Diamond particle aluminum-based composite material and preparation method thereof

Abstract

The embodiment of the invention provides a diamond particle aluminum-based composite material and a preparation method thereof, and the preparation method is characterized by comprising the following steps: (X1) carrying out wet ball milling, dispersion and drying on aluminum powder and diamond particles with preset volume fractions to obtain diamond particle aluminum-based composite powder; and (X2) the diamond particle aluminum-based composite powder obtained in the step (X1) is subjected to vacuum hot pressing sintering, gradient heating is conducted in the vacuum hot pressing sintering process, pressure is applied to the diamond particle aluminum-based composite powder in the gradient heating process, and the diamond particle aluminum-based composite material is obtained. According to the embodiment of the invention, a brittle Al3C4 phase generated by mutual diffusion reaction of carbon atoms and aluminum atoms due to high temperature can be reduced, so that the problems of increased interface thermal resistance and relatively low density of the composite material caused by the brittle Al3C4 phase are reduced; material deformation and stress concentration can be reduced; therefore, the diamond particle aluminum-based composite material with good interface bonding, high density and good thermal physical performance can be obtained.

Description

Technical Field

[0001] The present invention relates to the field of material preparation, and particularly to a diamond particle aluminum matrix composite material and a preparation method thereof. Background Art

[0002] With the increasingly diversified and complex development of aerospace and electronic devices, the requirements for material properties are becoming more and more stringent. Materials with high thermal conductivity, low coefficient of thermal expansion, and high strength play a crucial role in ensuring the reliability and service life of satellite structural components. However, when high-power density electronic devices are operating, the average heat flux density exceeds 15 W / cm 2 , and the huge amount of heat cannot be effectively dissipated, resulting in an increasing failure rate, which has become a bottleneck restricting the further development of electronic devices. The unique crystal structure of diamond endows it with extremely high intrinsic thermal conductivity (up to 2000 W / m·K at most) and extremely low coefficient of thermal expansion (about 1.0×10 -6 K -1 ), making it an ideal reinforcing phase material in the fields of aerospace and electronic packaging. Diamond not only has excellent thermal conductivity, but also has high strength and low density, and plays a huge role in improving the thermal conductivity and mechanical properties of aluminum matrix composites. Therefore, diamond has become an ideal reinforcing phase for composite materials in the fields of aerospace equipment and electronic packaging devices, etc. However, in some cases, doping diamond will lead to a decline in the thermophysical properties and mechanical properties of the composite material.

[0003] In summary, there is an urgent need to develop a new type of aluminum matrix composite material at present. The new type of aluminum matrix composite material is required to have high thermal conductivity, low coefficient of thermal expansion, and high density. Summary of the Invention

[0004] Therefore, based on the deficiencies of the prior art, the embodiments of the present invention provide a diamond particle aluminum matrix composite material and a preparation method thereof, so as to prepare a diamond particle aluminum matrix composite material with good interfacial bonding, high density, and good thermophysical properties.

[0005] The embodiments of the present invention provide a preparation method of a diamond particle aluminum matrix composite material, including the steps of:

[0006] (X1) Wet ball milling, dispersing, and drying aluminum powder and diamond particles with preset volume fractions respectively to obtain diamond particle aluminum matrix composite powder;

[0007] (X2) Vacuum hot pressing and sintering the diamond particle aluminum matrix composite powder obtained in the step (X1), performing gradient heating during the vacuum hot pressing and sintering, and applying pressure to the diamond particle aluminum matrix composite powder during the gradient heating process to obtain a diamond particle aluminum matrix composite material.

[0008] In some embodiments, the step (X2) specifically includes:

[0009] (X21) First-stage temperature rise: Raise the temperature to 300°C - 400°C at a heating rate of 6°C / min to 10°C / min;

[0010] (X22) First-stage heat preservation: 10 min to 30 min;

[0011] (X23) Second-stage temperature rise: Apply a pressure of 20 MPa - 25 Mpa to the diamond particle aluminum-based composite powder, and then continue to raise the temperature to 500°C - 600°C at a rate of 8°C / min to 10°C / min. During the temperature rise process, increase the pressure applied to the diamond particle aluminum-based composite powder to 50 MPa - 55 MPa at a rate of 1 MPa / min to 1.5 MPa / min;

[0012] (X24) Second-stage heat preservation: Heat preservation for 1 h to 3 h;

[0013] (X25) End the heating, cool down, stop applying pressure to the diamond particle aluminum-based composite powder after cooling to 400°C, and continue to cool.

[0014] In some embodiments, the step (X1) specifically includes:

[0015] (X11) Wet ball mill aluminum powder and diamond particles with preset volume fraction ratios under a protective atmosphere to obtain a composite powder. The wet ball milling specifically includes alternately rotating the ball mill clockwise and counterclockwise, and stopping during the alternation;

[0016] (X12) Place the composite powder obtained in the step (X11) in a protective atmosphere for ultrasonic dispersion to obtain a dispersed composite powder;

[0017] (X13) Place the dispersed composite powder obtained in the step (X12) in a vacuum environment for drying treatment to obtain the diamond particle aluminum-based composite powder.

[0018] In some embodiments, the duration of each clockwise rotation ball milling and each counterclockwise rotation ball milling in the step (X11) is 3 min to 5 min respectively; the stopping time during the alternation is 1 min to 2 min, and the total time of the wet ball milling is 6 h.

[0019] In some embodiments, the average particle size of the aluminum powder in the step (X11) is 25 μm to 30 μm; the average particle size of the diamond particles is 200 μm to 250 μm.

[0020] In some embodiments, the preset volume fraction ratio of the aluminum powder to the diamond particles is 10-11:10-9.

[0021] In some embodiments, the rotation speed of the wet ball milling is 100 rpm to 150 rpm.

[0022] In some embodiments, in the step (X13), the initial temperature in the drying treatment is 30°C to 40°C, and the temperature is increased at a rate of 5°C to 8°C every 2 h to 4 h until the temperature reaches 50°C to 60°C, and then dried for 24 h to 48 h.

[0023] An embodiment of the present invention also provides a diamond particle aluminum matrix composite material, including the diamond particle aluminum matrix composite material prepared by using the diamond particle aluminum matrix composite material preparation method described in any one of the above.

[0024] In some embodiments, the density of the diamond particle aluminum matrix composite material is greater than or equal to 98.5%, the thermal conductivity is 400 W / m·K to 470 W / m·K, and the thermal expansion coefficient is 5.1×10 -6 K -1 ~11.0×10 -6 K -1 .

[0025] The embodiments of the present invention at least include the following beneficial effects: By wet ball milling, dispersing, and drying aluminum powder and diamond particles, the embodiments of the present invention prepare a highly active diamond particle aluminum matrix composite powder, and then further perform vacuum sintering with gradient temperature increase on the diamond particle aluminum matrix composite powder, which can reduce the adverse effects of impurity atoms on sintering during the sintering process, reduce the mutual diffusion reaction of carbon atoms and aluminum atoms caused by high temperature to generate a brittle Al3C4 phase, and further reduce the problems of increased interfacial thermal resistance and low density of the composite material caused thereby, which is beneficial to making the temperature distribution of the material more uniform, reducing the risk of cracks or deformation of the material due to excessive temperature difference between the surface and the inside, and is also beneficial to reducing material deformation and stress concentration, so that a diamond particle aluminum matrix composite material with good interfacial bonding, high density, and good thermophysical properties can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic flow chart of a method for preparing a diamond particle aluminum matrix composite material provided by an embodiment of the present invention.

[0027] Figure 2 is Figure 1 a specific flow chart of step X1 in the method for preparing the diamond particle aluminum matrix composite material shown.

[0028] Figure 3 is Figure 1Schematic diagram of the specific process of step X2 of the preparation method of the diamond particle aluminum matrix composite material shown.

[0029] Figure 4 Morphology diagram of the aluminum powder before wet ball milling used in Example 1.

[0030] Figure 5 Morphology diagram of the diamond particles before wet ball milling used in Example 1.

[0031] Figure 6 Morphology diagram of the aluminum powder and diamond particles after wet ball milling used in Example 1.

[0032] Figure 7 Scanning electron microscope image of the diamond particle aluminum matrix composite material prepared by the method of Example 1.

[0033] Figure 8 Scanning electron microscope image of the diamond particle aluminum matrix composite material prepared by the method of Example 2.

[0034] Figure 9 Scanning electron microscope image of the diamond particle aluminum matrix composite material prepared by the method of Example 3.

[0035] Figure 10 Scanning electron microscope image of the diamond particle aluminum matrix composite material prepared by the method of Example 4.

[0036] Figure 11 Scanning electron microscope image of the diamond particle aluminum matrix composite material prepared by the method of Example 5. Detailed implementation manners

[0037] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following will describe the detailed implementation manners of the present invention in conjunction with the accompanying drawings.

[0038] In order to enable those of ordinary skill in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0039] It should be noted that the terms "first", "second", etc. in the description, claims and above-mentioned drawings of the present invention are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0040] It should also be noted that the division of multiple embodiments in the present invention is only for the convenience of description and should not constitute a special limitation. The features in various embodiments can be combined and cross-referenced without conflict.

[0041] The unique crystal structure of diamond enables its intrinsic thermal conductivity to reach up to 2000 W / m·K, and its thermal expansion coefficient is only 1.0×10 -6 K -1 . At the same time, diamond also has excellent mechanical properties and a low density, making it an ideal reinforcing phase for composite materials in the fields of aviation equipment and electronic packaging devices. However, the carbon atom dangling bonds on the diamond surface will adsorb impurity atoms in the environment and self-close-couple with adjacent carbon atoms, thereby reducing its surface energy and forming a stable surface. This results in a wetting angle between diamond and liquid metal aluminum exceeding 140°, which in turn affects the interfacial bonding between diamond and aluminum. When the composite material preparation temperature is too high or affected by stress, the carbon atoms of diamond and the aluminum atoms in the aluminum matrix diffuse into each other and react with aluminum at the interface to form a brittle Al3C4 phase, which not only increases the interfacial thermal resistance and destroys the interface structure, but also causes the thermophysical properties and mechanical properties of the composite material to decline, resulting in a lower density and particle agglomeration of the composite material.

[0042] Based on the above technical problems, referring to Figure 1 , an embodiment of the present invention provides a method for preparing a diamond particle aluminum matrix composite material, including the steps of:

[0043] Step X1: Wet ball milling, dispersing and drying aluminum powder and diamond particles with preset volume fractions respectively to obtain diamond particle aluminum matrix composite powder;

[0044] Step X2: Vacuum hot pressing and sintering the diamond particle aluminum matrix composite powder obtained in Step X1, performing gradient heating during the vacuum hot pressing and sintering process, and applying pressure to the diamond particle aluminum matrix composite powder during the gradient heating process to obtain a diamond particle aluminum matrix composite material.

[0045] In step X1, aluminum powder and diamond particles are incorporated into the liquid medium of wet ball milling to perform wet ball milling, which helps to reduce the contact of aluminum powder and diamond particles with oxygen during the wet ball milling process, thereby reducing the oxygen content of the obtained diamond particle aluminum-based composite powder and making the diamond particle aluminum-based composite powder highly active. Moreover, during the wet ball milling process, microdefects are introduced on the surface of diamond particles or the surface energy of diamond particles is increased through mechanochemical action to improve the chemical activity of the particles and promote the formation of a stronger interfacial bond with the aluminum matrix during the sintering process.

[0046] In step X2, vacuum hot pressing sintering causes the diamond particle aluminum-based composite powder to sinter into a diamond particle aluminum-based composite material. During the sintering process, maintaining a vacuum sintering environment is beneficial for reducing the introduction of oxygen during sintering, thereby reducing the adverse effects of impurity atoms on sintering; at the same time, the gas in the micropores of the formed diamond particle aluminum-based composite material is removed, accelerating the densification process of the material, and thus improving the overall performance of the diamond particle aluminum-based composite material. During the vacuum hot pressing sintering process, the sintering temperature of the diamond particle aluminum-based composite powder is lower than the melting point of aluminum, which is further beneficial for reducing the mutual diffusion reaction of carbon atoms and aluminum atoms caused by high temperature to generate the brittle Al3C4 phase, and further reducing the problems of increased interfacial thermal resistance and lower density of the composite material caused thereby; at the same time, through appropriate interfacial reactions, such as the combination of aluminum and the active sites on the surface of diamond, a metallurgical bonding interface is formed; this helps to reduce the complexity of the preparation process and reduce the preparation cost. Moreover, the vacuum hot pressing sintering is carried out in a gradient heating manner, which is beneficial for making the temperature distribution of the material more uniform, reducing the risk of cracks or deformation of the material caused by excessive temperature difference between the surface and the inside; at the same time, it is also beneficial for reducing material deformation and stress concentration, and thus beneficial for improving the density and thermophysical properties of the diamond particle aluminum-based composite material.

[0047] In the embodiment of the present invention, by performing wet ball milling, dispersion, and drying on aluminum powder and diamond particles to prepare a highly active diamond particle aluminum-based composite powder, and then further performing vacuum sintering with gradient heating on the diamond particle aluminum-based composite powder, it is possible to reduce the adverse effects of impurity atoms on sintering during the sintering process, reduce the mutual diffusion reaction of carbon atoms and aluminum atoms caused by high temperature to generate the brittle Al3C4 phase, and further reduce the problems of increased interfacial thermal resistance and lower density of the composite material caused thereby, which is beneficial for making the temperature distribution of the material more uniform, reducing the risk of cracks or deformation of the material caused by excessive temperature difference between the surface and the inside, and is also beneficial for reducing material deformation and stress concentration, so as to obtain a diamond particle aluminum-based composite material with good interfacial bonding, high density, and good thermophysical properties.

[0048] Applying pressure to the diamond particle aluminum matrix composite powder during the sintering process can significantly improve the density of the material, reduce the porosity, improve the uniformity of particle distribution, effectively avoid particle agglomeration, and thus enable the composite material to have a more uniform microstructure. Secondly, the presence of pressure can promote an increase in the interfacial contact area between the reinforcing particles and the aluminum matrix, further facilitating the plastic flow and atomic diffusion of the diamond particle aluminum matrix composite powder at high temperatures, enabling the aluminum powder to quickly wrap the diamond particles, thereby enhancing the interfacial reaction efficiency, forming a higher-strength interfacial bond, and reducing the possibility of particle detachment and interfacial defects. In addition, applying pressure can also effectively improve the mechanical properties of the composite material, including tensile strength, hardness, and toughness, because higher density and stronger interfacial bonding significantly reduce the failure risk caused by stress concentration and weak bonding regions. On the other hand, the action of pressure also has a positive impact on the thermal conductivity performance. By reducing the pore and interfacial thermal resistance and enhancing the continuity of the heat conduction path between particles, the thermal conductivity of the composite material is improved. In addition, applying pressure can also shorten the sintering time, reduce the sintering temperature, and improve the dimensional accuracy and stability of the composite material.

[0049] In some specific embodiments, in step X2, the diamond particle aluminum matrix composite powder is placed in a mold, which can enable the diamond particle aluminum matrix composite powder to sinter into a diamond particle aluminum matrix composite material with a specific shape. Specifically, the inner liner, punch, and gasket of the graphite mold are taken out, and boron nitride release agent is sprayed on the inner wall of the inner liner and the surfaces of the punch and gasket that come into contact with the composite powder. After the alcohol in the release agent has completely evaporated, the inner liner, punch, and gasket are reassembled into the graphite mold. A small amount of composite powder is taken out and filled into the inner liner of the graphite mold, and the filling amount is 1 / 3 of the inner liner volume. After filling, sintering is carried out.

[0050] Specifically, referring to Figure 3 , step X2 specifically includes:

[0051] Step X21: First-stage heating: Raise the temperature to 300°C - 400°C at a heating rate of 6°C / min - 10°C / min;

[0052] Step X22: First-stage heat preservation: 10 min - 30 min;

[0053] Step X23: Second-stage heating: Apply a pressure of 20 MPa - 25 Mpa to the diamond particle aluminum matrix composite powder, and then continue to raise the temperature to 500°C - 600°C at a rate of 8°C / min - 10°C / min. During the heating process, increase the pressure applied to the diamond particle aluminum matrix composite powder from 20 MPa - 25 Mpa to 50 MPa - 55 MPa at a rate of 1 MPa / min - 1.5 MPa / min;

[0054] Step X24: Second-stage heat preservation: Heat preservation for 1 h to 3 h;

[0055] Step X25: End the heating, perform cooling. After cooling to 400 °C, stop applying pressure to the diamond particle aluminum matrix composite powder, and continue to cool.

[0056] It can be understood that steps X21 to X25 are sub-steps of step X2.

[0057] By performing the above-mentioned vacuum hot pressing sintering with gradient heating and introducing diamond particles, not only the excellent thermophysical properties of diamond are effectively utilized, the thermal conductivity of the diamond particle aluminum matrix composite is improved, but also the cost is reduced. The obtained diamond particle aluminum matrix composite has high density and good interfacial bonding. By controlling the pressure and temperature applied to the diamond particle aluminum matrix composite powder during the heating process, the density and thermophysical properties of the obtained diamond particle aluminum matrix composite can also be adjusted.

[0058] In some embodiments, referring to Figure 2 , step X1 specifically includes:

[0059] Step X11: Wet ball mill aluminum powder and diamond particles with preset volume fraction ratios under a protective atmosphere to obtain a composite powder. The wet ball milling specifically includes alternately performing clockwise ball milling and counterclockwise ball milling, and stopping rotation during the alternation;

[0060] Step X12: Place the composite powder obtained in step X11 in a protective atmosphere for ultrasonic dispersion to obtain a dispersed composite powder;

[0061] Step X13: Place the dispersed composite powder obtained in step X12 in a vacuum environment for drying treatment to obtain a diamond particle aluminum matrix composite powder.

[0062] The purities of the aluminum powder and diamond particles used in step X11 are both greater than or equal to 99.95%. By alternately performing clockwise ball milling and counterclockwise ball milling in step X11, the average particle size of the obtained composite powder can be reduced, and the agglomeration of the composite powder can be reduced, increasing the dispersibility of the composite powder.

[0063] During the wet ball milling process, stopping the rotation during alternation is beneficial for reducing the probability of overheating, minimizing excessive wear of the composite powder, and improving the mixing effect. First, the friction between the ball milling medium and the composite powder in wet ball milling generates heat. Therefore, if ball milling continues, the temperature of the ball milling medium and the powder may rise, leading to sintering of the powder or excessive particle deformation. Thus, stopping the rotation during the alternation between clockwise and counterclockwise ball milling helps cool the ball milling medium, aluminum powder, and diamond particles, reducing the probability of degradation of the composite powder material caused by overheating. Second, when the rotation stops, the contact between the ball milling medium and the composite powder decreases, which is conducive to reducing excessive wear of the composite powder and refining the composite powder. If directly reversed, it may cause unnecessary wear of the composite powder, thereby affecting the particle size and distribution of the composite powder. Then, during the stop of rotation, the relative movement between the composite powder and the ball milling medium slows down, which helps redistribute the particles in the composite powder and promotes sufficient contact and uniform mixing between the particles of the composite powder.

[0064] Step X12: After wet ball milling in step X11, the composite powder is mixed with the liquid medium added in the wet ball milling to form a liquid medium slurry, and the liquid medium slurry is ultrasonically dispersed to improve the dispersion of the composite powder in the liquid medium.

[0065] In step X11 and step X12, both wet ball milling and ultrasonic dispersion are carried out in a protective atmosphere to reduce the oxidation of the composite powder, reduce the possibility of an increase in the oxygen content in the composite powder, and maintain the high activity of the composite powder.

[0066] Specifically, high-purity argon is used to form a protective atmosphere, which specifically includes evacuating the environment where wet ball milling is located, and then filling it with high-purity argon until the pressure in the environment where wet ball milling is located is the same as the external pressure, and repeating the above operation at least twice; evacuating the environment where ultrasonic dispersion is located, and then filling it with high-purity argon until the pressure in the environment where the composite powder is dispersed is the same as the external pressure, and repeating the above operation at least twice.

[0067] Step X13: Drying is carried out in a vacuum environment to accelerate the evaporation rate of the liquid medium in wet ball milling, thereby reducing the drying time and improving the drying efficiency; at the same time, it can also reduce the oxygen content in the environment, thereby reducing the probability of oxidation of the diamond particle aluminum matrix composite powder and facilitating the maintenance of the high activity of the diamond particle aluminum matrix composite powder.

[0068] Thus, the obtained diamond particle aluminum matrix composite powder has the properties of low agglomeration, high activity, low oxygen content, and uniform particle size. These properties enable the diamond particle aluminum matrix composite powder to further improve its chemical activity during vacuum sintering in step X2, promote the formation of a stronger interfacial bond between the diamond and the aluminum matrix during sintering, thereby effectively reducing the sintering temperature, further reducing the generation of the Al3C4 phase, and improving the density and thermophysical properties of the diamond particle aluminum matrix composite material.

[0069] In some embodiments, the average particle size of the aluminum powder in step X11 is 25 μm to 30 μm; the average particle size of the diamond particles is 200 μm to 250 μm. Thus, the diamond particles can be evenly dispersed in the aluminum powder. If the particle size of the diamond particles is too large, it will lead to insufficient crushing of the aluminum powder and diamond particles during the ball milling process, making it difficult to obtain finer aluminum powder. If the particle size of the diamond particles is too small, the oxygen introduced by the particles will also increase, making it difficult to obtain a diamond particle aluminum matrix composite powder with low oxygen content and high activity. Therefore, using aluminum powder and diamond particles with the above-mentioned particle sizes helps to prepare a diamond particle aluminum matrix composite powder with low agglomeration, high activity, low oxygen content, and uniform particle size.

[0070] Specifically, in step X1, the morphology of the aluminum powder particles is spherical. Spherical aluminum powder particles have good fluidity and uniformity, which can promote the dispersibility during the mixing process. In the embodiments using a mold for sintering, the spherical aluminum powder particles can more easily fill the mold, thereby helping to reduce the generation of pores or defects in the obtained diamond particle aluminum matrix composite material; the morphology of the diamond particles is a near-spherical polyhedron, which helps to reduce the packing resistance between the particles, improve the dispersibility of the particles, and thus optimize the uniformity of the composite material. Its polyhedral shape can provide a larger interfacial contact area, which can promote good bonding between the diamond particles and the aluminum matrix during sintering, thereby improving the thermal conductivity of the composite material.

[0071] In some embodiments, the preset volume fraction ratio of aluminum powder to diamond particles is 10-11:10-9. When the volume fraction of diamond particles is low, it is difficult to significantly improve the thermophysical properties and mechanical properties of the composite material. At low volume fractions, the diamond particles are sparsely distributed in the aluminum matrix and cannot form an effective heat conduction network. The overall thermal conductivity is still mainly dominated by the aluminum matrix, and the improvement amplitude is limited. At the same time, the distance between diamond particles is large, and heat transfer depends more on the aluminum matrix, making it difficult to fully utilize the high thermal conductivity of diamond particles. In addition, due to the insufficient proportion of diamond particles, the inhibitory effect on the thermal expansion coefficient of the aluminum matrix is small, and the overall thermal expansion coefficient of the composite material is reduced limitedly. In terms of mechanical properties, the low volume fraction results in the inability of diamond particles to form a continuous stress transfer network, and the enhancement effect on the strength and rigidity of the composite material is insufficient. When the volume fraction of diamond particles is high, although the enhancement effect of the composite material will continue to increase theoretically, other problems are likely to occur. High volume fractions easily lead to increased contact between particles, and it is difficult for the matrix aluminum to completely fill the gaps, thus forming pores, significantly increasing the interfacial thermal resistance and reducing the thermal conductivity of the composite material. At the same time, the particles are prone to agglomeration at high volume fractions, with uneven distribution, resulting in local stress concentration and reducing the strength and fracture toughness of the composite material. In addition, the fluidity of the material decreases significantly at high volume fractions, increasing the difficulty of the preparation process (such as vacuum hot pressing sintering), and thus it is difficult to make the particles evenly distributed and achieve high density. Therefore, choosing the volume fraction ratio in this embodiment is the result of a comprehensive balance of thermophysical properties, mechanical properties, and process adaptability. Within this range, the composite material can have excellent thermal conductivity, low thermal expansion coefficient, and good mechanical properties, while ensuring the operability of the preparation process and the uniformity of the material. Thus, the preset volume fraction ratio of aluminum powder to diamond particles being 10-11:10-9 is beneficial to balancing thermophysical properties, mechanical properties, and process adaptability, enabling the composite material to have excellent thermal conductivity, low thermal expansion coefficient, good mechanical properties, and good uniformity, while ensuring the operability of the preparation process. In addition, by adjusting the ratio between aluminum powder and diamond particles, the thermal properties of the diamond particle aluminum matrix composite material can be adjusted to meet the requirements of different application scenarios.

[0072] In some specific embodiments, the duration of each clockwise rotation and each counterclockwise rotation of the ball milling in step X11 are 3 min - 5 min respectively; the stopping time during alternation is 1 min - 2 min, and the total ball milling time is 6 h. The time of a single ball milling does not exceed 5 min, which is beneficial to reducing the probability of phenomena such as agglomeration, combination, and excessive cold welding of the composite powder, and reducing the influence on the crushing effect of aluminum powder and diamond particles; the time of a single ball milling is greater than or equal to 2 min, enabling the aluminum powder and diamond particles to be fully ball milled to obtain composite powder with a smaller particle size.

[0073] When alternating, the ball milling stop time is 1 min to 2 min, which helps to fully promote the mixing and distribution of aluminum powder and diamond particles, and is beneficial to effectively reduce the heat generated during the ball milling process; at the same time, it can also reduce the unnecessary refinement of the composite powder, reduce the probability of agglomeration, and reduce wear, and helps the ball milling to reach the required motion state again and maintain the ball milling efficiency. When the ball milling stop time is less than one minute, it is difficult to fully promote the mixing and distribution of aluminum powder and diamond particles, resulting in poor uniformity of the composite powder. At the same time, it may be difficult to effectively reduce the temperature during the ball milling process, and thus it is difficult to reduce the overheating problem. When the ball milling stop time is higher than two minutes, it will cause the composite powder to be exposed to a static state for a long time, which may lead to unnecessary refinement of the composite powder, agglomeration or greater wear, and it may take a long time to reach the required motion state again during the restart, thus reducing the efficiency.

[0074] In some embodiments, in step X1, the rotational speed of the ball milling is 100 rpm to 150 rpm. In this way, it is beneficial to make the diamond particles evenly dispersed with low oxygen content, and at the same time make the particle size of the aluminum powder smaller. If the rotational speed of the ball milling is too low, the particle size of the composite powder will increase and the activity will decrease; if the rotational speed of the ball milling is too high, the wear of the ball milling tank will be aggravated, and at the same time the particle size of the diamond particles will decrease, resulting in an increase in the oxygen content in the obtained composite powder, which will have an adverse effect on the sintering of the diamond particle aluminum matrix composite powder and is not conducive to forming a stronger interface bond between the diamond particles and the aluminum matrix.

[0075] In some specific embodiments, the ball-to-material ratio of the ball milling is 2 to 3:1. In this way, it helps to improve the wear effect of aluminum powder and diamond particles during the ball milling process. A higher ball-to-material ratio can increase the number of impacts between the ball milling medium and the composite during the grinding process, and promote the refinement and uniform distribution of the composite powder; at the same time, the maximum value of the ball-to-material ratio is limited to avoid over-grinding, making the particles too small, thus reducing the probability of introducing impurity atoms such as oxygen atoms.

[0076] In some embodiments, in step X11, the liquid medium for wet ball milling is anhydrous ethanol. By using anhydrous ethanol, the composite powder can be further separated from the external environment to further prevent the oxidation of the composite powder; ethanol is volatile and can take away part of the heat of the composite powder during the wet ball milling process, which is beneficial to reducing the probability of cold welding and the like during the wet ball milling process; and when using anhydrous ethanol, it is convenient to dry the composite powder.

[0077] In some embodiments, in step X12, the ultrasonic dispersion time is 1 h to 4 h to ensure that the slurry formed by the liquid medium of the ball milling and the composite powder can be fully dispersed.

[0078] In some embodiments, in step X13, the initial temperature in the drying process is 30°C to 40°C, and the temperature is increased at a rate of 5°C to 8°C every 2h to 4h until the temperature reaches 50°C to 60°C, and then dried for 24h to 48h. In this way, by gradually increasing the temperature during the drying process, the temperature distribution of the composite powder can be made more uniform, stress concentration in the composite powder can be reduced, and the drying effect can be improved. Gradually increasing the temperature during the drying process is beneficial to reducing the sharp change in the surface and internal temperature of the composite powder, helping to reduce the accumulation of internal stress caused by uneven temperature during the drying process, and reducing the possibility of deformation or cracking of the composite powder; the gradient heating helps to remove moisture more evenly, avoiding cracking on the surface of the composite powder caused by too fast evaporation of local moisture, and at the same time improving the drying uniformity of the surface and inside of the composite powder, thereby optimizing the drying effect of the composite powder.

[0079] In some embodiments, in step X13, the vacuum degree of the vacuum environment is -0.1 MPa, and during the drying process, every 30 min to 40 min, the vacuum degree of the vacuum environment is pumped to -0.1 MPa again. During the drying process, since water and the liquid medium of wet ball milling will volatilize, the vacuum degree of the vacuum environment will decrease, affecting the drying speed and drying effect. Therefore, every 30 min to 40 min, pumping the vacuum degree of the vacuum environment to -0.1 MPa again helps to improve the drying speed and drying effect during the drying process.

[0080] The embodiment of the present invention also provides a diamond particle aluminum matrix composite material, including the diamond particle aluminum matrix composite material prepared by using the diamond particle aluminum matrix composite material preparation method described in any one of the above. The diamond particle aluminum matrix composite material provided by the embodiment of the present invention introduces diamond particles as reinforcing particles, which not only effectively exerts the excellent thermophysical properties of diamond, improves the thermal conductivity of the diamond particle aluminum matrix composite material, but also reduces the cost. The obtained diamond particle aluminum matrix composite material has high density and good interfacial bonding.

[0081] In some embodiments, the density of the diamond particle aluminum matrix composite material is greater than or equal to 98.5%, the thermal conductivity is 400 W / m·K to 470 W / m·K, and the coefficient of thermal expansion is 5.1×10 -6 K -1 ~11.0×10 -6 K -1 。

[0082] Hereinafter, the preparation method of the diamond particle aluminum matrix composite material provided by the present invention will be described in detail with reference to Examples 1 to 3.

[0083] Example 1

[0084] A) Take 72.8 g of aluminum powder with a purity above 99.95% and an average particle size of 25 microns, and 77.2 g of diamond particles with an average particle size of 200 μm. The volume ratio of aluminum powder to diamond particles is 11:9. Put the prepared raw material powder into an alumina ball milling tank, add 300 g of alumina ball milling beads, and use anhydrous ethanol as the ball milling medium with an addition amount of 1 / 2 of the volume of the ball milling tank. Use an alumina ball milling tank with a capacity of 1 L. After loading the raw material powder and anhydrous ethanol, seal it with a sealing bolt. After sealing, close the intake valve on the upper cover of the ball milling tank, open the exhaust valve, and use a small vacuum pump to evacuate the tank to a vacuum with a vacuum degree of -0.1 MPa. Then close the exhaust valve, connect the argon gas pipeline to the intake valve and open it, and fill the tank with high-purity argon until the internal and external air pressures are balanced. Next, open the exhaust valve and keep the argon gas discharging from the exhaust valve for 5 min. Repeat the above steps twice. After that, close the intake valve and exhaust valve of the ball milling tank, and install the ball milling tank on a QXQM-16 all-round planetary ball mill. Set the ball milling speed to 100 rpm and the total running time of the equipment to 6 h. Stop rotating for 1 min every 5 min of operation, and at the same time change the rotation direction from clockwise to counterclockwise; continue to run for 5 min, then stop rotating for 1 min and change to counterclockwise rotation. Refer to Figure 4 、 Figure 5 and Figure 6 , after wet ball milling by the method of Example 1, the diamond particles have a crushing effect on the aluminum powder, significantly reducing the particle size of the aluminum powder.

[0085] B) After the ball milling is completed, before use, first evacuate the glove box to a vacuum degree of -0.1 MPa, and then introduce high-purity argon until it is level with the external air pressure. Repeat this process twice to ensure that the oxygen content in the glove box is maintained at a low level. Open the ball milling tank in the inert gas glove box, and separate the anhydrous ethanol and the ball milling beads from the mixed raw material powder through a sieve. Place the separated anhydrous ethanol slurry in a stainless steel tray and put it into an ultrasonic cleaner in the glove box for 4 h of ultrasonic oscillation dispersion. Put the dispersed slurry into a small high-temperature vacuum drying oven in the glove box, evacuate the vacuum degree to -0.1 MPa, and set the heating temperature to 50 °C. Restart the mechanical pump every 1 h to restore the vacuum degree to -0.1 MPa for 6 h. When the vacuum degree no longer drops, introduce high-purity argon into the drying oven to balance to atmospheric pressure, turn off the heating function, take out the powder and put it into a vacuum bag to obtain aluminum-based composite powder without agglomeration and with uniform particle size.

[0086] C) First, open the intake valve of the vacuum hot-pressing sintering furnace. After the pressure inside the furnace is balanced with the outside, open the furnace door, take out the graphite mold and place it in a stainless-steel tray. Remove the mold liner, punch, and gasket, and spray boron nitride release agent on the inner wall of the liner and the surfaces of the punch and gasket that come into contact with the composite powder. After the alcohol in the release agent has completely evaporated, reassemble the liner, punch, and gasket into the graphite mold. Take out a small amount of composite powder from the vacuum bag and fill it into the mold liner of the graphite mold. The filling amount is 1 / 3 of the liner volume. Then place the graphite mold into the vacuum hot-pressing sintering furnace, turn on the vacuum pump, and evacuate the vacuum inside the furnace to 0 MPa. Close and fasten the furnace door. The vacuum hot-pressing sintering process is as follows: First, heat it at a heating rate of 10 °C / min to 300 °C, hold for 30 minutes, then apply a pressure of 25 MPa, and then increase the pressure to 55 MPa at a rate of 1 MPa / min while continuing to heat at a rate of 10 °C / min to 580 °C. After holding for 2 hours, stop heating and cool with the furnace. When the temperature drops to 400 °C, relieve the pressure and continue to cool with the furnace to room temperature to complete the sintering process. Refer to Figure 7 , the surface of the composite material obtained by the method of Example 1 is clean and tidy, without obvious holes. The diamond particles are evenly dispersed in the aluminum matrix, but most of the diamond particles protrude on the matrix surface. The density of the diamond particle aluminum matrix composite material is 99.16%, the thermal conductivity is 459 W / m·K, and the thermal expansion coefficient is 5.6×10 -6 K -1 -10.6×10 -6 K -1 .

[0087] Example 2

[0088] A) Take 72.8 g of aluminum powder with a purity above 99.95%, the average particle size is 25 microns, and 77.2 g of diamond particles with an average particle size of 200 μm. The volume ratio of aluminum powder to diamond particles is 11:9. Put the prepared raw material powder into an alumina ball mill tank, add 300 g of alumina ball milling beads, and use anhydrous ethanol as the ball milling medium, with the addition amount being 1 / 2 of the volume of the ball mill tank. Use an alumina ball mill tank with a capacity of 1 L. After loading the raw material powder and anhydrous ethanol, seal it with a sealing bolt. After sealing, close the intake valve on the upper cover of the ball mill tank, open the exhaust valve, and use a small vacuum pump to evacuate the tank to a vacuum with a vacuum degree of -0.1 MPa. Then close the exhaust valve, connect the argon gas pipeline to the intake valve and open it, and fill the tank with high-purity argon until the internal and external air pressures are balanced. Next, open the exhaust valve and keep the argon gas discharging from the exhaust valve for 5 min. Repeat the above steps twice. After that, close the intake valve and exhaust valve of the ball mill tank, and install the ball mill tank on a QXQM-16 all-round planetary ball mill. Set the ball milling speed to 100 rpm, and the total running time of the equipment is 6 h. Stop rotating for 1 min every 5 min of operation, and at the same time change the rotation direction from clockwise to counterclockwise; continue to run for 5 min, then stop rotating for 1 min, and change to counterclockwise rotation.

[0089] B) After the ball milling is completed, before use, first evacuate the glove box to a vacuum degree of -0.1 MPa, and then introduce high-purity argon until it is level with the external air pressure. Repeat this process twice to ensure that the oxygen content in the glove box is maintained at a low level. Open the ball mill tank in the inert gas glove box, and separate the anhydrous ethanol and ball milling beads from the mixed raw material powder through a sieve. Place the separated anhydrous ethanol slurry in a stainless steel tray and put it into the ultrasonic cleaner in the glove box for 4 h of ultrasonic oscillation dispersion. Put the dispersed slurry into a small high-temperature vacuum drying oven in the glove box, evacuate the vacuum degree to -0.1 MPa, and set the heating temperature to 50 °C. Restart the mechanical pump every 1 h to restore the vacuum degree to -0.1 MPa for 6 h. When the vacuum degree no longer drops, introduce high-purity argon into the drying oven, balance it to atmospheric pressure, turn off the heating function, take out the powder and put it into a vacuum bag, and a non-agglomerated and uniform particle size aluminum-based composite powder can be obtained.

[0090] C) First, open the intake valve of the vacuum hot-pressing sintering furnace. After the pressure inside the furnace is balanced with the outside, open the furnace door, take out the graphite mold and place it in a stainless steel tray. Take out the mold liner, punch, and gasket, and spray boron nitride release agent on the inner wall of the liner and the surfaces of the punch and gasket that come into contact with the composite powder. After the alcohol in the release agent has completely evaporated, reassemble the liner, punch, and gasket into the graphite mold. Take out a small amount of composite powder from the vacuum bag and fill it into the liner of the graphite mold, with the filling amount being 1 / 3 of the liner volume. Then place the graphite mold into the vacuum hot-pressing sintering furnace, turn on the vacuum pump, and evacuate the vacuum degree inside the furnace to 0 MPa. Close and fasten the furnace door. The vacuum hot-pressing sintering process is as follows: First, heat it at a heating rate of 10 °C / min to 300 °C, hold for 30 minutes, then apply a pressure of 25 MPa, and then increase the pressure to 50 MPa at a rate of 1 MPa / min while continuing to heat at a rate of 10 °C / min to 580 °C. After holding for 2 hours, stop heating and cool with the furnace. When the temperature drops to 400 °C, relieve the pressure and continue to cool with the furnace to room temperature to complete the sintering process. Refer to Figure 8 , there are a small number of pores at the surface of the composite material obtained in Example 2 and at the interface between the irregular diamond particles and the aluminum matrix. The density of the diamond particle aluminum matrix composite material is 98.96%, the thermal conductivity is 445 W / m·K, and the thermal expansion coefficient is 6.2×10 -6 K -1 ~10.9×10 -6 K -1 .

[0091] Example 3

[0092] A) Take 72.8 g of aluminum powder with a purity above 99.95% and an average particle size of 25 microns, and 77.2 g of diamond particles with an average particle size of 200 μm. The volume ratio of the aluminum powder to the diamond particles is 11:9. Put the prepared raw material powder into an alumina ball mill tank, add 300 g of alumina ball milling beads, and use anhydrous ethanol as the ball milling medium with an addition amount of 1 / 2 of the volume of the ball mill tank. Use an alumina ball mill tank with a capacity of 1 L. After loading the raw material powder and anhydrous ethanol, seal it with a sealing bolt. After sealing, close the intake valve on the upper cover of the ball mill tank, open the exhaust valve, and use a small vacuum pump to evacuate the tank to a vacuum with a vacuum degree of -0.1 MPa. Then close the exhaust valve, connect the argon gas pipeline to the intake valve and open it, and fill the tank with high-purity argon until the internal and external air pressures are balanced. Next, open the exhaust valve and keep the argon gas discharging from the exhaust valve for 5 min. Repeat the above steps twice. After that, close the intake valve and exhaust valve of the ball mill tank, and install the ball mill tank on a QXQM-16 all-round planetary ball mill. Set the ball milling speed to 100 rpm, and the total running time of the equipment is 6 h. Stop rotating for 1 min every 5 min of operation, and at the same time change the rotation direction from clockwise to counterclockwise; continue to run for 5 min, then stop rotating for 1 min and change to counterclockwise rotation.

[0093] B) After the ball milling is completed, before use, first evacuate the glove box to a vacuum degree of -0.1 MPa, and then introduce high-purity argon until it is level with the external air pressure. Repeat this process twice to ensure that the oxygen content in the glove box is maintained at a low level. Open the ball mill tank in the inert gas glove box, and separate the anhydrous ethanol and the ball milling beads from the mixed raw material powder through a sieve. Place the separated anhydrous ethanol slurry in a stainless steel tray and put it into an ultrasonic cleaner in the glove box for 4 h of ultrasonic oscillation dispersion. Put the dispersed slurry into a small high-temperature vacuum drying oven in the glove box, evacuate the vacuum degree to -0.1 MPa, and set the heating temperature to 50 °C. Restart the mechanical pump every 1 h to restore the vacuum degree to -0.1 MPa for 6 h. When the vacuum degree no longer drops, introduce high-purity argon into the drying oven to balance to the atmospheric pressure, turn off the heating function, take out the powder and put it into a vacuum bag, and a non-agglomerated and uniform particle size aluminum-based composite powder can be obtained.

[0094] C) First, open the intake valve of the vacuum hot-pressing sintering furnace. After the pressure inside the furnace is balanced with the outside, open the furnace door, take out the graphite mold and place it in a stainless-steel tray. Remove the mold liner, punch, and gasket, and spray boron nitride release agent on the inner wall of the liner and the surfaces of the punch and gasket that come into contact with the composite powder. After the alcohol in the release agent has completely evaporated, reassemble the liner, punch, and gasket into the graphite mold. Take out a small amount of composite powder from the vacuum bag and fill it into the liner of the graphite mold, with the filling amount being 1 / 3 of the liner volume. Then place the graphite mold into the vacuum hot-pressing sintering furnace, turn on the vacuum pump, and evacuate the vacuum degree inside the furnace to 0 MPa. Close and fasten the furnace door. The vacuum hot-pressing sintering process is as follows: First, heat it at a heating rate of 10 °C / min to 300 °C, hold for 30 minutes, then apply a pressure of 25 MPa, and then increase the pressure to 55 MPa at a rate of 1.5 MPa / min while continuing to heat at a rate of 10 °C / min to 580 °C. After holding for 2 hours, end the heating and cool it with the furnace. When the temperature drops to 400 °C, relieve the pressure and continue to cool with the furnace to room temperature to complete the sintering process. See Figure 9 , the surface of the composite material obtained in Example 3 is clean and tidy, without obvious holes. The diamond particles are evenly distributed in the aluminum matrix. The density of the diamond particle aluminum matrix composite material is 99.65%, the thermal conductivity is 465 W / m·K, and the thermal expansion coefficient at 25 °C - 300 °C is 5.1×10 -6 ·K -1 ~10.3×10 -6 ·K -1 .

[0095] Example 4

[0096] A) Take 72.8 g of aluminum powder with a purity above 99.95% and an average particle size of 25 microns, and 77.2 g of diamond particles with an average particle size of 200 microns. The volume ratio of the aluminum powder to the diamond particles is 11:9. Put the prepared raw material powder into an alumina ball mill tank, add 300 g of alumina ball mill beads, and use anhydrous ethanol as the ball milling medium with an addition amount of 1 / 2 of the volume of the ball mill tank. Use an alumina ball mill tank with a capacity of 1 L. After loading the raw material powder and anhydrous ethanol, seal it with a sealing bolt. After sealing, close the intake valve on the upper cover of the ball mill tank, open the exhaust valve, and use a small vacuum pump to evacuate the tank to a vacuum with a vacuum degree of -0.1 MPa. Then close the exhaust valve, connect the argon gas pipeline to the intake valve and open it, and fill the tank with high-purity argon until the internal and external air pressures are balanced. Next, open the exhaust valve and keep the argon gas discharging from the exhaust valve for 5 min. Repeat the above steps twice. After that, close the intake valve and exhaust valve of the ball mill tank, and install the ball mill tank on a QXQM-16 all-round planetary ball mill. Set the ball milling speed to 100 rpm and the total running time of the equipment to 6 h. Stop rotating for 1 min every 5 min of operation, and at the same time change the rotation direction from clockwise to counterclockwise; continue to operate for 5 min, then stop rotating for 1 min, and change to counterclockwise rotation.

[0097] B) After the ball milling is completed, before use, first evacuate the glove box to a vacuum degree of -0.1 MPa, and then introduce high-purity argon until it is equal to the external air pressure. Repeat this process twice to ensure that the oxygen content in the glove box is maintained at a low level. Open the ball mill tank in the inert gas glove box, and separate the anhydrous ethanol and the ball mill beads from the mixed raw material powder through a sieve. Place the separated anhydrous ethanol slurry in a stainless steel tray and put it into an ultrasonic cleaner in the glove box for 4 h of ultrasonic oscillation dispersion. Put the dispersed slurry into a small high-temperature vacuum drying oven in the glove box, evacuate the vacuum degree to -0.1 MPa, and set the heating temperature to 50 °C. Restart the mechanical pump every 1 h to restore the vacuum degree to -0.1 MPa for 6 h. When the vacuum degree no longer drops, introduce high-purity argon into the drying oven to balance to atmospheric pressure, turn off the heating function, take out the powder and put it into a vacuum bag to obtain an aluminum-based composite powder without agglomeration and with uniform particle size.

[0098] C) First, open the intake valve of the vacuum hot-pressing sintering furnace. After the pressure inside the furnace is balanced with the outside, open the furnace door, take out the graphite mold and place it in a stainless-steel tray. Take out the mold liner, punch, and gasket, and spray boron nitride release agent on the inner wall of the liner and the surfaces of the punch and gasket that come into contact with the composite powder. After the alcohol in the release agent has completely evaporated, reassemble the liner, punch, and gasket into the graphite mold. Take out a small amount of composite powder from the vacuum bag and fill it into the liner of the graphite mold, with the filling amount being 1 / 3 of the liner volume. Then place the graphite mold into the vacuum hot-pressing sintering furnace, turn on the vacuum pump, and evacuate the vacuum degree inside the furnace to 0 MPa. Close and fasten the furnace door. The vacuum hot-pressing sintering process is as follows: First, heat it at a heating rate of 10 °C / min to 300 °C, hold for 30 minutes, then apply a pressure of 25 MPa, and then increase the pressure to 55 MPa at a rate of 1.5 MPa / min while continuing to heat at a rate of 10 °C / min to 580 °C. After holding for 3 hours, end the heating and cool with the furnace. When the temperature drops to 400 °C, relieve the pressure and continue to cool with the furnace to room temperature to complete the sintering process. Refer to Figure 10 , the surface of the composite material obtained in Example 4 is overall clean and tidy, and there are also no obvious holes. The diamond particles are evenly distributed in the aluminum matrix. The density of the diamond particle aluminum matrix composite material is 99.02%, the thermal conductivity is 450 W / m·K, and the thermal expansion coefficient is 5.9×10 -6 ·K -1 ~10.8×10 -6 ·K -1 .

[0099] Example 5

[0100] A) Take 72.8 g of aluminum powder with a purity above 99.95% and an average particle size of 25 microns, and 77.2 g of diamond particles with an average particle size of 200 microns. The volume ratio of the aluminum powder to the diamond particles is 11:9. Put the prepared raw material powder into an alumina ball milling tank, add 300 g of alumina ball milling beads, and use anhydrous ethanol as the ball milling medium with an addition amount of 1 / 2 of the volume of the ball milling tank. Use an alumina ball milling tank with a capacity of 1 L. After loading the raw material powder and anhydrous ethanol, seal it with a sealing bolt. After sealing, close the intake valve on the upper cover of the ball milling tank, open the exhaust valve, and use a small vacuum pump to evacuate the tank to a vacuum with a vacuum degree of -0.1 MPa. Then close the exhaust valve, connect the argon gas pipeline to the intake valve and open it, and fill the tank with high-purity argon until the internal and external air pressures are balanced. Next, open the exhaust valve and keep the argon gas discharging from the exhaust valve for 5 min. Repeat the above steps twice. After that, close the intake valve and exhaust valve of the ball milling tank, and install the ball milling tank on a QXQM-16 all-round planetary ball mill. Set the ball milling speed to 100 rpm and the total running time of the equipment to 6 h. Stop rotating for 1 min every 5 min of operation, and at the same time change the rotation direction from clockwise to counterclockwise; continue to run for 5 min, then stop rotating for 1 min, and change to counterclockwise rotation.

[0101] B) After the ball milling is completed, before use, first evacuate the glove box to a vacuum degree of -0.1 MPa, and then introduce high-purity argon until it is level with the external air pressure. Repeat this process twice to ensure that the oxygen content in the glove box is maintained at a low level. Open the ball milling tank in the inert gas glove box, and separate the anhydrous ethanol and the ball milling beads from the mixed raw material powder through a sieve. Place the separated anhydrous ethanol slurry in a stainless steel tray and put it into an ultrasonic cleaner in the glove box for 4 h of ultrasonic oscillation dispersion. Put the dispersed slurry into a small high-temperature vacuum drying oven in the glove box, evacuate the vacuum degree to -0.1 MPa, and set the heating temperature to 50 °C. Restart the mechanical pump every 1 h to restore the vacuum degree to -0.1 MPa for 6 h. When the vacuum degree no longer drops, introduce high-purity argon into the drying oven to balance to the atmospheric pressure, turn off the heating function, take out the powder and put it into a vacuum bag to obtain an aluminum-based composite powder without agglomeration and with uniform particle size.

[0102] C) First, open the intake valve of the vacuum hot-pressing sintering furnace. After the pressure inside the furnace is balanced with the outside, open the furnace door, take out the graphite mold and place it in a stainless steel tray. Take out the mold liner, punch, and gasket, and spray boron nitride release agent on the inner wall of the liner and the surfaces of the punch and gasket that come into contact with the composite powder. After the alcohol in the release agent has completely evaporated, reassemble the liner, punch, and gasket into the graphite mold. Take out a small amount of composite powder from the vacuum bag and fill it into the mold liner of the graphite mold, with the filling amount being 1 / 3 of the liner volume. Then place the graphite mold into the vacuum hot-pressing sintering furnace, turn on the vacuum pump, and evacuate the vacuum degree inside the furnace to 0 MPa. Close and fasten the furnace door. The vacuum hot-pressing sintering process is as follows: First, heat it at a heating rate of 10 °C / min to 300 °C, keep it warm for 30 minutes, then apply a pressure of 25 MPa, and then increase the pressure to 55 MPa at a rate of 1.5 MPa / min while continuing to heat at a rate of 10 °C / min to 570 °C. After keeping it warm for 3 hours, stop heating and cool it with the furnace. When the temperature drops to 400 °C, relieve the pressure and continue to cool it with the furnace to room temperature to complete the sintering process. Refer to Figure 11 , the surface of the composite material obtained in Example 5 is relatively flat and clean, with very few large and obvious pores. The diamond particles are evenly distributed in the aluminum matrix. The density of the diamond particle aluminum matrix composite material is 98.82%, the thermal conductivity is 423 W / m·K, and the thermal expansion coefficient is 6.4×10 -6 ·K -1 ~10.9×10 -6 ·K -1 .

[0103] The above-described embodiments of the present invention do not constitute a limitation on the protection scope of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a diamond particle aluminum matrix composite material, characterized in that Including the steps: (X1) Wet ball milling, dispersing, and drying aluminum powder and diamond particles with preset volume fractions respectively to obtain diamond particle aluminum matrix composite powder; (X2) Vacuum hot pressing and sintering the diamond particle aluminum matrix composite powder obtained in step (X1). During the vacuum hot pressing and sintering process, gradient heating is carried out, and pressure is applied to the diamond particle aluminum matrix composite powder during the gradient heating process to obtain diamond particle aluminum matrix composite material.

2. The preparation method according to claim 1, characterized in that, Step (X2) specifically includes: (X21) First stage heating: Raise the temperature to 300°C - 400°C at a heating rate of 6°C / min - 10°C / min; (X22) First stage heat preservation: 10 min - 30 min; (X23) Second stage heating: Apply a pressure of 20 MPa - 25 Mpa to the diamond particle aluminum matrix composite powder, and then continue to raise the temperature to 500°C - 600°C at a rate of 8°C / min - 10°C / min. During the heating process, increase the pressure applied to the diamond particle aluminum matrix composite powder to 50 MPa - 55 MPa at a rate of 1 MPa / min - 1.5 MPa / min; (X24) Second stage heat preservation: Heat preservation for 1 h - 3 h; (X25) End heating, cool down. After cooling down to 400°C, stop applying pressure to the diamond particle aluminum matrix composite powder and continue to cool.

3. The preparation method according to claim 1, characterized in that, Step (X1) specifically includes: (X11) Wet ball milling aluminum powder and diamond particles with preset volume fraction ratios under a protective atmosphere to obtain composite powder. The wet ball milling specifically includes alternately rotating clockwise and counterclockwise for ball milling and stopping during the alternation; (X12) Place the composite powder obtained in step (X11) in a protective atmosphere for ultrasonic dispersion to obtain dispersed composite powder; (X13) Place the dispersed composite powder obtained in step (X12) in a vacuum environment for drying treatment to obtain the diamond particle aluminum matrix composite powder.

4. The preparation method according to claim 3, characterized in that, In step (X11), the duration of each clockwise rotation for ball milling and each counterclockwise rotation for ball milling is 3 min - 5 min respectively; the stopping time during the alternation is 1 min - 2 min, and the total time of the wet ball milling is 6 h.

5. The preparation method according to claim 3, characterized in that, In step (X11), the average particle size of the aluminum powder is 25 μm - 30 μm; the average particle size of the diamond particles is 200 μm - 250 μm.

6. The preparation method according to claim 3, wherein, The preset volume fraction ratio of the aluminum powder to the diamond particles is 10 - 11:10 - 9.

7. The preparation method according to claim 3, characterized in that, The rotation speed of the wet ball milling is 100 rpm - 150 rpm.

8. The preparation method according to claim 3, characterized in that, In step (X13), the initial temperature in the drying treatment is 30°C - 40°C, and the temperature is raised in a way that the temperature is increased by 5°C - 8°C every 2 h - 4 h until the temperature reaches 50°C - 60°C, and then dried for 24 h - 48 h.

9. A diamond particle aluminum matrix composite material, characterized in that, Including the diamond particle aluminum matrix composite material prepared by the method for preparing diamond particle aluminum matrix composite material according to any one of claims 1 - 8.

10. The diamond particle aluminum matrix composite material according to claim 9, wherein The density of the diamond particle aluminum matrix composite is greater than or equal to 98.5%, the thermal conductivity is 400 W / m·K to 470 W / m·K, and the coefficient of thermal expansion is 5.1×10 -6 ·K -1 ~11.0×10 -6 ·K -1 .

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