Diamond / aluminum-based composite material with gradient Si-Al alloy coating and preparation method and application of diamond / aluminum-based composite material

Abstract

The invention discloses a gradually-changed Si-Al alloy coating diamond / aluminum-based composite material and a preparation method and application thereof, and the gradually-changed Si-Al alloy coating diamond / aluminum-based composite material is composed of an aluminum matrix and modified diamond evenly dispersed in the aluminum matrix. The modified diamond comprises diamond particles and a gradually-changed Si-Al alloy coating wrapping the surfaces of the diamond particles, in the gradually-changed Si-Al alloy coating, the mass fraction of Si is linearly decreased from 100% to 0% from inside to outside, and the mass fraction of Al is linearly increased from 0% to 100% from 0%. According to the method, the Si-Al alloy coating with gradually-changed and controllable components is constructed on the surface of the diamond, so that a SiC transition layer with strong binding force can be formed with the diamond, the gradient gradient coating is formed from inside to outside, internal stress can be released, good metallurgical bonding with an aluminum matrix can be achieved, formation of an Al4C3 phase is inhibited, and therefore the performance of the composite material is remarkably improved.

Description

Technical Field

[0001] The present invention relates to a gradient Si-Al alloy coated diamond / aluminum matrix composite material, a preparation method thereof and an application thereof, and belongs to the technical field of diamond / aluminum matrix composite material preparation. Background Art

[0002] With the continuous development of electronic technology, the power density of electronic components has been increasing continuously, generating more and more heat. At the same time, the requirement for material lightweight is becoming increasingly urgent. Commonly used thermal conductive materials can no longer meet the needs of the rapid development of current electronic technology. Developing new high thermal conductivity materials with higher thermal conductivity to dissipate the heat generated by semiconductors in time and ensure the normal working temperature of power components has become the key to the development of the electronic industry. The diamond / aluminum composite material not only has the characteristics of high thermal conductivity and low expansion, but also its density (2.9 - 3.2 g / cm 3 ) is much lower than other commonly used high thermal conductivity materials. Therefore, the diamond / aluminum composite material is the most promising new type of thermal management material in the future.

[0003] Due to the strong chemical inertness and large surface energy of diamond, its wetting angle with aluminum is greater than 90° even at high temperatures, and there is interfacial incompatibility between diamond and aluminum. In addition, diamond is extremely easy to react with aluminum to form Al4C3 during the preparation process. This interfacial product can react with water vapor, acids and alkalis, resulting in a significant decline in material properties. Starting from the interface, improving the interfacial incompatibility between diamond and aluminum and inhibiting the formation of Al4C3 are crucial for improving the comprehensive properties of the composite material. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the first object of the present invention is to provide a gradient Si-Al alloy coated diamond / aluminum matrix composite material. The gradient Si-Al alloy coated diamond / aluminum matrix composite material of the present invention has excellent thermal conductivity, mechanical properties and thermal shock resistance.

[0005] The second object of the present invention is to provide a preparation method of the gradient Si-Al alloy coated diamond / aluminum matrix composite material. The preparation method of the present invention is simple and controllable.

[0006] The third object of the present invention is to provide an application of the gradient Si-Al alloy coated diamond / aluminum matrix composite material.

[0007] In order to achieve the above objects, the present invention adopts the following technical solutions:

[0008] The present invention provides a gradient Si-Al alloy coated diamond / aluminum matrix composite material. The gradient Si-Al alloy coated diamond / aluminum matrix composite material is composed of an aluminum matrix and modified diamonds uniformly dispersed in the aluminum matrix. The modified diamonds include diamond particles and a gradient Si-Al alloy coating coated on the surface of the diamond particles. In the gradient Si-Al alloy coating, the mass fraction of Si linearly decreases from 100% to 0% from the inside to the outside, and the mass fraction of Al linearly increases from 0% to 100%.

[0009] For the gradient Si-Al alloy coated diamond / aluminum matrix composite material provided by the present invention, by constructing a Si-Al alloy coating with controllable gradient components on the surface of the diamond, it can not only form a SiC transition layer with strong bonding force with the diamond, and the gradient gradient coating formed from the inside to the outside helps to release internal stress, but also achieve good metallurgical bonding with the aluminum matrix, inhibit the formation of Al4C3 phase, thereby significantly improving the thermal conductivity, mechanical properties and thermal shock resistance of the composite material.

[0010] The gradient Si-Al alloy coating provided in the present invention has the characteristic of linear gradient. Through the linear gradient change, the progressive release of stress distribution can be realized, and the coefficient of thermal expansion gradually transitions from diamond (1×10 -6 / K) to the aluminum matrix (23×10 -6 / K), reducing the interfacial thermal mismatch stress by 60%; more than 90% of the residual stress is absorbed by the gradient buffer layer to prevent the coating from cracking. At the same time, the thermal mechanical properties are matched through the composition gradient: the number of thermal shock cycles is increased.

[0011] In a preferred embodiment, the volume fraction of the modified diamonds in the gradient Si-Al alloy coated diamond / aluminum matrix composite material is 45-85%.

[0012] In a preferred embodiment, the thickness of the gradient Si-Al alloy coating is 100-400 nm. Controlling the coating thickness within the scope of the present invention results in the optimal performance of the finally obtained composite material.

[0013] In a preferred embodiment, in the gradient Si-Al alloy coating, the atomic percentage of Si is 60-90 at%, and the atomic percentage of Al is 10-40 at%.

[0014] In the present invention, the atomic percentages of Si and Al in the gradient Si-Al alloy coating need to be effectively controlled. If the atomic percentage of Si is too small, the amount of SiC formed by the reaction of Si with C during inward segregation will be small, which is unfavorable for the bonding force of the material and affects the overall performance; if the atomic percentage of Si is too large, the amount of SiC formed will be large, and the excessive thickness of SiC will increase the interfacial thermal resistance and lead to a decrease in thermal diffusion performance.

[0015] Preferably, the particle size range of the diamond particles is 50 - 800 μm.

[0016] Preferably, the aluminum matrix is selected from one of pure aluminum and aluminum alloys.

[0017] The present invention also provides a method for preparing a gradient Si - Al alloy - coated diamond / aluminum - matrix composite material: a gradient Si - Al rough coating is deposited on the surface of diamond particles by dual - target magnetron co - sputtering, and then the diamond particles with the gradient Si - Al rough coating are heat - treated to obtain modified diamond with a gradient Si - Al alloy coating. The modified diamond and an aluminum source are infiltrated and compounded by isostatic pressing in a vacuum gas to obtain the gradient Si - Al alloy - coated diamond / aluminum - matrix composite material.

[0018] In the preparation method of the present invention, the magnetron dual - target co - sputtering technology is adopted. By adjusting the power ratio of the Si target and the Al target, a gradient Si - Al rough coating with linear gradient characteristics is obtained. Then, heat treatment is carried out. During the heat treatment process, Al reacts with diamond to form the Al4C3 phase, Si segregates inward and reacts with diamond to produce the SiC phase, Si segregates inward and reacts with Al4C3 to form SiC and Al, and the displaced Al segregates to the outer side of the coating. That is, through heat treatment, Al segregates outward and Si segregates inward. Through heat treatment, on the one hand, it promotes the solid - phase diffusion bonding at the interface of the Si - Al alloy - coated diamond, and on the other hand, due to the inevitable small sputtering deviation during magnetron sputtering, heat treatment can further adjust the gradient structure and form a continuous network structure, improving the thermal conductivity.

[0019] Preferably, the diamond particles are first ultrasonically cleaned with an organic solvent and then subjected to plasma activation treatment in sequence.

[0020] Further preferably, the organic solvent is selected from one of acetone, methyl butanone, and methyl isobutyl ketone.

[0021] Further preferably, during the plasma activation treatment, Ar gas plasma is used, the power is 150 - 250 W, and the treatment time is 10 - 45 min.

[0022] When performing magnetron multi - target co - sputtering on diamond particles, ultrasonic cleaning and plasma activation treatment are first carried out on them. Through plasma activation treatment, on the one hand, it can further remove organic pollutants, oxide layers, and other impurities on the material surface. In addition, by plasma bombardment, the physical and chemical properties of the material surface are changed, increasing the surface energy and surface reaction activity, improving the wettability and adhesiveness of the material, thereby enhancing the bonding force and stability between the coating and the substrate.

[0023] Preferably, the process of dual-target magnetron co-sputtering deposition is as follows: Set the power of the Si target to 500 - 1000 W, then linearly decrease it at a rate of 50 - 200 W / min until the power of the Si target reaches 0. Set the power of the Al target to 0, and then linearly increase it at a rate of 40 - 160 W / min until the power of the Al target reaches 400 - 800 W. The time for dual-target magnetron co-sputtering deposition is 5 - 10 min.

[0024] In the present invention, by regulating the power of dual-target magnetron co-sputtering deposition, on the one hand, a linear change is formed, and on the other hand, the atomic percentages of Si and Al are within the scope of the present invention.

[0025] Preferably, during the dual-target magnetron co-sputtering deposition, the temperature of the diamond particles is maintained at 200 - 300 °C.

[0026] Further preferably, before the dual-target magnetron co-sputtering deposition, the Si target is used for sputtering for 0.5 - 2 min. After the dual-target magnetron co-sputtering deposition is completed, the Al target is used for sputtering for 0.5 - 1 min.

[0027] The inventors found that by first depositing a silicon overcoat, silicon and diamond form silicon carbide, which is beneficial for interface bonding. If a silicon-aluminum coating is directly co-sputtered, it further avoids the presence of some aluminum on the diamond surface, which then reacts with diamond to form an aluminum-carbon tetra-phase, which is not conducive to interface bonding; sputtering the aluminum matrix after co-sputtering can also achieve better bonding.

[0028] Preferably, the heat treatment is carried out in a mixed atmosphere of Ar and H2. The temperature of the heat treatment is 750 - 1100 °C, the holding time is 1 - 3 h, and the heating rate is 10 - 30 °C / min;

[0029] In the mixed atmosphere, the volume ratio of Ar to H2 is 70 - 90:10 - 30.

[0030] In the present invention, the heat treatment is carried out in a mixed atmosphere of Ar and H2. By incorporating a small amount of H2, the surface oxides are reduced and the oxidation tendency of Al is decreased, thereby improving the properties of the composite material.

[0031] Further preferably, the process of the heat treatment is as follows: First, heat up at a heating rate of 10 - 15 °C / min to 300 - 600 °C, then heat up at a heating rate of 20 - 25 °C / min to 500 - 900 °C, and finally heat up at a heating rate of 26 - 30 °C / min to 750 - 1100 °C.

[0032] In the present invention, the performance of the finally obtained composite material is optimal through gradient heating. First, the temperature is slowly increased at a rate of 10-15 °C / min to promote the solid-phase diffusion bonding at the interface between the Si-Al alloy coating and diamond. Silicon migrates inward to form silicon carbide with carbon, and at the same time, residual gases (such as H2O, CO2) are removed. Then, the heating rate is increased to 20-25 °C / min. This stage triggers partial liquid-phase sintering, enhancing the metallurgical bonding between the coating and the substrate and avoiding thermal stress concentration caused by too rapid heating. Finally, the temperature is rapidly increased to the target temperature at a rate of 25-30 °C / min. Liquid-phase sintering is used to densify the material, while reducing the precipitation amount of Al4C3 (whose thermal conductivity is only 1 / 10 of that of diamond), and accelerating the migration of Al atoms to form a continuous network structure, thereby improving the thermal conductivity.

[0033] In the present invention, due to the low thermal conductivity of Al4C3, on the one hand, a gradient Si-Al thick coating with linear gradient characteristics is first obtained by magnetron sputtering, so that during the heat treatment process, the linear gradient can more precisely regulate the interfacial reaction. A diffusion barrier is formed through the gradient distribution of Si elements to reduce the C / Al contact probability. Combined with the temperature regulation during the heat treatment process, the generation amount of the Al4C3 phase can be suppressed to be controllable below 0.5 vol%. If the gradient Si-Al thick coating with linear gradient characteristics is not obtained by magnetron sputtering first, the uncontrollable gradient structure can reach more than 5%.

[0034] In a preferred embodiment, the process of infiltrating and compounding the modified diamond and the aluminum source by vacuum gas isostatic pressing is as follows: First, the modified diamond is loaded into a mold sleeve, and then the aluminum source is placed above the mold sleeve. After evacuating to a pressure ≤ 0 Pa, it is heated to 700-900 °C to melt the aluminum alloy, and then a protective gas of 2-12 MPa is filled, and the pressure is maintained for 30-90 min.

[0035] In a preferred embodiment, the process of infiltrating and compounding the modified diamond and the aluminum source by vacuum gas isostatic pressing is as follows: The modified diamond is loaded into a mold sleeve, and then the aluminum source is placed in a molten aluminum crucible. The mold sleeve is suspended above the molten aluminum crucible. After evacuating to a pressure ≤ 0 Pa, it is heated to 700-900 °C to melt the aluminum alloy, and then the mold sleeve is immersed in the molten aluminum crucible. Then, a protective gas of 2-12 MPa is filled, and the pressure is maintained for 30-90 min.

[0036] According to the above two methods, the composite material is prepared by the vacuum gas isostatic pressing process, and the pores can be fully removed under high pressure, making the composite material have a high density.

[0037] The present invention also provides an application of the gradient Si-Al alloy coating diamond / aluminum matrix composite material, and the gradient Si-Al alloy coating diamond / aluminum matrix composite material is applied to a high heat flux density semiconductor chip heat sink.

[0038] Beneficial effects

[0039] The present invention provides a gradient Si-Al alloy coated diamond / aluminum matrix composite material. By constructing a Si-Al alloy coating with controllable gradient components on the surface of the diamond, a SiC transition layer with strong bonding force can be formed with the diamond, and a gradient coating formed from the inside to the outside helps to release internal stress. At the same time, it can achieve good metallurgical bonding with the aluminum matrix and inhibit the formation of the Al4C3 phase, thereby significantly improving the thermal conductivity, mechanical properties and thermal shock resistance of the composite material.

[0040] The present invention adopts an innovative solution of multi-target co-sputtering technology and vacuum heat treatment to prepare the gradient coating. Compared with traditional methods such as electroplating and chemical vapor deposition, it has the advantages of simple process, low pollution and good controllability of coating composition. By precisely controlling the power ratio of Si and Al targets and vacuum heat treatment, continuous gradient changes of coating components can be achieved, avoiding the problem of stress concentration at the interface of traditional single-component coatings.

[0041] In addition, the present invention adopts a vacuum gas isostatic pressing infiltration process to prepare the composite material. Compared with traditional methods such as die casting and powder metallurgy, it can fully remove pores under high pressure and obtain a composite material with higher density and better performance. Specific embodiments

[0042] Example 1

[0043] Diamond particles with a particle size of 550 μm were first ultrasonically cleaned with acetone, and then treated with Ar gas plasma. The power was controlled at 250 W to perform plasma activation treatment on the diamond particles for 45 min. The power of the Si target was set at 800 W, and then decreased at a linear rate of 160 W / min until the power of the Si target reached 0. The power of the Al target was set at 0, and then increased at a linear rate of 100 W / min until the power of the Al target reached 500 W. The deposition time of dual-target magnetron co-sputtering was 5 min. The temperature of the diamond particles was maintained at 300 °C, and a silicon-aluminum coating was deposited on the surface of the diamond particles by magnetron multi-target co-sputtering. The diamond particles with the silicon-aluminum coating were heat-treated in a mixed atmosphere of argon and hydrogen (80:20). The heating rate was 10 °C / min, the temperature was 900 °C, and the holding time was 1 hour. After the heat treatment, modified diamonds with a gradient Si-Al alloy coating were obtained. Then, the modified diamonds and pure aluminum ingots were prepared so that the volume fraction of the modified diamonds in the gradient Si-Al alloy coating diamond / aluminum matrix composite was 60%. The modified diamonds with the gradient Si-Al alloy coating were placed in a mold sleeve, and then the aluminum ingot was placed in a molten aluminum crucible. The mold sleeve was suspended above the molten aluminum crucible. After evacuating to 0 Pa, it was heated to 850 °C to melt the aluminum ingot, and then the mold sleeve was immersed in the molten aluminum crucible, and 12 MPa of gas was filled and held for 60 min to achieve densification, and a gradient Si-Al alloy coating diamond / aluminum matrix composite was obtained.

[0044] In the gradient Al-Si alloy coating obtained in Example 1, the atomic percentage of Si was 70 at% and the atomic percentage of Al was 30 at%. The gradient Si-Al alloy coating diamond / aluminum matrix composite obtained in Example 1 was tested. The thermal conductivity was 750 W / m·k, the flexural property was 380 MPa, and the thermal shock resistance was -50 - 150 °C, 100 cycles, and the performance only decreased by 0.5%.

[0045] Example 2

[0046] Diamond particles with a particle size of 550 μm were first ultrasonically cleaned with acetone, and then treated with Ar gas plasma. The power was controlled at 250 W to perform plasma activation treatment on the diamond particles for 45 min. The power of the Si target was set at 700 W, and then decreased at a linear rate of 140 W / min until the power of the Si target reached 0. The power of the Al target was set at 0, and then increased at a linear rate of 80 W / min until the power of the Al target reached 400 W. The deposition time of dual-target magnetron co-sputtering was 5 min. Before the dual-target magnetron co-sputtering deposition, the Si target was sputtered alone for 1 min. After the dual-target magnetron co-sputtering deposition, the Al target was sputtered continuously for 1 min. The temperature of the diamond particles was maintained at 300 °C, and a silicon-aluminum coating was deposited on the surface of the diamond particles by magnetron sputtering. The diamond particles with the silicon-aluminum coating were heat-treated in a mixed atmosphere of argon and hydrogen (80:20). The heating rate was 10 °C / min, the temperature was 850 °C, and the holding time was 1 hour. After the heat treatment, modified diamonds with a gradient Si-Al alloy coating were obtained. Then, the modified diamonds and aluminum ingots were prepared, and the volume fraction of the modified diamonds in the gradient Si-Al alloy coating diamond / aluminum matrix composite was 60%. The modified diamonds with the gradient Si-Al alloy coating were loaded into a mold jacket, and the aluminum matrix was placed in a molten aluminum crucible. The mold jacket was suspended above the molten aluminum crucible. After evacuating to 0 Pa, it was heated to 850 °C to melt the aluminum ingot, and then the mold jacket was immersed in the molten aluminum crucible, and 12 MPa gas was filled and the pressure was maintained for 60 min to achieve densification. The obtained gradient Si-Al alloy coating diamond / aluminum matrix composite had a thermal conductivity of 760 W / m·k, a flexural strength of 370 MPa, and a thermal shock resistance of -50 - 150 °C for 100 cycles, with a performance degradation of 0.3%.

[0047] Example 3

[0048] Other conditions were the same as those in Example 1, except that the heat treatment process was as follows: first, it was heated to 400 °C at a heating rate of 10 °C / min, then heated to 700 °C at a heating rate of 20 °C / min, and finally heated to 900 °C at a heating rate of 30 °C / min. The obtained gradient Si-Al alloy coating diamond / aluminum matrix composite had a thermal conductivity of 780 W / m·k, a flexural strength of 390 MPa, and a thermal shock resistance of -50 - 150 °C for 100 cycles, with a performance degradation of 0.1%.

[0049] Comparative Example 1

[0050] Other conditions were the same as those in Example 1, except that the diamond particles were not subjected to plasma activation treatment. The obtained diamond / aluminum matrix composite had a thermal conductivity of 650 W / m·k, a flexural strength of 300 MPa, and a thermal shock resistance of -50 - 150 °C for 100 cycles, with a performance degradation of 2%.

[0051] Comparative Example 2

[0052] Other conditions are the same as those in Example 1, except that no aluminum-silicon alloy coating is applied on the surface of diamond particles. The obtained diamond / aluminum matrix composite has a thermal conductivity of 600 W / m·K, a flexural strength of 290 MPa, and a thermal shock resistance of -50 - 150 °C for 100 cycles, with a performance degradation of 8%.

[0053] Comparative Example 3

[0054] Other conditions are the same as those in Example 1, except that no aluminum-silicon coating is applied on the surface of diamond particles, but a tungsten coating is applied instead. The obtained diamond / aluminum matrix composite has a thermal conductivity of 650 W / m·K, a flexural strength of 300 MPa, and a thermal shock resistance of -50 - 150 °C for 100 cycles, with a performance degradation of 5%.

[0055] Comparative Example 4

[0056] Other conditions are the same as those in Example 1, except that no heat treatment is carried out. The obtained composite has a thermal conductivity of 660 W / m·K, a flexural strength of 300 MPa, and a thermal shock resistance of -50 - 150 °C for 100 cycles, with a performance degradation of 1%.

[0057] Comparative Example 5

[0058] Other conditions are the same as those in Example 1, except that single-target magnetron sputtering is used. The power of the Si-Al alloy target (atomic percentage of Si is 70 at% and atomic percentage of Al is 30 at%) is 150 w, the sputtering time is 8 min, and the temperature of diamond particles is maintained at 300 °C. The obtained gradient Si-Al alloy coating diamond / aluminum matrix composite has a thermal conductivity of 700 W / m·K, a flexural strength of 360 MPa, and a thermal shock resistance of -50 - 150 °C for 100 cycles, with a performance degradation of 1%.

Claims

1. A gradient Si-Al alloy coated diamond / aluminum-based composite material, characterized in that: The gradient Si-Al alloy coating diamond / aluminum-based composite material consists of an aluminum matrix and modified diamonds uniformly dispersed in the aluminum matrix, wherein the modified diamonds include diamond particles and a gradient Si-Al alloy coating coated on the surface of the diamond particles, wherein the mass fraction of Si in the gradient Si-Al alloy coating decreases linearly from 100% to 0% from the inside to the outside, and the mass fraction of Al increases linearly from 0% to 100%.

2. The gradient Si-Al alloy coated diamond / aluminum-based composite material according to claim 1, characterized in that: The volume fraction of the modified diamond in the gradient Si-Al alloy coating diamond / aluminum-based composite material is 45-85%.

3. The gradient Si-Al alloy coated diamond / aluminum-based composite material according to claim 1, characterized in that: The thickness of the gradient Si-Al alloy coating is 100-400 nm; In the gradient Si-Al alloy coating, the atomic percentage of Si is 60-90 at%, and the atomic percentage of Al is 10-40 at%; The particle size of the diamond particles ranges from 50 to 800 μm; The aluminum matrix is ​​selected from pure aluminum or aluminum alloy.

4. The method for preparing a gradient Si-Al alloy coated diamond / aluminum-based composite material according to any one of claims 1 to 3, characterized in that: A gradient Si-Al rough coating is obtained on the surface of diamond particles by dual-target magnetron sputtering deposition, and then the diamond particles containing the gradient Si-Al rough coating are heat treated to obtain modified diamond containing a gradient Si-Al alloy coating, and the modified diamond is compounded with an aluminum source by vacuum gas isostatic infiltration to obtain a gradient Si-Al alloy coated diamond / aluminum-based composite material.

5. The method for preparing a gradient Si-Al alloy coated diamond / aluminum-based composite material according to claim 4, characterized in that: The diamond particles are first subjected to organic solvent ultrasonic cleaning and plasma activation treatment in sequence; The organic solvent is selected from one of acetone, methyl butyl ketone and methyl isobutyl ketone; During the plasma activation treatment, Ar gas plasma is used, the power is 150-250W, and the treatment time is 10-45min.

6. The method for preparing a gradient Si-Al alloy coated diamond / aluminum-based composite material according to claim 4, characterized in that: The process of the dual-target magnetron sputtering deposition is as follows: the power of the Si target is set to 500-1000W, then reduced at a linear speed of 50-200W / min until the power of the silicon target is 0, the power of the Al target is set to 0, then increased at a linear speed of 40-160W / min until the power of the Al target is 400-800W, and the time of the dual-target magnetron co-sputtering deposition is 5-10min; During the dual-target magnetron co-sputtering deposition, the temperature of the diamond particles is maintained at 200-300° C.; Before dual-target magnetron co-sputtering deposition, Si target material is first sputtered for 0.5-2 minutes. After dual-target magnetron co-sputtering deposition is completed, Al target material is sputtered for 0.5-1 minute.

7. The method for preparing a gradient Si-Al alloy coated diamond / aluminum-based composite material according to claim 4, characterized in that: The heat treatment is carried out in a mixed atmosphere of Ar and H2, the heat treatment temperature is 750-1100°C, the holding time is 1-3h, and the heating rate is 10-30°C / min; In the mixed atmosphere, the volume ratio of Ar to H2 is 70-90:10-30.

8. The method for preparing a gradient Si-Al alloy coated diamond / aluminum-based composite material according to claim 7, characterized in that: The heat treatment process is: firstly heating to 300-600°C at a heating rate of 10-15°C / min, then heating to 500-900°C at a heating rate of 20-25°C / min, and finally heating to 750-1100°C at a heating rate of 26-30°C / min.

9. The method for preparing a gradient Si-Al alloy coated diamond / aluminum-based composite material according to claim 4, characterized in that: The process of compounding the modified diamond and the aluminum source by vacuum gas isostatic infiltration is as follows: first, the modified diamond is loaded into the mold sleeve, and then the aluminum source is placed above the mold sleeve, and after vacuuming to a pressure of ≤0 Pa, the aluminum alloy is heated to 700-900°C to melt, and then 2-12MPa protective gas is filled in, and the pressure is maintained for 30-90 minutes; or The process of compounding the modified diamond and the aluminum source by vacuum gas isostatic infiltration is as follows: the modified diamond is loaded into a mold sleeve, and then the aluminum source is placed in a molten aluminum crucible, the mold sleeve is suspended above the molten aluminum crucible, and after evacuating to a pressure of ≤0Pa, it is heated to 700-900°C to melt the aluminum alloy, and then the mold sleeve is immersed in the molten aluminum crucible, and then filled with 2-12MPa protective gas and maintained at pressure for 30-90min.

10. The use of a gradient Si-Al alloy coated diamond / aluminum-based composite material according to any one of claims 1 to 3, characterized in that: The gradient Si-Al alloy coating diamond / aluminum-based composite material is applied to a high heat flux density semiconductor chip heat sink.