Methods for selective porosity of composite substrates, metal articles, and metal composites

Abstract

The application discloses a method for selectively forming holes in a composite substrate, a metal product and a metal composite, and the method comprises the following steps: placing a composite substrate in an electrolyte, wherein the composite substrate comprises a stainless steel substrate layer and an aluminum alloy substrate layer; taking the composite substrate as an anode; and performing electrolysis to form holes on the surface of the aluminum alloy substrate layer of the composite substrate; the electrolyte used in the electrolysis comprises water, an acid, an alcohol and a chloride capable of dissociating chlorine ions in water; the acid provides an acid radical capable of forming an Al 3+ complexation occurs; the molar ratio of the acid and the chlorine ions dissociated from the chloride ranges from 1:1 to 10:1; and the mass concentration of the alcohol ranges from 1% to 10%. The application can form an independent hole structure capable of meeting the requirements of micron-level injection molding on the aluminum alloy part without damaging the stainless steel part.

Description

Technical Field

[0001] This application relates to the field of metal materials technology, and in particular to a method for selective pore forming of composite substrates, metal articles, and metal composites. Background Technology

[0002] Currently, the anodizing process mainly uses phosphoric acid as the primary electrolyte to form nanoscale porous structures on the surface of aluminum alloys. Due to the small size of these pores, only plastics with low molecular chain rigidity and good flowability, such as PBT (polybutylene terephthalate), can be injection molded within the pores. However, PBT plastic has low strength and cannot meet the requirements for product drop tests, necessitating the replacement with high-strength plastics such as Solvay AV651 (polyaryletherketone). However, these high-strength plastics, due to their high molecular chain rigidity and poor flowability, cannot be injected into the nanoscale pores formed by existing processes. Furthermore, to improve material strength, stainless steel and aluminum alloy are often die-cast into composite materials. These composite materials use stainless steel as the outer surface to ensure high strength, while aluminum alloy serves as the inner surface, reducing overall material weight and internal machining costs. However, forming porous structures on the surface of the composite material often damages the stainless steel. Therefore, there is an urgent need to develop a micropore fabrication process that can form porous structures on the surface of composite aluminum alloys without damaging the stainless steel, to meet the requirements of injection molding and product strength. Summary of the Invention

[0003] In view of this, it is necessary to provide a method for selective pore forming of composite substrates, metal articles, and metal composites that can solve the above-mentioned technical problems.

[0004] The first aspect of this application provides a method for selectively forming pores in a composite substrate, comprising the following steps:

[0005] A composite substrate, comprising a stainless steel substrate layer and an aluminum alloy substrate layer, is placed in an electrolyte. Electrolysis is performed using the composite substrate as the anode to form pores on the surface of the aluminum alloy substrate layer.

[0006] The electrolyte used in the electrolysis includes water, acid, alcohol, and chloride that can dissociate into chloride ions in water. The acid provides anions that can react with the Al generated during electrolysis in the aluminum alloy substrate layer. 3+ Complexation occurs; among them,

[0007] The molar ratio of the acid to the chloride ions dissociated from the chloride is in the range of 1:1 to 10:1, and the mass concentration of the alcohol is in the range of 1% to 10%.

[0008] The selective pore-forming method provided in this application utilizes a water-based-organic composite electrochemical corrosion mechanism. When the composite substrate is electrolyzed in an electrolyte containing alcohol, the materials of stainless steel and aluminum alloy differ, with aluminum alloy exhibiting superior conductivity compared to stainless steel. Consequently, current flows first through the aluminum alloy, rapidly forming a dense alumina passivation film that reduces conductivity, allowing current to flow through the stainless steel. After current passes through, stainless steel also forms a passivation film, primarily composed of chromium oxide and nickel oxide. Chloride ions dissociated from chloride in the electrolyte can act as etching ions under the guidance of an electric field to destroy the Al-O bonds in the alumina passivation film, thereby forming pitting corrosion on the aluminum alloy surface and thus creating pores. However, under electrolytic conditions, chloride ions are difficult to destroy the Cr-O and Ni-O bonds in the passivation film on stainless steel, making it difficult to etch pores on the stainless steel surface. In addition, the acid radicals provided by the acid in the electrolyte will complex with the aluminum ions dissolved in the aluminum alloy substrate layer during electrolysis. The resulting complexes will adhere to the aluminum alloy surface, preventing surface corrosion and facilitating pore formation. This application effectively avoids the problems of polishing and surface corrosion of aluminum alloys by controlling the molar ratio of acid and chloride ions in the electrolyte, which is beneficial for selective pore formation on the aluminum alloy substrate layer. Furthermore, when the alcohol content is too high, it will cause an increase in solution resistance and voltage, resulting in insufficient corrosion inhibition and making the aluminum alloy prone to over-corrosion. This application uses a low content of alcohol in the electrolyte, which can simultaneously play a protective role and prevent surface corrosion. This application uses an electrolyte containing chloride ions and low levels of alcohols to form independent pore structures in aluminum alloy parts that can meet micron-level injection molding requirements without damaging the stainless steel parts. The formed pores also have adhesive-pulling capabilities, which can improve the bonding force between the pores and the injection molding material.

[0009] According to some embodiments of this application, the electrolyte used contains more than 50% water by mass. The large amount of water in the electrolyte can increase the degree of dissociation of the electrolyte components, improve the electrolysis efficiency, and at the same time relatively reduce the formulation cost, thus having great application value.

[0010] According to some embodiments of this application, the acid is selected from at least one of phosphoric acid, oxalic acid, lactic acid, and tartaric acid. The acid anion provided can complex with dissolved aluminum ions; for example, phosphate ions can complex with aluminum ions to form aluminum phosphate, which adheres to the surface of the aluminum alloy and prevents surface corrosion.

[0011] According to some embodiments of this application, the mass concentration of the acid ranges from 2% to 8%.

[0012] According to some embodiments of this application, the alcohol is selected from at least one of propylene glycol, ethylene glycol, glycerol, and diethylene glycol. Alcohols can provide high internal resistance, preventing excessive current during electrolysis and thus providing a protective function.

[0013] According to some embodiments of this application, the chloride is a soluble chloride salt, and the chloride is selected from at least one of NaCl, KCl, CuCl2, and FeCl2.

[0014] According to some embodiments of this application, the mass concentration of the chloride ranges from 0.5% to 5%.

[0015] According to some embodiments of this application, in the electrolysis step, the applied current density ranges from 1 A / dm³. 2 ~5A / dm 2 Using the electrolyte provided in this application, selective pore formation can be performed on aluminum alloys under low current conditions.

[0016] According to some embodiments of this application, the electrolysis time is 10 min to 30 min. The depth of the formed pores can be controlled by controlling the electrolysis time.

[0017] According to some embodiments of this application, the temperature of the electrolyte is 20°C to 65°C.

[0018] According to some embodiments of this application, the method also includes the steps of peeling off the black film, cleaning, and drying the electrolyzed composite substrate.

[0019] According to some embodiments of this application, the composite substrate is further further subjected to a surface treatment step before being placed in the electrolyte. In some embodiments, the surface treatment includes degreasing and peeling off the black film. By performing the surface treatment, impurities on the surface of the composite substrate are removed, which facilitates subsequent electrolysis.

[0020] A second aspect of this application provides a metal article comprising:

[0021] Composite substrate, including a stainless steel substrate layer and an aluminum alloy substrate layer; and

[0022] Holes are formed on the surface of the aluminum alloy substrate layer; wherein,

[0023] The hole is a micron-sized blind hole. The hole has an opening on the surface of the aluminum alloy substrate layer and a bottom located inside the aluminum alloy substrate layer. The diameter of the opening is larger than the inner diameter of the hole. The vertical distance between the plane where the opening is located and the bottom of the hole forms the hole depth. The hole is cut along the hole depth to obtain a cross-section. In the cross-section of the hole, the inner sidewall of the hole includes at least one notch.

[0024] The metal product provided in this application has micron-sized blind holes formed on the aluminum alloy substrate layer, and the diameter of the hole opening is larger than the inner diameter of the hole, which is conducive to the injection of plastic materials with high molecular chain rigidity and poor flowability. At the same time, a notch is provided on the inner sidewall of the hole, which is conducive to the plastic material injected into the notch tightly gripping the notch, thereby improving the bonding force between the plastic material and the aluminum alloy substrate layer.

[0025] According to some embodiments of this application, the orifice diameter ranges from 20μm to 200μm, and the orifice depth ranges from 20μm to 120μm.

[0026] According to some embodiments of this application, the hole is inclined, and the opening extends obliquely inward to the bottom of the hole relative to the plane where the opening is located. The inclined hole can further improve the bonding force between the injected plastic and the hole.

[0027] According to some embodiments of this application, the hole has an edge-spiked structure. The notches on the inner sidewall of the hole constitute the edge spikes. During injection molding of the hole, the notches exert a gripping force on the injected plastic, and the edge-spiked structure can improve the bonding force between the hole and the plastic.

[0028] According to some embodiments of this application, the pore density is 40% to 60%. By controlling the pore density, both the strength of the aluminum alloy substrate and the bonding force with the injected plastic can be considered.

[0029] A third aspect of this application provides a metal composite, comprising:

[0030] Metal products; and

[0031] Material layer; among which,

[0032] The metal product is the aforementioned metal product.

[0033] The aluminum alloy substrate layer in the metal product contains the material of the material layer through the holes, and the material layer is bonded to the metal product through the holes.

[0034] The purpose of this application in providing metal articles with pores is to solve the problem that plastics with high molecular chain rigidity and poor flowability cannot be injection molded into nanopores. However, it is understood that the metal articles provided in this application can also be used for injection molding of plastics with low molecular chain rigidity and good flowability. In addition, non-plastic materials such as glass and ceramics can also be selected for combination. The specific material layers to be combined can be selected according to actual needs.

[0035] According to some embodiments of this application, the material layer is a resin layer.

[0036] According to some embodiments of this application, the material of the resin layer is selected from at least one of polyether etherketone (PEEK), polyphenylene oxide (PPO), polyphenylene sulfide (PPS), polyamide (PA), polyimide, polyamide-imide (PAI), and polyacetal. Attached Figure Description

[0037] Figure 1 This is a schematic diagram illustrating selective pore formation on the composite substrate in some embodiments;

[0038] Figure 2 These are schematic diagrams of the metal product structure and enlarged views of the holes in the aluminum alloy substrate layer in some embodiments.

[0039] Figure 3 The image shows the metal articles prepared in Example 1-1 under a Keyence optical microscope.

[0040] Figure 4 Example 2-2: A photograph of a section of the aluminum alloy substrate layer in a metal product under a Keyence optical microscope;

[0041] Figure 5 This is a photograph of the surface of the aluminum alloy substrate layer in the metal product of Example 5-2 under a Keyence optical microscope;

[0042] Figure 6 The image shows the surface of the aluminum alloy substrate layer in the metal product of Example 5-3 under a Keyence optical microscope.

[0043] Figure 7a The image shows the pore morphology of the aluminum alloy substrate layer surface in the metal product of Example 6-2 under a Keyence optical microscope.

[0044] Figure 7b This is a Z-axis depth diagram of the hole on the surface of the aluminum alloy substrate layer in the metal product of Example 6-2 under a Keyence optical microscope;

[0045] Figure 8 The image shown is a photograph of the surface of the aluminum alloy substrate layer in the metal product of Example 6-3 under a Keyence optical microscope.

[0046] Figure 9 The image shows the surface of the aluminum alloy substrate layer in the metal product of Examples 6-4 under a Keyence optical microscope.

[0047] Figure 10 This is a magnified view of a portion of the surface of the aluminum alloy substrate layer in the metal product of Example 6-4, and the hole depth curve along the lines in the figure;

[0048] Figure 11 This is a magnified view of a portion of the surface of the aluminum alloy substrate layer in the metal product of Example 7-3, and the hole depth curve along the lines in the figure.

[0049] Explanation of main component symbols

[0050] Composite substrate 100

[0051] Stainless steel substrate layer 110

[0052] Aluminum alloy substrate layer 120

[0053] Hole 200

[0054] 210 orifice

[0055] Hole bottom 220

[0056] Notch 230

[0057] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0058] 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 skilled in the art without creative effort are within the scope of protection of this application.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. In this application, "several" means one or more.

[0060] Reference Figure 1 This application provides a method for selectively forming pores in a composite substrate, comprising the following steps:

[0061] A composite substrate 100, comprising a stainless steel substrate layer 110 and an aluminum alloy substrate layer 120, is placed in an electrolyte. Electrolysis is performed using the composite substrate 100 as the anode to form pores on the surface of the aluminum alloy substrate layer of the composite substrate.

[0062] The electrolyte used in electrolysis includes water, acids, alcohols, and chlorides that can dissociate into chloride ions in water. The acid provides anions that can react with the Al generated during electrolysis in the aluminum alloy substrate layer. 3+ Complexation occurs; among them,

[0063] The molar ratio of chloride ions dissociated from the acid and chloride ranges from 1:1 to 10:1. The chloride does not include ferric chloride. The electrolyte contains more than 50% water, and the mass concentration of alcohols ranges from 1% to 10%.

[0064] This application utilizes a suitable electrolyte formulation to electrochemically etch the composite substrate 100, which can form micron-sized pores on the aluminum alloy substrate layer 120 without damaging the stainless steel substrate layer 110. This allows for injection molding of resins with high molecular chain rigidity and poor flowability. In addition, the formed pores have adhesive pulling ability and can have a strong bonding force with the injection-molded resin.

[0065] In some embodiments, FeCl3 is not used as the chloride in the electrolyte because Fe 3+ It has oxidizing properties and may affect the formation of pores on aluminum alloys during the electrolysis process.

[0066] In some embodiments, the electrolyte contains more than 50% water by mass. A higher water content increases the degree of ion dissociation in the electrolyte, improves its conductivity, and also enhances ion migration rates, thereby resulting in better pores.

[0067] In some embodiments, the acid is selected from at least one of phosphoric acid, oxalic acid, lactic acid, and tartaric acid. The acid anion provided can complex with dissolved aluminum ions; for example, phosphate ions can complex with aluminum ions to form aluminum phosphate, which adheres to the surface of the aluminum alloy and prevents surface corrosion.

[0068] In some implementations, the mass concentration of the acid ranges from 2% to 8%.

[0069] In some embodiments, the alcohol is selected from at least one of propylene glycol, ethylene glycol, glycerol, and diethylene glycol. Alcohols provide high internal resistance, preventing excessive current during electrolysis and thus providing protection.

[0070] In some embodiments, the chloride is a soluble chloride salt, and the chloride is selected from at least one of NaCl, KCl, CuCl2, and FeCl2.

[0071] In some embodiments, the mass concentration of chloride ranges from 0.5% to 5%.

[0072] In some implementations, the applied current density during the electrolysis step is in the range of 1 A / dm³. 2 ~5A / dm 2 Using the electrolyte provided in this application, selective pore formation can be performed on aluminum alloys under low current conditions.

[0073] In some implementations, the electrolysis time is 10 to 30 minutes. By controlling the electrolysis time, the depth of the formed pores can be controlled.

[0074] In some embodiments, the temperature of the electrolyte is 20°C to 65°C.

[0075] In some embodiments, a surface treatment step is included before placing the composite substrate in the electrolyte. The surface treatment includes degreasing and black film stripping to remove impurities from the surface of the composite substrate, facilitating subsequent electrolysis.

[0076] In some embodiments, after electrolyzing the composite substrate, the process further includes peeling off the black film, cleaning, and drying the electrolyzed composite substrate, which facilitates injection molding on the electrolyzed composite substrate.

[0077] The method provided in this application allows for the selective formation of micron-sized blind holes on an aluminum alloy substrate layer. The resulting metal products with micron-sized blind holes simultaneously meet the requirements of injection molding and product strength. See also... Figure 2 , Figure 2 Schematic diagrams of the structure of a metal article and cross-sectional diagrams of holes in an aluminum alloy substrate layer are shown in some embodiments. The metal article includes a composite substrate 100 and holes 200. The composite substrate 100 includes a stainless steel substrate layer 110 and an aluminum alloy substrate layer 120. Holes 200 are formed on the surface of the aluminum alloy substrate layer 120. Holes 200 are micron-sized blind holes, having an orifice 210 opening onto the surface of the aluminum alloy substrate layer 120 and a bottom 220 located inside the aluminum alloy substrate layer 120. The orifice diameter 'a' of the hole 200 is larger than the inner diameter of the hole, facilitating resin injection. The perpendicular distance between the plane containing the orifice 210 and the plane containing the bottom 220 forms the hole depth. A cross-section of the hole 200 is obtained by cutting along the hole depth direction. In the cross-section of the hole 200, the inner wall of the hole 200 includes at least one notch 230. For resins with high molecular chain rigidity and poor flowability, it is often impossible to inject them into nanoscale pores. By forming micron-sized pores on the surface of the aluminum alloy substrate layer 120, it is beneficial to injection mold such resins. In addition, the inner sidewall of the pore 200 has a notch 230, which can improve the bonding force between the plastic and the aluminum alloy substrate layer 120.

[0078] In some embodiments, the orifice diameter a of the orifice 210 ranges from 20 μm to 200 μm, and the orifice depth b ranges from 20 μm to 120 μm.

[0079] In some embodiments, the hole 200 is inclined relative to the surface of the aluminum alloy substrate layer 120, and the hole opening 210 extends obliquely inward to the bottom 220 relative to the plane where the hole opening 210 is located. The inclined arrangement of the hole 200 on the surface of the aluminum alloy substrate layer 120 allows the plastic to enter the hole 200 during injection molding, and the inclined hole can increase the vertical pull-out force between the plastic and the hole 200 on the surface of the aluminum alloy substrate layer 120.

[0080] In some implementations, such as Figure 2 and Figure 4 As shown, the different holes 200 have different inclination directions relative to the surface of the aluminum alloy substrate layer 120. This setting allows the plastic injected into the holes 200 to have different inclination directions relative to the surface of the aluminum alloy substrate layer 120. The different inclination directions of the plastic have two advantages. First, the different inclination directions of the plastic will increase the pull-out force between the plastic and the aluminum alloy substrate layer 120, thereby improving the bonding strength of the product. Second, when subjected to an external force in a specific direction, the external force is dispersed by the plastic in different directions, thereby improving the impact resistance of the product.

[0081] In some embodiments, the hole 200 has an edge-spiked structure, meaning that the inner wall extending from the hole opening 210 to the hole bottom 220 has at least one notch 230, which forms a spike. The notch on the inner wall of the hole constitutes the edge spike, and during injection molding of the hole, the notch exerts a gripping force on the injected plastic. The edge-spiked structure can improve the bonding force between the hole and the plastic.

[0082] In some embodiments, the pore density of the holes 200 is 40% to 60%. By controlling the pore density, both the strength of the aluminum alloy substrate and the bonding force with the injected plastic can be considered.

[0083] This application also provides a metal composite, including the aforementioned metal article and material layer. The material layer contains material within the pores of the aluminum alloy substrate layer in the metal article, and the material layer is bonded to the metal article through these pores. The material layer is bonded to the aluminum alloy substrate layer by being fitted into the pores in the substrate layer.

[0084] In some embodiments, the material layer is a resin layer, which can be injected into the holes by injection molding, and after curing, an aluminum alloy composite is formed. The resin layer material includes, but is not limited to, polyetheretherketone (PEEK), polyphenylene oxide (PPO), polyphenylene sulfide (PPS), polyamide (PA), polyimide, polyamide-imide (PAI), and polyacetal.

[0085] The following describes the process of preparing a composite substrate using the selective pore-forming method of this application, with reference to specific embodiments. The composite substrate used is stainless steel 316 / aluminum alloy 6013, and the degreasing agent is a 35% NaOH aqueous solution.

[0086] Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-2

[0087] Examples 1-1 to 1-5 provide a series of metal articles prepared according to the following steps:

[0088] 1) Surface treatment: The composite substrate is placed in a 35% aqueous solution and ultrasonically cleaned for 3 minutes at 55℃, and then placed in 200±10g / L H2SO4 and 5±1g / L HNO3 to peel off the black film for 1 minute.

[0089] 2) In this example electrolyte, the acid is phosphoric acid, the alcohol is propylene glycol, and the chloride is NaCl. NaCl is dissolved in deionized water at room temperature (25°C), and then phosphoric acid and propylene glycol are added to form the electrolyte. By mass percentage, the propylene glycol content in the electrolytes of Examples 1-1 to 1-5 is 4%, and the contents of NaCl and phosphoric acid are shown in Table 1. The surface-treated composite substrate is placed in the prepared electrolyte, with the composite substrate as the anode and graphite as the cathode. The applied voltage is controlled to maintain a current density of 2 A / dm³. 2 Electrolysis for 20 minutes, followed by peeling off the black film for 1 minute, ultrasonic washing, and drying at 80°C to obtain the metal product.

[0090] Comparative Example 1: Comparative Example 1 provides a metal product, the preparation process of which is the same as that of Examples 1-5, except that the molar ratio of NaCl to phosphoric acid in the electrolyte is 3:1.

[0091] Comparative Example 2: Comparative Example 2 provides a metal product, the preparation process of which is the same as that of Examples 1-5, except that the molar ratio of NaCl to phosphoric acid in the electrolyte is 1:12.

[0092] The surface morphology of the metal products prepared in Examples 1-5 was observed using a Keyence optical microscope. After electrolytic etching, the side views of the composite substrates in Examples 1-5 all showed no pores in the stainless steel substrate layer, while pores were formed in the aluminum alloy substrate layer. Taking the metal product prepared in Example 1-1 as an example, its photograph under a Keyence optical microscope at 30x magnification is shown below. Figure 3 As shown, the upper stainless steel substrate layer was not corroded and no pores were found, while the lower aluminum alloy substrate layer showed black corrosion holes. The experimental results show that the method of this application can avoid stainless steel corrosion and selectively form pores on the aluminum alloy.

[0093] The morphology of the metal articles of Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-2 was observed using a Keyence optical microscope. The pore morphology characteristics of the aluminum alloy substrate layer surface are statistically shown in Table 1.

[0094] Table 1. Process parameters and morphological characteristics of holes in the aluminum alloy substrate layer of the examples and comparative examples.

[0095]

[0096]

[0097] As shown in Table 1, when the molar ratio of chloride ions to acid is controlled within the range of 1:1 to 1:10 in the embodiments of this application, micron-sized pores are formed on the surface of the aluminum alloy substrate with good pore morphology, and the pore density gradually increases with the increase of acid content. By comparing the comparative example and the embodiment, it can be seen that when the acid exceeds this molar ratio range, the aluminum alloy will be polished, and when the chloride ions exceed this molar ratio range, over-corrosion will occur. The principle of selectively forming holes on the surface of aluminum alloy substrates in this application is as follows: When the composite substrate is energized in the electrolyte provided in this application, since the conductivity of aluminum alloy is better than that of stainless steel, the current passes through the aluminum alloy first. A dense layer of aluminum oxide (containing Al-O bonds) will quickly form on the aluminum alloy, which will lead to a decrease in conductivity and short circuit by the stainless steel. After the current passes through, a passivation film will also form on the surface of the stainless steel. The main components of the passivation film are chromium oxide (containing Cr-O bonds) and nickel oxide (containing Ni-O bonds). Chloride ions ionized from soluble chloride salts in the electrolyte can act as corrosion ions to destroy the Al-O bonds in aluminum oxide under the action of the electric field, thereby forming pitting corrosion on the surface of aluminum alloy. However, the corrosion ions chloride ions have difficulty destroying Cr-O bonds and Ni-O bonds, so the stainless steel surface cannot be etched with holes. By controlling the molar ratio of chloride ions to acid, the morphology of pores on the aluminum alloy substrate is optimized. In addition, the alcohols in the electrolyte provide high internal resistance, which avoids excessive current during electrolysis and thus prevents surface corrosion of the aluminum alloy. The acid radicals provided by the acid in the electrolyte can complex with the dissolved aluminum ions and adhere to the aluminum alloy surface, thereby preventing surface corrosion of the aluminum alloy and facilitating selective pore formation on the aluminum alloy surface.

[0098] Examples 2-1 to 2-3 and Comparative Example 2-1

[0099] Examples 2-1 to 2-3 provide a series of metal products. The preparation process is the same as that of Examples 1-1 to 1-5. The only difference is that, by mass percentage, the electrolyte in Examples 2-1 to 2-3 contains 5% propylene glycol, 5% phosphoric acid, and the content of NaCl is shown in Table 2.

[0100] Comparative Example 2-1: Comparative Example 2-1 provides a metal product, the preparation process of which is the same as that of Examples 2-1 to 2-3, except that, by mass percentage, the electrolyte of Comparative Example 2-1 contains 5% propylene glycol, 5% phosphoric acid, and does not contain NaCl.

[0101] The surface morphology of the metal products prepared in Example 2-2 was observed using a Keyence optical microscope. No pores were found in the stainless steel substrate layer of the metal products. A cross-section of the aluminum alloy substrate layer was photographed at 1000 magnification under a Keyence optical microscope, as shown below. Figure 4 As shown in the figure, the hole morphology characteristics of the slices are as follows: [1] hole depth 85.86μm, [2] hole depth 65.57μm, [3] hole depth 58.44μm, [4] hole depth 38.47μm, [5] hole depth 26.11μm, [6] hole diameter 35.07μm, [7] hole diameter 60.92μm, [8] hole diameter 65.57μm. It can be seen from the figure that after electrolysis, several holes were formed on the aluminum alloy substrate layer in Example 2-2, and the hole diameter and hole depth are both in the micrometer range.

[0102] The surface morphology of the metal products prepared in Examples 2-1 to 2-3 and Comparative Example 2-1 was observed using a Keyence optical microscope. No pores were found in the stainless steel substrate layer of the metal products. The pore morphology characteristics of the aluminum alloy substrate layer are statistically shown in Table 2.

[0103] Table 2. Process parameters and morphological characteristics of holes in aluminum alloy substrate layers in Examples 2-1 to 2-3 and Comparative Example 2-1.

[0104]

[0105]

[0106] As can be seen from Table 2, the electrolyte used in Comparative Example 2-1 did not contain NaCl and could not form pores. However, the electrolyte with added NaCl used in the embodiments of this application can form micron-sized pores on the aluminum alloy surface. Increasing the concentration of chloride ions in the electrolyte is beneficial to increasing the pore size, but excessive chloride ion concentration will cause pore leakage. The appropriate chloride ion molar percentage is 0.5% to 5%.

[0107] Examples 3-1 to 3-4 and Comparative Example 3-1

[0108] Examples 3-1 to 3-4 and Comparative Example 3-1 provide a series of metal products. The preparation process is the same as that of Examples 1-1 to 1-5. The difference is that the chloride in the electrolyte of Examples 3-1 to 3-4 is CuCl2, and the acids are phosphoric acid, oxalic acid, lactic acid and tartaric acid, respectively. By mass percentage, the propylene glycol content in the electrolyte of Examples 3-1 to 3-4 is 5%, the CuCl2 content is 1.3%, and the acid content is shown in Table 3. The propylene glycol content in the electrolyte of Comparative Example 3-1 is 5%, the CuCl2 content is 1.3%, and it does not contain acid.

[0109] The surface morphology of the metal products prepared in Examples 3-1 to 3-4 and Comparative Example 3-1 was observed using a Keyence optical microscope. No pores were found in the stainless steel substrate layer of the metal products. The pore morphology characteristics of the aluminum alloy substrate layer are statistically shown in Table 3.

[0110] Table 3. Process parameters and morphological characteristics of holes in aluminum alloy substrate layers in Examples 3-1 to 3-4 and Comparative Example 3-1.

[0111]

[0112]

[0113] As can be seen from Table 3, the electrolyte used in Comparative Example 3-1, which did not contain added acid, was prone to surface corrosion during electrolysis, making it impossible to form pores. In contrast, the electrolyte provided in this application, containing added phosphoric acid, oxalic acid, lactic acid, or tartaric acid, provides H+. + At the same time, its corresponding anion can react with Al 3+ Complexation can be performed to prevent surface corrosion, and micron-sized pores can be formed on the surface of the aluminum alloy substrate layer, although there are differences in pore structure and density.

[0114] Examples 4-1 to 4-3 and Comparative Example 4-1

[0115] Examples 4-1 to 4-3 and Comparative Example 4-1 provide a series of composite substrates. The preparation process is the same as that of Examples 1-1 to 1-5. The difference is that the electrolyte in Examples 4-1 to 4-3 contains FeCl2 as chloride and propylene glycol, ethylene glycol and glycerol as alcohols, respectively. By mass percentage, the electrolyte in Examples 4-1 to 4-3 contains 1.27% FeCl2, 8% phosphoric acid and 5% alcohols, while the electrolyte in Comparative Example 4-1 contains 1.27% FeCl2, 8% phosphoric acid and no alcohols.

[0116] The surface morphology of the metal products prepared in Examples 4-1 to 4-3 and Comparative Example 4-1 was observed using a Keyence optical microscope. No pores were found in the stainless steel substrate layer of the metal products. The pore morphology characteristics of the aluminum alloy substrate layer are statistically shown in Table 3.

[0117] Table 4. Process parameters and morphological characteristics of holes in the aluminum alloy substrate layer in Examples 4-1 to 4-3 and Comparative Example 4-1.

[0118]

[0119] As can be seen from Table 4, the electrolyte used in Comparative Example 4-1 did not contain any alcohols, and the electrolysis process caused severe corrosion at the tip edge of the aluminum alloy, making it impossible to form pores. However, the alcohols added to the electrolyte provided in this embodiment can provide higher internal resistance, avoid excessive current during electrolysis, and facilitate the formation of micron-sized pores.

[0120] Examples 5-1 to 5-4

[0121] Examples 5-1 to 5-4 provide a series of metal products, prepared using the same methods as those in Examples 1-1 to 1-5, except that, by mass percentage, the electrolyte contains 8% propylene glycol, 1% NaCl, and 5% phosphoric acid. The current densities during electrolysis are set as shown in Table 5.

[0122] Figure 5 The image shows a 200x magnified photograph of the surface of the aluminum alloy substrate layer in the metal product prepared in Example 5-2 under a Keyence optical microscope. The pore morphology features in the image are as follows: [1] pore diameter 141.1 μm, [2] pore diameter 154.2 μm, [3] pore diameter 96.8 μm, [4] pore diameter 126.2 μm, [5] pore diameter 159.3 μm, [6] pore diameter 136.3 μm, [7] pore diameter 112.3 μm, [8] pore diameter 91.1 μm. It can be seen from the image that after electrolysis, the surface of the aluminum alloy substrate layer in Example 5-2 has uniform pores, with a pore density of about 40%.

[0123] Figure 6 The image shown is a 300x magnified photograph of the surface of the aluminum alloy substrate layer in the composite substrate prepared in Examples 5-3 under a Keyence optical microscope.

[0124] The surface morphology of the metal products prepared in Examples 5-1 to 5-4 was observed using a Keyence optical microscope. No pores were found in the stainless steel substrate layer of the metal products. The pore morphology characteristics of the aluminum alloy substrate layer are statistically shown in Table 5.

[0125] Table 5. Process parameters and morphological characteristics of holes in aluminum alloy substrate layers in Examples 5-1 to 5-4.

[0126]

[0127]

[0128] As can be seen from Table 5, the pore size of micron-sized pores can be controlled by controlling the applied current density during the electrolysis process. When the current density is too high, pore leakage will occur.

[0129] Examples 6-1 to 6-5

[0130] Examples 6-1 to 6-5 provide a series of composite substrates, prepared using the same methods as Examples 1-1 to 1-5, except that, by mass percentage, the electrolyte contains 4% propylene glycol, 1% NaCl, and 5% phosphoric acid. The electrolysis times are set as shown in Table 6.

[0131] Figure 7a and Figure 7b This image shows a 300x magnified photograph of the surface of the aluminum alloy substrate layer in the metal article prepared in Example 6-2 under a Keyence optical microscope. Figure 7a The aperture morphology of the holes formed on the surface of the aluminum alloy substrate layer is shown. Figure 7b The Z-axis depths of the holes formed on the surface of the aluminum alloy substrate layer are shown, where the hole depths are 50.03 μm at [1], 53.14 μm at [2], 58.05 μm at [3], 53.12 μm at [4], 48.96 μm at [5], 60.57 μm at [6], 59.44 μm at [7], and 47.22 μm at [8]. The results show that the hole openings and hole depths are approximately similar, indicating that the holes formed on the surface of the aluminum alloy substrate layer are uniform.

[0132] Figure 8 The image shown is a 300x magnified photograph of the surface of the aluminum alloy substrate layer in the metal product prepared in Examples 6-3, under a Keyence optical microscope, showing that some of the formed holes have relatively large diameters.

[0133] Figure 9 This image shows a 200x magnified photograph of the surface of the aluminum alloy substrate layer in the metal articles prepared in Examples 6-4 using a Keyence optical microscope. Figure 10 The diagram shows a partial enlarged view of the surface of the aluminum alloy substrate layer in Examples 6-4 and a hole depth curve along the lines in the diagram. The maximum hole depth shown is 71.21 μm.

[0134] The surface morphology of the composite substrates prepared in Examples 6-1 to 6-5 was observed using a Keyence optical microscope. No pores were found in the stainless steel substrate layer of the metal products. The pore morphology characteristics of the aluminum alloy substrate layer are statistically shown in Table 6.

[0135] Table 6. Process parameters and morphological characteristics of holes in aluminum alloy substrate layers in Examples 6-1 to 6-5.

[0136]

[0137]

[0138] As can be seen from Table 6, micron-sized pores were formed on the surface of the aluminum alloy substrate layer of the composite substrate in Examples 6-1 to 6-5, but there were certain differences in the pore depth. The experimental results showed that the pore depth increased with the increase of electrolysis time, and the pore depth could be effectively controlled by controlling the electrolysis time.

[0139] Examples 7-1 to 7-4 and Comparative Examples 7-1 to 7-2

[0140] Examples 7-1 to 7-4 and Comparative Examples 7-1 to 7-2 provide a series of metal products. The preparation process is the same as that of Examples 1-1 to 1-5. The difference is that the electrolyte in Examples 7-1 to 7-4 and Comparative Examples 7-1 to 7-2 contains 2% NaCl, 5% phosphoric acid, and the contents of propylene glycol are shown in Table 7.

[0141] The surface morphology of the metal products prepared in Examples 7-1 to 7-4 and Comparative Examples 7-1 to 7-2 was observed using a Keyence optical microscope. In the metal products of Comparative Examples 7-1 to 7-2, pores appeared in both the stainless steel substrate layer and the aluminum alloy substrate layer. In the metal products of Examples 7-1 to 7-4, no pores appeared in the stainless steel substrate layer. The morphological characteristics of the pores on the aluminum alloy substrate layer are statistically shown in Table 7.

[0142] Figure 11 The diagram shows a partial magnified view of the surface of the aluminum alloy substrate layer in the metal product prepared in Examples 7-3, and a hole depth curve along the lines in the diagram. The maximum hole depth shown is 44.47 μm.

[0143] Table 7. Process parameters and morphological characteristics of holes in aluminum alloy substrate layers in Examples 7-1 to 7-4 and Comparative Examples 7-1 to 7-2.

[0144]

[0145]

[0146] As shown in Table 7, Examples 7-1 to 7-4 of this application can form uniform pores on the surface of the aluminum alloy substrate. While Comparative Examples 7-1 to 7-2 can also form pores, their selectivity is poor. They not only form pores on the aluminum alloy substrate but also exhibit uneven corrosion on the stainless steel substrate, with more corrosion on the aluminum alloy substrate. Experimental results indicate that controlling the alcohol content to no more than 10% is optimal; excessive alcohol content will cause stainless steel corrosion and reduce the selectivity for corroding aluminum alloys. The main reason is that the principle of pore formation is that chloride ions in the electrolyte break down aluminum chloride into pores under the action of an electric field. Compared to Examples 7-1 to 7-4, the electrolyte in Comparative Examples 7-1 to 7-2 has a higher propylene glycol content, leading to increased electrolyte resistance and voltage, insufficient corrosion inhibition function of the corrosion inhibitor, and over-corrosion of the aluminum alloy.

[0147] Example 8-1 and Comparative Examples 8-1 to 8-2

[0148] Example 8-1: An electrolyte was prepared by mixing 3% phosphoric acid, 2% NaCl, 5% propylene glycol, and 90% pure water by weight percentage. A clean composite substrate was placed in the electrolyte, with the composite substrate as the anode and graphite as the cathode, and the applied current density was controlled at 3 A / dm³. 2 Then, the black film is peeled off for 1 minute, ultrasonically washed with water, and dried at 80°C to obtain the composite substrate.

[0149] Comparative Example 8-1: An electrolyte was prepared by mixing 40% ethylene glycol, 8% sodium phosphate, 5% phosphoric acid, 2% NaCl, and 45% pure water (by molar percentage). A clean composite substrate was placed in the electrolyte, with the composite substrate as the anode and graphite as the cathode, and the applied current density was controlled at 3 A / dm³. 2 Then, the black film is peeled off for 1 minute, ultrasonically washed with water, and dried at 80°C to obtain the composite substrate.

[0150] Comparative Example 8-2: An electrolyte was prepared by mixing 30% propylene glycol, 8% sodium hexametaphosphate, 15% phosphoric acid, 2% NaCl, and 45% pure water (by molar percentage). The composite substrate was placed in the electrolyte, with the composite substrate as the anode and graphite as the cathode, and the applied current density was controlled at 3 A / dm³. 2 Then peel off the black film for 1 minute, ultrasonically wash with water, and dry at 80℃ to obtain the metal product.

[0151] The surface morphology of the metal products prepared in Examples 8-1 and Comparative Examples 81 to 8-2 was observed using a Keyence optical microscope. The experimental results showed that the stainless steel in Comparative Example 8 exhibited uneven pores, and the aluminum alloy showed over-corrosion. The stainless steel in Comparative Example 9 also showed uneven pores, and the aluminum alloy also showed over-corrosion. However, no pores appeared in the stainless steel of the metal product in Example 8-1, while uniform pores appeared in the aluminum alloy. This application designed a large series of experiments. The electrolyte formulation in Comparative Example 8-1 was adjusted to 40%-60% ethylene glycol, 5%-10% sodium phosphate, 5%-10% phosphoric acid, 2%-8% NaCl, and 12%-48% pure water by molar percentage. The composite substrate was then placed in the above series of electrolytes for electrolysis. In all cases, uneven pores appeared on the stainless steel, and the aluminum alloy showed over-corrosion. Using a molar percentage method, the electrolyte formulation in Comparative Example 8-2 was adjusted to 30%-50% propylene glycol, 5%-10% sodium hexametaphosphate, 15%-20% phosphoric acid, 2%-8% NaCl, and 12%-48% pure water. When the composite substrate was electrolyzed in these electrolytes, uneven pores appeared on the stainless steel, and over-corrosion occurred on the aluminum alloy. Reducing the propylene glycol content in the adjusted electrolyte formulation resulted in lower resistance, but experiments showed it was difficult to create good pores on the aluminum alloy. Comparative analysis of Comparative Examples 8-1, 8-2, and the electrolyte formulation of this application reveals that the comparative examples increased the content of alcohols (ethylene glycol or propylene glycol) in their electrolyte formulations, causing uneven corrosion of stainless steel alongside aluminum alloy, resulting in poor selectivity for the corroded materials. In contrast, this application, by controlling the alcohol content in the electrolyte formulation, can effectively and selectively create pores on the aluminum alloy.

[0152] The above description is merely a preferred embodiment of this application and is not intended to limit this application in any way. Although the preferred embodiment has been disclosed above, it is not intended to limit this application. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A method for selectively forming pores in a composite substrate, comprising the following steps: A composite substrate, comprising a stainless steel substrate layer and an aluminum alloy substrate layer, is placed in an electrolyte. Electrolysis is performed using the composite substrate as the anode to form pores on the surface of the aluminum alloy substrate layer. The electrolyte used in the electrolysis includes water, acid, alcohol, and chloride that can dissociate into chloride ions in water. The acid provides anions that can react with the Al generated during electrolysis in the aluminum alloy substrate layer. 3+ Complexation occurs; among them, In the electrolysis step, the applied current density ranges from 1 A / dm³. 2 ~5A / dm 2 The electrolysis time is 10 min to 30 min, the electrolyte temperature is 20℃ to 65℃, the acid is selected from at least one of phosphoric acid, oxalic acid, lactic acid, and tartaric acid, the alcohol is selected from at least one of propylene glycol, ethylene glycol, glycerol, and diethylene glycol, the chloride is a soluble chloride salt, and the chloride is selected from at least one of NaCl, KCl, CuCl2, and FeCl2. The molar ratio of chloride ions dissociated from the acid and the chloride is in the range of 1:1 to 10:1, and the mass concentration of the alcohol is in the range of 1% to 10%.

2. The method according to claim 1, wherein, The mass concentration of the acid is in the range of 2%-8%.

3. The method according to any one of claims 1 to 2, wherein, The mass concentration of the chloride is in the range of 0.5% to 5%.

4. A metal article comprising: Composite substrate, including a stainless steel substrate layer and an aluminum alloy substrate layer; and Holes are formed on the surface of the aluminum alloy substrate layer; wherein, The hole is prepared by the method of any one of claims 1-3. The hole is a micron-sized blind hole. The hole has an opening on the surface of the aluminum alloy substrate layer and a bottom located inside the aluminum alloy substrate layer. The diameter of the opening is larger than the inner diameter of the hole. The vertical distance between the plane where the opening is located and the bottom of the hole forms the hole depth. The hole is cut along the hole depth to obtain a cross-section of the hole. In the cross-section of the hole, the inner wall of the hole includes at least one notch.

5. The metal article according to claim 4, wherein, The orifice diameter ranges from 20μm to 200μm, and the orifice depth ranges from 20μm to 120μm.

6. The metal article according to claim 4, wherein, The hole is inclined, and relative to the plane where the hole opening is located, the hole opening extends obliquely inward to the bottom of the hole.

7. The metal article according to claim 4, wherein, The hole has an edge spike-like structure.

8. The metal article according to claim 4, wherein, The pore density is 40%~60%.

9. A metal composite comprising: Metal products; and Material layer; among which, The metal article is the metal article according to any one of claims 4 to 8. The aluminum alloy substrate layer in the metal product contains the material of the material layer through the holes, and the material layer is bonded to the metal product through the holes.

10. The metal composite according to claim 9, wherein, The material layer is a resin layer.

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