Method for preparing high-strength and high-thermal conductivity aluminum alloy material

Abstract

To provide a high strength and high thermal conductivity aluminum alloy material.SOLUTION: A high strength and high thermal conductivity aluminum alloy material is prepared in such a manner that alkylaluminium intermediates are prepared using alkyl aluminum such as trimethyl aluminum and triethylaluminum and amides such as dimethylformamide and dimethylacetamide as raw materials, and after separating the solid intermediates, the aluminum alloy powders are uniformly mixed with aluminum alloy powder, and finally by heating at a constant temperature and under vacuum conditions to obtain a mixed powder of aluminum nitride and aluminum alloy, the powder is filled into a mold, pressurized, and sintered to create a high-strength, high-thermal-conductivity aluminum alloy materia is obtained.EFFECT: The aluminum nitride of the present invention is produced at low temperatures, has no contamination on its surface, and has good compatibility with the aluminum matrix. The addition of aluminum nitride not only enhances the mechanical properties of the alloy, but also significantly increases the thermal conductivity of the aluminum alloy, therefore it has the potential for wide application in aluminum alloy components.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for preparing a high-strength and high-thermal conductivity aluminum alloy material, and belongs to the field of non-ferrous metal materials.

Background Art

[0002] Aluminum and its alloys have excellent comprehensive properties such as good thermal conductivity, plasticity, and workability. Aluminum alloy materials also have good high-temperature properties, formability, machinability, rivet jointability, and surface treatability. Therefore, aluminum alloys are very widely applied in various fields such as space, aviation, automobiles, transportation, bridges, construction, electronics, energy, power, machinery manufacturing, and electrical furniture. With the development of the industry and the improvement of people's living standards, the increase in chip integration of electronic products and communication devices has increased the device power, the heat generation amount, and the heat dissipation amount per unit volume of the device. Therefore, in order to ensure the service life and operation stability of the product, higher thermal conductivity of the material is required. Pure aluminum has a good thermal conductivity of about 237 W / (m·K) at room temperature, second only to copper (385 W / (m·K)) among metal materials. However, the strength of pure aluminum is too low at only 69 MPa and cannot meet the requirements for industrial production applications. Therefore, usually, the strength of pure aluminum is improved by alloying. However, with the increase in alloying elements, the thermal conductivity of the aluminum alloy gradually decreases.

[0003] The density of aluminum nitride (AlN) is 3.26 g / cm 3, the Mohs hardness is 7-8, the theoretical thermal conductivity is as high as 320 W / (m·K), and the thermal expansion coefficient is close to that of silicon. By incorporating aluminum nitride into aluminum alloys, the mechanical properties of the alloy can be enhanced by utilizing the inhibitory effect of the aluminum nitride strengthening layer on dislocations. On the other hand, by utilizing the high thermal conductivity of aluminum nitride, the thermal conductivity of the entire aluminum alloy can also be improved. Therefore, the research and development of new aluminum-based materials containing aluminum nitride strengthening phases have been emphasized by scientific researchers at home and abroad, and certain progress has been achieved. For example, Chinese Patent 201910884968.8 discloses a method for preparing an aluminum-based composite material strengthened by in-situ generation of two-phase particles of AlN and AlB 2 . In this method, aluminum powder and boron nitride nanosheets are put into a ball milling can at a mass ratio of (96-99):(1-4) of aluminum powder to boron nitride nanosheets, and under an inert gas atmosphere, the aluminum powder and boron nitride nanosheets are uniformly mixed by ball milling. The powder after ball milling is filled into a mold, cold press formed, and then sintered. Chinese Invention Patent 201811453938.3 discloses an aluminum-based composite material strengthened by high-temperature resistant AlN and Al 2 O 3 and its preparation method. In this method, first, ultrafine aluminum powder is pressurized to an appropriate porosity, put into a pack and sealed, and holes are opened around it so that an appropriate amount of air can enter. The pack is put into an air furnace and heated at a low temperature to thicken the oxide film, and then the temperature is raised to a high temperature, and AlN and Al 2 O 3 are generated using nitrogen gas and oxygen gas in the air. Sintering or hot working is performed on the powder after high-temperature treatment to finally obtain an aluminum alloy material. However, since all of the AlN in the above methods is generated by the reaction of aluminum powder with BN or air, it is not easy to adjust and control the reaction process and the volume fraction of the product. In addition, a large amount of heat is generated when the aluminum powder nitrides, causing the powder to agglomerate and even melt, making it impossible to control the product quality.

Summary of the Invention

Problems to be Solved by the Invention

[0004] It is impossible to achieve both high strength and high thermal conductivity of an aluminum alloy. To solve the problems existing in the preparation process of conventional AlN-containing aluminum alloys, such as the uncontrollable production amount of AlN, the agglomeration and melting of aluminum powder, and the difficulty of large-scale mass production, the object of the present invention is to provide a method for preparing a high-strength and high-thermal-conductivity aluminum alloy material specifically including the following steps.

Means for Solving the Problems

[0005] (1) Dissolve alkylaluminum in an amide, dropwise add aqueous ammonia to obtain a mixed solution, adjust the pH of the mixed solution to between 8 and 10, then put the mixed solution into a constant temperature water bath for heating, and cool to obtain a solution containing an alkylaluminum amide intermediate.

[0006] (2) Separate the alkylaluminum amide intermediate in the solution obtained in step (1), uniformly mix it with aluminum alloy powder using a vacuum ball mill, then put the mixed powder into a vacuum high-temperature furnace and heat it to obtain a mixed powder of aluminum nitride and aluminum alloy.

[0007] (3) Fill the AlN / aluminum alloy mixed powder into a mold having a shape corresponding to the part, and press and sinter it to obtain a high-strength and high-thermal-conductivity aluminum alloy material.

[0008] Preferably, the alkylaluminum described in step (1) of the present invention is any one of trimethylaluminum, triethylaluminum, triisobutylaluminum, and ethylaluminum dichloride.

[0009] Preferably, the amide described in step (1) of the present invention is any one of dimethylformamide and dimethylacetamide.

[0010] Preferably, the molar ratio of alkylaluminum, amide, and aqueous ammonia in the mixed solution described in step (1) of the present invention is 1:(0.4 - 0.7):(0.05 - 0.23).

[0011] Preferably, the heating condition in the constant temperature water bath of step (1) of the present invention is to heat at 65 - 80°C for 4 - 6 h.

[0012] Preferably, the separation method of the solid alkylaluminum amide intermediate in step (1) of the present invention is to separate using a commercially available high-speed centrifuge or rotary evaporator, and other feasible separation methods may also be applicable to the present invention.

[0013] Preferably, the aluminum alloy powder in step (2) of the present invention is an alloy powder of the Al - Si system, Al - Cu system, Al - Mg system, or Al - Zn system, with a particle size of 50 - 200 nm, and the molar ratio of the aluminum alloy powder to the alkylaluminum amide intermediate after separation is 1:(0.1 - 0.3).

[0014] Preferably, the conditions for vacuum ball milling in step (2) of the present invention are a vacuum degree of 0.01 - 0.5 Pa, a rotation speed of the ball milling of 100 - 400 r / min, and a ball milling time of 4 - 8 h.

[0015] Preferably, the treatment by the vacuum high-temperature furnace in step (2) of the present invention is a vacuum degree of 0.1 - 1 Pa, a temperature of the high-temperature furnace of 350 - 450°C, and a constant temperature holding time of 1 - 3 h.

[0016] Preferably, the sintering temperature in step (3) of the present invention is 580 - 630°C, and the time is 0.5 - 1 h.

[0017] The pressing and sintering methods described in the present invention may be any one of cold isostatic pressing + sintering by an air furnace, hot isostatic pressing, rapid sintering, and spark plasma sintering.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0019] The aluminum nitride (AlN) of the present invention is produced by reacting alkylaluminum, amide and aqueous ammonia with each other to form an alkylaluminum intermediate, and then under vacuum conditions of 350-450 °C. This avoids the uncontrollable process where aluminum powder produced by conventional methods reacts with BN or air to form AlN. The reaction temperature is relatively low, and both the risk and cost are reduced. In addition, since the AlN reinforcement forms nuclei and grows within the aluminum matrix, there is no contamination on the surface of the AlN, and the compatibility between the matrix and the reinforcement phase is good. Compared with conventional methods, the lattice mismatch between the AlN reinforcement and the aluminum matrix is less than 3%, so it can serve as nuclei for effective heterogeneous nucleation. Due to the uniformly distributed AlN reinforcement of the present invention, it is easy to refine the crystal grains. According to the Hall-Petch formula, the crystal grain size is inversely proportional to mechanical properties such as the yield strength. The smaller the crystal grain size, the better the mechanical properties.

[0020] The high-strength and high-thermal-conductivity aluminum alloy material prepared using the technology of the present invention has its mechanical properties improved by more than 20% compared to those without the AlN reinforcement phase due to the grain refinement effect of AlN. At the same time, due to the contribution of the AlN reinforcement phase to the thermal conductivity, the thermal conductivity of the material is also improved by more than 12%, achieving both the mechanical properties and thermal conductivity of the material.

Brief Description of the Drawings

[0021]

Figure 1

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Figure 4

Embodiments for Carrying out the Invention

[0022] Hereinafter, in relation to the embodiments of the present invention, the technical solutions in the present invention will be clearly and completely described. It is obvious that the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments in the present invention, all other embodiments obtained on the premise that those skilled in the art do not perform creative labor belong to the protection scope of the present invention.

Examples

[0023] Example 1 The present invention relates to a method for preparing an Al-Si series high-strength and high-thermal conductivity aluminum alloy material, and its specific steps are as follows.

[0024] (1) Dissolve trimethylaluminum in dimethylformamide, dropwise add aqueous ammonia to obtain a mixed solution, where the molar ratio of trimethylaluminum, dimethylformamide, and aqueous ammonia is 1:0.6:0.1. Put the mixed solution into a constant temperature water bath and keep it at a constant temperature of 75°C for 5 h, then cool it to obtain a solution containing a trimethylaluminum amide intermediate.

[0025] (2) Use a rotary evaporation device to separate the trimethylaluminum amide intermediate from the solution, put it into a ball milling can, and weigh ZL101 alloy (Chinese symbol, Al-Si series alloy) powder with a particle size of 100 nm and put it into the ball milling can. Set the molar ratio of the aluminum alloy powder to the trimethylaluminum amide intermediate to 1:0.2, and perform ball milling at a vacuum degree of 0.1 Pa and a rotation speed of 300 r / min for 6 h.

[0026] (3) Put the mixed powder after ball milling into a vacuum high-temperature furnace with a vacuum degree of 0.5 Pa and a temperature of 400 °C, and keep it at a constant temperature for 2 h. As shown in Figure 1, a mixed powder of aluminum nitride and Al-Si alloy is obtained. As can be seen from Figure 1, by the above method, an AlN and Al-Si alloy mixed powder on the nanometer order can be obtained, the powder particle size has good uniformity, and there is no surface contamination.

[0027] (4) Fill the AlN and Al-Si alloy mixed powder on the nanometer order into a mold, and by sintering with cold isostatic pressing + an air furnace (sintering temperature 600 °C, time 0.5 h), a high-strength and high-thermal-conductivity aluminum alloy material can be obtained. When the obtained aluminum alloy material was sampled and observed with a transmission electron microscope, its TEM morphology was as shown in Figure 2. As can be seen from Figure 2, the AlN strengthening phase in the material is uniformly dispersed in the aluminum matrix, there are no impurities between the micro interfaces between AlN and the aluminum matrix, and the interface bonding is good.

[0028] As a control, the preparation method of an aluminum alloy material without the addition of an AlN strengthening phase is to directly fill the corresponding alloy powder (Al-Si alloy powder in this example) into a mold, and by sintering with cold isostatic pressing + an air furnace (sintering temperature 600 °C, time 0.5 h), to obtain an aluminum alloy material.

[0029] The high-strength and high-thermal-conductivity aluminum alloy material prepared using the present invention has a grain size reduction from about 500 μm to about 60 μm without the addition of an AlN strengthening phase. Photographs of the grain sizes of both are shown in Figures 3 and 4. Due to the remarkable grain refinement strengthening effect, the tensile strength of the material has been improved from 210 MPa to 260 Mpa. By adding AlN with high thermal conductivity, the thermal conductivity of the material has also been improved from 150.8 W / (m·K) to 172.3 W / (m·K), and an aluminum alloy material with both mechanical properties and thermal conductivity has been obtained.

Example

[0030] Example 2 The present invention relates to a method for preparing an Al-Cu-based high-strength and high-thermal-conductivity aluminum alloy material, and its specific steps are as follows.

[0031] (1) Dissolve triethylaluminum in dimethylacetamide, and dropwise add aqueous ammonia to obtain a mixed solution, where the molar ratio of triethylaluminum, dimethylacetamide, and aqueous ammonia is 1:0.4:0.23. Place the mixed solution in a constant-temperature water bath and keep it at a constant temperature of 80 °C for 4 h, then cool it to obtain a solution containing a triethylaluminum amide intermediate.

[0032] (2) Use a high-speed centrifuge to separate the triethylaluminum amide intermediate from the solution, put it into a ball milling can, and weigh ZL203 alloy (Chinese symbol, Al-Cu-based alloy) powder with a particle size of 200 nm and put it into the ball milling can. Set the molar ratio of the aluminum alloy powder to the triethylaluminum amide intermediate to 1:0.3, and perform ball milling at a vacuum degree of 0.5 Pa and a rotation speed of 100 r / min for 4 h.

[0033] (3) Put the mixed powder after ball milling into a vacuum high-temperature furnace with a vacuum degree of 1 Pa and a temperature of 450 °C, keep it at a constant temperature for 1 h to obtain a mixed powder of aluminum nitride and an Al-Cu-based alloy.

[0034] (4) Fill the mold with the AlN and Al-Cu-based alloy mixed powder on the nanometer scale, and by hot isostatic pressing and air sintering (sintering temperature 630 °C, time 0.5 h), a high-strength and high-thermal-conductivity aluminum alloy material can be obtained.

[0035] As a control, the method for preparing an aluminum alloy material without adding an AlN strengthening phase is to directly fill the corresponding alloy powder (Al-Cu-based alloy powder in this example) into the mold, and obtain the aluminum alloy material by sintering with hot isostatic pressing + an air furnace (sintering temperature 630 °C, time 0.5 h).

[0036] The high-strength and high-thermal conductivity aluminum alloy material prepared using the present invention has a grain size that decreases from about 560 μm to about 80 μm without adding an AlN strengthening phase. Due to the remarkable grain refinement strengthening effect, the tensile strength of the material has increased from 205 MPa to 278 MPa. By adding AlN with high thermal conductivity, the thermal conductivity of the material has also increased from 154.9 W / (m·K) to 179.6 W / (m·K), obtaining an aluminum alloy material that combines mechanical properties and thermal conductivity.

Example

[0037] Example 3 The present invention relates to a method for preparing an Al-Mg-based high-strength and high-thermal conductivity aluminum alloy material, and its specific steps are as follows.

[0038] (1) Triisobutylaluminum is dissolved in dimethylacetamide, and ammonia water is added dropwise to obtain a mixed solution. The molar ratio of triisobutylaluminum, dimethylacetamide, and ammonia water is 1:0.7:0.05. The mixed solution is placed in a constant temperature water bath and kept at a constant temperature of 65 °C for 6 h, then cooled to obtain a solution containing a triisobutylaluminum amide intermediate.

[0039] (2) The triisobutylaluminum amide intermediate is separated from the solution using a high-speed centrifuge and placed in a ball milling can. At the same time, ZL303 alloy (Chinese symbol, Al-Mg-based alloy) powder with a particle size of 50 nm is weighed and placed in the ball milling can. The molar ratio of the aluminum alloy powder to the triisobutylaluminum amide intermediate is 1:0.1, and ball milling is carried out at a vacuum degree of 0.01 Pa and a rotation speed of 400 r / min for 8 h.

[0040] (3) The mixed powder after ball milling is placed in a vacuum high-temperature furnace at a vacuum degree of 0.1 Pa and a temperature of 350 °C, and kept at a constant temperature for 3 h to obtain a mixed powder of aluminum nitride and an Al-Mg-based alloy.

[0041] (4) Fill a mold with AlN and Al-Mg alloy mixed powder on the nanometer order, and by rapid sintering (sintering temperature 580 °C, time 1 h), a high-strength and high-thermal conductivity aluminum alloy material can be obtained.

[0042] As a control, the preparation method of an aluminum alloy material without the addition of AlN strengthening phase is to directly fill a corresponding alloy powder (Al-Mg alloy powder in this example) into a mold, and by rapid sintering (sintering temperature 580 °C, time 1 h), obtain an aluminum alloy material.

[0043] The high-strength and high-thermal conductivity aluminum alloy material prepared using the present invention has a decrease in grain size from about 450 μm to about 36 μm without the addition of AlN strengthening phase. Due to the remarkable grain refinement strengthening effect, the tensile strength of the material has been improved from 148 MPa to 189 MPa. By adding AlN with high thermal conductivity, the thermal conductivity of the material has also been improved from 125.6 W / (m·K) to 160.7 W / (m·K), and an aluminum alloy material with both mechanical properties and thermal conductivity has been obtained.

Example

[0044] Example 4 The present invention relates to a method for preparing an Al-Zn-based high-strength and high-thermal conductivity aluminum alloy material, and its specific steps are as follows.

[0045] (1) Dissolve ethylaluminum dichloride in dimethylacetamide, dropwise add aqueous ammonia to obtain a mixed solution, and the molar ratio of ethylaluminum dichloride, dimethylacetamide, and aqueous ammonia is 1:0.5:0.17. Put the mixed solution into a constant temperature water bath, keep it at a constant temperature of 70 °C for 4.5 h, and cool to obtain a solution containing an ethylaluminum dichloride amide intermediate.

[0046] (2) Use a high-speed centrifuge to separate the ethylaluminum dichloride amide intermediate from the solution, put it into a ball milling can, weigh the ZL402 alloy (Chinese symbol, Al-Zn alloy) powder with a particle size of 150 nm and put it into the ball milling can, and set the molar ratio of the aluminum alloy powder to the ethylaluminum dichloride amide intermediate to 1:0.15. Perform ball milling at a vacuum degree of 0.4 Pa and a rotation speed of 200 r / min for 6.5 h.

[0047] (3) Put the mixed powder after ball milling into a vacuum high-temperature furnace with a vacuum degree of 0.8 Pa and a temperature of 370 °C, keep it at a constant temperature for 2.5 h to obtain a mixed powder of aluminum nitride and Al-Zn alloy.

[0048] (4) Fill the mold with the AlN and Al-Zn alloy mixed powder on the nanometer order, and by means of discharge plasma sintering (sintering temperature 590 °C, time 0.8 h), a high-strength and high-thermal conductivity aluminum alloy material can be obtained.

[0049] As a control, the preparation method of the aluminum alloy material without the addition of the AlN strengthening phase is to directly fill the corresponding alloy powder (Al-Zn alloy powder in this example) into the mold, and by means of discharge plasma sintering (sintering temperature 590 °C, time 0.8 h), obtain the aluminum alloy material.

[0050] The high-strength and high-thermal conductivity aluminum alloy material prepared by using the present invention has a decrease in the grain size from about 480 μm to about 73 μm without the addition of the AlN strengthening phase. Due to the remarkable grain refinement strengthening effect, the tensile strength of the material has been improved from 235 MPa to 287 Mpa. By adding AlN with high thermal conductivity, the thermal conductivity of the material has also been improved from 138 W / (m·K) to 157 W / (m·K), and an aluminum alloy material with both mechanical properties and thermal conductivity has been obtained.

Claims

1. A method for preparing a high-strength and high-thermal conductivity aluminum alloy material, comprising: dissolving alkylaluminum in an amide, dropping aqueous ammonia to obtain a mixed solution, adjusting the pH of the mixed solution to between 8 and 10, and then putting the mixed solution into a constant-temperature water bath for heating and cooling to obtain a solution containing an alkylaluminum amide intermediate (step (1)); separating the alkylaluminum amide intermediate in the solution obtained in step (1), uniformly mixing it with aluminum alloy powder using a vacuum ball mill, and then putting the mixed powder into a vacuum high-temperature furnace for heating to obtain a mixed powder of aluminum nitride and aluminum alloy (step (2)), wherein the molar ratio of the aluminum alloy powder to the separated alkylaluminum amide intermediate is 1:(0.1 - 0.3) (step (2)); filling the AlN / aluminum alloy mixed powder into a mold having a shape corresponding to the part, and performing pressing and sintering to obtain a high-strength and high-thermal conductivity aluminum alloy material (step (3)); specifically including: the conditions of the vacuum ball milling in step (2) are that the vacuum degree is 0.01 - 0.5 Pa, the rotation speed of the ball milling is 100 - 400 r / min, and the ball milling time is 4 - 8 h; the treatment by the vacuum high-temperature furnace in step (2) is that the vacuum degree is 0.1 - 1 Pa, the temperature of the high-temperature furnace is 350 - 450 °C, and the constant-temperature holding time is 1 - 3 h; A method for preparing a high-strength and high-thermal conductivity aluminum alloy material, characterized by the above.

2. The alkylaluminum described in step (1) is any one of trimethylaluminum, triethylaluminum, triisobutylaluminum, and ethylaluminum dichloride. A method for preparing a high-strength and high-thermal conductivity aluminum alloy material according to claim 1, characterized by the above.

3. The amide described in step (1) is any one of dimethylformamide and dimethylacetamide. A method for preparing a high-strength and high-thermal conductivity aluminum alloy material according to claim 1 or claim 2, characterized by the above.

4. The molar ratio of the alkylaluminum, the amide, and the aqueous ammonia in the mixed solution described in step (1) is 1:(0.4 - 0.7):(0.05 - 0.23). A method for preparing a high-strength and high-thermal conductivity aluminum alloy material according to claim 3, characterized by the above.

5. The heating condition in the constant temperature water bath in step (1) is to heat at 65 to 80 °C for 4 to 6 h. The method for preparing a high-strength and high-thermal conductivity aluminum alloy material according to claim 1, characterized in that.

6. The separation method of the solid alkylaluminum amide intermediate in step (1) is to separate using a commercially available high-speed centrifuge or rotary evaporator. The method for preparing a high-strength and high-thermal conductivity aluminum alloy material according to claim 5, characterized in that.

7. The aluminum alloy powder in step (2) is an alloy powder of Al-Si system, Al-Cu system, Al-Mg system, or Al-Zn system, and the particle size is 50 to 200 nm. The method for preparing a high-strength and high-thermal conductivity aluminum alloy material according to claim 1, characterized in that.

8. The sintering temperature in step (3) is 580 to 630 °C, and the time is 0.5 to 1 h. The method for preparing a high-strength and high-thermal conductivity aluminum alloy material according to claim 1, characterized in that.

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