Fine-grained high-strength aluminum matrix composite material and method for producing the same

Abstract

The application discloses a fine-grain high-strength aluminum matrix composite material and a preparation method thereof, and belongs to the technical field of metal matrix composite material preparation. The uniform dispersion of graphene is realized through a wet planetary ball milling technology, and the synergistic effect of fine-grain strengthening and graphene enhancement is realized by combining cold pressing forming and hot rolling densification. The application realizes the uniform dispersion of graphene in the aluminum matrix and the intact structure of graphene by the synergistic effect of the wet planetary ball milling and the cold pressing-hot rolling integrated process, and effectively inhibits the generation of brittle interface reaction products. The proper amount of graphene is used as a recrystallization heterogeneous nucleation core and a grain boundary pinning agent, the aluminum matrix grains are significantly refined, the strength of the material is improved, the plasticity is maintained or even improved, and the bottleneck of the strength-plasticity inversion of traditional aluminum matrix composite materials is completely broken.

Description

Technical Field

[0001] This invention relates to the field of metal matrix composite material preparation technology, and in particular to a fine-grained high-strength aluminum matrix composite material and its preparation method. Background Technology

[0002] Aluminum-based composite materials possess advantages such as low density, high specific strength, excellent thermal and electrical conductivity, and corrosion resistance, making them widely used in lightweight applications such as aerospace, rail transportation, and electronic packaging. However, with the increasing demands for comprehensive material performance in high-end equipment, traditional aluminum-based materials are struggling to meet the stringent requirements of high strength, high plasticity, and complex forming processes. Therefore, introducing high-performance reinforcing phases has become a key approach to overcome existing performance bottlenecks and improve the overall performance of aluminum-based materials.

[0003] Graphene, a novel two-dimensional carbon material, possesses extremely high intrinsic strength (theoretically around 130 GPa), Young's modulus (around 1.0 TPa), and excellent thermal and electrical conductivity, making it a highly promising reinforcing phase in aluminum-based composites. Theoretical studies have shown that graphene can effectively inhibit grain growth in the aluminum matrix and produce a significant strengthening effect by hindering dislocation movement, thereby improving material strength while maintaining good plasticity. However, in actual fabrication processes, the performance of graphene-reinforced aluminum-based composites has fallen far short of theoretical expectations, primarily due to a series of long-standing unresolved technical bottlenecks.

[0004] Graphene sheets possess extremely strong van der Waals forces, and their large specific surface area and high surface activity make them highly susceptible to recombination and agglomeration during mixing with aluminum powder and subsequent densification processes, forming micron-sized aggregates. These aggregates easily cause stress concentration in the composite material under stress, leading to premature fracture. Numerous studies report that graphene-reinforced aluminum matrix composites prepared using conventional processes generally have room temperature elongation below 4%, with some studies even showing elongation below 2%, severely limiting the material's engineering applications, especially in structural components requiring a certain degree of formability.

[0005] Traditional powder metallurgy processes typically employ high-temperature, long-duration sintering or hot pressing to achieve densification. While this process yields high relative density, it inevitably leads to significant coarsening of the aluminum matrix grains, resulting in grain sizes generally exceeding 10 micrometers. This causes the fine-grained strengthening effect to be almost completely lost, thus affecting the material's plasticity. To improve the dispersion uniformity of graphene, researchers often use high-energy dry ball milling to pretreat the mixed powders.

[0006] While high-energy ball milling can break up graphene aggregates to some extent, it also introduces new problems. For example, strong mechanical impacts severely damage the crystal structure of graphene and introduce numerous defects, significantly reducing its intrinsic properties. Simultaneously, the localized temperature rise and intense mechanochemical effects during high-energy ball milling promote interfacial reactions between graphene and the aluminum matrix, generating a brittle Al4C3 phase. The Al4C3 phase not only weakens the interfacial bond between graphene and the aluminum matrix, but its inherent brittleness also makes it a preferential source of crack initiation. Therefore, although the high-energy dry ball milling process may improve strength to some extent, plasticity often decreases significantly, and the inverse relationship between strength and plasticity has not yet been effectively resolved.

[0007] In summary, under the existing technological system, graphene-reinforced aluminum matrix composites have long faced four core challenges: "difficulty in dispersion, coarse grains, poor interface, and inversion of strength and plasticity." Among these, the synergistic improvement of strength and plasticity is particularly critical and remains a technological bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0008] The purpose of this invention is to provide a fine-grained high-strength aluminum-based composite material and its preparation method. Through the synergistic effect of wet planetary ball milling and cold pressing-hot rolling integrated process, graphene is uniformly dispersed in the aluminum matrix with intact structure, effectively suppressing the formation of brittle interface reaction products. By using an appropriate amount of graphene as both a recrystallization heterogeneous nucleation core and a grain boundary pinning agent, the grain size of the aluminum matrix is ​​significantly refined, thereby improving the material strength while maintaining or even improving its plasticity, completely breaking the bottleneck of the traditional aluminum-based composite material's inversion of strength and plasticity. In addition, the process is simple, does not require complex sintering or annealing processes, and is highly compatible with existing powder metallurgy and rolling production lines, thus having good industrial application value.

[0009] To achieve the above objectives, the present invention provides a fine-grained high-strength aluminum-based composite material, which is composed of aluminum powder and monolayer graphene powder, wherein the content of monolayer graphene powder is 0.1-0.75 wt.%, and the balance is aluminum powder.

[0010] Preferably, the aluminum powder has a particle size of 25-30 μm, the monolayer graphene powder has a sheet diameter of 1-5 μm and a thickness of 0.3-2 nm, and the purity of both the aluminum powder and the monolayer graphene powder is ≥99%.

[0011] The preparation method of the fine-grained high-strength aluminum-based composite material described above includes the following steps: S1. Aluminum powder and single-layer graphene powder are put into a planetary ball mill jar, alcohol is added as the ball milling medium, and zirconia balls are added for ball milling. After ball milling, a composite slurry is obtained. S2. The composite slurry obtained in S1 is vacuum dried to remove alcohol, and then sieved to obtain GNPs-Al flake powder. S3. Place the GNPs-Al flake powder obtained in S2 into a mold, apply pressure to form it, and hold the pressure to obtain a composite green body. S4. The composite green blank obtained in S3 is hot rolled to obtain GNPs-Al composite material.

[0012] Preferably, in S1, after adding alcohol, the solid-liquid ratio in the planetary ball mill jar is 1g:5mL, the ball-to-powder mass ratio is (11-15):1, the rotation speed is 400-450r / min, and the ball milling time is 1-2h.

[0013] Preferably, in S2, the vacuum drying temperature is 60-70℃, the vacuum drying time is 15-20h, and the dried product is passed through a 100-mesh sieve.

[0014] Preferably, in step S3, the applied pressure is 25-30 MPa, and the pressure is held for 10-60 seconds.

[0015] Preferably, in S3, the composite green body has a length of 20mm, a width of 10mm, and a height of 4-6mm.

[0016] Preferably, in S4, the hot rolling operation is as follows: the first pass has a reduction of 10-30%, each subsequent pass has a reduction of 20%, the total reduction is ≥80%, the final rolling thickness is 0.8-1mm, and a total of 5-8 passes are performed.

[0017] Preferably, in S4, during the hot rolling process, after each hot rolling pass is completed, the material is returned to the furnace for heat preservation for 30-60 minutes.

[0018] Therefore, the present invention employs the above-mentioned fine-grained high-strength aluminum-based composite material and its preparation method, which has the following beneficial effects: (1) This invention uses an alcohol-medium wet planetary ball milling process combined with an integrated cold pressing-hot rolling preparation route to precisely optimize the amount of graphene added, thereby achieving significant grain refinement of the aluminum matrix. The average grain size of pure aluminum was reduced from 3 μm to 2.1 μm, a refinement of 66.7%, which is far superior to the effect of 0.1 wt.% or 0.75 wt.% graphene addition. This demonstrates that an appropriate amount of graphene can simultaneously serve as a recrystallization heterogeneous nucleation core and grain boundary pinning agent, providing sufficient recrystallization nucleation sites and effectively inhibiting abnormal grain growth during hot rolling. This achieves uniform and stable refinement of the matrix structure, laying a core organizational foundation for the comprehensive improvement of the mechanical properties of composite materials.

[0019] (2) The 0.5wt.% graphene-reinforced aluminum-based composite material prepared by this invention achieves a synergistic leap in strength and plasticity. The tensile strength reaches 280.32±2.97MPa, which is about 49.3% higher than that of pure aluminum. At the same time, the elongation increases from 5.25±0.21% of pure aluminum to 6.11±0.37%, solving the industry problem of the inversion of strength and plasticity in traditional aluminum-based composite materials where strength increases but plasticity inevitably decreases. The composite material with 0.5wt.% addition achieves the highest tensile strength and the best elongation, with significant advantages in comprehensive mechanical properties. It can meet the core performance requirements of high-end fields such as aerospace thin-walled parts, automotive lightweight structural parts, and electronic packaging heat dissipation substrates.

[0020] (3) The wet planetary ball milling process adopted in this invention achieves uniform adsorption and dispersion of graphene on the surface of aluminum powder under mild conditions, effectively avoiding the impact and damage of dry ball milling on the graphene sheet structure. At the same time, it solves the serious agglomeration problem that is prone to occur in high-content graphene. Combined with the low-temperature hot rolling process, it can effectively suppress the formation of brittle Al4C3 phase between graphene and aluminum matrix, ensuring a clean and stable interface bond between matrix and reinforcing phase.

[0021] (4) The present invention has a short process flow, low equipment requirements, and strong controllability of process parameters. It does not require complex vacuum sintering, long recrystallization annealing and other processes. It can be directly adapted to existing powder metallurgy and plastic processing industrial production lines, and has the potential for large-scale mass production and extremely high engineering application value.

[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of a fine-grained high-strength aluminum matrix composite material and its preparation method according to the present invention; Figure 2 This is a distribution diagram of monolayer graphene powder in the aluminum-based composite material of Example 1 of the present invention, which is a fine-grained high-strength aluminum-based composite material and its preparation method. Detailed Implementation

[0024] This invention provides a fine-grained high-strength aluminum-based composite material, which is composed of aluminum powder and monolayer graphene powder, wherein the content of monolayer graphene powder is 0.1-0.75 wt.%, and the balance is aluminum powder.

[0025] In this invention, the aluminum powder has a particle size of 25-30 μm, the monolayer graphene powder has a sheet diameter of 1-5 μm and a thickness of 0.3-2 nm, and the purity of both the aluminum powder and the monolayer graphene powder is ≥99%.

[0026] Aluminum powder, as the matrix material for composite materials, provides essential metallic properties such as lightweight, high specific strength, excellent thermal and electrical conductivity, and corrosion resistance. Its purity is ≥99% and its particle size is 25-30 μm, ensuring the purity and good formability of the matrix. In subsequent processes, aluminum powder fills the gaps between graphene sheets through plastic flow, forming a continuous and dense metallic matrix. Simultaneously, as the main phase bearing external forces, it transfers the load to the graphene reinforcing phase through the interface.

[0027] Single-layer graphene powder, as a reinforcing phase, utilizes its ultra-high intrinsic strength (theoretical 130 GPa) and Young's modulus (approximately 1.0 TPa) to bear load transfer and hinder dislocation movement in composite materials, thereby significantly improving strength. Simultaneously, the uniformly dispersed graphene sheets provide numerous heterogeneous nucleation sites during the recrystallization of the aluminum matrix and pin grain boundaries, inhibiting grain growth and achieving grain refinement (average grain size can be as fine as 2.1 μm). The designed parameters of sheet diameter (1-5 μm), thickness (0.3-2 nm), and purity (≥99%) ensure good dispersibility and reinforcement efficiency.

[0028] like Figure 1 As shown, the preparation method of the fine-grained high-strength aluminum-based composite material described above includes the following steps: S1. Aluminum powder and single-layer graphene powder are put into a planetary ball mill jar, alcohol is added as the ball milling medium, and zirconia balls are added for ball milling. After ball milling, a composite slurry is obtained. In S1, after adding alcohol, the solid-liquid ratio in the planetary ball mill jar is 1g:5mL, the ball-powder mass ratio is (11-15):1, the rotation speed is 400-450r / min, and the ball milling time is 1-2h.

[0029] In S1, alcohol was used as the ball milling medium, and ball milling was performed at 400-450 r / min for 1-2 hours to uniformly mix aluminum powder and monolayer graphene powder in the liquid phase. The alcohol medium effectively reduced the van der Waals forces between graphene sheets, avoiding graphene agglomeration and structural damage common in dry ball milling. At the same time, the gentle mechanical energy promoted the uniform adsorption of graphene on the surface of aluminum powder, forming a composite structure of graphene encapsulating aluminum powder, providing a precursor without agglomeration or harmful interfacial reactions for subsequent densification.

[0030] S2. The composite slurry obtained in S1 is vacuum dried to remove alcohol, and after drying, it is sieved to obtain GNPs-Al flake powder; in S2, the vacuum drying temperature is 60-70℃, the vacuum drying time is 15-20h, and after drying, it is sieved through a 100-mesh sieve.

[0031] S2 is vacuum dried at 60-70℃ for 15-20 hours to completely remove the alcohol solvent and prevent residual media from causing porosity or oxidation during subsequent hot rolling. After drying, it is passed through a 100-mesh sieve to further disperse any possible soft agglomerates, obtaining GNPs-Al flake powder with good flowability and uniform composition, ensuring the density uniformity and mechanical consistency of the green body during cold pressing.

[0032] S3. Place the GNPs-Al flake powder obtained in S2 into a mold, apply pressure to form it, and hold the pressure to obtain a composite green body. In S3, the applied pressure is 25-30 MPa, and the holding pressure is 10-60 s. The composite green body has a length of 20 mm, a width of 10 mm, and a height of 4-6 mm.

[0033] In S3, cold pressing avoids grain coarsening caused by high-temperature sintering, while forming mechanical interlocking and preliminary cold welding between powder particles, giving the green blank sufficient strength to withstand subsequent hot rolling operations, and providing a geometrically regular preform for hot rolling densification.

[0034] S4. The composite green billet obtained in S3 is hot rolled to obtain GNPs-Al composite material. In S4, the hot rolling operation is as follows: the first pass reduction is 10~30%, the subsequent passes have a reduction of 20%, the total reduction is ≥80%, the final rolling thickness is 0.8-1mm, and a total of 5-8 passes are performed. During the hot rolling process, after each pass is completed, the material is returned to the furnace for heat preservation for 30-60 minutes.

[0035] In S4, hot rolling causes dynamic recrystallization of the aluminum matrix through large plastic deformation, further refining the grains. At the same time, the rolling pressure promotes the closure of the interfaces between aluminum powder particles, achieving full densification of the composite material, and promotes the directional arrangement of graphene sheets along the rolling direction, optimizing load transfer efficiency. Furthermore, the heat preservation in the furnace ensures uniform deformation temperature and avoids cracks caused by work hardening.

[0036] The ratio of aluminum powder to monolayer graphene powder (0.1-0.75 wt.% graphene, preferably 0.5 wt.%) forms the first layer of synergy with the wet planetary ball milling process: an appropriate amount of graphene uniformly coats the aluminum powder in the alcohol medium, which not only avoids the damage to graphene caused by dry ball milling, but also provides sufficient nucleation cores for subsequent fine grain strengthening.

[0037] A second synergy is achieved between cold pressing and hot rolling processes: cold pressing yields high-density green blanks, avoiding grain coarsening caused by high-temperature pre-sintering; hot rolling, through dynamic recrystallization and grain boundary pinning (from uniformly dispersed graphene), controls the average grain size to 2-4 μm, while simultaneously achieving a tensile strength of up to 280 MPa and an elongation exceeding 6%, breaking through the bottleneck of increasing strength but decreasing plasticity in traditional aluminum-based composites. Furthermore, the synergistic effect of graphene addition (0.5 wt.%) and hot rolling temperature (550℃) suppresses the formation of harmful brittle Al4C3 phases, ensuring clean interfacial bonding, thus achieving a synergistic effect of fine-grain strengthening and graphene reinforcement.

[0038] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims and are all within the protection scope of the present invention.

[0039] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0040] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0041] In this invention, unless otherwise specified, all other test materials and instruments are conventional test materials in the field and can be purchased through commercial channels.

[0042] Example 1 This invention provides a fine-grained, high-strength aluminum-based composite material. The composite material is composed of aluminum powder and monolayer graphene powder, wherein the content of monolayer graphene powder is 0.5 wt.% and the aluminum powder is 99.5 wt.%. The distribution diagram of the monolayer graphene powder in the aluminum-based composite material is shown below. Figure 2 As shown, the red area represents the distribution region of single-layer graphene powder, which is composed of... Figure 2 It can be seen that the graphene sheets achieved a uniform and non-agglomerated dispersion in the aluminum matrix.

[0043] The aluminum powder has a particle size of 25-30μm, the monolayer graphene powder has a sheet diameter of 1-5μm and a thickness of 0.3-2nm, and the purity of both the aluminum powder and the monolayer graphene powder is ≥99%.

[0044] The above-mentioned method for preparing a fine-grained high-strength aluminum-based composite material includes the following steps: S1. Aluminum powder and single-layer graphene powder are put into a planetary ball mill jar, alcohol is added as the ball milling medium, the solid-liquid ratio is 1g:5mL, 2.5mm zirconia balls are added, the ball-to-powder ratio is 12:1, the rotation speed is 420r / min, the ball milling time is 1.5h, and a composite slurry is obtained after ball milling.

[0045] S2. The composite slurry obtained in S1 is dried in a vacuum drying oven at 65℃ for 18 hours to completely remove the alcohol. The dried powder is then passed through a 100-mesh sieve to obtain 0.5wt.% GNPs-Al flake powder.

[0046] S3. The GNPs-Al flake powder obtained in S2 is loaded into a steel mold and molded under a pressure of 26MPa for 30s to obtain a composite green body with a length of 20mm, a width of 10mm and a height of about 5mm.

[0047] S4. The composite green billet obtained in S3 is subjected to multi-pass hot rolling at 550±10℃: the first pass has a reduction of 15%, and each subsequent pass has a reduction of 20%, with a total reduction of not less than 80%, for a total of 6 passes, with a final rolled thickness of approximately 0.8 mm. During the rolling process, each pass is reheated in the furnace for 45 min to obtain 0.5 wt.% GNPs-Al composite material.

[0048] Example 2 The only difference between this embodiment and Example 1 is that the content of single-layer graphene powder is 0.75 wt.% and the content of aluminum powder is 99.25 wt.%, while all other conditions are the same.

[0049] Example 3 The only difference between this embodiment and Example 1 is that the content of single-layer graphene powder is 0.1 wt.% and the content of aluminum powder is 99.9 wt.%, while all other conditions are the same.

[0050] Comparative Example 1 The only difference between this comparative example and Example 1 is that no single-layer graphene powder was added in this comparative example, and the material prepared was composed of 100 wt.% aluminum powder. All other conditions were the same.

[0051] The materials prepared in Examples 1-3 and Comparative Example 1 were subjected to performance tests, and the test results are shown in Table 1.

[0052] Table 1 Process parameters and performance test results

[0053] As can be seen from Examples 1-3, as the graphene content increases from 0.1 wt.% to 0.75 wt.%, the average grain size of the composite material first decreases and then increases, while the tensile strength and elongation also show a regular change of first increasing and then decreasing. Example 1 has the finest average grain size (2.1 μm), the highest tensile strength (280.32 ± 2.97 MPa), and the optimal elongation (6.11 ± 0.37%), exhibiting the best overall performance. Example 2 has an average grain size of 2.8 μm, a tensile strength of 256 ± 14.2 MPa, and an elongation of 4.82 ± 1.25%. Example 3 has an average grain size of 3.4 μm, a tensile strength of 231 ± 4.23 MPa, and an elongation of 3.26 ± 0.76%. These results indicate that a graphene content of 0.5 wt.% provides the best grain refinement effect and the optimal overall performance in terms of strength and plasticity. Both excessively high (0.75 wt.%) and excessively low (0.1 wt.%) graphene content can lead to grain coarsening and a significant reduction in mechanical properties.

[0054] A comparison of Examples 1 with Examples 2 and 3 shows that when the graphene content is 0.5 wt.%, the average grain size is only 2.1 μm, while at 0.75 wt.%, the grain size increases to 2.8 μm, and at 0.1 wt.%, it reaches 3.4 μm. This indicates that there is an optimal value for the graphene content. At this content, the graphene is uniformly dispersed, providing sufficient heterogeneous nucleation sites to refine the grains, and inhibiting grain growth through grain boundary pinning. However, if the graphene content is too high, agglomeration is likely to occur, thus losing the grain refinement effect and leading to grain coarsening and performance degradation. If the content is too low, there are insufficient nucleation sites, making it impossible to achieve sufficient grain refinement, resulting in limited improvement in mechanical properties. Therefore, an appropriate amount of graphene addition is key to achieving a balance between grain refinement and strength / plasticity.

[0055] A comparison of Example 1 and Comparative Example 1 shows that the average grain size of pure aluminum without graphene is 3 μm, the tensile strength is 201.2 ± 2.53 MPa, and the elongation is 5.25 ± 0.21%. Compared with Example 1, the grains of pure aluminum are coarser and the strength is significantly insufficient, indicating that the addition of an appropriate amount of graphene can significantly refine the grains, greatly improve the strength, and maintain excellent plasticity.

[0056] Compared to pure aluminum (201.2 MPa), the tensile strength of the 0.5 wt.% graphene / aluminum composite reached 280.3 MPa, an improvement of approximately 49.3%. This improvement stems from the combined effect of two factors: firstly, the 2.1 μm fine-grained structure contributes to grain refinement through the Hall-Petch relationship; secondly, the uniformly dispersed and structurally complete graphene efficiently bears load transfer and hinders dislocation movement. These two mechanisms mutually enhance each other at the 0.5 wt.% ratio, while neither simple grain refinement (pure aluminum) nor simple graphene reinforcement (but agglomeration) can achieve this strength level.

[0057] Furthermore, it is traditionally believed that the addition of a hard reinforcing phase usually leads to a decrease in plasticity. However, in Example 1, the elongation of the 0.5 wt.% graphene / aluminum composite (6.11%) was actually higher than that of pure aluminum (5.25%). This is because wet ball milling ensures uniform dispersion of graphene, preventing agglomerates from acting as stress concentration sources and causing early fracture. Simultaneously, the fine-grained structure (2.1 μm) provides more intragranular dislocation storage space, delaying necking instability, while the clean interface between graphene and the aluminum matrix (inhibiting Al4C3 formation) ensures efficient load transfer during deformation. These three factors work synergistically to simultaneously improve both strength and plasticity.

[0058] The comparison shows that Example 1, through an integrated process of wet planetary ball milling combined with hot rolling and air cooling, and by optimizing the graphene content to 0.5 wt.%, successfully prepared an aluminum-based composite material with an average grain size of 2.1 μm, a tensile strength of over 280 MPa, and an elongation of over 6%. This achieved a synergistic effect of fine grain reinforcement and graphene enhancement, and its overall performance was significantly better than that of Examples 2-3 and Comparative Example 1.

[0059] Cold pressing at 25-30 MPa yields a composite green body with sufficient strength, avoiding grain coarsening caused by high-temperature sintering. Subsequently, multi-pass hot rolling at 550±10℃ (total reduction ≥80%) further refines the grains through dynamic recrystallization. Simultaneously, holding the material in the furnace after each pass (30-60 min) maintains the temperature, allowing the material to directly achieve high density and fine-grained structure without a separate annealing process. This integrated cold pressing and hot rolling approach eliminates the need for long-term high-temperature sintering in traditional powder metallurgy, and, in conjunction with the pinning effect of graphene, jointly suppresses grain growth to the 2-4 μm range.

[0060] Therefore, this invention employs the aforementioned fine-grained high-strength aluminum matrix composite material and its preparation method. Through the synergistic effect of wet planetary ball milling and cold pressing-hot rolling integrated process, graphene is uniformly dispersed in the aluminum matrix with intact structure, effectively suppressing the formation of brittle interface reaction products. By using an appropriate amount of graphene as both a recrystallization heterogeneous nucleation core and a grain boundary pinning agent, the aluminum matrix grains are significantly refined, thereby maintaining or even improving plasticity while enhancing material strength, completely breaking the bottleneck of the traditional aluminum matrix composite material's inversion of strength and plasticity. In addition, the process is simple, requires no complex sintering or annealing steps, and is highly compatible with existing powder metallurgy and rolling production lines, possessing good industrial promotion value.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a fine-grained, high-strength aluminum-based composite material, characterized in that: The aluminum-based composite material is composed of aluminum powder and monolayer graphene powder, wherein the content of monolayer graphene powder is 0.1-0.75 wt.%, and the balance is aluminum powder. The preparation method includes the following steps: S1. Aluminum powder and single-layer graphene powder are put into a planetary ball mill jar, alcohol is added as the ball milling medium, and zirconia balls are added for ball milling. After ball milling, a composite slurry is obtained. In S1, after adding alcohol, the solid-liquid ratio in the planetary ball mill jar is 1g:5mL, the ball-to-powder mass ratio is (11-15):1, the rotation speed is 400-450r / min, and the milling time is 1-2h. S2. The composite slurry obtained in S1 is vacuum dried to remove alcohol, and then sieved to obtain GNPs-Al flake powder. S3. Place the GNPs-Al flake powder obtained in S2 into a mold, apply pressure to form it, and hold the pressure to obtain a composite green body. S4. The composite green billet obtained in S3 is hot rolled to obtain GNPs-Al composite material; In S4, the hot rolling operation is as follows: the first pass has a reduction of 10~30%, each subsequent pass has a reduction of 20%, the total reduction is ≥80%, the final rolling thickness is 0.8-1mm, and a total of 5-8 passes are performed. In S4, during the hot rolling process, after each hot rolling pass is completed, the material is returned to the furnace for heat preservation for 30-60 minutes.

2. The method for preparing a fine-grained high-strength aluminum-based composite material according to claim 1, characterized in that: In S2, the vacuum drying temperature is 60-70℃, the vacuum drying time is 15-20h, and the dried product is passed through a 100-mesh sieve.

3. The method for preparing a fine-grained high-strength aluminum-based composite material according to claim 1, characterized in that: In S3, the applied pressure is 25-30 MPa, and the pressure is held for 10-60 seconds.

4. The method for preparing a fine-grained high-strength aluminum-based composite material according to claim 1, characterized in that: In S3, the composite green body has a length of 20mm, a width of 10mm, and a height of 4-6mm.

5. A fine-grained, high-strength aluminum-based composite material, characterized in that: The high-strength aluminum-based composite material with a fine-grained structure is prepared by any one of claims 1-4. The aluminum-based composite material is composed of aluminum powder and monolayer graphene powder, wherein the content of monolayer graphene powder is 0.1-0.75 wt.%, and the balance is aluminum powder.

6. The fine-grained high-strength aluminum-based composite material according to claim 5, characterized in that: The aluminum powder has a particle size of 25-30μm, the monolayer graphene powder has a sheet diameter of 1-5μm and a thickness of 0.3-2nm, and the purity of both aluminum powder and monolayer graphene powder is ≥99%.

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