A kind of ceramic fiber reinforced aluminum matrix composite based on stir casting and its preparation method

Abstract

The application discloses a kind of based on stirring ceramic fiber reinforced aluminum matrix composite and preparation method thereof, belong to composite material technical field.The composite preparation method is: aluminum alloy is heated under stirring state and is fully fused, remove surface oxide film, then add the ceramic fiber silk of pretreatment, improve stirring speed and fully mix, then cast forming, namely obtained;The mass ratio of aluminum alloy and ceramic fiber silk is 4~7:1;The ceramic fiber silk is one of pure ceramic fiber and aluminum base ceramic composite fiber.The method not only greatly improves the dispersivity of fiber reinforced phase, but also greatly improves the infiltration of aluminum alloy matrix to ceramic fiber, effectively improves two-phase interface, so as to significantly improve the mechanical properties of composite material, by testing, with ZL102 aluminum alloy as base material, aluminum base silicon carbide fiber as ceramic fiber reinforced phase, its tensile strength can reach 709MPa, compared with ordinary ZL102 aluminum alloy, it is increased by 443%.

Description

Technical Field

[0001] This invention relates to an aluminum-based composite material, specifically to an aluminum-based composite material reinforced with ceramic fiber based on stir casting and its preparation method, belonging to the field of composite material technology. Background Technology

[0002] Aluminum-based composites are widely used in aerospace, automotive manufacturing, and electronics industries due to their excellent properties, such as high strength, low density, corrosion resistance, and good thermal conductivity. However, to further improve their mechanical and high-temperature properties, researchers have developed various reinforcing phases, among which ceramic fibers are widely used for reinforcing aluminum-based composites due to their excellent mechanical and high-temperature properties.

[0003] Currently, the preparation processes for fiber-reinforced aluminum matrix composites are mostly powder metallurgy, etc. This is because the traditional simple casting process is difficult to achieve uniformity due to the large density difference between the fiber and the aluminum matrix. Furthermore, in the molten aluminum state, the fiber will react with the aluminum alloy matrix to generate harmful phases, which will affect the overall performance of the composite material. For example, in carbon fiber and silicon carbide fiber, the free carbon element will react with the aluminum alloy matrix at high temperature to generate harmful phases such as Al4C3.

[0004] Meanwhile, the wettability between the fiber and the aluminum alloy matrix is ​​poor, and it is usually necessary to use methods such as ultrasound and pressure to improve its wettability. This preparation method is complicated and it is difficult to prepare large-sized components.

[0005] Based on the above-mentioned problems, the present invention provides a ceramic fiber reinforced aluminum matrix composite material formed by stirring casting and its preparation method. Summary of the Invention

[0006] To address the problems existing in the prior art, the first objective of this invention is to provide a ceramic fiber-reinforced aluminum matrix composite material based on stir casting. This aluminum matrix composite material uses chopped ceramic fibers as the reinforcing phase and aluminum alloy as the matrix. Stir casting significantly improves not only the dispersion of the fiber reinforcing phase but also the wettability of the aluminum alloy matrix to the ceramic fibers, effectively improving the interface between the two phases and thus significantly enhancing the mechanical properties of the composite material. Testing showed that this aluminum matrix composite material, using ZL102 aluminum alloy as the matrix and aluminum-based silicon carbide fibers as the ceramic fiber reinforcing phase, achieved a tensile strength of 597 MPa at a rate of 1 mm / min, which is 373% higher than that of ordinary ZL102 aluminum alloy.

[0007] The second objective of this invention is to provide a method for preparing ceramic fiber reinforced aluminum matrix composites based on stir casting. This method utilizes the solid-liquid phase equilibrium of the aluminum alloy material. First, the aluminum alloy matrix is ​​heated to a temperature slightly above its melting point to ensure complete melting. Then, it is slowly lowered to the melting point to prevent solidification. At this point, short-cut ceramic fibers are added through stir casting. This not only ensures the uniform distribution of ceramic fibers within the aluminum alloy matrix but also effectively inhibits the reaction between the ceramic fibers and the aluminum alloy matrix, preventing the formation of harmful phases. Therefore, while simplifying the process, this method also significantly improves the mechanical properties of the aluminum matrix composite.

[0008] To achieve the above-mentioned technical objectives, the present invention provides a method for preparing ceramic fiber reinforced aluminum matrix composite material based on stirring casting, comprising: heating and fully melting aluminum alloy under stirring, removing the surface oxide film, then adding short-cut ceramic fiber filaments, increasing the stirring speed to fully mix, and then casting to form the composite material.

[0009] The mass ratio of the aluminum alloy to the ceramic fiber is 4~7:1; the ceramic fiber is one of pure ceramic fiber and aluminum-based ceramic composite fiber.

[0010] The purpose of using stirring casting in the technical solution provided by this invention is that: the stirring process generates strong turbulence and shear field, which can break the agglomeration of fibers and achieve uniform dispersion. It can also make the aluminum melt scour the surface of ceramic fibers, enhance the physical contact of the interface, and improve wettability. Furthermore, the stirring casting process of this invention is mainly carried out at a temperature close to the liquidus, and the melt viscosity is moderate, which is conducive to the discharge of bubbles and the inhibition of interface reactions. Therefore, good interface bonding can be obtained without applying external pressure or a vacuum environment. Compared with complex processes such as vacuum casting and pressure infiltration, it significantly reduces equipment costs, simplifies the process flow, and is more suitable for large-scale industrial applications.

[0011] In this invention, the ratio of raw materials must be strictly implemented in accordance with the above requirements. When the mass ratio of aluminum alloy to ceramic fiber is less than 4:1, the proportion of reinforcing phase is too high, and the fibers are prone to agglomeration, resulting in decreased fluidity and increased porosity, thereby weakening the interfacial bonding. When the mass ratio is higher than 7:1, the fiber volume fraction is insufficient, the reinforcing effect is not obvious, and the strength improvement of the composite material is limited.

[0012] Therefore, the present invention limits the mass ratio of aluminum alloy to ceramic fiber to a range of 4 to 7:1 in order to balance fiber dispersibility, interfacial wettability and overall mechanical properties of the composite material.

[0013] As a preferred embodiment, during the heating and melting process, the stirring speed is 50~70 r / min.

[0014] As a preferred embodiment, during the thorough mixing process, the stirring speed is 100~140 r / min and the duration is 10~30 min.

[0015] This invention employs a two-stage variable-speed stirring control for efficient composite processing of raw materials. The low-speed stirring stage (50-70 r / min) primarily functions during the initial heating and melting phase. This not only prevents melt splashing and air entrapment but also helps homogenize the temperature and composition fields, providing a stable flow environment for subsequent fiber addition. The high-speed stirring stage (100-140 r / min) mainly focuses on fiber dispersion. After fiber addition, high-speed stirring generates strong shear force, promoting uniform dispersion of ceramic fibers in the melt and preventing fiber agglomeration and sedimentation. It is crucial that the stirring sequence and parameter settings strictly adhere to these requirements. Reversing the stirring order (high speed followed by low speed) can easily lead to oxide film entrapment or melt splashing during the initial high-temperature, high-speed stirring, reducing material purity. Furthermore, if only low-speed stirring is used after fiber addition, insufficient dispersion will affect the reinforcing effect.

[0016] As a preferred embodiment, the conditions for fully melting the aluminum alloy are as follows: placing the aluminum alloy in a melting furnace, heating it from room temperature to 750-800℃ at a rate of 8-12℃ / min, and holding it at that temperature for 1-3 hours.

[0017] As a preferred embodiment, the chopped ceramic fiber filaments have a diameter of 10~30μm and a length of 100~150μm.

[0018] As a preferred embodiment, a cooling process is required before removing the surface oxide film. The process involves turning off the heating and holding the molten aluminum alloy at 680~730℃.

[0019] Al4C3 is a harmful phase that can form during the preparation of aluminum-based composites, mainly appearing at the interface where aluminum contacts carbon or carbon-containing materials (such as graphene, carbon fibers, etc.). Al4C3 is a brittle phase that reduces the toughness of the material, making the composite prone to crack propagation under stress, affecting long-term reliability. Especially in humid environments, Al4C3 may absorb moisture and hydrolyze, further exacerbating embrittlement. Furthermore, the formation of Al4C3 can disrupt the interfacial bonding between the aluminum matrix and the reinforcing phase, hindering effective stress transfer and reducing the mechanical properties of the composite. In specific applications, such as thermal management, the presence of Al4C3 introduces interfacial thermal resistance, reducing the thermal conductivity of the composite, and this effect is difficult to control, easily leading to thermal runaway.

[0020] The reason for performing a cooling treatment after removing the oxide film in this invention is to avoid the aluminum alloy reacting with the fiber at high temperatures, thereby generating brittle phases such as Al4C3 and AlN, which would reduce the mechanical properties of the composite material. In addition, the aluminum alloy melt after cooling treatment can reduce the melt viscosity, improve fiber wettability, reduce gas dissolution and oxidation tendency, ensure the purity of the composite material structure, and the temperature near the liquidus line can also form a semi-solid flow state with the fiber, enhancing the stirring and dispersion effect.

[0021] As a preferred embodiment, the casting process is as follows: the aluminum alloy melt mixed with ceramic fibers is poured into a graphite mold coated with a release agent and cooled and shaped at room temperature.

[0022] As a preferred embodiment, the release agent is one of boron nitride, borate, and silicone oil.

[0023] As a preferred embodiment, the pure ceramic fiber is at least one of silicon carbide fiber, silicon nitride fiber, carbon fiber, and alumina fiber.

[0024] As a preferred embodiment, the aluminum-based ceramic composite fiber is at least one of aluminum-based silicon carbide fiber, aluminum-based silicon nitride fiber, aluminum-based carbon fiber, and aluminum-based alumina fiber.

[0025] As a preferred embodiment, the mass percentage of pure aluminum in the aluminum-based ceramic composite fiber is 40-60%.

[0026] Compared to pure ceramic fibers, aluminum-based ceramic composite fibers have an aluminum coating, which significantly improves compatibility and wettability with the matrix melt, effectively enhances interfacial bonding, and reduces the chemical reactivity of the fibers at high temperatures. Simultaneously, controlling the proportion of pure aluminum in the composite fiber is crucial: when the pure aluminum content is below 40 wt.%, the coating layer is insufficient, resulting in limited improvement in wettability; when the pure aluminum content is above 60 wt.%, the ceramic proportion on the fiber surface is too low, reducing the reinforcing effect. Therefore, this invention limits the pure aluminum mass fraction in the aluminum-based ceramic composite fiber to 40-60 wt% to balance interfacial bonding and reinforcing effects.

[0027] The present invention also provides a ceramic fiber reinforced aluminum matrix composite material based on stirred casting, which is prepared by the method described in any one of the above.

[0028] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0029] 1) The aluminum-based composite material provided by this invention uses chopped ceramic fibers as the reinforcing phase and aluminum alloy as the matrix. Through stirring casting, the dispersion of the fiber reinforcing phase is greatly improved, as is the wettability of the aluminum alloy matrix to the ceramic fibers, effectively improving the interface between the two phases, thereby significantly improving the mechanical properties of the composite material. According to the test, the aluminum-based composite material with ZL102 aluminum alloy as the matrix and aluminum-based silicon carbide fiber as the ceramic fiber reinforcing phase can achieve a tensile strength of 597 MPa at a rate of 1 mm / min, which is 373% higher than that of ordinary ZL102 aluminum alloy.

[0030] 2) The preparation method provided by the present invention utilizes the solid-liquid phase equilibrium of aluminum alloy materials. First, the aluminum alloy matrix is ​​heated to a temperature slightly above the melting point to ensure complete melting of the aluminum alloy matrix. Then, it is slowly lowered to the melting point temperature to ensure that the aluminum alloy melt does not solidify. At this time, short-cut ceramic fibers are added by stirring casting. This not only ensures the uniform distribution of ceramic fibers in the aluminum alloy matrix, but also effectively inhibits the reaction between ceramic fibers and aluminum alloy matrix to generate harmful phases. Thus, while simplifying the process, it also significantly improves the mechanical properties of aluminum-based composite materials. Attached Figure Description

[0031] Figure 1 The tensile mechanical properties of the aluminum-based composite materials obtained in Examples 1-3 and Comparative Examples 1 and 2 of this invention are shown in the diagram.

[0032] Figure 2 This is a scanning electron microscope image of the aluminum-based composite material obtained in Example 1 of the present invention. Detailed Implementation

[0033] To enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, and to make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described below.

[0034] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0035] Example 1

[0036] This embodiment provides a ceramic fiber reinforced aluminum matrix composite material based on stir casting, and its specific preparation process is as follows:

[0037] 1) Silicon carbide fiber aluminum-based preforms with a diameter of 20 μm were cut into 100 μm chopped preforms using a chopped strand cutter. The mass percentage of silicon carbide fiber in the chopped preforms was 50 wt%.

[0038] 2) Heat 1 kg of ZL102 aluminum alloy to 750℃ in a clay crucible and hold for 2 hours to ensure that the aluminum alloy is completely melted. During this period, stir the melt continuously at 60 r / min.

[0039] 3) Stop heating and hold the melt at 700℃ when the temperature drops naturally. Then remove the oxide film on the surface of the crucible and immediately add 0.3 kg of the obtained chopped pre-stranded wire. At the same time, increase the stirring speed to 120 r / min and continue for 15 min.

[0040] 4) After stirring, pour the aluminum alloy melt containing the mixed ceramic fibers into a 200×200mm graphite mold coated with boron nitride release agent, and cool it to room temperature to obtain the final product.

[0041] The aluminum-based composite material obtained above was cut into standard tensile specimens, and then tensile tests were performed on a mechanical testing machine at a rate of 1 mm / min. The tensile strength was measured to be 709 MPa.

[0042] Example 2

[0043] The difference between this embodiment and Embodiment 1 lies in the content of ceramic fiber added:

[0044] 1) Silicon carbide fiber aluminum-based preforms with a diameter of 20 μm were cut into 100 μm chopped preforms using a chopped strand cutter. The mass percentage of silicon carbide fiber in the chopped preforms was 50 wt%.

[0045] 2) Heat 1 kg of ZL102 aluminum alloy to 750℃ in a clay crucible and hold for 2 hours to ensure that the aluminum alloy is completely melted. During this period, stir the melt continuously at 60 r / min.

[0046] 3) Stop heating and hold the melt at 700℃ when the temperature drops naturally. Then remove the oxide film on the surface of the crucible and immediately add 0.2 kg of the obtained chopped pre-stranded wire. At the same time, increase the stirring speed to 120 r / min and continue for 15 min.

[0047] 4) After stirring, pour the aluminum alloy melt containing the mixed ceramic fibers into a 200×200mm graphite mold coated with boron nitride release agent, and cool it to room temperature to obtain the final product.

[0048] The aluminum-based composite material obtained above was cut into standard tensile specimens, and then tensile tests were performed on a mechanical testing machine at a rate of 1 mm / min. The tensile strength was measured to be 597 MPa.

[0049] Example 3

[0050] The difference between this embodiment and Embodiment 1 lies in the type of ceramic fiber used:

[0051] 1) Carbon fiber aluminum-based preforms with a diameter of 20 μm were cut into 100 μm chopped preforms using a chopped strand cutter. The carbon fiber content in the chopped preforms was 50 wt%.

[0052] 2) Heat 1 kg of ZL102 aluminum alloy to 750℃ in a clay crucible and hold for 2 hours to ensure that the aluminum alloy is completely melted. During this period, stir the melt continuously at 60 r / min.

[0053] 3) Stop heating and hold the melt at 700℃ when the temperature drops naturally. Then remove the oxide film on the surface of the crucible and immediately add 0.2 kg of the obtained chopped pre-stranded wire. At the same time, increase the stirring speed to 120 r / min and continue for 15 min.

[0054] 4) After stirring, pour the aluminum alloy melt containing the mixed ceramic fibers into a 200×200mm graphite mold coated with boron nitride release agent, and cool it to room temperature to obtain the final product.

[0055] The aluminum-based composite material obtained above was cut into standard tensile specimens, and then tensile tests were performed on a mechanical testing machine at a rate of 1 mm / min. The tensile strength was measured to be 910 MPa.

[0056] Comparative Example 1

[0057] The difference between this embodiment and Embodiment 1 lies in the temperature:

[0058] 1) Silicon carbide fiber aluminum-based preforms with a diameter of 20 μm were cut into 100 μm chopped preforms using a chopped strand cutter. The mass percentage of silicon carbide fiber in the chopped preforms was 50 wt%.

[0059] 2) Heat 1 kg of ZL102 aluminum alloy to 750℃ in a clay crucible and hold for 2 hours to ensure that the aluminum alloy is completely melted. During this period, stir the melt continuously at 120 r / min.

[0060] 3) Keep the temperature at 750℃, then remove the oxide film on the surface of the crucible, and immediately add 0.2 kg of the obtained chopped pre-shredded wire, while reducing the stirring rate to 60 r / min for 15 min.

[0061] 4) After stirring, pour the aluminum alloy melt containing the mixed ceramic fibers into a 200×200mm graphite mold coated with boron nitride release agent, and cool it to room temperature to obtain the final product.

[0062] The aluminum-based composite material obtained above was cut into standard tensile specimens, and then tensile tests were performed on a mechanical testing machine at a rate of 1 mm / min. The tensile strength was measured to be 440 MPa.

[0063] Comparative Example 2

[0064] The difference between this embodiment and Embodiment 1 lies in the stirring speed:

[0065] 1) 0.2 kg of silicon carbide fiber aluminum-based preforms with a diameter of 20 μm were cut into 100 μm lengths using a chopped strand cutter. The silicon carbide fiber content in the chopped strands was 50 wt%.

[0066] 2) Heat 1 kg of ZL102 aluminum alloy to 750℃ in a clay crucible and hold for 2 hours to ensure that the aluminum alloy is completely melted. During this period, stir the melt continuously at 120 r / min.

[0067] 3) Stop heating and hold the melt at 700°C until the temperature drops naturally. Then remove the oxide film from the surface of the crucible and immediately add the chopped pre-formed filaments. At the same time, reduce the stirring speed to 60 r / min and hold for 15 min.

[0068] 4) After stirring, pour the aluminum alloy melt containing the mixed ceramic fibers into a 200×200mm graphite mold coated with boron nitride release agent, and cool it to room temperature to obtain the final product.

[0069] The aluminum-based composite material obtained above was cut into standard tensile specimens, and then tensile tests were performed on a mechanical testing machine at a rate of 1 mm / min. The tensile strength was measured to be 451 MPa.

Claims

1. A method for producing a ceramic fiber-reinforced aluminum matrix composite based on stir casting, characterized by, The application relates to an aluminum alloy ceramic fiber composite material and a preparation method thereof. The aluminum alloy is heated to be fully molten in a stirring state, the surface oxide film is removed, then the pretreated ceramic fiber filaments are added, the stirring speed is increased to fully mix, then casting forming is carried out, and the aluminum alloy ceramic fiber composite material is obtained; The mass ratio of the aluminum alloy to the ceramic fiber filaments is 4-7:1; the ceramic fiber filaments are one of pure ceramic fibers and aluminum-based ceramic composite fibers; During the heating and fully melting process, the stirring speed is 50-70 r / min; during the fully mixing process, the stirring speed is 100-140 r / min, and the duration is 10-30 min; The aluminum alloy is placed in a smelting furnace, the temperature is increased from room temperature to 750-800 DEG C at a speed of 8-12 DEG C / min, and the temperature is kept for 1-3 h; Before the surface oxide film is removed, a cooling treatment is further needed, and the process is as follows: the heating is stopped, the aluminum alloy melt is cooled to 680-730 DEG C, and then the temperature is kept; The length of the pretreated ceramic fiber filaments is 100-150 mu m.

2. The method for preparing a ceramic fiber reinforced aluminum matrix composite based on stirring casting according to claim 1, characterized in that: The diameter of the pretreated ceramic fiber filaments is 10-30 mu m.

3. The method of claim 1, wherein the ceramic fiber reinforced aluminum matrix composite is prepared by a stir casting process. The casting forming process is as follows: the aluminum alloy melt mixed with the ceramic fiber filaments is poured into a graphite mold coated with a release agent, and the mold is cooled to be formed at room temperature.

4. The method of claim 3, wherein the ceramic fiber reinforced aluminum matrix composite is prepared by a stir casting process. The release agent is one of boron nitride, borate and silicon oil.

5. The method of claim 1, wherein the ceramic fiber reinforced aluminum matrix composite is prepared by a stir casting process. The pure ceramic fibers are at least one of silicon carbide fibers, silicon nitride fibers, carbon fibers and alumina fibers; the aluminum-based ceramic composite fibers are at least one of aluminum-based silicon carbide fibers, aluminum-based silicon nitride fibers, aluminum-based carbon fibers and aluminum-based alumina fibers.

6. The method of claim 5, wherein the ceramic fiber reinforced aluminum matrix composite is prepared by a stir casting process. The mass percentage of pure aluminum in the aluminum-based ceramic composite fibers is 40-60%.

7. A stir-cast ceramic fiber reinforced aluminum matrix composite material, characterized by: The aluminum alloy ceramic fiber composite material is prepared by the method. The application relates to an aluminum alloy ceramic fiber composite material and a preparation method thereof.

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