Heat-resistant high-strength passenger car aluminum matrix composite brake disc and preparation method thereof

Abstract

The invention discloses a heat-resistant high-strength passenger car aluminum matrix composite brake disc and a preparation method thereof. The brake disc comprises an aluminum alloy base body layer and a composite material friction layer which are welded in a friction mode. The composite material friction layer comprises an Al-Fe-V-Si aluminum alloy and reinforced particles; the reinforced particles are at least one of SiC, BN and TiC. The preparation process of the brake disc comprises the steps that the composite material friction layer is placed on the base body layer, welding is conducted through friction stir welding after the position is adjusted, and the brake disc is obtained. According to the brake disc, the aluminum alloy base body layer and the composite material friction layer are combined through friction welding, it is guaranteed that the whole brake disc has good toughness, meanwhile, the abrasion resistance and the heat resistance can be improved, therefore, the overall mechanical property of the aluminum-based composite material brake disc is better, and the use reliability of the brake disc is improved.

Description

Technical Field

[0001] The invention relates to an aluminum-based composite brake disc, in particular to a heat-resistant and high-strength passenger car aluminum-based composite brake disc and a preparation method thereof, belonging to the technical field of brake discs. Background Art

[0002] The transportation industry is developing rapidly, but energy shortage is a severe challenge it faces. How to save energy is one of its primary development goals. For automobiles, there are two main measures: one is to vigorously develop new energy vehicles, and the other is to reduce the weight of the vehicle itself. If lightweight aluminum-based composite materials are used to replace the currently widely used cast iron and other materials brake discs, it can achieve a significant weight reduction effect, and the prospects are very attractive. In addition, aluminum-based composite brake discs have the advantages of light weight, good friction and wear performance, good thermal conductivity and good thermal fatigue resistance, and have a strong competitive advantage in the application of automotive brake discs.

[0003] At present, the research on composite materials for brake discs mainly uses stirring casting to prepare integrated composite brake discs. Due to the large surface tension and poor surface wettability of ceramic particles, composite materials prepared by stirring casting have casting defects such as pores, shrinkage and uneven distribution of reinforcement phase, which will have an adverse effect on the mechanical properties of the material. In addition, the toughness of aluminum-based composite materials is insufficient. During the braking process, the broken reinforcement phase particles will cause the initiation and expansion of cracks, which will further accelerate the fracture and failure of the brake disc. Summary of the invention

[0004] In view of the problems existing in the prior art, the first object of the present invention is to provide a heat-resistant and high-strength aluminum-based composite brake disc for passenger cars. The brake disc, based on the synergistic effect between the base layer and the friction layer, ensures the specific strength and specific stiffness of the brake disc while greatly improving the heat resistance of the brake disc, especially its mechanical properties under high temperature conditions above 300°C; the friction layer of the brake disc adopts Al-Fe-V-Si aluminum alloy as the base, and utilizes the finely dispersed Al 12 (Fe,V)3Si heat-resistant phase to achieve high temperature strengthening, combined with ceramic reinforcement particles to further improve the material's strength, modulus, wear resistance, fatigue resistance and thermal expansion The second object of the present invention is to provide a method for preparing a heat-resistant and high-strength passenger car aluminum-based composite brake disc. The method uses a stir friction welding process to combine the base layer and the friction layer together. The process generates heat through the friction between the high-speed rotating stirring head and the workpiece, so that the welded material is locally softened. When the stirring head moves along the welding interface, the plasticized material flows from the front end to the rear end of the stirring head under the action of the rotating friction force of the stirring head, and forms a dense solid phase weld under the extrusion of the stirring head. In addition, during the stir friction processing, the original defects near the contact surface of the base layer and the friction layer will be destroyed, thereby obtaining a finer and more uniform grain structure.

[0005] In order to achieve the above technical objectives, the present invention provides a heat-resistant and high-strength passenger car aluminum-based composite brake disc, comprising: an aluminum alloy matrix layer and a composite friction layer formed by friction welding; the composite friction layer comprises Al-Fe-V-Si aluminum alloy and reinforcing particles; the reinforcing particles are at least one of SiC, BN and TiC.

[0006] The brake disc provided by the present invention combines the aluminum alloy matrix layer and the composite friction layer by friction welding, which not only ensures that the brake disc has good toughness as a whole, but also improves wear resistance and heat resistance, thereby making the overall mechanical properties of the aluminum-based composite brake disc better and improving the reliability of the brake disc. The Al-Fe-V-Si aluminum alloy in the composite friction layer contains a high volume fraction of Al 12 (Fe,V)3Si nano-dispersed phase can improve the high temperature performance of the friction layer, and the addition of reinforcing particles can further improve the strength, modulus, wear resistance, fatigue resistance and thermal expansion of the alloy.

[0007] As a preferred solution, the tensile strength Rm of the base layer is ≥200 MPa, the elongation after fracture A is ≥9%, and the hardness is ≥65 HV0.2; and the aluminum alloy base layer is ZL101 aluminum alloy.

[0008] As a preferred solution, the reinforcing particles account for 15-30% of the total mass of the composite friction layer.

[0009] As a preferred solution, the particle size of the enhanced particles is 5-30 μm, and the distribution pattern is normal distribution.

[0010] As a preferred solution, the Al-Fe-V-Si aluminum alloy includes the following components in mass percentage: Fe 8.3~8.5%, Si 1.9~1.0%, V 1.2~1.4%, Zn 0.2~0.3%, Cr 0.1~0.3%, Mn 0.1~0.3%, Ti 0.1~0.3%, and the balance is aluminum.

[0011] As a preferred solution, the Al-Fe-V-Si aluminum alloy consists of the following components in mass percentage: Fe 8.42%, Si 1.93%, V 1.29%, Zn 0.25%, Cr 0.1%, Mn 0.1%, Ti 0.1%, and the balance is aluminum.

[0012] As a preferred solution, the friction layer has a tensile strength Rm ≥ 380 MPa, an elongation after fracture A ≥ 3%, a hardness ≥ 140 HV0.2, and a density of 2.9-3.0 g / cm 3 .

[0013] The present invention also provides a method for preparing a heat-resistant and high-strength passenger car aluminum-based composite brake disc, the process of which is: placing a composite friction layer on a substrate layer, adjusting the position and then performing stir friction welding to obtain the brake disc.

[0014] The present invention composites the friction layer and the base layer through the friction stir welding technology. During the welding process of this technology, the material will not undergo melting deformation as a whole, which can effectively avoid defects such as pores and shrinkage holes that are easily generated during aluminum alloy fusion welding, thereby improving the overall reliability and toughness of the brake disc.

[0015] As a preferred solution, the composite material friction layer and the matrix layer need to be surface cleaned before friction stir welding, and the process is: cleaning with caustic soda solution, then rinsing with ethanol, and then drying.

[0016] As a preferred solution, the preparation process of the composite friction layer is: the reinforcing particle powder is evenly mixed with the Al-Fe-V-Si aluminum alloy powder, and then the mixed powder is pressed into a green body by cold isostatic pressing, and then vacuum hot pressing sintering is performed, and then hot extrusion is performed to obtain the green body.

[0017] As a preferred solution, the vacuum hot pressing sintering process is: placing the green body in a vacuum hot pressing machine, the sintering temperature is 500-600°C, and the holding time is 3-5 hours at 70-80 MPa.

[0018] The combination of vacuum hot pressing sintering and hot extrusion can effectively eliminate defects such as pores in composite materials produced by powder metallurgy, while also improving the interface bonding between the aluminum matrix and the reinforcement phase particles and refining the grain size.

[0019] As a preferred solution, the conditions for the friction stir welding are: a stirring speed of 300-1200 r / min, a welding speed of 50-150 mm / min, and a stirring head inclination angle of 2-4°.

[0020] The friction stir welding adopted in the present invention generates heat through the friction between the high-speed rotating stirring head and the workpiece, so that the material to be welded is locally softened. When the stirring head moves along the welding interface, the plasticized material flows from the front end to the rear end of the stirring head under the action of the rotating friction force of the stirring head, and forms a dense solid phase weld under the extrusion of the stirring head. During the friction stir processing, the original defects near the contact surface of the base layer and the friction layer will be destroyed, thereby obtaining a finer and more uniform grain structure.

[0021] Specifically, the present invention also provides a detailed preparation process of a heat-resistant and high-strength passenger car aluminum-based composite brake disc, comprising the following steps: 1) Preparation of substrate layer: ZL101 aluminum alloy is machined and heat treated to form the desired shape; 2) Friction layer preparation: Aluminum-based composite materials are prepared by powder metallurgy hot extrusion process. 15 wt.%~30 wt.% of reinforcing particle powder is evenly mixed with commercial Al-Fe-V-Si powder, and then the mixed powder is pressed into a green body by cold isostatic pressing, and then placed in a vacuum hot press for vacuum hot pressing sintering. The sintering temperature is 580 ℃, and the hot pressing is maintained at 75 MPa for 4 h. The composite ingot is then hot extruded to form a plate.

[0022] 3) Brake disc composite: Place the friction layer on the base layer, adjust the position, fix the friction layer and the aluminum alloy base layer, and use stir friction welding to weld the friction layer and the aluminum alloy base layer to form a brake disc.

[0023] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are: 1) The composite brake disc provided by the present invention, based on the synergistic effect between the base layer and the friction layer, ensures the specific strength and specific stiffness of the brake disc, while also greatly improving the heat resistance of the brake disc, especially its mechanical properties under high temperature conditions above 300°C; the friction layer of the brake disc adopts Al-Fe-V-Si aluminum alloy as the base, and utilizes the finely dispersed Al 12 (Fe,V)3Si heat-resistant phase is used to achieve high temperature strengthening, and combined with ceramic reinforcing particles, the strength, modulus, wear resistance, fatigue resistance and thermal expansion of the material are further improved.

[0024] 2) In the preparation method provided by the present invention, a stir friction welding process is used to combine the base layer and the friction layer together. This process generates heat through the friction between the high-speed rotating stirring head and the workpiece, so that the welded material is locally softened. When the stirring head moves along the welding interface, the plasticized material flows from the front end to the rear end of the stirring head under the action of the rotating friction force of the stirring head, and forms a dense solid phase weld under the extrusion of the stirring head. In addition, during the stir friction processing, the original defects near the contact surface of the base layer and the friction layer will be destroyed, thereby obtaining a finer and more uniform grain structure.

[0025] 3) In the technical solution provided by the present invention, the friction layer uses a particle-reinforced aluminum-based composite material, and the matrix layer uses an aluminum alloy with good strength and toughness. The two materials are compounded together, which not only ensures that the brake disc has good toughness as a whole, but also improves wear resistance and heat resistance, thereby making the overall mechanical properties of the aluminum-based composite brake disc better and improving the reliability of the brake disc. After testing, the cross-sectional strength R m The stress strength is about 250 MPa at 300°C and the stress strength is still maintained above 100 MPa at 500°C, showing excellent high temperature performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a microstructure diagram of the friction layer of the composite material before friction stir lap welding in Example 1 of the present invention; Figure 2 This is a microstructure diagram of the friction layer of the composite material after friction stir lap welding in Example 1 of the present invention; Figure 3 This is a schematic structural diagram of the friction layer and the base layer in the cross-sectional view of the brake disc in Example 1 of the present invention; Figure 4 This is a structural diagram of a brake disc in Example 1 of the present invention; Figure 5 This is a stress strength test diagram of the brake disc in Example 1 of the present invention; in, Figure 5 (a) is a schematic diagram of the thermal simulation scheme of the composite material layer. Figure 5 (b) The strain rate is 0.1 s -1 Flow stress curve at Figure 5 (c) The strain rate is 1 s -1 Flow stress curve at Figure 5 (d) The strain rate is 10 s -1 Flow stress curve at . DETAILED DESCRIPTION

[0027] In order to facilitate the understanding of the present invention, the present invention will be described in more comprehensive and detailed manner in conjunction with the accompanying drawings and preferred embodiments of the specification. It should be noted that the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Example 1 This embodiment provides a heat-resistant and high-strength passenger car aluminum-based composite brake disc, and a specific preparation method thereof includes the following steps: 1. Base layer manufacturing With ZL101 aluminum alloy as raw material, the substrate layer is prepared by a casting method and then machined and heat treated to form the desired shape.

[0029] 2. Preparation of composite friction layer The composite friction layer is prepared by a powder metallurgy hot extrusion process. 15wt.% SiC powder is evenly mixed with commercial Al-Fe-V-Si powder, and then the mixed powder is pressed into a green body by cold isostatic pressing, and then placed in a vacuum hot press for vacuum hot pressing sintering. The sintering temperature is 580℃, and the hot pressing is maintained at 75MPa for 4 hours. In order to eliminate defects such as holes in the composite material prepared by powder metallurgy, improve the interface bonding between the aluminum matrix and the reinforcement phase particles, and refine the grain size, the composite ingot is then hot extruded to form a plate. Figure 1 As shown in the figure, it is the metallographic structure diagram of the material used for the friction layer. It can be seen from the figure that the SiC particles are fine and evenly distributed without obvious agglomeration.

[0030] 3. Composite of base layer and friction layer Place the cut friction layer on the base layer, adjust the position, fix the friction layer and the aluminum alloy base layer, and weld the friction layer and the aluminum alloy base layer by friction stir welding to form a brake disc. Figure 2 The figure shows the structure of the substrate layer and the friction layer prepared by the above method. During the friction stir processing, the stirring speed of the friction stir processing is 400 r / min, the welding speed is 50 mm / min, and the inclination angle of the stirring head is 2.5°. During the friction stir processing, the original defects near the contact surface of the substrate layer and the friction layer are broken, and a structure with a finer and more uniform grain size is obtained.

[0031] After testing, the interface bonding strength R between the base layer and the friction layer of the brake disc prepared in Example 1 is m ≈183 MPa, elongation at break A≥1%.

[0032] Example 2 This embodiment is exactly the same as the embodiment 1, except that the reinforcement particles selected for the aluminum-based composite material are TiC particles with a mass fraction of 15 wt.%.

[0033] After testing, the interface bonding strength R between the base layer and the friction layer of the brake disc prepared in Example 2 is m ≈181 MPa, elongation at break A≥1%.

[0034] Example 3 This embodiment is exactly the same as the embodiment 1, except that the reinforcement particles used in the aluminum-based composite material are 15 wt.% BN particles.

[0035] After testing, the interface bonding strength R between the base layer and the friction layer of the brake disc prepared in Example 3 is m ≈183 MPa, elongation at break A≥1%.

[0036] Example 4 This embodiment is exactly the same as Embodiment 1, except that the reinforcing particles used in the aluminum-based composite material are 25 wt.% SiC particles.

[0037] After testing, the interface bonding strength R between the base layer and the friction layer of the brake disc prepared in Example 4 is m ≈190 MPa, elongation at break A≥1%.

[0038] Example 5 This embodiment is exactly the same as the embodiment 1, except that the stirring speed of the friction stir processing is 600 r / min and the welding speed is 100 mm / min.

[0039] After testing, the interface bonding strength R between the base layer and the friction layer of the brake disc prepared in Example 4 is m ≈170 MPa, elongation at break A≥1%.

[0040] Example 6 This embodiment is exactly the same as the embodiment 1, except that the stirring speed of the friction stir processing is 800 r / min and the welding speed is 100 mm / min.

[0041] After testing, the interface bonding strength R between the base layer and the friction layer of the brake disc prepared in Example 4 is m ≈172MPa, elongation at break A≥1%.

[0042] In order to better understand the heat resistance of the brake disc provided by the present invention, the present invention also conducted stress strength tests at different temperatures on the brake disc obtained in Example 1. The test results are as follows: Figure 5 As shown, through Figure 5It can be seen that compared with most aluminum-based composites, SiCp / Al-Fe-V-Si exhibits better high-temperature resistance. When the deformation temperature is 300°C, the flow stress can be maintained at about 220MPa. When the deformation temperature reaches 500°C, the flow stress can still be maintained above 100MPa. This is mainly attributed to the presence of a large number of fine dispersed Al in the SiCp / Al-Fe-V-Si matrix. 12 (Fe,V)3Si heat-resistant phase.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A heat-resistant and high-strength passenger car aluminum-based composite brake disc, characterized in that: include: Aluminum alloy base layer and composite friction layer by friction welding; The composite friction layer comprises Al-Fe-V-Si aluminum alloy and reinforcing particles; The reinforcing particles are at least one of SiC, BN and TiC.

2. The heat-resistant and high-strength passenger car aluminum-based composite brake disc according to claim 1, characterized in that: The tensile strength Rm of the base layer is ≥200 MPa, the elongation after fracture A is ≥9%, and the hardness is ≥65 HV0.2; the aluminum alloy base layer is ZL101 aluminum alloy.

3. The heat-resistant and high-strength passenger car aluminum-based composite brake disc according to claim 1, characterized in that: The reinforcement particles account for 15-30% of the total mass of the composite material friction layer; the particle size of the reinforcement particles is 5-30 μm, and the distribution mode is normal distribution.

4. The heat-resistant and high-strength passenger car aluminum-based composite brake disc according to claim 1, characterized in that: The Al-Fe-V-Si aluminum alloy includes the following components in mass percentage: Fe 8.3-8.5%, Si 1.9-1.0%, V 1.2-1.4%, Zn 0.2-0.3%, Cr 0.1-0.3%, Mn 0.1-0.3%, Ti 0.1-0.3%, and the balance is aluminum.

5. The heat-resistant and high-strength passenger car aluminum-based composite brake disc according to claim 1 or 3, characterized in that: The friction layer has a tensile strength of Rm≥380 MPa, an elongation after fracture A≥3%, a hardness of ≥140 HV0.2, and a density of 2.9-3.0 g / cm 3 .

6. The method for preparing a heat-resistant and high-strength passenger car aluminum-based composite brake disc according to any one of claims 1 to 5, characterized in that: The composite material friction layer is placed on the substrate layer, and after adjusting the position, it is welded by stir friction welding to obtain the composite material.

7. The method for preparing a heat-resistant and high-strength passenger car aluminum-based composite brake disc according to claim 6, characterized in that: Before the friction stir welding, the friction layer and the matrix layer of the composite material need to be cleaned on the surface, and the process is: cleaning with a caustic soda solution, then rinsing with ethanol, and then drying.

8. The method for preparing a heat-resistant and high-strength passenger car aluminum-based composite brake disc according to claim 6, characterized in that: The preparation process of the composite friction layer is as follows: the reinforcing particle powder is evenly mixed with the Al-Fe-V-Si aluminum alloy powder, and then the mixed powder is pressed into a green body by cold isostatic pressing, and then vacuum hot pressing sintering is performed, and then hot extrusion is performed to obtain the green body.

9. The method for preparing a heat-resistant and high-strength passenger car aluminum-based composite brake disc according to claim 8, characterized in that: The vacuum hot pressing sintering process is as follows: placing the green body in a vacuum hot pressing machine, the sintering temperature is 500-600° C., and the holding time is 3-5 hours at 70-80 MPa.

10. The method for preparing a heat-resistant and high-strength passenger car aluminum-based composite brake disc according to claim 6, characterized in that: The conditions of the friction stir welding are as follows: a stirring speed of 300-1200 r / min, a welding speed of 50-150 mm / min, and a stirring head inclination angle of 2-4°.

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