Composite material, and preparation method therefor and use thereof

Abstract

The present invention relates to a composite material, and a preparation method therefor and the use thereof. The composite material comprises a substrate, and an anodic oxide film layer, a basic coating, a functional coating and a color coating, which are sequentially arranged on one surface of the substrate from inside to outside, wherein the functional coating comprises a plurality of first functional coatings and a plurality of second functional coatings, which are alternately arranged; and one first functional coating of the plurality of first functional coatings and one second functional coating of the plurality of second functional coatings meet one of the following conditions: metallic elements in the first functional coating are different from metallic elements in the second functional coating, or, the first functional coating contains metallic elements and the second functional coating does not contain metallic elements, the metallic elements being selected from one or more of Group IVB metals, Group VB metals, Group VIB metals and Group IVA metals.

Description

Composite material and its preparation method and application

[0001] This application claims priority to Chinese patent application No. 202410396077.9, filed on March 29, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present disclosure relates to the field of film coating, and in particular to a composite material and a preparation method and application thereof. Background Art

[0003] With the development of smart electronic products such as mobile phones and other fields, the demand for metal products such as stainless steel and aluminum alloys continues to grow. Stainless steel has good chemical stability and can be directly processed by PVD (Physical Vapor Deposition). For aluminum alloys, it is generally necessary to form an aluminum oxide film on the surface of the aluminum substrate.

[0004] Public content

[0005] The purpose of the present disclosure is to overcome the problems existing in the above-mentioned related technologies and provide a composite material with good wear resistance and corrosion resistance.

[0006] In order to achieve the above-mentioned purpose, the first aspect of the present disclosure provides a composite material, which includes a substrate and an anodized film layer, a basic coating layer, a functional coating layer and a color coating layer arranged on a surface of the substrate in sequence from the inside to the outside, the functional coating layer including a plurality of first functional coating layers and a plurality of second functional coating layers arranged alternately; a first functional coating layer in the plurality of first functional coating layers and a second functional coating layer in the plurality of second functional coating layers meet one of the following conditions: the metal element in the first functional coating layer is different from the metal element in the second functional coating layer; or, the first functional coating layer contains a metal element and the second functional coating layer does not contain a metal element; the metal element is selected from one or more of Group IVB metals, Group VB metals, Group VIB metals and Group IVA metals.

[0007] In some embodiments, the number of layers of the plurality of first functional coating layers and the number of layers of the plurality of second functional coating layers are each independently 2-10 layers.

[0008] In some embodiments, the number of layers of the plurality of first functional coating layers and the number of layers of the plurality of second functional coating layers are each independently 3-8 layers.

[0009] In some embodiments, the first functional coating layer and the second functional coating layer satisfy at least one of the following conditions: a thickness of the first functional coating layer is 100-300 nm; or a thickness of the second functional coating layer is 50-150 nm.

[0010] In some embodiments, the first functional coating layer includes a first element and a second element, the first element is selected from at least one of Cr, Ti, Zr, W, Nb, Mo, Ta or Ge, and the second element is selected from at least one of C or N.

[0011] In some embodiments, the first element in the first functional coating layer is partially or entirely the same as an element in the basic coating layer.

[0012] In some embodiments, the first functional coating layer further contains O element.

[0013] In some embodiments, the second functional coating layer is selected from one or more of an aluminum oxide layer, a silicon oxide layer, and a silicon nitride layer.

[0014] In some embodiments, the anodized film layer satisfies at least one of the following: the anodized film layer has a porous structure; the pore size of the pores in the anodized film layer is 15-35 nm; the porosity of the anodized film layer is 10%-20%; or the thickness of the anodized film layer is 5-15 μm.

[0015] In some embodiments, the substrate is an aluminum alloy; and the element of the base coating is selected from at least one of Cr, Ti, Zr, W, Nb, Mo, Ta, or Ge.

[0016] In some embodiments, the color coating includes a third element and an optional fourth element, the third element is selected from at least one of Cr, Ti, W, or Si, and the fourth element includes at least one of C or N.

[0017] In some embodiments, the base coating layer satisfies at least one of the following conditions: the thickness of the base coating layer is 100-300 nm; or the thickness of the color coating layer is 300-800 nm.

[0018] In some embodiments, the wear resistance of the composite material meets at least one of the following requirements: in the vibration wear test, the maximum vibration wear time when the wear test result is below level 1 is more than 4 hours; or the corrosion resistance of the composite material meets at least one of the following sub-requirements: in the water boiling test, the maximum water boiling treatment time when the cross-cut test result is below level 1 is more than 1.5 hours; in the neutral salt spray test, the maximum neutral salt spray treatment time when the cross-cut test result is below level 1 is more than 48 hours; or in the artificial sweat test, the maximum artificial sweat treatment time when the cross-cut test result is below level 1 is more than 96 hours.

[0019] A second aspect of the present disclosure provides a method for preparing a composite material, the method comprising: performing anodizing on a substrate to obtain a substrate with an anodized film layer attached thereto; performing physical vapor deposition on the substrate with the anodized film layer attached thereto; the physical vapor deposition comprising the following steps: performing a first magnetron sputtering on the substrate with the anodized film layer attached thereto to deposit a basic coating layer on the surface of the anodized film layer; performing a second magnetron sputtering and a third magnetron sputtering alternately on the basic coating layer multiple times to deposit a functional coating layer on the surface of the basic coating layer; the functional coating layer comprises a plurality of first functional coating layers and a plurality of second functional coating layers arranged alternately; performing a fourth magnetron sputtering on the surface of the functional coating layer to deposit a color coating layer on the surface of the functional coating layer; a first functional coating layer among the plurality of first functional coating layers and a second functional coating layer among the plurality of second functional coating layers satisfy one of the following conditions: the metal element in the first functional coating layer is different from the metal element in the second functional coating layer, or the first functional coating layer contains a metal element while the second functional coating layer does not contain a metal element; the metal element is selected from one or more of Group IVB metals, Group VB metals, Group VIB metals, and Group IVA metals.

[0020] In some embodiments, the anodization comprises the following steps: performing an anodization treatment in a sulfuric acid solution using graphite as a cathode and the substrate as an anode to obtain a substrate with the first anodized film layer attached thereto.

[0021] In some embodiments, the anodizing treatment time is 30-60 min; the voltage is 8-15 V; and the sulfuric acid concentration is 100-200 g / L.

[0022] In some embodiments, the anodizing further comprises: placing the substrate with the first anodized film layer attached thereto in a phosphoric acid solution for pore expansion treatment to obtain a substrate with a second anodized film layer formed thereon.

[0023] In some embodiments, the concentration of the phosphoric acid solution is 3-10 wt %; and the pore expansion treatment time is 2-10 min.

[0024] In some embodiments, the number of the plurality of second magnetron sputtering operations and the number of the plurality of third magnetron sputtering operations are each independently 2-10 times.

[0025] In some embodiments, the number of the plurality of second magnetron sputtering operations and the number of the plurality of third magnetron sputtering operations are each independently 3-8 times.

[0026] In some embodiments, the first magnetron sputtering, the second magnetron sputtering, the third magnetron sputtering and the fourth magnetron sputtering satisfy at least one of the following: the conditions of the first magnetron sputtering include: the target material is at least one of Cr, Ti, Zr, W, Nb, Mo, Ta or Ge; the conditions of the second magnetron sputtering include: the target material is at least one of Cr, Ti, Zr, W, Nb, Mo, Ta or Ge, and the reaction gas is one of nitrogen and acetylene; the conditions of the third magnetron sputtering include: the target material is one of Al and Si; the reaction gas is one of oxygen and nitrogen; or the conditions of the fourth magnetron sputtering include: the target material is at least one of Cr, Ti, W or Si; the reaction gas is at least one of nitrogen or acetylene.

[0027] In some embodiments, the metal elements of the first functional coating layer are partially the same as or completely the same as the metal elements of the base coating layer.

[0028] A third aspect of the present disclosure provides a shell, which includes the composite material provided by the first aspect of the present disclosure.

[0029] A fourth aspect of the present disclosure provides an electronic device, which includes the housing provided by the third aspect of the present disclosure.

[0030] Through the above-described technical solution, the composite material disclosed herein increases the longitudinal resistance of the functional coating layer by alternating multiple first and second functional coating layers, reducing galvanic corrosion during corrosion testing while maintaining the original performance of the film layer. The alternating arrangement of the first and second functional coating layers improves the density of the functional coating layer, reduces film defects, and enhances the corrosion resistance of the composite material. Furthermore, by pre-forming a self-grown anodic oxide film on the substrate surface, the difference in thermal expansion coefficient between the anodic oxide film and the substrate is minimized, enhancing the overall bonding strength of the film layer to the substrate, allowing for better coordination with the base coating layer, functional coating, and color coating, thereby improving the composite material's wear resistance.

[0031] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0033] FIG1 is a cross-sectional view of a partial structure of a composite material according to some embodiments of the present disclosure.

[0034] Reference numerals: 1. substrate; 2. anodized film layer; 3. basic coating layer; 4. functional coating layer; 41. first functional coating layer; 42. second functional coating layer; 5. color coating layer. DETAILED DESCRIPTION

[0035] The following describes the specific embodiments of the present disclosure in detail. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0036] Currently, substrates such as aluminum alloys are typically coated with three layers. Related art discloses a vacuum coating method for aluminum, in which the surface of the aluminum body is coated with three layers, sequentially from the inside out: the first layer is an aluminum oxide film, the second layer is a titanium-chromium film composed of metallic chromium and titanium, and the third layer is a titanium nitride film or a titanium carbide film. This coating method utilizes ultra-hard aluminum oxide as the base layer of the pure aluminum product, and then vacuum-coats the titanium-chromium film, titanium nitride film, or titanium carbide film, resulting in wear resistance, corrosion resistance, and a variety of decorative colors for the coated substrate. However, this film structure has the following drawbacks: First, due to the significant difference in the thermal expansion coefficients of the coating and the metal hardness, vacuum coating the aluminum oxide film on the metal surface results in poor adhesion. Second, the second coating layer is a single layer of chromium and titanium. Due to the simple structure of the coating, the corrosive solution may penetrate and corrode the substrate during corrosion testing. Furthermore, the low resistivity of the metal in the coating layer makes it easy for the aluminum substrate to communicate with the corrosive solution, causing galvanic corrosion, which in turn leads to poor overall corrosion resistance of the coated substrate.

[0037] A first aspect of an embodiment of the present disclosure provides a composite material, comprising a substrate and an anodized film layer, a base coating, a functional coating and a color coating arranged on a surface of the substrate in sequence from the inside to the outside; the metal elements in the first functional coating are different from the metal elements in the second functional coating, and the first functional coating contains metal elements while the second functional coating does not contain metal elements; the metal elements are selected from one or more of Group IVB metals, Group VB metals, Group VIB metals and Group IVA metals.

[0038] In some embodiments of the present disclosure, by alternating the first and second functional coatings, the longitudinal resistance of the functional coating is increased, reducing galvanic corrosion during corrosion testing without affecting the original performance of the film. The alternating first and second functional coatings improve the density of the functional coating, reduce film defects, and enhance the corrosion resistance of the composite material. Furthermore, by first applying a self-grown anodic oxide film on the substrate surface, the difference in thermal expansion coefficient between the anodic oxide film and the substrate is minimized, enhancing the overall bonding strength of the film to the substrate. This allows for better coordination with the base coating, functional coating, and color coating, improving the composite material's wear resistance.

[0039] Refer to Figure 1, which is a cross-sectional view of the local structure of a composite material of some embodiments of the present disclosure. The composite material includes a substrate 1 and an anodized film layer 2 formed on the surface of the substrate. The surface of the anodized film layer 2 is sequentially formed with a basic coating 3, a functional coating 4 and a color coating 5 by magnetron sputtering. The functional coating 4 includes 2-10 layers of a first functional coating 41 and a second functional coating 42 arranged alternately.

[0040] In some embodiments of the present disclosure, the number of layers of the plurality of first functional coating layers and the number of layers of the plurality of second functional coating layers are independently 2-10 layers. In some embodiments of the present disclosure, "alternating arrangement" can be understood as the first functional coating layer 41 and the second functional coating layer 42 being stacked in sequence. For example, the first functional coating layer 41 is stacked on the base coating layer 3, and the second functional coating layer 42 is stacked on the first functional coating layer 41. In this way, the number of layers of the first functional coating layer 41 and the second functional coating layer 42 are each 1 layer. On the basis of the above, a first functional coating layer 41 is stacked on the second functional coating layer 42, and a second functional coating layer 42 is stacked on the first functional coating layer 41. In this way, the number of layers of the first functional coating layer 41 and the second functional coating layer 42 are each 2 layers. Similarly, 2-10 layers of the first functional coating layer 41 and the second functional coating layer 42 can be set according to the desired effect.

[0041] In some embodiments, the number of layers of the first functional coating layer and the second functional coating layer can be 2 layers, 3 layers, 4 layers, 5 layers, 6 layers, 7 layers, 8 layers, 9 layers or 10 layers. In this way, the structure of the functional coating layer can be simplified. By alternately stacking the first functional coating layer and the second functional coating layer with the above number of layers, the density of the functional coating layer is improved, the defects of the film layer are reduced, and the corrosion resistance of the film layer is improved. In some embodiments, the number of layers of the first functional coating layer and the second functional coating layer is independently 3-8 layers. By alternately stacking the first functional coating layer and the second functional coating layer 3-8 times, the longitudinal resistance value of the film layer itself can be increased, the corrosion resistance of the composite material can be improved, and the overall thickness of the composite material can be effectively reduced.

[0042] In some embodiments of the present disclosure, the substrate 1 may be an aluminum alloy, and accordingly, the anodized film layer 2 is an aluminum oxide film layer grown on the surface of the aluminum alloy by an anodizing method.

[0043] In some embodiments of the present disclosure, the anodic oxide film layer 2 has a porous structure. For example, the porosity of the anodic oxide film layer can be 10%-20%, the pore diameter of the anodic oxide film layer can be 15-35 nm, and the thickness of the anodic oxide film layer can be 5-15 μm. The anodic oxide film layer having the above structure has a good bonding effect with the substrate and the base coating, has excellent wear resistance, and does not affect the appearance and metallic texture of the composite material.

[0044] In some embodiments of the present disclosure, the element of the base coating 3 is selected from at least one of Cr, Ti, Zr, W, Nb, Mo, Ta, or Ge. For example, the base coating is selected from at least one of Cr, Ti, W, or Nb. For example, the base coating 3 can be a Cr layer, a Ti layer, a W layer, a Nb layer, or a CrTi layer. The base coating 3 is placed between the anodized film layer 2 and the functional coating 4 to increase the adhesion between the functional coating 4 and the anodized film layer 2. The base coating 3 made of these materials can effectively prevent the film layer of the composite material from falling off from the surface of the substrate, thereby improving the wear resistance of the composite material.

[0045] In some embodiments of the present disclosure, the thickness of the basic coating layer 3 is 100-300 nm. For example, the thickness of the basic coating layer can be 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 240 nm, 260 nm, 280 nm, 300 nm, or any value within the aforementioned range. The moderate thickness of the basic coating layer 3 is not only conducive to enhancing the adhesion between the functional coating layer 4 and the anodized film layer 2, but also conducive to reducing the overall thickness of the composite material.

[0046] In some embodiments of the present disclosure, the first functional coating 41 includes a first element and a second element, wherein the first element is selected from at least one of Cr, Ti, Zr, W, Nb, Mo, Ta or Ge, and the second element is selected from at least one of C or N. The first element is selected from at least one of Cr, Ti, Zr, W, Nb, Mo, Ta or Ge, which can improve the wear resistance and corrosion resistance of the film layer. For example, the first element is selected from at least one of Cr, Ti, W or Nb. For example, the first functional coating 41 can be a CrC layer, a CrN layer, a TiC layer, a TiN layer, a CrTiWC layer or a CrTiWN layer. The first functional coating has good adhesion to the base coating and can transition to the color coating, so that the surface of the composite material presents a uniform color.

[0047] In some embodiments of the present disclosure, the thickness of the first functional coating 41 is 100-300 nm. For example, the thickness of the first functional coating 41 can be 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 240 nm, 260 nm, 280 nm, 300 nm, or any value within the aforementioned range. In this way, while achieving the corrosion resistance and wear resistance of the composite material, the first functional coating not only has good adhesion to the base coating, but also combines with the color coating to produce a good visual effect, and is also conducive to controlling the overall thickness of the composite material.

[0048] In the present disclosure, the first element and the second element of each first functional coating layer 41 that is alternately stacked may be the same or different. For example, to reduce process difficulty, the first element and the second element of each first functional coating layer 41 may be the same.

[0049] In some embodiments, the first element is the same as the element in the base plating layer to save costs and reduce process difficulty. For example, the first element in the first functional plating layer 41 is partially or completely the same as the element in the base plating layer 3. That is, the metal element in the first functional plating layer is partially or completely the same as the element in the base plating layer, thereby increasing the bonding strength between the first functional plating layer and the base plating layer.

[0050] In some embodiments of the present disclosure, the first functional coating further contains the element O. Nitrogen oxides have a higher electrical resistance and better bonding with metals or metal compounds, further enhancing the corrosion resistance of the film while maintaining bonding strength. By alternating the layers of nitrogen oxides and the first functional coating, the corrosion resistance of the composite material is further enhanced while maintaining bonding strength.

[0051] In some embodiments of the present disclosure, the second functional coating 42 is selected from one or more of an aluminum oxide layer, a silicon oxide layer, and a silicon nitride layer. These materials can meet the hardness requirements of the functional coating, and the precursors of these materials are easy to obtain. The aluminum oxide layer has the properties of high Vickers hardness and high resistance. By using aluminum oxide layers and silicon oxide layers and silicon nitride layers with similar properties to alternately stack the first functional coating layer, the longitudinal resistance value of the composite film layer is further increased. The elements of each second functional coating layer that is alternately stacked in a cyclic manner can be the same or different. For example, in order to reduce the difficulty of the process, the elements of each second functional coating layer are the same.

[0052] In some embodiments of the present disclosure, the second functional coating 42 has a thickness of 50-150 nm. For example, the thickness of the second functional coating 42 can be 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, or any value within the aforementioned range. The second functional coating 42 has a high Vickers hardness. These second functional coatings have high electrical resistance, which helps reduce the overall thickness of the composite material while improving the corrosion resistance and wear resistance of the composite material.

[0053] In some embodiments of the present disclosure, the color coating 5 includes a third element and a selective fourth element, the third element is selected from at least one of Cr, Ti, W or Si, and the fourth element includes at least one of C or N. The third element in the color coating is also beneficial to enhancing the adhesion between film layers, and the combination of the third element and the fourth element is beneficial to making the composite material present a uniform color. For example, the color coating 5 can be a Cr layer, a Ti layer, a W layer, a Si layer, a CrTi layer, a TiN layer, a TiCN layer, a CrCN layer or a CrSiCN layer. The color coating is used to adjust the color of the composite material. According to the required color effect, by adjusting the process of physical vapor deposition or the thickness of the color coating, the color of the color coating can be made richer, and the color coating and the aforementioned basic coating and functional coating can be combined to make the composite material present a more uniform color.

[0054] In some embodiments of the present disclosure, the color coating has a thickness of 300-800 nm. For example, the thickness of the color coating can be 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, or any value within the aforementioned range. This ensures that the composite material exhibits a uniform metallic luster while ensuring wear resistance, corrosion resistance, and scratch resistance, and can also reduce the material cost of the color coating.

[0055] In some embodiments, the basic coating layer, the functional coating layer, and the color coating layer work together to not only make the surface of the substrate present a uniform color, but also have good wear resistance and corrosion resistance.

[0056] In some embodiments of the present disclosure, the wear resistance of the composite material meets at least one of the following requirements: in a vibration wear test, the maximum vibration wear time when the wear test result is below level 1 is more than 4 hours; or the corrosion resistance of the composite material meets at least one of the following sub-requirements: in a water boiling test, the maximum water boiling treatment time when the cross-cut test result is below level 1 is more than 1.5 hours; in a neutral salt spray test, the maximum neutral salt spray treatment time when the cross-cut test result is below level 1 is more than 48 hours; or in an artificial sweat test, the maximum artificial sweat treatment time when the cross-cut test result is below level 1 is more than 96 hours.

[0057] The operation of vibration wear is as follows: put the sample into the Rosler vibration wear tester, in which abrasive, water and detergent are also placed; the abrasive includes 3 parts of RKF 10K (yellow cone) and 1 part of RKK 15P (green pyramid), a total of about 15L, the amount of water is 1L, and the amount of detergent is 200mL; add 0.5L of pure water every half an hour during the operation; take photos and observe every half an hour. The grade of the wear test results is determined according to the following standards: Grade 0: There is no obvious wear and bruises on the large surface, corners and edges of the sample, and the color is as clear as before; Grade 1: There is no wear on the large surface of the sample, only slight bruises and wear can be seen on the composite film layer at the corners and ridges, but the wear does not expose the substrate, and the area of ​​a single bruise is less than 1mm. 2 Level 2: A small amount of point wear appears on the large surface of the specimen, and the largest single wear area is less than 1mm 2 , or the edges and corners are worn through (leaking out the base material), and the maximum wear line width is less than 1mm.

[0058] Boiling treatment refers to placing the sample in pure water at 100°C and heating it in water; neutral salt spray treatment refers to spraying salt spray (NaCl solution concentration of 5wt%, pH value of 6.8) for 24 hours under the conditions of 35±2°C and humidity>85%; artificial sweat treatment refers to coating the material containing artificial sweat for 48 hours under the conditions of 45°C and relative humidity of 95%. The artificial sweat includes: 1000 parts by weight of water, 19.5 parts by weight of 85% lactic acid, 5±0.01 parts by weight of urea, 20±0.01 parts by weight of sodium chloride, 17.50±0.01 parts by weight of NH4Cl (ammonium chloride), 2.62 parts by weight of anhydrous acetic acid and an appropriate amount of sodium hydroxide powder. The pH value of artificial sweat is 4.7.

[0059] The cross-cut test is conducted in accordance with GB / T 9286-2021. For example, a grid is drawn on the composite material sample at 1mm intervals, forming 10×10 continuous 1mm×1mm squares. Each scribe line extends to the substrate, and the cross-cut area is clean. A piece of tape approximately 75mm long is applied to the cross-cut area (pressure-sensitive adhesive tape), with the tape extending at least 20mm beyond the grid line to ensure effective contact between the tape and the sample coating. After 3 minutes, the tape is held at the free end, held at a 60° angle to the sample as much as possible, and removed smoothly within 1.0s. The film is inspected for any peeling and the results are evaluated. The results are graded as follows: Grade 0: Completely smooth cut edges, with no peeling at the cut edges; Grade 1: Minor peeling at the cut intersections, with the actual damage area within the cross-cut area not exceeding 5%; Grade 2: Peeling at the cut edges and intersections, with the actual damage area within the cross-cut area ranging from 5% to 15%.

[0060] A second aspect of the present disclosure provides a method for preparing a composite material, the method comprising: performing anodizing on a substrate to obtain a substrate with an anodized film layer attached thereto; performing physical vapor deposition on the substrate with the anodized film layer attached thereto; the physical vapor deposition comprising the following steps: performing a first magnetron sputtering on the substrate with the anodized film layer attached thereto to deposit a basic coating layer on the surface of the anodized film layer; performing a second magnetron sputtering and a third magnetron sputtering alternately on the basic coating layer multiple times to deposit a functional coating layer on the surface of the basic coating layer; the functional coating layer comprises a plurality of first functional coating layers and a plurality of second functional coating layers arranged alternately; performing a fourth magnetron sputtering on the surface of the functional coating layer to deposit a color coating layer on the surface of the functional coating layer; a first functional coating layer among the plurality of first functional coating layers and a second functional coating layer among the plurality of second functional coating layers satisfy one of the following conditions: the metal element in the first functional coating layer is different from the metal element in the second functional coating layer, or the first functional coating layer contains a metal element while the second functional coating layer does not contain a metal element; the metal element is selected from one or more of Group IVB metals, Group VB metals, Group VIB metals, and Group IVA metals.

[0061] In order to improve the corrosion resistance of the composite material and based on cost savings, some embodiments of the present disclosure use magnetron sputtering technology to sequentially form a basic coating, a functional coating, and a color coating on the surface of the oxide film layer. The deposition rate and processing cost of magnetron sputtering technology are low, and the formed PVD film layer is well combined with the anodized film layer. In some embodiments of the present disclosure, by alternating the second magnetron sputtering and the third magnetron sputtering multiple times, an alternating first functional coating layer and a second functional coating layer can be formed on the basic coating formed by the first magnetron sputtering, so as to increase the longitudinal resistance value of the film layer itself, reduce film defects, and improve the corrosion resistance of the composite material.

[0062] In some embodiments of the present disclosure, the anodizing comprises the following steps: performing an anodizing treatment in a sulfuric acid solution using graphite as a cathode and the substrate as an anode to obtain a substrate with the first anodized film layer attached thereto.

[0063] In some embodiments of the present disclosure, the anodizing treatment time is 30-60 min; the voltage is 8-15 V; and the sulfuric acid concentration is 100-200 g / L.

[0064] The anodizing further comprises: placing the substrate with the first anodized film layer attached thereto in a phosphoric acid solution for pore expansion treatment to obtain a substrate with a second anodized film layer formed thereon.

[0065] In some embodiments of the present disclosure, the concentration of the phosphoric acid solution is 3-10 wt%, and the pore expansion treatment lasts for 2-10 minutes. By performing the aforementioned anodizing treatment on the substrate surface, an anodic oxide film having a thermal expansion coefficient that is slightly different from that of the substrate is formed on the substrate surface. This can enhance the overall bonding strength between the substrate and the composite film layer thereon, improving the wear resistance of the composite material.

[0066] In some embodiments of the present disclosure, the number of the multiple second magnetron sputterings and the number of the multiple third magnetron sputterings are each independently 2 to 10 times. In some embodiments of the present disclosure, the number of the multiple second magnetron sputterings and the number of the multiple third magnetron sputterings are each independently 3 to 8 times.

[0067] In some embodiments of the present disclosure, the conditions for the first magnetron sputtering include: the target material is at least one of Cr, Ti, Zr, W, Nb, Mo, Ta, or Ge. Forming the base coating layer on the anodized film by magnetron sputtering increases the bonding strength between the base coating layer and the anodized film, further strengthening the bonding strength between the substrate and the PVD film layer.

[0068] In some embodiments of the present disclosure, the conditions for the second magnetron sputtering include: the target material is at least one of Cr, Ti, Zr, W, Nb, Mo, Ta or Ge, and the reaction gas is nitrogen or acetylene.

[0069] In some embodiments of the present disclosure, the metal elements of the first functional coating layer are partially identical or completely identical to the metal elements of the basic coating layer, so that the bonding strength between the first functional coating layer and the basic coating layer is increased.

[0070] In some embodiments of the present disclosure, the conditions for the third magnetron sputtering process include: a target material of Al or Si, and a reactive gas of oxygen or nitrogen. Magnetron sputtering is used to form alternating first and second functional coating layers, resulting in dense and uniform films that further enhance the corrosion and wear resistance of the functional coating layers.

[0071] In some embodiments of the present disclosure, the fourth magnetron sputtering process is performed under the following conditions: the target material is at least one of Cr, Ti, W, or Si; and the reactive gas is at least one of nitrogen or acetylene. During the fourth magnetron sputtering process, if the color coating does not contain at least one of C or N, the reactive gas is not introduced. The color coating formed on the functional coating using the PVD process exhibits high hardness and excellent wear, corrosion, and scratch resistance.

[0072] In some embodiments of the present disclosure, the method for preparing the composite material comprises the following steps:

[0073] (1) placing an aluminum alloy substrate in 100-200 g / L sulfuric acid and oxidizing it at 8-15 V for 30-60 min, washing it with water, and then placing it in a 3-10 wt% phosphoric acid solution for pore expansion treatment for 2-10 min. The expanded aluminum alloy substrate is then baked at 80-120° C. for 30-40 min. For example, the aluminum oxide film layer has a thickness of 5-15 μm, a micropore diameter of 15-35 nm, and a porosity of 10%-20%.

[0074] (2) placing the oxidized substrate in a vacuum furnace and evacuating the vacuum, heating it to 80-180° C., filling the machine with argon gas, turning on the ion source, and performing ion cleaning on the surface of the aluminum alloy substrate and the target;

[0075] (3) placing the ion-cleaned substrate in a vacuum furnace and evacuating the vacuum, heating it to 60-90° C., filling the furnace with argon gas, and simultaneously turning on a medium-frequency sputtering power source for at least one target material selected from Cr, Ti, Zr, W, Nb, Mo, Ta, or Ge; depositing a base coating on the surface of the aluminum oxide film layer of the aluminum alloy substrate, for example, the base coating having a thickness of 100-300 nm;

[0076] (4) introducing argon gas into the vacuum furnace, turning on the medium frequency sputtering power supply of at least one target material selected from Cr, Ti, Zr, W, Nb, Mo, Ta, or Ge, introducing nitrogen or acetylene as a reaction gas, and depositing a first functional coating on the surface of the base coating. For example, the thickness of the first functional coating is 100-300 nm.

[0077] (5) introducing argon gas into the vacuum furnace, turning on the sputtering power supply of one of the Al and Si targets, introducing oxygen or nitrogen gas, and depositing a second functional coating layer on the surface of the first functional coating layer, for example, the thickness of the second functional coating layer is 50-150 nm;

[0078] (6) Repeat steps (4) and (5) 2-10 times in sequence to alternately stack the first functional coating layer and the second functional coating layer, then introduce argon gas into the vacuum furnace, turn on the sputtering power supply of at least one target material of Cr, Ti, W or Si, and selectively introduce at least one of the reaction gases nitrogen or acetylene to deposit a color coating on the surface of the second functional coating layer, for example, the thickness of the color coating is 300-800 nm.

[0079] In some embodiments of the present disclosure, the substrate may be pretreated before anodizing to remove oil stains on the surface of the substrate, such as by sequentially performing water washing, degreasing, and neutralization treatments.

[0080] The composite material disclosed herein has a simple preparation process and high repeatability, and the formed composite film layer has good stability, and can be widely used in modern intelligent terminal shell structure products.

[0081] The third aspect of the present disclosure provides a housing, which comprises the composite material provided in the first aspect of the present disclosure. For example, part or all of the housing may be composed of the aforementioned composite material.

[0082] The present disclosure also provides an electronic device, comprising the housing provided in the third aspect of the present disclosure. The housing of the present disclosure can be applied to electronic devices. For example, in some embodiments of the present disclosure, the electronic device can be a mobile phone, a laptop computer, a tablet computer, a watch, a camera, a monitoring device, an AR device, or a VR device. The housing can be a back cover, a middle frame, or other decorative structure of the electronic device.

[0083] The present disclosure is further described in detail below through examples, but the present disclosure is not limited to the following examples.

[0084] Example 1

[0085] The composite material of this embodiment includes an aluminum alloy substrate and an anodized film layer, a basic coating layer, a functional coating layer and a color coating layer arranged on one surface of the substrate from the inside to the outside; the functional coating layer includes 5 layers of first functional coating layers (TiN layers) and 5 layers of second functional coating layers (Al2O3 layers) arranged alternately.

[0086] The method for preparing the composite material in this embodiment includes the following steps:

[0087] (1) The aluminum alloy substrate was washed, degreased, and neutralized in sequence, and then the cleaned aluminum alloy substrate was placed in 125g / L sulfuric acid and oxidized at 8V for 45 minutes, washed with water for 180 seconds, and then placed in a 6wt% phosphoric acid solution for pore expansion for 5 minutes. The expanded aluminum alloy substrate was baked at 80°C for 30 minutes; the aluminum oxide film obtained by anodization had a thickness of 10μm, a micropore diameter of 25nm, and a porosity of 10%;

[0088] (2) placing the oxidized substrate in a vacuum coating machine and performing ion cleaning on the substrate and target surfaces;

[0089] (3) introducing argon gas into the vacuum furnace, turning on the medium-frequency sputtering power supply of the Ti target, and depositing a base coating (Ti layer) on the surface of the aluminum oxide film layer of the aluminum alloy substrate. The thickness of the Ti layer is 150 nm;

[0090] (4) Argon gas was introduced into the vacuum furnace, the Ti target sputtering power supply was turned on, and then nitrogen gas was introduced as a reactive gas to deposit the first functional coating (TiN layer) on the surface of the base coating. The thickness of the TiN layer was 150 nm.

[0091] (5) introducing argon gas into the vacuum furnace, turning on the Al target sputtering power supply, and then introducing the reactive gas oxygen to deposit a second functional coating layer (Al2O3 layer) on the surface of the first functional coating layer. The thickness of the Al2O3 layer is 75 nm.

[0092] (6) Repeat steps (4) and (5) five times in sequence to alternately stack the first functional coating layer and the second functional coating layer; then, introduce argon gas into the vacuum furnace, turn on the sputtering power supply of the Cr target and the Ti target, and deposit a color coating layer (CrTi layer) on the surface of the second functional coating layer. The thickness of the CrTi layer is 550 nm.

[0093] Example 2

[0094] The method for preparing the composite material in this embodiment is the same as that in embodiment 1, except that: the basic coating layer is a Cr layer; the first functional coating layer is a CrN layer, and the thickness of the CrN layer is 120 nm.

[0095] Example 3

[0096] The method for preparing the composite material in this embodiment is the same as that in Example 1, except that the thickness of the anodic oxide film layer is 15 μm.

[0097] Example 4

[0098] The method for preparing the composite material in this embodiment is the same as that in Example 1, except that the functional coating includes two first functional coating layers of TiN and two second functional coating layers of Al2O3, which are alternately arranged, and the thickness of the first functional coating layer of TiN is 400 nm, and the thickness of the second functional coating layer of Al2O3 is 100 nm.

[0099] Example 5

[0100] The method for preparing the composite material in this embodiment is the same as that in Example 1, except that the functional coating includes three first functional coating layers of TiN and three second functional coating layers of Al2O3, which are alternately arranged; and the thickness of the first functional coating layer of TiN is 300 nm, and the thickness of the second functional coating layer of Al2O3 is 150 nm.

[0101] Example 6

[0102] The method for preparing the composite material in this embodiment is the same as that in Example 1, except that the functional coating includes 8 layers of first functional coating TiN layers and 8 layers of second functional coating Al2O3 layers arranged alternately, and the thickness of the first functional coating CrN layer is 150nm, and the thickness of the second functional coating Al2O3 layer is 75nm.

[0103] Example 7

[0104] The method for preparing the composite material in this embodiment is the same as that in Example 1, except that the functional coating includes 10 layers of the first functional coating TiN layer and 10 layers of the second functional coating Al2O3 layer arranged alternately, and the thickness of the first functional coating TiN layer is 100 nm, and the thickness of the second functional coating Al2O3 layer is 50 nm.

[0105] Example 8

[0106] The method for preparing the composite material in this embodiment is the same as that in Example 1, except that the functional coating includes four first functional coating layers of TiN and four second functional coating layers of Al2O3, which are alternately arranged, and the thickness of the first functional coating layer of TiN is 100 nm, and the thickness of the second functional coating layer of Al2O3 is 175 nm.

[0107] Example 9

[0108] The method for preparing the composite material in this embodiment is the same as that in embodiment 1, except that the second functional coating is a SiO2 layer; the color coating is a CrCN layer; the thickness of the second functional coating is 75 nm, and the thickness of the color coating is 550 nm.

[0109] Comparative Example 1

[0110] The method for preparing the composite material in this comparative example is the same as that in Example 1, except that the functional coating layer of the composite material is a TiN layer, and the thickness of the TiN layer is 1125 nm.

[0111] Comparative Example 2

[0112] The method for preparing the composite material in this comparative example is the same as that in Example 1, except that the functional coating layer of the composite material is a CrN layer, and the thickness of the CrN layer is 1200 nm.

[0113] Test Examples

[0114] The composite material samples prepared in Examples 1-9 and Comparative Examples 1-2 were subjected to performance tests, including a water boiling test, an artificial sweat test, a salt spray test, and a vibration wear test.

[0115] (1) Hundred-grid test

[0116] The 100-grid test of composite materials is carried out with reference to GB / T 9286-2021. The 100-grid test is carried out at a temperature of 23±2°C and a relative humidity of 50±5%.

[0117] Test conditions: A grid of 10 x 10 continuous 1mm x 1mm squares is drawn on the composite material sample at 1mm intervals. Each grid line extends to the substrate, and the gridded area is clean. A section of tape approximately 75mm long is applied to the gridded area (pressure-sensitive adhesive tape), with the tape extending at least 20mm beyond the grid line to ensure effective contact between the tape and the sample coating. Allow the tape to stand for 3 minutes. Holding the dangling end of the tape, hold it at a 60° angle to the sample as much as possible and gently peel it off within 0.5-1.0 seconds. The film shedding condition is then inspected and the result is assessed on a scale of 0 to 5.

[0118] in:

[0119] Level 0: The cut edge is completely smooth and there is no peeling on the lattice edge.

[0120] Level 1: Small pieces peel off at the intersection of the cuts, and the actual damage in the grid area does not exceed 5%.

[0121] Level 2: There is peeling at the edges and intersections of the incision, covering an area of ​​5%-15%.

[0122] Level 3: The edges of the cuts are peeling off, large pieces are peeling off, and even some grids are peeling off. The peeling area is 15%-35%.

[0123] Level 4: Large pieces of the cut edge peel off, some grids peel off completely, and the peeled area is 35%-65%.

[0124] Level 5: Exceeds the previous level.

[0125] (2) Artificial sweat test

[0126] Test conditions: Before the test, check that the sample has no abnormal appearance and wipe the sample surface clean. Then, use a dust-free cloth soaked in artificial sweat to wipe the sample surface back and forth (wiping force is about 3-6N) for 2 minutes. After that, use a dust-free cloth to completely soak the sweat, half-wrap the sample (small parts are completely wrapped), and place it in a 45°C, 95% relative humidity incubator for 48 hours (single test cycle duration); after the test, take out the sample, wash it with water, and restore it to room temperature for 2 hours. Then check the appearance of the sample and perform the adhesion test in accordance with the above item (1). Record the maximum time for the salt spray test when the sample film layer has no abnormality and there is no obvious change in appearance (discoloration, rust, shedding, blistering, cracking, etc.), as well as the maximum artificial sweat treatment time when the 100-grid test reaches level 1 or below.

[0127] Preparation method of artificial sweat: 1L of water, 19.5g of 85% lactic acid, 5±0.01g of urea, 20±0.01g of sodium chloride, 17.50±0.01g of NH4Cl and 2.62g of anhydrous acetic acid, stir well, and add sodium hydroxide powder to make the solution pH reach 4.7.

[0128] (3) Neutral salt spray test

[0129] Test conditions: Before the test, check the appearance of the sample and wipe the surface of the sample clean. Then, place the composite material sample in the test machine at a 45-degree angle to the horizontal plane, with half of the sample facing up and half facing up. The conditions of a single test cycle include: temperature of 35±2℃, humidity of more than 85%, and continuous salt spraying of the composite material with a NaCl solution with a pH value of 6.8 and a concentration of 5wt% for 24 hours. Take a portion of the sample facing up and the sample facing up at room temperature for 2 hours, then check the appearance of the sample. The remaining samples are placed at 40℃ and 95% humidity for 168 hours, then restored to room temperature for 2 hours, and the test surface is checked. Record the maximum time for the salt spray test when the sample film layer has no abnormal appearance and no obvious changes in appearance (discoloration, rust, shedding, blistering, cracking, etc.). Refer to the above item (1) for the adhesion test. Record the maximum neutral salt spray treatment time for the sample to reach level 1 or below in the 100-grid test.

[0130] (4) Boiling test

[0131] Test conditions: Before testing, check the appearance of the sample and wipe the surface clean; heat pure water to 100°C and place the sample in a water bath, ensuring that the sample does not overlap, collide, or directly contact the heating rod; the water bath time is 180 minutes. After the test is completed, cool naturally to room temperature; inspect the appearance of the sample, and then perform the adhesion test in accordance with the above-mentioned item (1). Record the maximum time that the sample's appearance has no obvious corrosion, blistering, pitting, cracking, deformation, or other adverse changes, as well as the maximum water boiling (100°C) treatment time that the sample reaches level 1 or below in the 100-grid test.

[0132] (5) Vibration wear test

[0133] Test conditions:

[0134] a. Vibration wear tester: R180 / 530TE30 (equipment frequency: 50±0.5HZ, amplitude 1.65±0.1mm).

[0135] The volume ratio of mixed abrasive 15L: RKF10K (yellow cylinder) and RKK15P (green cone) is 3:1.

[0136] Detergent: Rosler FC120. The detergent (FC120) used in the test was diluted with water at a dilution ratio of 1:50 (volume ratio).

[0137] b. Test method

[0138] Pour 1L of water and 200mL of diluted detergent into the Rosler vibratory abrader containing the abrasive. Place the specimen into the abrasive with the head facing upward. Turn on the abrader. Add 0.5L of purified water every half hour while adjusting the orientation of the composite material as it is inserted into the abrasive. Take photos every half hour. Record the maximum vibration wear treatment time until the specimen's wear level reaches or falls below level 1.

[0139] The standards for wear levels 0-2 are:

[0140] Level 0: There is no obvious wear and damage on the large surface, corners and edges of the sample, and the color is as clear as before.

[0141] Level 1: The specimen has no wear on the large surface, and only the composite film layer at the corners and ridges has slight scratches and wear, but the wear does not expose the base material, and the area of ​​a single scratch is less than 1mm 2 .

[0142] Level 2: A small amount of point wear occurs on the large surface of the specimen, and the largest single wear area is less than 1mm 2 , or the edges and corners are worn through (leaking out the base material), and the maximum wear line width is less than 1mm.

[0143] The test results are shown in Table 1.

[0144] Table 1

[0145] It can be seen from the examples and comparative examples that the composite materials provided in some embodiments of the present disclosure have good bonding strength between the film layer and the substrate, and have excellent wear resistance and corrosion resistance.

[0146] It can be seen from Comparative Examples 1-2 and the embodiments that when only one functional coating layer is provided, the wear resistance and corrosion resistance of the composite material are both reduced. After adding the second functional coating layer, the Al2O3 coating layer, the corrosion resistance of the composite film layer is enhanced by utilizing the high Vickers hardness and high resistance of the Al2O3 coating layer.

[0147] It can be seen from Examples 4 and 8 that the overall performance of the film layer is related to the thickness of the first functional coating layer and the second functional coating layer. The first functional coating layer has a suitable thickness, which is beneficial to improving its bonding strength with the base coating layer; the second functional coating layer with a suitable thickness can increase the overall resistance and hardness of the film layer and improve the wear resistance of the film layer.

[0148] Some embodiments of the present disclosure are described in detail above. However, the present disclosure is not limited to the details in the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0149] It should also be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0150] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A composite material comprising: A substrate, and an anodic oxide film layer, a base coating layer, a functional coating layer, and a color coating layer sequentially arranged on one surface of the substrate from the inside to the outside, wherein the functional coating layer includes a plurality of first functional coating layers and a plurality of second functional coating layers arranged alternately; Wherein, one of the plurality of first functional coating layers and one of the plurality of second functional coating layers satisfy one of the following conditions: The metal element in the first functional coating layer is different from the metal element in the second functional coating layer; or The first functional coating layer contains metal elements and the second functional coating layer does not contain metal elements; The metal element is selected from one or more of Group IVB metals, Group VB metals, Group VIB metals, and Group IVA metals.

2. The composite material according to claim 1, wherein The number of layers of the plurality of first functional coating layers and the number of layers of the plurality of second functional coating layers are each independently 2-10 layers.

3. The composite material according to claim 2, wherein The number of layers of the plurality of first functional coating layers and the number of layers of the plurality of second functional coating layers are each independently 3-8 layers.

4. The composite material according to claim 1, wherein The first functional coating and the second functional coating satisfy at least one of the following conditions: The thickness of the first functional coating is 100-300 nm; or The thickness of the second functional coating is 50-150 nm.

5. The composite material according to any one of claims 1 to 4, wherein The first functional coating layer includes a first element and a second element, the first element is selected from at least one of Cr, Ti, Zr, W, Nb, Mo, Ta or Ge, and the second element is selected from at least one of C or N.

6. The composite material according to claim 5, wherein The first element in the first functional coating layer is partially or entirely the same as an element in the basic coating layer.

7. The composite material according to claim 5, wherein The first functional coating also contains O element.

8. The composite material according to any one of claims 1 to 4, 6 and 7, wherein: The second functional coating layer is selected from one or more of an aluminum oxide layer, a silicon oxide layer and a silicon nitride layer.

9. The composite material according to any one of claims 1 to 4, 6 and 7, wherein: The anodized film layer satisfies at least one of the following: The anodized film layer has a porous structure; The pore diameter of the anodic oxide film layer is 15-35 nm; The porosity of the anodized film layer is 10%-20%; or The thickness of the anodic oxide film layer is 5-15 μm.

10. The composite material according to any one of claims 1 to 4, 6 and 7, wherein: The substrate is an aluminum alloy; the element of the basic coating is selected from at least one of Cr, Ti, Zr, W, Nb, Mo, Ta or Ge.

11. The composite material according to any one of claims 1 to 4, 6 and 7, wherein: The color coating layer includes a third element and an optional fourth element, wherein the third element is selected from at least one of Cr, Ti, W or Si, and the fourth element includes at least one of C or N.

12. The composite material according to any one of claims 1 to 4, 6 and 7, wherein: The basic coating satisfies at least one of the following: The thickness of the basic coating is 100-300 nm; or The thickness of the color coating is 300-800 nm.

13. The composite material according to any one of claims 1 to 4, 6 and 7, wherein: The wear resistance of the composite material meets at least one of the following requirements: In the vibration wear test, the maximum vibration wear time for wear test results below level 1 is more than 4 hours; or The corrosion resistance of the composite material meets at least one of the following sub-requirements: In the boiling test, the maximum boiling time for the cross-cut test result below level 1 is more than 1.5 hours; In the neutral salt spray test, if the cross-cut test result is below level 1, the maximum neutral salt spray treatment time is more than 48 hours; or In the artificial sweat test, the maximum artificial sweat treatment time for a cross-cut test result below level 1 is more than 96 hours.

14. A method for preparing a composite material, comprising: Anodizing the substrate to obtain an anodic oxide film layer; Performing physical vapor deposition on the substrate with the anodic oxide film layer attached thereto; The physical vapor deposition comprises the following steps: Performing a first magnetron sputtering on the substrate with the anodic oxide film layer attached thereto to deposit a basic coating layer on the surface of the anodic oxide film layer; Alternatingly performing a second magnetron sputtering and a third magnetron sputtering on the basic coating layer multiple times to deposit a functional coating layer on the surface of the basic coating layer; the functional coating layer includes a plurality of first functional coating layers and a plurality of second functional coating layers that are alternately arranged; and performing a fourth magnetron sputtering on the surface of the functional coating layer to deposit a color coating layer on the surface of the functional coating layer; Wherein, a first functional coating layer among the plurality of first functional coating layers and a second functional coating layer among the plurality of second functional coating layers satisfy one of the following conditions: the metal element in the first functional coating layer is different from the metal element in the second functional coating layer, or the first functional coating layer contains a metal element while the second functional coating layer does not contain a metal element; The metal element is selected from one or more of Group IVB metals, Group VB metals, Group VIB metals, and Group IVA metals.

15. The method according to claim 14, wherein The anodizing step comprises the following steps: In a sulfuric acid solution, an anodic oxidation treatment is performed using graphite as a cathode and the substrate as an anode to obtain a substrate with the first anodic oxide film layer attached thereto.

16. The method according to claim 15, wherein The anodizing treatment time is 30-60 minutes; the voltage is 8-15V; and the sulfuric acid concentration is 100-200g / L.

17. The method according to claim 15 or 16, wherein The anodizing further comprises: placing the substrate with the first anodized film layer attached thereto in a phosphoric acid solution for pore expansion treatment to obtain a substrate with a second anodized film layer formed thereon.

18. The method according to claim 17, wherein The concentration of the phosphoric acid solution is 3-10 wt %; and the time for the pore expansion treatment is 2-10 minutes.

19. The method according to claim 14, wherein The number of the multiple second magnetron sputterings and the number of the multiple third magnetron sputterings are each independently 2-10 times.

20. The method according to claim 19, wherein The number of the multiple second magnetron sputterings and the number of the multiple third magnetron sputterings are each independently 3-8 times.

21. The method according to claim 14, wherein The first magnetron sputtering, the second magnetron sputtering, the third magnetron sputtering, and the fourth magnetron sputtering satisfy at least one of the following conditions: The conditions for the first magnetron sputtering include: the target material is at least one of Cr, Ti, Zr, W, Nb, Mo, Ta or Ge; The conditions of the second magnetron sputtering include: the target material is at least one of Cr, Ti, Zr, W, Nb, Mo, Ta or Ge, and the reaction gas is one of nitrogen and acetylene; The conditions of the third magnetron sputtering include: the target material is one of Al and Si; the reaction gas is one of oxygen and nitrogen; or The conditions of the fourth magnetron sputtering include: the target material is at least one of Cr, Ti, W or Si; and the reaction gas is at least one of nitrogen or acetylene.

22. The method according to claim 14, wherein The metal elements of the first functional coating layer are partially the same as or completely the same as the metal elements of the basic coating layer.

23. A casing comprising the composite material according to any one of claims 1 to 13.

24. An electronic device comprising the housing according to claim 23.

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