Aluminum alloy sheet, method for producing the same, and brake pad

Abstract

The application provides an aluminum alloy plate and a preparation method thereof and a brake pad. The method comprises the following steps: adding metal raw materials, silicon nitride particles and an organic metal adhesive according to the chemical composition of the aluminum alloy plate, and performing die casting and forming to obtain an aluminum alloy base; and performing micro-arc oxidation on the aluminum alloy base to form a film layer, so as to obtain the aluminum alloy plate. The aluminum alloy plate prepared by the preparation method realizes the balance between strength and light weight, and has good corrosion resistance, wear resistance and oxidation resistance.

Description

Technical Field

[0001] This application relates to the field of aluminum alloy sheet technology, specifically to an aluminum alloy sheet, its preparation method, and brake pads. Background Technology

[0002] With the global automotive industry's increasing demand for lightweighting, reducing vehicle weight has become a trend in the field. As an important component of a vehicle's unsprung mass and a rotating part, reducing the weight of the brake disc can not only significantly reduce rotational inertia but also further reduce vibration and noise, improving handling stability and ride comfort.

[0003] In brake pad applications, cast iron is the traditional material. While it has high heat capacity and wear resistance, its weight poses a challenge to the overall lightweighting and performance of the vehicle. Furthermore, cast iron has relatively poor heat dissipation at high temperatures, easily accumulating heat during prolonged braking, thus affecting braking performance and safety.

[0004] To overcome the aforementioned problems, other alloy materials, such as aluminum-based composites, have been extensively studied. However, the compositional characteristics of these composites lead to complex friction mechanisms, making composite brake discs prone to uneven wear and thermal stress concentration during friction. This further poses a significant challenge to the development of matching brake pads or brake calipers. Therefore, there is an urgent need to develop a high-efficiency, wear-resistant brake pad or material suitable for aluminum alloy sheet brake discs to solve the problems in existing technologies. Summary of the Invention

[0005] This application provides an aluminum alloy sheet, a method for preparing the same, and a brake pad. The aluminum alloy sheet prepared by this method achieves a balance between strength and lightweight, and has good corrosion resistance, wear resistance, and oxidation resistance.

[0006] In a first aspect, embodiments of this application provide a method for preparing an aluminum alloy sheet, the method comprising:

[0007] Based on the chemical composition of aluminum alloy sheets, metal raw materials, silicon nitride particles, and organometallic binders are added, followed by die casting and molding to obtain an aluminum alloy matrix.

[0008] The aluminum alloy substrate is subjected to micro-arc oxidation to form a film layer, thereby obtaining the aluminum alloy sheet, wherein the film layer is a silicon-containing ceramic oxide film.

[0009] In some optional embodiments, the metal raw material includes one or more of Al alloys, Mg alloys, Mn alloys, elemental Al, elemental Mg, and elemental Mn. The step of adding the metal raw material, silicon nitride particles, and organometallic binder according to the chemical composition of the aluminum alloy sheet, followed by die casting and molding to obtain the aluminum alloy matrix, includes:

[0010] The aluminum alloy matrix is ​​provided with metal raw materials and silicon nitride particles according to the chemical composition of the aluminum alloy matrix. The aluminum alloy matrix includes the following chemical composition by mass percentage: Mg: 1.5% to 2.5%, Mn: 0.1% to 0.3%, Si3N4: 15% to 30%, balance Al and unavoidable impurities, and the impurity content is ≤0.02%.

[0011] 100 parts by weight of metal raw material are melted at 700 to 800°C to obtain molten metal;

[0012] Silicon nitride particles and organometallic binders are mixed under heating conditions to obtain a framework material;

[0013] The molten metal is mixed with 20 to 30 parts by weight of the skeleton material at a temperature of 80 to 120°C, and then cast and pressurized until solidification is applied to obtain an aluminum alloy matrix.

[0014] In some optional embodiments, the mass ratio of the silicon nitride particles to the organometallic binder is 1:(0.2 to 0.3).

[0015] In some optional embodiments, the micro-arc oxidation of the aluminum alloy substrate to form a film layer to obtain the aluminum alloy sheet includes: in an oxidation solution, using the aluminum alloy substrate as the anode and the stainless steel plate as the cathode, with a current density of 28 ± 0.3 mA / cm². 2 The aluminum alloy sheet is obtained by applying an electric current for 35 to 55 minutes to form a film layer, wherein the oxidation solution includes sodium silicate solution and silica sol.

[0016] In some optional embodiments, before performing micro-arc oxidation on the aluminum alloy substrate to form a film layer and obtain the aluminum alloy sheet, the method further includes: degreasing the aluminum alloy substrate at room temperature using an aqueous solution containing sodium hydroxide and sodium phosphate, followed by activating the aluminum alloy substrate at 40 to 65°C using an aqueous solution containing sodium fluoride.

[0017] In some optional embodiments, the aqueous solution containing sodium hydroxide and sodium phosphate has a mass fraction of 3% to 5% for sodium hydroxide and sodium phosphate, respectively; and the degreasing time is 3-8 minutes.

[0018] In some optional embodiments, the aqueous solution containing sodium fluoride has a sodium fluoride mass fraction of 18% to 22%; and the activation time is 10 to 15 minutes.

[0019] Secondly, embodiments of this application provide an aluminum alloy sheet, which is prepared by the method described in the first aspect. The aluminum alloy sheet includes an aluminum alloy substrate and a film layer disposed on the surface of the aluminum alloy substrate. The aluminum alloy substrate comprises the following chemical components by mass percentage: Mg: 1.5% to 2.5%, Mn: 0.1% to 0.3%, Si3N4: 15% to 30%, with the balance being Al and unavoidable impurities, and the impurity content being ≤0.02%. The film layer is a silicon-containing ceramic oxide film.

[0020] In some optional embodiments, the film thickness is 24 to 28 μm; the surface Vickers hardness of the film is 1200 HV to 1300 HV; and the bonding strength between the aluminum alloy substrate and the film is 40 to 75 MPa.

[0021] The mechanical properties of the aluminum alloy sheet meet the following requirements: longitudinal elongation ≥ 10%, transverse elongation ≥ 8%, and compressive strength at break ≥ 550 MPa.

[0022] Thirdly, embodiments of this application provide a brake pad, which is manufactured according to a brake pad manufacturing model by the method described in the first aspect or by an aluminum alloy sheet as described in the second aspect.

[0023] The method for preparing aluminum alloy sheet in this application embodiment produces an aluminum alloy substrate comprising aluminum and Si3N4, giving the substrate good hardness and tensile strength. The film layer disposed on the surface of the aluminum alloy substrate also exhibits good hardness and tensile strength, low brittleness, and is not easily worn and is corrosion resistant. Furthermore, the in-situ formation of this film layer enhances the compatibility between the aluminum alloy substrate and the film layer, reducing the risk of abnormal wear and film layer separation. The in-situ formation of the film layer on the surface of the aluminum alloy substrate reduces scratches on the substrate by hard friction materials, improving the service life of the brake pads and achieving weight reduction. Traditional cast iron discs absorb frictional heat due to their high heat capacity, while the aluminum alloy sheet dissipates heat quickly, improving braking performance. The use of an organometallic binder to prepare the aluminum alloy substrate improves the stability of the aluminum alloy sheet. The high bonding strength between the aluminum alloy substrate and the film layer indicates that the film layer is formed in situ and can provide long-term protection to the aluminum alloy substrate, further improving the wear resistance and corrosion resistance of the aluminum alloy sheet. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0025] Figure 1 An external view of the aluminum alloy sheet of Embodiment 1 of this application is shown.

[0026] Figure 2 A schematic diagram of the overall structure of a braking assembly according to an embodiment of this application is shown.

[0027] Figure 3 A half-sectional structural schematic diagram of a braking assembly according to an embodiment of this application is shown.

[0028] 1. Protective cover; 2. Brake disc; 3. Brake pads.

[0029] The accompanying drawings have illustrated specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to specific embodiments. Detailed Implementation

[0030] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0031] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0033] Currently, it is difficult to achieve lightweighting of cast iron brake pads, and aluminum-based brake pads have problems such as easy surface wear and poor corrosion resistance.

[0034] Research has shown that micro-arc oxidation of aluminum alloy substrates can form a film layer in situ on the surface of the aluminum alloy substrate, improving its corrosion resistance. Furthermore, the resulting aluminum alloy substrate is lightweight and has high strength, which can meet the requirements for lightweight brake pad materials.

[0035] This application provides a method for preparing an aluminum alloy sheet, the method comprising steps 100 to 200.

[0036] Step 100: Add metal raw materials, silicon nitride particles, and organometallic binders according to the chemical composition of the aluminum alloy sheet, and perform die casting and molding to obtain an aluminum alloy matrix.

[0037] The metallic raw materials used in this step include Al alloys, Mg alloys, Mn alloys, as well as elemental Al, elemental Mg, and elemental Mn. The metallic raw materials can be Al-Mg alloys and Al-Mn alloys.

[0038] In this step, the raw materials for preparing aluminum alloy sheets are widely available and inexpensive. The materials used are low-toxicity and environmentally friendly, and the preparation process is simple and efficient, reducing environmental pollution during the process.

[0039] In this step, an aluminum alloy matrix is ​​prepared using metal raw materials, silicon nitride particles, and organometallic binders. This matrix has good hardness, tensile strength, thermal conductivity, and wear resistance, and facilitates frictional heat dissipation.

[0040] By precisely controlling the proportions of aluminum, magnesium, and manganese in the aluminum alloy matrix, the strength and hardness of the material can be significantly improved. The addition of magnesium increases the hardness and tensile strength of the aluminum alloy, while manganese helps to improve its wear resistance and corrosion resistance. The introduction of Si3N4 particles as a reinforcing phase can effectively improve the overall hardness and wear resistance of the material.

[0041] Step 200: Perform micro-arc oxidation on the aluminum alloy substrate to form a film layer, thereby obtaining the aluminum alloy sheet, wherein the film layer is a silicon-containing ceramic oxide film.

[0042] In this step, a silicon-containing ceramic oxide film is formed in situ on the surface of the aluminum alloy substrate through micro-arc oxidation treatment. This not only enhances the surface hardness and wear resistance, but also significantly improves the corrosion resistance, enabling the aluminum alloy sheet to maintain good performance in harsh environments and avoid damage caused by hard materials.

[0043] In this step, the aluminum alloy substrate is subjected to micro-arc oxidation to form a film layer, which ensures that no ablation will occur during the process. The film layer is firmly bonded to the aluminum alloy substrate, resulting in higher consistency in surface treatment color and a dense and uniform structure, further protecting the rare earth magnesium alloy substrate from corrosion.

[0044] The porosity of the film surface is lower than that of the aluminum alloy substrate, thus giving it stronger corrosion resistance than untreated rare earth magnesium alloys. Micro-arc oxidation treatment creates a film layer on the surface of the aluminum alloy substrate that is high in hardness, wear resistance, toughness, strong adhesion to the substrate, corrosion resistance, high-temperature oxidation resistance, and insulation. This film is particularly suitable for high-speed, lightweight metal alloy components requiring high wear resistance, corrosion resistance, and high-temperature impact resistance, such as brake pads.

[0045] Organometallic binders can be copper-containing organic compounds, organoiron compounds, MoS2 / graphite-doped organometallic polymers, or copper-free formulations of potassium titanate whiskers (K2O·6TiO2) and bio-based resins (such as soybean oil epoxy resin). NAO-type organometallic binders can be mixtures of potassium titanate whiskers (K2O·6TiO2) and bio-based resins (such as soybean oil epoxy resin).

[0046] Organometallic binders can improve the bonding performance between metal raw materials and Si3N4 particles, as well as the bonding performance between multiple Si3N4 particles. This facilitates the formation of a continuously distributed preform of Si3N4 particles in the initial stage, reduces particle agglomeration, minimizes interfacial defects between Si3N4 particles and metal raw materials, and improves the overall performance of the composite material. Copper-containing organic compounds and organoferric compounds can form more stable bonds with the metal matrix through chemical bonds, while MoS2 / graphite-doped organometallic polymers can provide additional lubricity and wear resistance. Copper-free binder formulations avoid the environmental problems and health risks associated with copper.

[0047] As an example, Figure 1 An external view of an aluminum alloy sheet according to an embodiment is shown. The overall appearance of the aluminum alloy sheet can be seen from the figure.

[0048] In some optional embodiments, the metal raw material includes one or more of Al alloys, Mg alloys, Mn alloys, elemental Al, elemental Mg, and elemental Mn. Step 100, which involves adding metal raw materials, silicon nitride particles, and organometallic binders according to the chemical composition of the aluminum alloy sheet, followed by die casting and molding to obtain an aluminum alloy matrix, includes:

[0049] Step 110: Provide metal raw materials and silicon nitride particles according to the chemical composition of the aluminum alloy matrix. The aluminum alloy matrix includes the following chemical composition by mass percentage: Mg: 1.5% to 2.5%, Mn: 0.1% to 0.3%, Si3N4: 15% to 30%, with the balance being Al and unavoidable impurities, and the impurity content is ≤0.02%.

[0050] Step 120: Melt 100 parts by weight of the metal raw material at 700 to 800°C to obtain the molten metal;

[0051] This step, through the combination of a unique alloy composition design and a surface ceramic film layer, significantly improves the material's corrosion resistance, wear resistance, and strength, while maintaining good plasticity.

[0052] Step 130: Mix silicon nitride particles and organometallic binder under heating conditions to obtain a skeleton material;

[0053] In this step, silicon nitride particles and organometallic binders in the skeleton material can form a continuous preform structure. This preform structure can effectively disperse stress. Compared with dispersed silicon nitride particles, which do not form a preform structure, this can prevent local stress concentration, delay microcrack propagation, improve overall fracture toughness, enhance impact resistance, and extend the service life of brake pads.

[0054] In this step, the silicon nitride particles in the skeleton material can be in the form of dispersed particles. These dispersed particles can act as a reinforcing phase, and their reinforcing effect is limited by interfacial bonding and particle distribution uniformity. Under stress, weak interfacial detachment or particle separation can easily occur, leading to interruption of stress transmission. The metallic materials in the aluminum alloy can form thermal conduction channels, improving the overall thermal conductivity and facilitating rapid heat dissipation. These dispersed particles help reduce the thermal fade effect during braking and maintain a stable coefficient of friction. As a reinforcing phase in the metallic material, the dispersed particles improve friction resistance, reduce heat accumulation, and prevent the aluminum alloy from softening or failing due to thermal fatigue at high temperatures.

[0055] The molten metal is mixed with 20 to 30 parts by weight of the skeleton material at a temperature of 80 to 120°C, and then cast and pressurized until solidification is applied to obtain an aluminum alloy matrix.

[0056] In this embodiment, the mass ratio of metal raw material to skeleton material is 100:(20-30). This effectively improves stiffness, strength, and wear resistance without causing the material to become too brittle. An excessively high Si3N4 content increases crack initiation and fracture failure, reducing impact resistance. A suitable amount of Si3N4 (20-30%) improves the connectivity of thermal conductivity paths and enhances heat dissipation efficiency. Furthermore, excessively high Si3N4 content hinders aluminum penetration, leading to significant fluctuations in finished product quality.

[0057] In some optional embodiments, the mass ratio of the silicon nitride particles to the organometallic binder is 1:(0.2 to 0.3).

[0058] Maintaining a mass ratio of silicon nitride particles to the aforementioned organometallic binder ensures a good bond between the silicon nitride particles and the aluminum alloy matrix. This avoids a decrease in mechanical properties due to excessive binder or a weak interfacial bond due to insufficient binder. As a reinforcing phase, the high hardness and good thermal stability of the silicon nitride particles significantly improve the wear resistance and heat resistance of the aluminum alloy matrix, while the organometallic binder acts as a bridge, strengthening the bond between the reinforcing phase and the aluminum metal matrix.

[0059] Compared to SiC particles, Si3N4 in this application is a ceramic material with a well-defined stoichiometric ratio and stable structure; SiN has an unstable structure and fluctuates significantly in performance; Si3N4 maintains good mechanical properties and a low coefficient of thermal expansion even at high temperatures, which is particularly important under high-temperature conditions during braking, as amorphous SiN may experience performance degradation at high temperatures due to its loose structure; Si3N4 particles can form tiny solid lubrication points in composite materials without breaking, improving frictional stability during braking; Si3N4 bonds well with metal matrices (such as aluminum alloys), forming a strong interface and improving overall mechanical strength. Irregularly structured or highly variable SiN may lead to poor interfacial bonding and defects.

[0060] In some optional embodiments, the micro-arc oxidation of the aluminum alloy substrate to form a film layer to obtain the aluminum alloy sheet includes: in an oxidation solution, using the aluminum alloy substrate as the anode and the stainless steel plate as the cathode, with a current density of 28 ± 0.3 mA / cm². 2 The aluminum alloy sheet is obtained by applying an electric current for 35 to 55 minutes to form a film layer, wherein the oxidation solution includes sodium silicate solution and silica sol.

[0061] The micro-arc oxidation process used in this application processes aluminum alloy sheets to produce aluminum alloy sheets with high hardness, high wear resistance, strong film-substrate adhesion, and corrosion resistance. These sheets can be applied in industries such as aviation, aerospace, weaponry, automobiles, ships, machinery, petroleum, chemical, medical, and electronics.

[0062] In sodium silicate solutions, the concentration of sodium silicate can range from 2 g / L to 18 g / L.

[0063] Silica sol is a key additive, typically used in conjunction with sodium silicate (Na₂SiO₃) solution to form an electrolyte system. Silica sol is a colloidal solution formed by dispersing nano-sized silica (SiO₂) particles in water or an organic solvent. Its main component is amorphous SiO₂ (particle size typically 5–50 nm), and its pH value is typically 9–11 (alkaline to prevent particle aggregation). Optionally, silica sol may include a stabilizer, which can be Na₂SiO₃. + K + or NH4 +This helps maintain the stability of the colloid.

[0064] Therefore, the surface treatment color of the film layer and the aluminum alloy substrate are more consistent, the structure is dense and uniform, and the porosity of the resulting film layer is ≤2%. The film layer thickness is 24 to 28 μm, and can be selected as 25 to 27 μm. Furthermore, the film layer withstands neutral salt spray tests for over 130 hours, demonstrating strong corrosion resistance.

[0065] For example, after connecting with aluminum wire, the aluminum alloy substrate is placed in the electrolytic cell, the frequency of the equipment is set to 300-500Hz, the pulse type is 20:9, the stirring system and cooling system are turned on, the power supply is modulated from 0V to 220V, and the current is reduced to 2A / dm. 2 The voltage is increased to 410±5V at a rate of 20V / min, and then controlled at 20-25℃ while maintaining the above current density to reduce the voltage, thereby obtaining a micro-arc oxidized aluminum alloy sheet, wherein a film layer is formed on the surface of the aluminum alloy substrate.

[0066] After micro-arc oxidation, aluminum alloy sheets can be sealed and dried.

[0067] In some optional embodiments, before performing micro-arc oxidation on the aluminum alloy substrate to form a film layer and obtain the aluminum alloy sheet, the method further includes: degreasing the aluminum alloy substrate at room temperature using an aqueous solution containing sodium hydroxide and sodium phosphate, followed by activating the aluminum alloy substrate at 40 to 65°C using an aqueous solution containing sodium fluoride.

[0068] Using sodium fluoride (NaF) aqueous solution for degreasing and activation is a common pretreatment method. Its core purpose is to generate discontinuous magnesium fluoride (MgF2) on the surface of magnesium alloy through chemical reaction, while removing surface grease and oxides.

[0069] NaF solution is weakly alkaline (pH≈8~10), which can saponify surface grease (reacting with esters to form water-soluble soap) and dissolve adsorbed organic impurities. The natural oxide film on the aluminum alloy surface, composed of magnesium fluoride, is porous and can react with NaF to form more stable MgF2, partially exposing the fresh metal surface. This magnesium fluoride film acts as a transition layer, reducing the initial breakdown voltage, promoting discharge uniformity, facilitating subsequent micro-arc oxidation, and reducing the porosity of the film formed by micro-arc oxidation; it can also inhibit the rapid corrosion of the magnesium substrate and prevent the conversion solution (such as phosphate) from failing due to a sudden increase in local pH.

[0070] In some optional embodiments, the aqueous solution containing sodium hydroxide and sodium phosphate has a mass fraction of 3% to 5% for sodium hydroxide and sodium phosphate, respectively; and the degreasing time is 3-8 minutes.

[0071] In some optional embodiments, the aqueous solution containing sodium fluoride has a sodium fluoride mass fraction of 18% to 22%; and the activation time is 10 to 15 minutes.

[0072] Secondly, embodiments of this application provide an aluminum alloy sheet, which is prepared by the method described in the first aspect. The aluminum alloy sheet includes an aluminum alloy substrate and a film layer disposed on the surface of the aluminum alloy substrate. The aluminum alloy substrate comprises the following chemical composition by mass percentage: Mg: 1.5% to 2.5%, Mn: 0.1% to 0.3%, Si3N4: 15% to 30%, with the balance being Al and unavoidable impurities, and the impurity content is ≤0.02%.

[0073] In some optional embodiments, the film thickness is 24 to 28 μm; the surface Vickers hardness of the film is 1200 HV to 1300 HV; and the bonding strength between the aluminum alloy substrate and the film is 40 to 75 MPa.

[0074] Thirdly, embodiments of this application provide a brake pad, which is manufactured according to a brake pad manufacturing model by the method described in the first aspect or by an aluminum alloy sheet as described in the second aspect.

[0075] In some optional embodiments, the neutral salt spray test of the membrane layer is ≥130h, or optionally ≥230h. For example, the neutral salt spray test of the membrane layer can be 140h to 180h, or optionally 150h to 170h.

[0076] In some optional embodiments, the mechanical properties of the aluminum alloy sheet meet the following requirements: longitudinal elongation ≥ 10%, transverse elongation ≥ 8%, and compressive strength at break ≥ 550 MPa; optionally, the longitudinal elongation is 11% to 16%, the transverse elongation is 9% to 14%, and the compressive strength at break is 560 MPa to 290 MPa.

[0077] In some optional embodiments, the aluminum alloy sheet exhibits a neutral salt spray test result of ≥230h and an abrasion resistance Δm <0.02mg / cm². 2 Optionally, the neutral salt spray test is 250h to 290h; the abrasion resistance Δm is 0.005 to 0.018 mg / cm. 2 .

[0078] In some optional embodiments, the aluminum alloy sheet has a yield strength ≥120 MPa; tensile strength ≥280 MPa; hardness ≥250 HV; maximum coefficient of friction 0.5; and end strain <0.2%. Optionally, the aluminum alloy sheet has a yield strength of 130 MPa to 180 MPa; tensile strength of 290 MPa to 350 MPa; hardness of 260 HV to 320 HV; maximum coefficient of friction 0.4; and end strain ≤0.13%.

[0079] Brake pads can be made from various raw materials, slag removed by argon gas, die-cast according to the brake pad processing mold, and then prepared by micro-arc oxidation. After micro-arc oxidation, they can be powder-coated / painted.

[0080] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0081] Example 1

[0082] This application provides a method for preparing an aluminum alloy sheet. The aluminum alloy sheet includes an aluminum alloy substrate and a film layer. The aluminum alloy substrate comprises the following chemical components by mass percentage: Mg: 1.5% to 2.5%, Mn: 0.1% to 0.3%, Si3N4: 15% to 30%, with the balance being Al and unavoidable impurities, and the impurity content is ≤0.02%. The specific chemical composition is shown in Table 1.

[0083] This application provides a method for preparing aluminum alloy sheet or brake pad, including:

[0084] Step 100: Add metal raw materials according to the chemical composition of the aluminum alloy sheet and perform die casting; then form according to the component model of the brake pad to obtain the aluminum alloy matrix.

[0085] Specifically, the aluminum alloy matrix is ​​provided with metal raw materials and silicon nitride particles according to the chemical composition of the aluminum alloy matrix. The aluminum alloy matrix comprises the following chemical composition by mass percentage: Mg: 1.5% to 2.5%, Mn: 0.1% to 0.3%, Si3N4: 15% to 30%, with the balance being Al and unavoidable impurities, and the impurity content being ≤0.02%.

[0086] 100 parts by weight of metal raw material are melted at 750°C to obtain molten metal;

[0087] Silicon nitride particles and organometallic binders are mixed under heating conditions to obtain a framework material;

[0088] The molten metal is mixed with 25 parts by mass of the skeleton material at 100°C, and then cast and pressurized until solidification is applied to obtain an aluminum alloy matrix.

[0089] After step 100, pretreatment is performed: oil removal is carried out at room temperature using an aqueous solution of 3% sodium hydroxide and 5% sodium phosphate for 5 minutes. Then, activation is performed using an aqueous solution of 19% sodium fluoride at 46°C for 12 minutes.

[0090] Step 200 involves micro-arc oxidation of the aluminum alloy substrate to form a film, resulting in the aluminum alloy sheet, also known as a brake pad assembly. Specifically, the aluminum alloy substrate, connected with aluminum wire, is placed in an electrolytic cell. The equipment frequency is set to 420Hz, the pulse type to 20:8, the stirring and cooling systems are activated, the power supply is modulated from 0V to 220V, and the current is reduced to 2A / dm³. 2 The voltage is increased to 415±5V at a rate of 20V / min, and then controlled at around 25℃ while maintaining the above current density to reduce the voltage, thus obtaining a micro-arc oxidized aluminum alloy sheet, wherein a film layer is formed on the surface of the aluminum alloy substrate.

[0091] An anodizing solution was prepared by mixing 1.5 mol / L sodium silicate and silica sol at a volume ratio of 8:2. An aluminum alloy substrate was used as the anode, and a stainless steel plate as the cathode. The current density was controlled at 28 ± 0.3 mA / cm². 2 The micro-arc oxidation time is 30 minutes to form a film layer, thus obtaining the aluminum alloy sheet.

[0092] The obtained film is a silicon-containing ceramic oxide film with a thickness of 27 μm; the porosity of the film is ≤1%, the surface Vickers hardness of the film is ≥1200 HV, and the bonding strength between the aluminum alloy substrate and the film is 46 MPa.

[0093] Example 2-Example 3

[0094] The difference between this embodiment and Embodiment 1 is that the chemical composition of the aluminum alloy matrix is ​​different.

[0095] Example 4

[0096] The difference between this embodiment and Embodiment 1 is that the preparation method of the aluminum alloy sheet or brake pad is different. Specifically, the aluminum alloy sheet or brake pad is activated by an aqueous solution of 17% sodium fluoride at 45°C for 8 minutes.

[0097] Example 5

[0098] The difference between this embodiment and Embodiment 1 lies in the preparation method of the aluminum alloy sheet or brake pad. Specifically, during pretreatment, the degreasing was not performed using an aqueous solution of 4% sodium hydroxide and 4.8% sodium phosphate at room temperature. Instead, activation was directly performed using an aqueous solution of 20% sodium fluoride at 45°C for 10 minutes.

[0099] Example 6

[0100] The difference between this embodiment and Embodiment 1 is that the preparation method of the aluminum alloy sheet or brake pad is different. Specifically, in step 200, 0.75 mol / L sodium silicate and silica sol are prepared into an anodizing solution at a volume ratio of 8:2, and the micro-arc oxidation time is 45 min to form a film layer.

[0101] Example 7

[0102] The difference between this embodiment and Embodiment 1 is that the preparation method of the aluminum alloy sheet or brake pad is different. Specifically, in step 200, 1.5 mol / L sodium aluminate and silica sol are prepared into an anodizing solution at a volume ratio of 8:2.

[0103] Example 8

[0104] The difference between this embodiment and Embodiment 1 is that the preparation method of the aluminum alloy sheet or brake pad is different. Specifically, in step 200, 1.5 mol / L sodium phosphate and silica sol are prepared into an anodizing solution at a volume ratio of 8:2.

[0105] Example 9

[0106] The difference between this embodiment and Embodiment 1 is that the mass ratio of the metal raw material to silicon nitride particles in Embodiment 1 is 100:20.

[0107] Example 10

[0108] The difference between this embodiment and Embodiment 1 is that the mass ratio of the metal raw material to silicon nitride particles in Embodiment 1 is 100:50.

[0109] Example 11

[0110] The difference between this embodiment and Embodiment 1 is that the mass ratio of the metal raw material to silicon nitride particles in Embodiment 1 is 50:100.

[0111] Example 12

[0112] The difference between this embodiment and Embodiment 1 is that the silicon nitride particles are SiC.

[0113] Example 13

[0114] The difference between this embodiment and Embodiment 1 is that the preparation method of the aluminum alloy sheet or brake pad is different. Specifically, in step 200, 1.9 mol / L sodium aluminate and 6 g / L NaOH solution are prepared into an anodizing solution in a volume ratio of 8:2.

[0115] Comparative Example 1

[0116] This comparative example uses existing brake cast iron as the material for brake pads, including brake cast iron containing pearlite. The brake pads or plates produced in this comparative example have high density, heavy weight, and low strength, making them unsuitable as brake pads. Under repeated impact tests, the pressure points of the brake pads cracked, posing a high risk.

[0117] Comparative Example 2

[0118] The difference between this comparative example and Example 1 is that the preparation method of the aluminum alloy sheet or brake pad is different. After step 100, a pretreatment is performed, but step 200 is not performed, so that the surface of the aluminum alloy substrate has a discrete magnesium fluoride film layer.

[0119] Comparative Example 3

[0120] The difference between this comparative example and Example 1 is that the aluminum alloy substrate used in Example 1 is not pretreated or micro-arc oxidized. The surface of this aluminum alloy substrate has a natural oxide film containing magnesium.

[0121] Table 1. Chemical composition (wt.%) of examples and comparative examples

[0122]

[0123] The results of testing show the characteristics of the aluminum alloy matrix and film layer in the brake pad material, as shown in Table 2.

[0124] Table 2

[0125]

[0126] Research has shown that different pretreatments result in varying degrees of hardness and corrosion resistance in micro-arc oxidation films. Lower porosity leads to higher surface hardness, which is beneficial for aluminum alloy sheets to pass neutral salt spray tests. Better wear resistance and stability also result in longer service life. Experiments were conducted at different electrolyte concentrations, temperatures, and times to characterize the effects of electrolytes or oxidation solutions on the microstructure of the micro-arc oxidation film, thereby deriving the optimal process parameters.

[0127] The aluminum alloy sheets from the examples or comparative examples were subjected to a neutral salt spray test according to GB / T 10125 "Artificial Atmosphere Corrosion Test - Salt Spray Test". The test conditions were 5±1% NaCl, pH 6.5~7.2 (25℃), requiring continuous spraying for ≥230 hours. After the test, no substrate corrosion (such as pitting or peeling) was observed on the surface. Slight discoloration or coating blistering was permissible, indicating that the aluminum alloy sheet passed the neutral salt spray test. Specifically, the aluminum alloy sheets from Examples 1-13 passed the 230-hour neutral salt spray test, while those from Comparative Examples 1-3 did not.

[0128] Figure 2A schematic diagram of the overall structure of a braking assembly according to an embodiment of this application is shown. Figure 3 A half-sectional structural schematic diagram of a braking assembly according to an embodiment of this application is shown. As can be seen from the figure, the aluminum alloy sheet prepared in this embodiment can be used in the braking assembly, which includes a protective cover 1 and a brake disc 2, wherein the brake pads are located on one side of the brake disc 2 for braking.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing an aluminum alloy sheet, characterized in that, The method includes: Metal raw materials and silicon nitride particles are provided based on the chemical composition of the aluminum alloy matrix; 100 parts by weight of metal raw material are melted at 700 to 800°C to obtain molten metal; Silicon nitride particles and organometallic binder are mixed under heating conditions to obtain a framework material, wherein the mass ratio of silicon nitride particles to organometallic binder is 1:(0.2~0.3). The molten metal is mixed with 20 to 30 parts by weight of the skeleton material at a temperature of 80 to 120°C, and then cast and pressurized until solidification is applied to obtain an aluminum alloy matrix. The aluminum alloy matrix comprises the following chemical composition by weight percentage: Mg: 1.5%~2.5%, Mn: 0.1%~0.3%, Si3N4: 15%~30%, with the balance being Al and unavoidable impurities, and the impurity content being ≤0.02%. The aluminum alloy substrate is degreased at room temperature using an aqueous solution containing sodium hydroxide and sodium phosphate, and then activated at 40 to 65°C using an aqueous solution containing sodium fluoride to generate magnesium fluoride. The mass fraction of sodium fluoride in the aqueous solution containing sodium fluoride is 18% to 22%, and the activation time is 10 to 15 minutes. The aluminum alloy substrate is subjected to micro-arc oxidation to form a film layer, thereby obtaining the aluminum alloy sheet. The film layer is a silicon-containing ceramic oxide film with a thickness of 24 to 28 μm.

2. The method according to claim 1, characterized in that, The process of performing micro-arc oxidation on the aluminum alloy substrate to form a film layer and obtain the aluminum alloy sheet includes: in an oxidation solution, using the aluminum alloy substrate as the anode and the stainless steel plate as the cathode, with a current density of 28 ± 0.3 mA / cm². 2 The aluminum alloy sheet is obtained by applying an electric current for 35 to 55 minutes to form a film layer, wherein the oxidation solution includes sodium silicate solution and silica sol.

3. The method according to claim 1, characterized in that, The aqueous solution containing sodium hydroxide and sodium phosphate has a mass fraction of 3% to 5% for sodium hydroxide and sodium phosphate, respectively; the degreasing time is 3-8 minutes.

4. An aluminum alloy sheet, characterized in that, The aluminum alloy sheet is prepared by the method according to any one of claims 1 to 3, wherein the aluminum alloy sheet comprises an aluminum alloy substrate and a film layer disposed on the surface of the aluminum alloy substrate, and the aluminum alloy substrate comprises the following chemical composition by mass percentage: Mg: 1.5%~2.5%, Mn: 0.1%~0.3%, Si3N4: 15%~30%, with the balance being Al and unavoidable impurities, and the impurity content being ≤0.02%.

5. The aluminum alloy sheet according to claim 4, characterized in that, The surface Vickers hardness of the film layer is 1200HV to 1300HV, and the bonding strength between the aluminum alloy substrate and the film layer is 40 to 75MPa.

6. A brake pad, characterized in that, According to the processing model of the brake pad, it is made by the method described in any one of claims 1-3 or by the aluminum alloy sheet of claim 4 or 5.

Images