Aluminum matrix composite based on micro-nano composite structure and preparation method thereof

Abstract

The application discloses an aluminum matrix composite based on a micro-nano composite structure and a preparation method thereof. The aluminum matrix composite comprises a microcrystalline aluminum alloy matrix and at least one reinforcing unit. The reinforcing unit is uniformly dispersed in the microcrystalline aluminum alloy matrix, and the long axis direction is arranged along a preset direction. The reinforcing unit comprises non-nano SiC particles and a nanocrystalline aluminum alloy coating layer. The nanocrystalline aluminum alloy coating layer coats the non-nano SiC particles to form a core-shell structure. The non-nano SiC particles are micro SiC particles, and the particle size of the micro SiC particles ranges from 1 to 100 microns. The application breaks through the constraint relationship between the strength and plasticity of the existing aluminum matrix composite, and significantly improves the strength and plasticity of the material.

Description

Technical Field

[0001] The present invention relates to the technical field of metal composite materials, in particular to an aluminum-based composite material based on a micro-nano composite structure and a preparation method thereof. Background Art

[0002] 7000 series aluminum alloys are precipitation-strengthened aluminum alloys, also known as heat-treatable aluminum alloys. Their strength before heat treatment is only 300 MPa, but after solution and aging treatments, the strength can be increased to 550-700 MPa. The addition of micron or nano-ceramic particles can improve the hardness, strength, and stiffness of aluminum alloys, but at the expense of plasticity. For example, 7000 series aluminum-based composites with a tensile strength exceeding 700 MPa typically have an elongation of no more than 2%. This strength-plasticity mismatch has long been a key technical bottleneck in aluminum-based composites.

[0003] In recent years, researchers have discovered that the damage tolerance of composite materials can be improved by designing reinforcements with an ordered, rather than uniform, distribution. Typical structures include multi-core, layered, mesh, and gradient structures. These structures are characterized by being nearly uniform at the macroscale but non-uniform at the microscale, meaning that the content of the reinforcement particles in each microscopic region exhibits periodic or gradient variations. These unique structural designs can effectively improve the fracture toughness and impact resistance of the material to a certain extent, making the development of aluminum-based composites extremely attractive.

[0004] However, existing technologies often use nano-reinforcements to achieve heterogeneous structural designs. These include ceramic particles such as nano-TiC, nano-TiB2, and nano-SiC, as well as flexible reinforcements such as carbon nanotubes (CNTs) and graphene. However, nano-reinforcements have high surface energy and are difficult to disperse. Agglomerated nano-reinforcements can degrade material strength and plasticity, so most nano-reinforcements are added at a volume fraction of less than 5%.

[0005] Micronized ceramic particles offer the advantages of low cost and ease of dispersion, allowing them to be added at a volume fraction of 10-45% to achieve aluminum-based composites with higher elastic modulus and hardness. However, unlike nanoparticles, micronized ceramic particles have a larger surface area, leading to more severe mismatch stress concentration at the interface with the aluminum matrix. Under external loads, dislocation pile-up occurs at the micronized SiC / Al interface. Once the mismatch stress exceeds the yield strength of the aluminum matrix, cracks will preferentially initiate and propagate until the material fails.

[0006] Unfortunately, existing technologies lack effective solutions for improving dislocation tolerance and regulating stress near the micron-SiC / Al interface. Stress concentration in areas with high micron-particle content is more pronounced, and crack initiation and propagation cannot be effectively suppressed, resulting in poor material strength and ductility. To overcome the constraints of existing micron-particle-reinforced aluminum-based composites on strength and ductility, this application provides the following solutions. Summary of the Invention

[0007] The present application provides an aluminum-based composite material based on a micro-nano composite structure and a preparation method thereof, which is used to break through the restrictive relationship between strength and plasticity of existing aluminum-based composite materials and significantly improve the strength and plasticity of the material.

[0008] On the one hand, the present application discloses an aluminum-based composite material based on a micro-nano composite structure, comprising a micron-crystalline aluminum alloy matrix and at least one strengthening unit; the strengthening unit is uniformly dispersed in the micron-crystalline aluminum alloy matrix, and the long axis direction is directionally arranged along a preset direction; the strengthening unit comprises non-nanoscale SiC particles and a nanocrystalline aluminum alloy wrapping layer, the nanocrystalline aluminum alloy wrapping layer covers the non-nanoscale SiC particles to form a core-shell structure; the non-nanoscale SiC particles are micron-sized SiC particles, and the particle size of the micron-sized SiC particles ranges from 1 to 100 μm; the average grain size of the nanocrystalline aluminum alloy wrapping layer is 200 to 500 nm, and the volume ratio of the micron-sized aluminum alloy matrix to the nanocrystalline aluminum alloy wrapping layer is 1:1; the number of the non-nanoscale SiC particles in a single strengthening unit is 1 to 20.

[0009] By adopting the above technical solution, the present application introduces a nanocrystalline transition layer on the surface of micron-sized reinforcing particles to form a new strengthening unit. The new strengthening unit and the micron-sized crystal matrix are arranged uniformly and directionally to obtain a composite structure aluminum-based composite material with a gradient arrangement of micron-sized crystals / nanocrystals / micron-sized particles.

[0010] Among them, the strengthening unit in this application includes non-nanoscale SiC particles and a nanocrystalline aluminum alloy coating, and the nanocrystalline aluminum alloy coating covers the non-nanoscale SiC particles to form a core-shell structure. Specifically, the non-nanoscale SiC particles in this application are micron SiC particles. The aluminum-based composite material in this application does not contain nanoscale SiC particles, but solves the problem of interface stress concentration in the aluminum-based composite material. Specifically, a gradient interface is formed between the nanocrystalline aluminum alloy coating and the micron-crystalline aluminum alloy matrix to alleviate interface stress concentration and inhibit crack initiation, so that the composite material has excellent plastic deformation ability.

[0011] Preferably, the average grain size of the micron-crystalline aluminum alloy matrix is ​​2-30 μm; nanometer-scale η' phase precipitates are uniformly distributed inside the grains of the micron-crystalline aluminum alloy matrix and the nanocrystalline aluminum alloy wrapping layer; and the η' phase precipitates are MgZn2.

[0012] By adopting the above technical solution, nano-scale η' phase (MgZn2) precipitates are evenly distributed inside the grains of the micron-crystalline aluminum alloy matrix and the nano-crystalline aluminum alloy wrapping layer. When the η' phase precipitates evenly within the grain, the formation of continuous network η phase at the grain boundary can be reduced, thereby reducing the grain boundary from becoming the preferred crack propagation path and improving the fracture toughness of the alloy.

[0013] On the other hand, the present application discloses a method for preparing the aluminum-based composite material based on the micro-nano composite structure, which includes the following operating steps: first mechanical mixing, nano-high-energy ball milling, second mechanical mixing, ingot preparation, thermal deformation and T6 heat treatment.

[0014] Preferably, the first mechanical mixing includes the following operating steps: weighing SiC particles and aluminum alloy powder according to a ratio of mass fraction of 10%-15%:90%-85%; and dividing the aluminum alloy powder into a first aluminum alloy powder and a second aluminum alloy powder in equal parts by mass; taking the weighed SiC particles and the first aluminum alloy powder and mixing them evenly using a mechanical mixer; the mechanical mixer is a V-type mixer, the ball-to-material ratio is 1:1, the mixer speed is 30~50rpm, and the mixing time is 6~8h, to obtain a mixture of the SiC particles and the first aluminum alloy powder.

[0015] Preferably, the chemical composition of the aluminum alloy powder is as follows by mass percentage: Zn: 6.0-7.0%, Mg: 2.0-3.0%, Cu: 1.0-2.0%, and the rest is Al and unavoidable impurity elements. The average particle size of the aluminum alloy powder is 10-15 microns.

[0016] Preferably, the nano-high-energy ball milling includes the following operating steps: adding 2% by mass of stearic acid to the mixture of the SiC particles and the first aluminum alloy powder, and using a stirred ball mill under argon protection to nano-crystalize the first aluminum alloy powder to form a reinforcement unit in which micron SiC particles are wrapped by nanocrystalline aluminum alloy, the ball-to-material ratio is 10:1, the ball milling speed is 300~400rpm, and the ball milling time is 3~6h.

[0017] Preferably, the second mechanical mixing includes the following steps: adding the second aluminum alloy powder to the strengthened unit after high-energy ball milling, and mixing it by using a mechanical mixer, wherein the mechanical mixer is a V-shaped mixer, the ball-to-powder ratio is 1:1, the mixer speed is 30-50 rpm, and the mixing time is 6-8 h, to obtain a uniform composite powder.

[0018] Preferably, the billet preparation includes the following steps: loading the composite powder into a mold, and sintering and forming in a vacuum hot-pressing furnace to obtain an aluminum-based composite material billet; the sintering temperature is 500-560℃, the holding time is 2-3 h, and the applied pressure is 30-50 Mpa.

[0019] Preferably, the hot deformation includes the following steps: deforming the aluminum-based composite material billet into an aluminum-based composite material with a shaped structure by hot extrusion, wherein the preheating temperature of the billet before hot extrusion is 420℃, the holding time is 1 h, and the extrusion ratio is 20:1.

[0020] Preferably, the T6 heat treatment includes the following steps: placing the aluminum-based composite material with a shaped structure in a muffle furnace for holding, then placing it in water for cooling, then placing the material in a drying oven for holding, and finally cooling it to room temperature in air, to obtain an aluminum-based composite material based on a micro-nano composite structure.

[0021] The one or more technical solutions provided in the application have at least the following technical effects or advantages:

[0022] In the application, a nano-crystal transition layer is introduced on the surface of the micron-level reinforcing particles to form a new strengthened unit, while the remaining aluminum alloy matrix maintains a micron-level grain structure, and then the new strengthened unit and the micron crystal matrix are uniformly and directionally arranged through hot extrusion deformation, so that an aluminum-based composite material with a micron crystal / nano crystal / micron particle composite structure is finally obtained.

[0023] The principle is to use the grain boundary strengthening effect to avoid crack initiation and accumulation of the SiC / Al near-interface matrix, thereby improving the yield strength and tensile strength of the material, and the micron-level grains provide sufficient space for the proliferation and sliding of dislocations, so that the composite material has excellent plastic deformation ability. Through the above micro-nano composite structure design, the strength and plasticity of the existing aluminum-based composite material can be broken through, the strength and plasticity of the material can be significantly improved, and the application prospect and economic benefit of the material are significant. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0025] Figure 1 Morphology diagram of uniform mixing of micron SiC particles and first aluminum alloy powder in Example 1 of the present application;

[0026] Figure 2 Morphology diagram of micron SiC particles coated with nanocrystals in Example 1 of the present application;

[0027] Figure 3 Schematic diagram of a strengthening unit of micron SiC particles coated with nanocrystals in Example 1 of the present application;

[0028] Figure 4 Metallographic structure diagram of micro-nano composite structure aluminum matrix composite material after extrusion deformation in Example 1 of the present application;

[0029] Figure 5 Multi-scale grain structure diagram in the micro-nano composite structure aluminum matrix composite material in Example 1 of the present application;

[0030] Figure 6 Tensile curve diagram of micro-nano composite structure aluminum matrix composite material after heat treatment in Example 1 of the present application;

[0031] Figure 7 Gradient interface diagram in the micro-nano composite structure aluminum matrix composite material in Example 1 of the present application;

[0032] Figure 8 Precipitated phase inside the nanocrystalline grain in Example 1 of the present application;

[0033] Figure 9 Precipitated phase inside the micron grain in Example 1 of the present application;

[0034] Figure 10 Metallographic structure diagram of aluminum matrix composite material in Example 2;

[0035] Figure 11 Metallographic structure diagram of aluminum matrix composite material in Comparative Example 1;

[0036] Figure 12 Metallographic structure diagram of aluminum matrix composite material in Comparative Example 2;

[0037] Figure 13 Metallographic structure diagram of aluminum matrix composite material in Comparative Example 3;

[0038] Figure 14This is the metallographic structure diagram of the aluminum-based composite material in Comparative Example 4. DETAILED DESCRIPTION

[0039] The present application provides an aluminum-based composite material based on a micro-nano composite structure and a preparation method thereof, which is used to break through the restrictive relationship between strength and plasticity of existing aluminum-based composite materials and significantly improve the strength and plasticity of the material.

[0040] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only some of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection of this application.

[0041] It should be noted that the terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or server that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or modules that are not clearly listed or inherent to these processes, methods, products, or devices.

[0042] raw material

[0043] SiC particles: This application uses commercially available silicon carbide particles, CAS number: 409-21-2, molecular weight: 40.096, density: 3.10-3.28 (g / cm3), content: 99.0%, particle size: 1~100 μm.

[0044] Aluminum alloy powder: This application uses commercially available aluminum alloy powder, which is prepared by atomization method, CAS number: 53947-37-8, content ≥99.9%, and particle sizes of 13 microns, 100 microns and 200 microns respectively.

[0045] Stearic acid: This application uses commercially available stearic acid, CAS No.: 85541-42-0, molecular weight: 285.470, purity: 95%.

[0046] Example Example 1

[0047] Micro-nano composite structure aluminum-based composite materials:

[0048] S1. First mechanical mixing: Weigh the SiC particles and aluminum alloy powder separately. Take 10 kg of SiC particles and 90 kg of aluminum alloy powder, and divide the aluminum alloy powder into 45 kg of first aluminum alloy powder and 45 kg of second aluminum alloy powder. Use a mechanical mixer to mix 10 kg of SiC particles and 45 kg of first aluminum alloy powder evenly. The morphology of the mixed powder is shown in FIG. Figure 1 The mechanical mixer used is a V-type mixer, the ball-to-material ratio is 1:1, the mixer speed is 36rpm, and the mixing time is 8h.

[0049] S2. Nano-energy ball milling: Stearic acid with a mass fraction of 2% is added to the mixture of SiC particles and the first aluminum alloy powder as a process control agent. The first aluminum alloy powder is then nano-milled in an agitated ball mill under argon protection to form a reinforcement unit with nano-grains (nano-aluminum alloy powder) encapsulating micro-grains (micro-SiC particles). The specific morphology is shown in Figure 2 , the schematic diagram of the strengthening unit is shown in Figure 3 , the ball-to-material ratio is 10:1, the ball milling speed is 300 rpm, and the ball milling time is 5 h.

[0050] S3. Second mechanical mixing: add 45 kg of the second aluminum alloy powder to the strengthening unit after nano-high energy ball milling, and use a V-type mechanical mixer again with a mixer speed of 36 rpm and a mixing time of 8 hours to obtain a uniform composite powder.

[0051] S4. Billet preparation: The uniformly mixed composite powder is loaded into a mold and sintered in a vacuum hot pressing furnace to obtain an aluminum-based composite material billet. The sintering temperature is 520°C, the holding time is 2h, and the applied pressure is 35 MPa to obtain an aluminum-based composite material.

[0052] S5. Hot deformation: The aluminum-based composite material ingot is processed into an aluminum-based composite material with a formed structure by hot extrusion deformation. The embodiment of the present application is a rod processed into an aluminum-based composite material. The preheating temperature of the ingot before hot extrusion is 420°C, the holding time is 1h, the extrusion ratio is 20:1, and a long strip reinforcement unit is obtained. The microstructure has directionality and the metallographic structure is shown in FIG. Figure 4 , micron / nano multi-scale grain structure see Figure 5 .

[0053] S6 and T6 heat treatment: the rod was placed in a muffle furnace at 470°C for 2 hours, then placed in water for cooling, the transfer time was less than 10 seconds, and then placed in a drying oven at 120°C for 24 hours, and finally cooled to room temperature in air to obtain a micro-nano composite structure aluminum-based composite material. The micro-nano composite structure aluminum-based composite material was tested, and the tensile strength reached 721Mpa, the yield strength was 615Mpa, the elongation was 3.5%, and the tensile curve was shown in FIG. Figure 6 .

[0054] The aluminum-based composite material obtained by the process of the present application includes a micron-crystalline aluminum alloy matrix and a plurality of strengthening units.

[0055] Specific, combined Figure 4 The average grain size of the micron-crystalline aluminum alloy matrix is ​​2-30 μm; the strengthening units are uniformly dispersed in the micron-crystalline aluminum alloy matrix, and the long axis direction is directionally arranged along a preset direction.

[0056] The strengthening unit is composed of micron-sized SiC particles and a nanocrystalline aluminum alloy wrapping layer. The nanocrystalline aluminum alloy wrapping layer covers the micron-sized SiC particles to form a core-shell structure. At the same time, the number of micron-sized SiC particles in a single strengthening unit is 1 to 20.

[0057] Reference Figure 7 From a broader perspective, the present application introduces a nanocrystalline transition layer on the surface of micron-sized reinforcing particles to form a new strengthening unit. The new strengthening unit and the micron-crystalline matrix are evenly and directionally arranged to obtain a composite aluminum-based composite material with a gradient arrangement of micron-crystalline / nanocrystalline / micron-sized particles. A gradient interface is formed between the nanocrystalline aluminum alloy wrapping layer and the micron-crystalline aluminum alloy matrix to alleviate interfacial stress concentration and inhibit crack initiation, so that the composite material has excellent plastic deformation ability. Specifically, the average grain size of the nanocrystalline aluminum alloy wrapping layer is 200-500nm, and the volume ratio of the micron-crystalline aluminum alloy matrix to the nanocrystalline aluminum alloy wrapping layer is 1:1.

[0058] In addition, refer to Figure 8 and Figure 9 Nanoscale η' phase (MgZn2) precipitates are uniformly distributed within the grains of the microcrystalline aluminum alloy matrix and the nanocrystalline aluminum alloy coating. The uniform precipitation of η' phase within the grains reduces the formation of continuous η phase networks at grain boundaries, thus reducing the grain boundaries from becoming the preferred crack propagation path and improving the alloy's fracture toughness.

[0059] Example 2

[0060] The difference between Example 2 and Example 1 is the degree of nano-crystallization of the aluminum alloy grains. In Example 2, the nano-crystallization ball milling time is 3 h, and the other preparation parameters are the same as those of Example 1. The metallographic structure is shown in FIG. Figure 10 After T6 heat treatment, the material has a tensile strength of 692 MPa, a yield strength of 585 MPa, and an elongation of 3.8%.

[0061] Comparative Example

[0062] Comparative Example 1

[0063] The difference between Comparative Example 1 and Example 1 is that, when the SiC particles and the aluminum alloy powder are weighed, the mass fraction of the SiC particles is 15%; and in Comparative Example 1, nano-high-energy ball milling and the second mechanical mixing are not performed.

[0064] In the first mechanical mixing step, all SiC particles and aluminum alloy powder were mixed evenly, and the aluminum alloy powder was not divided equally into the first aluminum alloy powder and the second aluminum alloy powder. The ball-to-material ratio was 1:1, the mixer speed was 36 rpm, and the mixing time was 8 h.

[0065] Subsequently, the mixed composite powder was placed in a mold and sintered in a vacuum hot press to obtain an aluminum-based composite ingot. The sintering temperature was 560°C, the holding time was 2 hours, and the applied pressure was 35 MPa. The aluminum-based composite ingot was processed into a rod by hot extrusion. The preheating temperature of the ingot before hot extrusion was 420°C, the holding time was 1 hour, and the extrusion ratio was 20:1. The metallographic structure is shown in FIG. Figure 11 , SiC particles are evenly distributed. After T6 heat treatment, the aluminum matrix composite material has a tensile strength of 646 MPa, a yield strength of 547 MPa, and an elongation of 3.3%.

[0066] Comparative Example 2

[0067] The difference between Comparative Example 2 and Example 1 is that the second mechanical mixing is not performed in Comparative Example 2.

[0068] The SiC particles and aluminum alloy powder were weighed, the mass of the SiC particles was 10 kg, and the mass of the aluminum alloy powder was 90 kg. Stearic acid with a mass fraction of 2% was added, and the powders were mixed evenly using a stirred ball mill under argon protection, and the micronized aluminum alloy powder was nano-sized. The ball-to-material ratio was 10:1, the ball mill speed was 300 rpm, and the ball milling time was 5 h.

[0069] Subsequently, the mixed composite powder was placed in a mold and sintered in a vacuum hot press to obtain an aluminum-based composite ingot. The sintering temperature was 520°C, the holding time was 2 hours, and the applied pressure was 35 MPa. The aluminum-based composite ingot was processed into a rod by hot extrusion. The preheating temperature of the ingot before hot extrusion was 420°C, the holding time was 1 hour, and the extrusion ratio was 20:1. The metallographic structure is shown in FIG. Figure 12 After T6 heat treatment, the aluminum matrix composite material has a tensile strength of 681 MPa, a yield strength of 557 MPa, and an elongation of 2.5%.

[0070] Comparative Example 3

[0071] The difference between Comparative Example 3 and Example 1 is that the mass fraction of SiC particles in the first mechanical mixing is different, wherein the mass of SiC particles is 15 kg and the mass of aluminum alloy powder is 85 kg.

[0072] In Comparative Example 3, nano-high-energy ball milling was not performed; in addition, the particle size of the aluminum alloy powder was also different, with the average particle size of 13 microns accounting for 50% of the aluminum powder and the average particle size of 100 microns accounting for 50%. A mechanical mixer was used to evenly mix all the SiC particles and the aluminum alloy powders of the two particle sizes, with a ball-to-material ratio of 1:1, a mixer speed of 36 rpm, and a mixing time of 8 h.

[0073] The mixed composite powder was placed in a mold and sintered in a vacuum hot press to obtain an aluminum-based composite ingot. The sintering temperature was 560°C, the holding time was 2.5 hours, and the applied pressure was 35 MPa. The aluminum-based composite ingot was processed into a rod by hot extrusion. The preheating temperature of the ingot before hot extrusion was 420°C, the holding time was 1 hour, and the extrusion ratio was 20:1. The metallographic structure is shown in FIG. Figure 13 , SiC particles are unevenly distributed. After T6 heat treatment, the tensile strength of the aluminum matrix composite material is 637 MPa, the yield strength is 590 MPa, and the elongation is 1.2%.

[0074] Comparative Example 4

[0075] The difference between Comparative Example 4 and Example 1 is that the mass fraction of SiC particles in the first mechanical mixing is different, wherein the mass of SiC particles is 15 kg and the mass of aluminum alloy powder is 85 kg.

[0076] In Comparative Example 4, nano-high-energy ball milling was not performed. Otherwise, the aluminum alloy chemical composition was the same as in Example 1, but the aluminum alloy powder particle size was different. Aluminum alloy powder with an average particle size of 13 mm accounted for 50%, and aluminum alloy powder with an average particle size of 200 mm accounted for 50%. All SiC particles and aluminum alloy powders of both particle sizes were uniformly mixed using a mechanical mixer at a ball-to-powder ratio of 1:1. The mixer speed was 36 rpm, and the mixing time was 8 hours.

[0077] The mixed composite powder was placed in a mold and sintered in a vacuum hot press to obtain an aluminum-based composite ingot. The sintering temperature was 560°C, the holding time was 2.5 hours, and the applied pressure was 35 MPa. The aluminum-based composite ingot was processed into a rod by hot extrusion. The preheating temperature of the ingot before hot extrusion was 420°C, the holding time was 1 hour, and the extrusion ratio was 20:1. The metallographic structure is shown in FIG. Figure 14The SiC particles are unevenly distributed at the microscopic level, and the macroscopic structure is similar to a layered structure. After T6 heat treatment, the aluminum-based composite material has a tensile strength of 620 MPa, a yield strength of 569 MPa, and an elongation of 0.9%.

[0078] The physical properties of the above Examples 1-2 and Comparative Examples 1-4 are summarized in Table 1 below.

[0079] Table 1. Physical properties of aluminum-based composite materials of Examples 1-2 and Comparative Examples 1-4

[0080] Performance Analysis

[0081] Compared with the aluminum-based composite materials with uniform structure in Comparative Examples 1 and 2, and the aluminum-based composite materials with micron-scale non-uniform structure in Comparative Examples 3 and 4, the micron-nano composite structure aluminum-based composite materials prepared in Examples 1 and 2 according to the technical solution provided by the present invention exhibit more excellent strong plasticity. Introducing nanocrystals around micron SiC particles can effectively alleviate the crack initiation caused by interfacial stress concentration, thereby improving the strength of the material. At the same time, the nanocrystalline boundary can reduce the scope of the dislocation knockout zone in the near-interface matrix, so that the micron-crystalline aluminum alloy matrix outside the strengthening unit can give full play to the plastic deformation ability, thereby obtaining good ductility. Compared with Example 2, the ball milling time of Example 1 is longer, and the degree of nano-crystalization of the grains in the strengthening unit is higher, so it exhibits higher strength.

[0082] The micron-level non-uniform structure aluminum-based composite materials of Comparative Examples 3 and 4 were obtained by regulating the proportion of aluminum alloy powders of different particle sizes. The grain size in the matrix alloy was all micron-level, except that the distribution pattern of SiC particles was similar to that of Examples 1 and 2, and both had the characteristics of macroscopic uniformity and microscopic non-uniformity. However, the matrix of the aluminum-based composite materials of Comparative Examples 3 and 4 near the SiC / Al interface was not strengthened, and the fundamental problem of material failure caused by interface stress concentration was not solved. In addition, the non-uniform distribution of SiC particles increased the particle content and stress concentration tendency in the microscopic region. Therefore, the micron-level non-uniform structure aluminum-based composite materials exhibited the worst strength and plasticity.

[0083] It should be noted that the above-mentioned order of the embodiments of the present application is for descriptive purposes only and does not represent the superiority or inferiority of the embodiments. The above description is of specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0084] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

[0085] This specification and drawings are merely illustrative of the present application and are intended to cover any and all modifications, variations, combinations, or equivalents within the scope of this application. Obviously, those skilled in the art may make various modifications and variations to this application without departing from the scope of this application. Thus, this application is intended to include such modifications and variations as fall within the scope of this application and its equivalents.

Claims

1. An aluminum-based composite material based on a micro-nano composite structure, characterized in that: The aluminum-based composite material comprises a micron-crystalline aluminum alloy matrix and at least one strengthening unit; the strengthening unit is uniformly dispersed in the micron-crystalline aluminum alloy matrix, and the long axis direction is oriented along a preset direction; The strengthening unit includes non-nanoscale SiC particles and a nanocrystalline aluminum alloy wrapping layer, wherein the nanocrystalline aluminum alloy wrapping layer covers the non-nanoscale SiC particles to form a core-shell structure; The non-nanoscale SiC particles are micron SiC particles, and the particle size of the micron SiC particles ranges from 1 to 100 μm; The average grain size of the nanocrystalline aluminum alloy wrapping layer is 200-500 nm, and the volume ratio of the micron-crystalline aluminum alloy substrate to the nanocrystalline aluminum alloy wrapping layer is 1:1; The number of the non-nanoscale SiC particles in a single strengthening unit is 1 to 20.

2. The aluminum-based composite material based on a micro-nano composite structure according to claim 1, characterized in that: The average grain size of the micron-crystalline aluminum alloy matrix is ​​2-30 μm; Nano-scale η' phase precipitates are uniformly distributed inside the grains of the micron-crystalline aluminum alloy matrix and the nano-crystalline aluminum alloy wrapping layer; the η' phase precipitates are MgZn2.

3. A method for preparing an aluminum-based composite material based on a micro-nano composite structure according to any one of claims 1 to 2, characterized in that: The process comprises the following steps: first mechanical mixing, nanometer high-energy ball milling, second mechanical mixing, ingot preparation, thermal deformation and T6 heat treatment.

4. The method for preparing an aluminum-based composite material based on a micro-nano composite structure according to claim 3, wherein: The first mechanical mixing comprises the following steps: Weighing SiC particles and aluminum alloy powder according to a ratio of 10%-15% by mass to 90%-85% by mass; and dividing the aluminum alloy powder into a first aluminum alloy powder and a second aluminum alloy powder in equal parts by mass; The weighed SiC particles and the first aluminum alloy powder are mixed evenly using a mechanical mixer; the mechanical mixer is a V-type mixer, the ball-to-material ratio is 1:1, the mixer speed is 30-50 rpm, and the mixing time is 6-8 hours to obtain a mixture of the SiC particles and the first aluminum alloy powder.

5. The method for preparing an aluminum-based composite material based on a micro-nano composite structure according to claim 4, wherein: The chemical composition of the aluminum alloy powder is as follows: Zn: 6.0-7.0%, Mg: 2.0-3.0%, Cu: 1.0-2.0%, and the rest is Al and unavoidable impurity elements. The average particle size of the aluminum alloy powder is 10-15 microns.

6. The method for preparing an aluminum-based composite material based on a micro-nano composite structure according to claim 4, wherein: The nano-high energy ball milling process includes the following steps: 2% by mass of stearic acid was added to a mixture of the SiC particles and the first aluminum alloy powder, and the first aluminum alloy powder was nano-crystallized using a stirred ball mill under argon protection to form a reinforcement unit in which micron-SiC particles were wrapped by nanocrystalline aluminum alloy. The ball-to-material ratio was 10:1, the ball milling speed was 300-400 rpm, and the ball milling time was 3-6 hours.

7. The method for preparing an aluminum-based composite material based on a micro-nano composite structure according to claim 6, wherein: The second mechanical mixing comprises the following steps: The second aluminum alloy powder is added to the strengthening unit after nano-high-energy ball milling, and is uniformly mixed using a mechanical mixer with a ball-to-material ratio of 1:1, a mixer speed of 30-50 rpm, and a mixing time of 6-8 hours to obtain a uniform composite powder.

8. The method for preparing an aluminum-based composite material based on a micro-nano composite structure according to claim 7, wherein: The billet preparation process includes the following steps: The composite powder is loaded into a mold and sintered in a vacuum hot pressing furnace to obtain an aluminum-based composite material ingot; the sintering temperature is 500-560° C., the holding time is 2-3 hours, and the applied pressure is 30-50 MPa.

9. The method for preparing an aluminum-based composite material based on a micro-nano composite structure according to claim 8, wherein: The thermal deformation process includes the following steps: The aluminum-based composite material ingot is subjected to hot extrusion deformation processing to form an aluminum-based composite material with a formed structure. Before hot extrusion, the ingot is preheated to 420° C., the holding time is 1 hour, and the extrusion ratio is 20:

1.

10. The method for preparing an aluminum-based composite material based on a micro-nano composite structure according to claim 9, wherein: The T6 heat treatment includes the following steps: The aluminum-based composite material with a formed structure is placed in a muffle furnace for heat preservation, then placed in water for cooling, and then placed in a drying oven for heat preservation, and finally cooled to room temperature in air to obtain an aluminum-based composite material based on a micro-nano composite structure.

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