A preparation method of high-strength and high-conductivity alumina dispersion-strengthened copper

Abstract

The present invention discloses a preparation method of high-strength and high-conductivity alumina dispersion-strengthened copper, which comprises: 1. preparing an aluminum nitrate-absolute ethanol solution; 2. mixing electrolytic copper powder and the aluminum nitrate-absolute ethanol solution; 3. ball-milling and crushing the mixed powder; 4. performing reduction treatment; 5. performing spark plasma sintering after room-temperature pre-pressing, crushing and exhausting to obtain alumina dispersion-strengthened copper. By utilizing the corrosion effect of aluminum nitrate on the surface of copper powder, the present invention can effectively prevent cold welding of the powder during long-term ball milling, and can obtain composite powder with very good dispersibility. By long-term ball milling, a micro-flake copper powder-supported alumina composite powder is constructed. The large grains formed on the large surface of the micro-flake copper powder can effectively increase the electron transport channels. By adopting low-temperature and high-pressure sintering, excessive grain growth can be effectively inhibited, so that the alumina dispersion-strengthened copper has high-strength and high-conductivity properties, and the process is easy to control, which can effectively reduce the production cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal composite materials and their preparation, and particularly relates to a method for preparing high-strength and high-conductivity alumina dispersion-strengthened copper. Background Art

[0002] With the rapid development of high-tech fields such as modern aerospace, new energy vehicles, and electronic information technology, the demand for high-strength and high-conductivity copper materials is increasing day by day. Alumina dispersion-strengthened copper has excellent comprehensive properties such as mechanical, electrical, and high-temperature softening resistance, and has broad application prospects, which has attracted extensive attention from researchers.

[0003] Currently, the mainstream technology for preparing commercial alumina dispersion-strengthened copper at home and abroad is the internal oxidation method. One of the key processes of the internal oxidation method is that aluminum atoms in the copper-aluminum alloy powder preferentially react with oxygen atoms in the oxygen-supplying agent at high temperature to generate nano-alumina particles. The control requirements of its reaction conditions are very strict, resulting in a low finished product rate of the composite material and a high price, mainly meeting the service in extreme working conditions and special environments. As the content of alumina nanoparticles increases, the pinning effect of the second-phase nanoparticles on dislocations is significantly enhanced. Although the strength of the composite material will increase, at the same time, the electron scattering effect is increased, and the conductivity drops significantly, making it difficult for the material to be popularized in conventional applications. Ball milling is one of the most economical and effective powder-making means, and the powder composition has strong designability. At the same time, it can effectively control the powder morphology and particle size, which helps to regulate fine grain strengthening and electron transport channels, and thus achieve the purpose of optimizing the strength and conductivity matching of the composite material. The great challenge for researchers is how to make the composite material have high-strength and high-conductivity properties.

[0004] Therefore, the problem that needs to be urgently solved by those skilled in the art is: to propose a method for preparing high-strength and high-conductivity alumina dispersion-strengthened copper to solve the technical problem that alumina dispersion-strengthened copper in the prior art cannot obtain high-strength and high-conductivity properties. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing high-strength and high-conductivity alumina dispersion-strengthened copper in view of the deficiencies of the above-mentioned prior art. This method corrodes the surface of copper powder with an aluminum nitrate-ethanol solution to generate copper salts on the surface of the copper powder. The aluminum nitrate and copper powder are refined by ball milling to construct a composite powder of micro-sheet copper powder loaded with nano-alumina particles, and sintered under low-temperature and high-pressure conditions to obtain alumina dispersion-strengthened copper. Since the loaded nano-alumina particles and low-temperature sintering can effectively hinder grain growth, and at the same time, the large grains formed on the large surface of the sheet copper powder can increase the electron transport channels, the alumina dispersion-strengthened copper has high-strength and high-conductivity properties, solving the technical problem that alumina dispersion-strengthened copper in the prior art cannot obtain high-strength and high-conductivity properties.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: a preparation method of high-strength and high-conductivity alumina dispersion-strengthened copper, characterized in that the method comprises the following steps:

[0007] Step 1: Uniformly dissolve aluminum nitrate nonahydrate in absolute ethanol by ultrasonic wave to obtain an aluminum nitrate-absolute ethanol solution;

[0008] Step 2: Mix electrolytic copper powder with the aluminum nitrate-absolute ethanol solution obtained in Step 1 and stir evenly, and then perform vacuum drying treatment to obtain a mixed powder A containing electrolytic copper powder and aluminum nitrate;

[0009] Step 3: Perform ball milling and crushing treatment on the mixed powder A obtained in Step 2 in an inert atmosphere to obtain a refined mixed powder B; the rotation speed of the ball milling is 300 rpm, the ball-to-material ratio is 2.7:1, and the ball milling time is 24 h to 60 h;

[0010] Step 4: Perform reduction treatment on the mixed powder B obtained in Step 3 to obtain a mixed powder C containing copper and alumina; the temperature of the reduction treatment is 400 °C and the time is 3 h;

[0011] Step 5: First perform room-temperature pre-pressing, crushing and exhaust on the mixed powder C obtained in Step 4, and then perform spark plasma sintering to obtain alumina dispersion-strengthened copper; the parameters of the spark plasma sintering are: the sintering temperature is 550 °C, the heat preservation time is 5 min, and the sintering pressure is 400 MPa.

[0012] In the present invention, aluminum nitrate nonahydrate is uniformly dissolved in absolute ethanol by ultrasonic wave, electrolytic copper powder and aluminum nitrate are mixed with absolute ethanol as a solvent, and absolute ethanol is easily volatilized under vacuum heating conditions, so the mixed powder has higher dryness. By controlling the parameters of ball milling, the impurity content can be effectively controlled to avoid the reduction of conductivity. By controlling the temperature and time of the reduction treatment, copper oxide can be fully reduced and aluminum nitrate can be completely decomposed. By controlling the parameters of spark plasma sintering, the grains can be prevented from growing excessively and causing a reduction in strength, and at the same time, a high-density composite material can be obtained.

[0013] In the above preparation method of high-strength and high-conductivity alumina dispersion-strengthened copper, it is characterized in that the inert atmosphere in Step 2 is argon or nitrogen. Ball milling in an inert atmosphere in the present invention can effectively prevent the powder from being over-oxidized.

[0014] In the above preparation method of high-strength and high-conductivity alumina dispersion-strengthened copper, it is characterized in that the ball milling in Step 3 is dry milling and no process control agent is added. In the present invention, without a process control agent, the collision frequency and energy between the steel balls and the powder can be increased, and the powder can be efficiently refined.

[0015] The above-mentioned preparation method of high-strength and high-conductivity alumina dispersion-strengthened copper is characterized in that the atmosphere for the reduction treatment in step four is a hydrogen atmosphere or a mixed atmosphere of hydrogen and an inert gas. In the present invention, a hydrogen atmosphere or a mixed atmosphere of hydrogen and an inert gas is used to reduce copper oxide and decompose aluminum nitrate.

[0016] The above-mentioned preparation method of high-strength and high-conductivity alumina dispersion-strengthened copper is characterized in that the mass content of aluminum in the mixed powder C in step four is 0.2% to 0.6%. By controlling the mass content of aluminum in the present invention, it is ensured that the obtained alumina has excellent dispersibility.

[0017] The above-mentioned preparation method of high-strength and high-conductivity alumina dispersion-strengthened copper is characterized in that the tensile strength of the alumina dispersion-strengthened copper in step five is not less than 600 MPa, and the electrical conductivity is not less than 80% IACS. The alumina dispersion-strengthened copper of the present invention meets the requirements of high strength and high conductivity.

[0018] The present invention has the following advantages compared with the prior art:

[0019] 1. The present invention uses aluminum nitrate nonahydrate as a grinding agent. During the mixing of copper powder and aluminum nitrate-absolute ethanol solution, the corrosion effect of aluminum nitrate on the surface of copper powder can effectively prevent cold welding of the powder during long-term ball milling, and a composite powder with very good dispersibility can be obtained.

[0020] 2. The present invention uses long-term ball milling to construct a micro-flaky copper powder-supported alumina composite powder. The large grains formed on the large surface of the micro-flaky copper powder can effectively increase the electron transport channels, making the alumina dispersion-strengthened copper have high conductivity performance.

[0021] 3. The present invention adopts low-temperature and high-pressure sintering, which can effectively inhibit the excessive growth of grains and obtain a high volume fraction of ultrafine grains, making the alumina dispersion-strengthened copper have high strength performance.

[0022] 4. The preparation method of the present invention is simple and easy to operate, the process is easy to control, and the production cost can be effectively reduced.

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Brief Description of the Drawings

[0024] Figure 1 It is the SEM image of the mixed powder C obtained in step four in Embodiment 2 of the present invention.

[0025] Figure 2 It is the EBSD image of the horizontal plane of the alumina dispersion-strengthened copper prepared in Embodiment 2 of the present invention.

[0026] Figure 3This is the EBSD map of the cross-section of the alumina dispersion strengthened copper prepared in Example 2 of the present invention.

[0027] Figure 4 This is the SEM map of the mixed powder A prepared in Example 5 of the present invention. Detailed implementation manners

[0028] Example 1

[0029] This example includes the following steps:

[0030] Step 1: Uniformly dissolve aluminum nitrate nonahydrate with corresponding content in absolute ethanol by ultrasonic wave to prepare an aluminum nitrate - absolute ethanol solution;

[0031] Step 2: Mix electrolytic copper powder with the aluminum nitrate - absolute ethanol solution in Step 1 and stir evenly, then perform vacuum drying treatment to obtain a mixed powder A of electrolytic copper powder and aluminum nitrate;

[0032] Step 3: Perform ball milling and crushing treatment on the mixed powder A in Step 2 in an inert atmosphere to obtain a refined mixed powder B; the ball milling speed is 300 rpm, the ball - to - material ratio is 2.7:1, and the ball milling time is 24 h;

[0033] Step 4: Perform reduction treatment on the mixed powder B obtained in Step 3 to obtain a mixed powder C of copper and alumina, and the temperature of the reduction treatment is 400 °C and the reduction time is 3 h;

[0034] Step 5: First perform room - temperature pre - pressing, crushing and exhaust on the mixed powder C obtained in Step 4, and then perform spark plasma sintering to obtain alumina dispersion strengthened copper with an aluminum mass fraction of 0.2%; the parameters of the spark plasma sintering are: the sintering temperature is 550 °C, the heat - preservation time is 5 min, and the sintering pressure is 400 MPa.

[0035] After testing, the tensile strength of the alumina dispersion strengthened copper prepared in this example is 610 MPa, and the electrical conductivity is 86.8% IACS.

[0036] Example 2

[0037] This example includes the following steps:

[0038] Step 1: Uniformly dissolve aluminum nitrate nonahydrate with corresponding content in absolute ethanol by ultrasonic wave to prepare an aluminum nitrate - absolute ethanol solution;

[0039] Step 2: Mix electrolytic copper powder with the aluminum nitrate - absolute ethanol solution in Step 1 and stir evenly, then perform vacuum drying treatment to obtain a mixed powder A of electrolytic copper powder and aluminum nitrate;

[0040] Step 3: Subject the mixed powder A obtained in Step 2 to ball milling and crushing treatment in an inert atmosphere to obtain a refined mixed powder B; the ball milling speed is 300 rpm, the ball-to-material ratio is 2.7:1, and the ball milling time is 36 h;

[0041] Step 4: Subject the mixed powder B obtained in Step 3 to reduction treatment to obtain a mixed powder C of copper and alumina, where the temperature of the reduction treatment is 400 °C and the reduction time is 3 h;

[0042] Step 5: First subject the mixed powder C obtained in Step 4 to room temperature pre-pressing, crushing, and exhaust, and then perform spark plasma sintering to obtain alumina dispersion-strengthened copper with an aluminum mass fraction of 0.2%; the parameters of the spark plasma sintering are: the sintering temperature is 550 °C, the heat preservation time is 5 min, and the sintering pressure is 400 MPa.

[0043] Upon testing, the tensile strength of the alumina dispersion-strengthened copper prepared in this example is 654 MPa, and the electrical conductivity is 84.5% IACS.

[0044] Figure 1 This is the SEM image of the mixed powder C obtained in Step 4 of this example. From Figure 1 it can be seen that the micro-flaky copper powder has very good dispersion, there is no obvious cold welding phenomenon, and alumina is evenly loaded on the micro-flaky copper powder.

[0045] Figure 2 This is the EBSD image of the horizontal plane of the alumina dispersion-strengthened copper prepared in this example. Figure 3 This is the EBSD image of the cross-section of the alumina dispersion-strengthened copper prepared in this example. From Figure 2 and Figure 3 it can be seen that there are obvious differences in the grain sizes inside the alumina dispersion-strengthened copper prepared in this example, and a large number of small grains are distributed around the large grains.

[0046] Table 1 Proportion of grain sizes of the horizontal plane and cross-section in Example 2

[0047] Area ratio Grain size ≤ 1μm Grain size > 1μm Horizontal plane 60.2％ 39.8％ Cross section 68.6％ 31.4％

[0048] It can be seen from Table 1 that the proportion of the area of ultrafine grains and nanocrystals is significantly higher than that of coarse grains, and the proportion of the area of ultrafine grains and nanocrystals in the cross-section is greater than that in the horizontal plane.

[0049] Example 3

[0050] This example includes the following steps:

[0051] Step 1: Uniformly dissolve aluminum nitrate nonahydrate with the corresponding content in absolute ethanol by ultrasonic waves to prepare an aluminum nitrate - absolute ethanol solution;

[0052] Step 2: Mix the electrolytic copper powder with the aluminum nitrate-anhydrous ethanol solution in Step 1 and stir evenly, then perform vacuum drying treatment to obtain a mixed powder A of electrolytic copper powder and aluminum nitrate;

[0053] Step 3: Perform ball milling and crushing treatment on the mixed powder A in Step 2 in an inert atmosphere to obtain a refined mixed powder B; the ball milling speed is 300 rpm, the ball-to-material ratio is 2.7:1, and the ball milling time is 48 h;

[0054] Step 4: Perform reduction treatment on the mixed powder B obtained in Step 3 to obtain a mixed powder C of copper and alumina, and the temperature of the reduction treatment is 400 °C and the reduction time is 3 h;

[0055] Step 5: First perform room temperature pre-pressing, crushing and exhaust on the mixed powder C obtained in Step 4, and then perform spark plasma sintering to obtain alumina dispersion strengthened copper with an aluminum mass fraction of 0.2%; the parameters of the spark plasma sintering are: the sintering temperature is 550 °C, the heat preservation time is 5 min, and the sintering pressure is 400 MPa.

[0056] After testing, the tensile strength of the alumina dispersion strengthened copper prepared in this example is 640 MPa, and the electrical conductivity is 84.3% IACS.

[0057] Example 4

[0058] This example includes the following steps:

[0059] Step 1: Uniformly dissolve aluminum nitrate nonahydrate with the corresponding content in anhydrous ethanol by ultrasonic wave to prepare an aluminum nitrate-anhydrous ethanol solution;

[0060] Step 2: Mix the electrolytic copper powder with the aluminum nitrate-anhydrous ethanol solution in Step ① and stir evenly, then perform vacuum drying treatment to obtain a mixed powder A of electrolytic copper powder and aluminum nitrate;

[0061] Step 3: Perform ball milling and crushing treatment on the mixed powder A in Step 2 in an inert atmosphere to obtain a refined mixed powder B; the ball milling speed is 300 rpm, the ball-to-material ratio is 2.7:1, and the ball milling time is 60 h;

[0062] Step 4: Perform reduction treatment on the mixed powder B obtained in Step 3 to obtain a mixed powder C of copper and alumina, and the temperature of the reduction treatment is 400 °C and the reduction time is 3 h;

[0063] Step 5: First, subject the mixed powder C obtained in Step 4 to room-temperature pre-pressing for crushing and degassing, and then perform spark plasma sintering to obtain alumina dispersion-strengthened copper with an aluminum mass fraction of 0.4%. The parameters for the spark plasma sintering are as follows: the sintering temperature is 550 °C, the holding time is 5 min, and the sintering pressure is 400 MPa.

[0064] Upon detection, the tensile strength of the alumina dispersion-strengthened copper prepared in this embodiment is 654 MPa, and the electrical conductivity is 82.0% IACS.

[0065] Example 5

[0066] This embodiment includes the following steps:

[0067] Step 1: Uniformly dissolve aluminum nitrate nonahydrate with the corresponding content in absolute ethanol by ultrasonic treatment to prepare an aluminum nitrate - absolute ethanol solution.

[0068] Step 2: Mix electrolytic copper powder with the aluminum nitrate - absolute ethanol solution in Step 1 and stir evenly, and then perform vacuum drying treatment to obtain a mixed powder A of electrolytic copper powder and aluminum nitrate.

[0069] Step 3: Subject the mixed powder A in Step 2 to ball milling and crushing treatment in an inert atmosphere to obtain a refined mixed powder B. The ball milling speed is 300 rpm, the ball-to-material ratio is 2.7:1, and the ball milling time is 60 h.

[0070] Step 4: Perform reduction treatment on the mixed powder B obtained in Step 3 to obtain a mixed powder C of copper and alumina. The temperature of the reduction treatment is 400 °C, and the reduction time is 3 h.

[0071] Step 5: First, subject the mixed powder C obtained in Step 4 to room-temperature pre-pressing for crushing and degassing, and then perform spark plasma sintering to obtain alumina dispersion-strengthened copper with an aluminum mass fraction of 0.6%. The parameters for the spark plasma sintering are as follows: the sintering temperature is 550 °C, the holding time is 5 min, and the sintering pressure is 400 MPa.

[0072] Upon detection, the tensile strength of the alumina dispersion-strengthened copper prepared in this embodiment is 600 MPa, and the electrical conductivity is 80.5% IACS.

[0073] Figure 4 SEM image of the mixed powder of electrolytic copper powder and aluminum nitrate nonahydrate after stirring and mixing in this embodiment. As can be seen from Figure 4 it, the aluminum nitrate nonahydrate particles are uniformly loaded on the electrolytic copper powder.

[0074] The above are only the preferred embodiments of the present invention and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent variations made to the above embodiments based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing high-strength and high-conductivity alumina dispersion-strengthened copper, characterized in that: The method comprises the following steps: Step 1: uniformly dissolving aluminum nitrate nonahydrate in anhydrous ethanol by ultrasonication to obtain an aluminum nitrate-anhydrous ethanol solution; Step 2: mixing the electrolytic copper powder with the aluminum nitrate-anhydrous ethanol solution obtained in Step 1 and stirring them uniformly, followed by vacuum drying to obtain a mixed powder A containing the electrolytic copper powder and aluminum nitrate; Step 3: The mixed powder A obtained in step 2 is subjected to ball milling in an inert atmosphere to obtain a refined mixed powder B; the ball milling speed is 300 rpm, the ball-to-material ratio is 2.7:1, and the ball milling time is 24 h to 60 h; Step 4: performing a reduction treatment on the mixed powder B obtained in step 3 to obtain a mixed powder C containing copper and aluminum oxide; the reduction treatment temperature is 400° C. and the time is 3 hours; Step 5: The mixed powder C obtained in step 4 is pre-pressed, crushed and exhausted at room temperature, and then subjected to spark plasma sintering to obtain alumina dispersion-strengthened copper; the parameters of the spark plasma sintering are: sintering temperature of 550° C., holding time of 5 min, and sintering pressure of 400 MPa.

2. The method for preparing high-strength and high-conductivity alumina dispersion-strengthened copper according to claim 1, characterized in that: The inert atmosphere in step 3 is argon or nitrogen.

3. The method for preparing high-strength and high-conductivity alumina dispersion-strengthened copper according to claim 1, characterized in that: The ball milling in step 3 is dry milling and no process control agent is added.

4. The method for preparing high-strength and high-conductivity alumina dispersion-strengthened copper according to claim 1, characterized in that: The atmosphere for the reduction treatment in step 4 is a hydrogen atmosphere or a mixed atmosphere of hydrogen and inert gas.

5. The method for preparing high-strength and high-conductivity alumina dispersion-strengthened copper according to claim 1, characterized in that: The mass content of aluminum in the mixed powder C described in step 4 is 0.2%~0.6%.

6. The method for preparing high-strength and high-conductivity alumina dispersion-strengthened copper according to claim 1, characterized in that: The tensile strength of the alumina dispersion-strengthened copper in step 5 is not less than 600 MPa, and the electrical conductivity is not less than 80% IACS.

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