Precise manufacturing method of aluminum-based silicon carbide

Abstract

The invention discloses a precise manufacturing method of aluminum-based silicon carbide. The method comprises the following steps: (1) preparing or preparing porous silicon carbide; (2) placing porous silicon carbide in graphite powder, wherein the upper surface of the silicon carbide is in contact with air; and (3) placing an aluminum block on the upper surface of the silicon carbide, heating and melting the aluminum block, and impregnating molten aluminum into pores of the silicon carbide to prepare the aluminum-based silicon carbide. According to the method, the extremely poor wettability between the molten aluminum and the graphite powder is fully utilized, diffusion and loss of the molten aluminum in a non-target area (namely the graphite powder) are effectively reduced, the molten aluminum can rapidly and intensively infiltrate silicon carbide pores, compared with a traditional infiltration process, the infiltration efficiency is improved by 30%-50%, and the production period is greatly shortened.

Description

Technical Field

[0001] The present invention belongs to the technical field of manufacturing aluminum-based silicon carbide composite materials, and particularly relates to a precision manufacturing method of aluminum-based silicon carbide. Background Art

[0002] In the existing technology, the production of aluminum-based silicon carbide parts generally adopts the model of "preparing raw materials first, and then machining". This traditional manufacturing method has many disadvantages: on the one hand, the process cost remains high. During the raw material preparation stage, a large amount of money needs to be invested in equipment purchase and raw material processing; during the machining process, there are problems such as tool wear and low processing efficiency, which leads to a significant increase in manpower, material and time costs. On the other hand, the manufacturing cycle is long. From the smelting and forming of raw materials to the subsequent cutting, grinding, polishing and other processes of parts, the entire process is time-consuming, seriously restricting production efficiency, and it is difficult to meet the market demand for rapid iteration. Therefore, the development of a new process that can directly manufacture high-precision aluminum-based silicon carbide parts has become the key to solving existing technical problems and promoting industry development. Summary of the Invention

[0003] In order to improve the above technical problems, the present invention provides a precision manufacturing process for aluminum-based silicon carbide. The process is based on the poor wettability of aluminum liquid and graphite to achieve the manufacture of high-precision aluminum-based silicon carbide, effectively reduce production costs, significantly shorten the manufacturing cycle, and improve product quality and production efficiency to meet the urgent demand of modern industry for high-performance aluminum-based silicon carbide parts.

[0004] Based on this, the technical solution of the present invention is as follows:

[0005] A method for manufacturing aluminum-based silicon carbide, the method comprising the following steps:

[0006] (1) preparing or preparing porous silicon carbide;

[0007] (2) placing porous silicon carbide in graphite powder, with the upper surface of the porous silicon carbide in contact with air;

[0008] (3) Placing an aluminum block on the upper surface of the porous silicon carbide, heating the aluminum block to melt it, and allowing the molten aluminum liquid to penetrate into the pores of the porous silicon carbide to prepare aluminum-based silicon carbide.

[0009] According to an embodiment of the present invention, in step (1), the porosity of the porous silicon carbide is 10%-70%, preferably 20-50%, for example 20%, 30%, 40% or 50%. In the present invention, precise control of the porosity of the porous silicon carbide is a key factor in ensuring the subsequent aluminum liquid infiltration effect. Different porosities will affect the infiltration speed and filling degree of the aluminum liquid, and thus affect the ultimate performance of the aluminum-based silicon carbide.

[0010] According to an embodiment of the present invention, in step (1), the porous silicon carbide is prepared using techniques known in the art, such as additive manufacturing processes (such as stereolithography, selective laser sintering, etc.) or traditional machining processes (such as turning, milling, grinding, etc.).

[0011] According to an embodiment of the present invention, in step (2), the particle size of the graphite powder is larger than the pore size of the porous silicon carbide. In the present invention, the particle size of the graphite powder and the pore size of the porous silicon carbide are not particularly limited, as long as the graphite powder does not enter the pores of the silicon carbide. For example, the particle size of the graphite powder is 0.1 mm to 0.5 mm, for example, 0.2 mm; the pore size of the porous silicon carbide is 0.01 mm to 0.3 mm, for example, 0.15 mm.

[0012] According to an embodiment of the present invention, in step (2), porous silicon carbide is embedded in graphite powder, so that the porous silicon carbide and the graphite powder are closely fitted to form a good contact interface. Preferably, after the porous silicon carbide is embedded in the graphite powder, a pressing block is used to compact the porous silicon carbide and the graphite powder. Preferably, the shape, volume and weight of the pressing block are not particularly limited, so that the porous silicon carbide and the graphite powder are closely fitted, so that the graphite powder provides support for the porous silicon carbide. In the present invention, through this step, not only a stable channel can be provided for the directional infiltration of aluminum liquid, but also a wetting angle of up to 157° (at room temperature) between the aluminum liquid and the graphite can be used, and at high temperatures (700-1200°C), a wetting angle greater than 90° is still maintained, effectively preventing the aluminum liquid from seeping out of the silicon carbide, thereby ensuring the accuracy and controllability of the infiltration process.

[0013] According to an embodiment of the present invention, in step (2), after the porous silicon carbide is placed in the graphite powder, the graphite powder covering the upper surface of the porous silicon carbide is cleaned to expose the upper surface of the porous silicon carbide. In the present invention, except for the upper surface of the porous silicon carbide that is in contact with air, the other surfaces are in contact with the graphite powder.

[0014] According to an embodiment of the present invention, in step (3), the weight of the aluminum block is calculated as follows:

[0015] Aluminum block weight = (aluminum-based silicon carbide mass - porous silicon carbide mass) × (1.5 to 2.0)

[0016] According to an embodiment of the present invention, in step (3), the heating and melting temperature is 700-1200°C, for example, 700°C, 800°C, 900°C, 1000°C, 1100°C or 1200°C, and the heating and melting time is 5-20 hours, preferably 8-15 hours. During the heating to the heating and melting temperature, the heating rate is 5-15°C / min.

[0017] According to an embodiment of the present invention, in step (3), heating and melting are performed under vacuum conditions or inert gas.

[0018] Preferably, the vacuum degree is 10 -3 -10 -5 Pa.

[0019] Preferably, the inert gas is argon or nitrogen, and the flow rate of the added inert gas is 5-20 L / min.

[0020] According to an embodiment of the present invention, step (3) is performed in a heating furnace. In step (3) of the present invention, the solid aluminum block gradually melts at 700-1200°C. The molten aluminum liquid has good fluidity and, driven by capillary action and pressure differential, quickly and evenly infiltrates into the pores of the porous silicon carbide.

[0021] According to an embodiment of the present invention, step (3) further includes a post-processing step: after the molten aluminum liquid is impregnated into the pores of the porous silicon carbide, the impregnated product is cooled to solidify the aluminum liquid and form the aluminum-based silicon carbide. For example, the cooling method is natural cooling, forced air cooling, or water cooling.

[0022] Specifically, the post-processing steps are as follows: after the infiltration process is completed, the crucible is taken out of the heating furnace, and a cooling method such as natural cooling, forced air cooling or water cooling is adopted to rapidly solidify the aluminum liquid into a shape, and after cooling and solidification treatment, aluminum-based silicon carbide with a dense structure and excellent performance is finally obtained.

[0023] The present invention also provides aluminum-based silicon carbide prepared by the above method.

[0024] According to an embodiment of the present invention, the porosity of the aluminum-based silicon carbide is 5% or less, preferably 4% or less.

[0025] The present invention also provides applications of the aluminum-based silicon carbide in high-end equipment manufacturing, aerospace and other fields.

[0026] Beneficial effects of the present invention:

[0027] The present invention utilizes the extremely poor wettability between molten aluminum and graphite to prepare aluminum-based silicon carbide. At room temperature, the wetting angle between molten aluminum and graphite is approximately 157°, and during the high-temperature infiltration process (700-1200°C), this wetting angle remains above 90°, causing the molten aluminum to exhibit a strong non-wetting characteristic on the surface of the graphite powder. In silicon carbide, due to its porous structure and relatively good wettability with the molten aluminum, when the molten aluminum is in a molten state, under the combined effects of temperature gradient, pressure difference, and capillary force, the molten aluminum can preferentially and quickly fill the pores of the silicon carbide without randomly spreading or leaking on the surface of the graphite powder. This allows for efficient and precise infiltration of the molten aluminum into the pores of the silicon carbide, laying the foundation for the preparation of high-performance aluminum-based silicon carbide composite materials.

[0028] (1) The method of the present invention makes full use of the extremely poor wettability between aluminum liquid and graphite powder, effectively reducing the diffusion and loss of aluminum liquid in non-target areas (i.e., graphite powder), so that the aluminum liquid can quickly and concentratedly infiltrate the pores of silicon carbide. Compared with the traditional infiltration process, the infiltration efficiency is improved by 30%-50%, which greatly shortens the production cycle.

[0029] (2) The present invention abandons the steps of complex surface modification of silicon carbide (such as chemical coating, surface activation, etc.) and the addition of expensive alloying elements in traditional processes, simplifies the process flow, reduces raw material and processing costs, and can reduce production costs by 20%-30%.

[0030] (3) By precisely controlling the process parameters of silicon carbide, such as porosity, heating and melting temperature, and heating and melting time, the prepared aluminum-based silicon carbide has extremely high density, and the porosity can be controlled below 5%. The dense microstructure gives the material excellent mechanical properties (such as a 5%-25% increase in tensile strength) and thermal properties (such as a 10%-20% increase in thermal conductivity and a 10%-15% decrease in thermal expansion coefficient), meeting the stringent requirements for high-performance materials in high-end equipment manufacturing, aerospace and other fields.

[0031] (4) The processes for preparing silicon carbide (e.g., additive manufacturing, machining), heating and melting, etc., of the present invention are all mature industrial technologies, with simple and easy-to-understand operation procedures and relatively low equipment requirements. Furthermore, the infiltration process does not require complex special equipment, facilitating technological transformation and production line upgrades for enterprises, and thus has good prospects for industrial application.

[0032] (5) The method of the present invention is not limited by the shape and size of silicon carbide. It can achieve high-precision manufacturing of complex special-shaped structural parts, large and small parts, and can be widely used in electronic packaging, automotive parts, mold manufacturing, aerospace and other fields, and has broad market application space. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1It is a schematic diagram of the infiltration process of aluminum-based silicon carbide of the present invention.

[0034] Figure 2 This is a micrograph of the aluminum-based silicon carbide of Example 1 (magnification is 1000 times). DETAILED DESCRIPTION

[0035] The technical solutions of the present invention will be described in further detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are encompassed within the scope of protection that the present invention is intended to protect.

[0036] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0037] Example 1

[0038] Porous SiC green body preparation: Using the Selective Laser Sintering (SLS) additive manufacturing process, SiC powder was used to produce a 100mm x 100mm x 50mm SiC green body with a porosity of 30%. Testing showed that the green body had good structural strength and uniform pore distribution.

[0039] Graphite powder covering: Place the silicon carbide green body in a graphite crucible, pour in high-purity graphite powder to completely cover the green body, so that the green body and graphite powder are in close contact, clean the graphite powder covering the upper surface of the silicon carbide, expose the upper surface of the silicon carbide, and allow the upper surface of the silicon carbide to contact with the air.

[0040] Aluminum block placement: Place a 500g pure aluminum block on the upper surface of silicon carbide, ensuring that the aluminum block is placed in the center to ensure uniform aluminum liquid infiltration.

[0041] Heating and Impregnation: A crucible containing silicon carbide, graphite powder, and aluminum blocks is placed in a vacuum furnace. The vacuum is evacuated to 10-3 Pa. The temperature is raised to 800°C at a rate of 10°C / min and held at this temperature for 10 hours. During the impregnation process, the temperature and vacuum level are monitored in real time to ensure stable process parameters.

[0042] Cooling and forming: After the impregnation is completed, the heating power is turned off and the crucible is allowed to cool naturally to room temperature in the furnace. The parts are taken out and tested. The surface of the parts is smooth, there is no aluminum liquid leakage, the internal structure is dense, the porosity is reduced to 3%, the bending strength of the parts is 460MPa, the elastic modulus is 125GPa, and the thermal conductivity is 163W.m -1 .K -1 , the linear expansion coefficient is 9.0×10 -6 / ℃, both mechanical and thermal properties meet the expected indicators.

[0043] Example 2

[0044] Preparation of porous silicon carbide green body: Using traditional machining technology, the block silicon carbide material is turned, milled and other processing operations to produce a silicon carbide green body with a size of 200mm×200mm×100mm, with a porosity of 25%.

[0045] Graphite powder covering and tamping: Transfer the green embryo to a graphite crucible, fill it with graphite powder and tamp it to ensure that there is no gap between the green embryo and the graphite powder to form a good infiltration environment. Clean the graphite powder covering the upper surface of the silicon carbide, expose the upper surface of the silicon carbide, and allow the upper surface of the silicon carbide to contact with the air.

[0046] Aluminum block placement: Place two aluminum blocks with masses of 300g and 200g respectively on the upper surface of silicon carbide. The two aluminum blocks are stacked to ensure that the aluminum liquid can fully cover the surface of the part and penetrate smoothly.

[0047] Heating and Impregnation: A crucible containing silicon carbide, graphite powder, and aluminum blocks was placed in an argon-filled, protective heating furnace at a flow rate of 10 L / min. The crucible was heated to 1000°C at a rate of 15°C / min and held at that temperature for 15 hours. During the impregnation process, the temperature was monitored in real time using an infrared thermometer to ensure temperature uniformity.

[0048] Cooling and forming: After the impregnation is completed, the crucible is quickly cooled by forced air cooling, and the part is taken out after cooling to room temperature. After testing, the part is well formed as a whole, with uniform internal structure, porosity of 4%, bending strength of 420MPa, elastic modulus of 113GPa, and thermal conductivity of 170W.m -1 .K -1 , linear expansion coefficient 10.5×10 -6 / ℃, all performance indicators meet the design requirements.

[0049] Example 3

[0050] Porous SiC green body preparation: Using stereolithography (SLA) additive manufacturing, a SiC green body measuring 50mm x 50mm x 30mm was produced with a controlled porosity of 40%. This process produces a dimensional accuracy of ±0.1mm and a fine internal pore structure.

[0051] Graphite powder covering: Carefully place the green embryo into the graphite crucible, cover it with graphite powder and tamp it, ensuring that there is no gap between the green embryo and the graphite powder, ensuring that the infiltration channel is unobstructed, clean the graphite powder covering the upper surface of the silicon carbide, expose the upper surface of the silicon carbide, and allow the upper surface of the silicon carbide to contact with the air.

[0052] Aluminum block placement: Place an aluminum block with a mass of 200g on the upper surface of silicon carbide to ensure that the aluminum block can provide sufficient aluminum liquid for the porous silicon carbide.

[0053] Heating and impregnation: Place the crucible containing silicon carbide, graphite powder and aluminum block in a vacuum heating furnace and evacuate to 10 -4 Pa, heated to 900°C at a rate of 8°C / min and kept at this temperature for 12 hours. During the infiltration process, the wetting of the aluminum liquid was observed to ensure that the silicon carbide was fully infiltrated.

[0054] Cooling and forming: After the infiltration is completed, the crucible is allowed to cool slowly in the furnace to avoid deformation of the parts due to thermal stress. After cooling, the parts are taken out and tested. The silicon carbide infiltration is complete, the porosity is 3.5%, the bending strength of the parts is 545MPa, the elastic modulus is 147GPa, and the thermal conductivity is 123W.m -1 .K -1 , linear expansion coefficient 6.5×10 -6 / ℃, which can meet the needs of special application scenarios.

[0055] The above is an exemplary description of the embodiments of the present invention. However, the scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for producing aluminum-based silicon carbide, characterized in that: The method comprises the following steps: (1) preparing or preparing porous silicon carbide; (2) placing porous silicon carbide in graphite powder, with the upper surface of the porous silicon carbide in contact with air; (3) Placing an aluminum block on the upper surface of silicon carbide, heating the aluminum block to melt it, and allowing the molten aluminum liquid to penetrate into the pores of the silicon carbide to prepare aluminum-based silicon carbide.

2. The method according to claim 1, characterized in that In step (1), the porosity of the porous silicon carbide is 10%-70%.

3. The method according to claim 1, characterized in that In step (2), the particle size of the graphite powder is larger than the pore size of the porous silicon carbide.

4. The method according to claim 1, wherein In step (2), silicon carbide is embedded in graphite powder, so that silicon carbide and graphite powder are closely attached to form a good contact interface.

5. The method according to claim 1, wherein In step (2), after the porous silicon carbide is placed in the graphite powder, the graphite powder covering the upper surface of the porous silicon carbide is cleaned to expose the upper surface of the porous silicon carbide.

6. The method according to claim 1, characterized in that In step (2), the weight of the aluminum block is calculated as follows: Aluminum block weight = (aluminum-based silicon carbide mass - porous silicon carbide mass) × (1.5 to 2.0).

7. The method according to claim 1, characterized in that In step (3), the heating and melting temperature is 700-1200° C., and the heating and melting time is 5-20 hours; During the heating process to the melting temperature, the heating rate is 5-15°C / min.

8. The method according to claim 1, characterized in that In step (3), heating and melting are carried out under vacuum conditions or inert gas.

9. Aluminum-based silicon carbide prepared by the method according to any one of claims 1 to 8.

10. Use of the aluminum-based silicon carbide according to claim 9 in high-end equipment manufacturing or aerospace fields.

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