temperature is 800~1000℃, and the extrusion ratio is ≥10:1.

[0027] Furthermore, in step S5, the heat insulation felt is laid on both the bottom of the steel cladding and the surface of the alumina / copper powder. The heat insulation felt is made of alumina fiber, aluminum silicate fiber or aerogel, and the heat insulation felt has through holes with a diameter of 1 to 5 mm.

[0028] Compared with existing technologies, the preparation method of high-density, low-free-oxygen-content dispersed copper of the present invention has the following advantages:

[0029] 1. This invention uses copper-aluminum powder oxidized as an oxygen source. After the oxygen source is reduced, aluminum oxide is still dispersed inside, which solves the problem of soft phase being generated inside dispersed copper when copper oxide is used as an oxygen source, and improves the uniformity of the dispersed phase distribution.

[0030] 2. This invention utilizes a steel liner designed for simultaneous reduction and vacuuming. The liner has insulating felt at both the bottom and top to prevent overheating of the gas leaving the liner, particularly the danger posed by overheated hydrogen. Vacuum pipes, 1-5 meters in length, are installed at both the top and bottom of the liner to facilitate the introduction of hydrogen during heating and vacuuming. Using this device, online hydrogen reduction can be achieved, lowering the free oxygen content. Simultaneously, immediate vacuum sealing of the reduced powder prevents the introduction of oxygen later. Through these processes, the free oxygen content can be controlled to ≤20ppm.

[0031] 3. This invention uses a temperature below 900℃ during reduction to prevent the formation of closed pores in the alumina / copper powder due to sintering, thus avoiding the decrease in density caused by closed pores during hot isostatic pressing. Densification of the powder is achieved through hot isostatic pressing, followed by hot extrusion, further improving the density of the dispersed copper. This method effectively increases the density of dispersed copper, achieving a relative density of over 98%. Attached Figure Description

[0032] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0033] Figure 1 This is a schematic diagram of the steel sheath structure of the present invention.

[0034] Figure Labels

[0035] 1. Alumina / copper powder; 2. Evacuation pipe; 3. Valve; 4. Steel sheath; 5. Insulation felt; 6. Hydrogen; 7. Heating furnace. Detailed Implementation

[0036] To make the technical means and objectives and effects of the present invention easier to understand, the embodiments of the present invention will be described in detail below with reference to specific illustrations.

[0037] It should be noted that all directional and positional terms used in this invention, such as "up," "down," "left," "right," "front," "back," "vertical," "horizontal," "inner," "outer," "top," "lower," "lateral," "longitudinal," and "center," are only used to explain the relative positional relationships and connections between components in a specific state. They are merely for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. Furthermore, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0038] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0039] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0040] like Figure 1 As shown, this invention provides a method for preparing high-density, low-free-oxygen-content dispersed copper. Through a series of innovative process steps, it solves the technical problem of "hydrogen sickness" and insufficient density caused by the reintroduction of free oxygen due to the exposure of the reduced material to the environment, without introducing solid reducing agents or foreign elements. This method is particularly suitable for applications such as nuclear fusion reactor divertors, which have extremely stringent requirements for material purity, vacuum performance, and hydrogen expansion rate.

[0041] Specifically, the following steps are included:

[0042] S1: Copper-aluminum alloy powder is prepared by water atomization or gas atomization. High-purity electrolytic copper and pure aluminum are used as raw materials and melted into copper-aluminum alloy according to a set ratio. Then, water atomization or gas atomization technology is used to break the molten alloy into fine powder and sieve it to the required particle size.

[0043] This setup produces initial copper-aluminum alloy powder with uniform composition, good sphericity, and low oxygen content, providing high-quality raw materials for subsequent oxidation and internal oxidation reactions. Atomization offers high powder production efficiency, controllable powder particle size, and good spherical powder flowability, which facilitates uniform filling and compaction during subsequent packaging, reducing porosity. Water atomization is less expensive, while gas atomization yields even purer powder.

[0044] S2: Take a portion of the copper-aluminum alloy powder from step S1 and oxidize it into copper oxide in an oxygen atmosphere; take a portion of the copper-aluminum alloy powder obtained in step S1, introduce oxygen into a tube furnace or box furnace, and keep it at a set temperature for several hours to completely oxidize it into copper oxide, which will then serve as an external oxygen source for subsequent internal oxidation.

[0045] This setup produces pure, controllable copper oxide powder as a precise oxygen supplier. Traditional processes use pure copper oxide as the oxygen supplier; after internal oxidation-reduction, the copper oxide becomes pure copper, lacking a dispersed strengthening phase and becoming a soft phase in dispersed copper, affecting its strength. This invention uses oxidized copper-aluminum alloy powder as the oxygen supplier. After internal oxidation-reduction, the copper-aluminum alloy powder still contains alumina dispersed phase, thus improving the uniformity of the alumina dispersed phase distribution, avoiding soft phase formation, and enhancing the strength of the dispersed copper.

[0046] S3: Mix the remaining copper-aluminum alloy powder with the copper oxide obtained in step S2 in a specific ratio, and then perform internal oxidation. Mix the unoxidized remaining copper-aluminum alloy powder with the copper oxide powder obtained in step S2 in a calculated ratio using ball milling or mechanical mixing to ensure uniform mixing. Place the mixed powder in a vacuum furnace and heat it to 700–1000°C under nitrogen or an inert atmosphere, holding for 1–5 hours to perform internal oxidation treatment.

[0047] At high temperatures, the oxygen provided by the decomposition of copper oxide reacts with the aluminum in the copper-aluminum alloy powder to generate dispersed Al2O3 nanoparticles. This process avoids the problems of inaccurate oxygen distribution and uneven oxidation caused by traditional whole-powder surface oxidation; the internal oxidation reaction takes place inside the powder, resulting in fine and uniformly distributed Al2O3 particles with a significant strengthening effect.

[0048] S4: The internally oxidized powder is crushed, then reduced and crushed again to obtain alumina / copper powder 1. The internally oxidized material is usually in the form of lumps or agglomerates, which need to be crushed first, such as by ball milling or crushing into fine powder. Then the crushed powder is reduced at 700-1000℃ for 2-8 hours in a hydrogen atmosphere to remove any possible surface oxides. After reduction, it is crushed again to obtain loose and uniform alumina / copper composite powder.

[0049] The lumpy material is deagglomerated to obtain a fine powder suitable for packaging; reduction with hydrogen 6 ensures that the powder surface is in a low oxidation state, creating favorable conditions for subsequent online reduction. This setting ensures good powder flowability, which is beneficial for compaction during packaging; pre-reduction reduces the burden on subsequent online reduction and improves process stability.

[0050] Preferably, crushing can be carried out using a ball mill or a crusher.

[0051] S5: Lay heat insulation felt 5 at the bottom of the steel bladder 4, fill the steel bladder 4 with the alumina / copper powder 1 obtained in S4 and compact it. After covering the surface of the alumina / copper powder 1 with heat insulation felt 5, seal the top cover. The bottom and top of the steel bladder 4 are each connected to a vacuum pipe 2. Close the bottom vacuum pipe 2 and evacuate the inside of the steel bladder 4 to a high vacuum through the top vacuum pipe 2. Fill the specially made low-carbon steel bladder 4 with the alumina / copper powder 1. Weld a stainless steel inlet pipe to the bottom of the bladder and a stainless steel vacuum pipe 2 to the top. Place the bladder containing the powder on a vibration platform and vibrate it while simultaneously tapping the bladder wall to ensure the powder is tightly packed. Close the bottom vacuum pipe 2 and evacuate the inside of the steel bladder 4 to a high vacuum through the top vacuum pipe 2.

[0052] Specifically, heat insulation felt 5 is laid on the bottom of the steel cladding 4 and the surface of the alumina / copper powder 1, and the heat insulation felt 5 has through holes with a diameter of 1-5 mm. During online reduction and immediate encapsulation in the heating furnace 7, the furnace temperature reaches 700-900℃. The air inlet pipe at the bottom and the exhaust pipe 2 at the top of the steel cladding 4 operate at this high temperature for extended periods, and their welded joints are prone to deformation, leakage, or even rupture due to thermal stress concentration or material degradation. Laying heat insulation felt 5 at the bottom of the steel cladding 4 forms an effective thermal barrier between the high-temperature furnace and the pipe joint, significantly reducing the temperature gradient and heat load in the joint area, protecting the welded joint, and improving the overall system's sealing and safety.

[0053] S6: Place the steel ladle 4 into the heating furnace 7, and introduce high-purity hydrogen gas 6 through the bottom extraction pipe 2 while simultaneously evacuating gas through the top extraction pipe 2 to reduce the alumina / copper powder 1 inside the steel ladle 4 online. Place the assembled workpiece into the resistance furnace and connect the gas pipeline. Start the vacuum pump, evacuate gas through the top extraction pipe 2, and simultaneously introduce high-purity hydrogen gas 6 (≥99.999%) through the bottom inlet pipe. Raise the furnace temperature to the set temperature, which should not exceed 900℃, and maintain it for a period of time to allow the hydrogen gas 6 to flow through the entire powder bed, completing the reduction.

[0054] Within a closed system, flowing hydrogen gas 6 is used to fully reduce the powder, and the generated water vapor is promptly carried away to ensure complete reduction. The dynamically flowing hydrogen gas 6 ensures the sufficiency and uniformity of the reduction reaction; low-temperature reduction prevents premature sintering of the powder, preserving its porosity and creating conditions for subsequent hot isostatic pressing to achieve high density; the entire reduction process is completed within a closed system, avoiding environmental oxygen pollution.

[0055] S7: Keep the temperature constant, close the bottom evacuation pipe 2, and evacuate the inside of the steel cladding 4 to a high vacuum through the top evacuation pipe 2. Then, seal the bottom and top evacuation pipes 2 and perform hot isostatic pressing to obtain a dispersed copper ingot billet. After reduction, keep the furnace temperature constant, first close the bottom inlet pipe, and then evacuate the inside of the cladding to 10°C through the top evacuation pipe 2. -3 ~10 -5 A high vacuum of Pa was applied, and the top evacuation pipe 2 was quickly sealed to complete the immediate vacuum sealing. Subsequently, the sealed casing was sent to a hot isostatic pressing (HIP) device and held at a set temperature and pressure for densification.

[0056] The material is permanently sealed in a low-oxygen environment, and internal pores are eliminated through hot isostatic pressing (HIP) to obtain a high-density billet. This setup completely isolates the reduced material from external contact, permanently locking the free oxygen content at an extremely low level of ≤20ppm, fundamentally solving the "hydrogen poisoning" problem. HIP can achieve complete densification at lower temperatures, obtaining high-quality billets with a relative density of ≥98%.

[0057] S8: The dispersed copper ingot obtained by hot isostatic pressing is vacuum-sealed, and high-density dispersed copper with low free oxygen content is obtained by hot extrusion. After removing the steel sleeve on the surface of the ingot after hot isostatic pressing, it is vacuum-sealed again, and then hot extruded to finally obtain the final products such as bars, tubes or plates. The dispersed copper prepared has a relative density ≥98% and a free oxygen content ≤20ppm.

[0058] Hot extrusion further improves the microstructure and properties of the material, enabling the final product to be formed. The vacuum enclosure ensures that the material is not oxidized during hot processing; hot extrusion refines the grains, improving the material's strength and plasticity. The final product simultaneously possesses high density and ultra-low free oxygen content, meeting the demands of high-end applications.

[0059] Testing revealed that the free oxygen content of the dispersed copper material prepared in this embodiment was 11 ppm, which fully meets the purity requirements of nuclear fusion devices and exhibits excellent resistance to hydrogen expansion.

[0060] Specifically, in step S1, the aluminum content in the copper-aluminum alloy powder is 0.01-3 wt%, and the particle size of the copper-aluminum alloy powder is 80 mesh.

[0061] The aluminum content is 0.01–3 wt%, a range that has been validated through extensive experiments to determine the optimal solution. When the aluminum content is below 0.01 wt%, the amount of dispersed Al2O3 phase generated is insufficient, resulting in a lack of significant strengthening effect. When the aluminum content is above 3 wt%, the internal oxidation reaction is intense, easily leading to powder agglomeration, and excessive Al2O3 may become a crack initiation point, affecting the material's plasticity and density. Within this preferred range, sufficient dispersion strengthening effect is ensured while maintaining good processability and comprehensive mechanical properties.

[0062] The particle size of 80 mesh offers the following advantages: First, the medium-sized powder has good flowability, facilitating uniform packing and efficient compaction in step S5, reducing segregation and voids during packing; second, the powder of this size has a moderate specific surface area, resulting in a balanced reaction rate during oxidation in steps S2 and S3, which is beneficial for uniform oxygen diffusion and uniform Al2O3 precipitation; finally, the powder of this size range, after being crushed in step S4, can be directly used for packing without additional fine grinding, simplifying the process.

[0063] Specifically, in step S2, 1% to 36% of copper-aluminum alloy powder is taken.

[0064] Oxidizing 1% to 36% of the total powder to CuO ensures that the number of oxygen atoms provided far exceeds the theoretical value required for the complete oxidation of aluminum by 1 to 3 times. This setting guarantees that the internal oxidation reaction can proceed fully and thoroughly, avoiding the problem of incomplete Al2O3 precipitation due to insufficient oxygen source. At this ratio, copper oxide particles are uniformly distributed in the unoxidized copper-aluminum alloy powder. During the internal oxidation process, the diffusion path of oxygen from CuO particles to adjacent copper-aluminum alloy powder is short and efficient, significantly shortening the internal oxidation time and improving production efficiency. If the proportion of powder used to prepare the oxygen source is too high, such as the number of oxygen atoms being more than 3 times the theoretical value, the heat released during internal oxidation will be concentrated, easily leading to excessively high local temperatures, causing powder agglomeration or even melting. If the proportion is too low, such as the number of oxygen atoms being less than 1 times the theoretical value, it may be necessary to add additional purchased CuO, increasing the risk of impurity introduction and resulting in uneven oxygen distribution.

[0065] Specifically, in step S2, the oxidation temperature of CuAl powder is 200–800°C.

[0066] At an initial temperature of 200℃, oxidation begins on the surface of the copper-aluminum alloy powder. The oxidation rate accelerates with increasing temperature. When the temperature reaches 800℃, the aluminum element inside the powder can also fully participate in the reaction, ensuring that the entire powder is completely transformed into copper oxide (CuO) from the surface to the core. This temperature range guarantees the thoroughness of the oxidation reaction, preventing a dense oxide film on the outer shell from hindering further internal oxidation. In an oxygen atmosphere between 200 and 800℃, copper and aluminum preferentially combine with oxygen to form CuO and Al2O3, without decomposition or volatilization. The resulting copper oxide particles are pure and highly reactive, effectively releasing oxygen atoms during subsequent internal oxidation, ensuring the uniform precipitation of the Al2O3 dispersed phase. The temperature range of 200–800℃ ensures both reaction efficiency and effectively inhibits powder sintering and agglomeration, maintaining good powder flowability.

[0067] Preferably, within this temperature range, the oxidation process can be precisely controlled by adjusting the temperature and holding time. For example, using staged heating, such as first holding at 400℃ for 2 hours, and then raising the temperature to 600℃ and holding for 2 hours, can make the oxidation reaction more uniform and complete. At the same time, it avoids energy waste and equipment damage caused by using excessively high temperatures.

[0068] Specifically, in step S3, the amount of copper oxide added is calculated as 1 to 3 times the amount of oxygen required for the complete oxidation of Al, and the internal oxidation temperature is 700 to 1000°C.

[0069] In the internal oxidation process, copper oxide (CuO) acts as an external oxygen source, decomposing at high temperatures to provide oxygen atoms (O). These oxygen atoms diffuse into the unoxidized copper-aluminum alloy powder, reacting with aluminum to form Al₂O₃. Due to potential oxygen loss in the actual reaction, adding copper oxide based on the theoretical oxygen requirement—the amount needed to oxidize all Al to Al₂O₃—can easily lead to insufficient oxygen supply, resulting in incomplete internal oxidation and some aluminum failing to form a dispersed phase. Setting the amount of copper oxide added to 1-3 times the theoretical oxygen requirement provides sufficient "oxygen potential," ensuring that all aluminum atoms can find enough oxygen atoms to react, thus achieving complete Al₂O₃ precipitation. Internal oxidation is a solid-solid phase reaction, dependent on the bulk diffusion of oxygen and aluminum atoms. Temperature is the most significant factor affecting the atomic diffusion rate. 700℃ is the minimum temperature for initiating effective diffusion, while 1000℃ is the upper limit temperature to prevent excessive softening or sintering of the powder. Within this range, atoms have sufficient kinetic energy for long-range diffusion, ensuring the internal oxidation reaction is completed within a reasonable time.

[0070] Specifically, in step S4, the reduction temperature is 700-1000℃, and the holding time is 2-8 hours.

[0071] After internal oxidation, the powder readily forms a thin oxide film, such as Cu2O or Al2O3, on its surface when exposed to air or during transfer. 700℃ is the starting temperature for the effective reduction of copper oxides by hydrogen 6, while 1000℃ is the upper limit temperature to prevent sintering of the powder in the reduction furnace. Within this temperature range, hydrogen 6 has sufficient reducing power to quickly and thoroughly reduce various oxides on the powder surface to a metallic state, ensuring a clean and highly reactive powder surface. The reduction reaction requires a certain amount of time to complete, especially for batch processing of powders, where sufficient time is needed for hydrogen 6 to penetrate into the powder pile, ensuring that the surface of all powder particles is fully reduced. Two hours is the minimum time to ensure basic removal of surface oxides, while eight hours ensures complete reaction under various charge densities and powder characteristics.

[0072] The holding time can be flexibly adjusted according to the degree of oxidation of the powder, the amount of material, and the flow of hydrogen in the reduction furnace. For powders with a small amount of copper oxide or small batch processing, a shorter time, such as 2 to 4 hours, can be used; for powders with a large amount of copper oxide or large batch processing, it needs to be extended to 6 to 8 hours to ensure uniform reduction.

[0073] Specifically, in step S5, the bottom and top suction pipes 2 of the steel sleeve 4 are made of steel pipes with an inner diameter of 1-10 mm and a length of 1-5 meters. The bottom suction pipe 2 is closed, and the cylinder liner is evacuated to a high vacuum through the top suction pipe 2.

[0074] The bottom steel pipe serves as the air inlet pipe, used to introduce high-purity hydrogen gas 6; the top steel pipe serves as the exhaust pipe 2, used to connect to a vacuum pump for evacuation. This bottom-inlet and top-extraction design creates a dynamic airflow from bottom to top inside the steel bladder 4, ensuring that hydrogen gas 6 can flow evenly and continuously through the entire powder bed, effectively carrying away the water vapor generated by the reduction reaction, preventing its local accumulation from affecting the reduction effect, and realizing online flow reduction.

[0075] The two steel pipes are designed to be 1-5 meters long, allowing the pipe joints to extend outside the heating furnace 7. After the powder has been reduced at high temperature, the operator can safely and conveniently perform the sealing operation outside the furnace. First, the bottom gas inlet pipe is sealed to cut off the hydrogen source, and then a high vacuum is performed inside the casing through the top evacuation pipe 2, with a vacuum level of 10. -3 ~10 -5 Pa, and finally, the top extraction pipe 2 is quickly sealed. The entire process is completed while maintaining a high system temperature, sealing the material in a low-oxygen environment, completely solving the re-oxidation problem caused by cooling and transfer in traditional processes. The inner diameter of 1-10mm ensures both smooth gas flow and maintains the overall rigidity of the casing.

[0076] Preferably, the steel pipe is a stainless steel pipe.

[0077] Preferably, the wall thickness of the steel sleeve 4 is 2-5 mm.

[0078] Specifically, heat insulation felt 5 is laid on the bottom of the steel sleeve 4 and the surface of the alumina / copper powder 1. The heat insulation felt 5 is one or more of alumina fiber, aluminum silicate fiber or aerogel, and the heat insulation felt 5 has through holes with a diameter of 1 to 5 mm.

[0079] During online reduction and immediate encapsulation in the heating furnace 7, the furnace temperature reaches 700–900℃. The inlet pipe at the bottom and the exhaust pipe 2 at the top of the steel cladding 4 operate at this high temperature for extended periods, making their welded joints prone to deformation, leakage, or even rupture due to thermal stress concentration or material degradation. Laying an insulating felt 5 at the bottom of the steel cladding 4 forms an effective thermal barrier between the high-temperature furnace and the pipe joints, significantly reducing the temperature gradient and heat load in the joint area, protecting the welded joints, and improving the overall system's sealing and safety. Laying the insulating felt 5 on the surface of the alumina / copper powder 1, near the top exhaust pipe 2, provides insulation, reducing heat loss upwards through the top pipe, thereby improving the axial temperature uniformity of the powder bed and ensuring the reduction reaction proceeds synchronously and uniformly throughout the entire powder volume. The 1–5 mm through-holes ensure smooth passage of hydrogen 6 and water vapor, maintaining the dynamic airflow pattern of "bottom inlet, top exhaust," while effectively preventing powder particles from migrating upwards or splashing into the exhaust pipe 2 and causing blockage.

[0080] Preferably, the thickness of the heat insulation felt 5 is 5 to 20 mm.

[0081] Specifically, in step S6, the flow rate of high-purity hydrogen 6 is 0.1–10 L / min, the reduction temperature is 700–900 °C, and the reduction time is 5–10 hours; and the reduction temperature is not higher than 900 °C.

[0082] Hydrogen 6 acts as a reducing agent, reacting with residual oxides on the surface of the alumina / copper powder 1 within the steel sheath 4. 0.1 L / min is the minimum flow rate threshold for maintaining effective gas flow and ensuring the continuous removal of water vapor generated during the reaction; 10 L / min is the upper limit to prevent excessive gas flow from causing powder fluidization, pressure fluctuations within the sheath, or wasting hydrogen 6. Within this flow rate range, a stable and uniform bottom-up airflow can be formed, ensuring sufficient contact between hydrogen 6 and the powder, achieving a thorough reduction reaction. Hydrogen 6 is a flammable and explosive gas; controlling the flow rate within a reasonable range can effectively reduce safety risks. Simultaneously, avoiding excessive use of high-purity hydrogen 6 (≥99.999%) helps reduce production costs.

[0083] 700℃ is the activation temperature at which hydrogen 6 begins to effectively reduce copper and aluminum oxides. Below this temperature, the reaction rate is extremely low, making it difficult to complete the reduction within a reasonable time. 900℃ is the maximum temperature limit set by the process of this invention. Within this temperature range, the atomic diffusion ability is moderate, and the reduction reaction can proceed steadily at a controllable rate. Strictly controlling the reduction temperature to no higher than 900℃ can effectively suppress the sintering behavior of the powder, ensure that hydrogen 6 is fully combined with the powder, and maintain its loose, porous original state after reduction, avoiding the formation of closed pores, ensuring a vacuum environment for the powder, and providing unobstructed channels for pore closure and material migration during the HIP process.

[0084] A longer holding time of 5 to 10 hours helps to eliminate temperature gradients and hydrogen concentration differences in different areas within the packaging, ensuring that the reduction reaction proceeds uniformly throughout the powder bed and avoiding localized under-reduction or over-reduction.

[0085] Specifically, in step S7, the temperature of hot isostatic pressing is 800-1000℃, the pressure is 50-200MPa, and the holding time is 2-6 hours.

[0086] 800℃ is the starting temperature at which significant creep and diffusion begin in a copper matrix; below this temperature, the densification rate is extremely slow. 1000℃ is the upper limit temperature to prevent excessive grain growth and material performance degradation. Within this temperature range, atoms have sufficient mobility to promote the closure and elimination of pores through grain boundary diffusion, bulk diffusion, and dislocation movement.

[0087] 50 MPa is the minimum pressure required to effectively eliminate micropores; below this pressure, complete densification is difficult to achieve. 200 MPa is a reasonable upper limit that the equipment capacity and material strength can withstand. Within this pressure range, isostatic pressing can uniformly compress the powder compact from all directions, causing the internal pores to close uniformly under isotropic pressure. For compacts with high porosity, higher pressures, such as 150–200 MPa, can be used to accelerate the densification process; for compacts with high packing density or partially pre-sintered compacts, lower pressures, such as 50–100 MPa, can achieve the densification requirements. This pressure range provides good process flexibility.

[0088] The production cycle time is 2 to 6 hours, which balances production speed and cost control while ensuring a density of ≥98%.

[0089] Specifically, in step S8, the steel sleeve on the surface of the hot isostatically pressed copper ingot blank is first removed, and then vacuum sealed; the hot extrusion temperature is 800-1000℃, and the extrusion ratio is ≥10:1.

[0090] After hot isostatic pressing, the low-carbon steel sheath 4 surrounding the ingot must be completely removed mechanically, such as by turning, grinding, or pickling, to expose the surface of the dispersed copper ingot. To prevent the copper matrix from reacting with oxygen in the air during the hot extrusion heating process, the ingot must be re-vacuum-sealed after removing the sheath. The ingot is then placed into a new, clean low-carbon steel or stainless steel sheath 4 and evacuated to 10... -3 ~10 -5 High-vacuum post-sealing at Pa. This operation continues the low-oxygen environment protection strategy, ensuring that the material remains isolated from the external atmosphere throughout the entire thermal processing chain, effectively preventing the reintroduction of free oxygen and maintaining an ultra-low oxygen level of ≤20ppm. The vacuum sealing not only prevents oxidation but also inhibits the reopening of pores during extrusion, improving the surface quality and internal density of the finished product. Matching the thermal stability of dispersion-strengthened copper within the aforementioned temperature range, it achieves sufficient hot deformation without causing decomposition of the Al2O3 phase or excessive softening of the matrix.

[0091] A high extrusion ratio greater than 10:1 signifies that the material has undergone plastic processing with a large amount of deformation, effectively eliminating residual micro-defects such as micropores and porosity, further improving the material's density and microstructure uniformity. The high-density dislocations and grain refinement effect introduced by large-deformation extrusion can significantly improve the material's strength and hardness, while maintaining good plasticity through dynamic recrystallization, thus enhancing the material's overall service performance.

[0092] Preferably, after hot isostatic pressing is completed, the furnace is cooled to room temperature.

[0093] Example 1

[0094] A method for preparing high-density, low-free-oxygen-content dispersed copper, comprising the following steps:

[0095] Copper-aluminum powder with an aluminum content of 0.52 wt% and a particle size of -80 mesh was prepared by gas atomization. 2 kg of copper-aluminum powder was reacted at 500°C for 2 hours in an oxygen atmosphere until it turned into copper oxide.

[0096] Take 50 kg of the above copper-aluminum powder and 2 kg of the above copper oxide powder, mix them evenly, put them into a vacuum furnace, evacuate the vacuum and introduce nitrogen gas, heat to 800℃, keep at the temperature for 5 hours, and cool to room temperature.

[0097] After the obtained powder is crushed, it is placed in a reduction furnace, hydrogen gas 6 is introduced, and it is heated to 930°C for reduction and crushing to obtain alumina / copper powder.

[0098] A steel sleeve 4 with an inner diameter of φ150mm and a thickness of 3mm is fabricated. The bottom cover of the steel sleeve 4 is sealed and welded, and a bottom evacuation pipe 2, made of stainless steel with an inner diameter of φ8mm and a length of 3 meters, is welded onto the bottom cover. Alumina fiber felt with several φ5mm through holes is laid at the bottom of the steel sleeve 4 to facilitate gas passage. The alumina / copper powder obtained in step four is loaded into the steel sleeve 4. After compaction on a vibrating platform, the same alumina fiber felt as the bottom is laid on top to prevent the gas leaving the steel sleeve 4 from overheating during reduction and high-temperature evacuation, which could damage the evacuation port or vacuum pump. The top cover is sealed and welded, and an evacuation pipe 2, made of stainless steel and the same size as the bottom evacuation pipe 2, is welded onto the top cover. The bottom evacuation pipe 2 is connected to the hydrogen gas line 6, and the top evacuation pipe 2 is connected to the vacuum pump. The hydrogen gas line 6 is closed, the vacuum pump is turned on, and a vacuum is evacuated to 10°C. -4 Pa.

[0099] Open the hydrogen gas pipeline 6 and introduce hydrogen gas 6 at a flow rate of 0.8 L / min. Maintain evacuation through the top evacuation pipe 2. Place the steel ladle sleeve 4 into the resistance furnace, with the top and bottom evacuation pipes 2 positioned outside the furnace. Heat to 850°C and reduce for 6 hours. During reduction at 850°C, the alumina / copper powder will not sinter, and closed pores will not form internally, thus avoiding the density decrease caused by closed pores during hot isostatic pressing.

[0100] Shut off hydrogen gas 6, maintain 850℃, seal the bottom of the steel ladle sleeve 4 with the vacuum pipe 2, and continue evacuating the vacuum using the top vacuum pipe 2 until it reaches 10℃. -4 After Pa, the top extraction pipe 2 is sealed and welded, and hot isostatic pressing is performed at a temperature of 900℃, a pressure of 100MPa, and a holding time of 4 hours to obtain a dispersed copper ingot billet.

[0101] Remove the steel cladding 4 from the surface of the dispersed copper ingot, place it in a copper cladding, evacuate to 10⁻⁴ Pa and then seal it. Hot extrusion is carried out at 880℃ with an extrusion ratio of 20:1 to obtain dispersed copper with high density and low free oxygen content.

[0102] The obtained dispersed copper had a relative density of 98.2% and a free oxygen content of 11 ppm.

[0103] Example 2

[0104] A method for preparing high-density, low-free-oxygen-content dispersed copper, comprising the following steps:

[0105] The alumina / copper powder obtained in Example 1 was placed in a steel liner 4 and evacuated to 10°C. -4 After sealing, the copper was subjected to hot isostatic pressing and hot extrusion according to the method in Example 1, and the resulting dispersed copper had a relative density of 97.6% and a free oxygen content of 68 ppm.

[0106] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing high-density, low-free-oxygen-content dispersed copper, characterized in that, Includes the following steps: S1: Copper-aluminum alloy powder is prepared by water atomization or gas atomization. S2: Take a portion of the copper-aluminum alloy powder from step S1 and oxidize it into copper oxide in an oxygen atmosphere; S3: Mix the remaining copper-aluminum alloy powder with the copper oxide obtained in step S2 in a certain proportion, and then perform internal oxidation. S4: The powder after internal oxidation is crushed, then reduced and crushed again to obtain aluminum oxide / copper powder (1). S5: Lay heat insulation felt (5) at the bottom of the steel sleeve (4), put the alumina / copper powder (1) obtained in step S4 into the steel sleeve (4) and compact it. After the heat insulation felt (5) is laid on the surface of the alumina / copper powder (1), seal the top cover. The bottom and top of the steel sleeve (4) are each connected to a vacuum pipe (2). Close the vacuum pipe (2) at the bottom and use the vacuum pipe (2) at the top to evacuate the inside of the steel sleeve (4) to a high vacuum. S6: Place the steel cladding (4) into the heating furnace (7), heat it to the set temperature, open the bottom exhaust pipe (2), introduce hydrogen (6), and at the same time exhaust the gas through the top exhaust pipe (2) to reduce the alumina / copper powder (1) in the steel cladding (4) online. S7: Keep the temperature constant, close the bottom suction pipe (2), and evacuate the inside of the steel cladding (4) to a high vacuum through the top suction pipe (2). Then seal the bottom and top suction pipes (2) and perform hot isostatic pressing to obtain a dispersed copper ingot blank. S8: Vacuum encapsulate the dispersed copper ingot obtained by hot isostatic pressing, and obtain high-density dispersed copper with low free oxygen content through hot extrusion.

2. The method for preparing high-density, low-free-oxygen-content dispersed copper according to claim 1, characterized in that, In step S1, the aluminum content in the copper-aluminum alloy powder is 0.01-3 wt%, and the remainder is pure copper.

3. The method for preparing high-density, low-free-oxygen-content dispersed copper according to claim 2, characterized in that, In step S2, the oxidation temperature of CuAl powder is 200–800℃.

4. The method for preparing high-density, low-free-oxygen-content dispersed copper according to claim 1, characterized in that, In step S3, the amount of copper oxide added is calculated as 1 to 3 times the amount of oxygen required for the complete oxidation of Al, and the internal oxidation temperature is 700 to 1000℃.

5. The method for preparing high-density, low-free-oxygen-content dispersed copper according to claim 4, characterized in that, In step S4, the reduction temperature is 700–1000℃, and the holding time is 2–8 hours.

6. The method for preparing high-density, low-free-oxygen-content dispersed copper according to claim 5, characterized in that, In step S5, the suction pipes (2) at the bottom and top of the steel sheath (4) are made of steel pipes with an inner diameter of 1 to 10 mm and a length of 1 to 5 meters.

7. The method for preparing high-density, low-free-oxygen-content dispersed copper according to claim 1, characterized in that, In step S6, the flow rate of the high-purity hydrogen (6) is 0.1 to 10 L / min, the reduction temperature is 700 to 900°C, and the reduction time is 5 to 10 hours; and the reduction temperature is not higher than 900°C.

8. The method for preparing high-density, low-free-oxygen-content dispersed copper according to claim 1, characterized in that, In step S7, the temperature of hot isostatic pressing is 800-1000℃, the pressure is 50-200MPa, and the holding time is 2-6 hours.

9. The method for preparing high-density, low-free-oxygen-content dispersed copper according to claim 1, characterized in that, In step S8, the steel sleeve on the surface of the hot isostatically pressed copper ingot is first removed, and then vacuum sealed; the hot extrusion temperature is 800-1000℃, and the extrusion ratio is ≥10:

1.

10. The method for preparing high-density, low-free-oxygen-content dispersed copper according to claim 1, characterized in that, In step S5, the heat insulation felt (5) is laid on the bottom of the steel sleeve (4) and the surface of the alumina / copper powder (1). The heat insulation felt (5) is made of alumina fiber, aluminum silicate fiber or aerogel, and the heat insulation felt (5) has through holes with a diameter of 1 to 5 mm.

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