Composite metal material applied to unmanned aerial vehicle and preparation method thereof

Abstract

The present application relates to a kind of composite metal material applied to unmanned aerial vehicle and preparation method thereof, the composite metal material includes the core layer part by aluminum base alloy, the surface layer aluminum alloy part being arranged on the upper and lower two surfaces of the core layer part and optional intermediate Zn layer, effectively improve the external component and load-bearing distortion component suitable for long-term work in harsh environment unmanned aerial vehicle, improve the large-angle bending requirement and surface adhesion requirement required by miniaturization component, also meet the basic demand and other mechanical properties of light weight material.

Description

Technical Field

[0001] This invention relates to composite metal materials, and more specifically, to a composite metal material for use in unmanned aerial vehicles (UAVs) and its preparation method. Background Technology

[0002] With the development of automatic control, artificial intelligence, and the electronic information industry, the field of unmanned aerial vehicles (UAVs) has made significant progress. UAVs for various applications have been developed, and many products have entered the market. In the field of UAV fuselage materials, high-strength and lightweight metal and composite materials are widely used in UAV airframe structures due to their advantages such as high specific strength, high specific modulus, and light weight. However, as UAV applications become more widespread, many UAVs need to operate for extended periods under harsh conditions, such as earthquake relief and forest fire fighting. This necessitates relatively compact UAV dimensions while simultaneously requiring the addition of large loads when needed. As the weight and size of UAVs decrease, their structural materials must be able to withstand large-angle bending or twisting (greater than 90 degrees, even greater than 120 degrees) to form fuselage components within small to medium dimensions. This places higher demands on the application of metal composite materials.

[0003] Numerous studies and products have explored structural materials for drones. For example, patent publication CN118124213A discloses a wear-resistant, lightweight composite metal material for drone shells. This patent document provides a wear-resistant, lightweight composite metal material for drone shells that can significantly improve the impact resistance of drone shells, and the molding process is relatively simple. However, this type of material does not consider the performance requirements of rigid materials that need to be folded at large angles at corners or bends under the size requirements of medium and small drones, nor does it consider the working requirements of the material surface under long-term harsh working conditions. Summary of the Invention

[0004] The purpose of this invention is to address one or more shortcomings in the prior art by improving the bendability, toughness, surface coating adhesion, and other mechanical properties of composite metal materials used in drones through specific alloy composition, rolling process, and layer configuration.

[0005] A first aspect of the present invention provides a composite metal material applicable to unmanned aerial vehicles (UAVs), the composite metal material comprising a core layer portion made of an aluminum-based alloy and surface aluminum alloy portions disposed on upper and lower surfaces of the core layer portion, wherein the core layer portion made of the aluminum-based alloy has the following composition expressed in weight percent:

[0006] 0.8% ≤ Mg ≤ 1.2%

[0007] 0.5% ≤ Si ≤ 0.8%

[0008] Fe≤0.3%

[0009] Cu≤0.1%

[0010] Mn≤0.1%

[0011] Cr≤0.1%

[0012] 0.2% ≤ Zn ≤ 0.4%

[0013] Ti≤0.1%,

[0014] Besides the components mentioned above, the remainder consists of Al and unavoidable impurities; and

[0015] The surface aluminum alloy portion has the following alloy composition, shown in weight percent:

[0016] Si≤0.20%

[0017] Fe≤0.3%

[0018] Cu≤0.1%

[0019] Mn≤0.10%

[0020] 0.8% ≤ Mg ≤ 1.5%

[0021] Cr≤0.1%

[0022] 0.6% ≤ Zn ≤ 1.2%; the remainder is Al and unavoidable impurities.

[0023] In a preferred embodiment, an intermediate Zn layer exists between the core layer composed of aluminum-based alloy and the surface aluminum alloy layer. The intermediate Zn layer exists between the core layer composed of aluminum-based alloy and the surface aluminum alloy layer in a continuous or discontinuous manner, and the maximum thickness of the intermediate Zn layer is less than 1 micrometer.

[0024] Furthermore, in a preferred embodiment, a portion of the Zn composition in the surface aluminum alloy portion originates from the intermediate Zn layer.

[0025] In a preferred embodiment, the thickness of the core layer portion made of aluminum-based alloy is approximately 4 mm to approximately 9 mm, the thickness of the surface aluminum alloy portion is approximately 0.5 mm to 1 mm, and the thickness of the composite metal material is approximately 5 mm to approximately 10 mm.

[0026] A second aspect of the present invention provides a method for manufacturing a composite metal material applicable to unmanned aerial vehicles (UAVs), the method comprising the following steps:

[0027] Step 1) Cast aluminum alloy blanks

[0028] An aluminum-based alloy ingot is obtained using a casting process, and a cast aluminum alloy billet is obtained from the ingot.

[0029] Step 2) Homogenize and cast aluminum alloy billets

[0030] The cast aluminum alloy billet obtained in step 1) is homogenized in a melting furnace at a homogenization temperature of 500-650℃ for 1 to 3 hours to obtain a homogenized cast aluminum alloy billet.

[0031] Step 3) Forming the initial surface aluminum alloy portion

[0032] After homogenization, the upper and lower surfaces of the cast aluminum alloy blank are treated with a immersion bath containing Zn ions to coat an intermediate Zn layer.

[0033] A preliminary surface layer of aluminum alloy is applied to the surface of a cast aluminum alloy blank with an intermediate Zn layer deposited thereon.

[0034] Step 4) Hot rolling process

[0035] The cast aluminum alloy billet obtained in step 3) is fed into a hot rolling mill for one or more hot rolling passes. In at least the first or first two hot rolling passes, the hot rolling temperature is maintained above 550°C. After hot rolling, the hot-rolled strip is cooled and coiled to obtain a hot-rolled composite metal strip.

[0036] Step 5) Cold rolling process

[0037] The hot-rolled composite metal strip obtained in step 4) above is fed into a cold rolling equipment for cold rolling, and one or more passes of cold rolling are performed to obtain a cold-rolled composite metal strip.

[0038] Step 6) Solution annealing

[0039] The cold-rolled composite metal strip obtained in step 5) above is fed into an annealing furnace for annealing. The annealing temperature is greater than 600℃, and the annealing time is controlled to be less than 1 minute.

[0040] The strip after solution annealing is cooled and then wound again to obtain a composite metal material applicable to drones. The composite metal material applicable to drones includes a core layer and a surface aluminum alloy layer located on the surface of the core layer.

[0041] In a further preferred embodiment, the method specifically includes the following steps:

[0042] Step 1) Cast aluminum alloy blanks

[0043] An aluminum-based alloy ingot is obtained using a casting process to obtain a cast aluminum alloy billet, which has the following composition expressed as a percentage by weight:

[0044] 0.8% ≤ Mg ≤ 1.2%,

[0045] 0.5% ≤ Si ≤ 0.8%,

[0046] Fe≤0.3%,

[0047] Cu≤0.1%,

[0048] Mn≤0.1%

[0049] Cr≤0.1%

[0050] 0.2% ≤ Zn ≤ 0.4%,

[0051] Ti≤0.1%,

[0052] Apart from the components mentioned above, the remainder consists of Al and unavoidable impurities;

[0053] Step 2) Homogenize and cast aluminum alloy billets

[0054] The cast aluminum alloy billet obtained in step 1) is homogenized in a melting furnace at a homogenization temperature of 550 to 560°C for 1 to 2 hours to obtain a homogenized cast aluminum alloy billet.

[0055] Step 3) Forming the initial surface aluminum alloy portion

[0056] After homogenization, the cast aluminum alloy billet is degreased and placed in a sodium hydroxide solution with a concentration of 50-100 g / L at 50-60°C to remove the Al oxide film on the surface. Subsequently, the surface of the surface-treated cast aluminum alloy billet is washed with pure water and placed in a zinc sulfate solution with a concentration of 50 to 150 g / L for zinc precipitation treatment for 1 to 10 minutes to displace the intermediate Zn layer deposited on the surface of the cast aluminum alloy billet. The thickness of the intermediate Zn layer is 1 to 5 micrometers.

[0057] A preliminary surface aluminum alloy portion is applied to the surface of a cast aluminum alloy blank having an intermediate Zn layer deposited thereon. The preliminary surface aluminum alloy portion has the following composition, shown in weight percent:

[0058] Si≤0.20%

[0059] Fe≤0.3%

[0060] Cu≤0.1%

[0061] Mn≤0.10%

[0062] 0.8% ≤ Mg ≤ 1.5%

[0063] Cr≤0.1%

[0064] 0.5% ≤ Zn ≤ 1.0%;

[0065] The remainder consists of Al and unavoidable impurities.

[0066] The thickness of the initial surface aluminum alloy layer applied is 1 mm to 2 mm;

[0067] Step 4) Hot rolling process

[0068] The cast aluminum alloy billet obtained in step 3) is fed into a hot rolling mill for 4 to 6 passes of hot rolling. In the first two passes, the hot rolling temperature is maintained at 580°C to 600°C.

[0069] Maintain a temperature of 460°C or higher before the cast aluminum alloy billet enters the penultimate hot rolling pass;

[0070] Next, the hot-rolled billet that has formed the preliminary hot-rolled strip is cooled down using a cooling device, gradually cooled to a temperature of 180 to 200°C, and then rolled to obtain hot-rolled composite metal strip;

[0071] Step 5) Cold rolling process

[0072] The hot-rolled composite metal strip obtained in step 4) above is fed into a cold rolling equipment for cold rolling, and one or more passes of cold rolling are performed to obtain a cold-rolled composite metal strip.

[0073] Step 6) Solution annealing

[0074] The cold-rolled composite metal strip obtained in step 5) above is fed into an annealing furnace for annealing. The annealing temperature is controlled at 620 to 630°C, and the annealing time is controlled at 20 to 40 seconds. It is then cooled to 200 to 250°C and wound to obtain a composite metal material applicable to drones.

[0075] The composite metal material applicable to drones includes a core layer and a final surface aluminum alloy layer on the surface of the core layer, the core layer having a thickness of approximately 4-9 mm and the final surface aluminum alloy layer having a thickness of approximately 0.5 to 1 mm.

[0076] In a further preferred embodiment, the final surface aluminum alloy portion of the composite metal material applicable to drones has the following composition:

[0077] Si≤0.20%

[0078] Fe≤0.3%

[0079] Cu≤0.1%

[0080] Mn≤0.10%

[0081] 0.8% ≤ Mg ≤ 1.5%

[0082] Cr≤0.1%

[0083] 0.6% ≤ Zn ≤ 1.2%.

[0084] Among other alternative technical solutions, the composite metal material applicable to UAVs satisfies one of the following:

[0085] The core layer portion directly contacts the final surface aluminum alloy portion located on the surface of the core layer portion without any intermediate Zn layer between them; or

[0086] The intermediate Zn layer exists between the core layer and the final surface aluminum alloy layer, either continuously or discontinuously, with a maximum thickness of less than or equal to 0.5 μm.

[0087] The method for manufacturing a composite metal material applicable to drones as described in the second aspect of the present invention can be used to manufacture the composite metal material applicable to drones as described in the first aspect. Conversely, the composite metal material applicable to drones as described in the first aspect of the present invention can be manufactured by the method described in the second aspect above.

[0088] The composite metal material and its manufacturing method applicable to unmanned aerial vehicles provided by the present invention effectively improve the external components and load-bearing torsion components of unmanned aerial vehicles that are suitable for long-term operation in harsh environments, improve the large-angle bending requirements and surface adhesion requirements of miniaturized components, and also meet the basic requirements of lightweight materials and other mechanical properties.

[0089] The technical solutions and advantages of the present invention will be explained and described in more detail below with reference to specific embodiments. It should be understood that the content presented in the specification and specific embodiments is only for the purpose of more clearly illustrating the technical solutions and advantages of the present invention, and does not constitute a limitation on the scope of protection of the present invention. Those skilled in the art can obtain various reasonable modifications based on the disclosure in the specification, and as long as they do not depart from the spirit of the present invention, all modified technical solutions should be understood to be included within the scope of protection of the present invention. Attached Figure Description

[0090] The accompanying drawings shown in this application are intended to provide a further understanding of the technical solutions disclosed herein and constitute a part of the specification. They are used together with the specific embodiments of this application to explain the technical solutions disclosed herein and do not constitute a limitation on the technical solutions disclosed herein.

[0091] Figure 1 This is a schematic flowchart of the hot rolling process of composite metal materials applicable to drones according to the present invention;

[0092] Figure 2 This is an SEM electron microscope image of the cross section of the composite metal material strip prepared according to Example 1 of the present invention after metallographic sectioning.

[0093] Figure 3 This illustrates a bending angle testing apparatus for a sample of the present invention;

[0094] Figure 4 A schematic diagram of the alloy composite bending angle α is shown;

[0095] Figure 5 This is a schematic diagram of the load-bearing frame of an unmanned aerial vehicle made using the composite metal material of this invention.

[0096] The reference numerals in the various figures can be simply represented as follows:

[0097] 100-Slab cooling device; 200-Hot-rolled billet; 300-Slab cooling device; 400-Hot-rolled strip; 401-Core layer; 402-Surface alloy coating; 500-Final slab cooling device; 600-Hot-rolled coiler; 700-Measuring bending angle; 800-Side beam member of load-bearing frame; 900-Connecting member. Detailed Implementation

[0098] The invention is described in more detail below to aid in understanding it.

[0099] Before describing the specific implementation scheme, it should be noted that those skilled in the art can select appropriate raw materials based on the teachings and guidance of this disclosure, conduct relevant tests using relevant testing equipment, and obtain corresponding results. For raw materials for which specific manufacturers or methods are not specified, those skilled in the art can select raw materials that meet the corresponding requirements as reaction starting materials based on the disclosure and needs of this specification. The reaction raw materials for the compounds in the process section are derived from the initial products synthesized in the preceding steps of this invention, which is also understandable based on this disclosure.

[0100] First, it should be noted that the raw materials not described in this invention are varieties of raw materials that can be obtained by those skilled in the art based on ordinary technical knowledge and existing market products.

[0101] Furthermore, it should be noted that percentages specified in the technical solutions, embodiments, and summary sections of this invention are generally described in detail. Unless otherwise specified, concentrations or percentages refer to mass percentages (wt%) or units of mass such as grams per liter (g / L). For example, components used in the embodiments generally refer to mass percentages, while solutions can be expressed in g / L.

[0102] Furthermore, this invention can employ open-ended component definition methods such as "comprising" or "including" to indicate that embodiments of the invention may include the main components / coatings used, as well as other auxiliary components / coatings. However, in preferred embodiments of the invention, it may consist only of the components and coatings defined by the invention, without necessarily including any other components. For example, the composite metal material described in the embodiments of the invention may include an aluminum alloy core layer, an aluminum alloy surface layer, and may also include other auxiliary layers (e.g., a Zn layer present with a very small thickness), or other layers (e.g., decorative layers) and / or other unavoidable layers (e.g., oxide layers on the surface of the formed aluminum alloy). Meanwhile, in preferred embodiments of the invention, it may consist only of the described components: an aluminum alloy core layer, an aluminum alloy surface layer, and / or an intermediate Zn layer, without having or including other intermediate layers or other coatings with significant main components. In the description of the technical solutions, "one layer is located on top of another layer" generally refers to one layer being directly located on another layer without any other layers in between. "A layer is located between two layers" may refer to the surface of that layer being in direct contact with both layers.

[0103] Test experiments of the present invention

[0104] Before describing the preparation examples, the testing procedures, standards, and characterization methods used in typical experiments of this invention will be briefly described first. For methods and parameters not described, those skilled in the art can use methods known or accepted in the field of metallic materials to perform the measurements.

[0105] 1. Bending angle test (α)

[0106] It is necessary to describe the process flow of the bending angle test of the present invention in a simple manner, but those skilled in the art are not necessarily limited to this description and may use similar or other standard methods already available in the field of alloy material bending to perform the test. Figure 3The test apparatus for performing the bending test is schematically illustrated using a close-up macro camera photograph, which can be used to determine the maximum bending angle. The test apparatus consists of bending rollers, typically with a roller radius of 2.0 cm. The sample was previously cut into 800 mm × 200 mm pieces perpendicular to the rolling direction. The sample was then pre-stretched by 10% perpendicular to the rolling direction at a pre-stretching speed of 15 mm / min. The resulting sample was then cut into 200 × 200 mm pieces and fed to the bending device. Figure 3 The bending rollers shown extend parallel to the rolling direction, and the bending line also extends parallel to the rolling direction. The bending rollers press the sample between two rollers with a diameter of 2.0 cm, spaced 10 times the sample thickness, using a force F. The roller force F is measured during the bending process. If the roller force F reaches its maximum and then gradually decreases, it indicates that the bending angle of the sample has reached its limit, and the material may begin to fail (e.g., delamination, cracking, or abnormal twisting). The test is stopped when the force F decreases by 20 N from the peak force. The sample is then removed from the bending device and... Figure 4 The bending angle shown is 70° (α). The "bending angle" referred to in the embodiments and experiments of this invention refers to the angle between the two sides of the bent metal composite material after reaching its maximum bending degree.

[0107] 2. Surface adhesion test

[0108] This invention also relates to testing the surface adhesion of samples under harsh conditions, which is instructive for the use of UAV composite materials in complex external environments. Under typical test conditions, a 3% wt acetic acid test is selected. The sample is first rapidly rinsed with a 3% wt sodium bicarbonate (Na₂CO₃) solution at approximately 45°C to remove surface-adhered impurities and some oxides. The subsequent 3% acetic acid test can include an assessment of the surface aluminum alloy layer's resistance to diluted acidic media for 120 minutes at approximately 100°C. The test can involve cutting the sample with cross-shaded markings and placing the sample in a 3% acetic acid solution at approximately 100°C for 120 minutes, after which the sample is removed and cooled. Then, an additional set of cross-cuts is performed on each sample, with tape placed above the cross-shaded areas before and after the acid bath, and the tape is steadily removed at an angle of approximately 60° within 0.5 to 1 second. If there are no visible aluminum alloy coating peeling points on the tape, it is excellent (3 points); if there are visible peeling points on the surface of the tape, it is acceptable (2 points); if there are flaky peeling pieces on the tape, it is unacceptable (1); if there are cracks on the surface, it is unacceptable (0 points).

[0109] Furthermore, other relevant tests for composite metal materials, which are frequently tested, can be performed with reference to existing industry standards or international / national standards. For example, tests related to the elongation of aluminum alloys (such as ultimate elongation and elongation at break) can be performed with reference to the relevant content of international standard ISO 6892-1:2016, and tests related to tensile strength can be performed with reference to GB / T-228.1-2010. These will not be elaborated further in this specification.

[0110] The following description, in conjunction with the accompanying drawings, will specifically illustrate the composite metal material applicable to unmanned aerial vehicles (UAVs) and its preparation method.

[0111] Step 1) Cast aluminum alloy blanks

[0112] The core layer of the aluminum alloy composite material is obtained by casting. In the preparation method of the composite metal material of this invention, casting processes from related or existing technologies can be used, as long as the aluminum alloy meets the following composition expressed in weight percent:

[0113] 0.8% ≤ Mg ≤ 1.2%

[0114] 0.5% ≤ Si ≤ 0.8%

[0115] Fe≤0.3%

[0116] Cu≤0.1%

[0117] Mn≤0.1%

[0118] Cr≤0.1%

[0119] 0.2% ≤ Zn ≤ 0.4%

[0120] Ti≤0.1%,

[0121] In addition to the above components, the remainder consists of Al and unavoidable impurities. In order to ensure the subsequent mechanical and other properties of the metal composite material, the total amount of impurities in the core layer shall not exceed 0.10% wt, and the mass of a single impurity shall preferably not exceed 0.03%.

[0122] In preferred embodiments of the present invention, alloy compositions within the aforementioned range are preferred, which facilitates the application of the present invention to unmanned aerial vehicle structural components or external supports. Some experiments suggest that an increase in Mg content exceeding 0.5% can affect the toughness and bending resistance of aluminum alloys. However, according to the design of this application, a Mg content of 0.8% ≤ 1.2% is preferred, while also ensuring sufficient toughness and strength in bending tests and coatings. The inventors have surprisingly discovered that, while Mg is present in the aluminum alloy, adding a suitable high content of Zn (e.g., 0.2% to 0.4% wt) can improve the interlocking of magnesium-zinc grains, ensuring the auxiliary strengthening effect of Mg on the strength of the aluminum alloy, while simultaneously moderately reducing the Si content and decreasing the number of non-bending hard compounds between Mg and Si. However, a small amount of silicon helps maintain the bonding between various alloying elements and the curing characteristics of the composite metal material. When the Si content is greater than 0.8%, excessive MgSi intermediate hard particles are synthesized with the high-strength auxiliary element Mg, which is detrimental to the properties of the metal composite material under extreme bending conditions. Furthermore, the presence of a small amount of Fe helps refine the grain boundaries between the various metal phases, but the Fe content needs to be limited to a maximum of 0.3% by weight to avoid coarse precipitates. Copper can improve corrosion resistance, and its content should be limited to a maximum of 0.1% by weight. Manganese below 0.1% by weight can help suppress the formation of coarse manganese precipitates. Although chromium (Cr) helps form a fine structure, it should also be limited to 0.1% by weight to avoid coarse precipitates. In addition, it was unexpectedly found that Zn, in addition to helping improve the corrosion resistance of the alloy, can also form the ZnMg crystal phase with high Mg content, helping to obtain improved bending resistance and coating adhesion. Titanium helps refine the grains during the casting process, but should be limited to a maximum of 0.1% by weight to ensure good castability of the aluminum alloy. The composition of the core layer in a typical embodiment is shown in the table below.

[0123] Table 1: Composition of the core layer (wt%, balance is Al and impurities, omitted)

[0124]

[0125] Step 2) Homogenization treatment of cast aluminum alloy billets

[0126] The cast aluminum alloy billet from step 1) is homogenized in a melting furnace at a homogenization temperature of about 560°C for 2 hours, thereby making the alloy composition more evenly distributed in the billet to be rolled.

[0127] Step 3) Forming a preliminary surface aluminum alloy coating

[0128] In a typical process, a specified Zn layer is first deposited on the cast aluminum alloy blank, which will provide improved performance for the composite metal material in subsequent tests.

[0129] In this embodiment, the cast aluminum alloy blank is degreased and then subjected to alkaline etching at 50-60°C (immersed in a sodium hydroxide solution with a concentration of 80-100 g / L) to remove the Al oxide film on the surface, exposing the pure Al surface. Subsequently, the surface of the die-cast aluminum alloy part after surface treatment is washed with pure water and immersed in a zinc sulfate solution with a concentration of 100 g / L for 2 to 5 minutes to displace a thin zinc layer with certain adhesion. During deposition, the thickness of the Zn layer is ensured to be greater than 1 micrometer; preferably, in this embodiment, a Zn deposition layer of 3 to 5 micrometers is formed.

[0130] Subsequently, the aluminum alloy coating to be applied is prepared according to the following composition, wherein, in embodiments of the invention, the preliminary surface aluminum alloy coating (before rolling and heat treatment) typically has the following alloy composition, shown in weight percent:

[0131] Si≤0.20%

[0132] Fe≤0.3%

[0133] Cu≤0.1%

[0134] Mn≤0.10%

[0135] 0.8% ≤ Mg ≤ 1.5%

[0136] Cr≤0.1%

[0137] 0.5% ≤ Zn ≤ 1.0%;

[0138] The remainder consists of Al and unavoidable impurities, with each individual impurity not exceeding 0.03% and the total not exceeding 0.10%.

[0139] The aforementioned aluminum alloy coating can be applied to both sides of the core layer using existing plating techniques to form a covering, such as melt plating (e.g., melt casting followed by scraping), melt bath immersion, electroplating, etc. Those skilled in the art can apply the aluminum alloy coating according to the alloy composition disclosed in this invention. The surface aluminum alloy coating thickness is maintained at 1 mm to 1.5 mm. In typical implementation processes, it is controlled to be approximately 1 to 1.2 mm.

[0140] In the aluminum alloy coating, some elements and compositions are similar to those in the core layer. However, the inventors discovered that further increasing the content of Mg and Zn elements is beneficial for further improving the adhesion between the surface and core layers, as well as the bending resistance of the surface layer.

[0141] The percentage of the initial surface aluminum alloy coating in a typical embodiment is shown in the table below.

[0142] Table 2: Preliminary composition of the surface layer (wt%, balance is Al and impurities, omitted)

[0143]

[0144] Step 4) Hot rolling process

[0145] The blank to be rolled, which has had a surface aluminum alloy coating applied in step 3), is rolled using a hot rolling mill (such as...). Figure 1 The slab (100) shown is hot-rolled. In the hot rolling process of this embodiment, the hot rolling temperature is controlled to be greater than 550°C (580°C to 600°C in this embodiment). Hot rolling can be repeated in multiple passes (e.g., 4 to 6 hot rolling passes, 5 hot rolling passes are selected in this embodiment). The figure only shows the state of one hot rolling process as an example. The slab can be moved left and right repeatedly for multiple rolling passes. In the first one or two hot rolling passes, maintaining the temperature above 550°C is beneficial to the fusion of the Zn layer and the overlying preliminary surface aluminum alloy coating.

[0146] The hot-rolled billet 200 preferably has a temperature of at least 460°C after leaving the hot rolling mill 100 and before entering the penultimate hot rolling process, and preferably is maintained at a temperature of 480°C-500°C. During this time, the hot-rolled billet 200, having already formed a preliminary hot-rolled strip 400, is cooled (e.g., by air cooling or water cooling) using the slab cooling device 300 and auxiliary work rolls of the hot rolling mill 100 within the aforementioned temperature range. The hot-rolled strip 400 can be repeatedly moved left and right for two or more hot rolling passes.

[0147] For example, in one embodiment, the hot-rolled strip is cooled to a temperature of 330-350°C before the final hot rolling process, thereby further cooling the strip. To this end, the slab cooling device 100 sprays the hot-rolled strip with a cooled emulsion, accelerating its cooling. The work rolls of the hot rolling mill are also coated with an emulsion, further cooling the hot-rolled strip and lowering its temperature in the final hot rolling process. In this embodiment, after the final hot rolling process, the hot-rolled strip 400 has a temperature of 180 to 200°C at the exit of the slab final cooling device 500, and is then wound at this temperature by the hot-rolling coiler 600 to obtain a hot-rolled composite metal strip with a thickness of 10 mm to 15 mm.

[0148] In the process of this invention, the aforementioned hot rolling temperature is beneficial for controlling an appropriate grain elongation rate of the hot-rolled strip at the end of the hot rolling process; otherwise, it would be detrimental to the preparation of tough materials with large-angle bending resistance in the later stages. If the elongation rate is too high or too low, it would be difficult for the various coatings of the billet to effectively maintain the corresponding crystal morphology during the cold rolling process.

[0149] Step 5) Cold rolling process

[0150] The hot-rolled composite metal strip obtained in step 4) is fed into a cold rolling mill for cold rolling. In this embodiment, cold rolling can be performed using a cold rolling process known in the art, and can be performed in one or more passes to obtain a cold-rolled composite metal strip with a diameter of 5 mm to 10 mm.

[0151] 6) Solution annealing

[0152] The cold-rolled composite metal strip from step 5 is wound and then annealed in an annealing furnace. In this process, the annealing temperature is preferably greater than 600°C, typically controlled at 620-630°C, for 30 to 40 seconds. This helps the Zn cladding, which has initially penetrated into the aluminum alloy layer during the hot rolling process, to more effectively penetrate and fuse with the core and surface aluminum alloy layers. Afterward, it is rapidly cooled to 200 to 250°C and wound again. A composite metal strip of 5 mm to 10 mm in diameter is obtained.

[0153] In the final composite metal strip, the core aluminum alloy layer is approximately 4-9 mm thick, and the surface layer (upper and lower layers) is approximately 0.5 to 1 mm thick.

[0154] The inventors first performed a longitudinal section on the final sample obtained in the typical preparation of Example 1 in the implementation scheme, and after metallographic specimen pretreatment, conducted SEM cross-sectional electron microscopy observation. For example... Figure 2 As shown. Figure 2 Image 401 shows the core layer of the composite metal strip, and image 402 shows the surface alloy coating. Different colors in the image represent different orientations of grains or crystal phases. No other layers are visible between the core and the surface layer.

[0155] In addition, from Figure 2 The cross-sectional electron microscope images show that the boundary between the core layer 401 and the surface alloy covering layer 402 of the composite metal strip is obvious, and the grain size varies greatly. The inventors do not limit themselves to any theoretical explanation, but speculate that the intermediate Zn coating layer plays a certain role in separating the layers in a short period of time. At the same time, the high hot rolling temperature has a significant impact on the surface layer, promoting the rapid growth and elongation of the surface alloy grains with high ZnMg composition.

[0156] In addition, the surface and core layers in the embodiments were analyzed by X-ray fluorescence spectroscopy to determine the elemental composition. The inventors found that the Zn content in the final surface aluminum alloy coating was slightly higher than that in the initial surface aluminum alloy coating, with the final surface Zn content being 0.1 wt% to 0.2 wt% higher than the initial surface Zn content, while the Zn composition of other components and the core layer remained almost unchanged. In other words, the final surface aluminum alloy coating typically has the following alloy composition, shown in weight percent:

[0157] Si≤0.20%

[0158] Fe≤0.3%

[0159] Cu≤0.1%

[0160] Mn≤0.10%

[0161] 0.8% ≤ Mg ≤ 1.5%

[0162] Cr≤0.1%

[0163] 0.6% ≤ Zn ≤ 1.2%; the remainder consists of Al and unavoidable impurities, with each individual impurity not exceeding 0.03% and the total not exceeding 0.10%.

[0164] In other words, in the final aluminum alloy composite material, a portion of the Zn content in the final surface aluminum alloy coating originates from the intermediate transition Zn layer between the aluminum alloy core layer and the aluminum alloy surface layer. This intermediate transition Zn layer in the process of this invention may be completely absent in the final aluminum alloy composite material due to upward diffusion, or it may exist in a trace amount with a thickness of less than approximately 1.0 μm between the aluminum alloy core layer and the aluminum alloy surface layer.

[0165] The inventors believe that the Zn element in the embodiments of the present invention tends to diffuse towards the surface layer. This is partly because the hot rolling temperature set in the process of the present invention is relatively high, and hot rolling has a significantly greater impact on the surface layer than on the core layer. Therefore, the high heat in the surface layer attracts the upward diffusion of Zn. Furthermore, the high Mg and low silicon content in the surface layer may control and reduce the formation of ultra-hard MgSi compounds, which also contributes to the greater attraction of Zn to fuse upwards.

[0166] Comparative experiment

[0167] The inventors then conducted a series of comparative experiments to compare the invention with the preferred implementation scheme.

[0168] Comparative Example 1

[0169] In Comparative Example 1, the same alloy components as described in Example 1 were used, and a similar process to that of Example 1 was employed. The difference lies in the manufacturing process of Comparative Example 1: after the homogenization treatment of the cast aluminum alloy billet in step 2) of Example 1, the Zn deposition layer formation process was omitted in step 3), and the process proceeded directly to the subsequent aluminum alloy coating process and the hot rolling step in step 4). Except for the aforementioned processes, all other processes were identical to those in Example 1, and their manufacturing procedures will not be described in detail here.

[0170] Comparative Example 2

[0171] In Comparative Example 2, the same alloy components as described in Example 1 were used, and a similar process as in Example 1 was employed. The difference lies in the manufacturing process of Comparative Example 2: after the homogenization treatment of the cast aluminum alloy blank in step 2) of Example 1, the following step 3) was performed:

[0172] The cast aluminum alloy blanks are degreased and then subjected to alkaline etching at 50–60°C (immersed in an 80–100 g / L sodium hydroxide solution) to remove the surface Al oxide film, exposing the pure Al surface. Subsequently, the surface-treated die-cast aluminum alloy parts are immersed in a 150 g / L zinc sulfate solution for 15 minutes to displace a thicker zinc layer. After deposition, SEM scanning microscopy analysis of the sample cross-section shows a thickness of approximately 20 to 30 micrometers.

[0173] Comparative Example 3

[0174] In Comparative Example 2, the same alloy components as described in Example 1 were used, and a similar process as in Example 1 was employed. The difference was that in step 4), the hot rolling temperature was controlled at 480°C to 500°C, while the rest of the process was the same as described in the examples.

[0175] Comparative Examples 4-7

[0176] The same process steps as described in the examples were used in Comparative Examples 4-7. However, the core alloy composition and surface alloy composition listed in the following table were used in the corresponding comparative examples.

[0177] Table 3: Composition of the core layer in the comparative experiment (wt%, balance being Al and impurities)

[0178]

[0179] Table 4: Preliminary composition of the surface layer in the comparative experiment (wt%, balance being Al and impurities).

[0180]

[0181]

[0182] As can be seen from the table above, in the comparative experiment, Comparative Example 4 used a lower content of Mg and Zn elements compared to Example 1; in Comparative Example 5, a lower level of Si element content was used in the core layer compared to Example 2, while the outer coating layer had a higher Si content compared to the Example; and Comparative Example 6 used a higher content of Fe in the core and Fe in the outer aluminum alloy compared to the Example.

[0183] Next, bending angle (α), coating adhesion (Ad), and other relevant elongation and tensile strength tests were performed on the metal composite samples of the examples and comparative examples. The test results are shown in Table 5 below.

[0184] Table 5: Relevant Mechanical Property Tests of Examples and Comparative Samples

[0185]

[0186]

[0187] The test comparisons of the embodiment schemes and comparative experiments show that the alloy products obtained from the composite metal materials suitable for UAVs in the embodiments of the present invention achieve superior characteristics in bending angle and surface adhesion tests. The inventors are not bound by any theoretical explanation, but believe that the above characteristics are related to the core layer, aluminum alloy composition, intermediate layer configuration, and rolling process used in the present invention. Compared to products without a Zn intermediate layer, the products in the embodiments correspondingly achieve smaller bending angles and surface adhesion characteristics. This is related to the fact that the Zn intermediate layer partially or completely penetrates upwards during the hot rolling process to form more ZnMg compounds. The inventors believe that the ZnMg composite crystalline phase is beneficial to increasing the grain elongation and bending of the aluminum alloy composite product, while the transition fusion of Zn also strengthens the strength of the surface aluminum alloy coating. It is worth noting that when the Zn layer is too thick (as in Comparative Example 2), the surface Al alloy layer will show significant slippage in the adhesion test, leading to adhesion degradation. This is related to the soft properties of the Zn layer itself. Therefore, in the composite metal material products of this invention, an independent and continuous Zn layer may not exist between the final aluminum alloy core layer and the aluminum alloy outer cladding layer. If an intermediate Zn layer exists, it may exist in a trace amount between the aluminum alloy core layer and the aluminum alloy surface layer, with a maximum thickness of less than 0.5 μm, in a continuous or discontinuous manner. Furthermore, when the Mg and Zn content in the aluminum alloy composite material is excessively reduced (e.g., Comparative Example 4), the inventors found that the bending angle test was significantly inferior to the examples. However, when the Fe or Si content was too high (Comparative Examples 5 and 6), the toughness and bending angle performance were insufficient. This may be related to the formation of bulk hard compound intermediate phases by Si and Fe in the aluminum alloy. Moreover, higher initial and secondary hot rolling temperatures significantly improve the adhesion of the alloy layer on the strip surface and the surface bending resistance.

[0188] Application examples

[0189] Figure 5The diagram schematically depicts a load-bearing frame for an unmanned aerial vehicle (UAV) fuselage manufactured from a composite metal material according to the present invention, including side beam members 800 and connecting members 900. This load-bearing frame shape and structure are typically suitable for the central connecting beam of a UAV. In small and medium-sized UAVs, the vertical and horizontal spans of this frame are typically less than 50 cm, or even less than 30 cm. This component can be constructed using the aluminum alloy-based composite material of the present invention, and can be manufactured through appropriate forging, drawing, and bending processes. In the field of UAV applications, due to the limitations of their fuselage size and the frequent operation under harsh conditions (e.g., UAVs used in forest fire fighting or earthquake relief scenarios), fuselage components need to undergo large-angle bending and simultaneously withstand large loads (such as the large-angle bending portions in the load-bearing frame). Furthermore, in superior products, the surface layer of the component is required not to peel or crack under prolonged harsh environmental conditions (e.g., acid and alkali corrosion, relatively high temperatures). The metal composite material of the embodiments of the present invention effectively achieves and improves these characteristics suitable for UAV components.

[0190] Based on the embodiments and technical content described in this specification, the present invention can provide at least the following technical solutions: Although this disclosure includes specific embodiments, it will be apparent to those skilled in the art that various substitutions or changes in form and detail can be made to these embodiments without departing from the inventive spirit and scope of the claims and their equivalents. The embodiments described herein should be considered illustrative only and not for limiting purposes. The description of features and aspects in each embodiment is considered applicable to similar features and aspects in other embodiments. Therefore, the scope of this disclosure should not be limited by the specific description, but rather by the technical solutions of the claims, and all variations within the scope of the claims and their equivalents are to be interpreted as included within the technical solutions of this disclosure.

Claims

1. A composite metal material applicable to a drone, characterized by, The composite metal material includes a core layer portion composed of an aluminum-based alloy, and a surface layer aluminum alloy portion provided on both upper and lower surfaces of the core layer portion, wherein the core layer portion composed of the aluminum-based alloy has the following composition represented by weight %: 0.8%≤Mg≤1.2%, 0.5%≤Si≤0.8%, Fe≤0.3%, Cu≤0.1%, Mn≤0.1%, Cr≤0.1%、 0.2%≤Zn≤0.4%, Ti≤0.1%, the remainder being Al and inevitable impurities; and The surface layer aluminum alloy portion has the following alloy composition shown by weight %: Si≤0.20%, Fe≤0.3%, Cu≤0.1%, Mn≤0.10%, 0.8%≤Mg≤1.5%, Cr≤0.1%、 0.6%≤Zn≤1.2%; the remainder being Al and inevitable impurities; and There is also an intermediate Zn layer between the core layer portion composed of the aluminum-based alloy and the surface layer aluminum alloy portion, the intermediate Zn layer being present in a continuous or discontinuous state between the core layer portion composed of the aluminum-based alloy and the surface layer aluminum alloy portion, the maximum thickness of the intermediate Zn layer being less than 1 micron; And wherein the composite metal material applicable to the unmanned aerial vehicle is prepared by the following method: Step 1) Casting aluminum alloy blank An aluminum-based alloy ingot is obtained by a casting process, and a cast aluminum alloy blank is obtained from the ingot, the cast aluminum alloy blank having the following components represented by weight % composition: 0.8%≤Mg≤1.2%, 0.5%≤Si≤0.8%, Fe≤0.3%, Cu≤0.1%, Mn≤0.1%, Cr≤0.1%、 0.2%≤Zn≤0.4%, Ti≤0.1%, the remainder being Al and inevitable impurities; Step 2) Homogenizing the cast aluminum alloy blank The cast aluminum alloy blank obtained in step 1) is subjected to homogenization treatment in a melting furnace at a homogenization temperature of 550 to 560°C for 1 to 2 hours to obtain a homogenized cast aluminum alloy blank; Step 3) Forming a preliminary surface layer aluminum alloy portion The homogenized cast aluminum alloy blank is subjected to degreasing treatment, and the blank is placed in a sodium hydroxide solution with a concentration of 50-100g / L at 50-60°C to remove the surface Al oxide film; subsequently, the surface treated cast aluminum alloy blank is washed with pure water, and is placed in a zinc sulfate solution with a concentration of 50 to 150g / L for zinc deposition treatment for 1 to 10 minutes, replacing the intermediate Zn layer and depositing it on the surface of the cast aluminum alloy blank, the thickness of the intermediate Zn layer being 1 to 5 microns; A preliminary surface layer aluminum alloy portion is applied to the surface of the cast aluminum alloy blank with the deposited intermediate Zn layer, the preliminary surface layer aluminum alloy portion having the following composition shown by weight %: Si≤0.20%, Fe≤0.3%, Cu≤0.1%, Mn≤0.10%, 0.8%≤Mg≤1.5%, Cr≤0.1%、 0.5%≤Zn≤1.0%; the remainder being Al and inevitable impurities, The thickness of the applied preliminary surface layer aluminum alloy portion is 1mm to 2mm; Step 4) Hot rolling process The cast aluminum alloy billet obtained in step 3) is fed into a hot rolling mill for 4 to 6 passes of hot rolling. In the first two passes, the hot rolling temperature is maintained at 580°C to 600°C. Maintain a temperature of 460°C or higher before the cast aluminum alloy billet enters the penultimate hot rolling pass; Next, the hot-rolled billet that has formed the preliminary hot-rolled strip is cooled down using a cooling device, gradually cooled to a temperature of 180 to 200 ℃, and then rolled to obtain hot-rolled composite metal strip. Step 5) Cold rolling process The hot-rolled composite metal strip obtained in step 4) above is fed into a cold rolling equipment for cold rolling, and one or more passes of cold rolling are performed to obtain a cold-rolled composite metal strip. Step 6) Solution annealing The cold-rolled composite metal strip obtained in step 5) above is fed into an annealing furnace for annealing. The annealing temperature is controlled at 620 to 630°C, and the annealing time is controlled at 20 to 40 seconds. It is then cooled to 200 to 250°C and wound to obtain a composite metal material applicable to drones. The composite metal material applicable to drones includes a core layer and a final surface aluminum alloy layer on the surface of the core layer, the core layer having a thickness of 4 to 9 mm and the final surface aluminum alloy layer having a thickness of 0.5 to 1 mm.

2. The composite metal material applicable to a drone according to claim 1, characterized in that, A portion of the Zn composition in the final surface aluminum alloy portion originates from the intermediate Zn layer.

3. The composite metal material applicable to drones according to claim 1, wherein the thickness of the composite metal material is 5 mm to 10 mm.

4. A method of manufacturing a composite metal material applicable to a drone, characterized by, The method includes the following steps: Step 1) Cast aluminum alloy blanks An aluminum-based alloy ingot is obtained using a casting process, and a cast aluminum alloy billet is obtained from the ingot. The cast aluminum alloy billet has the following composition expressed as a percentage by weight: 0.8%≤Mg≤1.2%, 0.5%≤Si≤0.8%, Fe≤0.3%, Cu≤0.1%, Mn≤0.1%, Cr≤0.1%、 0.2%≤Zn≤0.4%, Ti≤0.1%, Apart from the components mentioned above, the remainder consists of Al and unavoidable impurities; Step 2) Homogenize and cast aluminum alloy billets The cast aluminum alloy billet obtained in step 1) is homogenized in a melting furnace at a homogenization temperature of 550 to 560°C for 1 to 2 hours to obtain a homogenized cast aluminum alloy billet. Step 3) Forming the initial surface aluminum alloy portion The homogenized cast aluminum alloy billet is degreased and placed in a sodium hydroxide solution with a concentration of 50-100 g / L at 50-60°C to remove the Al oxide film on the surface. Subsequently, the surface of the surface-treated cast aluminum alloy billet is washed with pure water and placed in a zinc sulfate solution with a concentration of 50-150 g / L for zinc precipitation treatment for 1 to 10 minutes to displace the intermediate Zn layer deposited on the surface of the cast aluminum alloy billet. The thickness of the intermediate Zn layer is 1 to 5 micrometers. A preliminary surface aluminum alloy portion is applied to the surface of a cast aluminum alloy blank having an intermediate Zn layer deposited thereon. The preliminary surface aluminum alloy portion has the following composition, shown in weight percent: Si≤0.20%, Fe≤0.3%, Cu≤0.1%, Mn≤0.10%, 0.8%≤Mg≤1.5% Cr≤0.1%、 0.5%≤Zn≤1.0%; The remainder consists of Al and unavoidable impurities. The thickness of the initial surface aluminum alloy layer applied is 1 mm to 2 mm; Step 4) Hot rolling process The cast aluminum alloy billet obtained in step 3) is fed into a hot rolling mill for 4 to 6 passes of hot rolling. In the first two passes, the hot rolling temperature is maintained at 580°C to 600°C. Maintain a temperature of 460°C or higher before the cast aluminum alloy billet enters the penultimate hot rolling pass; Next, the hot-rolled billet that has formed the preliminary hot-rolled strip is cooled down using a cooling device, gradually cooled to a temperature of 180 to 200 ℃, and then rolled to obtain hot-rolled composite metal strip. Step 5) Cold rolling process The hot-rolled composite metal strip obtained in step 4) above is fed into a cold rolling equipment for cold rolling, and one or more passes of cold rolling are performed to obtain a cold-rolled composite metal strip. Step 6) Solution annealing The cold-rolled composite metal strip obtained in step 5) above is fed into an annealing furnace for annealing. The annealing temperature is controlled at 620 to 630°C, and the annealing time is controlled at 20 to 40 seconds. It is then cooled to 200 to 250°C and wound to obtain a composite metal material applicable to drones. The composite metal material applicable to drones includes a core layer portion made of an aluminum-based alloy and a final surface aluminum alloy portion located on the surface of the core layer portion, wherein the thickness of the core layer portion is 4 to 9 mm and the thickness of the final surface aluminum alloy portion is 0.5 to 1 mm. An intermediate Zn layer exists between the core layer composed of an aluminum-based alloy and the surface aluminum alloy layer. The intermediate Zn layer exists between the core layer composed of an aluminum-based alloy and the surface aluminum alloy layer in a continuous or discontinuous state, and the maximum thickness of the intermediate Zn layer is less than 1 micrometer.

5. The method for manufacturing a composite metal material applicable to unmanned aerial vehicles according to claim 4, characterized in that, The final surface aluminum alloy portion of the composite metal material applicable to drones has the following composition: Si≤0.20%, Fe≤0.3%, Cu≤0.1%, Mn≤0.10%, 0.8%≤Mg≤1.5% Cr≤0.1%、 0.6%≤Zn≤1.2%.

6. The method for manufacturing a composite metal material applicable to unmanned aerial vehicles according to claim 4, characterized in that, The intermediate Zn layer exists between the core layer and the final surface aluminum alloy layer, either continuously or discontinuously, with a maximum thickness of less than or equal to 0.5 μm.

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