Method for synergistically improving modulus, obdurability and heat resistance of aluminum-based composite material by utilizing silicon carbide whisker network and intragranular rare earth covering precipitated phase

Abstract

The invention discloses a method for synergistically improving modulus, obdurability and heat resistance of an aluminum-based composite material by utilizing a silicon carbide whisker network and an intragranular rare earth covering precipitated phase, and belongs to the field of aluminum-based composite materials. The problems that according to an existing silicon carbide whisker reinforced aluminum matrix composite, the segregation behavior of rare earth elements on various interfaces such as a reinforcement body / matrix and a precipitated phase / matrix cannot be accurately regulated and controlled while homogenization and refinement of a matrix structure are difficult to achieve, and a multi-stage reinforced structure with high thermal stability cannot be constructed are solved. The method comprises the following steps: 1, preparing a silicon carbide whisker precast block; 2, preparing an alloy melt; 3, extruding and infiltrating to prepare an aluminum-based composite material; and 4, a tandem heat treatment-hot extrusion-heat treatment synergistic process. The method is used for synergistically improving the modulus, obdurability and heat resistance of the aluminum-based composite material by utilizing a silicon carbide whisker network and an intragranular rare earth covering precipitated phase.

Description

Technical Field

[0001] This invention belongs to the field of aluminum-based composite materials. Background Technology

[0002] High-strength heat-resistant aluminum alloys and their composites were developed to meet the development needs of advanced spacecraft, with the ultimate goal of obtaining lightweight, high-strength, and heat-resistant materials that can operate stably in the temperature range of 200℃ to 400℃. In recent years, significant progress has been made in the research of heat-resistant aluminum alloys, leading to novel microstructure design strategies such as atomic segregation at precipitate phase interfaces, ordered interstitial positions of heterogeneous atoms, and coherent coupling at multi-level heterogeneous phase interfaces. Among these, microalloyed deformable heat-resistant aluminum alloys under ingot metallurgical conditions (such as Al-Cu-Mg-Fe-Ni, Al-Cu-Mn, and Al-Cu-Mg-Ag systems) have significantly improved their high-temperature mechanical properties by introducing transition metals and rare earth elements (publication numbers CN 115323230 A, CN 102796927 A).

[0003] However, although microalloying and heat treatment optimization can improve the heat resistance of aluminum alloys to some extent, the inherent upper limit of their heat resistance and the poor dimensional stability caused by their high coefficient of thermal expansion are difficult to fundamentally solve, limiting their application in more advanced working conditions. Unlike traditional aluminum alloys, aluminum matrix composites combine the plasticity and toughness of the matrix alloy with the high specific modulus and high strength of the reinforcement by introducing highly thermally stable reinforcements (such as ceramic particles and whiskers) from the outside or generating them in situ within the matrix. They not only have higher specific strength and specific stiffness, but also exhibit better thermal conductivity, low expansion and dimensional stability, making them ideal lightweight structural materials for the aerospace field with broad application prospects (publication numbers CN112301298 B, CN 114134370 A).

[0004] Currently, the research frontier and consensus on improving the heat resistance of aluminum matrix composites lies in "synergistic reinforcement of the interface and matrix." The core strategy is to microalloy rare earth elements (such as Sc, Ce, and Y) to form thermally stable nano-precipitates within the aluminum matrix to strengthen it, while simultaneously inducing selective segregation of these elements at key interfaces, thereby fundamentally improving the thermal stability of the interfacial bonding. Silicon carbide whiskers (SiCw), due to their one-dimensional single-crystal structure and high thermal stability, are ideal reinforcements for constructing three-dimensional strengthening networks. Therefore, combining the load-bearing advantages of SiCw with the stabilizing effect of rare earth elements on the interface / matrix through heat treatment is considered an ideal way to achieve a combination of high modulus, strength, toughness, and heat resistance in materials. However, translating this theoretically perfect strategy into a controllable preparation process to systematically solve the core bottleneck of whisker debonding caused by interface weakening at high temperatures in SiCw-reinforced aluminum matrix composites faces the following deep-seated and mutually coupled process contradictions in current technologies:

[0005] 1. The "Unattainable Target" Contradiction of Interfacial Segregation: Existing successful "rare earth interfacial segregation" technologies in aluminum alloys mainly target the interface of intermetallic compound precipitates (such as the θ′ phase) within the matrix. However, SiCw and aluminum are heterogeneous systems with vastly different thermophysical properties. The segregation behavior, effective structure, and required process conditions of rare earth elements at ceramic / metal interfaces such as SiCw / Al may be completely different. Applying mature heat treatment procedures for precipitate interfaces cannot ensure the formation of an effective and stable segregated layer at the most critical reinforcement / matrix interface, resulting in the failure to achieve the goal of high-temperature interfacial strengthening.

[0006] 2. The "Conflict of Process Conditions" Between Microstructure Preparation and Interface Optimization: To obtain high-performance composite materials, it is necessary to break down the as-cast microstructure, densify it, and optimize the SiCw distribution (e.g., by constructing a three-dimensional network) through large-deformation hot extrusion. However, the brittle, low-melting-point phases in the as-cast microstructure are the root cause of extrusion cracking and need to be eliminated beforehand through long-term high-temperature homogenization. This process easily damages the initial state of the SiCw / Al interface and may even induce harmful reactions, directly conflicting with the thermodynamic premise of subsequently constructing a stable segregation interface. The specific heat treatment window aimed at optimizing interfacial segregation is also mutually constrained by the optimal process parameters required for hot processing.

[0007] 3. The Integration Dilemma of Multi-Level Structure "Collaborative Construction": The final high-temperature performance of a material depends on the synergy of three factors: refined matrix grains, optimized spatial distribution of reinforcements (especially "whisker internalization"), and stable multi-type interfaces (precipitates / matrix, SiCw / matrix). Existing technologies can usually only optimize one or two aspects, lacking a logically coherent and sequentially locked composite process chain that can smoothly advance the next stage without compromising the results of the previous stage.

[0008] In summary, although "achieving synergistic strengthening of the interface and matrix through rare earth microalloying" is a recognized cutting-edge direction, existing technologies lack a systematic process solution that can overcome the aforementioned contradictions and sequentially achieve this in silicon carbide whisker-reinforced aluminum matrix composites.

[0009] (1) The full homogenization and plasticity modification of the matrix lay the foundation for safe large deformation;

[0010] (2) The reinforcement network is optimized and the matrix grains are refined by actively reconstructing the microstructure through large deformation;

[0011] (3) Synergistically drive rare earth elements to achieve effective segregation at both the precipitate phase / matrix and the SiCw / Al reinforcement / matrix, thereby constructing a multi-level synergistic structure with high thermal stability.

[0012] Therefore, developing an innovative preparation process that can organically integrate and precisely solve the above-mentioned series of problems is the key to breaking through the high-temperature performance bottleneck of silicon carbide whisker-reinforced aluminum matrix composites and realizing their engineering applications. Summary of the Invention

[0013] This invention aims to address the problem that existing silicon carbide whisker-reinforced aluminum matrix composites are unable to achieve both homogenization and refinement of the matrix structure while precisely controlling the segregation behavior of rare earth elements at various interfaces such as the reinforcement / matrix and precipitates / matrix, thus failing to construct a multi-level reinforced structure with high thermal stability. Therefore, this invention provides a method that synergistically improves the modulus, strength, toughness, and heat resistance of aluminum matrix composites by utilizing a silicon carbide whisker network and intracrystalline rare earth-covered precipitates.

[0014] A method for synergistically improving the modulus, strength, toughness, and heat resistance of aluminum matrix composites using silicon carbide whisker networks and intracrystalline rare earth-covered precipitates is carried out according to the following steps:

[0015] I. Preparation of silicon carbide whisker preforms:

[0016] The rinsed silicon carbide whisker solution is stirred and dispersed evenly with water-soluble organic sol to obtain whisker slurry. The whisker slurry is added to a mold with drainage holes at the bottom and left to stand until the water has fully seeped out. Then it is pre-pressed to obtain a pre-formed whisker preform. The pre-formed whisker preform is sintered and shaped and the residual glue is removed to obtain a silicon carbide whisker preform.

[0017] II. Preparation of alloy melt:

[0018] Weigh the raw materials according to the mass percentage of each metal element in the alloy matrix material and melt them under an argon atmosphere to obtain alloy aluminum liquid.

[0019] III. Preparation of aluminum-based composite materials by extrusion impregnation:

[0020] The silicon carbide whisker preform is placed in the middle of the extrusion mold and heated and kept warm in the furnace. Then, some alloy aluminum liquid is poured into the gap between the silicon carbide whisker preform and the extrusion mold. The furnace is reheated and kept warm until the alloy aluminum liquid solidifies to fix the silicon carbide whisker preform. After keeping warm, the heating is stopped. At the same time as the heating is stopped, the remaining alloy aluminum liquid is poured into the gap between the silicon carbide whisker preform and the extrusion mold. Secondary pressurization is carried out during the furnace cooling process. Finally, the furnace is demolded and the surrounding uninfiltrated aluminum alloy is removed to obtain an aluminum-based composite material ingot.

[0021] IV. Series-type heat treatment-hot extrusion-heat treatment synergistic process:

[0022] ① The aluminum-based composite material ingot is subjected to a two-stage homogenization process, and then removed and cooled by water quenching to obtain the homogenized composite material.

[0023] ② The homogenized composite material is subjected to large deformation hot extrusion, and finally water quenching and cooling to obtain extruded bars;

[0024] ③ The extruded bar is subjected to a short-time high-temperature solution treatment, then removed and water-quenched to obtain the solution-treated bar.

[0025] ④ The solution-treated rods are subjected to multi-stage aging treatment to obtain an aluminum-based composite material that is synergistically reinforced by silicon carbide whisker network and intracrystalline rare earth covering precipitates.

[0026] The beneficial effects of this invention are:

[0027] The aluminum-based composite material and its preparation method provided by this invention, through a series of interconnected and interlocking process designs, form the following difficult-to-imitate technical barriers and significant effects:

[0028] 1. This invention solves the problem of synergistic aggregation of rare earth elements at multiple interfaces, constructing an indivisible multi-level synergistic structure: Through a precisely sequential process chain of "long-term homogenization → large deformation extrusion → short-time solid solution / multi-level aging," this invention systematically solves the "interface positioning" and "process conflict" problems mentioned in the background technology. Homogenization provides a pure matrix free of harmful phases for subsequent large deformation; extrusion, while achieving microstructure refinement and "whisker internalization," creates numerous fresh and clean interfaces; the final multi-level aging process precisely drives rare earth elements such as Sc and Ce to selectively aggregate simultaneously at the SiCw / Al interface and the precipitated phase / matrix interface, forming nanoscale diffusion barriers at both key interfaces. This series of operations is interconnected, ultimately constructing a unique and high-performance multi-level synergistic structure within the composite material: "fine equiaxed crystalline matrix + three-dimensional network and partially internalized SiC whiskers + intracrystalline nano-heat-resistant phase with synergistic rare earth aggregation at the interface." The absence of any single step or deviation of parameters will disrupt the achievement of this multi-interface synergistic clustering, causing the entire synergistic effect to fail.

[0029] 2. Achieved proactive design and precise positioning of microstructure: Unlike the random results of traditional processes, this invention completely eliminates the non-equilibrium second phase at medium and low temperatures through homogenization heat treatment, creating a pure matrix for subsequent extrusion; utilizes the extrusion process to break up coarse grains under the "cutting" of the SiCw network and actively achieve "whisker internalization"; and performs short-time solid solution and multi-interface segregation control based on the aforementioned ideal structure. This series of operations achieves proactive design and precise positioning of reinforcement distribution (intra-crystalline / inter-crystalline), matrix grain size, and multiple interface states (rare earth segregation), presenting a high technological barrier.

[0030] 3. Excellent performance stability across temperature ranges was achieved through multi-interface rare-earth segregation engineering: This material exhibits high strength and high modulus at room temperature, primarily due to the combined effects of fine-grained strengthening, precipitate phase strengthening, and whisker load transfer. At high temperatures of 200℃~400℃, when the matrix softens, the strengthening mechanism is dominated by the mechanical constraint of the thermally highly stable three-dimensional SiC whisker network and the enhanced interfacial chemical stability resulting from the dual segregation of rare earth elements at the reinforcement / matrix and precipitate / matrix interfaces. The segregation of rare earth elements at the precipitate interface effectively pins the phase boundary, inhibiting the coarsening and dissolution of the heat-resistant precipitate at high temperatures; the segregation at the SiCw / Al interface significantly enhances the interfacial bonding force between the reinforcement and the matrix at high temperatures, fundamentally suppressing performance degradation caused by high-temperature interfacial weakening. This achieves a smooth transition and high performance retention from room temperature to medium-high temperatures, solving the core problem of high-temperature interfacial weakening in traditional whisker-reinforced composite materials.

[0031] 4. Process robustness and performance repeatability: Since each process step (especially creating a clean, uniform, and refined precursor structure for interfacial segregation) creates clear and necessary conditions for the next step (especially multi-interfacial rare earth segregation), the entire process chain has inherent logical consistency and robustness, which is conducive to obtaining composite material products with stable performance and high repeatability, and has the potential for industrial production. Attached Figure Description

[0032] Figure 1 SiC prepared in Example 1 w / Al-Cu-Mg-Ag-0.5Ce aluminum-based composite material and SiC prepared in Comparative Experiment 1 w Room temperature tensile stress-strain curve of Al-Cu-Mg-Ag aluminum matrix composite material;

[0033] Figure 2 SiC prepared in Example 1 w / Al-Cu-Mg-Ag-0.5Ce aluminum-based composite material, and SiC prepared in Comparative Experiment 1 w High-temperature tensile (300℃) stress-strain curves of Al-Cu-Mg-Ag aluminum matrix composite material and Al-Cu-Mg-Ag aluminum alloy prepared in Comparative Experiment 2;

[0034] Figure 3 SiC prepared in Example 1 w TEM characterization results of the interfacial phase of the Al-Cu-Mg-Ag-0.5Ce aluminum-based composite material;

[0035] Figure 4 SiC prepared in Example 1 w TEM characterization results of intragranular precipitates in Al-Cu-Mg-Ag-0.5Ce aluminum-based composite materials;

[0036] Figure 5 SiC prepared in Example 1 w SEM microstructure characterization results of Al-Cu-Mg-Ag-0.5Ce aluminum-based composite materials;

[0037] Figure 6 SiC prepared in Example 1 w EBSD microstructure characterization results of Al-Cu-Mg-Ag-0.5Ce aluminum-based composite materials;

[0038] Figure 7 To compare the SiC prepared in Experiment 3 w TEM characterization results of the interfacial phase of the Al-Cu-Mg-Ag-0.5Ce aluminum-based composite material. Detailed Implementation

[0039] Specific Implementation Method 1: This implementation method utilizes a silicon carbide whisker network and intracrystalline rare earth-covered precipitates to synergistically improve the modulus, strength, toughness, and heat resistance of aluminum-based composite materials. It is carried out according to the following steps:

[0040] I. Preparation of silicon carbide whisker preforms:

[0041] The rinsed silicon carbide whisker solution is stirred and dispersed evenly with water-soluble organic sol to obtain whisker slurry. The whisker slurry is added to a mold with drainage holes at the bottom and left to stand until the water has fully seeped out. Then it is pre-pressed to obtain a pre-formed whisker preform. The pre-formed whisker preform is sintered and shaped and the residual glue is removed to obtain a silicon carbide whisker preform.

[0042] II. Preparation of alloy melt:

[0043] Weigh the raw materials according to the mass percentage of each metal element in the alloy matrix material and melt them under an argon atmosphere to obtain alloy aluminum liquid.

[0044] III. Preparation of aluminum-based composite materials by extrusion impregnation:

[0045] The silicon carbide whisker preform is placed in the middle of the extrusion mold and heated and kept warm in the furnace. Then, some alloy aluminum liquid is poured into the gap between the silicon carbide whisker preform and the extrusion mold. The furnace is reheated and kept warm until the alloy aluminum liquid solidifies to fix the silicon carbide whisker preform. After keeping warm, the heating is stopped. At the same time as the heating is stopped, the remaining alloy aluminum liquid is poured into the gap between the silicon carbide whisker preform and the extrusion mold. Secondary pressurization is carried out during the furnace cooling process. Finally, the furnace is demolded and the surrounding uninfiltrated aluminum alloy is removed to obtain an aluminum-based composite material ingot.

[0046] IV. Series-type heat treatment-hot extrusion-heat treatment synergistic process:

[0047] ① The aluminum-based composite material ingot is subjected to a two-stage homogenization process, and then removed and cooled by water quenching to obtain the homogenized composite material.

[0048] ② The homogenized composite material is subjected to large deformation hot extrusion, and finally water quenching and cooling to obtain extruded bars;

[0049] ③ The extruded bar is subjected to a short-time high-temperature solution treatment, then removed and water-quenched to obtain the solution-treated bar.

[0050] ④ The solution-treated rods are subjected to multi-stage aging treatment to obtain an aluminum-based composite material that is synergistically reinforced by silicon carbide whisker network and intracrystalline rare earth covering precipitates.

[0051] In step one of this specific embodiment, to ensure that the finished whisker preform has a complete structure and sufficient strength, an appropriate amount of mixed adhesive needs to be added. After the whisker solution and the mixed adhesive are stirred to obtain a uniform whisker slurry, it is poured into a special mold and left to stand. The mold has drainage holes at the bottom, which allow water to seep through, but the whiskers will not seep through.

[0052] In this specific embodiment, step three of the composite material die-casting process includes three processes: placement of the preform and mold, casting ring, and secondary pressurization. A steel mold is used to prepare the composite material. To expel residual gas from the preform and ensure the molten aluminum alloy fully penetrates the preform, a gas vent hole is provided on the bottom surface of the mold. During the pouring of the molten aluminum alloy, a special copper pressure head is placed above the preform. After casting the ring, it is removed with clamps to prevent the molten aluminum alloy from covering the upper surface of the preform during casting.

[0053] Step four of this specific implementation method, the tandem heat treatment-hot extrusion-heat treatment synergistic process, is key to forming a high-performance microstructure. Its technical barrier lies in the progressive objectives and interlocking conditions of the three sub-steps:

[0054] 1. Long-term two-stage homogenization heat treatment – ​​creating a "pure and malleable" matrix prerequisite for controllable large deformation hot extrusion:

[0055] The primary objective of this process is to specifically and completely eliminate low-to-medium temperature non-equilibrium second phases (such as S-Al2CuMg and θ-Al2Cu phases) in the as-cast microstructure that may melt within the subsequent hot extrusion temperature range (300℃~520℃). These phases can locally liquefy or soften during hot deformation, becoming crack initiation points and severely deteriorating workability. Simultaneously, this treatment significantly improves the morphology and distribution of high-melting-point insoluble phases (such as MnFe-rich and CuCe-rich phases), making them spheroidized and refined. This step provides the necessary, uniform, and highly ductile matrix conditions for subsequent large deformation. Its temperature and time windows are closely coupled with the subsequent extrusion temperature window, making it an irreplaceable prerequisite for achieving large deformation without cracking.

[0056] 2. Large Deformation Hot Extrusion – Achieving Synergy Between “Tissue Fracture and Reconstruction” and “Whisker Internalization and Positioning”:

[0057] This step achieves two main goals based on the "pure matrix" provided by homogenization:

[0058] (1) Structure fragmentation and densification: Large plastic deformation is used to close the casting pores, break the original coarse grains and the homogenized and improved insoluble phases, introduce high-density dislocations, promote dynamic recrystallization, and form fine equiaxed crystals.

[0059] (2) Whisker “internalization” design: The key innovation lies in using a pre-constructed three-dimensional continuous, high-hardness SiC whisker network as a “rigid skeleton” and “cutting template”. During extrusion deformation, the migrating grain boundaries are strongly pinned and cut by the network whiskers, and newly formed fine recrystallized grains are formed in the gaps of the whisker network. By controlling the extrusion parameters, some whiskers are actively encouraged to be wrapped inside the newly formed grains, thus achieving “whisker internalization”. This directly upgrades the reinforcement from an intergranular barrier to a direct barrier to the movement of dislocations within the grain.

[0060] The success of this step depends entirely on the quality of the homogenization process. Precise control of extrusion parameters (temperature, speed, deformation) directly determines the degree of grain refinement and the proportion of "whisker incorporation".

[0061] 3. Short-duration high-temperature solution treatment and multi-stage aging – constructing a thermally stable interface on an “ideal precursor structure”:

[0062] (1) Solution treatment: Since the first two steps have already obtained a microstructure with uniform composition, fine grains and improved insoluble phases, only a short-term high-temperature solution treatment is needed to allow the main strengthening elements to dissolve rapidly into the matrix, while effectively inhibiting grain growth caused by long-term high-temperature exposure. This is thanks to the fact that homogenization and extrusion have eliminated the unstable factors in the microstructure in advance.

[0063] (2) Aging treatment: Promotes the dispersion of heat-resistant precipitates. Through multi-stage aging temperature and time design, slow-diffusion elements such as Sc and Ce are driven to selectively segregate at the precipitate / matrix interface and SiC. w The matrix interface forms a nanoscale diffusion barrier, which greatly improves the thermal stability of the interface.

[0064] The efficiency and effectiveness of this step are directly determined by the "ideal precursor microstructure" formed by long-term two-stage homogenization heat treatment and large-deformation hot extrusion. Without the improvement of the insoluble phase by homogenization treatment and the fine-grained microstructure brought about by extrusion, conventional solid solution treatment would be unable to balance the contradiction between solute dissolution and grain coarsening.

[0065] The core innovation of this specific implementation lies in proposing and implementing a set of heat treatment and hot deformation process chains with rigorous sequential logic and interdependent conditions. This process chain, through "step-by-step conditional processing," sequentially solves key issues such as the uniformity of the as-cast microstructure, optimization of the spatial distribution of the reinforcement, refinement and control of the matrix grains, and improvement of the interface thermal stability. Ultimately, it constructs an indivisible multi-level synergistic reinforcement structure within the composite material, forming a significant technological barrier.

[0066] 1. Core collaborative structure and micro-organizational characteristics:

[0067] The composite material described in this specific embodiment uses an alloy as the matrix material and silicon carbide whiskers (SiCw) as the reinforcement. Through the preparation method, a microstructure with the following characteristics can be obtained:

[0068] At room temperature, the composite material exhibits a unique multi-scale structure: SiC whisker reinforcements, distributed in a three-dimensional network across grain boundaries, tightly encapsulate the aluminum matrix grains, providing excellent load transfer and grain boundary pinning effect; simultaneously, within the aluminum alloy matrix, heat-resistant precipitates (such as θ′ phases) selectively covered or segregated by rare earth elements such as Sc / Ce are uniformly distributed. These rare earth elements in SiC... w Segregation at the Al interface and the precipitated phase / matrix interface forms a chemically ordered nanoscale transition layer.

[0069] 2. Synergistic reinforcement and toughening mechanisms over a wide temperature range:

[0070] The aforementioned unique microstructure leads to a synergistic effect of "strengthening" and "toughening" mechanisms, ensuring the material's excellent performance across a wide temperature range.

[0071] (1) Synergistic strengthening mechanism: In the medium and high temperature environment of 200℃~400℃, the triple mechanism of nanocrystal strengthening, SiC whisker grain boundary pinning strengthening and intracrystalline whisker / heat-resistant precipitation phase dislocation pinning strengthening works together to effectively hinder dislocation movement and grain boundary slip, ensuring that the material can stably maintain high mechanical properties at high temperature.

[0072] (2) Synergistic toughening mechanism: The nanocrystalline structure itself has the ability to coordinate deformation; at the same time, the rare earth element interfacial segregation significantly improves the bonding and compatibility of key interfaces such as intracrystalline precipitates-matrix, reinforcement-matrix and grain boundaries. Under the combined effect of these two toughening mechanisms, the aluminum-based composite material exhibits good plasticity and toughness in the range from room temperature to 400℃, thus possessing excellent subsequent processing and forming properties.

[0073] 3. Principle:

[0074] This specific implementation method utilizes the core principle of "multi-level synergy between reinforcement, precipitates, and matrix through rare earth element interfacial segregation," and is not limited to the aforementioned specific alloy system. This principle is also applicable to other heat-treatable strengthened aluminum alloys capable of forming heat-resistant precipitates and interacting with rare earth elements at the interface, such as Al-RE, Al-Cu-Mg-RE, Al-Ni-Fe, and Al-Zn-Mg-Cu systems. When applied to different alloy systems, the specific process parameters need to be adjusted according to the phase diagram and precipitation characteristics of the alloy, but the core objective remains the same: to achieve effective segregation of the rare earth elements at key interfaces, thereby constructing a similar synergistic strengthening structure.

[0075] The beneficial effects of this specific implementation method are:

[0076] The aluminum-based composite material and its preparation method provided in this specific embodiment, through a series of interconnected and interlocking process designs, form the following difficult-to-imitate technical barriers and significant effects:

[0077] 1. This invention solves the problem of synergistic aggregation of rare earth elements at multiple interfaces, constructing an indivisible multi-level synergistic structure: This specific implementation systematically solves the "interface positioning" and "process conflict" problems mentioned in the background technology through a precise series of processes: "long-term homogenization → large deformation extrusion → short-time solid solution / multi-level aging". Homogenization provides a pure matrix free of harmful phases for subsequent large deformation; extrusion, while achieving microstructure refinement and "whisker internalization", creates a large number of fresh and clean interfaces; the final multi-level aging process precisely drives rare earth elements such as Sc and Ce to selectively aggregate at both the SiCw / Al interface and the precipitated phase / matrix interface, simultaneously forming nanoscale diffusion barriers at the two key interfaces. This series of operations are interconnected, ultimately constructing a unique and high-performance multi-level synergistic structure in the composite material: "fine equiaxed crystalline matrix + three-dimensional network and partially internalized SiC whiskers + intracrystalline nano-heat-resistant phase with synergistic aggregation of rare earth elements at the interface". The absence of any single step or deviation of parameters will disrupt the achievement of this multi-interface synergistic clustering, causing the entire synergistic effect to fail.

[0078] 2. Active design and precise positioning of microstructure: Unlike the random results of traditional processes, this specific implementation completely eliminates the non-equilibrium second phase at medium and low temperatures through homogenization heat treatment, creating a pure matrix for subsequent extrusion; it utilizes the extrusion process to break up coarse grains under the "cutting" of the SiCw network and actively achieves "whisker internalization"; and it performs short-time solid solution and multi-interface segregation control based on the aforementioned ideal structure. This series of operations achieves active design and precise positioning of reinforcement distribution (intra-crystalline / inter-crystalline), matrix grain size, and multiple interface states (rare earth segregation), representing a high technological barrier.

[0079] 3. Excellent performance stability across temperature ranges was achieved through multi-interface rare-earth segregation engineering: This material exhibits high strength and high modulus at room temperature, primarily due to the combined effects of fine-grained strengthening, precipitate phase strengthening, and whisker load transfer. At high temperatures of 200℃~400℃, when the matrix softens, the strengthening mechanism is dominated by the mechanical constraint of the thermally highly stable three-dimensional SiC whisker network and the enhanced interfacial chemical stability resulting from the dual segregation of rare earth elements at the reinforcement / matrix and precipitate / matrix interfaces. The segregation of rare earth elements at the precipitate interface effectively pins the phase boundary, inhibiting the coarsening and dissolution of the heat-resistant precipitate at high temperatures; the segregation at the SiCw / Al interface significantly enhances the interfacial bonding force between the reinforcement and the matrix at high temperatures, fundamentally suppressing performance degradation caused by high-temperature interfacial weakening. This achieves a smooth transition and high performance retention from room temperature to medium-high temperatures, solving the core problem of high-temperature interfacial weakening in traditional whisker-reinforced composite materials.

[0080] 4. Process robustness and performance repeatability: Since each process step (especially creating a clean, uniform, and refined precursor structure for interfacial segregation) creates clear and necessary conditions for the next step (especially multi-interfacial rare earth segregation), the entire process chain has inherent logical consistency and robustness, which is conducive to obtaining composite material products with stable performance and high repeatability, and has the potential for industrial production.

[0081] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the silicon carbide whisker solution after rinsing in step one is prepared according to the following steps: The silicon carbide whiskers are soaked in a mixed acid. First, the mixture is stirred for 2 to 12 hours at room temperature and a stirring speed of 200 to 600 r / min. Then, the mixture is kept at a temperature of 75 to 90°C for 6 to 24 hours. Finally, the mixture is stirred for 1 to 2 hours at room temperature and a stirring speed of 200 to 600 r / min to obtain acid-washed silicon carbide whiskers. Distilled water is added to the acid-washed silicon carbide whiskers and allowed to stand to allow the whiskers to precipitate. Then, the water is removed. The process of adding distilled water, precipitation, and water removal is repeated multiple times until the pH of the removed water is 6 to 7. Finally, the water is drained to obtain the rinsed silicon carbide whisker solution.

[0082] The silicon carbide whiskers have a diameter of 100 nm to 1.5 µm and a length of 10 µm to 100 µm; the mixed acid is composed of hydrofluoric acid solution, sulfuric acid solution, and water, with a volume ratio of hydrofluoric acid solution to sulfuric acid solution of 1:(0.5~1), and a volume ratio of the total volume of hydrofluoric acid solution and sulfuric acid solution to the volume of water of 1:(5~9); the mass percentage of the hydrofluoric acid solution is 49%, and the mass percentage of the sulfuric acid solution is 98%. Other aspects are the same as in Specific Embodiment 1.

[0083] In this specific embodiment, sulfuric acid is used to remove residual catalysts Fe and Ni from the whisker production process; the acid washing process causes the amorphous carbon on the surface of the whisker to peel off from the whisker and float to the liquid surface, and also causes the residual catalysts Fe and Ni to react with the acid to form soluble salts.

[0084] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: the water-soluble organic sol mentioned in step one is composed of water, silica gel, and polysilazane, and the volume ratio of polysilazane to silica gel is 1:(2~4), and the volume ratio of polysilazane to water is 1:(20~50); the mass percentage of the rinsed silicon carbide whiskers in the rinsed silicon carbide whisker solution mentioned in step one is 25%~35%; in step one, 0.5mL~1.5mL of water-soluble organic sol is added to every 1g of rinsed silicon carbide whisker solution; the pre-compression mentioned in step one is specifically carried out under a pressure of 10MPa~100MPa for 2h~24h. Everything else is the same as in Specific Implementation Method One or Two.

[0085] In the water-soluble organic sol described in this specific embodiment, silica gel plays a good role in the low-temperature range (room temperature to about 850°C), preventing cracking during the moisture removal stage and the subsequent heating to 850°C; polysilazane is mainly used to improve the compressive strength of the preform, preventing deformation or cracking under the pressure applied during the aluminum alloy impregnation process due to insufficient compressive strength of the preform.

[0086] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the sintering and shaping and removal of residual adhesive in step one are specifically carried out as follows: First, the temperature is maintained at 40℃~60℃ for 12h~36h; then, it is maintained at 80℃~90℃ for 12h~36h; then, it is maintained at 100℃~120℃ for 12h~36h; then, the temperature is increased to 700℃~900℃ at a rate not exceeding 2℃ / min, and maintained at 700℃~900℃ for 1h~4h; after maintenance, it is cooled to room temperature in the furnace; then, it is sintered under vacuum at 1100℃~1300℃ for 1h~4h to obtain silicon carbide whisker preforms with a compressive strength of 7MPa~10MPa. The rest is the same as in Specific Implementation Methods One to Three.

[0087] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the alloy matrix material mentioned in step two is an Al-RE alloy, an Al-Cu-Mg-RE alloy, an Al-Ni-Fe-RE alloy, an Al-Cu-Mg-Ag-RE alloy, or an Al-Zn-Mg-Cu-RE alloy, wherein RE is one or a combination of Ce, Sc, Y, and Zr. Everything else is the same as in Specific Implementation Methods One to Four.

[0088] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: when the alloy matrix material mentioned in step two is an Al-Cu-Mg-Ag-RE alloy, the Al-Cu-Mg-Ag-RE alloy is composed of 3.6%~6.0% Cu, 0.4%~2.0% Mg, 0.2%~0.8% Mn, 0.3%~1.0% Ag, 0.1%~2.0% RE, and the balance Al by mass percentage, wherein RE is one or a combination of Ce, Sc, Y, and Zr; the raw materials mentioned in step two are pure Al, Al-Mn alloy, Al-Cu alloy, pure Ag, pure Mg, and Al-RE alloy, wherein the Al-RE alloy is one or a combination of Al-Ce alloy, Al-Sc alloy, Al-Y alloy, and Al-Zr alloy; the melting under an argon atmosphere mentioned in step two is specifically carried out according to the following steps: ① Under an argon atmosphere ① Pure Al, Al-Mn alloy, Al-Cu alloy, and pure Ag are heated and melted at an atmosphere and temperature of 760℃~800℃ to obtain a first melt; ② Under an argon atmosphere and temperature of 750℃~780℃, an aluminum foil-wrapped degassing agent is pressed into the bottom of the first melt using a bell jar. After the degassing agent and the first melt have completely reacted and no more gas is produced, the slag is removed to obtain the melt after slag removal; the mass ratio of the degassing agent to the first melt is 1:(0.005~0.005). 02), the degassing agent is hexachloroethane; ③ Under an argon atmosphere and a temperature of 750℃~780℃, pure Mg and Al-RE alloy wrapped in aluminum foil is pressed into the slag-removed melt using a bell jar, and allowed to stand for 5min~30min to obtain a second melt; ④ Under an argon atmosphere, a temperature of 760℃~850℃, and a stirring speed of 200r / min~800r / min, the second melt is stirred for 5min~15min to obtain alloy aluminum liquid. Other aspects are the same as in specific embodiments one to five.

[0089] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: the extrusion die in step three consists of a die sleeve and a bottom graphite gasket, and the bottom graphite gasket has ventilation holes; the placement of the silicon carbide whisker preform in the middle of the extrusion die and its subsequent heating and heat preservation in the furnace in step three is specifically carried out at a temperature of 560℃~620℃ for 0.5h~2h; the reheating and heat preservation in step three until the alloy aluminum liquid solidifies to fix the silicon carbide whisker preform is carried out according to the following steps: reheating to 560℃~620℃ and holding at 560℃~620℃ for 30min~60min; the secondary pressurization in step three specifically involves first holding at a low pressure of 5MPa~6MPa for 1min~2min, and then holding at a high pressure of 200MPa~230MPa for 5min~10min. Everything else is the same as in Specific Implementation Methods One to Six.

[0090] In this specific embodiment, in order to obtain higher density and interfacial bonding strength, but to avoid interfacial reactions, the low pressure is increased to 5MPa~6MPa and the high pressure is increased to 200MPa~230MPa.

[0091] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the secondary homogenization treatment described in step four① is specifically carried out according to the following steps: first, maintain the temperature at 420℃~490℃ for 48h~96h, and then maintain the temperature at 500℃~530℃ for 4h~10h. Everything else is the same as in Specific Implementation Methods One to Seven.

[0092] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that: the large deformation hot extrusion described in step four ② is specifically carried out according to the following steps: first, holding at a temperature of 300℃~520℃ for 0.5h~2h, and then hot extrusion deformation is performed at a temperature of 300℃~520℃ and a metal outflow rate of 0.5m / min~3m / min, with an extrusion ratio of (9~40):1; the short-time high-temperature solution treatment described in step four ③ is specifically carried out according to the following steps: holding at a temperature of 530℃~600℃ for 10min~60min. Everything else is the same as in Specific Implementation Methods One to Eight.

[0093] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that the multi-stage aging treatment described in step four (④) is specifically carried out according to the following steps: First, at a temperature of 150℃~200℃, it is held for 1h~8h, then water-quenched to room temperature; then, at a temperature of 200℃~250℃, it is held for 0h~16h, then water-quenched to room temperature; finally, at a temperature of 250℃~300℃, it is held for 0h~16h, then water-quenched to room temperature; the volume percentage of silicon carbide whiskers in the aluminum-based composite material synergistically reinforced by the silicon carbide whisker network and intracrystalline rare earth covered precipitates in step four (④) is 15%~40%. Everything else is the same as in Specific Implementation Methods One to Nine.

[0094] The beneficial effects of the present invention are verified using the following embodiments:

[0095] Example 1:

[0096] A method for synergistically improving the modulus, strength, toughness, and heat resistance of aluminum matrix composites using silicon carbide whisker networks and intracrystalline rare earth-covered precipitates is carried out according to the following steps:

[0097] I. Preparation of silicon carbide whisker preforms:

[0098] Weigh out 1 mL of water-soluble organic sol for every 1 g of rinsed silicon carbide whisker solution. Stir and disperse the rinsed silicon carbide whiskers and water-soluble organic sol evenly to obtain whisker slurry. Add the whisker slurry to a mold with drainage holes at the bottom and let it stand until the water has fully seeped out. Then, pre-press it for 12 hours under a pressure of 20 MPa to obtain a pre-formed whisker preform. Hold the pre-formed whisker preform at 60°C for 24 hours, then at 90°C for 24 hours, then at 105°C for 24 hours. Then, raise the temperature to 800°C at a rate not exceeding 2°C / min and hold it at 800°C for 2 hours. After holding, cool it to room temperature in the furnace and then sinter it under vacuum at 1200°C for 2 hours to obtain a silicon carbide whisker preform.

[0099] The water-soluble organic sol is composed of water, silica gel and polysilazane, and the volume ratio of polysilazane to silica gel is 1:2, and the volume ratio of polysilazane to water is 1:40.

[0100] The silica gel is alkaline silica gel with a pH value of 9. The mass percentage of silica in the alkaline silica gel is 30%~31%, and the average particle size of silica is 10nm~20nm.

[0101] The purity of the polysilazane is 98%~99%;

[0102] The pre-formed whisker preform has a diameter of 60 mm and a height of 20 mm.

[0103] The compressive strength of the silicon carbide whisker preform is 8 MPa;

[0104] II. Preparation of alloy melt:

[0105] Weigh out pure Al, Al-20Mn alloy, Al-50Cu alloy, pure Ag, pure Mg and Al-30Ce alloy as raw materials with a mass percentage of 4.2% Cu, 1.0% Mg, 0.4% Mn, 0.4% Ag, 0.5% Ce and balance Al, and then melt them under an argon atmosphere to obtain alloy aluminum liquid.

[0106] The melting process under an argon atmosphere is specifically carried out according to the following steps:

[0107] ① Under an argon atmosphere and at a temperature of 800℃, pure Al, Al-20Mn alloy, Al-50Cu alloy and pure Ag were heated and melted to obtain the first melt;

[0108] ② Under an argon atmosphere and a temperature of 760℃, the degassing agent wrapped in aluminum foil is pressed into the bottom of the first melt using a bell jar. After the degassing agent and the first melt have completely reacted and no more gas is produced, the slag is removed to obtain the melt after slag removal.

[0109] The mass ratio of the degassing agent to the first melt is 1:0.01, and the degassing agent is hexachloroethane;

[0110] ③ Under an argon atmosphere and at a temperature of 780℃, pure Mg and Al-30Ce alloy wrapped in aluminum foil was pressed into the melt after slag removal using a bell jar, and allowed to stand for 5 minutes to obtain the second melt.

[0111] ④ Under the conditions of argon atmosphere, temperature of 800℃ and stirring speed of 400r / min, the second melt is stirred for 5min to obtain alloy aluminum liquid;

[0112] III. Preparation of aluminum-based composite materials by extrusion impregnation:

[0113] A silicon carbide whisker preform is placed in the middle of an 80mm extrusion die and heated in the furnace at 580℃ for 30 minutes. Then, some molten aluminum alloy is poured into the gap between the silicon carbide whisker preform and the extrusion die. The furnace is then heated to 580℃ and held at 580℃ for 30 minutes until the molten aluminum alloy solidifies to fix the silicon carbide whisker preform. After holding at 580℃, the heating is stopped. At the same time as the heating is stopped, the remaining molten aluminum alloy is poured into the gap between the silicon carbide whisker preform and the extrusion die. During the furnace cooling process, the furnace is first held at a low pressure of 5MPa for 1 minute, and then held at a high pressure of 200MPa for 6 minutes. Finally, the furnace is demolded and the surrounding uninfiltrated aluminum alloy is removed to obtain an aluminum-based composite material ingot.

[0114] The extrusion die is composed of a die sleeve and a bottom graphite gasket, and the bottom graphite gasket is provided with vent holes;

[0115] IV. Series-type heat treatment-hot extrusion-heat treatment synergistic process:

[0116] ① In a muffle furnace, the aluminum-based composite material ingot is first held at 480℃ for 48 hours, and then held at 525℃ for 8 hours. After being taken out, it is cooled by water quenching to obtain a homogenized composite material.

[0117] ② The homogenized composite material is processed into a diameter of 59mm and a height of 20mm. Using a 200T press, a layer of graphite oil is applied to the inner wall of the mold and the extrusion cup. Then, a pure aluminum sheet with a thickness of 5mm, the homogenized composite material and 6 graphite pads with a thickness of 8mm are placed in sequence. The ring heating aluminum is used for heating. First, the homogenized composite material is kept at a temperature of 450℃ for 0.5h. Then, at a temperature of 450℃ and a metal flow rate of 1.5m / min, hot extrusion deformation is carried out at an extrusion ratio of 16:1. Finally, it is water quenched and cooled to obtain the extruded bar.

[0118] ③ Under the condition of 530℃, the extruded bar is subjected to short-time high-temperature solution treatment for 60 minutes, and then cooled by water quenching to obtain the solution-treated bar.

[0119] ④ The solution-treated rods were aged for 2.5 hours at 180℃, then held at that temperature and water-quenched to room temperature to obtain an aluminum-based composite material, SiC, which is synergistically reinforced by silicon carbide whisker networks and intragranular rare earth-covered precipitates. w / Al-Cu-Mg-Ag-0.5Ce aluminum-based composite material;

[0120] The volume percentage of silicon carbide whiskers in the aluminum matrix composite material that is synergistically reinforced by the silicon carbide whisker network and the intracrystalline rare earth covering precipitates is 28%.

[0121] The rinsed silicon carbide whisker solution described in step one is prepared according to the following steps: Silicon carbide whiskers are immersed in a mixed acid, first stirred for 12 hours at room temperature and a stirring speed of 200 r / min, then kept at 80℃ for 12 hours, and finally stirred for 2 hours at room temperature and a stirring speed of 200 r / min to obtain acid-washed silicon carbide whiskers. Distilled water is added to the acid-washed silicon carbide whiskers and allowed to stand for 24 hours to allow the whiskers to precipitate. The water is then removed, and this process of adding distilled water, precipitation, and water removal is repeated multiple times until all water is removed. The pH was set to 6, and the solution was drained to obtain a rinsed silicon carbide whisker solution. The mass percentage of the rinsed silicon carbide whiskers in the rinsed silicon carbide whisker solution was 30%. The average diameter of the silicon carbide whiskers was 600 nm, and the average length was 14 µm. The mixed acid was composed of hydrofluoric acid solution, sulfuric acid solution, and water, with a volume ratio of hydrofluoric acid solution to sulfuric acid solution of 1:1 and a total volume ratio of hydrofluoric acid solution to water of 1:8. The mass percentage of the hydrofluoric acid solution was 49%, and the mass percentage of the sulfuric acid solution was 98%.

[0122] Comparative Experiment 1: This embodiment differs from Embodiment 1 in that: in step 2, pure Al, Al-20Mn alloy, Al-50Cu alloy, pure Ag, and pure Mg were weighed as raw materials with a mass percentage of 4.2% Cu, 1.0% Mg, 0.4% Mn, 0.4% Ag, and the balance Al. These were then melted under an argon atmosphere to obtain an alloy aluminum liquid; in step 4, SiC was prepared. w / Al-Cu-Mg-Ag aluminum-based composite material. Everything else is the same as in Example 1.

[0123] Comparative Experiment 2: This comparative experiment differs from Example 1 in that steps 1 and 3 are omitted; in step 2, pure Al, Al-20Mn alloy, Al-50Cu alloy, pure Ag, and pure Mg are weighed as raw materials with mass percentages of 4.2% Cu, 1.0% Mg, 0.4% Mn, 0.4% Ag, and the balance Al, and then melted under an argon atmosphere to obtain an alloy aluminum liquid; in step 2④, the second melt is stirred for 5 minutes under an argon atmosphere, a temperature of 760℃, and a stirring speed of 400 r / min, and then poured into a Φ60mm steel mold and air-cooled to obtain... Step 4.2: The homogenized aluminum alloy is processed into a diameter of 59 mm and a height of 20 mm. On a 200T press, a layer of graphite oil is applied to the inner wall of the die and the extrusion cup. Then, the homogenized aluminum alloy and six 8 mm thick graphite pads are placed in sequence. The mixture is heated using a ring-shaped aluminum heater. The homogenized aluminum alloy is first held at 450℃ for 0.5 h, then hot-extruded at an extrusion ratio of 25:1. Finally, it is water-cooled to obtain an extruded bar. Step 4.3: The Al-Cu-Mg-Ag aluminum alloy is prepared. Other steps are the same as in Example 1.

[0124] Comparative Experiment 3: This example differs from Example 1 in that: in step 4③, the extruded bar is solution treated for 60 minutes at a temperature of 500℃, then removed and water-quenched to obtain the solution-treated bar. Everything else is the same as in Example 1.

[0125] Figure 1 SiC prepared in Example 1 w / Al-Cu-Mg-Ag-0.5Ce aluminum-based composite material and SiC prepared in Comparative Experiment 1 w The room temperature tensile stress-strain curve of the Al-Cu-Mg-Ag aluminum matrix composite is shown in the figure. As can be seen from the figure, under the condition of a test speed of 1.5 mm / min, SiC... w The room temperature tensile strength of the Al-Cu-Mg-Ag-0.5Ce aluminum-based composite material reached 983 MPa, which is significantly better than that of SiC. w / Al-Cu-Mg-Ag aluminum-based composite material (672MPa), with an elastic modulus exceeding 130Gpa, far superior to common aluminum alloys (<80Gpa).

[0126] Figure 2 SiC prepared in Example 1 w / Al-Cu-Mg-Ag-0.5Ce aluminum-based composite material, and SiC prepared in Comparative Experiment 1 wHigh-temperature tensile (300℃) stress-strain curves of the Al-Cu-Mg-Ag aluminum matrix composite and the Al-Cu-Mg-Ag aluminum alloy prepared in Comparative Experiment 2 are shown. As can be seen from the figure, under a testing speed of 1.5 mm / min, the high-temperature tensile strength of the composite materials prepared in Example 1 (221 MPa) and Comparative Experiment 1 (231 MPa) is comparable, both showing an increase of approximately 30% compared to the matrix alloy (173 MPa).

[0127] In addition, combined Figure 1 and Figure 2 It can be seen that the SiC prepared in Example 1 w The elongation (0.9% and 12.7%) of the Al-Cu-Mg-Ag-0.5Ce aluminum-based composite material at room temperature and high temperature is significantly better than that of the SiC prepared in Comparative Experiment 1. w / Al-Cu-Mg-Ag aluminum-based composite materials (0.5%, 4.7%).

[0128] Figure 3 SiC prepared in Example 1 w TEM characterization results of the interface phase of the / Al-Cu-Mg-Ag-0.5Ce aluminum-based composite material. Bright-field phase and elemental distribution diagrams show that some whiskers have achieved grain incorporation (blue dashed lines represent grain boundaries, indicating that some whiskers have entered the grains). Furthermore, a 10nm~50nm thick (Ce,O) rich transition layer was observed at the interfaces of SiC whiskers-aluminum matrix and SiC whiskers-grain boundaries.

[0129] Figure 4 SiC prepared in Example 1 w TEM characterization results of intracrystalline precipitates in Al-Cu-Mg-Ag-0.5Ce aluminum-based composite materials. Bright-field phase and elemental distribution diagrams show that while Ce elements segregate on the surface of SiC whiskers, they also segregate on the surface and inside the nano-precipitates within the composite material, covering / embedding a layer of Ce atoms, achieving the expected process effect of multi-interface segregation.

[0130] Figure 5 SiC prepared in Example 1 w The SEM microstructure characterization results of the Al-Cu-Mg-Ag-0.5Ce aluminum-based composite material are shown in the figure. As can be seen from the figure, the micron-sized SiC whiskers are intertwined and linked to form a three-dimensional network structure, which constitutes the heat-resistant skeleton of the aluminum-based composite material.

[0131] Figure 6 SiC prepared in Example 1 wEBSD microstructure characterization results of the Al-Cu-Mg-Ag-0.5Ce aluminum-based composite material. As shown in the figure, the microstructure of this composite material consists of uniform equiaxed crystals with an average grain size of approximately 2.2 μm.

[0132] Figure 7 To compare the SiC prepared in Experiment 3 w TEM characterization results of the interfacial phase of the / Al-Cu-Mg-Ag-0.5Ce aluminum-based composite material. No Ce segregation was observed on the surface of SiC whiskers, indicating that the solid solution process parameters can control the formation and distribution of the (Ce, Cu) rich interfacial layer on the surface of SiC whiskers. This demonstrates that the heat treatment and hot deformation process chain proposed in this embodiment is logically sound and the conditions are interdependent.

Claims

1. A method for synergistically improving the modulus, strength, toughness, and heat resistance of aluminum matrix composites using silicon carbide whisker networks and intracrystalline rare earth-covered precipitates, characterized in that... It is done in the following steps: I. Preparation of silicon carbide whisker preforms: The rinsed silicon carbide whisker solution is stirred and dispersed evenly with water-soluble organic sol to obtain whisker slurry. The whisker slurry is added to a mold with drainage holes at the bottom and left to stand until the water has fully seeped out. Then it is pre-pressed to obtain a pre-formed whisker preform. The pre-formed whisker preform is sintered and shaped and the residual glue is removed to obtain a silicon carbide whisker preform. II. Preparation of alloy melt: The raw materials are weighed according to the mass percentage of each metal element in the alloy matrix material and melted under an argon atmosphere to obtain alloy aluminum liquid. III. Preparation of aluminum-based composite materials by extrusion impregnation: The silicon carbide whisker preform is placed in the middle of the extrusion mold and heated and kept warm in the furnace. Then, some alloy aluminum liquid is poured into the gap between the silicon carbide whisker preform and the extrusion mold. The furnace is reheated and kept warm until the alloy aluminum liquid solidifies to fix the silicon carbide whisker preform. After keeping warm, the heating is stopped. At the same time as the heating is stopped, the remaining alloy aluminum liquid is poured into the gap between the silicon carbide whisker preform and the extrusion mold. Secondary pressurization is carried out during the furnace cooling process. Finally, the furnace is demolded and the surrounding uninfiltrated aluminum alloy is removed to obtain an aluminum-based composite material ingot. IV. Series-type heat treatment-hot extrusion-heat treatment synergistic process: ① The aluminum-based composite material ingot is subjected to a two-stage homogenization process, and then removed and cooled by water quenching to obtain the homogenized composite material. ② The homogenized composite material is subjected to large deformation hot extrusion, and finally water quenching and cooling to obtain extruded bars; ③ The extruded bar is subjected to a short-time high-temperature solution treatment, then removed and water-quenched to obtain the solution-treated bar. ④ The solution-treated rods are subjected to multi-stage aging treatment to obtain an aluminum-based composite material that is synergistically reinforced by silicon carbide whisker network and intracrystalline rare earth covering precipitation.

2. The method for synergistically improving the modulus, strength, toughness, and heat resistance of aluminum matrix composites using silicon carbide whisker networks and intracrystalline rare earth-covered precipitates according to claim 1, characterized in that... The rinsed silicon carbide whisker solution described in step one is prepared according to the following steps: The silicon carbide whiskers are soaked in a mixed acid. First, the mixture is stirred for 2 to 12 hours at room temperature and a stirring speed of 200 to 600 r / min. Then, the mixture is kept at a temperature of 75 to 90°C for 6 to 24 hours. Finally, the mixture is stirred for 1 to 2 hours at room temperature and a stirring speed of 200 to 600 r / min to obtain acid-washed silicon carbide whiskers. Distilled water is added to the acid-washed silicon carbide whiskers and allowed to stand to allow the whiskers to precipitate. Then, the water is removed. The process of adding distilled water, precipitation, and water removal is repeated multiple times until the pH of the removed water is 6 to 7. Finally, the water is drained to obtain the rinsed silicon carbide whisker solution. The silicon carbide whiskers have a diameter of 100 nm to 1.5 µm and a length of 10 µm to 100 µm; the mixed acid is composed of hydrofluoric acid solution, sulfuric acid solution and water, and the volume ratio of hydrofluoric acid solution to sulfuric acid solution is 1:(0.5~1), and the volume ratio of the total volume of hydrofluoric acid solution and sulfuric acid solution to water is 1:(5~9); the mass percentage of the hydrofluoric acid solution is 49%, and the mass percentage of the sulfuric acid solution is 98%.

3. The method for synergistically improving the modulus, strength, toughness, and heat resistance of aluminum matrix composites by utilizing silicon carbide whisker networks and intracrystalline rare earth-covered precipitates according to claim 1, characterized in that... The water-soluble organic sol mentioned in step one is composed of water, silica gel, and polysilazane, and the volume ratio of polysilazane to silica gel is 1:(2~4), and the volume ratio of polysilazane to water is 1:(20~50); the mass percentage of the rinsed silicon carbide whiskers in the rinsed silicon carbide whisker solution mentioned in step one is 25%~35%; in step one, 0.5mL~1.5mL of water-soluble organic sol is weighed out for every 1g of rinsed silicon carbide whisker solution; the pre-compression mentioned in step one is specifically carried out under a pressure of 10MPa~100MPa for 2h~24h.

4. The method for synergistically improving the modulus, strength, toughness, and heat resistance of aluminum matrix composites using silicon carbide whisker networks and intracrystalline rare earth-covered precipitates according to claim 1, characterized in that... The sintering and shaping and removal of residual adhesive described in step one are carried out in the following steps: First, the temperature is maintained at 40℃~60℃ for 12h~36h, then at 80℃~90℃ for 12h~36h, then at 100℃~120℃ for 12h~36h, then the temperature is increased to 700℃~900℃ at a rate not exceeding 2℃ / min, and then maintained at 700℃~900℃ for 1h~4h. After the maintenance, the temperature is cooled to room temperature in the furnace, and then sintered in a vacuum at 1100℃~1300℃ for 1h~4h to obtain silicon carbide whisker preforms with a compressive strength of 7MPa~10MPa.

5. A method for synergistically improving the modulus, strength, toughness, and heat resistance of aluminum matrix composites using silicon carbide whisker networks and intracrystalline rare earth-covered precipitates, as described in claim 1, characterized in that... The alloy matrix material mentioned in step two is an Al-RE alloy, an Al-Cu-Mg-RE alloy, an Al-Ni-Fe-RE alloy, an Al-Cu-Mg-Ag-RE alloy, or an Al-Zn-Mg-Cu-RE alloy, wherein RE is one or a combination of Ce, Sc, Y, and Zr.

6. A method for synergistically improving the modulus, strength, toughness, and heat resistance of aluminum matrix composites using silicon carbide whisker networks and intracrystalline rare earth-covered precipitates, as described in claim 5, characterized in that... When the alloy matrix material mentioned in step two is an Al-Cu-Mg-Ag-RE alloy, the Al-Cu-Mg-Ag-RE alloy is composed of 3.6%~6.0% Cu, 0.4%~2.0% Mg, 0.2%~0.8% Mn, 0.3%~1.0% Ag, 0.1%~2.0% RE, and the balance Al by mass percentage, wherein RE is one or a combination of Ce, Sc, Y, and Zr; the raw materials mentioned in step two are pure Al, Al-Mn alloy, Al-Cu alloy, pure Ag, pure Mg, and Al-RE alloy, wherein Al-RE alloy is one or a combination of Al-Ce alloy, Al-Sc alloy, Al-Y alloy, and Al-Zr alloy; the melting in an argon atmosphere mentioned in step two is specifically carried out according to the following steps: ① melting in an argon atmosphere at a temperature of 760℃~800℃. ① Under ℃ conditions, pure Al, Al-Mn alloy, Al-Cu alloy and pure Ag are heated and melted to obtain a first melt; ② Under argon atmosphere and temperature of 750℃~780℃, an aluminum foil-wrapped degassing agent is pressed into the bottom of the first melt using a bell jar. After the degassing agent and the first melt react completely and no more gas is produced, the slag is removed to obtain the melt after slag removal; the mass ratio of the degassing agent to the first melt is 1:(0.005~0.02), and the degassing agent is hexachloroethane; ③ Under argon atmosphere and temperature of 750℃~780℃, pure Mg and Al-RE alloy wrapped in aluminum foil are pressed into the melt after slag removal using a bell jar, and allowed to stand for 5min~30min to obtain a second melt; ④ Under argon atmosphere, temperature of 760℃~850℃ and stirring speed of 200r / min~800r / min, the second melt is stirred for 5min~15min to obtain alloy aluminum liquid.

7. A method for synergistically improving the modulus, strength, toughness, and heat resistance of aluminum-based composite materials using silicon carbide whisker networks and intracrystalline rare earth-covered precipitates, as described in claim 1, characterized in that... The extrusion die described in step three consists of a die sleeve and a bottom graphite gasket, with ventilation holes provided in the bottom graphite gasket. Specifically, placing the silicon carbide whisker preform in the middle of the extrusion die and heating it in the furnace in step three involves holding it at a temperature of 560℃~620℃ for 0.5h~2h. Reheating and holding the temperature in step three until the aluminum alloy liquid solidifies to fix the silicon carbide whisker preform is carried out as follows: reheating to 560℃~620℃ and holding at that temperature for 30min~60min. The secondary pressurization in step three involves first holding at a low pressure of 5MPa~6MPa for 1min~2min, and then holding at a high pressure of 200MPa~230MPa for 5min~10min.

8. A method for synergistically improving the modulus, strength, toughness, and heat resistance of aluminum-based composite materials using silicon carbide whisker networks and intracrystalline rare earth-covered precipitates, as described in claim 1, characterized in that... The secondary homogenization process described in step 4① is carried out in the following steps: first, keep warm at a temperature of 420℃~490℃ for 48h~96h, and then keep warm at a temperature of 500℃~530℃ for 4h~10h.

9. A method for synergistically improving the modulus, strength, toughness, and heat resistance of aluminum matrix composites using silicon carbide whisker networks and intracrystalline rare earth-covered precipitates, as described in claim 1, characterized in that... The large deformation hot extrusion described in step 4② is carried out according to the following steps: first, the temperature is maintained at 300℃~520℃ for 0.5h~2h, and then hot extrusion deformation is carried out at a temperature of 300℃~520℃ and a metal outflow rate of 0.5m / min~3m / min, with an extrusion ratio of (9~40):1; the short-time high-temperature solution treatment described in step 4③ is carried out according to the following steps: the temperature is maintained at 530℃~600℃ for 10min~60min.

10. A method for synergistically improving the modulus, strength, toughness, and heat resistance of aluminum matrix composites using silicon carbide whisker networks and intracrystalline rare earth-covered precipitates, as described in claim 1, characterized in that... The multi-stage aging treatment described in step 4④ is carried out according to the following steps: First, the temperature is maintained at 150℃~200℃ for 1h~8h, and then water-quenched to room temperature. Next, the temperature is maintained at 200℃~250℃ for 0h~16h, and then water-quenched to room temperature. Finally, the temperature is maintained at 250℃~300℃ for 0h~16h, and then water-quenched to room temperature. The volume percentage of silicon carbide whiskers in the aluminum matrix composite material synergistically reinforced by silicon carbide whisker network and intracrystalline rare earth covered precipitates in step 4④ is 15%~40%.

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