A high thermal conductivity magnesium-diamond composite material and its preparation method

Abstract

This invention discloses a high thermal conductivity magnesium-diamond composite material and its preparation method, belonging to the field of metal matrix composites. The method includes: roughening the surface of a magnesium or magnesium alloy matrix; preparing a diamond suspension and impregnating the matrix; anchoring diamond particles to the roughened surface of the matrix via ultrasonic embedding; preheating at 250-350℃, followed by hot rolling at 280-320℃ with a deformation of 20%-70%; and finally, stress-relief annealing and finishing. This invention employs a low-temperature solid-state composite process, completely avoiding harmful interfacial reactions between magnesium and diamond; the combination of roughening and ultrasonic embedding ensures uniform dispersion and firm anchoring of diamond particles; and hot rolling achieves dense encapsulation and strong interfacial bonding of the particles. The prepared composite material has a diamond volume fraction of 5%-40%, a thermal conductivity ≥400W / m·K (up to 650W / m·K), and a density ≤2.3g / cm³. 3 Furthermore, the process is simple and the cost is controllable, making it suitable for heat dissipation of high-end electronic devices and easy to mass-produce.

Description

Technical Field

[0001] This invention relates to the field of metal matrix composites, specifically to a high thermal conductivity composite material with magnesium or magnesium alloy as the matrix and artificial single-crystal diamond micropowder as the reinforcing phase, and its preparation method. This composite material is particularly suitable for applications with extremely high requirements for heat dissipation efficiency and lightweighting, such as aerospace electronic devices, new energy vehicle heat dissipation modules, and 5G base station power amplifiers. Background Technology

[0002] Magnesium and its alloys are characterized by their low density (1.74-1.81 g / cm³). 3 With its advantages such as high strength and specific strength, magnesium has become an ideal lightweight substrate in high-end manufacturing. However, the thermal conductivity of pure magnesium (approximately 150-160 W / m·K) is insufficient to meet the heat dissipation requirements of modern high-power-density electronic devices. Diamond, as the material with the highest thermal conductivity in nature (>1000 W / m·K), is the ultimate reinforcing phase for improving the thermal conductivity of metal matrix composites.

[0003] Currently, the mainstream technologies for preparing magnesium-diamond composite materials (such as powder metallurgy and melt infiltration) have significant drawbacks:

[0004] 1) The process is usually carried out at high temperature (≥600℃), which leads to a severe interfacial reaction between the magnesium matrix and diamond, generating brittle magnesium carbide (Mg2C3) phase, which destroys the interfacial bonding and blocks the heat conduction path.

[0005] 2) High volume fraction diamond particles are prone to agglomeration in the matrix, resulting in poor dispersion uniformity and unstable composite material performance (fluctuation coefficient often exceeds 20%).

[0006] 3) The complex process, high equipment requirements, and expensive production costs (approximately RMB 8,000 / kg) severely restrict its large-scale application.

[0007] Therefore, developing a magnesium-diamond composite material preparation technology that can effectively suppress harmful interfacial reactions, achieve highly uniform dispersion of the reinforcing phase, and is simple and cost-controllable has become the core breakthrough point for the industrialization of this field. Summary of the Invention

[0008] I. Technical problems to be solved

[0009] The present invention aims to overcome the defects of the prior art, such as severe interfacial reaction, uneven dispersion of reinforcing phase, complex process and high cost, and provides a high thermal conductivity magnesium-diamond composite material and its preparation method that has simple process, excellent interfacial bonding, and synergistic optimization of thermal conductivity and lightweight.

[0010] II. Technical Solution

[0011] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0012] (I) A method for preparing a high thermal conductivity magnesium-diamond composite material, characterized by comprising the following steps:

[0013] Substrate pretreatment: Select pure magnesium foil / plate or magnesium alloy (such as AZ31, ZK60, AM60, AZ91D, etc.) foil / plate with a thickness of 0.5-2mm as the substrate, and use sandblasting, wire brush mechanical grinding or chemical etching to roughen at least one surface to achieve a surface roughness Ra of 1.5-5.0μm, forming a micron-level uneven structure.

[0014] Diamond suspension preparation and impregnation: Select synthetic single-crystal diamond powder with a particle size of 1-50μm, disperse it in a volatile liquid medium such as deionized water, ethanol, isopropanol or ethyl acetate, and add a dispersant (such as polyethylene glycol, sodium dodecylbenzenesulfonate, Span-80, etc.) accounting for 0.1-0.5wt% of the total mass of the suspension. After ultrasonic dispersion for 10-20 minutes, prepare a uniform suspension with a solid content of 5-40 vol%. Immerse the roughened magnesium matrix completely or partially in the suspension and soak for 5-15 minutes.

[0015] Ultrasonic embedding: Apply ultrasonic vibrations with a power of 500-2000W to an immersed magnesium substrate for 1-30 minutes. Utilize the microjets generated by the ultrasonic cavitation effect and the mechanical impact force to force the artificial single-crystal diamond particles in the suspension into the micron-level uneven structure on the substrate surface, achieving preliminary mechanical anchoring.

[0016] Preheating and hot rolling composite: The magnesium matrix embedded with diamond particles is placed in a heating device (such as a resistance furnace) and heated to 250-350℃, held for 10-30 minutes; then immediately hot rolled on a two-roll mill, with the rolling temperature controlled at 280-320℃, the deformation at 20%-70%, and the rolling speed at 0.3-1.0 m / min. Through the thermoplastic flow of the matrix at low temperature, a dense encapsulation of the diamond particles is achieved, forming a strong and tough metallurgical-mechanical composite interface.

[0017] Post-processing: The hot-rolled composite material is subjected to stress-relief annealing (150-200℃, held for 1-2 hours), and then mechanical finishing (such as leveling and cutting) to obtain the finished product.

[0018] (II) A high thermal conductivity magnesium-diamond composite material prepared by the above method, characterized in that:

[0019] The composite material consists of a magnesium or magnesium alloy matrix and artificial single-crystal diamond particles embedded in at least one surface layer of the matrix. The diamond has a volume fraction of 5%-40% and is uniformly dispersed in the surface layer of the matrix, with a dispersion uniformity variation coefficient ≤8%. No brittle magnesium carbide (Mg2C3) is formed at the interface.

[0020] This composite material exhibits the following excellent properties: planar thermal conductivity at room temperature ≥400 W / m·K, with a maximum of 650 W / m·K; density ≤2.3 g / cm³. 3 Interfacial shear strength ≥ 25 MPa; flexural strength ≥ 280 MPa; fracture toughness ≥ 12 kJ / m 2 .

[0021] III. Beneficial Effects

[0022] Compared with the prior art, the present invention has the following significant advantages:

[0023] Effective suppression of interfacial reactions: This invention employs a low-temperature (≤350℃) solid-phase composite process, which is far below the temperature threshold (approximately 450℃) at which magnesium and diamond react significantly. This fundamentally avoids the formation of brittle magnesium carbide (Mg2C3), ensuring the integrity of the thermal conductivity pathway and the strength of the interfacial bonding.

[0024] Highly uniform phase dispersion: By combining "surface roughening pretreatment" with "ultrasonic encapsulation," diamond particles are pre-fixed to the matrix surface using the mechanical anchoring principle, and then densely encapsulated through subsequent hot rolling. This method effectively prevents the agglomeration of diamond particles during the composite process, keeping the coefficient of variation of dispersion uniformity below 8%, and significantly improving the stability of material properties.

[0025] Simple process and low cost: The entire process is streamlined, requiring no complex vacuum or high-pressure equipment. The main processes (ultrasonic and hot rolling) are easily achievable through continuous and large-scale production. Compared to traditional powder metallurgy, production costs can be reduced by more than 50% (e.g., to approximately 3800 RMB / kg).

[0026] Excellent overall performance: The prepared composite material maintains the lightweight advantage of magnesium alloy (density ≤ 2.3 g / cm³). 3 At the same time, it achieves a leap in thermal conductivity (≥400W / m·K) and also has good mechanical properties (flexural strength ≥280MPa), meeting the structural-functional integrated application requirements in harsh heat dissipation scenarios. Attached Figure Description

[0027] Figure 1 This is a process flow diagram of the preparation method of the present invention. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0029] The performance testing methods are as follows: thermal conductivity was tested using the laser flare method (refer to GB / T 22588-2008); interfacial shear strength was tested using the nanoindentation method; and the uniformity of diamond particle dispersion was determined by statistically calculating the coefficient of variation from SEM images.

[0030] Example 1 (Basic Scheme)

[0031] Substrate pretreatment: AZ31 magnesium alloy plate with dimensions of 100mm×100mm×1mm was selected and subjected to double-sided sandblasting with 200-mesh quartz sand. The surface roughness Ra was measured to be 3.2μm.

[0032] Suspension preparation: Artificial single-crystal diamond powder with an average particle size of 20 μm was dispersed in anhydrous ethanol, and polyethylene glycol accounting for 0.3 wt% of the total mass of the suspension was added as a dispersant. The mixture was ultrasonically dispersed for 15 minutes to prepare a uniform suspension with a solid content of 20 vol%.

[0033] Ultrasonic coating: The sandblasted magnesium plate is completely immersed in the suspension and treated with 1500W ultrasound for 15 minutes. After removal, it is dried at room temperature.

[0034] Preheating and hot rolling: The sample was placed in an electric resistance furnace and preheated at 300°C for 10 minutes. Then it was hot rolled on a two-roll mill at 300°C with a total reduction of 50% (final thickness of 0.5 mm) and a rolling speed of 0.5 m / min.

[0035] Post-processing: The hot-rolled material is stress-relief annealed at 180°C for 1.5 hours, and then mechanically finished.

[0036] Performance testing: The obtained composite material has a room temperature planar thermal conductivity of 520 W / m·K and a density of 2.1 g / cm³. 3 The interfacial shear strength was 28 MPa, the coefficient of variation for diamond dispersion uniformity was 6.2%, and the flexural strength was 295 MPa. No magnesium carbide phase was detected by SEM or XRD analysis.

[0037] Example 2 (Single-sided composite structure)

[0038] Substrate pretreatment: ZK60 magnesium alloy foil with a thickness of 0.8 mm was selected, and mechanical polishing was performed on only one side of the surface using a wire brush. The roughness Ra of the roughened surface was 2.8 μm.

[0039] Suspension preparation: Diamond powder with an average particle size of 5 μm was dispersed in deionized water, and 0.2 wt% sodium dodecylbenzenesulfonate was added. The mixture was ultrasonically dispersed for 20 minutes to prepare a 15 vol% suspension.

[0040] Ultrasonic coating: The polished surface is immersed in the suspension and treated with 800W ultrasound for 25 minutes, and then dried in an oven at 60℃.

[0041] Preheating and hot rolling: Hold at 280℃ for 15 minutes, then hot roll with a total reduction of 40% (final thickness 0.48 mm) and a rolling speed of 0.3 m / min.

[0042] Post-treatment: Anneal at 160℃ for 2 hours.

[0043] Performance testing: The composite material exhibits a thermal conductivity as high as 550 W / m·K in the composite surface direction, while the non-composite surface retains the thermal conductivity of the magnesium alloy matrix (approximately 158 W / m·K), with a density of 2.08 g / cm³. 3 The interfacial shear strength is 32 MPa. This structure achieves asymmetric heat dissipation and is suitable for specific scenarios requiring only efficient heat dissipation from one side.

[0044] Example 3 (High Volume Fraction)

[0045] Substrate pretreatment: AM60 magnesium alloy plate with a thickness of 1.5mm, chemically etched on both sides with 10% hydrochloric acid solution for 30 seconds, Ra=4.5μm.

[0046] Suspension preparation: Diamond powder with an average particle size of 40 μm was dispersed in ethyl acetate, 0.5 wt% polyethylene glycol was added, and the mixture was sonicated for 12 minutes to prepare a high-concentration suspension of 35 vol%.

[0047] Ultrasonic coating: Fully immerse in the suspension, treat with 2000W high-power ultrasound for 8 minutes, and air dry at room temperature.

[0048] Preheating and hot rolling: Hold at 320℃ for 8 minutes, hot rolling total reduction of 60% (final thickness 0.6mm), rolling speed 0.7m / min.

[0049] Post-treatment: Anneal at 200℃ for 1 hour.

[0050] Performance testing: Thermal conductivity reaches 650 W / m·K, density is 2.28 g / cm³. 3 The interfacial shear strength was 26 MPa, the coefficient of variation for dispersion uniformity was 7.8%, the flexural strength was 282 MPa, and there were no interfacial reaction products.

[0051] Example 4 (Chemical Etching Pretreatment and Organic Medium)

[0052] Substrate pretreatment: AZ91D magnesium alloy plate with a thickness of 2.0 mm was chemically etched on both sides for 40 seconds using a mixture of 5% sulfuric acid and 3% phosphoric acid, with Ra = 3.8 μm.

[0053] Suspension preparation: Diamond powder with an average particle size of 15 μm was dispersed in anhydrous isopropanol, 0.1 wt% Span-80 was added, and the mixture was sonicated for 18 minutes to prepare a 25 vol% suspension.

[0054] Ultrasonic coating: Fully immerse, treat with 1200W ultrasound for 20 minutes, and dry with nitrogen.

[0055] Preheating and hot rolling: Hold at 310℃ for 12 minutes, hot rolling total reduction of 55% (final thickness 0.9mm), rolling speed 0.6m / min.

[0056] Post-treatment: Anneal at 170℃ for 1.8 hours.

[0057] Performance testing: Thermal conductivity 580 W / m·K, density 2.15 g / cm³ 3 The interfacial shear strength is 30 MPa, and the coefficient of variation for dispersion uniformity is 5.9%. Due to the cleaner etched surface, the corrosion resistance of the composite material is improved by approximately 30% compared to the matrix alloy.

[0058] Example 5 (Energy Saving and Scalability Adaptation Solution)

[0059] Substrate pretreatment: AZ31 magnesium plate with a thickness of 1.2mm, sandblasted on both sides with 180-mesh corundum sand, Ra=3.0μm.

[0060] Suspension preparation: Diamond powder with an average particle size of 25 μm was dispersed in deionized water, 0.3 wt% dispersant was added, and the mixture was sonicated for 15 minutes to prepare a 22 vol% suspension.

[0061] Ultrasonic coating: Treat with 1000W ultrasonic waves for 18 minutes, then air dry naturally.

[0062] Preheating and hot rolling: The plate is preheated to 290°C (held for about 5 minutes) using the residual heat of the rolling mill production line, and then directly hot rolled with a total reduction of 45% (final thickness 0.66 mm). The rolling speed is increased to 1.0 m / min to improve production efficiency.

[0063] Post-processing: To simplify the process, some stress is released by precisely controlling the rolling process parameters, thus omitting the separate annealing process.

[0064] Performance testing: Thermal conductivity 535 W / m·K, density 2.12 g / cm³ 3The interfacial shear strength is 27 MPa, and the coefficient of variation for dispersion uniformity is 6.5%. This solution reduces energy consumption per unit product by approximately 40%, and the estimated production cost can be reduced to 3800 yuan / kg, making it very suitable for large-scale continuous production.

[0065] Comparative Example (Traditional Powder Metallurgy)

[0066] Diamond powder with an average particle size of 20 μm was mixed with AZ31 magnesium powder at a ratio of 20 vol%. After ball milling for 10 hours, the mixture was hot-pressed and sintered at 600℃ and 30 MPa pressure for 2 hours to prepare a composite material.

[0067] Test results: The thermal conductivity is only 180 W / m·K; XRD and SEM showed that a large amount of brittle Mg2C3 phase was generated at the interface; the flexural strength is only 150 MPa; and the fracture toughness is 4.2 kJ / m. 2 The coefficient of variation for diamond dispersion uniformity is as high as 18.5%. All performance indicators are far inferior to any embodiment of the present invention.

Claims

1. A method for preparing a high thermal conductivity magnesium-diamond composite material, characterized in that, Includes the following steps: a) Substrate pretreatment: Select magnesium or magnesium alloy foil / plate with a thickness of 0.5-2 mm, and roughen at least one surface to achieve a surface roughness Ra of 1.5-5.0 μm; b) Suspension preparation and impregnation: Disperse artificial single-crystal diamond powder with a particle size of 1-50 μm in a liquid medium, add a dispersant accounting for 0.1-0.5 wt% of the total mass of the suspension, and prepare a uniform suspension with a solid content of 5-40 vol%; immerse the substrate treated in step a) into the suspension; c) Ultrasonic coating: Apply an ultrasonic coating to the immersed substrate. The process involves: d) Preheating and hot rolling: The matrix with diamond particles embedded is heated to 250-350℃ and held for 10-30 minutes, followed by hot rolling at 280-320℃ with a deformation of 20%-70% and a rolling speed of 0.3-1.0 m / min; e) Post-treatment: The hot-rolled material is stress-relieved annealed at 150-200℃ for 1-2 hours, followed by mechanical finishing.

2. The preparation method according to claim 1, characterized in that, In step a), the roughening treatment is sandblasting, mechanical grinding with a wire brush, or chemical etching; the magnesium alloy is AZ31, ZK60, AM60, or AZ91D.

3. The preparation method according to claim 1, characterized in that, In step b), the liquid medium is deionized water, ethanol, isopropanol or ethyl acetate; the dispersant is polyethylene glycol, sodium dodecylbenzenesulfonate or Span-80.

4. The preparation method according to claim 1, characterized in that, In step c), the power of the ultrasonic treatment is 800-1500W, and the treatment time is 10-20 minutes.

5. The preparation method according to claim 1, characterized in that, In step d), the hot rolling temperature is 300°C and the deformation is 40%-55%.

6. A high thermal conductivity magnesium-diamond composite material prepared by the method according to any one of claims 1 to 5, characterized in that, include: A magnesium or magnesium alloy matrix, and artificial single-crystal diamond particles embedded in at least one surface layer of the matrix; the volume fraction of the artificial single-crystal diamond particles is 5%-40%, and the composite material contains no magnesium carbide interfacial reaction products.

7. The high thermal conductivity magnesium-diamond composite material according to claim 6, characterized in that, The composite material has a room temperature planar thermal conductivity ≥400 W / m·K and a density ≤2.3 g / cm³. 3 The interfacial shear strength is ≥25MPa, and the coefficient of variation of the dispersion uniformity of the artificial single-crystal diamond particles in the surface layer is ≤8%.

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