Preparation method of aluminum-based composite material

Abstract

The invention belongs to the field of material preparation, and particularly relates to a preparation method of an aluminum-based composite material, which is mainly based on a powder metallurgy technology and is characterized in that the aluminum-based composite material is prepared from stainless steel short fibers and pre-alloyed powder through the procedures of ball milling, pressing, extrusion sintering and the like. Through rotation of the mold, the material generates certain pure shear deformation, deformation superposition can refine the structure and crush the original boundary of alloy powder particles, better metallurgical bonding between the particles can be achieved during subsequent sintering, and the purpose of improving the mechanical property of the material is achieved. The density of the Al-xSi-3Cu-0.5 Mg-ySSF composite material reaches 98% or above of the theoretical density, when the mass fraction of Si is 10 wt%, the microhardness and tensile strength of the composite material reach 120 HV and 450 MPa respectively, and important practical value is provided for accelerating and promoting the light weight process of automobiles.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a method for preparing aluminum-based composite materials. Background Technology

[0002] Aluminum-based composite materials, with their lightweight, excellent thermal conductivity, high strength, good wear resistance, excellent casting properties, and certain corrosion resistance, have been widely used in key fields such as the automotive industry, machinery manufacturing, aerospace, transportation, and construction. Taking automotive engine pistons and connecting rods as examples, these components have high requirements for material strength and heat resistance, and aluminum-based composite materials can precisely meet these requirements.

[0003] The Si phase in aluminum-based composites is a reinforcing phase in the matrix. However, the casting process, which produces coarse, polygonal blocky primary Si and long, lamellar eutectic Si, can severely fracture the aluminum alloy matrix and degrade its properties. Therefore, reducing the size of silicon in aluminum-silicon alloys is a key research focus. Summary of the Invention

[0004] In view of this, the present invention discloses a method for preparing aluminum-based composite materials, specifically including the following steps:

[0005] S1. Al-Si-Mg pre-alloyed powder, Cu powder, and stainless steel short fibers are placed in a planetary ball mill for ball milling to prepare Al-xSi-3Cu-0.5Mg-ySSF composite powder.

[0006] In this composite powder system, the numbers preceding the symbols of each component and the variables x and y represent the mass fraction (in %) of that component in the composite powder. Specifically: Al is the matrix phase, x is the mass fraction of Si, ranging from 5% to 20%; Cu has a mass fraction of 3%, and Mg has a mass fraction of 0.5%; y is the mass fraction of stainless steel fiber (SSF), ranging from 1.5% to 4.5%. The mass fractions of Al, Si, and Mg in the composite powder are comprehensively controlled by the mass percentage of each element in the Al-Si-Mg pre-alloy powder pre-alloy, as well as the amount of Cu powder and stainless steel short fiber added.

[0007] The average particle size of Al-Si-Mg pre-alloyed powder is 15 μm, and the average particle size of Cu powder is 10 μm.

[0008] Although aluminum-based powders have large particle sizes and good flowability, their specific surface area is small, resulting in insufficient diffusion driving force during sintering. This leads to increased porosity, decreased density, and reduced mechanical properties (such as strength and hardness) and fatigue resistance of the alloy.

[0009] The small particle size of aluminum-based powder leads to high friction between small particles, resulting in uneven filling during pressing, which may create density gradients and cause cracking or deformation of the green body. In addition, nanoscale powders have extremely high activity, which may lead to abnormal grain growth due to over-sintering, weakening performance and increasing cost. Therefore, this patent uses micron-sized aluminum-based powder as raw material.

[0010] The short stainless steel fibers, 1-2 mm in length, are produced by cutting long stainless steel fibers using a cutting machine. Stainless steel fiber is the primary reinforcing phase; when its content is too low, the composite material's strength and elastic modulus are close to those of undoped aluminum-based composites, failing to fully realize its reinforcing effect. When the fiber content is too high, the fiber-aluminum interface area increases; if the interface bonding is poor (e.g., oxidation, reaction layer), it can become a crack initiation point, leading to a decrease in strength instead of an increase. Therefore, this application limits the stainless steel fiber mass ratio to 1.5%-4.5% to achieve a sufficient reinforcing effect.

[0011] The addition of Cu is 3% of the total mass. Cu can inhibit grain growth and improve the strength of the alloy.

[0012] S2. The Al-xSi-3Cu-0.5Mg-ySSF composite powder and the first lubricant are mixed in a powder mixer to reduce friction between the composite powder particles. The lubricant reduces friction between powder particles and improves flowability. If the lubricant is inadequate, the powder will not fill the mold evenly, resulting in uneven density distribution of the blank (such as localized porosity or density gradients). High friction accelerates mold wear (especially in the mold cavity and punch), shortening its service life.

[0013] S3. Apply the second lubricant to the inner wall of the pressing mold, and place the Al-xSi-3Cu-0.5Mg-ySSF composite powder, which is mixed with the first lubricant, into the pressing mold for pressing to obtain an Al-xSi-3Cu-0.5Mg-ySSF compact. The second lubricant is used to reduce the friction between the composite powder and the mold surface.

[0014] The S4.Al-xSi-3Cu-0.5Mg-ySSF compact is placed in a box furnace and held at 280-320℃ for 2 hours. This heat treatment helps reduce the deformation resistance of the compact in the subsequent rotary extrusion process in step S5.

[0015] During the aforementioned heating process, the Al-xSi-3Cu-0.5Mg-ySSF ingot undergoes significant plastic deformation during the rotary extrusion process, causing a temperature rise. Excessive heating temperature in the box furnace can easily lead to overheating of the Al-xSi-3Cu-0.5Mg-ySSF ingot during the rotary extrusion process. Conversely, lower heating temperatures result in greater deformation resistance in the ingot, leading to rotary extrusion failure.

[0016] S5. The Al-xSi-3Cu-0.5Mg-ySSF preform, after being heated and kept at a specific temperature in step S4, is placed into an extruder for extrusion to obtain an Al-xSi-3Cu-0.5Mg-ySSF composite extruded rod. The extrusion speed is 2~2.5 mm / s. In the extruder, the preform is pushed towards the die by the extrusion rod, causing plastic deformation at the die position to form the Al-xSi-3Cu-0.5Mg-ySSF composite extruded rod. The density of the prepared Al-xSi-3Cu-0.5Mg-ySSF composite extruded rod reaches 98% of the theoretical density through a rotary extrusion process.

[0017] Extrusion can increase the density of the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion bar, allowing internal gases to escape. However, the oxide film on the aluminum powder surface hinders interfacial bonding during sintering, creating a physical barrier at the contact interface that impedes metal atom diffusion and interfacial fusion. This results in a lack of strong metallurgical bonding between powder particles, ultimately leaving porosity in the sintered body and reducing density. In this application, the forward extrusion of the extrusion bar breaks up the oxide film on the aluminum powder surface, facilitating the sintering process.

[0018] Simultaneously, the extrusion process can further reduce the length of the stainless steel fiber powder. The presence of stainless steel fiber powder can, to a certain extent, reduce the size of the Si phase and ensure its uniform dispersion in the matrix, thereby enhancing the dispersion of the second phase.

[0019] S6. Sinter the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod to obtain an aluminum-based composite material.

[0020] Stainless steel fibers combine the fineness and flexibility of fibers with the high strength and high elastic modulus of metals. They also possess excellent electrical and thermal conductivity, corrosion resistance, and wear resistance, making them suitable as reinforcing materials for composite materials. However, precision mechanical cutting can reduce long stainless steel fibers to 1-2 mm lengths. Increasing the number of short stainless steel fibers does not improve the performance of aluminum-based composites; instead, their length can lead to a decrease in material strength as a defect. Furthermore, the oxide film formed on the surface of aluminum powder can hinder the sintering process of aluminum-based composites.

[0021] This application utilizes a ball milling process to prepare stainless steel fiber powder from short stainless steel fibers. The length of the ball-milled stainless steel fiber powder ranges from 30 μm to 150 μm. A subsequent extrusion process further shortens the fiber length, allowing it to be uniformly and densely distributed within the composite powder. Simultaneously, extrusion induces significant plastic deformation in the powder particles, effectively disrupting the oxide film on the surface of the aluminum powder and enhancing its composite effect with the stainless steel fiber powder. This lays the foundation for subsequent sintering, thereby improving the mechanical properties of the sintered Al-xSi-3Cu-0.5Mg-ySSF alloy rods. Furthermore, since the stainless steel fiber powder is made of stainless steel, its addition enhances the heat resistance of the Al-xSi-3Cu-0.5Mg-ySSF alloy rods, enabling them to exhibit excellent application performance in automotive engine pistons, connecting rods, and other components.

[0022] Through the above technical solution, stainless steel short fibers are compositely processed with Al-Si-Mg pre-alloy powder and Cu powder to obtain Al-xSi-3Cu-0.5Mg-ySSF alloy rods. The comprehensive mechanical properties of Al-Si are improved by fiber composite reinforcement. The Si particles can be significantly refined from cast polygonal blocks to micron-sized particles, which are evenly distributed in the matrix, thereby strengthening the dispersion distribution of the second phase.

[0023] As a supplement to the technical solution of this invention, in step S1, the rotation speed of the planetary ball mill is 190-200 r / min, the milling time is 2-6 h, the ball-to-material ratio is 3:2, and the ratio of large stainless steel balls (118-122 mm in diameter), medium balls (72-82 mm in diameter), small balls (32-42 mm in diameter), and ultra-small balls (8-12 mm in diameter) in the ball mill is 3:4:3:10. By ball milling, the length of the stainless steel short fibers is reduced, allowing them to be transformed into stainless steel fiber powder. Al-Si from the Al-Si-Mg pre-alloyed powder is selected as the milling medium; its metallic material can significantly reduce the direct impact force of the steel balls, avoiding cold welding problems in the stainless steel fibers during the ball milling process and reducing the fiber pulverization effect.

[0024] When the ball-to-material ratio and rotational speed are optimally combined, the grinding balls exhibit a typical "waterfall motion" trajectory within the grinding jar—the upper grinding balls, lifted to a certain height by centrifugal force, fall freely along a parabolic trajectory, colliding violently with the lower material. This unique motion pattern organically combines impact crushing and grinding refinement, not only maximizing pulverization efficiency but also ensuring a highly uniform particle size distribution. This process demonstrates excellent energy consumption control, maximizing energy utilization efficiency through optimized process parameters. Practical verification shows that ball milling produces high-quality stainless steel fiber powder with lengths ranging from 30μm to 150μm from short stainless steel fibers, whose performance indicators fully meet the technical requirements of high-end applications such as composite material reinforcement and filter material manufacturing. Regarding the selection of ball milling time, a reasonable milling time can significantly reduce fiber length. When the milling time is less than 2 hours, the ball milling effect on short stainless steel fibers is not significant, resulting in longer stainless steel fiber powder. When the milling time is greater than 6 hours, some stainless steel fiber powder is flattened and pulverized, contrary to the desired fiber powder size.

[0025] As a supplement to the technical solution of this invention, step S1 further includes the following step: The Al-xSi-3Cu-0.5Mg-ySSF composite powder is placed in a vacuum tube furnace for annealing at a temperature of 300~350℃. Since the Al-10Si-Mg pre-alloyed powder is prepared using a rapid solidification (RS) process, its powder preparation process achieves rapid solidification through atomization technology. During this process, internal stress is generated within the powder, which can easily lead to difficulties in subsequent pressing processes. Through the above annealing treatment, the internal stress of the powder can be fully released, thereby ensuring that the Al-xSi-3Cu-0.5Mg-ySSF composite powder can be successfully formed in subsequent pressing steps, guaranteeing its density.

[0026] As a supplement to the technical solution of the present invention, the first lubricant is prepared by mixing ethylene glycol bis-stearamide (EBS) and polyethylene glycol (PEG) in a 1:2 ratio, and the mass of the first lubricant accounts for 0.6% to 0.8% of the total mass of the alloy powder. The first lubricant is mixed with Al-xSi-3Cu-0.5Mg-ySSF composite powder in a powder mixer for 6 to 8 hours.

[0027] The long-chain alkyl groups (stearic acid groups) in EBS molecules can form a uniform lubricating film on the surface of powder particles, significantly reducing friction between particles and between particles and the mold, improving pressing efficiency and demolding properties. It also exhibits high-temperature stability, making it suitable for high-temperature pressing processes, such as warm pressing, and maintaining lubrication before sintering. PEG has good low-temperature lubrication properties, with significant lubrication effects at room temperature to medium temperatures (<150℃), making it suitable for cold pressing processes, such as room-temperature molding. Both lubricants effectively reduce friction and mold wear, balancing low-temperature lubrication and high-temperature stability. A mixture of the two lubricants maintains good lubrication during cold pressing and also during subsequent extrusion at certain temperatures. When the mass ratio of EBS to PEG is 1:2, the powder has better flowability, making it more suitable for the initial pressing process and ensuring the smoothness and density of the blank.

[0028] As a supplement to the technical solution of this invention, the pressing pressure in step S3 is 300~600MPa. If the pressing pressure is too low, the aluminum-based billet will not be dense, resulting in poor forming effect; if the pressure is too high, the billet will harden severely, causing it to break at the exit position, resulting in poor forming effect.

[0029] As a supplement to the technical solution of the present invention, the second lubricant is prepared by mixing a 5% PEG solution and mineral oil at a volume ratio of 3:1 and stirring evenly. Before mixing, the PEG needs to be dissolved in deionized water to prepare a 5% PEG solution, and then stirred on a magnetic stirrer for 30 minutes.

[0030] Mineral oils offer good oil film strength and anti-wear properties, making them suitable for high-load or boundary lubrication conditions.

[0031] PEG aqueous solution: possesses excellent extreme pressure and water-based lubrication properties, reducing the coefficient of friction, especially at high speeds or low temperatures during startup. When mixed: the two complement each other, maintaining oil film durability while improving lubrication uniformity and heat dissipation.

[0032] As a supplement to the technical solution of the present invention, the extrusion press in step S5 includes a hydraulic press, a three-phase asynchronous motor, an extrusion rod, an extrusion rod fixing plate, an upper base plate, a die sleeve, an extrusion cylinder, a variable diameter die, a lower base plate, a thrust rolling bearing, a transmission shaft, a bushing, a CNC operating cabinet, a WPO147 type reducer, and a frequency converter.

[0033] The extrusion cylinder has a cylindrical structure with a cylindrical through hole at its axial position for placing the extrusion rod and the Al-xSi-3Cu-0.5Mg-ySSF compact.

[0034] The variable-diameter die has a cylindrical structure with a cylindrical through-hole at its axial center. One end of the variable-diameter die abuts against one end of the extrusion cylinder, ensuring that the cylindrical through-hole of the extrusion cylinder and the axis of the variable-diameter die are aligned. The Al-xSi-3Cu-0.5Mg-ySSF preform is extruded towards the variable-diameter die through an extrusion rod. The cylindrical through-hole in the variable-diameter die, located near one end of the extrusion cylinder, has a tapered angle on its inner wall, with an angle of 30~45°. The tapered angle allows for smoother metal flow during extrusion, reducing shear stress and preventing surface cracks. This is suitable for low-plasticity materials, reducing the contact area with the die, lowering friction, and decreasing extrusion pressure. This is suitable for high-plasticity materials, such as Al-based composites. An angle that is too small may increase frictional resistance, leading to increased extrusion pressure and accelerated die wear. An angle that is too large may cause severe metal deformation, easily resulting in central cracks or shrinkage cavities.

[0035] The diameter of the cylindrical through hole inside the variable diameter die, which serves as an extrusion die, should be smaller than the diameter of the cylindrical through hole inside the extrusion cylinder.

[0036] By setting the conical angle, the plastic deformation of the Al-xSi-3Cu-0.5Mg-ySSF compact during the extrusion process can be transitioned at the conical angle position, ultimately extruding the compact into the cylindrical through hole.

[0037] One end of the drive shaft is connected to the variable diameter die via a cross coupling, while the other end of the conventional shaft is connected to a three-phase asynchronous motor. The rotation of the drive shaft drives the rotation of the variable diameter die. Through the rotation of the variable diameter die and the extrusion of the extrusion rod, the Al-xSi-3Cu-0.5Mg-ySSF ingot is subjected to compressive and shear stresses during the extrusion process.

[0038] The die sleeve is disposed on the outside of the extrusion cylinder and the variable diameter die. The extrusion cylinder and the die sleeve are fixedly connected, preferably by a screw connection.

[0039] The lower base plate is screwed to the end of the die sleeve. A through hole is provided in the middle of the lower base plate for the drive shaft to pass through. The drive shaft passes through the lower base plate and connects to the variable diameter die. A thrust rolling bearing is provided between the end of the variable diameter die away from the extrusion cylinder and the lower base plate. During the extrusion process, the variable diameter die is subjected to a thrust in the direction of the thrust rolling bearing. Through the arrangement of the drive shaft and the thrust rolling bearing, the variable diameter die can rotate within the die sleeve.

[0040] The extrusion rod is a cylindrical rod-shaped structure. One end of the extrusion rod is equipped with an upper base plate, which is connected to a hydraulic press. The hydraulic press drives the extrusion rod to move into the extrusion cylinder to extrude the Al-xSi-3Cu-0.5Mg-ySSF ingot. The drive shaft is equipped with a bushing on its outside.

[0041] Preferably, the diameter of the cylindrical through hole of the extrusion cylinder is 29 mm, and the diameter of the cylindrical through hole of the variable diameter die is 8 mm.

[0042] Preferably, the extrusion rod is fixedly connected to the upper base plate via an extrusion rod fixing plate to ensure that the upper base plate and the extrusion rod fixing plate are in close horizontal contact, thus avoiding stress concentration that could damage the mold.

[0043] Preferably, the axis of the rotating shaft is provided with a through hole that communicates with the cylindrical through hole on the variable diameter die, so that when the Al-xSi-3Cu-0.5Mg-ySSF compact is extruded to form a long Al-xSi-3Cu-0.5Mg-ySSF composite material extrusion bar, the rotating shaft can provide a accommodating space.

[0044] Preferably, the die sleeve has a first through hole and a second through hole. The first through hole is used to house the extrusion cylinder. The second through hole is used to house the variable diameter die, the outer periphery of which is tapered near the extrusion cylinder. The structure of the second through hole is adapted to the structure of the variable diameter die, allowing the variable diameter die to rotate stably within the second through hole. The tapered structure on the outer periphery of the variable diameter die facilitates installation and improves rotational stability.

[0045] The formula for the speed of a three-phase asynchronous motor is as follows:

[0046] (1)

[0047] In the above formula (1), n ​​is the motor speed, f is the power supply frequency, p is the number of pole pairs of the motor, and s is the slip rate.

[0048] The inverter outputs a maximum frequency of 50Hz, the motor has 2 pole pairs, a slip of 0.04, and a maximum output speed of approximately 143 r / min. At 20Hz, the rotational speed is 56 r / min; at 25Hz, it is 70 r / min; and at 30Hz, it is 84 r / min. The extrusion speed is 4 mm / s at 100% flow rate, 1.6 mm / s at 40% flow rate, 2 mm / s at 50% flow rate, and 2.4 mm / s at 60% flow rate. The maximum pressure is 25 MPa, and the working stroke is 500 mm. The reducer has a reduction ratio of 10:1, and the extrusion speed is adjustable from 0 to 4 mm / s, while the rotational speed is adjustable from 0 to 143 r / min.

[0049] The control console switches control the start of the equipment. The required rotation speed and positive extrusion speed are set through the frequency converter and CNC operating cabinet. The frequency converter controls the motor to output a high-speed frequency. The high-speed power output by the motor is reduced by the speed reducer, which increases the output torque and also reduces the load inertia.

[0050] As a supplement to the technical solution of the present invention, the rotation speed of the variable diameter die in the extruder is 50~66 r / min.

[0051] During positive extrusion, the rotation of the die induces pure shear deformation in the material. The superposition of deformations refines the microstructure and breaks down the original boundaries of the alloy powder particles. This allows for better metallurgical bonding between particles during subsequent sintering, thereby improving the material's mechanical properties. Simultaneously, the length of the stainless steel fiber powder is further reduced by 4-10 μm under double deformation, further shortening the fiber length. During the material's service life, the stainless steel fiber powder and Cu particles exhibit a synergistic pinning effect, further enhancing hardness and strength.

[0052] In the aforementioned process, a variable-diameter die rotation speed exceeding 66 r / min results in significant shear deformation of the compact, leading to greater heat generation from powder particle friction. This degrades the material surface quality and introduces defects, potentially causing the compact temperature to rise and resulting in overheating of the Al-xSi-3Cu-0.5Mg-ySSF composite extruded rod. The initial purpose of rotary extrusion is to improve material properties through shear strain; however, low speeds may weaken this effect, resulting in limited grain refinement. When the variable-diameter die rotation speed is below 50 r / min, poor grain refinement occurs, leaving residual pores within the alloy and leading to poor density.

[0053] During the extrusion process, the Al-xSi-3Cu-0.5Mg-ySSF preform is first placed in the extrusion cylinder, and then the Al-xSi-3Cu-0.5Mg-ySSF preform is plastically deformed at the variable diameter die position by the extrusion rod, and the diameter is reduced. Under the dual action of extrusion force and shear force, an Al-xSi-3Cu-0.5Mg-ySSF composite material extrusion rod is formed.

[0054] As a supplement to the technical solution of the present invention, the sintering process of the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod in step S6 is specifically as follows: the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod is placed in a vacuum tube furnace, and nitrogen is used as a protective atmosphere. It is heated to 300~350℃ at a heating rate of 3.5℃ / min for pre-sintering to remove residual lubricant oil stains and other substances on the alloy surface. Then, it is heated to 500~525℃ at 5℃ / min and held for 2 hours, and then cooled with the furnace.

[0055] If the holding temperature is too low during sintering, physical bonds and grain boundaries exist within the alloy, but the metallurgical bonding between grains is incomplete, leading to a decrease in performance. If the holding temperature is too high during sintering, the elements in the alloy will reach the alloy eutectic point, resulting in over-burning, a significant decrease in density, and a decline in the mechanical properties of Al-xSi-3Cu-0.5Mg-ySSF alloy rods.

[0056] This application adjusts the die rotation speed and extrusion bar descent speed during the extrusion process using a frequency converter and CNC control box. The variable-diameter die exit shape is circular, the positive extrusion speed is 2.5 mm / s, and the rotation speed is 50~66 r / min for the Al-xSi-3Cu-0.5Mg-ySSF composite material extrusion bar. Under double extrusion, the porosity of the powder metallurgy material is eliminated, the alumina film is completely pulverized, and the material density is higher after sintering, reaching 98% of the theoretical density. Furthermore, the sintering process can form a CuAl2 strengthening phase, further improving the alloy strength. However, the rotary extrusion process results in significant deformation. If the holding temperature is too low, extrusion is difficult; if the holding temperature is too high, the extrusion exit temperature is too high, leading to overheating of the Al-xSi-3Cu-0.5Mg-ySSF alloy, resulting in poor surface quality and performance. Excessive rotation speed increases the heat generated by powder particle friction, leading to a decrease in material surface quality and defects.

[0057] Beneficial Effects: This invention discloses a method for preparing aluminum-based composite materials. The method involves ball milling, compacting, extruding, and sintering stainless steel short fibers with pre-alloyed powder and Cu powder to obtain the final aluminum-based composite material. During the material's service life, the stainless steel fiber powder and Cu particles exhibit a synergistic pinning effect, further improving hardness and strength. Simultaneously, the extruder's structural design allows for pure shear deformation of the compact. The superposition of deformations refines the microstructure and breaks down the original boundaries of the alloy powder particles, leading to better metallurgical bonding between particles during subsequent sintering, thus improving the material's mechanical properties. Furthermore, the length of the stainless steel fiber powder is further reduced to 4-10 μm under double deformation. The final aluminum-based composite material achieves a density of over 98%, with optimal microhardness and tensile strength reaching 120 HV and 450 MPa, respectively. Attached Figure Description

[0058] Figure 1 SEM images of Al-xSi-3Cu-0.5Mg-ySSF composite powders with different ball milling times.

[0059] Figure 2 Photos of Al-xSi-3Cu-0.5Mg-ySSF billets under different pressing pressures.

[0060] Figure 3 (a) is a schematic diagram of the extrusion principle; Figure 3 (b) is a schematic diagram of the stress in the strong shear deformation zone of Al-xSi-3Cu-0.5Mg-ySSF billet during extrusion.

[0061] Figure 4 (a) is a macroscopic photograph of Al-xSi-3Cu-0.5Mg-ySSF billet after heat preservation;Figure 4 (b) to Figure 4 (d) is a physical image of the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion bar obtained by extruding Al-xSi-3Cu-0.5Mg-ySSF preforms at different heat preservation temperatures; Figure 4 (e) is a physical image of the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion bar at a rotation speed of 84 r / min.

[0062] Figure 5 Images of aluminum-based composite materials prepared at different sintering temperatures.

[0063] Figure 6 Metallographic micrographs of aluminum-based composite materials.

[0064] Figure 7 Line graphs showing the tensile strength of aluminum-based composite materials obtained after different ball milling times.

[0065] Figure 8 Line graphs showing the microhardness and tensile strength of aluminum-based composite materials prepared under different stainless steel fiber powder contents.

[0066] Figure 9 A bar chart showing the tensile strength of aluminum-based composite materials prepared under different sintering temperatures.

[0067] Figure 10 XRD pattern of aluminum-based composite material.

[0068] Figure 11 Metallographic micrographs of aluminum-based composite materials at different sintering temperatures.

[0069] Figure 12 The fracture morphology of aluminum-based composite materials obtained by fracture morphology analysis experiments after different ball milling times is shown.

[0070] Figure 13 Metallographic micrograph of aluminum-based composite material prepared at a variable diameter die rotation speed of 0 r / min.

[0071] Figure 14 This is a schematic diagram of the extruder structure of the present invention.

[0072] Figure 15 This is a schematic diagram of the variable diameter die structure of the extruder of the present invention.

[0073] Figure 14 , Figure 15 middle:

[0074] 1. Extrusion rod, 2. Extrusion rod fixing plate, 3. Upper base plate, 4. Die sleeve, 5. Extrusion cylinder, 6. Variable diameter die, 7. Lower base plate, 8. Thrust rolling bearing, 9. Drive shaft, 10. Bushing, 11. Taper angle. Detailed Implementation

[0075] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0076] like Figure 3 , Figure 14 , Figure 15 As shown, the present invention first discloses an extrusion press, including a hydraulic press, a three-phase asynchronous motor, an extrusion rod 1, an extrusion rod fixing plate 2, an upper base plate 3, a die sleeve 4, an extrusion cylinder 5, a variable diameter die 6, a lower base plate 7, a thrust rolling bearing 8, a transmission shaft 9, a bushing 10, a CNC operating cabinet, a WPO147 type reducer, and a frequency converter.

[0077] The extrusion cylinder 5 has a cylindrical structure with a cylindrical through hole at its axial position for placing the extrusion rod 1 and the Al-xSi-3Cu-0.5Mg-ySSF blank.

[0078] The variable-diameter die 6 has a cylindrical structure with a cylindrical through-hole at its axial center. One end of the variable-diameter die 6 abuts against one end of the extrusion cylinder 5, ensuring that the cylindrical through-hole of the extrusion cylinder 5 and the axial center of the variable-diameter die 6 are aligned. The Al-xSi-3Cu-0.5Mg-ySSF preform is extruded towards the variable-diameter die 6 via the extrusion rod 1. The cylindrical through-hole in the variable-diameter die 6 is located near one end of the extrusion cylinder 5, and its inner wall has a tapered angle 11, with an angle of 30~45°. An 11-degree tapered angle allows for smoother metal flow during extrusion, reduces shear stress, and avoids surface cracks. This is suitable for low-plasticity materials, reducing the contact area with the die and lowering friction, thus reducing extrusion pressure. This is suitable for high-plasticity materials, such as Al-based composites. An angle that is too small may increase frictional resistance, leading to increased extrusion pressure and accelerated die wear. An angle that is too large may cause severe metal deformation, easily resulting in central cracks or shrinkage cavities.

[0079] The diameter of the cylindrical through hole inside the variable diameter die 6, which serves as an extrusion die, should be smaller than the diameter of the cylindrical through hole inside the extrusion cylinder 5.

[0080] By setting the cone angle 11, the plastic deformation of the Al-xSi-3Cu-0.5Mg-ySSF compact during the extrusion process can be transitioned at the cone angle 11 position, and finally the compact is extruded into the cylindrical through hole.

[0081] One end of the drive shaft 9 is connected to the variable diameter die 6 via a cross coupling, and the other end of the drive shaft is connected to a three-phase asynchronous motor. The rotation of the drive shaft 9 drives the rotation of the variable diameter die 6. Through the rotation of the variable diameter die 6 and the extrusion of the extrusion rod 1, the Al-xSi-3Cu-0.5Mg-ySSF ingot is subjected to compressive stress and shear stress during the extrusion process.

[0082] The die sleeve 4 is disposed on the outside of the extrusion cylinder 5 and the variable diameter die 6. The extrusion cylinder 5 and the die sleeve 4 are fixedly connected, preferably by screw connection.

[0083] The lower base plate 7 is screwed to the end of the die sleeve 4. A through hole for the drive shaft 9 to pass through is provided in the middle of the lower base plate 7. The drive shaft 9 passes through the lower base plate 7 and connects to the variable diameter die 6. A thrust rolling bearing 8 is provided between the end of the variable diameter die 6 away from the extrusion cylinder 5 and the lower base plate 7. During the extrusion process, the variable diameter die 6 is subjected to a thrust in the direction of the thrust rolling bearing 8. Through the arrangement of the drive shaft 9 and the thrust rolling bearing 8, the variable diameter die 6 can rotate within the die sleeve 4.

[0084] The extrusion rod 1 is a cylindrical rod-shaped structure. One end of the extrusion rod 1 is provided with an upper base plate 3, which is connected to a hydraulic press. The hydraulic press drives the extrusion rod 1 to move into the extrusion cylinder 5 to extrude the Al-xSi-3Cu-0.5Mg-ySSF ingot. The drive shaft 9 is provided with a bushing 10 on its outside.

[0085] The CNC control cabinet is used to control the hydraulic press and the three-phase asynchronous motor.

[0086] Preferably, the diameter of the cylindrical through hole of the extrusion cylinder 5 is 29 mm, and the diameter of the cylindrical through hole of the variable diameter die 6 is 8 mm.

[0087] Preferably, the extrusion rod 1 is fixedly connected to the upper base plate 3 through the extrusion rod fixing plate 2, ensuring that the upper base plate 3 and the extrusion rod fixing plate 2 are in close horizontal contact, thus avoiding stress concentration that could damage the mold.

[0088] Preferably, the axis of the rotating shaft is provided with a through hole that communicates with the cylindrical through hole on the variable diameter die 6, so that when the Al-xSi-3Cu-0.5Mg-ySSF compact is formed by extrusion and the Al-xSi-3Cu-0.5Mg-ySSF composite material extrusion bar is long, the rotating shaft can provide a accommodating space.

[0089] Preferably, the die sleeve 4 has a first through hole and a second through hole. The first through hole is used to house the extrusion cylinder 5. The second through hole is used to house the variable diameter die 6, the outer periphery of which is tapered near the extrusion cylinder 5. The structure of the second through hole is adapted to the structure of the variable diameter die 6, allowing the variable diameter die 6 to rotate stably within the second through hole. The tapered structure on the outer periphery of the variable diameter die 6 facilitates installation and improves rotational stability.

[0090] like Figure 3 As shown in (a), this is a schematic diagram of the working principle of the extruder of the present invention. Figure 3 (a) Point A is the zone of strong shear deformation of the compact during the extrusion process. For example... Figure 3 (b) shows a schematic diagram of the stress analysis in the strong shear deformation zone.

[0091] Based on the above-described extruder structural design, this invention discloses a method for preparing aluminum-based composite materials. Specific embodiments and comparative examples are as follows:

[0092] Example 1. A method for preparing an aluminum-based composite material, comprising the following steps:

[0093] S1. Al-Si-Mg pre-alloyed powder, Cu powder, and stainless steel short fibers were placed in a planetary ball mill for ball milling. The rotation speed of the planetary ball mill was 190 r / min, the milling time was 2 h, the ball-to-material ratio was 3:2, and the ratio of large, medium, small, and ultra-small stainless steel balls in the ball mill was 3:4:3:10. This prepared Al-xSi-3Cu-0.5Mg-ySSF composite powder. The average particle size of the Al-Si-Mg pre-alloyed powder was 15 μm, the average particle size of the Cu powder was 10 μm, and the length of the stainless steel short fibers was 1-2 mm. The stainless steel short fibers were made by cutting stainless steel long fibers using a cutting machine at a cutting speed of 400 times / min. The mass fraction of Cu in the Al-xSi-3Cu-0.5Mg-ySSF composite powder was 3%, the mass fraction of Mg was 0.5%, x was 10%, and y was 1.5%.

[0094] The Al-xSi-3Cu-0.5Mg-ySSF composite powder was then placed in a vacuum tube furnace for annealing at a temperature of 300℃.

[0095] S2. The Al-xSi-3Cu-0.5Mg-ySSF composite powder and the first lubricant are mixed in a powder mixer. The first lubricant is prepared by mixing ethylene glycol bis-stearamide (EBS) and polyethylene glycol (PEG) in a 1:2 ratio, and the mass of the first lubricant accounts for 0.6% of the total mass of the alloy powder. The first lubricant and the Al-xSi-3Cu-0.5Mg-ySSF composite powder are mixed in the powder mixer for 6 hours.

[0096] S3. The second lubricant is coated on the inner wall of the pressing mold. The Al-xSi-3Cu-0.5Mg-ySSF composite powder, mixed with the first lubricant, is placed into the pressing mold and pressed at a pressure of 300 MPa to form a cylindrical blank with a diameter of 30 mm, thus obtaining an Al-xSi-3Cu-0.5Mg-ySSF compact. The second lubricant is used to reduce the friction between the composite powder and the mold surface. The second lubricant is prepared by mixing PEG dissolved in deionized water and gasoline at a volume ratio of 3:1 and stirring evenly. Before mixing, the PEG dissolved in deionized water needs to be stirred on a magnetic stirrer for 30 minutes.

[0097] The S4.Al-xSi-3Cu-0.5Mg-ySSF compact was placed in a box furnace and held at 300℃ for 2 hours.

[0098] S5. The Al-xSi-3Cu-0.5Mg-ySSF preform, after being heated and kept at a certain temperature in step S4, is placed into an extruder for extrusion to obtain an Al-xSi-3Cu-0.5Mg-ySSF composite material extruded bar. The extrusion speed is 2.5 mm / s, and the rotation speed of the variable diameter die 6 is 50 r / min. A schematic diagram of the green billet rotary extrusion is shown below. Figure 3 As shown in (a), the force diagram of the strong shear deformation zone during green billet rotational extrusion is as follows: Figure 3 As shown in (b), rotary extrusion is performed at an extrusion ratio of 8.

[0099] S6. Sinter the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod to obtain an aluminum-based composite material. The sintering process of the extrusion rod is as follows: the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod is placed in a vacuum tube furnace, and pre-sintered at 300°C with nitrogen as the protective atmosphere at a heating rate of 3.5°C / min to remove residual lubricant oil stains on the alloy surface. Then, it is heated to 500°C at 5°C / min and held for 2 hours, followed by furnace cooling.

[0100] like Figure 1 As shown in (b), the SEM image of the composite powder after ball milling in step S1 of this embodiment shows that the stainless steel short fibers are ball milled to form stainless steel fiber powder with a length of about 100 μm.

[0101] like Figure 2 (b) shows the actual Al-xSi-3Cu-0.5Mg-ySSF compact obtained by pressing in step S3 in this embodiment, which has a better forming effect.

[0102] like Figure 4 (a) shows the actual product of the Al-xSi-3Cu-0.5Mg-ySSF compact after being heated and kept warm in the box furnace in step S4.

[0103] like Figure 4 (c) shows a physical image of the Al-xSi-3Cu-0.5Mg-ySSF composite material extrusion bar obtained by rotary extrusion in step S5 of this embodiment. It can be seen that its surface is smooth and the extrusion bar is uniform and without deformation.

[0104] like Figure 6 The image shown is a metallographic micrograph of the aluminum-based composite material obtained after sintering in step S6 of this embodiment. It can be seen that Cu, Si, and SSF are uniformly distributed in the aluminum matrix.

[0105] Generally, stainless steel fiber powder refers to extremely short fibers with a length of less than 1 mm or in the micrometer range, and its morphology is closer to that of powder. Stainless steel short fibers usually refer to fibers with a length greater than 1 mm and less than 150 mm.

[0106] Example 2: A method for preparing an aluminum-based composite material, comprising the following steps

[0107] S1. Al-Si-Mg pre-alloyed powder, Cu powder, and stainless steel short fibers were placed in a planetary ball mill and ball-milled at a speed of 190 r / min for 3 hours. The ball-to-material ratio was 3:2, and the ratio of large, medium, small, and ultra-small stainless steel balls in the mill was 3:4:3:10, thus preparing Al-xSi-3Cu-0.5Mg-ySSF composite powder. The average particle size of the Al-Si-Mg pre-alloyed powder was 15 μm, the average particle size of the Cu powder was 10 μm, and the length of the stainless steel short fibers was 1-2 mm. The mass fraction of Si in the Al-xSi-3Cu-0.5Mg-ySSF composite powder was 10%, the mass fraction of Cu was 3%, the mass fraction of Mg was 0.5%, and the content of stainless steel fibers was 4.5%.

[0108] The Al-xSi-3Cu-0.5Mg-ySSF composite powder was then placed in a vacuum tube furnace for annealing at a temperature of 310℃.

[0109] S2. The Al-xSi-3Cu-0.5Mg-ySSF composite powder and the first lubricant are mixed in a powder mixer. The first lubricant is prepared by mixing ethylene glycol bis-stearamide (EBS) and polyethylene glycol (PEG) in a 1:2 ratio, and the mass of the first lubricant accounts for 0.7% of the total mass of the alloy powder. The first lubricant and the Al-xSi-3Cu-0.5Mg-ySSF composite powder are mixed in the powder mixer for 6 hours.

[0110] S3. The second lubricant is coated on the inner wall of the pressing mold. The Al-xSi-3Cu-0.5Mg-ySSF composite powder, mixed with the first lubricant, is placed into the pressing mold and pressed at a pressure of 500 MPa to form a cylindrical blank with a diameter of 30 mm, thus obtaining an Al-xSi-3Cu-0.5Mg-ySSF compact. The second lubricant is used to reduce the friction between the composite powder and the mold surface. The second lubricant is prepared by mixing PEG dissolved in deionized water and gasoline at a volume ratio of 3:1 and stirring evenly. Before mixing, the PEG dissolved in deionized water needs to be stirred on a magnetic stirrer for 30 minutes.

[0111] The S4.Al-xSi-3Cu-0.5Mg-ySSF compact was placed in a box furnace and held at 280℃ for 2 hours.

[0112] S5. The Al-xSi-3Cu-0.5Mg-ySSF preform, after being heated and kept at a certain temperature in step S4, is placed into an extruder for extrusion to obtain an Al-xSi-3Cu-0.5Mg-ySSF composite material extrusion bar. The extrusion speed is 2.5 mm / s, and the rotation speed of the variable diameter die 6 is 55 r / min.

[0113] S6. Sinter the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod to obtain an aluminum-based composite material. The sintering process of the extrusion rod is as follows: the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod is placed in a vacuum tube furnace, and pre-sintered at 330°C with nitrogen as the protective atmosphere at a heating rate of 3.5°C / min to remove residual lubricant oil stains on the alloy surface. Then, it is heated to 525°C at 5°C / min and held for 2 hours, followed by furnace cooling.

[0114] like Figure 2 (c) shows the actual Al-xSi-3Cu-0.5Mg-ySSF compact obtained by pressing in step S3 in this embodiment, which has a better forming effect.

[0115] Example 3: A method for preparing an aluminum-based composite material, comprising the following steps

[0116] S1. Al-Si-Mg pre-alloyed powder, Cu powder, and stainless steel short fibers were placed in a planetary ball mill and ball-milled at a speed of 200 r / min for 3 hours. The ball-to-powder ratio was 3:2, and the ratio of large, medium, small, and ultra-small stainless steel balls in the mill was 3:4:3:10, thus preparing Al-xSi-3Cu-0.5Mg-ySSF composite powder. The average particle size of the Al-Si-Mg pre-alloyed powder was 15 μm, the average particle size of the Cu powder was 10 μm, and the length of the stainless steel short fibers was 1-2 mm. The mass fraction of Si in the Al-xSi-3Cu-0.5Mg-ySSF composite powder was 10%, the mass fraction of Cu was 3%, the mass fraction of Mg was 0.5%, and the mass fraction of stainless steel fibers was 3%.

[0117] The Al-xSi-3Cu-0.5Mg-ySSF composite powder was then placed in a vacuum tube furnace for annealing at a temperature of 300℃.

[0118] S2. The Al-xSi-3Cu-0.5Mg-ySSF composite powder and the first lubricant are mixed in a powder mixer. The first lubricant is prepared by mixing ethylene glycol bis-stearamide (EBS) and polyethylene glycol (PEG) in a 1:2 ratio, and the mass of the first lubricant accounts for 0.7% of the total mass of the alloy powder. The first lubricant and the Al-xSi-3Cu-0.5Mg-ySSF composite powder are mixed in the powder mixer for 7 hours.

[0119] S3. The second lubricant is coated on the inner wall of the pressing mold. The Al-xSi-3Cu-0.5Mg-ySSF composite powder, mixed with the first lubricant, is placed into the pressing mold and pressed at a pressure of 600 MPa to form a cylindrical blank with a diameter of 30 mm, thus obtaining an Al-xSi-3Cu-0.5Mg-ySSF compact. The second lubricant is used to reduce the friction between the composite powder and the mold surface. The second lubricant is prepared by mixing PEG dissolved in deionized water and gasoline at a volume ratio of 3:1 and stirring evenly. Before mixing, the PEG dissolved in deionized water needs to be stirred on a magnetic stirrer for 30 minutes.

[0120] The S4.Al-xSi-3Cu-0.5Mg-ySSF compact was placed in a box furnace and held at 300℃ for 2 hours.

[0121] S5. The Al-xSi-3Cu-0.5Mg-ySSF preform, after being heated and kept at a certain temperature in step S4, is placed into an extruder for extrusion to obtain an Al-xSi-3Cu-0.5Mg-ySSF composite material extrusion bar. The extrusion speed is 2.5 mm / s, and the rotation speed of the variable diameter die 6 is 60 r / min.

[0122] S6. Sinter the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod to obtain an aluminum-based composite material. The sintering process of the extrusion rod is as follows: the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod is placed in a vacuum tube furnace, and pre-sintered at 350°C with nitrogen as the protective atmosphere at a heating rate of 3.5°C / min to remove residual lubricant oil stains on the alloy surface. Then, it is heated to 520°C at 5°C / min and held for 2 hours, followed by furnace cooling.

[0123] like Figure 2 As shown in (d), this is a picture of the Al-xSi-3Cu-0.5Mg-ySSF compact obtained by pressing in step S3 in this embodiment. The forming effect is better.

[0124] like Figure 5 As shown in (a), this is a physical image of the aluminum-based composite material obtained after sintering in step S6 in this embodiment. The surface is smooth and free of overheating defects.

[0125] like Figure 10 The image shows the XRD pattern of the aluminum-based composite material prepared in this embodiment. The pattern clearly shows the formation of SSF (BBC) martensite phase, SSF (FBC) austenite phase, and CuCl2 phase.

[0126] like Figure 11 As shown in (a), this is a metallographic micrograph of the aluminum-based composite material obtained after sintering in step S6 of this embodiment. The surface exhibits excellent metallurgical bonding, with no visible grain boundaries, good density, and a small silicon phase. The eutectic silicon prepared by the traditional casting method is needle-like, while the eutectic silicon prepared by this powder metallurgy process is mainly spherical with a smooth surface.

[0127] like Figure 12 As shown in (b), the fracture morphology of the aluminum-based composite material prepared in this embodiment is clearly visible. It can be clearly seen that the stainless steel fiber and the matrix have a good interface bond, and the presence of stainless steel fiber is clearly visible at the fracture site, without obvious agglomeration. Obvious dimple morphology is visible at the fracture site, indicating that the material has undergone a certain degree of plastic deformation during the fracture process. This further illustrates that this good interface bond enables the stainless steel fiber to effectively bear the load, and under stress, it significantly improves the mechanical properties of the aluminum-based composite material through its own deformation and synergistic effect with the matrix.

[0128] During the tensile process, according to the Kelly-Tyson theory, when the fiber-matrix interface is well bonded, external loads can be transferred to the high-strength stainless steel fiber powder through shear stress in the Al matrix. During tensile testing, the fiber powder bears the primary stress, while the Al matrix transfers stress to the fiber through interfacial shear force. The fiber powder and Cu particles hinder dislocation movement, thereby increasing the material's strength. Furthermore, ball milling and rotary extrusion also martensitize the fibers, further increasing the material's strength and hardness. Stainless steel short fiber powder can significantly improve the hardness and strength of aluminum-based composites, adapting them to service behavior in high-strength, wear-resistant environments.

[0129] Example 4: A method for preparing an aluminum-based composite material, comprising the following steps

[0130] S1. Al-Si-Mg pre-alloyed powder, Cu powder, and stainless steel short fibers were placed in a planetary ball mill and ball-milled at a speed of 195 r / min for 5 h. The ball-to-powder ratio was 3:2, and the ratio of large, medium, small, and ultra-small stainless steel balls in the mill was 3:4:3:10, thus preparing Al-xSi-3Cu-0.5Mg-ySSF composite powder. The average particle size of the Al-Si-Mg pre-alloyed powder was 15 μm, the average particle size of the Cu powder was 10 μm, and the length of the stainless steel short fibers was 1-2 mm. The mass fraction of Si in the Al-xSi-3Cu-0.5Mg-ySSF composite powder was 10%, the mass fraction of Cu was 3%, the mass fraction of Mg was 0.5%, and the mass fraction of stainless steel fibers was 3%.

[0131] The Al-xSi-3Cu-0.5Mg-ySSF composite powder was then placed in a vacuum tube furnace for annealing at a temperature of 320℃.

[0132] S2. The Al-xSi-3Cu-0.5Mg-ySSF composite powder and the first lubricant are mixed in a powder mixer. The first lubricant is prepared by mixing ethylene glycol bis-stearamide (EBS) and polyethylene glycol (PEG) in a 1:2 ratio, and the mass of the first lubricant accounts for 0.8% of the total mass of the alloy powder. The first lubricant and the Al-xSi-3Cu-0.5Mg-ySSF composite powder are mixed in the powder mixer for 8 hours.

[0133] S3. The second lubricant is coated on the inner wall of the pressing mold. The Al-xSi-3Cu-0.5Mg-ySSF composite powder, mixed with the first lubricant, is placed into the pressing mold and pressed at a pressure of 500 MPa to form a cylindrical blank with a diameter of 30 mm, thus obtaining an Al-xSi-3Cu-0.5Mg-ySSF compact. The second lubricant is used to reduce the friction between the composite powder and the mold surface. The second lubricant is prepared by mixing PEG dissolved in deionized water and gasoline at a volume ratio of 3:1 and stirring evenly. Before mixing, the PEG dissolved in deionized water needs to be stirred on a magnetic stirrer for 30 minutes.

[0134] The S4.Al-xSi-3Cu-0.5Mg-ySSF compact was placed in a box furnace and held at 320℃ for 2 hours.

[0135] S5. The Al-xSi-3Cu-0.5Mg-ySSF preform, after being heated and kept at a certain temperature in step S4, is placed into an extruder for extrusion to obtain an Al-xSi-3Cu-0.5Mg-ySSF composite material extrusion bar. The extrusion speed is 2.5 mm / s, and the rotation speed of the variable diameter die 6 is 66 r / min.

[0136] S6. Sinter the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod to obtain an aluminum-based composite material. The sintering process of the extrusion rod is as follows: the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod is placed in a vacuum tube furnace, and pre-sintered at 350°C with nitrogen as the protective atmosphere at a heating rate of 3.5°C / min to remove residual lubricant oil stains on the alloy surface. Then, it is heated to 525°C at 5°C / min and held for 2 hours, followed by furnace cooling.

[0137] Example 5: A method for preparing an aluminum-based composite material, comprising the following steps

[0138] S1. Al-Si-Mg pre-alloyed powder, Cu powder, and stainless steel short fibers were placed in a planetary ball mill and ball-milled at a speed of 200 r / min for 3 hours. The ball-to-powder ratio was 3:2, and the ratio of large, medium, small, and ultra-small stainless steel balls in the mill was 3:4:3:10, thus preparing Al-xSi-3Cu-0.5Mg-ySSF composite powder. The average particle size of the Al-Si-Mg pre-alloyed powder was 15 μm, the average particle size of the Cu powder was 10 μm, and the length of the stainless steel short fibers was 1-2 mm. The mass fraction of Si in the Al-xSi-3Cu-0.5Mg-ySSF composite powder was 5.5%, the mass fraction of Cu was 3%, the mass fraction of Mg was 0.5%, and the mass fraction of stainless steel fibers was 3%.

[0139] The Al-xSi-3Cu-0.5Mg-ySSF composite powder was then placed in a vacuum tube furnace for annealing at a temperature of 300℃.

[0140] S2. The Al-xSi-3Cu-0.5Mg-ySSF composite powder and the first lubricant are mixed in a powder mixer. The first lubricant is prepared by mixing ethylene glycol bis-stearamide (EBS) and polyethylene glycol (PEG) in a 1:2 ratio, and the mass of the first lubricant accounts for 0.7% of the total mass of the alloy powder. The first lubricant and the Al-xSi-3Cu-0.5Mg-ySSF composite powder are mixed in the powder mixer for 7 hours.

[0141] S3. The second lubricant is coated on the inner wall of the pressing mold. The Al-xSi-3Cu-0.5Mg-ySSF composite powder, mixed with the first lubricant, is placed into the pressing mold and pressed at a pressure of 600 MPa to form a cylindrical blank with a diameter of 30 mm, thus obtaining an Al-xSi-3Cu-0.5Mg-ySSF compact. The second lubricant is used to reduce the friction between the composite powder and the mold surface. The second lubricant is prepared by mixing PEG dissolved in deionized water and gasoline at a volume ratio of 3:1 and stirring evenly. Before mixing, the PEG dissolved in deionized water needs to be stirred on a magnetic stirrer for 30 minutes.

[0142] The S4.Al-xSi-3Cu-0.5Mg-ySSF compact was placed in a box furnace and held at 300℃ for 2 hours.

[0143] S5. The Al-xSi-3Cu-0.5Mg-ySSF preform, after being heated and kept at a certain temperature in step S4, is placed into an extruder for extrusion to obtain an Al-xSi-3Cu-0.5Mg-ySSF composite material extrusion bar. The extrusion speed is 2.5 mm / s, and the rotation speed of the variable diameter die 6 is 60 r / min.

[0144] S6. Sinter the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod to obtain an aluminum-based composite material. The sintering process of the extrusion rod is as follows: the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod is placed in a vacuum tube furnace, and pre-sintered at 350°C with nitrogen as the protective atmosphere at a heating rate of 3.5°C / min to remove residual lubricant oil stains on the alloy surface. Then, it is heated to 520°C at 5°C / min and held for 2 hours, followed by furnace cooling.

[0145] Example 6: A method for preparing an aluminum-based composite material, comprising the following steps

[0146] S1. Al-Si-Mg pre-alloyed powder, Cu powder, and stainless steel short fibers were placed in a planetary ball mill and ball-milled at a speed of 200 r / min for 3 hours. The ball-to-powder ratio was 3:2, and the ratio of large, medium, small, and ultra-small stainless steel balls in the mill was 3:4:3:10, thus preparing Al-xSi-3Cu-0.5Mg-ySSF composite powder. The average particle size of the Al-Si-Mg pre-alloyed powder was 15 μm, the average particle size of the Cu powder was 10 μm, and the length of the stainless steel short fibers was 1-2 mm. The mass fraction of Si in the Al-xSi-3Cu-0.5Mg-ySSF composite powder was 18%, the mass fraction of Cu was 3%, the mass fraction of Mg was 0.5%, and the mass fraction of stainless steel fibers was 3%.

[0147] The Al-xSi-3Cu-0.5Mg-ySSF composite powder was then placed in a vacuum tube furnace for annealing at a temperature of 300℃.

[0148] S2. The Al-xSi-3Cu-0.5Mg-ySSF composite powder and the first lubricant are mixed in a powder mixer. The first lubricant is prepared by mixing ethylene glycol bis-stearamide (EBS) and polyethylene glycol (PEG) in a 1:2 ratio, and the mass of the first lubricant accounts for 0.7% of the total mass of the alloy powder. The first lubricant and the Al-xSi-3Cu-0.5Mg-ySSF composite powder are mixed in the powder mixer for 7 hours.

[0149] S3. The second lubricant is coated on the inner wall of the pressing mold. The Al-xSi-3Cu-0.5Mg-ySSF composite powder, mixed with the first lubricant, is placed into the pressing mold and pressed at a pressure of 600 MPa to form a cylindrical blank with a diameter of 30 mm, thus obtaining an Al-xSi-3Cu-0.5Mg-ySSF compact. The second lubricant is used to reduce the friction between the composite powder and the mold surface. The second lubricant is prepared by mixing PEG dissolved in deionized water and gasoline at a volume ratio of 3:1 and stirring evenly. Before mixing, the PEG dissolved in deionized water needs to be stirred on a magnetic stirrer for 30 minutes.

[0150] The S4.Al-xSi-3Cu-0.5Mg-ySSF compact was placed in a box furnace and held at 300℃ for 2 hours.

[0151] S5. The Al-xSi-3Cu-0.5Mg-ySSF preform, after being heated and kept at a certain temperature in step S4, is placed into an extruder for extrusion to obtain an Al-xSi-3Cu-0.5Mg-ySSF composite material extrusion bar. The extrusion speed is 2.5 mm / s, and the rotation speed of the variable diameter die 6 is 60 r / min.

[0152] S6. Sinter the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod to obtain an aluminum-based composite material. The sintering process of the extrusion rod is as follows: the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod is placed in a vacuum tube furnace, and pre-sintered at 350°C with nitrogen as the protective atmosphere at a heating rate of 3.5°C / min to remove residual lubricant oil stains on the alloy surface. Then, it is heated to 520°C at 5°C / min and held for 2 hours, followed by furnace cooling.

[0153] Comparative Example 1: The difference between Comparative Example 1 and Example 3 lies only in step S1:

[0154] S1. Al-Si-Mg pre-alloyed powder, Cu powder, and stainless steel short fibers were placed in a planetary ball mill and ball-milled at a speed of 200 r / min for 1.5 h. The ball-to-powder ratio was 3:2, and the ratio of large, medium, small, and ultra-small stainless steel balls in the mill was 3:4:3:10, thus preparing Al-xSi-3Cu-0.5Mg-ySSF composite powder. The average particle size of the Al-Si-Mg pre-alloyed powder was 15 μm, the average particle size of the Cu powder was 10 μm, and the length of the stainless steel short fibers was 1-2 mm. The mass fraction of Si in the Al-xSi-3Cu-0.5Mg-ySSF composite powder was 10%, the mass fraction of Cu was 3%, the mass fraction of Mg was 0.5%, and the mass fraction of stainless steel fibers was 3%.

[0155] The Al-xSi-3Cu-0.5Mg-ySSF composite powder was then placed in a vacuum tube furnace for annealing at a temperature of 300℃.

[0156] like Figure 1 As shown in (a), this is the SEM image of the composite powder after ball milling in step S1 of this embodiment. The ball milling time in this comparative example is relatively short, and it can be seen that the stainless steel short fibers are ball milled to form stainless steel fiber powder with a length of about 200 μm.

[0157] like Figure 12 As shown in (a), the fracture morphology of the aluminum-based composite material prepared in this comparative example is shown. Due to the long length of the stainless steel fiber after the ball milling process, the aluminum matrix and its interface are intersected, and the fracture surface is obviously rough. The preparation process failed to achieve the best density.

[0158] Comparative Example 2: The difference between Comparative Example 2 and Example 3 lies only in step S1:

[0159] S1. Al-Si-Mg pre-alloyed powder, Cu powder, and stainless steel short fibers were placed in a planetary ball mill and ball-milled at a speed of 200 r / min for 8 hours. The ball-to-powder ratio was 3:2, and the ratio of large, medium, small, and ultra-small stainless steel balls in the mill was 3:4:3:10, thus preparing Al-xSi-3Cu-0.5Mg-ySSF composite powder. The average particle size of the Al-Si-Mg pre-alloyed powder was 15 μm, the average particle size of the Cu powder was 10 μm, and the length of the stainless steel short fibers was 1-2 mm. The mass fraction of Si in the Al-xSi-3Cu-0.5Mg-ySSF composite powder was 10%, the mass fraction of Cu was 3%, the mass fraction of Mg was 0.5%, and the mass fraction of stainless steel fibers was 3%.

[0160] The Al-xSi-3Cu-0.5Mg-ySSF composite powder was then placed in a vacuum tube furnace for annealing at a temperature of 300℃.

[0161] like Figure 1 As shown in (d), this is the SEM image of the composite powder after ball milling in step S1 of this comparative example. The ball milling time in this comparative example is relatively long, and it can be seen that the stainless steel fiber powder formed after ball milling of stainless steel short fibers is in powder form.

[0162] like Figure 12 As shown in (c), the fracture morphology of the aluminum-based composite material prepared in this comparative example is clearly visible. Since the stainless steel fibers are in powder form after the ball milling process, it can be clearly seen that there are relatively few stainless steel fibers present in its fracture surface.

[0163] Comparative Example 3: The difference between Comparative Example 3 and Example 3 lies only in step S3:

[0164] S3. The second lubricant is coated on the inner wall of the pressing mold. The Al-xSi-3Cu-0.5Mg-ySSF composite powder, mixed with the first lubricant, is placed into the pressing mold and pressed at a pressure of 200 MPa to form a cylindrical blank with a diameter of 30 mm, thus obtaining an Al-xSi-3Cu-0.5Mg-ySSF compact. The second lubricant is used to reduce the friction between the composite powder and the mold surface. The second lubricant is prepared by mixing PEG dissolved in deionized water and gasoline at a volume ratio of 3:1 and stirring evenly. Before mixing, the PEG dissolved in deionized water needs to be stirred on a magnetic stirrer for 30 minutes.

[0165] like Figure 1 (c) shows the SEM image of the composite powder after ball milling in step S1 of this embodiment. The ball milling time in this comparative example is relatively short, and it can be seen that the stainless steel short fibers are ball milled to form stainless steel fiber powder with a length of about 50 μm.

[0166] like Figure 2As shown in (a), this is a picture of the Al-xSi-3Cu-0.5Mg-ySSF compact prepared in step S3 in this comparative example. The pressing pressure is too low, the aluminum-based billet is not dense, and the forming effect is poor.

[0167] Comparative Example 4: The difference between Comparative Example 4 and Example 3 lies only in step S3:

[0168] S3. The second lubricant is coated on the inner wall of the pressing mold. The Al-xSi-3Cu-0.5Mg-ySSF composite powder, mixed with the first lubricant, is placed into the pressing mold and pressed at a pressure of 800 MPa to form a cylindrical blank with a diameter of 30 mm, thus obtaining an Al-xSi-3Cu-0.5Mg-ySSF compact. The second lubricant is used to reduce the friction between the composite powder and the mold surface. The second lubricant is prepared by mixing PEG dissolved in deionized water and gasoline at a volume ratio of 3:1 and stirring evenly. Before mixing, the PEG dissolved in deionized water needs to be stirred on a magnetic stirrer for 30 minutes.

[0169] like Figure 2 As shown in (e), this is a picture of the Al-xSi-3Cu-0.5Mg-ySSF compact prepared in step S3 in this comparative example. The pressure was too high, the compact hardened severely, which caused it to break at the exit position and the forming effect was poor.

[0170] Comparative Example 5: The difference between Comparative Example 5 and Example 3 lies only in step S4:

[0171] The S4.Al-xSi-3Cu-0.5Mg-ySSF compact was placed in a box furnace and held at 260℃ for 2 hours.

[0172] like Figure 4 (b) shows the actual product of this comparative example after being kept warm in step S4 and then extruded in the extruder. Because the heat preservation temperature was too low, the extrusion was difficult to carry out, resulting in extrusion failure.

[0173] Comparative Example 6: The difference between Comparative Example 6 and Example 3 lies only in step S4:

[0174] The S4.Al-xSi-3Cu-0.5Mg-ySSF compact was placed in a box furnace and held at 360℃ for 2 hours.

[0175] like Figure 4 As shown in (d), this is a picture of the actual object after the comparative example was heat-preserved in step S4 and then extruded in the extruder. The heat preservation temperature was too high and the extrusion outlet temperature was too high, which caused the alloy to overheat and the surface quality to deteriorate.

[0176] Comparative Example 7: The difference between Comparative Example 7 and Example 3 lies only in step S5:

[0177] S5. The Al-xSi-3Cu-0.5Mg-ySSF preform, after being heated and kept at a certain temperature in step S4, is placed into an extruder for extrusion to obtain an Al-xSi-3Cu-0.5Mg-ySSF composite material extrusion bar. The extrusion speed is 2.5 mm / s, and the rotation speed of the variable diameter die 6 is 84 r / min.

[0178] like Figure 4 As shown in (e), this is a physical image of the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion bar obtained after extrusion in step S5 in this comparative example. The excessive rotation speed of the variable diameter die 6 results in a large amount of heat generated by the friction of powder particles, which leads to a decrease in the surface quality of the material and is accompanied by cracking defects.

[0179] Comparative Example 8: The difference between Comparative Example 8 and Example 3 lies only in step S5:

[0180] S5. The Al-xSi-3Cu-0.5Mg-ySSF preform, after being heated and kept at a certain temperature in step S4, is placed into an extruder for extrusion to obtain an Al-xSi-3Cu-0.5Mg-ySSF composite material extrusion bar. The extrusion speed is 2.5 mm / s, and the rotation speed of the variable diameter die 6 is 40 r / min.

[0181] The comparative variable diameter die has a relatively low rotational speed.

[0182] Comparative Example 9: The difference between Comparative Example 9 and Example 3 lies only in step S1:

[0183] S1. Al-10Si-Mg pre-alloyed powder, Cu powder, and stainless steel short fibers were placed in a planetary ball mill and ball-milled at a speed of 200 r / min for 3 hours. The ball-to-material ratio was 3:2, and the ratio of large, medium, small, and ultra-small stainless steel balls in the mill was 3:4:3:10, thus preparing Al-xSi-3Cu-0.5Mg-ySSF composite powder. The average particle size of the Al-Si-Mg pre-alloyed powder was 15 μm, the average particle size of the Cu powder was 10 μm, and the length of the stainless steel short fibers was 1-2 mm. The mass fraction of Si in the Al-xSi-3Cu-0.5Mg-ySSF composite powder was 10%, the mass fraction of Cu was 3%, the mass fraction of Mg was 0.5%, and the stainless steel fiber content was 6%. Then, the Al-xSi-3Cu-0.5Mg-ySSF composite powder was annealed in a vacuum tube furnace at a temperature of 300℃.

[0184] The comparative example has a relatively large amount of stainless steel fiber powder added.

[0185] Comparative Example 10: The difference between Comparative Example 10 and Example 3 lies only in step S6:

[0186] S6. Sinter the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod to obtain an aluminum-based composite material. The sintering process of the extrusion rod is as follows: the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod is placed in a vacuum tube furnace, and pre-sintered at 350°C with nitrogen as the protective atmosphere at a heating rate of 3.5°C / min to remove residual lubricant oil stains on the alloy surface. Then, it is heated to 480°C at 5°C / min and held for 2 hours, followed by furnace cooling.

[0187] The sintering temperature of this comparative example is relatively low.

[0188] Comparative Example 11: The difference between Comparative Example 11 and Example 3 lies only in step S6:

[0189] S6. Sinter the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod to obtain an aluminum-based composite material. The sintering process of the extrusion rod is as follows: the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod is placed in a vacuum tube furnace, and pre-sintered at 350°C with nitrogen as the protective atmosphere at a heating rate of 3.5°C / min to remove residual lubricant oil stains on the alloy surface. Then, it is heated to 550°C at 5°C / min and held for 2 hours, followed by furnace cooling.

[0190] like Figure 5 As shown in (b), this is a physical image of the aluminum-based composite material after sintering in this comparative example. It can be clearly seen that the surface quality is poor.

[0191] like Figure 11 (b) shows a metallographic micrograph of the aluminum-based composite material obtained after sintering in step S6. The sintering temperature was too high, and the over-burning problem on the metallographic surface can be clearly seen.

[0192] Comparative Example 12: The only difference between Comparative Example 12 and Example 3 is step S1.

[0193] S1. Al-Si-Mg pre-alloyed powder without stainless steel short fibers and Cu powder are mixed in a powder mixer for 6 hours to prepare Al-10Si-3Cu-Mg composite powder.

[0194] Since there is no need to prepare stainless steel fiber powder, the pre-alloyed powder and Cu powder can be mixed evenly using a powder mixer.

[0195] like Figure 8 As shown, compared to the performance of the best-doped aluminum matrix composite, the tensile strength and microhardness of the undoped aluminum matrix composite are 350 MPa and 65 HV, respectively, which are lower than those of the best-doped aluminum matrix composite (450 MPa and 110 HV).

[0196] Comparative Example 13: The only difference between this comparative example and Example 3 is step S5.

[0197] S5. The Al-xSi-3Cu-0.5Mg-ySSF preform, after being heated and kept at a certain temperature in step S4, is placed into an extruder for extrusion to obtain an Al-xSi-3Cu-0.5Mg-ySSF composite material extrusion bar. The extrusion speed is 2.5 mm / s, and the rotation speed of the variable diameter die 6 is 0 r / min.

[0198] The silicon particles in aluminum matrix composites that have not undergone rotary extrusion are larger than those in rotary extrusion composites, with a density of 95%, which is smaller than the 98% of those in rotary extrusion composites. The tensile strength is only 300 MPa, which is smaller than the tensile strength of 450 MPa of aluminum matrix composites after rotary extrusion.

[0199] like Figure 13 The image shows a metallographic micrograph of the aluminum-based composite material prepared in this embodiment. It is clearly visible that during the extrusion process, if the variable-diameter die is not rotated, voids appear in the metallographic microstructure. This is mainly because the deformation from direct extrusion alone is insufficient to completely break down the oxide film on the powder surface, and the porosity obtained in powder metallurgy is difficult to completely eliminate, resulting in poor density of the aluminum-based composite material. However, the dual deformation of direct extrusion and rotary extrusion, through the synergistic effect of multi-directional stress and shear force, more efficiently eliminates porosity, which is the fundamental reason why its density is superior to that of traditional direct extrusion.

[0200] like Figure 7 As shown, the line graphs of the tensile strength of aluminum-based composite materials prepared in Examples 1, 3, 4, Comparative Example 1, and Comparative Example 2 clearly show that the tensile strength of the aluminum-based composite materials prepared after ball milling for 1.5-2 hours and 5-8 hours is significantly lower than that of the aluminum-based composite materials prepared after ball milling for 3-5 hours.

[0201] like Figure 8 The figures show the microhardness and tensile strength of the aluminum-based composite materials prepared in Examples 1, 2, 3, Comparative Example 9, and Comparative Example 12. It is evident that the limiting hardness and tensile strength of the aluminum-based composite materials prepared with stainless steel fiber additions in the ranges of 0-1.5% and 4.5-6% are significantly lower than those prepared with stainless steel fiber additions in the range of 1.5-4.5%.

[0202] Figure 9 The bar chart shown is a tensile strength histogram of aluminum-based composite materials prepared in Examples 1, 3, 10, and 11. It can be clearly seen that the tensile strength of the aluminum-based composite materials at sintering temperatures of 500℃ and 520℃ is significantly higher than that at 480℃ and 550℃.

[0203] The density, tensile strength at room temperature, tensile strength at 300℃, and microhardness of the aluminum-based composite materials prepared in Examples 1-6 and Comparative Examples 1-12 were tested and summarized in the table below.

[0204] Performance test table for aluminum-based composite materials

[0205]

[0206] The test results in the table above show that, at 300°C, the aluminum-based composite material prepared by adding stainless steel fiber powder in Example 3, compared to the aluminum-based composite material prepared without stainless steel fiber powder in Comparative Example 12, exhibits significant improvements in hardness, tensile strength, and high-temperature heat resistance. Stainless steel fiber powder typically has higher strength and modulus than the aluminum matrix, maintaining high mechanical properties even at high temperatures. When the composite material is subjected to load, the fibers transfer stress through the interface, sharing the load on the matrix and delaying plastic deformation. As a hard phase, the fiber powder hinders dislocation slip and grain boundary migration in the aluminum matrix at high temperatures, thereby improving creep resistance. The aluminum matrix softens easily above 300°C, while the recrystallization temperature and melting point of stainless steel fiber powder are higher, providing high-temperature support for the composite material. With the increase of stainless steel fibers, the performance of the aluminum-based composite material at high temperatures also increases. Therefore, adding stainless steel fiber powder can effectively improve the performance of aluminum-based composite materials at high temperatures.

[0207] The optimal fiber-added aluminum matrix composite material was prepared using the best rotary extrusion process, fiber powder ratio, and sintering temperature. The material achieved a hardness of 120 HV and a tensile strength of 450 MPa, which is much higher than the 65 HV and 350 MPa of Al-Si-Cu-Mg material without stainless steel fiber powder, and even higher than the tensile strength of the composite material of this composition prepared by the traditional casting method (nearly 200 MPa).

[0208] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing an aluminum-based composite material, characterized in that, Includes the following steps: S1. Al-Si-Mg pre-alloyed powder, Cu powder, and stainless steel short fibers are placed in a planetary ball mill for ball milling to prepare Al-xSi-3Cu-0.5Mg-ySSF composite powder; x is the mass fraction of Si in the composite powder, and x ranges from 5 to 20. y represents the mass fraction of stainless steel fiber in the composite powder, and y ranges from 1.5 to 4.

5. S2. The Al-xSi-3Cu-0.5Mg-ySSF composite powder and the first lubricant are mixed in a powder mixer; S3. The second lubricant is applied to the inner wall of the pressing mold, and the Al-xSi-3Cu-0.5Mg-ySSF composite powder mixed with the first lubricant is placed into the pressing mold and pressed to obtain the Al-xSi-3Cu-0.5Mg-ySSF compact; S4. Place the Al-xSi-3Cu-0.5Mg-ySSF compact into a box furnace and hold it at 280-320℃ for 2 hours; S5. The Al-xSi-3Cu-0.5Mg-ySSF preform after being heated and kept warm in step S4 is placed into an extruder for extrusion to obtain an Al-xSi-3Cu-0.5Mg-ySSF composite material extrusion bar; S6. Sinter the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod to obtain an aluminum-based composite material.

2. The method for preparing an aluminum-based composite material according to claim 1, characterized in that, In step S1, the planetary ball mill rotates at a speed of 190-200 r / min, the milling time is 2-6 h, and the ball-to-material ratio is 3:

2.

3. The method for preparing an aluminum-based composite material according to claim 1, characterized in that, In step S1, there is also The process includes the following steps: placing the Al-xSi-3Cu-0.5Mg-ySSF composite powder into a vacuum tube furnace for annealing at a temperature of 300~350℃.

4. The method for preparing an aluminum-based composite material according to claim 1, characterized in that, In step S2, the first lubricant is prepared by mixing ethylene glycol bis-stearamide and polyethylene glycol in a 1:2 ratio. The mass of the first lubricant accounts for 0.6% to 0.8% of the total mass of the alloy powder. The first lubricant is mixed with Al-xSi-3Cu-0.5Mg-ySSF composite powder in a powder mixer for 6 to 8 hours.

5. The method for preparing an aluminum-based composite material according to claim 1, characterized in that, The pressing pressure in step S3 is 300~600MPa.

6. The method for preparing an aluminum-based composite material according to claim 1, characterized in that, In step S3, the second lubricant is prepared by mixing a 5% PEG solution with mineral oil at a volume ratio of 3:1 and stirring until homogeneous.

7. The method for preparing an aluminum-based composite material according to claim 1, characterized in that, The extrusion press includes a hydraulic press, a three-phase asynchronous motor, an extrusion rod (1), an extrusion rod fixing plate (2), an upper base plate (3), a die sleeve (4), an extrusion cylinder (5), a variable diameter die (6), a lower base plate (7), a thrust rolling bearing (8), a transmission shaft (9), and a bushing (10). The extrusion cylinder (5) has a cylindrical structure and a cylindrical through hole for the extrusion rod (1) to pass through at its axial position; The variable diameter die (6) is a cylindrical structure with a cylindrical through hole at its axial position. One end of the variable diameter die (6) abuts against one end of the extrusion cylinder (5). The cylindrical through hole of the extrusion cylinder (5) and the axial center of the variable diameter die (6) are on the same straight line. A tapered angle (11) is provided on the inner wall of the cylindrical through hole in the variable diameter die (6) near the extrusion cylinder (5). The angle of the tapered angle (11) is 30~45°. One end of the drive shaft (9) is connected to the variable diameter die (6) via a cross coupling, and the other end of the conventional shaft is connected to a three-phase asynchronous motor; The die sleeve (4) is located on the outside of the extrusion cylinder (5) and the variable diameter die (6). The extrusion cylinder (5) is fixedly connected to the die sleeve (4). The lower base plate (7) is screwed to the end of the die sleeve (4). A through hole for the transmission shaft (9) to pass through is provided in the middle of the lower base plate (7). The transmission shaft (9) passes through the lower base plate (7) and connects to the variable diameter die (6). A thrust rolling bearing (8) is provided between the end of the variable diameter die (6) away from the extrusion cylinder (5) and the lower base plate (7). The extrusion rod (1) is a cylindrical rod structure, and one end of the extrusion rod (1) is provided with an upper base plate (3), which is connected to the hydraulic press.

8. The method for preparing an aluminum-based composite material according to claim 7, characterized in that, In step S5, the extrusion speed is 2~2.5 mm / s, and the rotation speed of the variable diameter die (6) is 50~66 r / min.

9. The method for preparing an aluminum-based composite material according to claim 1, characterized in that, The sintering process of the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod in step S6 is as follows: the Al-xSi-3Cu-0.5Mg-ySSF composite extrusion rod is placed in a vacuum tube furnace, and pre-sintered at 300~350℃ with nitrogen as the protective atmosphere at a heating rate of 3.5℃ / min. Then, it is heated to 500~525℃ at 5℃ / min and held for 2 hours, and then cooled with the furnace.

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