A method for near-net-shape forming of diamond / aluminum composites by pressureless infiltration

Abstract

The application relates to a method for preparing a diamond / aluminum composite material by a pressureless infiltration method, and relates to a method for preparing a diamond / aluminum composite material. The application aims at solving the problems of poor compactness and the influence of residual organic binder on thermal performance in the existing preparation of the diamond / aluminum composite material by the pressureless infiltration method. The method comprises the following steps: S1, preparing double-coated diamond powder; S2, preparing a diamond porous skeleton; and S3, pressureless infiltration of pure aluminum. The application is used for the pressureless infiltration method for near-net-shape forming of the diamond / aluminum composite material.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing diamond / aluminum composite material. BACKGROUND

[0002] Diamond / aluminum composite material and diamond / copper composite material are typical representatives of the fourth generation of thermal management materials, especially diamond / aluminum composite material has the characteristics of low density, similar thermal expansion coefficient to electronic device chip, and thermal conductivity up to 400W·m -1 ·K -1 The above has obtained preliminary application in the fields of integrated circuits, automobiles, aviation, etc.

[0003] At present, the general preparation process of diamond metal matrix composite material is divided into powder metallurgy and liquid phase infiltration. The traditional powder metallurgy method for preparing diamond / aluminum composite material has the problems of diamond particle agglomeration and aluminum powder diffusion difficulty, which is the main reason for the poor density of the composite material. Therefore, liquid phase infiltration is more suitable for forming diamond / aluminum composite material. Pressureless infiltration is a process that does not apply external pressure and relies on the capillary action of molten metal to spontaneously fill the gap between diamond particles. The general steps are: first, diamond particles are added with organic binder to prepare diamond preform, then porous diamond skeleton is obtained after degreasing, and then metal matrix is infiltrated. The aluminum ingot is heated to the molten state, and long time heat preservation is ensured to ensure that the infiltration process can be fully carried out. At present, the research on the preparation of diamond / aluminum composite material by pressureless infiltration at home and abroad is relatively less, and the commonly reported thermal conductivity value is 300W·(m·K) -1 The following is the poor density. This is because the wettability between diamond and aluminum or between the plating layer on the surface of diamond and aluminum is poor, and the molten aluminum cannot completely fill all the gaps between the diamond particles; in addition, a small amount of organic binder is left in the diamond skeleton after degreasing, which will eventually affect the thermal performance of the composite material. SUMMARY

[0004] The present application solves the problems of poor density and residual organic binder affecting thermal performance in the preparation of diamond / aluminum composite material by existing pressureless infiltration, and further provides a method for near-net-shape diamond / aluminum composite material by pressureless infiltration.

[0005] A method for near-net-shape diamond / aluminum composite material by pressureless infiltration, which is carried out according to the following steps:

[0006] I. Preparation of double-plated diamond powder:

[0007] ①A layer of metal or non-metal plating layer M is deposited on the surface of diamond particles to obtain plated diamond, and the surface plating layer of the plated diamond is carbonized to obtain diamond covered with carbide layer MC;

[0008] ②The diamond covered with carbide layer MC is sequentially subjected to sensitization treatment, water washing, surface activation treatment, water washing and drying, and finally placed in a chemical copper plating solution to form an outer plating layer Cu by chemical copper plating to obtain the Cu@MC double plating layer diamond;

[0009] The mass ratio of the diamond covered with carbide layer MC to the outer plating layer Cu in the Cu@MC double plating layer diamond is 1:(0.2-0.8);

[0010] II. Preparation of the diamond porous skeleton:

[0011] ①The Cu@MC double plating layer diamond and Sn powder are uniformly mixed to obtain a mixed powder, and the mixed powder is poured into a sintering mold to be sintered to obtain the diamond porous skeleton;

[0012] The mass ratio of the Cu@MC double plating layer diamond to the Sn powder is 100:(0.05-2);

[0013] ②The diamond porous skeleton is subjected to cold isostatic pressing to obtain a high diamond volume fraction diamond skeleton;

[0014] III. Pressureless infiltration of pure aluminum:

[0015] ①The high diamond volume fraction diamond skeleton is wrapped by Sn foil to obtain a wrapped skeleton, a pure aluminum block is covered on the upper surface or lower surface of the wrapped skeleton and placed in an infiltration mold to obtain a to-be-infiltrated piece, and the to-be-infiltrated piece is subjected to infiltration to obtain a formed piece;

[0016] Or the pure aluminum block is covered on the upper surface or lower surface of the high diamond volume fraction diamond skeleton, and a Sn powder layer is laid on the contact surface between the pure aluminum block and the high diamond volume fraction diamond skeleton, and then placed in an infiltration mold to obtain a to-be-infiltrated piece, and the to-be-infiltrated piece is subjected to infiltration to obtain a formed piece;

[0017] ②The formed piece is subjected to homogenization annealing to obtain a diamond / aluminum composite material.

[0018] The present application has the following beneficial effects:

[0019] 1. A method for preparing a diamond skeleton with a complex shape without adding an organic binder, that is, independent diamond particles are bonded to each other into a diamond skeleton with a certain porosity by means of sintering necks formed after sintering of the external copper plating layer of the diamond powder. The diamond porous skeleton is subjected to cold isostatic pressing to reduce the porosity of the diamond skeleton and further increase the diamond volume fraction of the formed piece.

[0020] 2. The diamond powder surface is evenly coated with a layer of copper, the diamond skeleton is pressureless infiltrated with aluminum, the copper on the surface of the diamond skeleton is completely wetted with the molten aluminum, which promotes the infiltration of the molten pure aluminum liquid to the diamond particles; in addition, the copper plating layer with a certain thickness ensures that adjacent diamond particles are separated by a certain gap width, and there is no problem of diamond particle agglomeration and uneven dispersion.

[0021] 3. Sn element has the characteristics of low melting point, small solid solubility in pure aluminum or aluminum alloy, high diffusion rate, and no reaction with Al, which not only effectively reduces the melting temperature of aluminum, but also reduces the transition temperature of aluminum from liquid phase to solid phase, so the Sn element can expand the liquid phase range of aluminum. In the pressureless infiltration process, the trace amount of Sn element attached to the surface of the diamond skeleton rapidly diffuses into the molten aluminum liquid, which can reduce the surface energy of the liquid phase, and the generated liquid phase can be maintained for a long time to promote the full infiltration, which helps to improve the density of the formed part.

[0022] 4. In the process of infiltration, the copper plating layer reacts with the molten aluminum to form aluminum-copper alloy phase Al2Cu. On the one hand, a proper amount of aluminum-copper alloy phase Al2Cu can significantly enhance the mechanical properties of the matrix; on the other hand, excessive aluminum-copper alloy phase Al2Cu reduces the thermal conductivity of the matrix, which easily leads to material brittleness. In the process of infiltration, Sn element tends to segregate to the Al-Cu interface, which is beneficial to break the network-like aluminum-copper alloy phase Al2Cu into dispersed particle phase. After homogenization annealing treatment, the residual part of the aluminum-copper alloy phase Al2Cu in the aluminum matrix can be effectively eliminated. Finally, the diamond / aluminum composite material with a specific shape is successfully prepared, the density reaches more than 96%, and the thermal conductivity can reach 400 W·m -1 ·K -1 ~ 550 W·m -1 ·K -1 . The low-cost, high-density, and near-net-shape diamond / aluminum composite material with complex shape can be realized.

[0023] The present application is a method for near-net-shape forming of diamond / aluminum composite material by pressureless infiltration. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a flowchart of the present application for near-net-shape forming of diamond / aluminum composite material by pressureless infiltration;

[0025] Figure 2 It is an SEM morphology diagram of the fracture of the diamond / aluminum composite material prepared in Example 1;

[0026] Figure 3 It is an XRD diagram of the fracture of the diamond / aluminum composite material, (a) is the diamond / aluminum composite material prepared in Example 1, and (b) is the diamond / aluminum composite material prepared in the comparative experiment. DETAILED DESCRIPTION

[0027] The technical solution of the present application is not limited to the following specific embodiments, but also includes any combination between the specific embodiments.

[0028] Specific embodiment one: combined with Figure 1 Specifically, the method for preparing a near-net-shape diamond / aluminum composite material by pressureless infiltration in this embodiment is carried out according to the following steps:

[0029] I. Preparation of double-coated diamond powder:

[0030] ①A layer of metal or non-metal coating M is deposited on the surface of the diamond particles to obtain coated diamond, and the surface coating of the coated diamond is carbonized to obtain diamond coated with a carbide layer MC;

[0031] ②The diamond coated with the carbide layer MC is sequentially subjected to sensitization treatment, water washing, surface activation treatment, water washing and drying, and finally placed in a chemical copper plating solution to form an outer copper coating Cu to obtain Cu@MC double-coated diamond;

[0032] The mass ratio of the diamond coated with the carbide layer MC to the outer copper coating Cu in the Cu@MC double-coated diamond is 1:(0.2-0.8);

[0033] II. Preparation of diamond porous skeleton:

[0034] ①The Cu@MC double-coated diamond and Sn powder are uniformly mixed to obtain a mixed powder, and the mixed powder is poured into a sintering mold to obtain a diamond porous skeleton;

[0035] The mass ratio of the Cu@MC double-coated diamond to the Sn powder is 100:(0.05-2);

[0036] ②The diamond porous skeleton is cold isostatic pressed to obtain a high-diamond-volume-fraction diamond skeleton;

[0037] III. Pressureless infiltration of pure aluminum:

[0038] ①The high-diamond-volume-fraction diamond skeleton is wrapped with Sn foil to obtain a wrapped skeleton, a pure aluminum block is covered on the upper surface or lower surface of the wrapped skeleton and placed in an infiltration mold to obtain a to-be-infiltrated piece, and the to-be-infiltrated piece is infiltrated to obtain a formed piece;

[0039] Alternatively, a pure aluminum block is covered on the upper surface or lower surface of the high-diamond-volume-fraction diamond skeleton, and a Sn powder layer is laid on the contact surface between the pure aluminum block and the high-diamond-volume-fraction diamond skeleton, and then placed in an infiltration mold to obtain a to-be-infiltrated piece, and the to-be-infiltrated piece is infiltrated to obtain a formed piece;

[0040] 2. Homogenizing annealing the shaped piece to obtain a diamond / aluminum composite material.

[0041] The beneficial effects of the present embodiment are:

[0042] 1. A method for preparing a diamond skeleton with complex shape without adding organic binder, i.e. relying on the sintering neck formed after sintering of the external copper plating layer of the diamond powder to bond the independent diamond particles to each other into a diamond skeleton with certain porosity. Cold isostatic pressing of the diamond porous skeleton can reduce the porosity of the diamond skeleton and further increase the diamond volume fraction of the shaped piece.

[0043] 2. The diamond powder is uniformly coated with a layer of copper, and the diamond skeleton is subjected to pressureless infiltration of aluminum. The copper on the surface of the diamond skeleton is completely wetted by the molten aluminum, promoting the infiltration of the molten pure aluminum into the diamond particles. In addition, the copper plating layer with a certain thickness ensures that adjacent diamond particles are separated by a certain gap width, and there is no problem of agglomeration and uneven dispersion of diamond particles.

[0044] 3. Sn element has the characteristics of low melting point, small solid solubility in pure aluminum or aluminum alloy, high diffusion rate, and no reaction with Al, which not only effectively reduces the melting temperature of aluminum, but also reduces the transition temperature of aluminum from liquid phase to solid phase, so Sn element can expand the liquid phase range of aluminum. During pressureless infiltration, the trace amount of Sn element attached to the surface of the diamond skeleton rapidly diffuses into the molten aluminum, which can reduce the surface energy of the liquid phase, and the generated liquid phase can be maintained for a long time to promote the full infiltration, which helps to improve the density of the shaped piece.

[0045] 4. During the infiltration process, the copper plating layer reacts with the molten aluminum to form aluminum-copper alloy phase Al2Cu. On the one hand, a proper amount of aluminum-copper alloy phase Al2Cu can significantly enhance the mechanical properties of the matrix; on the other hand, excessive aluminum-copper alloy phase Al2Cu reduces the thermal conductivity of the matrix, which easily leads to brittleness of the material. During the infiltration process, Sn element tends to segregate to the Al-Cu interface, which helps to break the network-like aluminum-copper alloy phase Al2Cu into dispersed particle phase. Homogenization annealing of the infiltrated piece can effectively eliminate a part of the residual aluminum-copper alloy phase Al2Cu in the aluminum matrix. Finally, a diamond / aluminum composite material with a specific shape is successfully prepared, with a density of more than 96% and a thermal conductivity of up to 400 W·m -1 ·K -1 ~ 550 W·m -1 ·K -1 , which can realize near-net-shaping of low-cost, high-density, and complex-shaped diamond / aluminum composite materials.

[0046] Specific embodiment two: the difference between this embodiment and the specific embodiment one is that the average particle size of the diamond particles in step 1 1 is 50 μm-400 μm. The others are the same as the specific embodiment one.

[0047] Specific embodiment three: the difference between this embodiment and the specific embodiment one or two is that a layer of metal or non-metal plating layer M is deposited on the surface of the diamond particles in step 1 1 by magnetron sputtering method, chemical plating, sol-gel method or salt bath plating; the plating layer M in step 1 1 is Ti plating layer, W plating layer, Cr plating layer, Si plating layer, Mo plating layer, B plating layer or Zr plating layer; the thickness of the plating layer M in step 1 1 is 50 nm-1 μm. The others are the same as the specific embodiment one or two.

[0048] Specific embodiment four: the difference between this embodiment and the specific embodiment one to three is that the coated diamond in step 1 1 is put into a vacuum atmosphere furnace, vacuumized to less than 10 -3 Pa, or the inert gas is passed at a flow rate of 20-30 sccm, the temperature is raised to 800-1200℃ at a temperature raising rate of 5-10℃ / min, and then the temperature is kept at 800-1200℃ for 1-4 h to obtain the diamond coated with carbide layer MC; the inert gas is nitrogen or argon. The others are the same as the specific embodiment one to three.

[0049] Specific embodiment five: the difference between this embodiment and the specific embodiment one to four is that the diamond coated with carbide layer MC in step 1 2 is sequentially subjected to sensitization treatment, water washing, surface activation treatment, water washing and drying, and finally put into a chemical copper plating solution to form an outer plating layer Cu by chemical copper plating at a temperature of 50-60℃ to obtain the Cu@MC double plating layer diamond.

[0050] The sensitization treatment is specifically that the diamond is added into a sensitization solution and stirred for 3-5 min; the sensitization solution is specifically prepared by the following steps: SnCl2 is dissolved in deionized water to obtain a SnCl2 solution with a concentration of 10-50 g / L, and then 10-20% dilute hydrochloric acid is added dropwise into the SnCl2 solution until the solution changes from white to clear.

[0051] The surface activation treatment is specifically that the diamond is added into an activation solution and stirred for 3-5 min; the activation solution is specifically prepared by the following steps: PbCl2 is dissolved in 35-36% concentrated hydrochloric acid, and then deionized water is added to dilute the PbCl2 concentration in the solution to 0.5-1.5 g / L.

[0052] The chemical copper plating solution is mixed by CuSO4·5H2O, 20%-40% HCHO aqueous solution, EDTA, C4O6H4KNa, bipyridine, potassium ferrocyanide and water, and the adding amount of CuSO4·5H2O in the chemical copper plating solution is 15g / L-20g / L, the adding amount of 20%-40% HCHO aqueous solution is 10mL / L-15mL / L, the adding amount of EDTA is 10g / L-15g / L, the adding amount of C4O6H4KNa is 10g / L-15g / L, the adding amount of bipyridine is 0.01g / L-0.02g / L, and the adding amount of potassium ferrocyanide is 0.005g / L-0.01g / L. The other steps are the same as those in the first to fourth embodiments.

[0053] Embodiment six: different from one of the first to fifth embodiments is that in step two ①, the Cu@MC double-plated diamond is mixed with Sn powder to obtain mixed powder, the mixed powder is poured into a sintering mold and vibrated, and then placed in a vacuum atmosphere furnace, vacuumized to a vacuum degree ≤10 Pa in the furnace, and then a reducing gas is introduced at a flow rate of 20-30sccm, heated to 800-1050℃ at a heating rate of 5-10℃ / min, and then kept at a sintering temperature of 800-1050℃ for 0.5-2h, and finally cooled to room temperature at a cooling rate of 5-10℃ / min and demolded to obtain a diamond porous skeleton; the Sn powder has a purity of 99.99% and an average particle size of 1-10μm; and the reducing gas is hydrogen or carbon monoxide. The other steps are the same as those in the first to fifth embodiments.

[0054] In the embodiment, hydrogen or carbon monoxide is introduced to prevent the Cu plating layer of the diamond powder from being oxidized in the high-temperature sintering process.

[0055] Embodiment seven: different from one of the first to sixth embodiments is that in step two ②, the diamond porous skeleton is wrapped in a rubber mold, and then placed in a cold isostatic pressing machine, kept at a pressure of 60-80MPa for 3-5min, and finally unloaded and demolded to obtain a diamond skeleton with a high diamond volume fraction. The other steps are the same as those in the first to sixth embodiments.

[0056] Embodiment eight: different from one of the first to seventh embodiments is that in step three ①, the infiltration is performed according to the following steps: the infiltrated part is placed in a vacuum atmosphere furnace, vacuumized to a vacuum degree ≤10 Pa in the furnace, and then a reducing gas is introduced at a flow rate of 20-30sccm, heated to 800-1050℃ at a heating rate of 5-10℃ / min, and then kept at a sintering temperature of 800-1050℃ for 0.5-2h, and finally cooled to room temperature at a cooling rate of 5-10℃ / min and demolded to obtain a diamond porous skeleton. The other steps are the same as those in the first to seventh embodiments. -3Pa, or argon gas is introduced at a flow rate of 20-30 seem, and the temperature is raised to 700-900℃ at a temperature raising rate of 10-20℃ / min, then the temperature is kept at 700-900℃ for 2-4h, and the temperature is cooled to room temperature in the furnace and the formed piece is demolded, the excess aluminum on the surface of the formed piece is removed by mechanical cutting or polishing, and the formed piece is obtained. The other steps are the same as those in Embodiment 1-7.

[0057] Embodiment 9: Different from any one of Embodiments 1-8, the volume ratio of the pure aluminum block to the high diamond volume fraction diamond skeleton in step 3(1) is 1:(1-2); the thickness of the Sn foil in step 3(1) is 0.01-0.03mm; and the thickness of the Sn powder layer in step 3(1) is 0.05-0.1mm. The other steps are the same as those in Embodiments 1-8.

[0058] Embodiment 10: Different from any one of Embodiments 1-9, the homogenizing annealing in step 3(2) is performed by the following steps: the formed piece is placed in a vacuum annealing furnace, argon gas is introduced at a flow rate of 20-30 seem, and the temperature is raised to 400-550℃ at a temperature raising rate of 5-10℃ / min, then the temperature is kept at 400-550℃ for 2-6h, and the temperature is cooled to room temperature in the furnace, and the diamond / aluminum composite material is obtained. The other steps are the same as those in Embodiments 1-9.

[0059] The beneficial effects of the present application are verified by the following examples:

[0060] Example 1:

[0061] A method for preparing a near-net shaped diamond / aluminum composite material by pressureless infiltration is performed by the following steps:

[0062] I. Preparation of double-coated diamond powder:

[0063] ①A Ti coating layer with a thickness of 200nm is deposited on the surface of the diamond particles by a magnetron sputtering method, and coated diamond is obtained. The coated diamond is placed in a vacuum atmosphere furnace, nitrogen gas is introduced at a flow rate of 20 seem, and the temperature is raised to 900℃ at a temperature raising rate of 10℃ / min, then the temperature is kept at 900℃ for 2h, and diamond coated with a carbide layer TiC is obtained; the average particle size of the diamond particles is 150μm;

[0064] ②The diamond coated with carbide layer TiC is sequentially subjected to sensitization treatment, water washing, surface activation treatment, water washing and drying, and finally placed in a chemical copper plating solution to form an outer plating layer Cu by chemical copper plating at a temperature of 55℃, thereby obtaining Cu@TiC double plating layer diamond;

[0065] The sensitization treatment specifically involves adding the diamond into a sensitization solution and stirring for 4 min; the sensitization solution is specifically prepared by the following steps: dissolving SnCl2 in deionized water to obtain a SnCl2 solution with a concentration of 30g / L, and then adding 10% dilute hydrochloric acid dropwise into the SnCl2 solution until the solution changes from white to clear;

[0066] The surface activation treatment specifically involves adding the diamond into an activation solution and stirring for 4 min; the activation solution is specifically prepared by the following steps: dissolving PbCl2 in 35% concentrated hydrochloric acid, and then adding deionized water to dilute the solution to a PbCl2 concentration of 1g / L;

[0067] The chemical copper plating solution is composed of CuSO4·5H2O, 37% HCHO aqueous solution, EDTA, C4O6H4KNa, bipyridine, potassium ferrocyanide and water, and the addition amounts of CuSO4·5H2O, 37% HCHO aqueous solution, EDTA, C4O6H4KNa, bipyridine and potassium ferrocyanide in the chemical copper plating solution are 20g / L, 10mL / L, 14g / L, 14g / L, 0.02g / L and 0.01g / L, respectively;

[0068] The mass ratio of the diamond coated with carbide layer TiC to the outer plating layer Cu in the Cu@TiC double plating layer diamond is 1:0.4;

[0069] II. Preparation of diamond porous skeleton:

[0070] ①The Cu@TiC double plating layer diamond and Sn powder are uniformly mixed to obtain a mixed powder, the mixed powder is poured into a sintering mold and vibrated, and then placed in a vacuum atmosphere furnace, vacuumized to a vacuum degree of 10Pa in the furnace, and then carbon monoxide is introduced at a flow rate of 20sccm, heated to 950℃ at a heating rate of 10℃ / min, then kept at a sintering temperature of 950℃ for 0.5h, finally cooled to room temperature at a cooling rate of 10℃ / min and demolded, thereby obtaining a diamond porous skeleton; the Sn powder has a purity of 99.99% and an average particle size of 10μm;

[0071] The mass ratio of the Cu@TiC double plating layer diamond to the Sn powder is 100:0.5;

[0072] ②putting the diamond porous skeleton into a rubber mold, and then placing it in a cold isostatic pressing machine, under the condition of 80 MPa pressure, keeping pressure for 5 min, and finally unloading and demolding to obtain a high diamond volume fraction diamond skeleton;

[0073] The volume percentage of diamond in the high diamond volume fraction diamond skeleton is 50%;

[0074] III. Pressureless infiltration of pure aluminum:

[0075] ① wrapping the high diamond volume fraction diamond skeleton by Sn foil to obtain a wrapped skeleton, covering a pure aluminum block on the lower surface of the wrapped skeleton and placing it in an infiltration mold to obtain a to-be-infiltrated piece, and then infiltrating the to-be-infiltrated piece to obtain a formed piece;

[0076] The volume ratio of the pure aluminum block to the high diamond volume fraction diamond skeleton is 1:2, and the thickness of the Sn foil is 0.02 mm;

[0077] The infiltration is specifically performed by the following steps: placing the to-be-infiltrated piece in a vacuum atmosphere furnace, vacuumizing to a vacuum degree of 10 -3 Pa in the furnace, under the condition of a heating rate of 15℃ / min, heating to 800℃, then keeping the temperature at 800℃ for 2h, cooling to room temperature with the furnace, demolding, removing the excess aluminum on the surface of the formed piece by mechanical cutting or polishing, and obtaining the formed piece;

[0078] ② placing the formed piece in a vacuum annealing furnace, passing argon gas at a flow rate of 20sccm, under the condition of a heating rate of 5 / min, heating to 500℃, then keeping the temperature at 500℃ for 2h, cooling to room temperature with the furnace, and obtaining a diamond / aluminum composite material.

[0079] Comparative experiment: the difference between the comparative experiment and Example 1 is that: in step two ①, the addition of Sn powder is cancelled; in step three ①, the use of Sn foil is cancelled; and step three ② is cancelled. The others are the same as Example 1.

[0080] It is tested that the density of the diamond / aluminum composite material prepared in the comparative experiment is 90%, the thermal conductivity is 306W·(m·K) -1 (according to the national standard GB / T22588-2008), and the three-point bending strength is 280MPa (according to the national standard GB / T232-2010);

[0081] It is tested that the density of the diamond / aluminum composite material prepared in Example 1 is 96%, the thermal conductivity is 400W·(m·K) -1The three-point bending strength is 320 MPa (tested according to the national standard GB / T232-2010), and the mechanical strength and thermodynamic properties are more excellent compared with the control experiment, which can meet the requirements of practical application.

[0082] Figure 2 The SEM morphology of the fracture of the diamond / aluminum composite material prepared in Example 1 is shown in the figure. As can be seen from the figure, the diamond particles in the composite material are well combined with the matrix, and the introduction of Sn effectively improves the density of the composite material.

[0083] Figure 3 The XRD graph of the fracture of the diamond / aluminum composite material is shown in the figure, (a) is the diamond / aluminum composite material prepared in Example 1, and (b) is the diamond / aluminum composite material prepared in the control experiment. As can be seen from the figure, the diamond / aluminum composite material prepared in the control experiment contains Al2Cu mechanical reinforcing phase, and does not contain the adverse intermediate phase Al4C3. After the diamond / aluminum composite material containing Sn element in Example 1 is subjected to homogenization annealing treatment, it is found that the characteristic diffraction peak intensity of the Al2Cu intermediate phase in the XRD graph of the fracture of the composite material is relatively reduced compared with the control experiment, which indicates that the introduction of trace Sn element can effectively regulate the influence of the content of Al2Cu mechanical reinforcing phase on the performance of the composite material.

Claims

1. A method of near-net shape diamond / aluminum composite by pressureless infiltration, characterized by It is carried out according to the following steps: I. Preparation of double-plated diamond powder: ①A plating layer M of metal is deposited on the surface of the diamond particles to obtain plated diamond, and the plated diamond is placed in a vacuum atmosphere furnace, vacuumed to a vacuum degree less than 10 -3 Pa, or inert gas is introduced at a flow rate of 20-30 sccm, and heated to 800-1200℃ at a heating rate of 5-10℃ / min, and then kept at a temperature of 800-1200℃ for 1-4h to obtain diamond coated with carbide layer MC. The plating layer M is a Ti plating layer; the thickness of the plating layer M is 50 nm-1 μm; The diamond coated with the carbide layer MC is subjected to sensitization treatment, water washing, surface activation treatment, water washing and drying in sequence, and finally placed in a chemical copper plating solution to form an outer plating layer Cu by chemical copper plating under the condition of a temperature of 50-60 DEG C, thereby obtaining Cu@MC double-plated diamond; The mass ratio of the diamond coated with the carbide layer MC to the outer plating layer Cu in the Cu@MC double-plated diamond is 1:(0.2-0.8); The sensitization treatment specifically comprises adding the diamond into a sensitization solution and stirring for 3-5 min; the sensitization solution is specifically prepared according to the following steps: SnCl2 is dissolved in deionized water to obtain a SnCl2 solution with a concentration of 10-50 g / L, and then 10-20% dilute hydrochloric acid is added dropwise into the SnCl2 solution until the solution changes from white to clear; The surface activation treatment specifically comprises adding the diamond into an activation solution and stirring for 3-5 min; the activation solution is specifically prepared according to the following steps: PbCl2 is dissolved in concentrated hydrochloric acid with a mass percentage of 35-36%, and then deionized water is added to dilute the solution to a PbCl2 concentration of 0.5-1.5 g / L; The chemical copper plating solution is prepared by mixing CuSO4.5H2O, 20-40% HCHO aqueous solution, EDTA, C4O6H4KNa, bipyridine, potassium ferrocyanide and water, and the addition amounts of the components in the chemical copper plating solution are as follows: CuSO4.5H2O 15-20 g / L, 20-40% HCHO aqueous solution 10-15 mL / L, EDTA 10-15 g / L, C4O6H4KNa 10-15 g / L, bipyridine 0.01-0.02 g / L, and potassium ferrocyanide 0.005-0.01 g / L; II. Preparation of diamond porous skeleton: The Cu@MC double-plated diamond and Sn powder are mixed uniformly to obtain a mixed powder, the mixed powder is poured into a sintering mold and vibrated, and then placed in a vacuum atmosphere furnace, vacuumized to a vacuum degree of less than or equal to 10 Pa, and then a reducing gas is introduced at a flow rate of 20-30 sccm, heated to 800-1050 DEG C at a heating rate of 5-10 DEG C / min, and then cooled to room temperature at a cooling rate of 5-10 DEG C / min and demolded after being kept at a sintering temperature of 800-1050 DEG C for 0.5-2 h, thereby obtaining a diamond porous skeleton; the Sn powder has a purity of 99.99% and an average particle size of 1-10 μm; and the reducing gas is hydrogen or carbon monoxide. The mass ratio of the Cu@MC double-coated diamond and the Sn powder is 100:(0.05-2). ②The diamond porous framework is wrapped in a rubber mold cover, and then is placed in a cold isostatic pressing machine under the condition that the pressure is 60-80 MPa, the pressure is maintained for 3-5 min, and finally the pressure is released and the product is taken out of the mold to obtain a high diamond volume fraction diamond framework; III. Pressureless infiltration of pure aluminum: ①The high diamond volume fraction diamond framework is wrapped with Sn foil to obtain a wrapped framework, a pure aluminum block is covered on the upper surface of the wrapped framework and placed in an infiltration mold to obtain a to-be-infiltrated piece, and the to-be-infiltrated piece is infiltrated to obtain a formed piece; or a pure aluminum block is covered on the upper surface of the high diamond volume fraction diamond framework, and a Sn powder layer is laid on the contact surface between the pure aluminum block and the high diamond volume fraction diamond framework, and then the to-be-infiltrated piece is placed in an infiltration mold to obtain a to-be-infiltrated piece, and the to-be-infiltrated piece is infiltrated to obtain a formed piece; The infiltration is specifically performed by the following steps: placing the to-be-infiltrated part in a vacuum atmosphere furnace, vacuumizing the furnace to a vacuum degree ≤10 -3 Pa, or argon gas is introduced at a flow rate of 20-30 seem, the temperature is raised to 700-900 DEG C at a temperature raising rate of 10-20 DEG C / min, then the temperature is kept at 700-900 DEG C for 2-4 hours, the furnace is cooled to room temperature, the part is demolded, the excess aluminum on the surface of the part is removed by mechanical cutting or polishing, and the formed part is obtained. ②The formed piece is placed in a vacuum annealing furnace, argon gas is introduced at a flow rate of 20-30 sccm, the temperature is raised to 400-550℃ at a rate of 5-10℃ / min, then the temperature is maintained at 400-550℃ for 2-6 h, and the furnace is cooled to room temperature to obtain a diamond / aluminum composite material.

2. A method of near net shape diamond / aluminum composite by pressureless infiltration according to claim 1, characterized in that The average particle size of the diamond particles in step 1 ① is 50-400 μm.

3. A method of near net shape diamond / aluminum composite by pressureless infiltration according to claim 1, characterized in that The inert gas in step 1 ① is nitrogen or argon.

4. A method of near net shape diamond / aluminum composite by pressureless infiltration according to claim 1, characterized in that The volume ratio of the pure aluminum block to the high diamond volume fraction diamond framework in step III ① is 1:(1-2); the thickness of the Sn foil in step III ① is 0.01-0.03 mm; and the thickness of the Sn powder layer in step III ① is 0.05-0.1 mm.

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