Preparation method of automobile brake disc

Abstract

According to the preparation method of the automobile brake disc, through multi-dimensional cooperation of'component design-shrinkage rate difference-sintering process', interface combination and shape control are achieved through the self-extrusion effect during disc body sintering, the complex process that a traditional brake disc depends on machining or shaping is avoided, 'near-net forming 'is truly achieved, and the production efficiency is improved. After sintering, the brake disc with the dimensional precision, the interface strength and the functional performance meeting the requirements can be directly obtained, the production efficiency is remarkably improved, and the manufacturing cost of the lightweight brake disc is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of powder metallurgy, and particularly to a preparation method of an automotive brake disc. Background Art

[0002] Lightweighting is one of the most effective means to achieve energy conservation and consumption reduction in automobiles and other transportation vehicles. Using high-performance light metals to replace steel materials in key moving parts such as the engines and brake discs of transportation equipment can not only reduce the weight of the whole vehicle, lower the momentum of high-speed moving parts of transportation equipment, but also significantly improve the power performance of transportation equipment while reducing energy consumption.

[0003] Silicon carbide particle-reinforced aluminum matrix composites have low density, high specific strength and specific stiffness, high thermal conductivity, and excellent anti-wear and corrosion resistance, and have broad application prospects in the field of lightweight structural components. Using silicon carbide particle-reinforced aluminum matrix composites to replace traditional brake disc materials has also become the main research direction for lightweighting transportation vehicles at present.

[0004] Most of the existing lightweight automotive brake discs achieve lightweighting by using a disc cap made of aluminum alloy, while the disc body still uses cast iron material with good wear resistance. This requires the disc body and the disc cap to be able to move radially relative to each other to minimize the thermal tension generated in the disc body during each braking process. The radial freedom is generated by a mating gap, which is generated by machining and inserted connecting elements, resulting in high manufacturing costs. Moreover, the inserted connecting elements bear a large moment during the braking process and are prone to deformation and fracture, affecting driving safety.

[0005] CN111442039A discloses a lightweight and wear-resistant aluminum-based powder metallurgy composite automotive brake disc, whose disc body is composed of an aluminum-based structural material, and the friction surface is composed of a wear-resistant aluminum-based composite material. By using lightweight materials with different materials for the friction surface and the disc body, the weight is further reduced while meeting the friction performance and reducing energy consumption. However, for this automotive brake disc, the disc body is actually composed of a disc cap and a support structure extending radially outward from the disc cap to between the two friction surfaces, and the connection strength between the disc body and the friction surface is improved by increasing the contact area between the friction surface and the disc body. The existence of the support structure undoubtedly increases the manufacturing cost and the complexity of the preparation process.

[0006] CN118786294A discloses a lightweight automotive brake disc and its preparation method. By selecting two aluminum matrix composites with matching sintering shrinkage rates during the powder metallurgy preparation process and also matching thermal expansion coefficients under the service conditions of the automotive brake disc, the disc cap and the disc body are respectively prepared, so that the disc cap and the disc body are metallurgically connected only in the circumferential direction, thereby obtaining a relatively high interfacial bonding strength, while meeting the braking performance requirements such as friction wear and fatigue resistance required by traditional automotive brake discs during the friction braking process. However, this method still requires hot pressing and shaping after sintering, with complex processes and high costs. Summary of the Invention

[0007] Based on this, it is necessary to provide a preparation method for an automotive brake disc with simple processes and low costs.

[0008] A preparation method for an automotive brake disc, the automotive brake disc includes a disc cap and a disc body, the disc cap and the disc body are metallurgically connected in the circumferential direction, and the preparation method for the automotive brake disc includes the following steps:

[0009] Provide powder for the disc cap. By mass percentage, the powder for the disc cap includes: 4% - 6.5% of copper powder, 1% - 1.5% of magnesium powder, 0.3% - 0.7% of silicon powder, 17% - 28% of silicon carbide particles, and 63.3% - 77.7% of aluminum powder;

[0010] Provide powder for the disc body. By mass percentage, the powder for the disc body includes: 33% - 49% of silicon carbide particles and the balance of aluminum - copper - magnesium alloy; the total mass content of copper and magnesium in the aluminum - copper - magnesium alloy is 2.8% - 6.7%;

[0011] Provide a forming mold, the forming mold includes a disc cap cavity adapted to the disc cap and a disc body cavity adapted to the disc body;

[0012] After mixing the powder for the disc cap evenly, fill it into the disc cap cavity, after mixing the powder for the disc body evenly, fill it into the disc body cavity, close the mold and press, then demold to obtain a green body;

[0013] Subject the green body to temperature - rising sintering, holding sintering, and temperature - dropping sintering in sequence to obtain the automotive brake disc.

[0014] In one embodiment, during the temperature - rising sintering process, the green body is heated at a heating rate of 12°C / min - 21°C / min to 580°C - 650°C.

[0015] In one embodiment, during the holding sintering process, the temperature of the green body is 580°C - 650°C, and the holding sintering time is 30 - 60 minutes.

[0016] In one embodiment, during the cooling and sintering process, the green body is cooled to 200°C - 300°C at a rate of 4.5°C / min - 10°C / min.

[0017] In one embodiment, the process of die closing and pressing is specifically as follows: first, overall pre-pressing is carried out, and then zone pressing is carried out. The zone pressing includes pressing in the disc cap area and pressing in the disc body area.

[0018] In one embodiment, the pressure of the overall pre-pressing is 15 MPa - 45 MPa.

[0019] In one embodiment, the pressure of pressing in the disc cap area is 200 MPa - 250 MPa; the pressing in the disc body area is carried out in a manner of displacement control and pressure protection, and the pressure of the pressure protection is 150 MPa - 180 MPa.

[0020] In one embodiment, the D of the silicon carbide particles in the disc cap raw material powder 50 is 15 μm - 40 μm, and the aluminum powder is irregular aluminum powder.

[0021] In one embodiment, the D of the silicon carbide particles in the disc body raw material powder 50 is 20 μm - 50 μm, and the D of the aluminum-copper-magnesium alloy 50 is 25 μm - 40 μm.

[0022] The above method for preparing an automotive brake disc realizes interface bonding and shape control by means of multi-dimensional coordination of "composition design - shrinkage rate difference - sintering process", utilizes the self-extrusion effect during disc body sintering, avoids the complex processes of traditional brake discs relying on machining or shaping, truly realizes "near-net shaping", and can obtain a brake disc with size accuracy, interface strength and functional performance all meeting the requirements after sintering, significantly improving production efficiency and reducing the manufacturing cost of lightweight brake discs. Detailed Embodiments

[0023] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below, and preferred embodiments of the present invention are given. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0025] A preparation method of an automotive brake disc according to an embodiment, the automotive brake disc includes a disc cap and a disc body, and the disc cap and the disc body are metallurgically bonded in the circumferential direction. The preparation method includes the following steps S110 to S150:

[0026] S110. Provide the disc cap raw material powder.

[0027] The disc cap raw material powder includes: copper powder with a mass content of 4% to 6.5%, magnesium powder with a mass content of 1% to 1.5%, silicon powder with a mass content of 0.3% to 0.7%, silicon carbide particles with a mass content of 17% to 28%, and aluminum powder with a mass content of 63.3% to 77.7% (calculated based on the total mass content of the disc cap raw material powder being 100%).

[0028] The disc cap raw material powder with the above composition will generate more liquid phase under the sintering conditions of this application, so that the material has good processability. After sintering, the disc cap has high density and a complete shape without cracks. At the same time, the addition of silicon powder also makes Mg2Si phase generated during the sintering process for strengthening, thereby ensuring the structural strength of the disc cap.

[0029] Further, the D of the silicon carbide particles in the above disc cap raw material powder 50 is 15um to 40um. The aluminum powder is irregular aluminum powder.

[0030] It can be understood that if the particle size of the silicon carbide particles in the disc cap raw material powder is too large, the compression performance is poor, and problems such as inability to form after pressing may occur; if the particle size is too small, the fluidity of the raw material powder is poor, resulting in uneven density of the green body after forming and easy deformation of the green body after sintering.

[0031] Select silicon carbide particles with D 50 of 15um to 40um, which can be evenly dispersed in matrix powders such as aluminum powder, copper powder, and magnesium powder, avoiding uneven dispersion and interfacial stress concentration caused by too large particles, and can provide effective support through moderate particle size, inhibiting excessive plastic deformation of the matrix powder during sintering, thereby enhancing the interface load transfer efficiency.

[0032] By adding irregular aluminum powder, the compression performance of the disc cap raw material powder can be improved. The particle morphology of the irregular aluminum powder has edges and corners and an asymmetric structure. During the pressing process, the locking effect between particles can be enhanced through the mechanical meshing effect. Compared with spherical aluminum powder, its surface roughness is high and the contact area between particles is larger, which can effectively fill the gaps between silicon carbide particles and metal powders, reduce the porosity and increase the green body density.

[0033] Meanwhile, irregular particles are prone to plastic deformation under pressure, forming a denser particle packing structure, enabling the powder to obtain a higher initial density at a lower compaction pressure, providing a better microstructure contact for the uniform distribution of the liquid phase and interface bonding during the subsequent sintering process, and thus improving the forming quality and structural strength of the disc cap blank.

[0034] S120. Provide the powder of the disc body raw material.

[0035] The powder of the disc body raw material includes 33% - 49% by mass of silicon carbide particles and the balance of aluminum-copper-magnesium alloy (calculated based on the total mass content of the powder of the disc body raw material being 100%). Among them, the total mass content of copper and magnesium elements in the aluminum-copper-magnesium alloy is 2.8% - 6.7% (calculated based on the total mass content of the aluminum-copper-magnesium alloy being 100%).

[0036] For the powder of the disc body raw material with the above composition, the copper and magnesium elements are added in the form of the aluminum-copper-magnesium alloy. Under the sintering conditions of this application, its sintering shrinkage rate is significantly higher than that of the powder of the disc cap raw material, so that the disc body shrinks inward and extrudes the disc cap, thereby improving the interfacial bonding force between the disc body and the disc cap.

[0037] The above-mentioned powder of the disc body raw material has good wear resistance and heat resistance after sintering, and can meet the braking performance requirements such as friction wear and fatigue resistance required by traditional automotive brake discs during the friction braking process.

[0038] Further, the D 50 of the silicon carbide particles in the powder of the disc body raw material is 20um - 50um. The D 50 of the aluminum-copper-magnesium alloy is 25um - 40um.

[0039] Selecting silicon carbide particles with D 50 of 20um - 50um as the main wear-resistant phase can form a stable hard support framework during the braking friction process, effectively resisting abrasive wear and adhesive wear on the friction surface, and meeting the high wear-resistant performance requirements of the disc body.

[0040] Selecting an aluminum-copper-magnesium alloy with D 50 of 25um - 40um, if it is too fine, the fluidity of the powder decreases, which may cause sintering agglomeration and the problem of disc body deformation after cooling; if it is too coarse, it will affect the forming compression performance and may lead to insufficient interfacial bonding.

[0041] S130. Provide a forming mold.

[0042] The forming mold includes a disc cap cavity adapted to the above-mentioned disc cap and a disc body cavity adapted to the above-mentioned disc body.

[0043] S140. After uniformly mixing the above-mentioned disc cap raw material powder, fill it into the disc cap cavity. After uniformly mixing the above-mentioned disc body raw material powder, fill it into the disc body cavity. Demold after mold clamping and pressing to obtain a green body.

[0044] Among them, the process of mold clamping and pressing is specifically as follows: first, perform overall pre-pressing and then perform zone pressing. The zone pressing includes disc cap zone pressing and disc body zone pressing.

[0045] Furthermore, the pressure of the overall pre-pressing is 15 MPa to 45 MPa. The pressure of the disc cap zone pressing is 200 MPa to 250 MPa. The disc body zone pressing is carried out in a manner of displacement control and pressure protection, and the pressure of the pressure protection is 150 MPa to 180 MPa.

[0046] Adopt overall pre-pressing to ensure that the disc cap raw material powder and the disc body raw material powder are fully filled into their respective mold cavities. Then, adopt the method of zone pressing to make the density of the disc body lower than that of the disc cap, and finally promote the sintering shrinkage rate of the disc body to be higher than that of the disc cap during the sintering process.

[0047] S150. Subject the above-mentioned green body to temperature rising sintering, heat preservation sintering and temperature decreasing sintering in sequence to obtain an automotive brake disc.

[0048] Among them, during the temperature rising sintering process, the green body is heated to 580 °C to 650 °C at a heating rate of 12 °C / min to 21 °C / min.

[0049] During the heat preservation sintering process, the temperature of the green body is 580 °C to 650 °C, and the heat preservation sintering time is 30 to 60 minutes.

[0050] During the temperature decreasing sintering process, the green body is cooled to 200 °C to 300 °C at a rate of 4.5 °C / min to 10 °C / min.

[0051] The core of the above-mentioned method for preparing an automotive brake disc lies in controlling the addition form of copper and magnesium elements (elemental powder VS. alloy powder), differentially regulating the sintering behaviors of the disc cap and the disc body (liquid phase generation amount and sintering shrinkage rate), and utilizing the interface extrusion effect generated by the difference in the sintering shrinkage rates of the disc cap and the disc body during the sintering process, thereby improving the interface bonding force.

[0052] Specifically, copper and magnesium in the disk cap raw material powder are added in the form of elemental powder. During the heating and sintering process, after being heated to the eutectic temperature, they gradually form Al-Cu and Al-Mg solid solutions and low-melting-point eutectic phases through diffusion alloying. Since the elemental powder needs to undergo a complete diffusion alloying process, the liquid phase generation temperature is relatively broad and the generated amount continuously increases with the increase in temperature. The appearance of the liquid phase promotes particle rearrangement and interstitial filling, effectively suppressing the early shrinkage of the disk cap green body. During the isothermal sintering process, a large amount of liquid phase at high temperature (including eutectic liquid phase and local liquid phase around the Mg2Si strengthening phase formed by the reaction of silicon powder and magnesium powder) wraps the aluminum powder and silicon carbide particles, and realizes efficient mass transfer and densification between particles through viscous flow. The viscous resistance of the liquid phase significantly slows down the sintering shrinkage rate, making the disk cap green body mainly undergo "liquid-phase-dominated densification" during the isothermal stage, with a relatively low shrinkage rate. During the cooling and sintering process, the liquid phase gradually solidifies, forming a composite structure of Al-Cu-Mg matrix alloy and Mg2Si strengthening phase. The silicon carbide particles are evenly distributed in this composite structure to form a rigid skeleton. Due to the large amount of liquid phase in the early stage and the inhibited shrinkage, the disk cap material shows low sintering shrinkage characteristics during cooling, forming a relatively stable core structure.

[0053] However, copper and magnesium in the disk body raw material powder are added in the form of aluminum-copper-magnesium alloy. During the heating and sintering process, only a small amount of local eutectic liquid phase is generated (mainly from the low-melting-point phase inside the alloy powder), and the generated amount of the liquid phase is significantly less than that of the disk cap material. The combination between particles is mainly through solid-phase diffusion, and the shrinkage driving force is relatively strong. During the isothermal sintering process, it shrinks through rigid contact and dislocation slip between particles, and the sintering shrinkage rate is higher than that of the disk cap material. Although silicon carbide particles with a content of 33% - 49% will inhibit the matrix shrinkage, due to the strong shrinkage driving force of the alloy powder, the overall still shows a relatively high radial shrinkage trend. During the cooling and sintering process, as the temperature decreases, due to the solid-phase sintering characteristics of the alloy powder in the disk body material, the cooling shrinkage rate is faster than that of the disk cap material, forming a strong radial inward shrinkage trend; and at this time, the disk cap has formed a rigid core, and the shrinkage of the disk body generates a radial extrusion stress on the disk cap, promoting the particles at the interface to tightly fit, and at the same time, a small amount of unfrozen liquid phase fills the interface pores under pressure, strengthening the metallurgical bond.

[0054] In summary, in the late stage of isothermal sintering to the initial stage of cooling and sintering (i.e., the temperature range where the liquid phase has not completely solidified), due to the dominant mechanism of solid-phase sintering of the alloy powder in the disk body material, the sintering shrinkage rate is significantly higher than that of the disk cap material. This shrinkage rate difference causes the disk body to continuously exert a radial extrusion on the disk cap, forming mechanical meshing and metallurgical bond at the interface, and at the same time, residual interface compressive stress remains after cooling, ultimately achieving an improvement in the circumferential metallurgical bond strength.

[0055] The following are specific examples.

[0056] Example 1

[0057] (1) Provide the powder of the disc cap raw material, which includes 4 wt.% of copper powder, 1 wt.% of magnesium powder, 0.3 wt.% of silicon powder, 17 wt.% of silicon carbide particles (with a particle size of 15 μm), and 77.7 wt.% of irregular aluminum powder.

[0058] (2) Provide the powder of the disc body raw material, which includes 33% of silicon carbide particles (with a particle size of 20 μm) and 67% of aluminum-copper-magnesium alloy (with a particle size of 25 μm), and the total mass content of copper and magnesium in the aluminum-copper-magnesium alloy is 2.8%.

[0059] (3) Provide a forming die, which includes a disc cap cavity adapted to the brake disc cap to be prepared and a disc body cavity adapted to the brake disc body to be prepared.

[0060] (4) After mixing the above-mentioned powder of the disc cap raw material evenly, fill it into the disc cap cavity. After mixing the above-mentioned powder of the disc body raw material evenly, fill it into the disc body cavity. After closing the die and pressing, demold to obtain a green body.

[0061] (5) Heat the above-mentioned green body to 580 °C at a heating rate of 12 °C / min, then keep it at 580 °C for 30 minutes, and then cool it to 200 °C at a rate of 4.5 °C / min to obtain an automotive brake disc.

[0062] After testing, the appearance of the automotive brake disc prepared in Example 1 is complete and defect-free. The difference between the external dimension and the drawing dimension is 1.5 mm - 2.0 mm (for the reserved machining allowance), and the interior is dense without pores and fine cracks, and the particle distribution is uniform. The interfacial bonding strength between the disc cap and the disc body is 145 MPa - 165 MPa. Conduct a bench test on this lightweight automotive brake disc, and complete and pass the two bench tests of T / CAAMTB 09-2018 high load and Jaso C419-2006 torque failure, indicating that the structural strength and friction and wear performance of this brake disc meet the requirements of the brake disc.

[0063] Example 2

[0064] (1) Provide the powder of the disc cap raw material, which includes 6.5 wt.% of copper powder, 1.5 wt.% of magnesium powder, 0.7 wt.% of silicon powder, 28 wt.% of silicon carbide particles (with a particle size of 40 μm), and 63.3 wt.% of irregular aluminum powder.

[0065] (2) Provide the powder of the disc body raw material, which includes 49% of silicon carbide particles (with a particle size of 50 μm) and 51% of aluminum-copper-magnesium alloy (with a particle size of 40 μm), and the total mass content of copper and magnesium in the aluminum-copper-magnesium alloy is 6.7%.

[0066] (3) Provide a forming die, which includes a cap cavity adapted to the brake disc cap to be prepared and a body cavity adapted to the brake disc body to be prepared.

[0067] (4) After uniformly mixing the above-mentioned cap raw material powder, fill it into the cap cavity. After uniformly mixing the above-mentioned body raw material powder, fill it into the body cavity. After closing the die and pressing, demold to obtain a green body.

[0068] (5) Heat the above-mentioned green body to 650 °C at a heating rate of 21 °C / min, then keep it at 650 °C for 60 minutes, and then cool it to 300 °C at a rate of 10 °C / min to obtain an automotive brake disc.

[0069] After testing, the appearance of the automotive brake disc prepared in Example 2 is complete and defect-free. The difference between the external dimension and the drawing dimension is 1.5 mm to 2 mm (for the reserved machining allowance). Moreover, it is dense inside without pores and small cracks, and the particle distribution is uniform. The interfacial bonding strength between the cap and the body is 140 MPa to 156 MPa. Conduct a bench test on this lightweight automotive brake disc, and complete and pass the two bench tests of T / CAAMTB 09-2018 high load and Jaso C419-2006 torque failure, indicating that the structural strength and friction and wear performance of this brake disc meet the requirements of the brake disc.

[0070] Example 3

[0071] (1) Provide cap raw material powder, which includes 5 wt.% copper powder, 1.2 wt.% magnesium powder, 0.5 wt.% silicon powder, 25 wt.% silicon carbide particles (particle size of 25 μm), and 68.3 wt.% irregular aluminum powder.

[0072] (2) Provide body raw material powder, which includes 45 wt.% silicon carbide particles (particle size of 35 μm) and 55% aluminum-copper-magnesium alloy (particle size of 30 μm). The total mass content of copper and magnesium in this aluminum-copper-magnesium alloy is 5%.

[0073] (3) Provide a forming die, which includes a cap cavity adapted to the brake disc cap to be prepared and a body cavity adapted to the brake disc body to be prepared.

[0074] (4) After uniformly mixing the above-mentioned cap raw material powder, fill it into the cap cavity. After uniformly mixing the above-mentioned body raw material powder, fill it into the body cavity. After closing the die and pressing, demold to obtain a green body.

[0075] (5) Heat the above-mentioned green body to 620 °C at a heating rate of 18 °C / min, then keep it at 620 °C for 45 minutes, and then cool it to 200 °C at a rate of 8 °C / min to obtain an automotive brake disc.

[0076] Upon inspection, the appearance of the automotive brake disc prepared in Example 3 is complete and defect-free. The difference between the external dimensions and the drawing dimensions is 1.5 mm to 2.0 mm (the reserved machining allowance). Moreover, its interior is dense without pores and fine cracks, and the particle distribution is uniform. The interfacial bonding strength between the disc cap and the disc body is 145 MPa to 175 MPa. The lightweight automotive brake disc was subjected to bench tests and completed and passed the two bench tests of T / CAAMTB 09-2018 high load and Jaso C419-2006 torque failure, indicating that the structural strength and friction and wear performance of the brake disc meet the requirements of the brake disc.

[0077] Comparative Example 1

[0078] Comparative Example 1 is basically the same as Example 3, except that in Comparative Example 1, the green body was heated to 560 °C at a heating rate of 18 °C / min, then held at 560 °C for 45 minutes, and then cooled to 200 °C at a rate of 8 °C / min.

[0079] As a result, the sintering shrinkage rate of the brake disc did not meet the material requirements, the interfacial strength was lower than 100 MPa, and the material strength of the disc cap part was lower than 120 MPa. During the bench test, due to the increase in the temperature of the brake disc, cracks appeared at the position of the disc cap mounting hole, resulting in the failure of the test.

[0080] Comparative Example 2

[0081] Comparative Example 2 is basically the same as Example 3, except that in Comparative Example 2, the green body was heated to 620 °C at a heating rate of 30 °C / min, then held at 620 °C for 45 minutes, and then cooled to 200 °C at a rate of 8 °C / min to obtain an automotive brake disc.

[0082] At a high heating rate, during the heating process of the green body of the brake disc, due to the difference in sintering shrinkage between the inner and outer materials, there are maintenance cracks at the interface position, and the cracks extend into the interior of the brake disc and cannot be removed by machining.

[0083] The above-described embodiments merely represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims

1. A preparation method of an automotive brake disc, the automotive brake disc comprising a disc cap and a disc body, the disc cap and the disc body being metallurgically bonded in the circumferential direction, characterized in that, The preparation method of the automotive brake disc comprises the following steps: Provide the powder of the disc cap raw material. By mass percentage, the powder of the disc cap raw material comprises: 4% - 6.5% of copper powder, 1% - 1.5% of magnesium powder, 0.3% - 0.7% of silicon powder, 17% - 28% of silicon carbide particles, and 63.3% - 77.7% of aluminum powder; Provide the powder of the disc body raw material. By mass percentage, the powder of the disc body raw material comprises: 33% - 49% of silicon carbide particles and 51% - 67% of aluminum copper magnesium alloy; the total mass content of copper and magnesium in the aluminum copper magnesium alloy is 2.8% - 6.7%; Provide a forming die, which comprises a disc cap cavity adapted to the disc cap and a disc body cavity adapted to the disc body; Mix the powder of the disc cap raw material evenly and fill it into the disc cap cavity, mix the powder of the disc body raw material evenly and fill it into the disc body cavity, close the die and press, then demould to obtain a green body; Sinter the green body by heating, heat preservation sintering and cooling sintering in sequence to obtain the automotive brake disc; 2. The preparation method of the automotive brake disc according to claim 1, characterized in that, During the heating sintering process, the green body is heated to 580°C - 650°C at a heating rate of 12°C / min - 21°C / min; 3. The preparation method of the automotive brake disc according to claim 1, characterized in that, During the heat preservation sintering process, the temperature of the green body is 580°C - 650°C, and the heat preservation sintering time is 30 - 60 minutes; 4. The preparation method of the automotive brake disc according to claim 1, wherein, During the cooling sintering process, the green body is cooled to 200°C - 300°C at a rate of 4.5°C / min - 10°C / min; 5. The preparation method of the automotive brake disc according to claim 1, characterized in that, The process of closing the die and pressing is specifically as follows: first, perform overall pre-pressing and then perform zone pressing, and the zone pressing includes disc cap zone pressing and disc body zone pressing; 6. The preparation method of the automotive brake disc according to claim 5, characterized in that The pressure of the overall pre-pressing is 15MPa - 45MPa; 7. The preparation method of the automotive brake disc according to claim 5, wherein, The pressure of the disc cap zone pressing is 200MPa - 250MPa; the disc body zone pressing is carried out in a manner of displacement control and pressure protection, and the pressure of the pressure protection is 150MPa - 180MPa.

8. The preparation method of the automotive brake disc according to claim 1, wherein, The D of the silicon carbide particles in the raw material powder of the disc cap 50 is 15 um to 40 um, and the aluminum powder is irregular aluminum powder.

9. The preparation method of the automotive brake disc according to claim 1, wherein, The D of the silicon carbide particles in the raw material powder of the disk body 50 is 20 μm to 50 μm, and the D of the aluminum-copper-magnesium alloy 50 is 25 μm to 40 μm.