A method for preparing diamond / copper composite materials using electron beam powder bed melting

Abstract

This invention provides a method for preparing diamond / copper composite materials using electron beam powder bed melting, aiming to solve the problem that the high hardness and difficulty in subsequent machining of diamond / copper composite materials limit their engineering applications. The method includes: metallizing the surface of diamond particles and mixing them with copper powder to obtain diamond / copper-based composite powder; and selectively melting the composite powder layer by layer using electron beam powder bed melting technology. During the forming process, the melting behavior of the copper-based powder, the stability of the molten pool, the coating state of the diamond particles, and the degree of interfacial reaction between the diamond and the copper matrix are adjusted by controlling the electron beam defocusing amount, beam current, scanning speed, and linear energy. Under suitable process conditions, the copper powder can fully melt and effectively coat the metallized diamond particles, while forming a carbide-containing interfacial transition layer between the diamond particles and the copper matrix, thereby improving the density, thermal conductivity, hardness, and wear resistance of the composite material.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology of metal matrix composites, specifically relating to a method for preparing diamond-reinforced copper matrix composites by electron beam powder bed melting based on the synergistic control of defocusing amount and linear energy, and its application. Background Technology

[0002] With the rapid development of artificial intelligence technology and high-performance computing equipment, the heat generated by high-performance chips and related electronic devices during operation has increased significantly, placing higher demands on thermal management materials. To meet the service requirements under high power density and high heat flux density conditions, thermal management materials typically need to simultaneously possess high thermal conductivity, low coefficient of thermal expansion, good thermal stability, and certain mechanical properties and wear resistance.

[0003] Copper possesses high intrinsic thermal conductivity and good electrical conductivity, making it a commonly used metallic material in thermal management. However, pure copper has limited hardness and wear resistance, making it difficult to meet the synergistic requirements of high thermal conductivity and high reliability under high loads, complex contacts, and long-term service environments. Diamond, with its extremely high intrinsic thermal conductivity, low coefficient of thermal expansion, and excellent hardness, is an ideal reinforcing phase for improving the heat transfer capacity and mechanical properties of copper-based composites. Diamond-reinforced copper-based composites have significant application potential in electronic packaging, heat sinks, heat dissipation substrates, and thermal management of high-power devices. However, the addition of diamond particles significantly increases the hardness and processing difficulty of the composite material, limiting subsequent machining after preparation using traditional casting, powder metallurgy, hot pressing sintering, or melt infiltration methods, which is detrimental to the manufacturing and engineering applications of complex-shaped components.

[0004] Additive manufacturing technology enables the near-net-shape fabrication of complex components through layer-by-layer forming, providing a new technological path for the structural design and processing of diamond-reinforced copper-based composites. Electron beam powder bed melting (EBM) technology, performed in a vacuum environment, boasts high energy efficiency and good processing adaptability for high thermal conductivity metals, making it suitable for forming copper-based composites. However, in the EBM forming process of diamond / copper composite powders, powder melting behavior, molten pool stability, diamond particle coating state, particle dispersion uniformity, and interfacial reaction degree are all highly sensitive to the electron beam energy input. Insufficient electron beam energy input leads to incomplete melting of the copper-based powder, making it difficult for diamond particles to be fully coated by the molten copper matrix, resulting in unfused pores and interfacial defects within the material. Excessive electron beam energy input can cause copper matrix evaporation, molten pool fluctuations, splashing, particle disturbance, diamond thermal damage, and excessive interfacial reactions. The electron beam offset affects the beam spot size, energy density, and molten pool temperature field on the powder bed surface, while the linear energy directly affects the energy input per unit length of the scanning path. Therefore, offset and linear energy are important process parameters for controlling powder melting, melt pool stability and interfacial reactions.

[0005] Therefore, there is an urgent need to provide a preparation method that combines metallized diamond particles, copper-based powder systems, electron beam offset, and linear energy window to achieve stable forming, interface optimization, and overall performance improvement of diamond-reinforced copper-based composite materials. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing diamond-reinforced copper matrix composites by electron beam powder bed melting based on the synergistic control of defocusing amount and linear energy. This method improves the coating state and dispersion uniformity of diamond particles in the copper matrix by combining surface metallization treatment of diamond particles, electron beam offset defocusing amount control, and linear energy window control. It also adjusts the degree of interfacial reaction between diamond and the copper matrix, reduces interfacial defects and interfacial thermal resistance, thereby improving the density, thermal conductivity, hardness, and wear resistance of the composite material. This provides an effective approach for the net-shape forming of complex-shaped diamond / copper materials.

[0007] A method for preparing diamond / copper composite materials using electron beam powder bed melting. The method is characterized by the following preparation steps: (1) Spherical pure Cu powder was prepared by gas atomization; (2) W is coated by magnetron sputtering using diamond particles with a particle size of 50-100 μm; (3) Mix pure Cu powder and coated diamond particles in a certain proportion; (4) The diamond / copper-based composite powder is laid on the forming platform of an electron beam powder bed melting device, and the powder bed is preheated in a vacuum environment. Subsequently, by adjusting the electron beam accelerating voltage, beam current, scanning speed, layer thickness, linear energy, and electron beam offset, the diamond / copper-based composite powder is selectively melted layer by layer, so that the copper-based powder melts and coats the diamond particles with metal coating on the surface. After layer-by-layer powder laying and layer-by-layer melting, a diamond-reinforced copper-based composite material or a diamond-reinforced copper-based component is obtained.

[0008] Furthermore, the method for preparing diamond / copper composite material by electron beam melting is characterized in that the target material used for magnetron sputtering in step (2) is a tungsten target material with a coating thickness of 250-700 nm.

[0009] Furthermore, the method for preparing diamond / copper composite material by electron beam melting is characterized in that the volume fraction of diamond particles in the composite powder in step (3) is 10-40 vol.%.

[0010] Furthermore, the method for preparing diamond / copper composite materials by electron beam melting is characterized in that, during the electron beam melting process in step (4), the electron beam accelerating voltage is 60-80 kV, the beam current is 12-20 mA, the scanning speed is 4-8 m / s, the layer thickness is 0.05-0.08 mm, and the powder bed preheating temperature is 300-400 ℃. Based on the electron beam accelerating voltage, beam current, and scanning speed, the linear energy range is 90-300 J / m.

[0011] Furthermore, the method for preparing diamond / copper composite materials by electron beam melting is characterized in that the electron beam defocusing amount in step (4) is expressed by the offset parameter in the electron beam powder bed melting equipment, with the unit being V. The offset parameter changes the beam spot size, energy input per unit area, and molten pool temperature field distribution of the electron beam acting on the powder bed surface by adjusting the position of the electron beam focus relative to the powder bed surface. The offset parameter is from +0.1 V to -0.25 V. Under negative defocusing conditions, the electron beam energy density is higher than that under positive defocusing conditions, which is beneficial for the full melting of copper-based powder, the formation of a stable molten pool, and the effective coating of metallized diamond particles by the copper matrix.

[0012] The basic principle of this invention lies in the following: This invention utilizes the regulatory effect of a W coating on the effective specific gravity, dispersion stability, and interfacial reaction of diamond particles, combined with the advantages of efficient melting and layer-by-layer accumulation of Cu-based powders by electron beam powder bed melting, to achieve synergistic control of uniform diamond particle distribution, effective interfacial bonding, and high-density composite material forming. On one hand, this invention employs a W coating to perform surface metallization modification on diamond particles. Due to the high density of W, the coating thickness of 250-700 nm is designed to be relatively large, which can, to a certain extent, increase the effective specific gravity of the metallized diamond particles in the copper-based powder system, reducing the tendency for agglomeration and uneven dispersion between diamond particles and Cu powder due to density differences. Therefore, during powder mixing, powder spreading, and subsequent melting and forming processes, the W-coated diamond particles can be more stably distributed in the copper-based powder system and the molten pool, which is beneficial for obtaining diamond / Cu composite materials with more uniform particle dispersion and more stable microstructure. Simultaneously, the W coating can react in situ with the carbon on the diamond surface during electron beam melting, forming an interfacial transition layer containing WC compounds between the diamond particles and the Cu matrix. This improves the interfacial bonding between diamond and Cu and reduces interfacial defects. On the other hand, electron beam powder bed melting technology is performed in a vacuum environment, and the electron beam energy input is well-suited to Cu-based powders. By controlling the electron beam current, scanning speed, linear energy, and defocusing amount, the Cu-based powder can be fully melted to form a stable molten pool, thereby improving sample density and reducing defects such as unfused porosity, interfacial debonding, and insufficient melting. Compared with traditional powder metallurgy, hot pressing sintering, or melt infiltration methods, electron beam powder bed melting employs a layer-by-layer powder laying, selective melting, and cumulative forming process. It does not rely on complex molds and extensive subsequent machining, enabling near-net-shape manufacturing of high-hardness diamond / Cu composite materials and providing a technological basis for the fabrication of heat sinks, heat dissipation substrates, and other complex-shaped thermal management components.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses electron beam powder bed melting technology to prepare diamond-reinforced copper-based composite materials, which can realize near-net-shape manufacturing of diamond-reinforced copper-based composite materials or components, reducing the difficulty of subsequent processing caused by the increase in material hardness in traditional processing methods.

[0014] 2. This invention modifies the surface of diamond particles by designing a 250-700 nm W coating, thereby increasing the effective specific gravity of metallized diamond particles in the copper-based powder system, improving the dispersion stability of diamond particles during powder mixing, spreading, and melting and forming, reducing the tendency of particle segregation and local agglomeration, making the diamond particles more uniformly distributed in the Cu matrix, which is conducive to forming a continuous and stable heat transfer path and improving the microstructure uniformity and thermal conductivity of the composite material.

[0015] 3. This invention achieves the adjustment of electron beam spot size, energy input per unit area, and molten pool temperature field by designing electron beam offsets of +0.1 V, -0.1 V, -0.15 V, -0.2 V, and -0.25 V. This allows control over the melting behavior of copper-based powder, molten pool stability, diamond particle coating state, and interfacial reaction degree. Under offset conditions of -0.15 to -0.2 V, copper-based powder can fully melt and stably coat metallized diamond particles, while forming a continuous or semi-continuous carbide-containing interfacial transition layer, which is beneficial for reducing interfacial thermal resistance and improving the thermal conductivity of composite materials. Attached Figure Description

[0016] Figure 1 The electron beam current of this invention is 20 mA and the scanning speed is 6 m·s. -1 Furthermore, the scanning electron microscope (SEM) morphology of tungsten-copper / diamond composite material prepared by electron beam melting under the condition of defocusing amount of -0.2 V. Detailed Implementation

[0017] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific implementation examples. Figure 1 This is a typical technical roadmap of the present invention.

[0018] Example 1: Diamond particles were selected as the reinforcing phase, and their surfaces were subjected to W metallization treatment to obtain diamond particles with a W coating. The diamond particles had a particle size of approximately 70 μm, and the W coating thickness was 300 nm. The pure copper powder had a particle size range of 53-105 μm, with a D50 of 75.9 μm. The W-coated diamond particles were mixed with Cu powder to obtain a diamond / Cu composite powder, wherein the volume fraction of diamond particles in the composite material was 15 vol.%.

[0019] The obtained composite powder was placed in an electron beam powder bed melting apparatus, and preheated and selectively melted layer by layer under vacuum. During the forming process, the accelerating voltage was 60 kV, the beam current was 20 mA, the scanning speed was 6 m / s, the layer thickness was 0.05 mm, the preheating temperature was 400 ℃, and the defocusing amount was -0.2 V. Figure 1 The image shows a scanning electron microscope (SEM) image of the sample. The thermal conductivity of the resulting composite material reaches 491.32 W·m. - ¹·K - ¹ It is 25% higher than pure copper, while its hardness is increased by 43% and its wear rate is reduced by 94%.

[0020] Example 2: The same W-coated diamond particles and Cu powder as in Example 1 were used, except that the volume fraction of diamond particles in the composite material was 20 vol.%. During the forming process, the accelerating voltage was 60 kV, the beam current was 20 mA, the scanning speed was 8 m / s, the layer thickness was 0.05 mm, the preheating temperature was 400 ℃, and the defocusing amount was -0.25 V. The resulting composite material achieved a thermal conductivity of 451 W·m⁻¹·K⁻¹.

Claims

1. A method for preparing diamond / copper composite materials using electron beam powder bed melting, characterized in that, Includes the following steps: 1) The surface of diamond particles is subjected to tungsten (W) metallization treatment to obtain diamond particles with a tungsten metal coating on the surface; 2). The diamond particles with a tungsten coating on their surface are mixed with pure copper (Cu) powder to obtain a composite powder of diamond and copper; 3). The diamond / copper composite powder is laid on the forming platform of an electron beam powder bed melting device, and the diamond / copper composite powder is preheated in a vacuum environment; 4) By adjusting the electron beam accelerating voltage, beam current, scanning speed, layer thickness, line energy, and electron beam offset, the diamond / copper composite powder is selectively melted layer by layer to finally obtain the diamond / copper composite material.

2. The method according to claim 1, characterized in that, The diamond particles have a diameter of 50-100 μm, and the selected W metal coating has a thickness of 250-700 nm.

3. The method according to claim 1, characterized in that, Pure Cu powder was prepared by gas atomization, with a particle size of 53-105 μm.

4. The method according to claim 1, characterized in that, The volume fraction of the diamond particles in the composite material is 10-40 vol.%.

5. The method according to claim 1, characterized in that, The unit of the electron beam offset is V. The offset is used to adjust the position of the electron beam focus relative to the powder bed surface, thereby changing the beam spot size, energy input per unit area, and molten pool temperature field distribution of the electron beam acting on the powder bed surface. Its adjustment range is +0.1 V to -0.25 V.

6. The method according to claim 1, characterized in that, The accelerating voltage during the electron beam powder bed melting process is 60-80 kV, the beam current is 12-20 mA, the scanning speed is 4-8 m / s, the layer thickness is 0.05-0.08 mm, and the preheating temperature is 300-400 ℃.

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