Die-casting forming method of graphene reinforced aluminum matrix composite brake disc

Abstract

The invention provides a die-casting forming method for a graphene reinforced aluminum matrix composite brake disc, and belongs to the field of brake disc preparation. The method comprises the following steps: carrying out surface modification treatment on graphene; mixing the modified graphene with the aluminum alloy melt; the brake disc is formed through a die-casting process; and the formed part is subjected to heat treatment to optimize the organization structure of the formed part. The brake disc prepared by the method has excellent thermophysical properties and mechanical properties, and is suitable for a high-performance automobile brake system.

Description

Technical Field

[0001] The present invention relates to the field of brake disc preparation, and particularly to a die-casting forming method for a graphene-reinforced aluminum matrix composite brake disc. Background Art

[0002] With the rapid development of the automotive industry, higher requirements are put forward for brake disc materials, especially in terms of high performance, light weight, and wear resistance. Although traditional cast iron brake discs have good braking performance and wear resistance, their high density leads to an increase in the vehicle's overall mass, which is not conducive to improving fuel economy and handling performance. Aluminum alloys, due to their low density, high specific strength, and good thermal conductivity, have become an ideal choice to replace cast iron materials. However, the wear resistance and high-temperature performance of pure aluminum and its alloys are relatively poor, which limits their application in high-load friction components such as brake discs.

[0003] To improve the performance of aluminum alloys, researchers have tried to introduce reinforcing phases into the aluminum matrix to prepare aluminum matrix composites. Graphene, as a new type of two-dimensional carbon material, has excellent mechanical properties, thermal conductivity, and electrical conductivity, and is considered an ideal reinforcing phase. Research shows that the addition of a small amount of graphene can significantly improve the strength, hardness, and wear resistance of aluminum matrix composites. For example, in the graphene-reinforced aluminum matrix composite prepared by powder metallurgy, when the mass fraction of graphene is 0.3%, its tensile strength and yield strength are increased by 62% and 50% respectively.

[0004] At present, the methods for preparing graphene-reinforced aluminum matrix composites mainly include powder metallurgy, melt stirring casting, chemical synthesis, etc. Powder metallurgy can achieve the uniform dispersion of graphene in the aluminum matrix, but there are problems such as complex process, high cost, and difficulty in preparing parts with complex shapes. The melt stirring casting process is relatively simple and suitable for large-scale production, but graphene is prone to agglomeration and thermal decomposition in the high-temperature melt, resulting in a decline in the performance of the composite material. In addition, graphene and aluminum are prone to interface reactions at high temperatures, generating brittle Al4C3 phases, which further affect the mechanical properties of the material.

[0005] To overcome the above problems, researchers have proposed various improvement methods, such as using surface modification technology to improve the interfacial bonding between graphene and the aluminum matrix, optimizing the stirring process parameters to improve the dispersion of graphene, and controlling the addition amount of graphene to avoid agglomeration. However, these methods still have certain limitations and are difficult to meet the requirements of high performance and industrial production simultaneously.

[0006] Therefore, developing a preparation method that can achieve the uniform dispersion of graphene in the aluminum matrix, good interfacial bonding, and is suitable for the forming of parts with complex shapes has become a hot and difficult point in current research. Summary of the Invention

[0007] In view of the problems involved in the above-mentioned background technology, the present invention provides a die-casting forming method for a graphene-reinforced aluminum matrix composite brake disc. By performing surface modification treatment on graphene and optimizing the melt preparation and die-casting process parameters, a brake disc product with excellent performance and suitable for industrial production is prepared.

[0008] A die-casting forming method for a graphene-reinforced aluminum matrix composite brake disc, comprising the following steps: a) Graphene surface modification treatment: Under nitrogen protection, 10-20 parts of 1-pyrenemethanethiol, 2-5 parts of 3-mercaptopropyltrimethoxysilane, 0.02-0.5 part of (ferrocenyl)hexanethiol and 300-500 parts of absolute ethanol are successively added to a reaction vessel, stirred evenly, the system is cooled to 0-5 °C, and 1-5 parts of metallic sodium are slowly added and stirred until completely dissolved to obtain a mixed sodium thiolate solution; Disperse 60-80 parts of graphene oxide in 500-1000 parts of deionized water, perform ultrasonic treatment for 30-60 minutes to form a uniform suspension, slowly drop the mixed sodium thiolate solution into the graphene suspension, stir and react at 50-60 °C for 9-12 hours. After the reaction ends, centrifuge and wash with water / ethanol until neutral, and vacuum dry at 60-80 °C for 9-12 hours to obtain modified graphene; b) Preparation of composite material melt: Heat 100-150 parts of aluminum alloy to 715-730 °C, add 0.5-1.5 parts of the modified graphene obtained in step a), and stir for 30-100 minutes under inert gas protection to form a graphene-reinforced aluminum matrix composite melt; c) Die-casting forming: Inject the composite material melt into a steel mold preheated to 180-220 °C, adopt a high-pressure die-casting process, and take out the casting after cooling; d) Heat treatment: Perform solution treatment on the formed brake disc at a temperature of 450-550 °C for 1-3 hours, and then perform artificial aging treatment at a temperature of 160-180 °C for 8-10 hours to optimize its organizational structure and performance.

[0009] In some embodiments, the specific composition of the aluminum alloy is: 9-11 parts of silicon (Si), 2-4 parts of copper (Cu), 0.5-1.5 parts of magnesium (Mg), and the balance is aluminum (Al).

[0010] In some embodiments, the inert gas is selected from nitrogen or argon.

[0011] In some embodiments, the high-pressure die-casting process parameters are: injection pressure is 80-120 MPa, and the holding pressure time is 10-20 seconds.

[0012] In some embodiments, the solution treatment is carried out in an air furnace with a heating rate of 8 - 12 °C / min, and water quenching treatment is carried out immediately after the holding ends.

[0013] In some embodiments, the artificial aging treatment is carried out in a constant temperature furnace with a heating rate of 4 - 6 °C / min.

[0014] Beneficial effects: 1) By using surface-modified graphene as the reinforcement phase, the tensile strength and hardness of the aluminum matrix composite are significantly improved. The surface modification treatment not only improves the dispersion of graphene but also enhances the interfacial bonding force between it and the aluminum matrix. The strong interfacial bonding helps the effective transfer of load between the matrix and the reinforcement phase, improving the overall mechanical properties of the composite.

[0015] 2) The addition of graphene significantly improves the wear resistance and thermal stability of the aluminum matrix composite. Graphene has excellent thermal conductivity and self-lubricating properties, which can effectively disperse frictional heat, reduce wear, and extend the service life of the brake disc.

[0016] 3) Dual mechanisms achieve nanoscale dispersion: π-π conjugation and steric hindrance: 1-pyrenemethanethiol is adsorbed on the surface of graphene through π-π interaction, and 3-mercaptopropyltrimethoxysilane forms a flexible spacer to prevent sheet stacking, making the graphene size evenly distributed.

[0017] 4) High-temperature stability and strengthening effect of chemical bonds: Si-O-C / Si-O-Al bond bridging: The Si-O-C bond formed by the silane coupling agent is converted into Si-O-Al bond in the high-temperature melt, enhancing the interfacial bonding strength. The strong interfacial bonding increases the thermal conductivity, inhibits the initiation of thermal cracks, and increases the service life of the brake disc. Specific embodiments

[0018] The technical solutions of the present invention will be described in detail below in conjunction with specific embodiments, so that those skilled in the art can better understand and implement the technical solutions of the present invention.

[0019] Embodiment 1: A die-casting forming method for a graphene-reinforced aluminum matrix composite brake disc, comprising the following steps: 1) Graphene surface modification treatment: Under nitrogen protection, 15 kg of 1-pyrenemethanethiol, 3 kg of 3-mercaptopropyltrimethoxysilane, 0.2 kg of (ferrocenyl) hexanethiol, and 400 kg of absolute ethanol are successively added to the reaction vessel, stirred evenly, the system is cooled to 3 °C, and 3 kg of metallic sodium is slowly added and stirred until completely dissolved to obtain a mixed sodium thiolate solution; Disperse 70 kg of graphene oxide in 800 kg of deionized water and ultrasonically treat for 45 minutes to form a homogeneous suspension. Slowly drop the mixed sodium mercaptide solution into the graphene suspension, stir and react at 55 °C for 10 hours. After the reaction, centrifuge and wash with water / ethanol until neutral, and then dry in vacuum at 70 °C for 10 hours to obtain modified graphene.

[0020] 2) Preparation of composite material melt: Heat 120 kg of aluminum alloy (containing 10 kg of silicon, 3 kg of copper, 1 kg of magnesium, and 106 kg of aluminum) to 720 °C, add 0.8 kg of modified graphene, and stir for 60 minutes under argon protection to form a graphene-reinforced aluminum matrix composite material melt.

[0021] 3) Die casting: Inject the composite material melt into a steel mold preheated to 200 °C, adopt the high-pressure die casting process, with an injection pressure of 100 MPa and a holding pressure time of 15 seconds, and take out the casting after cooling.

[0022] 4) Heat treatment: Perform solution treatment on the formed brake disc, heat it in an air furnace at a heating rate of 10 °C / min to 500 °C, hold for 2 hours, immediately perform water quenching treatment after the holding is completed, and then perform artificial aging treatment. Heat it in a constant temperature furnace at a heating rate of 5 °C / min to 170 °C and hold for 9 hours to optimize its organizational structure and performance.

[0023] Example 2: A die casting method for a graphene-reinforced aluminum matrix composite brake disc, comprising the following steps: 1) Surface modification treatment of graphene: Under nitrogen protection, sequentially add 10 kg of 1-pyrenemethanethiol, 2 kg of 3-mercaptopropyltrimethoxysilane, 0.05 kg of (ferrocenyl)hexanethiol, and 300 kg of absolute ethanol to the reaction vessel, stir evenly, cool the system to 0 °C, slowly add 1 kg of metallic sodium and stir until completely dissolved to prepare a mixed sodium mercaptide solution; Disperse 60 kg of graphene oxide in 500 kg of deionized water and ultrasonically treat for 30 minutes to form a homogeneous suspension. Slowly drop the mixed sodium mercaptide solution into the graphene suspension, stir and react at 50 °C for 12 hours. After the reaction, centrifuge and wash with water / ethanol until neutral, and then dry in vacuum at 60 °C for 12 hours to obtain modified graphene.

[0024] 2) Preparation of composite material melt: Heat 100 kg of aluminum alloy (containing 9 kg of silicon, 2 kg of copper, 0.5 kg of magnesium, and 88.5 kg of aluminum) to 715 °C, add 0.5 kg of modified graphene, and stir for 30 minutes under nitrogen protection to form a graphene-reinforced aluminum matrix composite material melt.

[0025] 3) Die casting: Inject the composite material melt into a steel mold preheated to 180 °C, and adopt the high-pressure die-casting process with an injection pressure of 80 MPa and a holding pressure time of 20 seconds. After cooling, take out the casting.

[0026] 4) Heat treatment: Conduct solution treatment on the formed brake disc. Heat it in an air furnace at a heating rate of 8 °C / min to 450 °C, hold for 3 hours, immediately perform water quenching treatment after the holding ends, and then perform artificial aging treatment. Heat it in a constant-temperature furnace at a heating rate of 4 °C / min to 160 °C and hold for 10 hours to optimize its organizational structure and performance.

[0027] Example 3: A die-casting forming method for a graphene-reinforced aluminum matrix composite brake disc, comprising the following steps: 1) Graphene surface modification treatment: Under nitrogen protection, sequentially add 20 kg of 1-pyrenemethanethiol, 5 kg of 3-mercaptopropyltrimethoxysilane, 0.5 kg of (ferrocenyl) hexanethiol and 500 kg of absolute ethanol to the reaction vessel, stir evenly, cool the system to 5 °C, slowly add 5 kg of metallic sodium and stir until completely dissolved to obtain a mixed sodium mercaptide solution; Disperse 80 kg of graphene oxide in 1000 kg of deionized water, and perform ultrasonic treatment for 60 minutes to form a uniform suspension. Slowly drop the mixed sodium mercaptide solution into the graphene suspension, stir and react at 60 °C for 9 hours. After the reaction ends, perform centrifugal separation and wash with water / ethanol until neutral, and then dry in vacuum at 80 °C for 9 hours to obtain modified graphene.

[0028] 2) Preparation of composite material melt: Heat 150 kg of aluminum alloy (containing 11 kg of silicon, 4 kg of copper, 1.5 kg of magnesium, and 133.5 kg of aluminum) to 730 °C, add 1.5 kg of modified graphene, and stir for 100 minutes under argon protection to form a graphene-reinforced aluminum matrix composite material melt.

[0029] 3) Die casting: Inject the composite material melt into a steel mold preheated to 220 °C, and adopt the high-pressure die-casting process with an injection pressure of 120 MPa and a holding pressure time of 10 seconds. After cooling, take out the casting.

[0030] 4) Heat treatment: The formed brake disc is solution-treated, heated in an air furnace at a heating rate of 12 °C / min to 550 °C, held for 1 hour, immediately water-quenched after the holding is completed, and then artificially aged. It is heated in a constant-temperature furnace at a heating rate of 6 °C / min to 180 °C and held for 8 hours to optimize its microstructure and properties.

[0031] Example 4: A die-casting forming method for a graphene-reinforced aluminum matrix composite brake disc, comprising the following steps: 1) Graphene surface modification treatment: Under nitrogen protection, 18 kg of 1-pyrenemethanethiol, 4 kg of 3-mercaptopropyltrimethoxysilane, 0.3 kg of (ferrocenyl)hexanethiol, and 450 kg of absolute ethanol are successively added to a reaction vessel, stirred evenly, the system is cooled to 4 °C, 4 kg of metallic sodium is slowly added and stirred until completely dissolved to obtain a mixed sodium mercaptide solution; 75 kg of graphene oxide is dispersed in 900 kg of deionized water, and ultrasonic treatment is carried out for 50 minutes to form a uniform suspension. The mixed sodium mercaptide solution is slowly dropped into the graphene suspension, and stirring reaction is carried out at 58 °C for 11 hours. After the reaction is completed, centrifugal separation is carried out and washed with water / ethanol until neutral, and vacuum drying is carried out at 75 °C for 11 hours to obtain modified graphene.

[0032] 2) Preparation of composite material melt: 130 kg of aluminum alloy (containing 9.5 kg of silicon, 3.5 kg of copper, 1.2 kg of magnesium, and 115.8 kg of aluminum) is heated to 725 °C, 1.2 kg of modified graphene is added, and stirring is carried out for 80 minutes under nitrogen protection to form a graphene-reinforced aluminum matrix composite material melt.

[0033] 3) Die-casting forming: The composite material melt is injected into a steel mold preheated to 210 °C, and a high-pressure die-casting process is adopted. The injection pressure is 110 MPa, and the holding pressure time is 18 seconds. After cooling, the casting is taken out.

[0034] 4) Heat treatment: The formed brake disc is solution-treated, heated in an air furnace at a heating rate of 11 °C / min to 520 °C, held for 1.5 hours, immediately water-quenched after the holding is completed, and then artificially aged. It is heated in a constant-temperature furnace at a heating rate of 5.5 °C / min to 175 °C and held for 8.5 hours to optimize its microstructure and properties.

[0035] Comparative Example 1: A die-casting forming method for a graphene-reinforced aluminum matrix composite brake disc, comprising the following steps: 1) Graphene surface modification treatment: Under nitrogen protection, 3 kg of 3-mercaptopropyltrimethoxysilane, 0.2 kg of (ferrocenyl)hexanethiol, and 400 kg of absolute ethanol were successively added to a reaction vessel, stirred evenly, the system was cooled to 3 °C, 3 kg of metallic sodium was slowly added and stirred until completely dissolved to obtain a mixed sodium mercaptide solution.

[0036] 70 kg of graphene oxide was dispersed in 800 kg of deionized water and ultrasonicated for 45 minutes to form a homogeneous suspension. The mixed sodium mercaptide solution was slowly dropped into the graphene suspension and stirred at 55 °C for 10 hours. After the reaction ended, it was centrifuged and washed with water / ethanol until neutral, and vacuum dried at 70 °C for 10 hours to obtain modified graphene.

[0037] 2) Preparation of composite material melt: 120 kg of aluminum alloy (containing 10 kg of silicon, 3 kg of copper, 1 kg of magnesium, and 106 kg of aluminum) was heated to 720 °C, 0.8 kg of modified graphene was added, and stirred for 60 minutes under argon protection to form a graphene-reinforced aluminum matrix composite material melt.

[0038] 3) Die casting: The composite material melt was injected into a steel mold preheated to 200 °C, and a high-pressure die casting process was used with an injection pressure of 100 MPa and a holding pressure time of 15 seconds. After cooling, the casting was taken out.

[0039] 4) Heat treatment: The formed brake disc was solution-treated, heated to 500 °C in an air furnace at a heating rate of 10 °C / min, held for 2 hours, immediately water-quenched after the holding ended, and then artificially aged, heated to 170 °C in a constant-temperature furnace at a heating rate of 5 °C / min, and held for 9 hours to optimize its microstructure and properties.

[0040] Comparative Example 2: A die casting method for a graphene-reinforced aluminum matrix composite material brake disc, comprising the following steps: 1) Surface modification treatment of graphene: Under nitrogen protection, 15 kg of 1-pyrenemethanethiol, 0.2 kg of (ferrocenyl)hexanethiol, and 400 kg of absolute ethanol were successively added to a reaction vessel and stirred evenly. The system was cooled to 3 °C, 3 kg of metallic sodium was slowly added and stirred until completely dissolved to obtain a mixed sodium mercaptide solution; 70 kg of graphene oxide was dispersed in 800 kg of deionized water and ultrasonicated for 45 minutes to form a homogeneous suspension. The mixed sodium mercaptide solution was slowly dropped into the graphene suspension and stirred at 55 °C for 10 hours. After the reaction ended, it was centrifuged and washed with water / ethanol until neutral, and vacuum dried at 70 °C for 10 hours to obtain modified graphene.

[0041] 2) Preparation of composite material melt: Heat 120 kg of aluminum alloy (containing 10 kg of silicon, 3 kg of copper, 1 kg of magnesium, and 106 kg of aluminum) to 720 °C, add 0.8 kg of modified graphene, and stir for 60 minutes under argon protection to form a graphene-reinforced aluminum matrix composite material melt.

[0042] 3) Die casting: Inject the composite material melt into a steel mold preheated to 200 °C, and use the high-pressure die casting process with an injection pressure of 100 MPa and a holding pressure time of 15 seconds. After cooling, take out the casting.

[0043] 4) Heat treatment: Conduct solution treatment on the formed brake disc. Heat it in an air furnace at a heating rate of 10 °C / min to 500 °C, hold for 2 hours, immediately perform water quenching after the holding is completed, and then perform artificial aging treatment. Heat it in a constant temperature furnace at a heating rate of 5 °C / min to 170 °C, hold for 9 hours to optimize its organizational structure and performance.

[0044] Testing methods: 1. Mechanical property testing: Tensile strength and yield strength: According to the GB / T 228.1-2010 standard, use an electronic universal material testing machine to conduct tensile testing with a loading rate of 1 mm / min.

[0045] 2. Hardness: According to the GB / T 231.1-2009 standard, use a Brinell hardness tester to conduct testing with a loading force of 500 N and a holding time of 15 seconds.

[0046] 3. Wear resistance testing: According to the GB / T 3960-2016 standard, use a pin-on-disc friction and wear testing machine with a load of 50 N, a sliding speed of 0.42 m / s, and a testing time of 30 minutes to calculate the wear rate and friction coefficient.

[0047] 4. Thermal conductivity testing: According to the GB / T 10297-2015 standard, use the laser flash method to measure the thermal diffusivity of the material, and calculate the thermal conductivity in combination with the density and specific heat capacity.

[0048] The test results of each example and comparative example obtained through the above testing methods are shown in Table 1 below: Table 1: Test results of each example and comparative example

[0049] In summary, the present invention verifies the effectiveness and advancement of the technical solution by surface modification of graphene and optimization of the die-casting process, and comparing the graphene-reinforced aluminum matrix composite brake discs prepared with the comparative examples in terms of mechanical properties, wear resistance, thermal conductivity, etc.

[0050] Although the present invention has been described above in conjunction with exemplary embodiments, those skilled in the art should clearly understand that various modifications and changes can be made to the exemplary embodiments of the present invention without departing from the spirit and scope defined by the claims.

Claims

1. Die casting forming method of graphene reinforced aluminum matrix composite brake disc, characterized in that It includes the following steps: a) Surface modification of graphene: Under nitrogen protection, 10 - 20 parts of 1-pyrenemethanethiol, 2 - 5 parts of 3-mercaptopropyltrimethoxysilane, 0.02 - 0.5 part of (ferrocenyl)hexanethiol and 300 - 500 parts of absolute ethanol are successively added into a reaction vessel, stirred evenly, the system is cooled to 0 - 5 °C, 1 - 5 parts of metallic sodium are slowly added and stirred until completely dissolved to obtain a mixed sodium mercaptide solution; 60 - 80 parts of graphene oxide are dispersed in 500 - 1000 parts of deionized water, ultrasonically treated for 30 - 60 minutes to form a uniform suspension, the mixed sodium mercaptide solution is slowly dropped into the graphene suspension, stirred and reacted at 50 - 60 °C for 9 - 12 hours, after the reaction ends, centrifuged and washed with water / ethanol until neutral, vacuum dried at 60 - 80 °C for 9 - 12 hours to obtain modified graphene; b) Preparation of composite material melt: 100 - 150 parts of aluminum alloy are heated to 715 - 730 °C, 0.5 - 1.5 parts of the modified graphene obtained in step a) are added, and stirred for 30 - 100 minutes under inert gas protection to form a graphene-reinforced aluminum matrix composite material melt; c) Die casting: The composite material melt is injected into a steel mold preheated to 180 - 220 °C, and the high-pressure die casting process is adopted, and the casting is taken out after cooling; d) Heat treatment: The formed brake disc is subjected to solution treatment at a temperature of 450 - 550 °C for 1 - 3 hours, and then artificial aging treatment at a temperature of 160 - 180 °C for 8 - 10 hours.

2. The die-casting forming method of the graphene-reinforced aluminum matrix composite brake disc according to claim 1, characterized in that: The specific composition of the aluminum alloy is: 9 - 11 parts of silicon, 2 - 4 parts of copper, 0.5 - 1.5 parts of magnesium, and the balance is aluminum.

3. The die-casting forming method of the graphene-reinforced aluminum matrix composite brake disc according to claim 1, characterized in that: The inert gas is selected from nitrogen or argon.

4. The die-casting forming method of the graphene-reinforced aluminum matrix composite brake disc according to claim 1, characterized in that: The high-pressure die casting process parameters: the injection pressure is 80 - 120 MPa, and the holding pressure time is 10 - 20 seconds.

5. The die-casting forming method of the graphene-reinforced aluminum matrix composite brake disc according to claim 1, characterized in that: The solution treatment is carried out in an air furnace, and the heating rate is 8 - 12 °C / min, and water quenching treatment is immediately carried out after the holding ends.

6. The die-casting forming method of the graphene-reinforced aluminum matrix composite brake disc according to claim 1, characterized in that: The artificial aging treatment is carried out in a constant temperature furnace, and the heating rate is 4 - 6 °C / min.

Images