Vacuum melting and die-casting integrated forming method for aluminum-lithium alloy unmanned aerial vehicle structural member

Abstract

This invention relates to the field of drone manufacturing technology, and provides a vacuum melting and die-casting method for integral molding of aluminum-lithium alloy drone structural components. The method includes: S1: placing aluminum-lithium alloy raw materials in a melting crucible; S2: preheating the die-casting mold; S3: spraying a release agent onto the cavity surface of the die-casting mold, blowing and drying it, and then closing the mold; S4: evacuating the melting chamber, barrel, and mold to achieve a preset vacuum environment; S5: heating the melting crucible to melt the raw materials into a melt and holding it at that temperature; S6: pouring the melt into a barrel; S7: injecting the melt from the barrel into the cavity under the action of an injection rod; S8: holding the melt under pressure and solidifying it; S9: opening the mold to obtain the drone structural component. This invention solves the problems of difficulty in controlling the composition of aluminum-lithium alloy and difficulty in achieving precise molding in existing processes.

Description

Technical Field

[0001] This invention relates to the field of drone manufacturing technology, and more specifically, to a method for integral molding of aluminum-lithium alloy drone structural components by vacuum melting and die casting. Background Technology

[0002] Unlike consumer drones, industrial drones typically face stringent requirements such as high payload, long flight time, and operation in complex weather conditions. "Payload" and "flight time" have become core performance indicators for drones. Given the limited potential for breakthroughs in battery energy density in the short term, extreme lightweight design of fuselage components (such as arms, central frame, fuselage mid-frame, motor mounts, and landing gear) is the most direct and effective way to improve the overall performance of drones.

[0003] Currently, the load-bearing structural components of high-performance drones mainly utilize carbon fiber composites or high-strength aluminum alloys (such as 7-series aerospace aluminum). While carbon fiber composites possess extremely high specific strength, their anisotropic characteristics make the design and processing of connection points extremely difficult. Furthermore, when molding complex, integrated irregular structures with internal heat dissipation channels or reinforcing ribs, mold costs are high, production cycles are long, and the materials are difficult to recycle after disposal, which contradicts the industry trend of green manufacturing. Traditional aluminum alloys, although technologically mature and relatively inexpensive, typically have a density of 2.7–2.8 g / cm³. 3 Between these, the specific stiffness (specific modulus) is relatively limited. In today's pursuit of extreme weight reduction, the weight reduction potential of traditional aluminum alloys has approached its physical limit, making it difficult to meet the design requirements of the next generation of long-endurance UAVs.

[0004] Aluminum-lithium alloy (Al-Li) is hailed as the "crown jewel" of aerospace metal materials. Lithium (Li), as the lightest metallic element, reduces the alloy density by approximately 3% and increases the elastic modulus (stiffness) by approximately 6% for every 1 wt% of lithium added to an aluminum alloy. For drones, using aluminum-lithium alloy instead of traditional aluminum alloy can not only significantly reduce the weight of the fuselage but also greatly improve the bending stiffness of cantilever beam structures (such as arms), effectively suppressing high-frequency vibrations during flight, thereby improving the stability of captured images and the precision of flight control.

[0005] Despite the excellent performance of aluminum-lithium alloys, their large-scale manufacturing of structural components still faces significant technological challenges, limiting their widespread application: First, material utilization is low. Currently, aluminum-lithium alloys are mainly supplied in the form of plates or forgings. Manufacturing complex UAV structural components requires extensive CNC machining, resulting in severe material waste and high component costs. Second, there is the issue of "lithium burn-off" and compositional instability. Lithium is chemically extremely reactive, and in traditional open or semi-open melting environments, it readily oxidizes and burns, causing the alloy composition to deviate from design values ​​and significantly reducing performance. Third, aluminum-lithium alloy melts have extremely high solubility for hydrogen (commonly known as "hydrogen-absorbing sponges"). During the open-feed transfer process of traditional die casting, the melt comes into contact with moisture in the air, easily absorbing hydrogen and forming diffuse pinholes and hydrogen embrittlement within the casting. For UAV structural components subjected to alternating loads (vibration) over long periods, these microscopic defects are fatal fatigue crack initiation points, easily leading to arm fracture and aircraft failure.

[0006] In summary, existing traditional smelting-injection separation processes or machining processes cannot perfectly resolve the contradiction between the "difficulty in controlling the composition" and the "difficulty in achieving dense molding" of aluminum-lithium alloys. Therefore, to solve these problems, it is urgent to develop a vacuum smelting and die-casting integrated molding method for aluminum-lithium alloy UAV structural components that can isolate air from the smelting source, lock in lithium elements, and prevent hydrogen absorption. Summary of the Invention

[0007] In view of the above problems, the purpose of this invention is to provide a vacuum melting and die casting method for aluminum-lithium alloy UAV structural components, so as to solve the problems of "difficulty in controlling the composition" and "difficulty in achieving dense forming" of aluminum-lithium alloys in existing traditional melting-injection separation processes or machining processes; thereby achieving near-net-shape forming of complex aluminum-lithium alloy structural components with low cost and high performance.

[0008] In a first aspect, the present invention provides an integrated vacuum melting and die-casting equipment, comprising a melting chamber, a melting crucible and a tilting drive mechanism disposed within the melting chamber, a die-casting mold, a material cylinder, an injection rod, a vacuum pump assembly, and a mold temperature controller, wherein... One end of the barrel is connected to the cavity of the die-casting mold, and the other end passes through the melting chamber and is connected to the injection rod; The smelting crucible is mounted on the tilting drive mechanism, which is used to drive the smelting crucible to tilt so as to pour the molten material formed by smelting into the material cylinder; The injection rod is used to inject the molten material in the barrel into the cavity of the die-casting mold; The die-casting mold is used to die-cast the molten material in the cavity; The vacuum pump unit is connected to the melting chamber and the die-casting mold, and is used to draw a vacuum. The mold temperature controller is connected to the die-casting mold and is used to preheat the die-casting mold.

[0009] Alternatively, the melting crucible may be a silicon carbide crucible, a high-purity graphite crucible, a magnesium oxide crucible, or a steel crucible with a ceramic barrier coating sprayed on its inner wall.

[0010] Secondly, this invention provides a vacuum melting and die-casting integrated molding method for aluminum-lithium alloy drone structural components. The method utilizes the aforementioned vacuum melting and die-casting integrated equipment to prepare the aluminum-lithium alloy drone structural components, and includes: S1: Place the aluminum-lithium alloy raw material in a melting crucible, wherein the aluminum-lithium alloy raw material, by mass percentage, has the following chemical composition: Li: 1.0-3.0%; Cu: 1.0-4.5%; Mg: 0.5-2.0%; Zr: 0.05-0.2%; the balance being Al and unavoidable impurities; S2: Before closing the mold, the die-casting mold is preheated to a preset temperature. S3: After the die-casting mold reaches the preset temperature, spray a release agent onto the cavity surface of the die-casting mold, blow it dry, and then close the die-casting mold. S4: Evacuate the melting chamber, the barrel, and the die-casting mold to bring the integrated vacuum melting and die-casting equipment to a preset vacuum environment; S5: Under the vacuum environment, the melting crucible is heated to melt the aluminum-lithium alloy raw material in the melting crucible into an aluminum-lithium alloy melt and keep it at the temperature; S6: Pour the aluminum-lithium alloy melt into the barrel; S7: Under the action of the injection rod, the aluminum-lithium alloy melt in the barrel is injected into the cavity of the die-casting mold; S8: After the aluminum-lithium alloy melt fills the cavity, the aluminum-lithium alloy melt is solidified under pressure. S9: After the pressure holding and solidification are completed, the mold is opened to obtain the aluminum-lithium alloy UAV structural parts.

[0011] Alternatively, the aluminum-lithium alloy drone structural components may include any one of the following: drone arms, fuselage mid-frame, fuselage frame, motor mount, and landing gear. A reinforcing rib groove is provided in the cavity at a position corresponding to the aluminum-lithium alloy drone structural component. The reinforcing rib groove is used to form an irregular thin-walled structure of internal reinforcing ribs or heat dissipation channels of the aluminum-lithium alloy drone structural component.

[0012] Alternatively, in S2, the preset temperature is 200–300 °C.

[0013] Alternatively, in S4, the preset vacuum environment is a high vacuum state with a pressure lower than 50 Pa. In S5, the melting temperature of the aluminum-lithium alloy is 720–780 °C.

[0014] Alternatively, in S6, the pouring rate of the melting crucible is 10–80 ° / s.

[0015] Alternatively, in S7, the injection rate of the injection rod is 3 to 7 m / s; In S8, the pressure for holding the aluminum-lithium alloy melt is 60-120 MPa, and the holding time is 2-15 s.

[0016] Alternatively, the method may further include: S10: subjecting the obtained aluminum-lithium alloy UAV structural component to T6 heat treatment; wherein, The aluminum-lithium alloy UAV structural component is heated to 480-530 ℃ and held for 2-8 hours for solution treatment, followed by water quenching. The aluminum-lithium alloy UAV structural components, after water quenching and cooling, are heated to 150-180℃ and held for 6-24 hours for artificial aging treatment.

[0017] In addition, an optional approach is that the method further includes: S11: performing surface anodizing or micro-arc oxidation treatment on the aluminum-lithium alloy drone structural parts after T6 heat treatment, so that a corrosion-resistant layer is formed on the surface of the aluminum-lithium alloy drone structural parts.

[0018] As can be seen from the above technical solution, the vacuum melting and die casting integrated molding method for aluminum-lithium alloy UAV structural parts provided by the present invention has the following advantages compared with the prior art: 1) This invention precisely controls the composition of raw materials and suppresses lithium element burn-off: This invention utilizes the full-chain vacuum closed-loop environment of the vacuum melting and die-casting integrated equipment, thereby solving the problem that lithium element is easily oxidized and volatilized (burn-off) in the traditional open melting of aluminum-lithium alloys; thus ensuring that the lithium content in the UAV structural components is consistent with the design value, thereby ensuring that the density and stiffness of the UAV structural components reach the theoretical optimal value.

[0019] 2) This invention eliminates hydrogen absorption and removes the risk of fatigue fracture: By using vacuum melting and closed conveying, the path of contact between the aluminum-lithium alloy melt and moisture in the air is cut off at the source, effectively avoiding the phenomenon of "hydrogen absorption" by the melt. The resulting UAV structural components are free of pinholes and pores, significantly improving the fatigue resistance of the components and thus solving the problem of UAV arm fracture under long-term high-frequency vibration.

[0020] 3) The aluminum-lithium alloy UAV structure of the present invention has a complex thin-walled structure: combined with vacuum-based temperature drop-free conveying and high-pressure feeding process (60~120 MPa), the present invention can produce a complex fuselage frame and slender arms with internal reinforcing ribs or heat dissipation channels, and with the T6 heat treatment process, the structural components have obtained excellent specific stiffness and specific strength.

[0021] 4) The aluminum-lithium alloy drone structural parts prepared by this invention have high-end surface treatment capabilities: thanks to the extremely low porosity and dense microstructure, the aluminum-lithium alloy drone structural parts prepared by this invention can be directly subjected to anodizing or micro-arc oxidation treatment, which not only improves corrosion resistance, but also meets the stringent requirements of industrial drones for appearance and texture.

[0022] To achieve the foregoing and related objectives, one or more aspects of the invention include the features that will be described in detail below. The following description and accompanying drawings illustrate certain exemplary aspects of the invention. However, these aspects indicate only a few of the various ways in which the principles of the invention can be used. Furthermore, the invention is intended to encompass all such aspects and their equivalents. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of an integrated vacuum melting and die-casting equipment according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the aluminum-lithium alloy drone fuselage frame prepared in Example 1; Figure 3 This is a schematic diagram of the structure of the aluminum-lithium alloy drone shell prepared in Example 2; Figure 4 This is a schematic diagram of the vacuum melting and die casting integrated molding method for aluminum-lithium alloy UAV structural components according to an embodiment of the present invention.

[0025] The attached figures are labeled as follows: 1. Melting chamber, 2. Melting crucible, 3. Injection rod, 4. Die casting mold, 5. Material cylinder. Detailed Implementation

[0026] In the following description, numerous specific details are set forth for illustrative purposes and to provide a thorough understanding of one or more embodiments. However, it will be apparent that these embodiments may also be implemented without these specific details. In other instances, well-known structures and devices are shown in block diagram form for ease of description of one or more embodiments.

[0027] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0028] This invention can be modified and has various embodiments, with specific embodiments illustrated in the accompanying drawings. However, this invention is not limited to this particular implementation and all modifications, equivalents, and substitutions falling within the spirit and technical scope of this invention are to be understood as included.

[0029] Ordinal terms such as "first," "second," etc., may be used to describe various constituent elements, but the constituent elements are not limited to these terms. The terms are used only to distinguish one constituent element from another. For example, without departing from the scope of the claims of this invention, a second constituent element may be named a first constituent element, and similarly, a first constituent element may be named a second constituent element. Terms and / or include combinations of multiple associated items or one of multiple associated items.

[0030] It should be understood that when referring to a constituent element being "connected" or "in contact" with other constituent elements, this includes not only cases where it is directly connected or in contact with other constituent elements, but also cases where other constituent elements exist between them. Conversely, when referring to a constituent element being "directly connected" or "directly in contact" with other constituent elements, it should be understood that no other constituent elements exist between them.

[0031] To address the aforementioned problems in existing traditional melting-injection separation processes or machining processes where it is difficult to simultaneously achieve "difficulty in controlling the composition" and "difficulty in achieving dense forming" of aluminum-lithium alloys, this invention proposes a vacuum melting and die-casting integrated forming method for aluminum-lithium alloy UAV structural components. UAV structural components formed using this method exhibit precise composition, no internal porosity, high specific stiffness, and excellent fatigue resistance.

[0032] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0033] To illustrate the structure of the integrated vacuum melting and die casting equipment provided by this invention Figure 1 A schematic diagram of an integrated vacuum melting and die-casting equipment according to an embodiment of the present invention is shown.

[0034] like Figure 1 As shown, this invention provides an integrated vacuum melting and die-casting equipment, including a melting chamber 1, a melting crucible 2 disposed in the melting chamber 1, a tilting drive mechanism, a die-casting mold 4, a material cylinder 5, and an injection rod 3. One end of the material cylinder 5 is connected to the cavity of the die-casting mold 4 (hereinafter referred to as the cavity), and the other end passes through the melting chamber 1 and is connected to the injection rod 3. The melting crucible is mounted on the tilting drive mechanism, which drives the melting crucible to tilt and pour the melt formed by melting into the material cylinder 5. Under the action of the injection rod 3, the material cylinder 5 injects the melt into the cavity. The die-casting mold 4 is used to perform die-casting processing on the melt in the cavity.

[0035] Furthermore, the integrated vacuum melting and die casting equipment of the present invention also includes a vacuum pump unit and a mold temperature controller. The mold temperature controller is used to preheat the die casting mold; the vacuum pump unit is used to evacuate the melting chamber, the barrel, and the die casting mold. The structural components of the entire equipment work together to achieve a vacuum throughout the entire process from melting and injection to solidification.

[0036] The melting crucible is made of silicon carbide (SiC), high-purity graphite, magnesium oxide, or steel with a boron nitride (BN) coating on its inner wall.

[0037] To illustrate the vacuum melting and die-casting integrated molding method for aluminum-lithium alloy UAV structural components provided by this invention, such as... Figure 4 As shown, the present invention provides a vacuum melting and die-casting integrated molding method for aluminum-lithium alloy drone structural parts. The method uses the aforementioned vacuum melting and die-casting integrated equipment to prepare aluminum-lithium alloy drone structural parts, and includes: S1: Place the aluminum-lithium alloy raw material in a melting crucible, wherein the aluminum-lithium alloy raw material, by mass percentage, has the following chemical composition: Li: 1.0-3.0%; Cu: 1.0-4.5%; Mg: 0.5-2.0%; Zr: 0.05-0.2%; the balance being Al and unavoidable impurities; S2: Before closing the mold, the die-casting mold is preheated to a preset temperature. S3: After the die-casting mold reaches the preset temperature, spray a release agent onto the cavity surface of the die-casting mold, blow it dry, and then close the die-casting mold. S4: Evacuate the melting chamber, the barrel, and the die-casting mold to bring the integrated vacuum melting and die-casting equipment to a preset vacuum environment; S5: Under the vacuum environment, the melting crucible is heated to melt the aluminum-lithium alloy raw material in the melting crucible into an aluminum-lithium alloy melt and keep it at the temperature; S6: Pour the aluminum-lithium alloy melt into the barrel; S7: Under the action of the injection rod, the aluminum-lithium alloy melt in the barrel is injected into the cavity of the die-casting mold; S8: After the aluminum-lithium alloy melt fills the cavity, the aluminum-lithium alloy melt is solidified under pressure. S9: After the pressure holding and solidification are completed, the mold is opened to obtain the aluminum-lithium alloy UAV structural parts.

[0038] In embodiments of this invention, the end-to-end vacuum closed-loop environment of an integrated vacuum melting and die-casting equipment solves the problem of lithium easily oxidizing and volatilizing (burning off) in traditional open melting of aluminum-lithium alloys. This ensures that the lithium content in the UAV structural components matches the design value, thereby guaranteeing that the density and stiffness of the UAV structural components reach the theoretically optimal values. Vacuum melting and closed-loop conveying cut off the path of contact between the aluminum-lithium alloy melt and moisture in the air, effectively avoiding the phenomenon of "hydrogen absorption" by the melt. The resulting UAV structural components are free of pinholes and pores, significantly improving the fatigue resistance of the components and solving the problem of arm fracture easily occurring under prolonged high-frequency vibration in UAVs.

[0039] In this invention, the aluminum-lithium alloy drone structural component includes any one of a drone arm, fuselage mid-frame, fuselage frame, motor mount, and landing gear. Reinforcing rib slots are provided in the cavity at positions corresponding to the aluminum-lithium alloy drone structural component. These reinforcing rib slots are used to form the irregular thin-walled structure of the aluminum-lithium alloy drone structural component, which consists of internal reinforcing ribs or heat dissipation channels. In embodiments of this invention, by combining vacuum-based temperature-drop-free conveying and high-pressure feeding processes (60~120 MPa), a complex drone fuselage mid-frame and slender arms with internal reinforcing ribs or heat dissipation channels are fabricated. Furthermore, the T6 heat treatment process gives the structural component excellent specific stiffness and specific strength.

[0040] In S2, to reduce the temperature difference between the melt and the mold, delay early solidification during thin-walled filling, improve surface finish, and reduce filling resistance, the preset temperature is set to 200–300 °C. In S4, to prevent secondary oxidation inclusions in the aluminum-lithium alloy at high-temperature molten state, thereby forming other oxides detrimental to alloy properties, the preset vacuum environment is set to a high vacuum state with a pressure below 50 Pa. In S5, the melting temperature of the aluminum-lithium alloy is 720–780 °C. In S6, to maintain the continuity and stability of melt delivery, reduce heat loss, and prevent liquid splashing and entrainment of residual gas in the vacuum chamber due to excessively rapid pouring, the pouring rate of the melting crucible is set to 10–80 ° / s. In S7, to ensure that the melt completes filling before solidification, the injection rate of the injection rod is set to 3–7. m / s; In S8, in order to eliminate internal shrinkage cavities, improve dimensional accuracy, and increase the density of the casting, the holding pressure of the aluminum-lithium alloy melt is set to 60-120 MPa, and the holding time is 2-15 s.

[0041] In addition, the method further includes: S10: performing T6 heat treatment on the obtained aluminum-lithium alloy UAV structural parts; the specific process includes: heating the aluminum-lithium alloy UAV structural parts to 480-530 ℃ and holding for 2-8 hours for solution treatment, and then water quenching; heating the water-quenched aluminum-lithium alloy UAV structural parts to 150-180 ℃ and holding for 6-24 hours for artificial aging treatment.

[0042] Furthermore, the method also includes: S11: performing surface anodizing or micro-arc oxidation treatment on the aluminum-lithium alloy drone structural parts after T6 heat treatment, so that a corrosion-resistant layer is formed on the surface of the aluminum-lithium alloy drone structural parts. In other words, the surface of the treated aluminum-lithium alloy drone structural parts is corrosion-resistant and free of porosity defects. In this invention, thanks to its extremely low porosity and dense microstructure, the aluminum-lithium alloy drone structural parts prepared by this invention can be directly subjected to anodizing or micro-arc oxidation treatment, which not only improves corrosion resistance but also meets the stringent requirements for appearance and texture of industrial-grade drones.

[0043] To illustrate the effects of this invention in detail, specific embodiments are provided below. Unless otherwise specified, the raw materials used in the embodiments of this invention are all purchased through commercial channels, i.e., industrial-grade raw materials.

[0044] Example 1

[0045] This embodiment provides a die-casting method for an integrated fuselage frame of an aluminum-lithium alloy drone. For example... Figure 2 As shown, the frame is a complex porous irregular structure that integrates a motor mounting base, a battery compartment bearing surface, and a blade protection ring interface, making it a typical load-bearing structural component.

[0046] S1 Raw Material Preparation: A high-modulus aluminum-lithium alloy was selected. The chemical composition used in this example, by mass percentage, is: Li: 2.0%, Cu: 2.5%, Mg: 1.0%, Zr: 0.12%, with the balance being Al. The raw materials in the above proportions were weighed and placed in a high-purity graphite melting crucible for integrated vacuum melting and die casting.

[0047] S2 Mold Preheating: Before mold closing, the mold temperature controller is started to heat the die-casting mold. In this embodiment, the working temperature of the die-casting mold is preset and stabilized at 280 ℃.

[0048] S3 Mold Treatment: After the die-casting mold reaches the preset temperature of 280℃, a water-based release agent is evenly sprayed onto the cavity surface of the die-casting mold using an automatic spray nozzle. After spraying, the cavity is immediately dried by powerful blowing with compressed air for about 5~10 seconds until it is confirmed that there is no residual moisture on the cavity surface. Then the die-casting mold is closed.

[0049] S4 System Vacuuming: Start the vacuum pump unit to simultaneously evacuate the melting chamber containing the melting crucible, the material cylinder, and the die-casting mold cavity connected to the material cylinder. Evacuation continues until the gas pressure in the system reaches 20 Pa.

[0050] S5 Vacuum Melting: The melting crucible is heated under a vacuum of 20 Pa. In this embodiment, the melting temperature is set to 760 °C, and the raw materials are melted into a uniform aluminum-lithium alloy melt. The melt is held at this temperature for 15 minutes to facilitate degassing and homogenization of the composition.

[0051] S6 Melt Transfer: While maintaining a constant vacuum environment of 20 Pa, the melting crucible is tilted. In this embodiment, the tilting rate of the crucible is controlled at 50 ° / s, and the metered aluminum-lithium alloy melt is poured smoothly and without turbulence into the barrel.

[0052] S7 Injection Molding: After the aluminum-lithium alloy melt enters the barrel, the injection rod of the die-casting machine is immediately activated. For the long flow channel structure of the machine arm, the injection rate (high-speed section) is set to 5.0 m / s in this embodiment to ensure smooth filling.

[0053] S8 Pressure Holding and Solidification: After the aluminum-lithium alloy melt has been completely filled, a pressure boosting process is immediately applied. In this embodiment, the cooling and solidification forming pressure is set to 90 MPa, and the holding time is 5 s.

[0054] S9 Mold Opening and Part Removal: After cooling and solidification, the integrated aluminum-lithium alloy drone fuselage frame structure is removed from the mold.

[0055] S10 Heat Treatment: The integrated fuselage frame structural component removed from the mold undergoes T6 heat treatment. The casting is heated to 520 ℃ and held for 4 hours for solution treatment, followed by water quenching and cooling; then the casting is heated to 160 ℃ and held for 12 hours for artificial aging treatment.

[0056] S11 Surface Treatment: The integrated fuselage frame structure after heat treatment is cleaned and subjected to hard anodizing to form a wear-resistant protective film layer on the surface.

[0057] The integrated aluminum-lithium alloy UAV fuselage frame prepared in Example 1 was subjected to performance testing and appearance inspection. The results are as follows: Appearance quality: The complex reinforcing ribs and motor mount interface are fully filled and there is no cold shut.

[0058] Dimensional accuracy: The overall flatness of the frame is excellent, and the coplanarity error of the four motor mounting planes is less than 0.05 mm.

[0059] Mechanical properties: Tests show that the integrated fuselage frame has a tensile strength of 520 MPa, a yield strength of 460 MPa, and an elastic modulus (stiffness) of 79 GPa. Compared to a 6061 aluminum alloy arm of the same specification (modulus of approximately 69 GPa), the stiffness of this embodiment is increased by approximately 14%, which can effectively suppress flight flutter.

[0060] Composition consistency: Spectroscopic analysis showed that the lithium (Li) content in the casting was 1.98%, which is almost consistent with the formula value (2.0%), proving that the vacuum process effectively suppressed the loss of lithium.

[0061] Post-treatment performance: After S11 anodizing, a uniform black oxide film is formed on the surface with strong film adhesion and no "white spot" defects caused by pores.

[0062] Example 2

[0063] This embodiment provides a method for preparing a streamlined upper shell for an aluminum-lithium alloy unmanned aerial vehicle (UAV). For example... Figure 3 As shown, the shell is a thin-walled structure with a large curvature, and the thinnest part of the wall is only 0.6 mm. It mainly serves the functions of aerodynamic rectification, heat dissipation, and electromagnetic shielding. The method includes the following steps S1 to S11.

[0064] S1 Raw Material Preparation: Low-density aluminum-lithium alloy was selected as the raw material. The chemical composition used in this embodiment, by mass percentage, is: Li: 2.8%, Cu: 1.5%, Mg: 1.5%, Zr: 0.1%, with the balance being Al. The raw materials in the above proportions were weighed and placed in a steel crucible with a boron nitride coating on the inner wall of the integrated equipment.

[0065] S2 Mold Preheating: Before mold closing, the mold temperature controller is started to heat the die-casting mold. Considering the large projected area of ​​the machine body frame, this embodiment presets and stabilizes the working temperature of the die-casting mold at 240 ℃ to ensure the fluidity of the melt in the complex flow channel.

[0066] S3 Mold Treatment: After the die-casting mold reaches the preset temperature of 240℃, a water-based release agent is evenly sprayed onto the cavity surface at 240℃ using an automatic spray nozzle. After spraying, the cavity is immediately dried by powerful blowing with compressed air for about 5~10 seconds until it is confirmed that there is no residual moisture on the cavity surface, and then the mold is closed.

[0067] S4 System Vacuuming: Start the vacuum pump unit to simultaneously evacuate the melting chamber containing the melting crucible, the material cylinder, and the die-casting mold cavity connected to the material cylinder. Evacuation continues until the gas pressure in the system reaches 10 Pa.

[0068] S5 Vacuum Melting: The melting crucible is heated under a vacuum of 10 Pa. In this embodiment, the melting temperature is set to 740 °C, and the raw materials are melted into a uniform aluminum-lithium alloy melt. The melt is held at this temperature for 10 min to fully remove the gas from the melt and homogenize the composition.

[0069] S6: Melt Transfer: While maintaining a constant vacuum environment of 10 Pa, the melting crucible is tilted. In this embodiment, the tilting rate of the crucible is controlled at 60 ° / s, and the metered aluminum-lithium alloy melt is smoothly and without turbulence poured into the barrel through a closed flow channel, with no temperature drop throughout the process.

[0070] S7 Injection Molding: After the aluminum-lithium alloy melt enters the barrel, the injection rod of the die-casting machine is immediately started. In view of the complex thin-walled characteristics of the heat sink in the middle frame of the machine body, this embodiment increases the injection rate (high-speed section) to 6.5 m / s, and uses the extremely high filling speed to force all heat sink positions to be filled before the melt solidifies.

[0071] S8 Pressure Holding and Solidification: After the aluminum-lithium alloy melt is filled, a pressure boosting process is immediately applied. In this embodiment, the cooling and solidification molding pressure is set to 110 MPa, and the holding time is 8 s. High pressure is used to compensate for shrinkage and eliminate porosity.

[0072] S9 Mold Opening and Part Removal: After cooling and solidification, the streamlined upper shell structure of the aluminum-lithium alloy UAV is removed from the mold.

[0073] S10 Heat Treatment: The streamlined upper shell structure of the unmanned aerial vehicle (UAV) was subjected to T6 heat treatment. The casting was heated to 500 ℃ and held for 2 hours for solution treatment, followed by water quenching; then heated to 175 ℃ and held for 8 hours for artificial aging treatment.

[0074] S11 Surface Treatment: The streamlined upper shell structure of the UAV after heat treatment is cleaned and subjected to micro-arc oxidation treatment to grow a ceramic film layer in situ on the surface.

[0075] The streamlined upper shell of the aluminum-lithium alloy UAV prepared in Example 2 was subjected to performance testing and appearance inspection. The results are as follows: Appearance quality: The curved surface is smooth and free of flow marks, and can be directly anodized.

[0076] Electromagnetic shielding: Compared to traditional plastic shells, the aluminum-lithium alloy shell used in this embodiment has natural electromagnetic shielding performance, effectively protecting the internal GPS and flight control modules from external interference.

[0077] Mechanical properties: Tests showed that the streamlined upper shell of this aluminum-lithium alloy drone has a tensile strength of 495 MPa and an elongation of 6.0%. In simulated high-frequency vibration fatigue tests, its fatigue life is more than three times that of traditional A356 aluminum alloy die-cast parts, and no fatigue cracks were found.

[0078] Composition consistency: Spectroscopic analysis showed that the lithium (Li) content in the casting was 2.78%, which is highly consistent with the formula value (2.8%), further verifying the excellent effect of the 10 Pa high vacuum environment on suppressing the burn-off of high lithium content.

[0079] Post-processing performance: After S11 micro-arc oxidation, a grayish-white ceramic-textured film layer is formed on the surface. The film layer has high hardness, strong adhesion, excellent insulation and heat dissipation radiation performance, which meets the installation and heat dissipation requirements of the drone motherboard.

[0080] The above are merely preferred embodiments of the present invention and do not limit the scope of protection of the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any changes, modifications, substitutions, integrations, and parameter alterations to these embodiments within the spirit and principles of the present invention, achieved through conventional substitutions or by achieving the same function without departing from the principles and spirit of the present invention, fall within the scope of protection of the present invention.

Claims

1. An integrated vacuum melting and die-casting equipment, characterized in that, This includes a melting chamber, a melting crucible located within the melting chamber, a die-casting mold, a barrel, an injection rod, a vacuum pump assembly, and a mold temperature controller. One end of the barrel is connected to the cavity of the die-casting mold, and the other end passes through the melting chamber and is connected to the injection rod; The smelting crucible is mounted on the tilting drive mechanism, which is used to drive the smelting crucible to tilt so as to pour the molten material formed by smelting into the material cylinder; The injection rod is used to inject the molten material in the barrel into the cavity of the die-casting mold; The die-casting mold is used to die-cast the molten material in the cavity; The vacuum pump unit is connected to the melting chamber and the die-casting mold, and is used to draw a vacuum. The mold temperature controller is connected to the die-casting mold and is used to preheat the die-casting mold.

2. The integrated vacuum melting and die-casting equipment according to claim 1, characterized in that, The smelting crucible is made of silicon carbide, high-purity graphite, magnesium oxide, or steel with a ceramic barrier coating on the inner wall.

3. A method for integral molding of aluminum-lithium alloy UAV structural components by vacuum melting and die casting, characterized in that, The method for preparing aluminum-lithium alloy UAV structural components using the vacuum melting and die-casting integrated equipment as described in claim 1 or 2 includes: S1: Place the aluminum-lithium alloy raw material in a melting crucible, wherein the aluminum-lithium alloy raw material, by mass percentage, has the following chemical composition: Li: 1.0-3.0%; Cu: 1.0-4.5%; Mg: 0.5-2.0%; Zr: 0.05-0.2%; the balance being Al and unavoidable impurities; S2: Before closing the mold, the die-casting mold is preheated to a preset temperature. S3: After the die-casting mold reaches the preset temperature, spray a release agent onto the cavity surface of the die-casting mold, blow it dry, and then close the die-casting mold. S4: Evacuate the melting chamber, the barrel, and the die-casting mold to bring the integrated vacuum melting and die-casting equipment to a preset vacuum environment; S5: Under the vacuum environment, the melting crucible is heated to melt the aluminum-lithium alloy raw material in the melting crucible into an aluminum-lithium alloy melt and keep it at the temperature; S6: Pour the aluminum-lithium alloy melt into the barrel; S7: Under the action of the injection rod, the aluminum-lithium alloy melt in the barrel is injected into the cavity of the die-casting mold; S8: After the aluminum-lithium alloy melt fills the cavity, the aluminum-lithium alloy melt is solidified under pressure. S9: After the pressure holding and solidification are completed, the mold is opened to obtain the aluminum-lithium alloy UAV structural parts.

4. The vacuum melting and die-casting integrated molding method for aluminum-lithium alloy UAV structural components according to claim 3, characterized in that, The aluminum-lithium alloy drone structural components include any one of the following: drone arms, fuselage mid-frame, fuselage frame, motor mount, and landing gear. A reinforcing rib groove is provided in the cavity at a position corresponding to the aluminum-lithium alloy drone structural component. The reinforcing rib groove is used to form an irregular thin-walled structure of internal reinforcing ribs or heat dissipation channels of the aluminum-lithium alloy drone structural component.

5. The vacuum melting and die-casting integrated molding method for aluminum-lithium alloy UAV structural components according to claim 3, characterized in that, In S2, the preset temperature is 200-300 ℃.

6. The vacuum melting and die-casting integrated molding method for aluminum-lithium alloy UAV structural components according to claim 3, characterized in that, In S4, the preset vacuum environment is a high vacuum state with a pressure lower than 50 Pa; In S5, the melting temperature of the aluminum-lithium alloy is 720–780 °C.

7. The vacuum melting and die-casting integrated molding method for aluminum-lithium alloy UAV structural components according to claim 3, characterized in that, In S6, the tilting rate of the melting crucible is 10–80 ° / s.

8. The vacuum melting and die-casting integrated molding method for aluminum-lithium alloy UAV structural components according to claim 3, characterized in that, In S7, the injection rate of the injection rod is 3 to 7 m / s; In S8, the pressure for holding the aluminum-lithium alloy melt is 60-120 MPa, and the holding time is 2-15 s.

9. The vacuum melting and die-casting integrated molding method for aluminum-lithium alloy UAV structural components according to claim 3, characterized in that, The method further includes: S10: subjecting the obtained aluminum-lithium alloy UAV structural component to T6 heat treatment; wherein... The aluminum-lithium alloy UAV structural component is heated to 480-530℃ and held for 2-8 hours for solution treatment, followed by water quenching. The aluminum-lithium alloy UAV structural components, after water quenching and cooling, are heated to 150-180℃ and held for 6-24 hours for artificial aging treatment.

10. The vacuum melting and die-casting integrated molding method for aluminum-lithium alloy UAV structural components according to claim 9, characterized in that, The method further includes: S11: performing surface anodizing or micro-arc oxidation treatment on the aluminum-lithium alloy drone structural parts after T6 heat treatment, so that a corrosion-resistant layer is formed on the surface of the aluminum-lithium alloy drone structural parts.

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