Metal-plastic composite structure, preparation method therefor and application thereof

Abstract

A plastic composite structure, a preparation method therefor and an application thereof. The plastic composite structure comprises: a first metal layer and a second metal layer which are stacked and connected to each other, wherein the first metal layer and the second metal layer are made of different materials; and a first oxide film layer and a first plastic layer which are sequentially stacked on the surface of the first metal layer that is not connected to the second metal layer, and / or a second oxide film layer and a second plastic layer which are sequentially stacked on the surface of the second metal layer that is not connected to the first metal layer. The first oxide film layer comprises a plurality of first nanopores, and the minimum distance between two adjacent first nanopores is less than or equal to 50 nm; and / or the second oxide film layer comprises a plurality of second nanopores, and the minimum distance between two adjacent second nanopores is less than or equal to 50 nm.

Description

Metal-plastic composite structures, their preparation methods and applications

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202410721056.X, filed on June 4, 2024, entitled "Metal-Plastic Composite Structure and Preparation Method Thereof and Application", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of materials, specifically to metal-plastic composite structures, their preparation methods, and applications. Background Technology

[0004] Currently, to simultaneously meet the requirements of high strength and lightweight, electronic device housings are made of composite metals. However, since metal can shield signals, it is necessary to create slots in the metal housing for injection molding to solve the signal shielding problem. In related technologies, to improve the bonding ability between metal and plastic, the metal surface is usually treated to form holes, and then a plastic layer is formed on the metal surface through injection molding. However, for composite metal housings, the performance differences between different metals increase the difficulty of surface treatment, making industrialization difficult. Therefore, there is a need for a metal-plastic composite structure solution that is simple to manufacture and can achieve a strong bond between composite metal and plastic. Summary of the Invention

[0005] In view of this, this application provides a metal-plastic composite structure, its preparation method and application. In this metal-plastic composite structure, the bonding force between the metal layer and the plastic layer is strong, which is beneficial to improving its application reliability. Moreover, the preparation process of this composite structure is simple and conducive to industrialization.

[0006] In a first aspect, this application provides a metal-plastic composite structure, including a first metal layer and a second metal layer interconnected, wherein the first metal layer and the second metal layer are metal layers of different materials; the first metal layer and the second metal layer satisfy at least one of the following:

[0007] (a) It further includes a first oxide film layer and a first plastic layer sequentially stacked on the surface of the first metal layer that is not connected to the second metal layer; the first oxide film layer contains a first metal oxide, wherein at least one metal element in the first metal oxide is the same as at least one metal element in the first metal layer;

[0008] (b) further includes a second oxide film layer and a second plastic layer sequentially stacked on the surface of the second metal layer that is not connected to the first metal layer; at least one metal element in the second metal oxide is the same as at least one metal element in the second metal layer.

[0009] The first oxide film layer and the second oxide film layer may be the same as or different from each other; and the first oxide film layer and the second oxide film layer satisfy at least one of the following:

[0010] (α) The first oxide film layer includes a plurality of first nanopores, and the shortest distance between two adjacent first nanopores is less than or equal to 50 nm;

[0011] (β) The second oxide film layer includes a plurality of second nanopores, and the shortest distance between two adjacent second nanopores is less than or equal to 50 nm.

[0012] In some embodiments, the metal element in the first metal oxide is the same as the metal element in the first metal layer.

[0013] In some embodiments, the metal element in the second metal oxide is the same as the metal element in the second metal layer.

[0014] In some embodiments, the first metal layer has a first surface and a second surface disposed opposite to each other, the second metal layer has a third surface and a fourth surface disposed opposite to each other, the second surface and the third surface are bonded and connected to each other, the first surface has a first oxide film layer and a first plastic layer stacked together, and the fourth surface has a second oxide film layer and a second plastic layer stacked together.

[0015] In some embodiments, a first oxide film layer and a first plastic layer are sequentially stacked on the side surface of the first metal layer, and a second oxide film layer and a second plastic layer are sequentially stacked on the side surface of the second metal layer.

[0016] In some embodiments, the first metal layer has a first surface and a second surface disposed opposite to each other, the second metal layer has a third surface and a fourth surface disposed opposite to each other, the second surface is bonded and connected to the third surface, and the first surface and the fourth surface satisfy at least one of the following:

[0017] (i) The first surface has a first oxide film layer and a first plastic layer stacked together;

[0018] (ii) The fourth surface has a second oxide film layer and a second plastic layer stacked together.

[0019] In some embodiments, the material of the first metal layer includes titanium or a titanium alloy, and the material of the second metal layer includes aluminum or an aluminum alloy.

[0020] In some embodiments, the average pore size of the first nanopore is 10nm-70nm, the average center-to-center distance between two adjacent first nanopores is less than or equal to 150nm, and the pore depth of the first nanopore is 100nm-1000nm.

[0021] In some embodiments, the average pore size of the second nanopore is 10nm-50nm, the average center-to-center distance between two adjacent second nanopores is less than or equal to 100nm, and the pore depth of the second nanopore is 100nm-3000nm.

[0022] In some embodiments, the difference between the average pore size of the first nanopore and the average pore size of the second nanopore is less than or equal to 30 nm.

[0023] In some embodiments, the porosity of the first oxide film layer is 20%-90%.

[0024] In some embodiments, the surface roughness Ra of the first oxide film layer on the side closest to the first plastic layer is 0.1 μm-20 μm.

[0025] In some embodiments, the thickness of the first oxide film layer is 100nm-1000nm.

[0026] In some embodiments, the porosity of the second oxide film layer is 20%-90%.

[0027] In some embodiments, the surface roughness Ra of the side of the second oxide film layer closest to the second plastic layer is 0.1 μm-50 μm.

[0028] In some embodiments, the thickness of the second oxide film is 100nm-3000nm.

[0029] In some embodiments, at least a portion of the first nanopore and at least a portion of the second nanopore are filled with plastic material.

[0030] In some embodiments, the thickness of the first plastic layer (14) is 0.1mm-200mm, and the thickness of the second plastic layer (16) is 0.1mm-200mm.

[0031] In some embodiments, the shear strength between the first plastic layer and the first metal layer is greater than or equal to 20 MPa.

[0032] In some embodiments, the shear strength between the second plastic layer and the second metal layer is greater than or equal to 25 MPa.

[0033] In some embodiments, a connecting layer is further included between the first metal layer and the second metal layer.

[0034] In some embodiments, the connecting layer comprises metal or resin.

[0035] In some embodiments, the thickness of the connecting layer is greater than or equal to 0.05 mm.

[0036] The metal-plastic composite structure provided in this application has strong bonding between the plastic layer and the metal layer, and high structural stability.

[0037] Secondly, this application provides a method for preparing a metal-plastic composite structure, comprising:

[0038] A composite metal material to be injection molded is provided, the composite metal material to be injection molded includes a third metal layer and a fourth metal layer that are interconnected;

[0039] The composite metal material to be injection molded is placed in a fluorine-containing electrolyte and subjected to anodizing treatment to obtain an oxidized composite metal material to be injection molded; the anodizing treatment achieves at least one of the following: (a) forming a first oxide film layer on the surface of the third metal layer that is not connected to the fourth metal layer, and (b) forming a second oxide film layer on the surface of the fourth metal layer that is not connected to the third metal layer.

[0040] The oxidized composite metal material to be injection molded is injection molded to obtain a metal-plastic composite structure; the injection molding of the oxidized composite metal material to be injection molded achieves at least one of the following: (a′) forming a first plastic layer on the surface of the first oxide film layer; (b′) forming a second plastic layer on the surface of the second oxide film layer to obtain a metal-plastic composite structure.

[0041] In some embodiments, the material of the third metal layer includes titanium or a titanium alloy, and the material of the fourth metal layer includes aluminum or an aluminum alloy.

[0042] In some embodiments, the fluorinated electrolyte includes fluorides and corrosion inhibitors.

[0043] In some embodiments, the fluoride includes at least one of potassium fluoride, sodium fluoride, ammonium fluoride, ammonium hydrogen fluoride, fluorozirconate, fluoroborate, hydrofluoric acid, fluorozironic acid, and fluoroboric acid.

[0044] In some embodiments, the corrosion inhibitor is an oxidizing corrosion inhibitor or a non-oxidizing corrosion inhibitor.

[0045] In some embodiments, the voltage of the anodizing treatment is 5V-50V, the time of the anodizing treatment is 1min-60min, and the temperature of the anodizing treatment is 5℃-80℃.

[0046] In some embodiments, the injection temperature is 200℃-500℃ and the injection pressure is 75MPa-300MPa.

[0047] The method for preparing the metal-plastic composite structure provided in this application is novel and the preparation process is simple, which can produce a metal-plastic composite structure with strong bonding between the metal layer and the plastic layer.

[0048] Thirdly, this application provides a method for preparing a metal composite structure, comprising: providing a composite metal material, wherein the composite metal material comprises a first metal layer and a second metal layer interconnected with each other; the first metal layer and the second metal layer are metal layers of different materials;

[0049] The composite metal material is placed in a fluorine-containing electrolyte and subjected to anodizing treatment to obtain an oxidized composite metal material to be injection molded; the anodizing treatment achieves at least one of the following: (a) a first oxide film is formed on the surface of the first metal layer that is not connected to the second metal layer; (b) a second oxide film is formed on the surface of the second metal layer that is not connected to the first metal layer; the first oxide film contains a first metal oxide, at least one metal element in the first metal oxide is the same as at least one metal element in the first metal layer, the second oxide film contains a second metal oxide, at least one metal element in the second metal oxide is the same as at least one metal element in the second metal layer, the first oxide film and the second oxide film are the same or different; and the first oxide film and the second oxide film satisfy at least one of the following: (α) the first oxide film includes a plurality of first nanopores, and the shortest distance between two adjacent first nanopores is less than or equal to 50 nm; (β) the second oxide film includes a plurality of second nanopores, and the shortest distance between two adjacent second nanopores is less than or equal to 50 nm.

[0050] The method for preparing the metal composite structure provided in this application is simple, has low preparation cost, and produces a metal composite structure with excellent performance.

[0051] Fourthly, this application provides the application of the metal-plastic composite structure described in the first aspect, the metal-plastic composite structure prepared by the preparation method described in the second aspect, or the metal composite structure prepared by the preparation method described in the third aspect in electronic devices, vehicles, and electrical appliances.

[0052] The metal-plastic composite structure provided in this application has a wide range of applications and is conducive to its commercial application.

[0053] Fifthly, this application provides a structural component, which includes the metal-plastic composite structure described in the first aspect, the metal-plastic composite structure prepared by the preparation method described in the second aspect, or the metal composite structure prepared by the preparation method described in the third aspect.

[0054] In some embodiments, the structural component includes an electronic device housing.

[0055] The structural components provided in this application have high structural stability, long service life, and low manufacturing cost, which is conducive to their large-scale application.

[0056] In a sixth aspect, this application provides an electronic device that includes the structural components described in the fifth aspect.

[0057] The electronic device provided in this application has good overall performance and strong product competitiveness. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0059] Figure 1 is a cross-sectional structural diagram of a metal-plastic composite structure provided in an embodiment of this application;

[0060] Figure 2 is a cross-sectional structural diagram of a metal-plastic composite structure provided in another embodiment of this application;

[0061] Figure 3 is a schematic diagram of the cross-sectional structure of the composite metal provided in one embodiment of this application;

[0062] Figure 4 is a schematic diagram of the concave-convex structure of the composite metal provided in one embodiment of this application;

[0063] Figure 5 is a metallographic characterization diagram of the cross-sectional morphology of the pit structure along the thickness direction of the composite metal in some embodiments of this application;

[0064] Figure 6 is an enlarged view of region A in Figure 1;

[0065] Figure 7 is a schematic diagram of the shear strength test principle of the metal-plastic composite structure provided in one embodiment of this application;

[0066] Figure 8 is a flowchart of the preparation method of the metal-plastic composite structure provided in one embodiment of this application;

[0067] Figure 9 is a scanning electron microscope image of the first oxide film layer of the metal-plastic composite structure prepared in Example 1 of this application;

[0068] Figure 10 is a cross-sectional scanning electron microscope image of the first oxide film layer of the metal-plastic composite structure prepared in Example 1 of this application;

[0069] Figure 11 is a scanning electron microscope image of the second oxide film layer of the metal-plastic composite structure prepared in Example 1 of this application;

[0070] Figure 12 is a cross-sectional scanning electron microscope image of the second oxide film layer of the metal-plastic composite structure prepared in Example 1 of this application. Detailed Implementation

[0071] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0072] Please refer to Figure 1, which is a schematic cross-sectional view of a metal-plastic composite structure provided in one embodiment of this application. The metal-plastic composite structure 100 includes a first metal layer 11 and a second metal layer 12 interconnected with each other, and a first oxide film layer 13 and a first plastic layer 14 sequentially stacked on the surface of the first metal layer 11 not connected to the second metal layer 12, and a second oxide film layer 15 and a second plastic layer 16 sequentially stacked on the surface of the second metal layer 12 not connected to the first metal layer 11. The first metal layer 11 and the second metal layer 12 are metal layers of different materials. The first oxide film layer 13 contains a first metal oxide, and at least one metal element in the first metal oxide is the same as at least one metal element in the first metal layer 11. The second oxide film layer 15 contains a second metal oxide, and at least one metal element in the second metal oxide is the same as at least one metal element in the second metal layer 12. The first oxide film layer 13 and the second oxide film layer 15 may be the same or different. The first oxide film layer 13 includes a plurality of first nanopores, and the shortest distance between two adjacent first nanopores is less than or equal to 50 nm. The second oxide film layer 15 includes a plurality of second nanopores, and the shortest distance between two adjacent second nanopores is less than or equal to 50 nm.

[0073] The metal-plastic composite structure provided in this application has a first metal layer and a second metal layer. The first metal layer and the second metal layer are made of different materials. The two layers are made of different metal materials. This composite material combines the performance advantages of different metal materials, which is conducive to the widespread use of metal-plastic composite structures. The first metal layer and the second metal layer satisfy at least one of the following: (a) the first metal layer has a first oxide film layer and a first plastic layer; (b) the surface of the second metal layer has a second oxide film layer and a second plastic layer. In addition, at least one of the first oxide film layer and the second oxide film layer has nanopores distributed in it. The nanopores are densely arranged and the oxide film layer has a large specific surface area, which is conducive to improving the bonding force between the first plastic layer and the first metal layer, the bonding force between the second plastic layer and the second metal layer, and improving the structural stability of the metal-plastic composite structure.

[0074] In the embodiment shown in Figure 1, the first metal layer has a first surface S1 and a second surface S2 disposed opposite to each other, the second metal layer has a third surface S3 and a fourth surface S4 disposed opposite to each other, the second surface S2 and the third surface S3 are bonded and connected to each other, the first surface S1 has a first oxide film layer 13 and a first plastic layer 14 stacked together, and the fourth surface S4 has a second oxide film layer 15 and a second plastic layer 16 stacked together.

[0075] In one embodiment of this application, an oxide film layer may be provided only on the surface of the first metal layer 11 or only on the surface of the second metal layer 12. In this case, the metal-plastic composite structure 100 includes a first metal layer 11 and a second metal layer 12 that are interconnected, and a first oxide film layer 13 and a first plastic layer 14 that are sequentially stacked on the surface of the first metal layer 11 that is not connected to the second metal layer 12; or the metal-plastic composite structure 100 includes a first metal layer 11 and a second metal layer 12 that are stacked, and a second oxide film layer 15 and a second plastic layer 16 that are sequentially stacked on the surface of the second metal layer 12 that is not connected to the first metal layer 11. In this embodiment, an oxide film layer can also be formed simultaneously on the surfaces of the first metal layer 11 and the second metal layer 12. In this case, the metal-plastic composite structure 100 includes the first metal layer 11 and the second metal layer 12 connected to each other, and a first oxide film layer 13 and a first plastic layer 14 sequentially stacked on the surface of the first metal layer 11 that is not connected to the second metal layer 12, and a second oxide film layer 15 and a second plastic layer 16 sequentially stacked on the surface of the second metal layer 12 that is not connected to the first metal layer 11. In some embodiments, an oxide film layer and a plastic layer are formed on the side surfaces of the first metal layer 11 and the second metal layer 12. Simultaneously, the first oxide film layer and the first plastic layer can be formed on the first surface S1, or the second oxide film layer and the second plastic layer can be formed on the fourth surface S4, or the first oxide film layer and the first plastic layer can be formed on the first surface S1, and the second oxide film layer and the second plastic layer can be formed on the fourth surface S4.

[0076] It should be noted that the specific shape and size of the first metal layer 11 and the second metal layer 12 in the embodiments of this application are not limited and can be designed according to actual needs. They can be regular shapes or irregular shapes. The first metal layer 11 can be a layer structure with equal or unequal thickness in all places, and the second metal layer 12 can be a layer structure with equal or unequal thickness in all places.

[0077] In this embodiment, the first oxide film layer and the first plastic layer may be sequentially connected to each other on the portion or all of the surface of the first metal layer that is not connected to the second metal layer, as needed; the second oxide film layer and the second plastic layer may be sequentially stacked on the portion or all of the surface of the second metal layer that is not connected to the first metal layer, as needed.

[0078] Please refer to Figure 2, which is a cross-sectional structural diagram of a metal-plastic composite structure provided in another embodiment of this application. The metal-plastic composite structure 100 includes a first metal layer 11 and a second metal layer 12 connected to each other, and includes a first oxide film layer 13 and a first plastic layer 14 sequentially stacked on the side of the first metal layer 11, or a second oxide film layer 15 and a second plastic layer 16 sequentially stacked on the side of the second metal layer 12, or a first oxide film layer 13 and a first plastic layer 14 sequentially stacked on the side of the first metal layer 11, and a second oxide film layer 15 and a second plastic layer 16 sequentially stacked on the side of the second metal layer 12. In the embodiment shown in Figure 2, the metal-plastic composite structure 100 also includes a first plastic layer 14 and a second plastic layer 16, and the first plastic layer 14 and the second plastic layer 16 are disposed adjacent to each other on the same side. In this case, the first plastic layer 14 and the second plastic layer 16 are an integral structure, and the first plastic layer 14 and the second plastic layer 16 are made of the same material.

[0079] In one embodiment of this application, the material of the first metal layer 11 includes titanium or a titanium alloy, and the material of the second metal layer 12 includes aluminum or an aluminum alloy. Titanium or titanium alloys have properties such as wear resistance, corrosion resistance, and low density, while aluminum or aluminum alloys have good thermal conductivity, are easy to process, and are low in cost, which is beneficial for improving the strength and lightweight of the metal-plastic composite structure. Specific titanium alloy grades can be, but are not limited to, TA1, TA2, TA3, TA4, TA5, T6, TA7, TA8, TB2, TB3, TB4, TB5, TB6, TC1, TC2, TC3, TC4, or TC6, etc.; aluminum alloy grades can be, but are not limited to, 1016, 1024, 5005, 5052, 6013, 6063, 6061, 7075, 7550, ADC10, ADC12, or GM55, etc. In one embodiment of this application, the material of the first metal layer can be TA5, and the material of the second metal layer can be 6061.

[0080] In one embodiment of this application, a connecting layer is further provided between the first metal layer and the second metal layer. The first metal layer, the connecting layer, and the second metal layer constitute a composite metal. Please refer to FIG3, which is a schematic cross-sectional view of the composite metal 200 provided in one embodiment of this application. The composite metal 200 provided in this application includes a first metal layer 11 and a second metal layer 12 stacked together, and a connecting layer 21 disposed between the first metal layer 11 and the second metal layer. In this embodiment of the application, the first metal layer 11 and the second metal layer 12 are different metal layers; the surface where the first metal layer 11 and the connecting layer 21 are joined has at least one uneven structure, or the surface where the second metal layer 12 and the connecting layer 21 are joined has at least one uneven structure, or the surface where the first metal layer 11 and the connecting layer 21 are joined has at least one uneven structure, and the surface where the second metal layer 12 and the connecting layer 21 are joined also has at least one uneven structure; wherein, the uneven structure includes at least one pit structure, or includes at least one protrusion structure, or includes at least one pit structure and at least one protrusion structure. The composite metal provided in this application includes a first metal layer and a second metal layer made of different materials, enabling the composite metal to possess both high strength and low weight, thereby improving its applicability in various fields, especially in electronic device housings. The composite metal of this application also includes a connecting layer between the first and second metal layers. Both the surfaces where the first metal layer and the connecting layer are bonded, and the surfaces where the second metal layer and the connecting layer are bonded, are provided with multiple uneven structures. These uneven structures in the connecting layer can be mechanically embedded into the first and second metal layers, thus tightly interlocking and bonding with them to form a firmly bonded composite metal whole. This significantly improves the bonding force between the first and second metal layers, extends the service life of the composite metal, and is more conducive to meeting the mechanical performance requirements of the composite metal during molding and processing in actual production applications. Furthermore, the connecting layer serves as a transition layer between the first metal layer and the second metal layer. The bonding surface of the connecting layer and the first and second metal layers is also provided with an uneven structure, which can effectively buffer the problems caused by the different fluidity of the two metal materials during the processing and forming process, such as uneven thickness of the first and second metal layers and unclear boundary line at the bonding interface. This effectively improves the comprehensive mechanical properties of the composite metal and broadens its application scenarios. For example, it can improve the forming limit of the R angle during stamping and forming, thereby forming an approximately right-angled structure.

[0081] In one embodiment of this application, the composite metal can be a metal processing raw material, which can be subsequently formed and processed according to actual usage requirements to obtain the corresponding product. In one embodiment of this application, the shape of the composite metal is not required; depending on different usage requirements, the composite metal can be, for example, sheet metal, profile, or casting. In one embodiment of this application, the sheet metal includes, but is not limited to, thick sheet metal, foil, and strip (coil).

[0082] Please refer to Figure 4, which is a schematic diagram of the uneven structure of the bonding surface between the connecting layer 21 and the first metal layer 11, or between the connecting layer 21 and the second metal layer 12, or between the connecting layer 21 and the first metal layer 11 and the connecting layer 21 and the second metal layer 12 in the composite metal 200 provided in this application; the uneven structure includes at least one pit structure, or at least one protrusion structure, or at least one pit structure and at least one protrusion structure. In some embodiments, a protrusion structure is formed between every two adjacent pit structures, and the pit structure and the protrusion structure are continuously arranged. In other embodiments, the pit structure and the protrusion structure are independently arranged structures, and the pit structure and the protrusion structure are not continuous.

[0083] In some embodiments, a protrusion is formed between every two adjacent recess structures. The distance D1 between two adjacent recess structures is the minimum straight-line distance between the edges of the two adjacent recess structures. In one embodiment of this application, the distance D1 between two adjacent recess structures is 0.1mm-0.5mm. A suitable distribution of recess structures can better facilitate the embedding of the concave-convex structure portion in the connecting layer into the first metal layer and the second metal layer, further enhancing the bonding force between the connecting layer and the first and second metal layers. Specifically, the distance D1 between two adjacent recess structures can be, but is not limited to, 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, or 0.5mm, etc.

[0084] In one embodiment of this application, the depth H of the recess structure is the absolute value of the difference between the vertical distance between the highest point of the protruding structure and the lowest point of the recess structure. In one embodiment, the depth H of the recess structure is 100μm-500μm. A suitable depth of the recess structure can improve the bonding performance between the connecting layer and the first metal layer and the second metal layer. Specifically, the depth H of the recess structure can be, but is not limited to, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, or 500μm. In one embodiment of this application, the lateral dimension D2 of the recess structure is 50μm-350μm. A suitable size of the recess structure can optimize the design of the concave-convex structure and improve the bonding force between the connecting layer and the first metal layer and the second metal layer. In this embodiment, the lateral dimension of the recess structure specifically refers to the diameter or side length of the cross-sectional shape of the recess structure in the direction perpendicular to the thickness of the composite metal. Specifically, the lateral dimension D2 of the pit structure can be, but is not limited to, 50μm, 100μm, 150μm, 200μm, 250μm, 300μm, or 350μm.

[0085] In one embodiment of this application, the cross-sectional shape of each recess structure along the thickness direction of the composite metal can be rectangular, trapezoidal, triangular, or T-shaped. In another embodiment of this application, the cross-sectional shapes of multiple recess structures in the composite metal along the thickness direction of the composite metal can be the same or different. As shown in Figure 5, in some embodiments of this application, the cross-sectional shape of the recess structure along the thickness direction of the composite metal can be rectangular, as shown in Figure 5(a), the rectangle can be a rectangle, as shown in Figure 5(b), the rectangle can be a square; in one embodiment of this application, as shown in Figure 5(c), the cross-sectional shape of the recess structure along the thickness direction of the composite metal can be triangular; in one embodiment of this application, as shown in Figure 5(d), the cross-sectional shape of the recess structure along the thickness direction of the composite metal can be T-shaped. When the cross-sectional shape is T-shaped, it is beneficial to form a "barb" structure at the interface between the connecting layer and the first metal layer and the second metal layer, thereby improving the bonding force between the connecting layer and the first metal layer and the second metal layer, and thus improving the bonding force between the first metal layer and the second metal layer.

[0086] As shown in Figure 3, the surface of the uneven structure is further provided with a nano-secondary structure. In some embodiments, the inner surface of at least one recessed structure is provided with a first nano-secondary structure, and the inner surface of the recessed structure includes the sidewalls and bottom surface of the recessed structure. In one embodiment of this application, the first nano-secondary structure includes a nanopore with a diameter of 50 nm-500 nm. Specifically, the diameter of the nanopore can be, but is not limited to, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, or 500 nm. In some embodiments, the outer surface of at least one raised structure is provided with a second nano-secondary structure, and the outer surface of the raised structure includes the sidewalls and top surface of the raised structure. In one embodiment of this application, the second nano-secondary structure includes a nanopore with a diameter of 50 nm-500 nm. Specifically, the diameter of the nanopores can be, but is not limited to, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, or 500nm. Further adding nano-secondary structures to the surface of the micron-scale uneven structure can optimize the design of the uneven structure, improve its surface roughness, and thus enhance the bonding force between the connecting layer and the first and second metal layers.

[0087] In one embodiment of this application, the surface roughness of the uneven structure is 10 μm-25 μm, that is, the surface roughness of the pit structure is 10 μm-25 μm, or the surface roughness of the protrusion structure is 10 μm-25 μm, or both the surface roughness of the pit structure and the surface roughness of the protrusion structure are 10 μm-25 μm. The surface roughness of the uneven structure is caused by the nanoscale secondary structure on the surface of the uneven structure. Controlling the surface roughness of the uneven structure within a suitable range can improve the bonding force between the first metal layer and the second metal layer.

[0088] In one embodiment of this application, the connecting layer 21 comprises a metal or a resin. In some specific embodiments, the metal may be, but is not limited to, at least one of magnesium and its alloys, aluminum and its alloys, zinc and its alloys, and copper and its alloys. When the connecting layer comprises a metal, the connection point is a different metal layer from the first metal layer, or the connecting layer is a different metal layer from the second metal layer, or the connecting layer, the first metal layer, and the second metal layer are all different metal layers. In other specific embodiments, the resin includes, but is not limited to, at least one of polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyamide (PA), polyphthalamide (PPA), polypropylene (PP), polycarbonate (PC), polyphenylene sulfone (PPSU), and polyetheretherketone (PEEK). In some embodiments, when the connecting layer material is aluminum or its alloy, while an oxide film layer and a plastic layer are provided on the sides of the first metal layer 11 and the second metal layer 12, the surface of the connecting layer has a third oxide film layer and a third plastic layer. The third oxide film layer includes a plurality of third nanopores, the average pore size of the third nanopores is 10nm-50nm, the pore depth of the third nanopores is 100nm-3000nm, and the total area of ​​the nanopores on the surface of the third oxide film layer near the third plastic layer accounts for 20%-90%. The third oxide film layer has a loose porous structure, and at least some of the third nanopores are filled with plastic material, which can improve the bonding force between the third plastic layer and the third metal layer, and is beneficial to improving the strength and reliability of the metal-plastic composite structure.

[0089] In one embodiment of this application, the connecting layer 21 comprises metal. The hardness of the connecting layer is in the ratio of the hardness of the lower of the first metal layer and the second metal layer to 1:(0.8-1.2). Since metals have lower hardness, their deformation resistance is correspondingly poorer, resulting in greater deformation under external force. Therefore, when the connecting layer is metal, this application controls the hardness of the connecting layer to be similar to the hardness of the lower of the connected metal layers. This minimizes the deformation difference between the connecting layer and the first and second metal layers, improves the deformation coordination between dissimilar metals, enhances the connection buffering effect of the connecting layer, and improves the bonding strength between the connecting layer and the first and second metal layers. Specifically, the ratio of the hardness of the connecting layer to the hardness of the lower of the first and second metal layers can be, but is not limited to, 1:0.8, 1:0.9, 1:1, 1:1.1, or 1:1.2, etc.

[0090] In one embodiment of this application, the ratio of the thermal expansion coefficient of the connecting layer 21 to the thermal expansion coefficient of the larger of the first metal layer 11 and the second metal layer 12 is 1:(0.8-1.2). The larger the thermal expansion coefficient of a metal, the greater its deformation when the temperature rises. Therefore, when the connecting layer is metal, this application controls the thermal expansion coefficient of the connecting layer to be similar to the thermal expansion coefficient of the larger of the connected metal layers. This reduces the deformation difference between the connecting layer and the first and second metal layers during heating, improves the deformation coordination between the dissimilar metals, and allows for better bonding between the connecting layer and the first and second metal layers during the preparation of the composite metal. This prevents peeling or cracking between the layers of the composite metal due to large differences in thermal expansion coefficients. In some specific embodiments, the ratio of the thermal expansion coefficient of the connecting layer to the thermal expansion coefficient of the larger of the first and second metal layers can be, for example, 1:0.8, 1:0.9, 1:1, 1:1.1, or 1:1.2. In one embodiment of this application, the first metal layer is a titanium alloy, the second metal layer is an aluminum alloy, and the coefficient of thermal expansion of the connecting layer is 2×10⁻⁶. -5 / K-2.7×10 -5 / K. Specifically, the coefficient of thermal expansion of the bonding layer can be, but is not limited to, 2 × 10⁻⁶. -5 / K, 2.1×10 -5 / K, 2.2×10 -5 / K, 2.3×10 -5 / K, 2.4×10 -5 / K, 2.5×10 -5 / K, 2.6×10 -5 / K or 2.7×10 -5 / K etc.

[0091] In some embodiments of this application, the connecting layer 21 is a different metal layer from the first metal layer 11 and the second metal layer 12; that is, the connecting layer is a different metal layer from the first metal layer and also a different metal layer from the second metal layer. In some embodiments of this application, the connecting layer and the first metal layer are different types of metal alloys, or the connecting layer and the second metal layer are different types of metal alloys, or the connecting layer, the first metal layer, and the second metal layer are all different types of metal alloys. In other embodiments of this application, the connecting layer and the first metal layer are the same type but different grades of metal alloys, or the connecting layer and the second metal layer are the same type but different grades of metal alloys, or the connecting layer, the first metal layer, and the second metal layer are all the same type but different grades of metal alloys. Since the connecting layer and the first and second metal layers are all different metal layers, a micrometer-scale intermetallic diffusion bonding layer formed by intermolecular thermal motion exists at the interface between the connecting layer and the first and second metal layers. This intermetallic diffusion layer simultaneously includes the connecting metal from the connecting layer and the first metal from the first metal layer or the second metal from the second metal layer. That is, using EDS (Energy Dispersive Spectroscopy), the elements of both the connecting metal and the first metal can be simultaneously measured at every point in the intermetallic diffusion layer between the connecting layer and the first metal layer, and the elements of both the connecting metal and the second metal can be simultaneously measured at every point in the intermetallic diffusion layer between the connecting layer and the second metal layer. The thickness of the intermetallic diffusion layer corresponds to the intermetallic diffusion depth, which is specifically the depth along the thickness direction of the composite metal. In one embodiment of this application, the intermetallic diffusion depth is 1μm-10μm. By controlling the intermetallic diffusion depth between the connecting layer and the first and second metal layers within a small range, this application can achieve better interfacial bonding performance between dissimilar metals, thereby improving the bonding force between dissimilar metals and enhancing the overall mechanical properties of the composite metal. This can improve the forming limit of the R-angle during stamping, thus forming an approximately right-angled structure. Simultaneously, it can also ensure uniform microstructure at the formed R-angle, resulting in a product with uniform color during subsequent anodizing and coloring, thus improving the product's aesthetics. Specifically, the intermetallic diffusion depth can be, for example, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, or 10μm.

[0092] In one embodiment of this application, the shear strength between the first metal layer 11 and the second metal layer 12 is greater than or equal to 100 MPa. This application significantly improves the bonding strength between the first and second metal layers by using a connecting layer and providing an uneven structure at the interface between the first and second metal layers and the connecting layer, thereby enhancing the overall mechanical properties of the composite metal, facilitating subsequent molding and processing, and extending the service life of the composite metal. Specifically, the bonding strength between the first and second metal layers can be, but is not limited to, 100 MPa, 105 MPa, 110 MPa, 120 MPa, 130 MPa, 150 MPa, 180 MPa, or 200 MPa. In some embodiments, the shear strength between the first metal layer and the connecting layer is greater than or equal to 100 MPa. In some embodiments, the shear strength between the second metal layer and the connecting layer is greater than or equal to 100 MPa.

[0093] In one embodiment of this application, the first metal layer 11 can be used as the outer metal layer of the shell, that is, as the outer surface metal layer exposed to the outside of the shell. In some specific embodiments, the first metal layer includes at least one of iron and its alloys, zirconium and its alloys, and titanium and its alloys. In some specific embodiments, the iron alloy includes an iron-carbon alloy, i.e., steel. In some specific embodiments, the elastic modulus of the first metal layer is 30 GPa-300 GPa, and the elastic modulus of the first metal layer is greater than that of the second metal layer. In some specific embodiments, the yield strength of the first metal layer is 100 MPa-1000 MPa, and the yield strength of the first metal layer is greater than that of the second metal layer. When the first metal layer is used as the outer surface metal layer exposed to the outside, controlling its elastic modulus and strength within a suitable range can provide better mechanical properties for the shell to withstand the impact of the shell encountering a sharp object or falling.

[0094] In one embodiment of this application, the second metal layer 12 can be used as an inner metal layer of the housing, that is, as a metal layer on the unexposed inner surface of the housing. In some specific embodiments, the second metal layer includes at least one selected from magnesium and its alloys, aluminum and its alloys, copper and its alloys, and zinc and its alloys. In some embodiments, the thermal conductivity of the second metal layer is 10 W·m. -1 ·k -1 -1000W·m -1 ·k -1 Furthermore, the thermal conductivity of the second metal layer is greater than that of the first metal layer. In some embodiments, the density of the second metal layer is greater than or equal to 1.2 g / cm³. 3Furthermore, the density of the second metal layer is less than that of the first metal layer. When the housing is an electronic device housing, the second metal layer, as an inner surface metal layer close to the interior of the electronic device, can provide better heat dissipation performance and reduce the overall weight of the housing by controlling its thermal conductivity and density within a suitable range.

[0095] In one embodiment of this application, the first metal layer 11 comprises a titanium alloy, the second metal layer 12 comprises a 6013 aluminum alloy, and the connecting layer 21 comprises an A380 aluminum alloy. Titanium alloys possess excellent mechanical properties. Using a titanium alloy as the first metal layer and employing the resulting composite metal as the equipment housing effectively protects the internal equipment. Furthermore, titanium alloys exhibit good wear resistance and corrosion resistance, which can extend the service life of the composite metal. Aluminum alloys have good thermal conductivity and low density. Using an aluminum alloy as the second metal layer and employing the resulting composite metal as the equipment housing effectively dissipates heat and reduces the overall weight of the housing. The A380 aluminum alloy has a similar hardness to the 6013 aluminum alloy; using it as the connecting layer between the titanium alloy first metal layer and the 6013 aluminum alloy second metal layer can improve the bonding strength between the first and second metal layers.

[0096] In one embodiment of this application, the first oxide film layer 13 is located close to the first metal layer 11. The first oxide film layer 13 comprises a first metal oxide, wherein at least one metal element in the first metal oxide is the same as at least one metal element in the first metal layer. In some embodiments, the metal element in the first metal oxide is the same as the metal element in the first metal layer.

[0097] In one embodiment of this application, the thickness of the first oxide film layer 13 is 100nm-1000nm. A suitable first oxide film layer 13 can improve the bonding ability between the first metal layer 11 and the first plastic layer 14. Specifically, the thickness of the first oxide film layer can be, but is not limited to, 100nm, 200nm, 400nm, 600nm, 800nm, or 1000nm. In one embodiment of this application, the thickness of the first oxide film layer can be 100nm-600nm. In another embodiment of this application, the thickness of the first oxide film layer can be 500nm-1000nm.

[0098] In one embodiment of this application, the total area of ​​nanopores on the surface of the first oxide film layer 13 near the first plastic layer 14 accounts for 20%-90%. The first oxide film layer has a loose porous structure, and the porosity of the first oxide film layer is characterized by the total area of ​​nanopores on the surface of the first oxide film layer near the first plastic layer. Here, nanopores are pores with a diameter less than or equal to 100 nm, specifically obtained by scanning the surface of the first oxide film layer near the first plastic layer using a scanning electron microscope (SEM). Suitable porosity can improve the bonding ability between the first metal layer and the first plastic layer, and improve the bonding ability of the metal-plastic composite structure. Specifically, the total area of ​​nanopores on the surface of the first oxide film layer near the first plastic layer can be, but is not limited to, 20%, 40%, 50%, 60%, 70%, 80%, or 90%. In one embodiment of this application, the total area of ​​nanopores on the surface of the first plastic layer in the first oxide film layer can be 20%-70%. In one embodiment of this application, the total area of ​​nanopores on the surface near the first plastic layer in the first porous oxide film layer can account for 60%-90%.

[0099] Please refer to Figure 6, which is an enlarged view of region A in Figure 1. It can be seen that the first oxide film layer 13 has an uneven surface. The surface roughness Ra of the side of the first oxide film layer near the first plastic layer is 0.1 μm-20 μm, increasing the specific surface area of ​​the surface of the first oxide film layer near the first plastic layer. An interlocking structure of unevenness is formed between the first plastic layer and the first oxide film layer, which is beneficial to improving the strength and reliability of the metal-plastic composite structure. Specifically, the surface roughness Ra of the side of the first oxide film layer near the first plastic layer can be, but is not limited to, 0.1 μm, 1 μm, 2 μm, 5 μm, 10 μm, 12 μm, 15 μm, or 20 μm. In one embodiment of this application, the surface roughness Ra of the side of the first oxide film layer near the first plastic layer can be 0.1 μm-10 μm. In another embodiment of this application, the surface roughness Ra of the side of the first oxide film layer near the first plastic layer can be 8 μm-20 μm.

[0100] In one embodiment of this application, the first oxide film layer 13 includes a plurality of first nanopores. The first nanopores are closely arranged in the first oxide film layer, and at least a portion of the first nanopores are filled with plastic material, which can improve the bonding force between the first plastic layer and the first metal layer. In some embodiments, all the first nanopores in the first oxide film layer are filled with plastic material. In other embodiments, at least a portion of the first nanopores are completely filled with plastic material, or at least a portion of the first nanopores are partially filled with plastic material.

[0101] In one embodiment of this application, the average pore size of the first nanopore is 10nm-70nm. A suitable pore size increases the specific surface area of ​​the first nanopore, promoting the entry of plastic and improving the adhesion between the first metal layer and the first plastic layer. Specifically, the average pore size of the first nanopore can be, but is not limited to, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, or 70nm. In one embodiment of this application, the average pore size of the first nanopore can be 10nm-50nm. In another embodiment of this application, the average pore size of the first nanopore can be 40nm-70nm.

[0102] In one embodiment of this application, the pore depth of the first nanopore is 100nm-1000nm. A suitable pore depth can improve the bonding ability between the first metal layer and the first plastic layer. Specifically, the pore depth of the first nanopore can be, but is not limited to, 100nm, 200nm, 400nm, 600nm, 800nm, or 1000nm. In one embodiment of this application, the pore depth of the first nanopore can be 100nm-600nm. In another embodiment of this application, the pore depth of the first nanopore can be 500nm-1000nm.

[0103] In this application, the shortest distance between two adjacent first nanopores is less than or equal to 50 nm. The shortest distance between two adjacent first nanopores is the shortest straight-line distance between the edge positions of the two adjacent first nanopores. Specifically, the shortest distance between two adjacent first nanopores can be, but is not limited to, less than or equal to 50 nm, less than or equal to 40 nm, less than or equal to 30 nm, less than or equal to 20 nm, or less than or equal to 10 nm. In one embodiment of this application, the shortest distance between two adjacent first nanopores can be less than or equal to 35 nm. In another embodiment of this application, the shortest distance between two adjacent first nanopores can be less than or equal to 20 nm.

[0104] In one embodiment of this application, the center-to-center spacing of adjacent first nanopores is less than or equal to 150 nm. Since the pore shape of the nanopores is approximately circular and / or elliptical, taking a circular shape as an example, the center-to-center spacing refers to the shortest distance between the centers of two adjacent first nanopores. The smaller this distance, the more densely packed the first nanopores are, which is beneficial for improving the bonding force between the first metal layer and the first plastic layer. Specifically, the center-to-center spacing of adjacent first nanopores can be, but is not limited to, less than or equal to 150 nm, less than or equal to 140 nm, less than or equal to 130 nm, less than or equal to 120 nm, less than or equal to 110 nm, or less than or equal to 100 nm. In one embodiment of this application, the center-to-center spacing of adjacent first nanopores can be less than or equal to 130 nm. In another embodiment of this application, the center-to-center spacing of adjacent first nanopores can be less than or equal to 110 nm.

[0105] In one embodiment of this application, the thickness of the first plastic layer 14 is 0.1mm-200mm. Specifically, the thickness of the first plastic layer can be, but is not limited to, 0.1mm, 10mm, 20mm, 40mm, 60mm, 80mm, 100mm, 150mm, 180mm, or 200mm. In one embodiment of this application, the thickness of the first plastic layer can be 0.1mm-80mm. In another embodiment of this application, the thickness of the first plastic layer can be 70mm-200mm. In some embodiments, the thickness and shape of the first plastic layer can be designed according to actual needs; it can be a regular shape or an irregular shape, and the first plastic layer can be a layer structure with uniform or unequal thickness throughout.

[0106] In one embodiment of this application, at least a portion of the first oxide film layer 13 is covered by the first plastic layer 14. That is, the covering method of the first plastic layer can be configured according to actual needs. Specifically, the first plastic layer may cover the entire first oxide film layer, or it may cover only a portion of the first oxide film layer.

[0107] In one embodiment of this application, the plastic material in the first plastic layer 14 is the same material as the plastic material in a portion of the first nanopores.

[0108] Please refer to Figure 7, which is a schematic diagram of the shear strength test principle of the metal-plastic composite structure provided in one embodiment of this application. The shear strength between the first plastic layer 14 and the first metal layer 11 is greater than or equal to 20 MPa, which improves the bonding ability between the first plastic layer 14 and the first metal layer 11. Specifically, the shear strength between the first plastic layer and the first metal layer can be, but is not limited to, greater than or equal to 20 MPa, greater than or equal to 22 MPa, greater than or equal to 24 MPa, greater than or equal to 26 MPa, greater than or equal to 28 MPa, or greater than or equal to 30 MPa. In one embodiment of this application, the shear strength between the first plastic layer and the first metal layer can be greater than or equal to 25.6 MPa. In another embodiment of this application, the shear strength between the first plastic layer and the first metal oxide layer can be greater than or equal to 27.5 MPa.

[0109] In one embodiment of this application, after the shear strength test, the residual area of ​​the first plastic layer on the surface of the first metal layer is greater than or equal to 95%. That is, the bonding force between the first plastic layer and the first metal layer is strong, and after the shear strength test, the first plastic layer and the first metal layer cannot be completely separated, with at least some plastic material remaining on the surface of the first metal layer. Specifically, after the shear strength test, the residual area of ​​the first plastic layer on the surface of the first metal layer can be, but is not limited to, greater than or equal to 95%, greater than or equal to 96%, greater than or equal to 97%, greater than or equal to 98%, or greater than or equal to 99%, etc. In one embodiment of this application, after the shear strength test, the residual area of ​​the first plastic layer on the surface of the first metal layer can be greater than or equal to 96%.

[0110] In one embodiment of this application, the second oxide film layer 15 is adjacent to the second metal layer 12. The second oxide film layer 15 comprises an oxide of the material of the second metal layer 12. The second oxide film layer 15 contains a second metal oxide, and at least one metal element in the second metal oxide is the same as at least one metal element in the second metal layer. In some embodiments, the metal element in the second metal oxide is the same as the metal element in the second metal layer.

[0111] In one embodiment of this application, the thickness of the second oxide film layer 15 is 100nm-3000nm. A suitable second oxide film layer 15 can improve the bonding ability between the second metal layer 12 and the second plastic layer 16. Specifically, the thickness of the second oxide film layer can be, but is not limited to, 100nm, 200nm, 800nm, 1000nm, 1800nm, 2000nm, 2800nm, or 3000nm. In one embodiment of this application, the thickness of the second oxide film layer can be 100nm-1800nm. In another embodiment of this application, the thickness of the second oxide film layer can be 1500nm-3000nm.

[0112] In one embodiment of this application, the total area of ​​nanopores on the surface of the second oxide film layer near the second plastic layer accounts for 20%-90%. The second oxide film layer has a loose porous structure, and the porosity of the second oxide film layer is characterized by the total area of ​​nanopores on the surface of the second oxide film layer near the second plastic layer. Here, nanopores are pores with a diameter less than or equal to 100 nm, specifically obtained by scanning the surface of the second oxide film layer near the second plastic layer using a scanning electron microscope (SEM). Suitable porosity can improve the bonding ability between the second metal layer and the second plastic layer, and improve the bonding ability of the metal-plastic composite structure. Specifically, the total area of ​​nanopores on the surface of the second oxide film layer near the second plastic layer can be, but is not limited to, 20%, 40%, 50%, 60%, 70%, 80%, or 90%. In one embodiment of this application, the total area of ​​nanopores on the surface of the first plastic layer in the second oxide film layer can be 20%-70%. In another embodiment of this application, the total area of ​​nanopores on the surface of the second porous oxide film layer near the first plastic layer can account for 60%-90%.

[0113] In one embodiment of this application, the second oxide film layer 15 has an uneven surface, and the surface roughness Ra of the side of the second oxide film layer near the second plastic layer is 0.1 μm-50 μm. This increases the specific surface area of ​​the surface of the second oxide film layer near the second plastic layer, forming an interlocking structure between the second plastic layer and the second oxide film layer, which is beneficial to improving the strength and reliability of the metal-plastic composite structure. Specifically, the surface roughness Ra of the side of the second oxide film layer near the second plastic layer can be, but is not limited to, 0.1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, or 50 μm. In one embodiment of this application, the surface roughness Ra of the side of the second oxide film layer near the second plastic layer can be 0.1 μm-30 μm. In another embodiment of this application, the surface roughness Ra of the side of the second oxide film layer near the second plastic layer can be 28 μm-50 μm.

[0114] In one embodiment of this application, the second oxide film layer 15 includes a plurality of second nanopores, which are closely arranged in the second oxide film layer. At least a portion of the second nanopores are filled with plastic material, which can improve the adhesion between the second plastic layer and the second metal layer. In some embodiments, all the second nanopores in the second oxide film layer are filled with plastic material. In other embodiments, at least a portion of the second nanopores are completely filled with plastic material, or at least a portion of the second nanopores are partially filled with plastic material.

[0115] In one embodiment of this application, the average pore size of the second nanopore is 10nm-50nm. A suitable pore size increases the specific surface area of ​​the second nanopore, promoting the entry of plastic and improving the adhesion between the first metal layer and the first plastic layer. Specifically, the average pore size of the second nanopore can be, but is not limited to, 10nm, 20nm, 30nm, 35nm, 40nm, 45nm, or 50nm. In one embodiment of this application, the average pore size of the second nanopore can be 10nm-35nm. In another embodiment of this application, the average pore size of the second nanopore can be 30nm-50nm.

[0116] In one embodiment of this application, the difference between the average pore size of the first nanopore and the average pore size of the second nanopore is less than or equal to 30 nm. Controlling the difference between the average pore sizes of the first and second nanopores can maintain similar specific surface areas between the first and second metal layers, improve the bonding ability between the plastic layer and the metal layer, and prevent an imbalance between the bonding ability between the first plastic layer and the first metal layer and between the second plastic layer and the second metal layer, which would lead to a decrease in the mechanical properties of the metal-plastic composite structure. Specifically, the difference between the average pore size of the first and second nanopores can be, but is not limited to, less than or equal to 30 nm, less than or equal to 28 nm, less than or equal to 25 nm, less than or equal to 22 nm, less than or equal to 20 nm, less than or equal to 17 nm, or less than or equal to 15 nm. In one embodiment of this application, the difference between the average pore size of the first and second nanopores can be less than or equal to 20 nm. In another embodiment of this application, the difference between the average pore size of the first and second nanopores can be less than or equal to 15 nm.

[0117] In one embodiment of this application, the depth of the second nanopore is 100nm-3000nm. A suitable depth can improve the bonding ability between the first metal layer and the first plastic layer. Specifically, the depth of the second nanopore can be, but is not limited to, 100nm, 200nm, 800nm, 1000nm, 1800nm, 2000nm, 2800nm, or 3000nm. In one embodiment of this application, the depth of the second nanopore can be 100nm-1600nm. In another embodiment of this application, the depth of the second nanopore can be 1500nm-3000nm.

[0118] In this application, the shortest distance between two adjacent second nanopores is less than or equal to 50 nm. The shortest distance between two adjacent second nanopores is the shortest straight-line distance between the edge positions of the two adjacent second nanopores. Specifically, the shortest distance between two adjacent second nanopores can be, but is not limited to, less than or equal to 50 nm, less than or equal to 40 nm, less than or equal to 30 nm, less than or equal to 20 nm, or less than or equal to 10 nm. In one embodiment of this application, the shortest distance between two adjacent second nanopores can be less than or equal to 35 nm. In another embodiment of this application, the shortest distance between two adjacent second nanopores can be less than or equal to 20 nm.

[0119] In one embodiment of this application, the average center-to-center spacing of adjacent second nanopores is less than or equal to 100 nm. Since the pore shape of the nanopores is approximately at least one of circular and elliptical shapes, taking a circular shape as an example, the center-to-center spacing refers to the distance between the centers of two adjacent second nanopores. The smaller this distance, the more densely packed the second nanopores are, which is beneficial for improving the bonding force between the second metal layer and the second plastic layer. Specifically, the average center-to-center spacing of adjacent second nanopores can be, but is not limited to, less than or equal to 150 nm, less than or equal to 140 nm, less than or equal to 130 nm, less than or equal to 120 nm, less than or equal to 110 nm, or less than or equal to 100 nm. In one embodiment of this application, the average center-to-center spacing of adjacent second nanopores can be less than or equal to 130 nm. In another embodiment of this application, the average center-to-center spacing of adjacent second nanopores can be less than or equal to 110 nm.

[0120] In one embodiment of this application, the thickness of the second plastic layer 16 is 0.1mm-200mm. Specifically, the thickness of the second plastic layer can be, but is not limited to, 0.1mm, 10mm, 20mm, 40mm, 60mm, 80mm, 100mm, 150mm, 180mm, or 200mm. In one embodiment of this application, the thickness of the second plastic layer can be 0.1mm-80mm. In another embodiment of this application, the thickness of the second plastic layer can be 70mm-200mm. In some embodiments, the thickness and shape of the second plastic layer can be designed according to actual needs; it can be a regular shape or an irregular shape, and the second plastic layer can be a layer structure with uniform or unequal thickness throughout.

[0121] In one embodiment of this application, at least a portion of the second oxide film layer is covered by the second plastic layer. That is, the covering method of the second plastic layer can be configured according to actual needs. Specifically, the second plastic layer may cover the entire second oxide film layer, or it may cover only a portion of the second oxide film layer.

[0122] In one embodiment of this application, the first plastic layer 14 and the second plastic layer 16 may be made of the same material or different materials.

[0123] In one embodiment of this application, the plastic material in the second plastic layer 16 is the same material as the plastic material in some of the second nanopores.

[0124] In one embodiment of this application, the shear strength between the second plastic layer 16 and the second metal layer 12 is greater than or equal to 25 MPa, which improves the bonding strength between the second plastic layer 16 and the second metal layer 12. Specifically, the shear strength between the second plastic layer and the second metal layer can be, but is not limited to, greater than or equal to 25 MPa, greater than or equal to 26 MPa, greater than or equal to 27 MPa, greater than or equal to 28 MPa, greater than or equal to 29 MPa, or greater than or equal to 30 MPa. In one embodiment of this application, the shear strength between the second plastic layer and the second metal layer can be greater than or equal to 25.6 MPa. In another embodiment of this application, the shear strength between the second plastic layer and the second metal layer can be greater than or equal to 28 MPa.

[0125] In one embodiment of this application, after the shear strength test, the residual area of ​​the second plastic layer on the surface of the second metal layer is greater than or equal to 95%. That is, the bonding force between the second plastic layer and the second metal layer is strong, and after the shear strength test, the second plastic layer and the second metal layer cannot completely separate, with at least some plastic material remaining on the surface of the second metal layer. Specifically, after the shear strength test, the residual area of ​​the second plastic layer on the surface of the second metal layer can be, but is not limited to, greater than or equal to 95%, greater than or equal to 96%, greater than or equal to 97%, greater than or equal to 98%, or greater than or equal to 99%, etc. In one embodiment of this application, after the shear strength test, the residual area of ​​the second plastic layer on the surface of the second metal layer can be greater than or equal to 96%.

[0126] Please refer to Figure 8, which is a flowchart of a method for preparing a metal-plastic composite structure according to an embodiment of this application, including:

[0127] S101: Provide a composite metal material to be injection molded, the composite metal material to be injection molded includes a third metal layer and a fourth metal layer that are interconnected;

[0128] S102: The composite metal material to be injection molded is placed in a fluorine-containing electrolyte and subjected to anodizing treatment to obtain an oxidized composite metal material to be injection molded; the anodizing treatment achieves at least one of the following: (a) forming a first oxide film layer on the surface of the third metal layer that is not connected to the fourth metal layer; (b) forming a second oxide film layer on the surface of the fourth metal layer that is not connected to the third metal layer.

[0129] S103: Injection molding is performed on the oxidized composite metal material to obtain a metal-plastic composite structure; the injection molding of the oxidized composite metal material to be injection molded achieves at least one of the following: (a′) forming a first plastic layer on the surface of the first oxide film layer; (b′) forming a second plastic layer on the surface of the second oxide film layer. The preparation method provided in this application can simultaneously form nanoporous oxide film layers on metal surfaces with different etching properties through only one anodizing treatment, shortening the preparation process, reducing preparation costs, and facilitating industrial production. The preparation method of the metal-plastic composite structure provided in this application is novel, with a simple process, mild conditions, simple surface treatment, and high bonding strength of the obtained metal-plastic composite structure.

[0130] In one embodiment of this application, the third metal layer of the composite metal material to be injection molded is a titanium alloy and the fourth metal layer is an aluminum alloy, and anodizing treatment is performed using a fluorine-containing electrolyte. In this case, the composite metal material to be injection molded serves as the anode. During the anodizing treatment, the main reaction on the surface of the third metal layer (titanium alloy) is Ti + 2H₂O - 4e⁻ = TiO₂ + 4H⁺. + A first oxide film layer, mainly composed of titanium oxide, is formed. On the surface of the fourth metal layer (aluminum alloy), the reaction 2Al + 3H₂O → 6e⁻ occurs. - =Al2O3 + 6H + A second oxide film, primarily composed of aluminum oxide, is formed. The fluorinated electrolyte contains fluoride ions, which react with hydrogen ions on the surface of the titanium oxide film to form hydrogen fluoride, exhibiting excellent etching effects and creating densely packed first nanopores within the first oxide film. While hydrofluoric acid has a weak etching effect on aluminum or aluminum alloys, the hydrogen ions generated during the formation of the aluminum oxide film have a strong etching effect, resulting in densely packed second nanopores within the second oxide film. Different etching principles are employed for the third and fourth metal layers, allowing for simultaneous pore formation in both layers, thus creating a nanoporous oxide film on the surfaces of the first and second metal layers of the composite metal material to be injection molded.

[0131] In one embodiment of this application, after the third metal layer in the injection-molded metal-plastic composite structure is anodized, the surface of the third metal layer is oxidized to form a first oxide film layer. At this time, the unoxidized portion of the third metal layer forms the first metal layer of the metal-plastic composite structure. Similarly, after the fourth metal layer in the injection-molded metal-plastic composite structure is anodized, the surface of the fourth metal layer is oxidized to form a first oxide film layer. At this time, the unoxidized portion of the fourth metal layer forms the second metal layer of the metal-plastic composite structure.

[0132] In one embodiment of this application, the material of the third metal layer may be, but is not limited to, titanium or titanium alloy, and the material of the fourth metal layer may be, but is not limited to, aluminum or aluminum alloy. Titanium or titanium alloy has properties such as wear resistance, corrosion resistance, and low density, while aluminum has good thermal conductivity, is easy to process, and has low cost, which is beneficial for improving the strength and lightweight of the metal-plastic composite structure. In one embodiment of this application, the material of the third metal layer may be TA5, and the material of the fourth metal layer may be 6061. In some embodiments, the third metal layer and the first metal layer are made of the same material, and the fourth metal layer and the second metal layer are made of the same material.

[0133] In one embodiment of this application, the fluorinated electrolyte includes a fluoride and a corrosion inhibitor, providing mild conditions that are beneficial for industrial production. Specifically, the fluoride may include, but is not limited to, at least one of potassium fluoride, sodium fluoride, ammonium fluoride, ammonium hydrogen fluoride, fluorozirconate, fluoroborate, hydrofluoric acid, fluorozironic acid, and fluoroboric acid. In one embodiment of this application, the fluoride may be potassium fluoride.

[0134] In one embodiment of this application, the concentration of fluoride ions in the fluorinated electrolyte is 0.5 g / L-10 g / L. Suitablely, the concentration of fluoride ions in the fluorinated electrolyte can be, specifically, but is not limited to, 0.5 g / L, 1 g / L, 2 g / L, 4 g / L, 6 g / L, 8 g / L, or 10 g / L. In one embodiment of this application, the concentration of fluoride ions in the fluorinated electrolyte can be 0.5 g / L-6 g / L. In another embodiment of this application, the concentration of fluoride ions in the fluorinated electrolyte can be 5 g / L-10 g / L.

[0135] In one embodiment of this application, the pH value of the fluorinated electrolyte is 2-12. Specifically, the pH value of the fluorinated electrolyte can be, but is not limited to, 2, 4, 6, 8, 10, or 12. In one embodiment of this application, the pH value of the fluorinated electrolyte can be 2-6. In another embodiment of this application, the pH value of the fluorinated electrolyte can be 7-12.

[0136] In one embodiment of this application, the corrosion inhibitor can slow down the etching rate of the metal layer, avoiding serious damage to the metal layer. The corrosion inhibitor is an oxidizing corrosion inhibitor or a non-oxidizing corrosion inhibitor. Specifically, the zinc oxide corrosion inhibitor may be, but is not limited to, at least one of chromates, dichromates, molybdates, tungstates, permanganates, hydrogen peroxide, ozone, hypochlorous acid, hypochlorite, and ferric ions. Non-oxidizing corrosion inhibitors include at least one of aldehydes, amines, organosulfur compounds, heterocyclic compounds, organic acids, and organic acid salts. Specifically, non-oxidizing corrosion inhibitors may be, but are not limited to, amino acids, benzotriazole, chitosan, hexadecylamine, quinoline, mercaptobenzothiazole, methylbenzotriazole, imidazoline, thiazoline, ethylenediaminetetraacetic acid and its salts, gluconate and its salts, malic acid and its salts, oxalic acid and its salts, citric acid and its salts, succinic acid and its salts, lactic acid and its salts, malonic acid and its salts, adipic acid and its salts, and diphenyl disulfide. In one embodiment of this application, when the corrosion inhibitor is an oxidizing corrosion inhibitor, the corrosion inhibitor may be potassium permanganate. In another embodiment of this application, when the corrosion inhibitor is a non-oxidizing corrosion inhibitor, the corrosion inhibitor may be malonic acid.

[0137] In one embodiment of this application, the fluorinated electrolyte further includes an additive, which includes at least one of a pH buffer and a surfactant. This additive can reduce the surface tension of the fluorinated electrolyte, improve wettability, and promote the consistency and uniformity of the anodizing reaction. Specifically, the pH buffer may include, but is not limited to, at least one of carbonates, bicarbonates, acetic acid and its salts, phosphoric acid and its salts, and pyrophosphate and its salts; the surfactant may include, but is not limited to, at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate, hexadecyltrimethylamine, and carboxymethyl cellulose. In one embodiment of this application, when the additive is a pH buffer, the additive can be phosphoric acid. In another embodiment of this application, when the additive is a surfactant, the additive can be sodium dodecyl sulfonate.

[0138] In one embodiment of this application, the fluorinated electrolyte further includes a solvent. Specifically, the solvent may be, but is not limited to, at least one selected from water, ethylene glycol, propylene glycol, glycerol, 1,3-butanediol, ethanol, and propanol. In one embodiment of this application, the solvent may be water and propylene glycol.

[0139] In one embodiment of this application, in the anodic oxidation process, a heterogeneous composite metal is used as the anode, and the cathode may be, but is not limited to, stainless steel, platinum, iridium, or a graphite plate. In one embodiment of this application, the cathode may be a graphite plate.

[0140] In one embodiment of this application, the voltage for anodizing is 5V-50V, the anodizing time is 1min-60min, and the anodizing temperature is 5℃-80℃. Suitable voltage, time, and temperature for anodizing can promote the formation of the oxide film layer and improve the bonding ability between the metal layer and the plastic layer. Specifically, the voltage for anodizing can be, but is not limited to, 5V, 15V, 25V, 35V, 45V, or 50V; the time for anodizing can be, but is not limited to, 1min, 10min, 20min, 30min, 40min, 50min, or 60min; and the temperature for anodizing can be, but is not limited to, 5℃, 15℃, 25℃, 45℃, 55℃, 65℃, 75℃, or 80℃. In one embodiment of this application, the voltage for anodizing can be 5V-40V, the time for anodizing can be 1min-40min, and the temperature for anodizing can be 5℃-60℃. In another embodiment of this application, the voltage for anodizing can be 35V-50V, the time for anodizing can be 30min-60min, and the temperature for anodizing can be 55℃-80℃.

[0141] In one embodiment of this application, the injection molding temperature is 200℃-500℃, and the injection molding pressure is 75MPa-300MPa, which can promote the plastic to enter the nanopores in the oxide film layer, thus improving the bonding force between the plastic layer and the metal layer. Specifically, the injection molding temperature can be, but is not limited to, 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, or 500℃; the injection molding pressure can be, but is not limited to, 75MPa, 100MPa, 150MPa, 200MPa, 250MPa, or 300MPa. In one embodiment of this application, the injection molding temperature can be 250℃-380℃, and the injection molding pressure can be 120MPa-200MPa, which is beneficial for improving the bonding force between the plastic layer and the metal layer. In another embodiment of this application, the injection molding temperature can be 350℃-500℃, and the injection molding pressure can be 175MPa-300MPa.

[0142] In one embodiment of this application, different molds can be used during injection molding according to actual usage needs, and the mold temperature is 80℃-350℃. Specifically, the mold temperature can be, but is not limited to, 80℃, 100℃, 120℃, 180℃, 200℃, 250℃, or 350℃. In one embodiment of this application, the mold temperature can be 130℃-230℃, which is beneficial to improving the injection molding effect. In another embodiment of this application, the mold temperature can be 200℃-350℃.

[0143] In one embodiment of this application, the injection molding material includes plastic and glass fiber. The plastic may include, but is not limited to, at least one of polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), acrylonitrile-styrene-butadiene copolymer (ABS), polyamide (PA), polyphthalamide (PPA), polypropylene (PP), polyethylene terephthalate (PET), polycarbonate (PC), polyphenylene sulfone resin (PPSU), polyaryletherketone (PEAK), and polyetheretherketone (PEEK). In one embodiment of this application, the injection molding material may be polybutylene terephthalate (PBT).

[0144] In one embodiment of this application, the mass percentage of glass fiber in the injection-molded material is less than or equal to 55%. Specifically, the mass percentage of glass fiber can be, but is not limited to, less than or equal to 55%, less than or equal to 50%, less than or equal to 45%, less than or equal to 40%, less than or equal to 35%, less than or equal to 30%, or less than or equal to 20%, etc. In one embodiment of this application, the mass percentage of glass fiber can be 40%.

[0145] In one embodiment of this application, a pretreatment is included before the anodizing process. The pretreatment includes degreasing, alkaline etching, sandblasting, chemical polishing, neutralization, and cleaning, which can remove surface impurities of heterogeneous composite metals, improve surface roughness, and facilitate the anodizing process.

[0146] In one embodiment of this application, the anodizing process further includes cleaning and baking, which can remove the fluorine-containing electrolyte remaining on the surface of the oxide film after the anodizing process, which is beneficial for injection molding.

[0147] This application also provides a method for preparing a metal composite structure, comprising: providing a composite metal material, the composite metal material comprising a third metal layer and a fourth metal layer interconnected; placing the composite metal material in a fluorine-containing electrolyte, and after anodizing treatment, forming a first oxide film layer on the surface of the third metal layer not connected to the fourth metal layer, and forming a second oxide film layer on the surface of the fourth metal layer not connected to the third metal layer, thereby obtaining an oxidized composite metal material to be injection molded; wherein the first metal layer and the second metal layer are metal layers of different materials; the first oxide film layer comprises a first metal oxide, wherein at least one metal element in the first metal oxide is the same as at least one metal element in the first metal layer; the second oxide film layer comprises a second metal oxide, wherein at least one metal element in the second metal oxide is the same as at least one metal element in the second metal layer; the first oxide film layer and the second oxide film layer may be the same as or different; the first oxide film layer comprises a plurality of first nanopores, wherein the shortest distance between two adjacent first nanopores is less than or equal to 50 nm; the second oxide film layer comprises a plurality of second nanopores, wherein the shortest distance between two adjacent second nanopores is less than or equal to 50 nm. The method for preparing the metal composite structure provided in this application is simple, has low preparation cost, and the resulting metal composite structure has excellent comprehensive performance.

[0148] This application provides a metal-plastic composite structure or metal composite structure for use in electronic devices, vehicles, and electrical appliances, which can improve the service life of electronic devices, vehicles, and electrical appliances and reduce their manufacturing costs.

[0149] This application also provides a structural component, which includes the metal-plastic composite structure described in any of the above embodiments, or the metal-plastic composite structure prepared by the preparation method described in any of the above embodiments, or the metal composite structure prepared by the preparation method described in any of the above embodiments. In one embodiment of this application, the structural component is an electronic device housing, including a mid-frame and a back cover. For example, it can be an electronic device mid-frame, wherein the first metal layer of the metal-plastic composite structure can be used as an inner metal layer of the housing near the inside of the electronic device, providing good heat dissipation performance for the housing and reducing the weight of the entire housing; the second metal layer provides the housing with better mechanical properties to withstand the impact of the housing encountering sharp objects or drops; the first oxide film layer can improve the bonding strength between the first metal layer and the first plastic layer, and / or the second oxide film layer can improve the bonding strength between the second metal layer and the second plastic layer, which is beneficial to improving the structural stability and service life of the electronic device housing. In some embodiments, the electronic device mid-frame and the electronic device back cover can be an integral structure or a separate structure.

[0150] This application also provides an electronic device that includes the structural components described in any of the above embodiments. The electronic device may be, for example, a mobile phone, a tablet computer, a laptop computer, a wearable device (watch, bracelet), a digital camera, etc.

[0151] The effects of the technical solution in this application will be further illustrated below with specific examples.

[0152] Example 1

[0153] Pretreatment (degreasing, alkaline etching, sandblasting, chemical polishing, neutralization treatment and ultrasonic cleaning) was carried out on a composite metal material to be injected with dimensions of 40mm×12mm×3mm (the first metal layer is TA4 titanium alloy and the second metal layer is 6013 aluminum alloy).

[0154] The composite metal material to be injection molded was used as the anode and anodized to obtain the oxidized composite metal material to be injection molded. The anodizing temperature was 40℃, the voltage was 30V, and the oxidation time was 15min. The electrolyte composition for the anodizing treatment was fluoride (10g / L potassium fluoride, fluoride ion concentration 3.3g / L), corrosion inhibitor (20g / L potassium permanganate), pH buffer (100g / L phosphoric acid), and the solvent was water.

[0155] After post-treatment (ultrasonic cleaning and drying) of the anodized composite metal material to be injection molded, PBT resin and glass fiber are used for injection molding, wherein the mass percentage of glass fiber is 40%, the injection temperature is 265℃, the mold temperature is 150℃, and a metal-plastic composite structure can be obtained after injection molding.

[0156] Example 2

[0157] The difference from Example 1 is that the electrolyte is fluoride (5 g / L potassium fluoride, fluoride ion concentration 1.6 g / L), 50 g / L potassium sodium tartrate, corrosion inhibitor (1 g / L sodium dodecylbenzene sulfonate), solvent is water and ethylene glycol in a mass ratio of 3:1, the anodizing temperature is 35°C, the anodizing voltage is 15 V, and the anodizing time is 15 min.

[0158] Example 3

[0159] The difference from Example 1 is that the first metal layer is TC4 titanium alloy and the second metal layer is 6063 aluminum alloy.

[0160] Example 4

[0161] The difference from Example 2 is that the first metal layer is TC4 titanium alloy and the second metal layer is 6063 aluminum alloy.

[0162] Comparative Example 1

[0163] The difference from Example 1 is that the electrolyte does not contain fluoride.

[0164] Performance testing

[0165] The metal-plastic composite structures prepared in Examples 1-4 and Comparative Example 1 were characterized by scanning electron microscopy to determine the pore size, pore depth, and spacing between adjacent pores in the first oxide film layer and the second oxide film layer. The results are shown in Table 1.

[0166] Figure 9 is a scanning electron microscope (SEM) image of the first oxide film layer of the metal-plastic composite structure prepared in Example 1 of this application; Figure 10 is a cross-sectional SEM image of the first oxide film layer of the metal-plastic composite structure prepared in Example 1 of this application; Figure 11 is a SEM image of the second oxide film layer of the metal-plastic composite structure prepared in Example 1 of this application; Figure 12 is a cross-sectional SEM image of the second oxide film layer of the metal-plastic composite structure prepared in Example 1 of this application. As can be seen from Figures 9-12, the first and second oxide film layers include multiple nanopores. The pore size of the first nanopore is 50 nm-70 nm, with an average pore size of 59 nm, and the thickness of the first oxide film layer is approximately 700 nm. The pore size of the second nanopore is 25 nm-45 nm, with an average pore size of 34 nm, and the thickness of the second oxide film layer is approximately 1350 nm. [0166.1][Correction 01.04.2025 according to detailed rule 91] As shown in Figures 9-12, Figure 9 shows the pore sizes of five nanopores in the first oxide film layer, where D11 indicates... S 54.92nm, D12 indicates S 62.68nm, D13 indicates S 52.97nm, D14 indicates S 63.41nm, D15 indicates S 59.50 nm. Figure 10 shows the thickness of the first oxide film at two points in its cross-section, respectively. S 730.0nm S 685.1 nm. Figure 11 shows the pore sizes of five nanopores in the second oxide film, denoted as D21. S 29.56nm, D22 indicates S 34.48nm, D23 indicates S 35.38nm, D24 indicates S 26.15nm, D25 indicates S 41.67 nm. Figure 12 shows the thicknesses at two points on the interface of the second oxide film, respectively. S 1.356μm S 1.365μm.

[0167] The bonding force between the first metal layer and the first oxide film layer of the metal-plastic composite structures prepared in Examples 1-4 and Comparative Example 1 were tested using a universal testing machine, and the results are shown in Table 2.

[0168] The bonding force between the second metal layer and the second oxide film layer of the metal-plastic composite structures prepared in Examples 1-4 and Comparative Example 1 were tested using a universal testing machine, and the results are shown in Table 2.

[0169] Table 1 Performance Test Results

[0170] Table 2 Mechanical property test results

[0171] As can be seen from Examples 1-4 and the comparative examples, the metal-plastic composite structure provided in this application exhibits good bonding between the metal layer and the plastic layer, resulting in high reliability. Examples 1 and 2 demonstrate that suitable preparation parameters can improve the bonding ability between the metal layer and the plastic layer. Examples 1 and 3-4 show that the anodizing method provided in this application can be used with various titanium alloys and aluminum alloys, exhibiting a wide range of applications. Examples 1 and Comparative Example 1 demonstrate that the use of a fluorinated electrolyte is necessary to simultaneously etch nanopores onto metal surfaces with different properties, while maintaining the bonding ability between the first metal layer and the first plastic layer, and between the second metal layer and the second plastic layer, within an appropriate range, which is beneficial for improving the reliability of the metal-plastic composite structure.

[0172] The above description represents the preferred embodiments of this application, but should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this application, and these improvements and modifications are also considered to be within the scope of protection of this application.

Claims

1. A metal-plastic composite structure, characterized in that, It includes a first metal layer (11) and a second metal layer (12) that are interconnected, wherein the first metal layer (11) and the second metal layer (12) are metal layers of different materials; the first metal layer (11) and the second metal layer (12) satisfy at least one of the following: (a) It further includes a first oxide film layer (13) and a first plastic layer (14) sequentially stacked on the surface of the first metal layer (11) that is not connected to the second metal layer (12); the first oxide film layer (13) contains a first metal oxide, wherein at least one metal element in the first metal oxide is the same as at least one metal element in the first metal layer (11); (b) further includes a second oxide film layer (15) and a second plastic layer (16) sequentially stacked on the surface of the second metal layer (12) that is not connected to the first metal layer (11); at least one metal element in the second metal oxide is the same as at least one metal element in the second metal layer (12). The first oxide film layer (13) is the same as or different from the second oxide film layer (15); and the first oxide film layer (13) and the second oxide film layer (15) satisfy at least one of the following: (α) The first oxide film layer (13) includes a plurality of first nanopores, and the shortest distance between two adjacent first nanopores is less than or equal to 50 nm; (β) The second oxide film layer (15) includes a plurality of second nanopores, and the shortest distance between two adjacent second nanopores is less than or equal to 50 nm.

2. The metal-plastic composite structure as described in claim 1, characterized in that, The metal element in the first metal oxide is the same as the metal element in the first metal layer (11).

3. The metal-plastic composite structure as described in claim 1 or 2, characterized in that, The metal element in the second metal oxide is the same as the metal element in the second metal layer (12).

4. The metal-plastic composite structure as described in any one of claims 1-3, characterized in that, The first metal layer (11) has a first surface and a second surface disposed opposite to each other, the second metal layer (12) has a third surface and a fourth surface disposed opposite to each other, the second surface and the third surface are bonded and connected to each other, the first surface has a first oxide film layer (13) and a first plastic layer (14) stacked together, and the fourth surface has a second oxide film layer (15) and a second plastic layer (16) stacked together.

5. The metal-plastic composite structure as described in any one of claims 1-3, characterized in that, The first metal layer (11) has a first oxide film layer (13) and a first plastic layer (14) stacked sequentially on its side, and the second metal layer (12) has a second oxide film layer (15) and a second plastic layer (16) stacked sequentially on its side.

6. The metal-plastic composite structure as described in claim 5, characterized in that, The first metal layer (11) has a first surface and a second surface disposed opposite to each other, and the second metal layer (12) has a third surface and a fourth surface disposed opposite to each other, the second surface being bonded and connected to the third surface, and the first surface and the fourth surface satisfying at least one of the following: (i) The first surface has a first oxide film layer (13) and a first plastic layer (14) stacked together; (ii) The fourth surface has a second oxide film layer (15) and a second plastic layer (16) stacked together.

7. The metal-plastic composite structure according to any one of claims 1-6, characterized in that, The material of the first metal layer (11) includes titanium or titanium alloy, and the material of the second metal layer (12) includes aluminum or aluminum alloy.

8. The metal-plastic composite structure according to any one of claims 1-7, characterized in that, The first nanopore and the second nanopore satisfy at least one of the following: (A) The average pore size of the first nanopore is 10nm-70nm, the average center-to-center distance between two adjacent first nanopores is less than or equal to 150nm, and the pore depth of the first nanopore is 100nm-1000nm. (B) The average pore size of the second nanopore is 10nm-50nm, the average center-to-center distance between two adjacent second nanopores is less than or equal to 100nm, and the pore depth of the second nanopore is 100nm-3000nm.

9. The metal-plastic composite structure as described in any one of claims 1-8, characterized in that, The difference between the average pore size of the first nanopore and the average pore size of the second nanopore is less than or equal to 30 nm.

10. The metal-plastic composite structure according to any one of claims 1-9, characterized in that, The porosity of the first oxide film layer (13) is 20%-90%, the surface roughness Ra of the side of the first oxide film layer (13) close to the first plastic layer (14) is 0.1μm-20μm, and the thickness of the first oxide film layer (13) is 100nm-1000nm.

11. The metal-plastic composite structure according to any one of claims 1-10, characterized in that, The porosity of the second oxide film layer (15) is 20%-90%, the surface roughness Ra of the side of the second oxide film layer (15) close to the second plastic layer (16) is 0.1μm-50μm, and the thickness of the second oxide film layer (15) is 100nm-3000nm.

12. The metal-plastic composite structure according to any one of claims 1-11, characterized in that, At least a portion of the first nanopore and at least a portion of the second nanopore are filled with plastic material.

13. The metal-plastic composite structure according to any one of claims 1-12, characterized in that, The thickness of the first plastic layer (14) is 0.1mm-200mm, and the thickness of the second plastic layer (16) is 0.1mm-200mm.

14. The metal-plastic composite structure according to any one of claims 1-13, characterized in that, The shear strength between the first plastic layer (14) and the first metal layer (11) is greater than or equal to 20 MPa.

15. The metal-plastic composite structure according to any one of claims 1-14, characterized in that, The shear strength between the second plastic layer (16) and the second metal layer (12) is greater than or equal to 25 MPa.

16. The metal-plastic composite structure according to any one of claims 1-15, characterized in that, A connecting layer (21) is also provided between the first metal layer (11) and the second metal layer (12).

17. The metal-plastic composite structure as described in claim 16, characterized in that, The connecting layer (21) comprises metal or resin.

18. The metal-plastic composite structure as described in claim 16 or 17, characterized in that, The thickness of the connecting layer (21) is greater than or equal to 0.05 mm.

19. The method for preparing the metal-plastic composite structure according to any one of claims 1-18, characterized in that, include: A composite metal material to be injection molded is provided, the composite metal material to be injection molded includes a third metal layer and a fourth metal layer that are interconnected; The composite metal material to be injection molded is placed in a fluorine-containing electrolyte and subjected to anodizing treatment to obtain an oxidized composite metal material to be injection molded; the anodizing treatment achieves at least one of the following: (a) forming a first oxide film layer (13) on the surface of the third metal layer that is not connected to the fourth metal layer, and (b) forming a second oxide film layer (15) on the surface of the fourth metal layer that is not connected to the third metal layer. The oxidized composite metal material to be injection molded is injection molded to obtain a metal-plastic composite structure; the injection molding of the oxidized composite metal material to be injection molded achieves at least one of the following: (a′) forming a first plastic layer (14) on the surface of the first oxide film layer (13); (b′) forming a second plastic layer (16) on the surface of the second oxide film layer to obtain a metal-plastic composite structure.

20. The preparation method according to claim 19, characterized in that, The material of the third metal layer includes titanium or titanium alloy, and the material of the fourth metal layer includes aluminum or aluminum alloy.

21. The preparation method according to claim 19 or 20, characterized in that, The fluorinated electrolyte includes fluorides and corrosion inhibitors; The fluoride includes at least one of potassium fluoride, sodium fluoride, ammonium fluoride, ammonium hydrogen fluoride, fluorozirconate, fluoroborate, hydrofluoric acid, fluorozirconic acid, and fluoroborate. The corrosion inhibitor is an oxidizing corrosion inhibitor or a non-oxidizing corrosion inhibitor.

22. The preparation method according to any one of claims 19-21, characterized in that, The voltage for the anodizing treatment is 5V-50V, the time for the anodizing treatment is 1min-60min, and the temperature for the anodizing treatment is 5℃-80℃.

23. The preparation method according to any one of claims 19-22, characterized in that, The injection temperature is 200℃-500℃, and the injection pressure is 75MPa-300MPa.

24. A method for preparing a metal composite structure, characterized in that, include: A composite metal material is provided, the composite metal material comprising a first metal layer (11) and a second metal layer (12) connected to each other; the first metal layer (11) and the second metal layer (12) are metal layers of different materials; The composite metal material is placed in a fluorine-containing electrolyte and subjected to anodizing treatment to obtain an oxidized composite metal material to be injection molded; the anodizing treatment achieves at least one of the following: (a) forming a first oxide film layer (13) on the surface of the first metal layer (11) not connected to the second metal layer (12); (b) forming a second oxide film layer (15) on the surface of the second metal layer (12) not connected to the first metal layer (11); the first oxide film layer (13) contains a first metal oxide, wherein at least one metal element in the first metal oxide is the same as at least one metal element in the first metal layer (11), and the second oxide film layer... (15) includes a second metal oxide, wherein at least one metal element in the second metal oxide is the same as at least one metal element in the second metal layer (12), and the first oxide film layer (13) is the same as or different from the second oxide film layer (15); and the first oxide film layer (13) and the second oxide film layer (15) satisfy at least one of the following: (α) the first oxide film layer (13) includes a plurality of first nanopores, and the shortest distance between two adjacent first nanopores is less than or equal to 50 nm; (β) the second oxide film layer (15) includes a plurality of second nanopores, and the shortest distance between two adjacent second nanopores is less than or equal to 50 nm.

25. The application of the metal-plastic composite structure according to any one of claims 1-18, the metal-plastic composite structure prepared by the preparation method according to any one of claims 19-23, or the metal composite structure prepared by the preparation method according to claim 24 in electronic devices, vehicles, and electrical appliances.

26. A structural component, characterized in that, The structural component includes the metal-plastic composite structure according to any one of claims 1-18, the metal-plastic composite structure prepared by the preparation method according to any one of claims 19-23, or the metal composite structure prepared by the preparation method according to claim 24.

27. The structural component as described in claim 26, characterized in that, The structural component includes an electronic device housing.

28. An electronic device, characterized in that, The electronic device includes the structural component as described in any one of claims 26-27.

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