A method for producing aluminum oxide dispersed copper

Abstract

The application belongs to the technical field of powder metallurgy, and particularly relates to a preparation method of aluminum oxide dispersed copper, which comprises the following steps: mixing copper-aluminum alloy and cuprous oxide, performing primary internal oxidation to generate a partially internally oxidized sintered blank; performing hot deformation treatment on the partially internally oxidized sintered blank; and performing secondary internal oxidation on the partially internally oxidized sintered blank subjected to the hot deformation treatment to generate a completely internally oxidized sintered blank. Thus, in the primary internal oxidation process, the aluminum atoms in the copper-aluminum alloy can not be completely internally oxidized, and then the sintered blank is subjected to hot deformation treatment to improve the density. Since the deformation resistance of the partially internally oxidized sintered blank is relatively small, the deformation difficulty is relatively low, and the sintered blank is not easy to be extruded and cracked during extrusion, the hot extrusion performance can be improved. After the hot extrusion is completed, the secondary internal oxidation is performed again, so that the Cu-Al in the sintered blank is completely converted into Cu-Al2O3, and the comprehensive performance of the sintered blank is improved. The method can solve the problem of difficult hot deformation of the dispersed copper sintered blank, and improve the yield of the final product.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy technology, and specifically relates to a method for preparing alumina-dispersed copper. Background Technology

[0002] Alumina-dispersed copper (also known as alumina-dispersed reinforced copper, hereinafter referred to as dispersed copper) relies on composite strengthening methods to generate nanoscale alumina-reinforced phases in situ within the copper matrix. While maintaining excellent conductivity, it can achieve breakthroughs in high-temperature performance, making it the copper-based material with the best high-temperature mechanical properties to date.

[0003] The existing method for preparing alumina-dispersed copper involves a complete internal oxidation process. Using a copper-aluminum alloy as the initial powder, an oxygen source is introduced, and the Cu-Al alloy within the material is completely converted into a Cu-Al₂O₃ billet (i.e., a dispersed copper sintered billet) using the principle of internal oxidation. Subsequently, the Cu-Al₂O₃ billet is hot-extruded to increase its density. Hot extrusion compresses the internal pores, improving the billet's density. The amount of deformation during hot extrusion is positively correlated with the increase in density; the greater the deformation, the greater the increase in density. However, while the Al₂O₃ particles in the Cu-Al₂O₃ billet provide good reinforcement to the Cu matrix, they also lead to high deformation resistance, poor plasticity, and susceptibility to cracking in the dispersed copper sintered billet. In other words, the dispersed copper sintered billet faces difficulties in hot extrusion, cracking even with limited deformation, resulting in a low yield of the final product. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing alumina-dispersed copper to solve the problem of poor hot extrusion performance of dispersed copper sintered billets.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for preparing alumina-dispersed copper includes: mixing a copper-aluminum alloy and cuprous oxide, performing a first internal oxidation to generate a partially internally oxidized sintered blank; performing a hot deformation treatment on the partially internally oxidized sintered blank; and performing a second internal oxidation on the partially internally oxidized sintered blank after the hot deformation treatment to generate a fully internally oxidized sintered blank.

[0007] In this invention, during a single internal oxidation process, aluminum atoms in the copper-aluminum alloy are not completely oxidized. The partially internally oxidized sintered billet comprises Cu-Al and Cu-Al₂O₃. The billet is then subjected to hot deformation to increase density. Because the deformation resistance of the partially internally oxidized sintered billet is lower than that of the fully internally oxidized sintered billet in existing methods, deformation is less difficult, and it is less prone to cracking during extrusion, reducing deformation force and improving hot extrusion performance. After hot extrusion, a second internal oxidation process is performed to completely convert Cu-Al in the sintered billet to Cu-Al₂O₃, further improving the overall performance of the sintered billet. This invention solves the problem of difficult hot deformation of dispersed copper sintered billets and improves the yield of products prepared using this method.

[0008] Compared to traditional methods, the method of this invention allows for milder conditions in the hot deformation process. For example, in existing methods, hot deformation of a fully internally oxidized sintered billet with a diameter of 80mm requires a 1200-ton extruder. With the method of this invention, due to the lower deformation resistance of partially oxidized sintered billets, a 500-ton extruder can be used, reducing equipment requirements and achieving low-carbon environmental protection. Furthermore, existing methods can only use extrusion molding for hot deformation, resulting in low product yield and ultimately low final product yield. The hot deformation process of the method of this invention yields higher product yield, thus improving the final product yield. In addition, existing methods treat fully internally oxidized sintered billets, which have poor deformability and can only be formed by extrusion under triaxial compressive stress. Using other deformation processes such as hot forging can easily lead to cracking. With the method of this invention, due to the improved deformability and reduced deformation resistance of partially oxidized sintered billets, hot deformation can be performed using methods including but not limited to hot forging, expanding the hot deformation process.

[0009] Furthermore, after mixing the copper-aluminum alloy and cuprous oxide, the method further includes: compacting the mixed powder of copper-aluminum alloy and cuprous oxide using a cold isostatic press, followed by an internal oxidation.

[0010] As a further improvement, the temperature of the first internal oxidation is 850-900℃, and the time of the first internal oxidation is 1-1.5h. Therefore, under the above-mentioned temperature and time conditions for the first internal oxidation, metallurgical bonding can be ensured within the material, while reducing the decomposition of cuprous oxide and the diffusion of oxygen within the copper matrix. This results in incomplete internal oxidation of aluminum atoms in the copper-aluminum alloy, ensuring that the sintered billet contains both copper-aluminum alloy and a small amount of alumina, thus reducing the amount of alumina generated. Since the deformability of copper-aluminum alloy is superior to that of Cu-Al2O3 material, the product obtained after the first internal oxidation has a lower alumina content and lower deformation resistance, which is beneficial for further improving hot extrusion performance and facilitating hot extrusion forming.

[0011] Furthermore, the primary internal oxidation is carried out under the protection of an inert gas, the pressure of which can be 3 atm. The inert gas includes nitrogen.

[0012] As a further improvement, the temperature of the secondary internal oxidation is 900-910℃, and the time of the secondary internal oxidation is 2-3 hours. Under these conditions, the sintered billet can undergo sufficient internal oxidation, causing all remaining aluminum atoms in the sintered billet to be oxidized into alumina, thereby improving the overall performance of alumina-dispersed copper.

[0013] As a further improvement, the hot deformation treatment includes hot extrusion at a temperature of 900-910°C. This hot extrusion achieves densification. Since the product obtained after a single internal oxidation step has a lower alumina content and lower deformation resistance, the yield of this step is higher, which in turn can further improve the yield of the final product.

[0014] Furthermore, the hot deformation treatment includes hot forging deformation or hot extrusion deformation.

[0015] As a further improvement, the oxidation degree of the partially oxidized sintered billet is 10%-90%, wherein the oxidation degree of the partially oxidized sintered billet refers to the percentage of aluminum atom content corresponding to Al2O3 in the partially oxidized sintered billet to the aluminum atom content in the copper-aluminum alloy, and the aluminum atom content refers to the molar amount, mass or volume fraction of aluminum atoms.

[0016] The degree of oxidation of a partially internally oxidized sintered billet refers to the proportion of aluminum atoms corresponding to Al2O3 in the partially internally oxidized sintered billet to the total aluminum atom content in the copper-aluminum alloy. The degree of oxidation of the partially internally oxidized sintered billet is positively correlated with its conductivity. In this invention, the degree of oxidation of the partially internally oxidized sintered billet is determined as follows: The conductivity of the copper-aluminum alloy before internal oxidation occurs is measured, at which point the degree of internal oxidation is 0. When all the aluminum in the copper-aluminum alloy is converted to alumina, the degree of internal oxidation is 100%, resulting in a fully internally oxidized sintered billet. The conductivity of the fully internally oxidized sintered billet is measured. Based on the above data, the relationship between the degree of internal oxidation and the conductivity of the sintered billet is obtained. The conductivity of the partially internally oxidized sintered billet to be tested is measured and substituted into the above relationship to calculate the degree of oxidation of the partially internally oxidized sintered billet to be tested.

[0017] As a further improvement, the oxidation degree of the partially oxidized sintered blank is 30%-65%.

[0018] As a further improvement, after the secondary internal oxidation is completed, the method further includes: reducing the fully internally oxidized sintered billet in a hydrogen atmosphere to obtain copper alumina dispersion. This allows unreacted cuprous oxide to undergo a reduction reaction with hydrogen, reducing cuprous oxide to copper.

[0019] Furthermore, when the oxygen content in the added cuprous oxide and the aluminum content in the copper-aluminum alloy meet the stoichiometric ratio of Al2O3, the aforementioned reduction step is unnecessary. In other words, the reduction step can be adjusted based on the amount of cuprous oxide added. When the oxygen in the added cuprous oxide can completely react with the aluminum in the copper-aluminum alloy, the reduction step is not required. When an excess of cuprous oxide is added, the reduction step is necessary to remove the excess oxygen source.

[0020] Furthermore, after the secondary internal oxidation is completed, the method further includes: subjecting the fully internally oxidized sintered billet to cold deformation treatment to further improve its performance. The cold deformation treatment is cold drawing.

[0021] Furthermore, the alumina content in the alumina-dispersed copper is 0.2-1.2 wt%. Detailed Implementation

[0022] The technical solution of the present invention will be further described in detail below with reference to specific embodiments.

[0023] Existing methods produce alumina-dispersed copper with poor hot extrusion properties. To address this issue, this invention provides a method for preparing alumina-dispersed copper, comprising: mixing a copper-aluminum alloy and cuprous oxide, performing a first internal oxidation to generate a partially internally oxidized sintered blank; subjecting the partially internally oxidized sintered blank to a hot deformation treatment; and subjecting the partially internally oxidized sintered blank after the hot deformation treatment to a second internal oxidation to generate a fully internally oxidized sintered blank.

[0024] This invention involves a first internal oxidation process where aluminum atoms in the copper-aluminum alloy are not completely oxidized. The sintered billet is then subjected to hot deformation to increase density. Because the partially internally oxidized sintered billet has a lower alumina content and lower deformation resistance, its hot extrusion performance can be improved. A second internal oxidation process is then performed, causing the remaining aluminum atoms in the sintered billet to react and form alumina, further enhancing the overall performance of the sintered billet. This invention solves the problem of difficult hot deformation of dispersed copper sintered billets, improving the yield of the final product.

[0025] I. Examples of methods for preparing alumina-dispersed copper

[0026] Example 1

[0027] The method for preparing alumina-dispersed copper in this embodiment includes the following steps:

[0028] (1) Powder Mixing and Loading: Take the following raw materials: Cu-Al alloy powder produced by water mist method, with an aluminum content of 0.35wt% and a particle size of 45μm; Cu2O oxidant powder, with a particle size of 1μm and a purity ≥99.5wt%; the Cu2O content in the raw materials is 2.70wt%, and the balance is Cu-Al alloy powder; mix the Cu-Al alloy powder and Cu2O powder thoroughly in a V-type powder mixer for 3 hours to obtain a mixed powder. Load the mixed powder into a rubber sleeve for sealing, and perform cold isostatic pressing to obtain an isostatic pressed billet. Example 1: The alumina content in alumina-dispersed copper is 0.66wt%.

[0029] (2) First internal oxidation: The isostatically pressed billet is loaded into the furnace lining, nitrogen is introduced to purge the air, the nitrogen pressure is maintained at 3 atm, and the temperature is raised to carry out the first internal oxidation. The temperature of the first internal oxidation is 900℃, and the holding time is 1h. Then the temperature is lowered to obtain a partially internally oxidized sintered billet. The oxidation degree of the partially internally oxidized sintered billet is 50%.

[0030] (3) Hot extrusion: Part of the internally oxidized sintered billet is heated to 900°C and extruded on an extruder to form a shape with an extrusion ratio of 20:1.

[0031] (4) Secondary internal oxidation: After hot extrusion, the extruded bar is placed in an internal oxidation furnace, heated to 900°C, and held for 2 hours to completely convert the remaining Cu-Al alloy in the material into Cu-Al2O3 material, thus obtaining a fully internally oxidized sintered billet.

[0032] (5) Cold deformation: The rod obtained after secondary internal oxidation is cold drawn to further improve its performance. The cold drawing deformation is 50% to obtain alumina-dispersed copper.

[0033] Example 2

[0034] The method for preparing alumina-dispersed copper in this embodiment includes the following steps:

[0035] (1) Mixing powder and loading, the specific steps are the same as in Example 1.

[0036] (2) The isostatic pressing billet is loaded into the furnace chamber, nitrogen is introduced to purge the air, the nitrogen pressure is maintained at 3 atm, the temperature is raised to carry out the first internal oxidation, the temperature of the first internal oxidation is 850℃, the holding time is 1h, and then the temperature is lowered to obtain the partially internally oxidized sintered billet, the oxidation degree of the partially internally oxidized sintered billet is 30%.

[0037] (3) Hot extrusion, the specific steps are the same as in Example 1.

[0038] (4) Secondary internal oxidation, the specific steps are the same as in Example 1.

[0039] (5) Cold deformation, the specific steps are the same as in Example 1.

[0040] Example 3

[0041] The method for preparing alumina-dispersed copper in this embodiment includes the following steps:

[0042] (1) Mixing powder and loading, the specific steps are the same as in Example 1.

[0043] (2) First internal oxidation: The isostatically pressed billet is loaded into the furnace lining, nitrogen is introduced to purge the air, the nitrogen pressure is maintained at 3 atm, and the temperature is raised to carry out the first internal oxidation. The temperature of the first internal oxidation is 900℃, and the holding time is 1.5h. Then the temperature is lowered to obtain the partially internally oxidized sintered billet. The oxidation degree of the partially internally oxidized sintered billet is 65%.

[0044] (3) Hot extrusion, the specific steps are the same as in Example 1.

[0045] (4) Secondary internal oxidation, the specific steps are the same as in Example 1.

[0046] (5) Cold deformation, the specific steps are the same as in Example 1.

[0047] II. Comparative Example

[0048] Comparative Example 1

[0049] Comparative Example 1 uses a conventional fully internal oxidation process. The method for preparing alumina-dispersed copper in Comparative Example 1 includes the following steps:

[0050] (1) Powder mixing and loading: Take the following raw materials: Cu-Al alloy powder produced by water mist method, with an aluminum content of 0.35wt% and a particle size of 45μm; Cu2O oxidant powder, with a particle size of 1μm and a purity of ≥99.5wt%; the Cu2O content in the raw materials is 3.30wt%, and the balance is Cu-Al alloy powder; mix the Cu-Al alloy powder and Cu2O powder thoroughly in a V-type powder mixer for 3 hours to obtain mixed powder. Load the mixed powder into a rubber sleeve for sealing, and perform cold isostatic pressing to obtain an isostatic pressed billet.

[0051] (2) Internal oxidation, reduction, and powder sintering: The composite billet is loaded into the furnace chamber, and nitrogen is introduced to purge the air, maintaining a nitrogen pressure of 3 atm. Internal oxidation is performed at 900℃ for 2 hours. After internal oxidation, hydrogen is introduced to purge the nitrogen, maintaining a hydrogen pressure of 3 atm. Reduction is then performed under reduction process parameters at 930℃ for 2 hours. After reduction, sintering is carried out in an inert gas atmosphere (nitrogen or argon) at 950℃ for 2 hours. After sintering, the billet is cooled to obtain the sintered billet.

[0052] (3) Hot extrusion: The sintered billet is heated to 900°C and extruded on an extruder with an extrusion ratio of 20:1.

[0053] (4) Cold deformation: The bar obtained after secondary internal oxidation is cold drawn to further improve its performance. The cold drawing deformation is 50%.

[0054] III. Performance Testing

[0055] The performance of the alumina-dispersed copper prepared in Examples 1-3 and Comparative Example 1 was tested, and the test results are shown in Table 1.

[0056] The test methods were as follows: the conductivity of the sample was tested using a D60K eddy current conductivity meter, the hardness of the sample was tested using a Brinell hardness tester, and the density of the sample was tested using the water displacement method.

[0057] Table 1. Performance comparison of alumina-dispersed copper prepared in Examples 1-3 and Comparative Example 1

[0058] Comparative Example 1 82.7 138.3 99.2％ Example 1 82.5 139.7 99.1％ Example 2 81.7 138.5 99.2％ Example 3 82.3 139.1 99.3％

[0059] As can be seen from Table 1, the performance and density of the alumina-dispersed copper in Examples 1-3 are comparable to those of the product in Comparative Example 1.

[0060] In the preparation process of Examples 1-3, five parallel experiments were conducted during the hot extrusion operation, and each extrusion resulted in complete extrusion without cracking. In the preparation process of Comparative Example 1, five parallel experiments were conducted during the hot extrusion operation, with three successful extrusions, one sample cracking during extrusion, and one failure to extrude. Compared with Comparative Example 1, the method of the present invention can improve the yield of products prepared by the hot extrusion step, thereby improving the yield of the final product.

Claims

1. A method for preparing alumina-dispersed copper, characterized in that, include: A copper-aluminum alloy and cuprous oxide are mixed and subjected to a first internal oxidation process to generate a partially internally oxidized sintered billet. The internally oxidized sintered blank is subjected to hot deformation treatment; The partially internally oxidized sintered blank that has undergone the heat deformation treatment is subjected to secondary internal oxidation to generate a fully internally oxidized sintered blank. The oxidation degree of the partially oxidized sintered blank is 30%-65%; The degree of oxidation of the partially oxidized sintered billet refers to the percentage of aluminum atom content corresponding to Al2O3 in the partially oxidized sintered billet compared to the percentage of aluminum atom content in the copper-aluminum alloy.

2. The method for preparing alumina-dispersed copper according to claim 1, characterized in that, The temperature of the first internal oxidation is 850-900℃, and the time of the first internal oxidation is 1-1.5h.

3. The method for preparing alumina-dispersed copper according to claim 1, characterized in that, The temperature of the secondary internal oxidation is 900-910℃, and the time of the secondary internal oxidation is 2-3 hours.

4. The method for preparing alumina-dispersed copper according to claim 1, characterized in that, The heat deformation treatment includes hot extrusion, and the hot extrusion temperature is 900-910℃.

5. The method for preparing alumina-dispersed copper according to any one of claims 1-4, characterized in that, After the secondary internal oxidation is completed, the method further includes: reducing the fully internally oxidized sintered blank in a hydrogen atmosphere to obtain alumina-dispersed copper.