WO2019178934A1

WO2019178934A1 - In-situ nano-reinforced aluminum alloy hub for new energy automobile and manufacturing method therefor

Info

Publication number: WO2019178934A1
Application number: PCT/CN2018/087959
Authority: WO
Inventors: 赵玉涛; 陶然; 陈刚; 王坤; 李维玉
Original assignee: 江苏大学
Priority date: 2018-03-20
Filing date: 2018-05-23
Publication date: 2019-09-26
Also published as: CN108559864A; CN108559864B

Abstract

A method for manufacturing a lightweight, high-strength, and fatigue-resistant in-situ nano-reinforced aluminum alloy hub for a new energy automobile. The method achieves nano-particle combined reinforcement by means of Orowan strengthening and grain boundary strengthening by employing an in-situ chemical melt reaction and achieves grain boundary strengthening by integrating long-acting combination modification and refinement. The method adopts nitrogen-argon composite rotary air refining and aluminum-rare earth purification technology to achieve multi-stage deep purification of an aluminum melt, forms a protective layer on the surface of the melt by leveraging the fact that the density of argon is higher than that of air, and introduces an aluminum-rare earth intermediate alloy to produce an intermediate compound having a density greater than that of the particles, thereby effectively achieving deep and efficient purification. The method also adopts a novel low-pressure forming technology of sequential solidification and rapid crystallization. Due to the shortening of crystallization time, the secondary dendrite arm spacing in the microstructure of a casting becomes shorter, the microstructure is refined, and the feeding effect is enhanced, such that the casting structure is denser, thus obtaining a hub having high-strength plasticity, high fatigue resistance, and high density. Further disclosed is the lightweight, high-strength, and fatigue resistant in-situ nano-reinforced aluminum alloy hub for a new energy automobile.

Description

In-situ nano-reinforced aluminum alloy wheel hub for new energy automobile and manufacturing method thereof

Technical field

The invention relates to a lightweight high-strength anti-fatigue in-situ nano-reinforced aluminum alloy wheel hub for a new energy automobile and a manufacturing method thereof, and belongs to the technical field of new energy automobile wheel hub preparation.

Background technique

At present, new energy vehicles represented by pure electric vehicles, hybrid vehicles and fuel cell vehicles are growing rapidly in the world. However, due to factors such as battery weight and cruising range, new energy vehicles are more urgent for lightweighting. Research shows that new energy vehicles use lightweight high-strength aluminum alloy wheels instead of traditional aluminum wheels, which can reduce the energy consumption of the whole vehicle by 3%. At the same time, because new energy vehicles are generally heavier than conventional vehicles of the same class, their hubs are subjected to greater loads and require higher strength and fatigue resistance. Therefore, new energy vehicle wheels have high requirements for light weight and performance.

A356.2 aluminum alloy has become the main material of automobile wheels because of its excellent casting properties, machinability, heat treatment, toughening design performance and fatigue resistance. Chinese patent 200910131282.8 discloses a wheel hub of aluminum alloy, which is further alloyed with Sr and mixed rare earth RE on the basis of the existing A356.2 alloy, which can effectively deteriorate Si and improve performance. Chinese patent 201610054783.0 discloses an aluminum alloy ingot for automobile wheel hub and a preparation method thereof. On the basis of A356.2 alloy, adding Ti, Eu and La elements and adjusting the content of Si, Mn and Mg elements can play the role of alloy structure. Deterioration and refinement to improve the mechanical properties of aluminum alloy wheels. However, the above process technology still has the following shortcomings and shortcomings: (1) the use of a large number of expensive rare earth elements to increase the cost of material manufacturing; (2) relying on conventional alloy precipitation strengthening to increase the material's strong plasticity is limited, It is often to reduce the plasticity to increase the strength; (3) the content of rare earth is difficult to control, and excessive addition will reduce the performance of the material. Therefore, there is an urgent need to develop a new type of wheel material.

In recent years, particle-reinforced aluminum-based composite materials have been gradually applied to the material of the hub, especially in-situ generation of nano-particle-reinforced aluminum-based composite materials, because their nano-reinforces are in-situ nucleated and grown from the aluminum matrix by chemical reaction. The thermodynamically stable phase, so that the surface of the reinforcing body is non-polluting, avoids the problem of poor compatibility with the matrix, has high interfacial bonding strength, and has a nano-size effect, has higher specific strength, specific modulus, and good heat resistance. Sex, friction resistance, corrosion resistance, and excellent fatigue resistance are important means to improve the comprehensive mechanical properties of automotive aluminum alloy materials, and have become a research hotspot for lightweight high-strength wheels for new energy vehicles. However, the following problems are easily encountered in the manufacturing process: (1) The direct reaction method of the melt, the reaction residue is liable to remain in the melt, and it is easy to wind into the melt due to the fluctuation inside the melt; (2) the generated nanoparticles are easy Agglomeration, uneven distribution, so it is easy to produce defects, resulting in low density.

Summary of the invention

The invention aims to develop a lightweight high-strength in-situ nano-reinforced aluminum alloy wheel hub and a manufacturing method thereof according to the deficiencies of the prior art, and adopts in-situ multi-particles and aging precipitation synergistic strengthening, melt deep purification and high-density low-pressure molding. Technology, significantly improve the strong plasticity and fatigue resistance of the hub.

The invention relates to a method for manufacturing a lightweight high-strength in-situ nano-reinforced aluminum alloy wheel hub, which realizes nano-particle composite strengthening by Orowan strengthening + fine grain strengthening through melt in-situ chemical reaction, integrating long-acting composite metamorphism, and composite refining , to achieve fine grain strengthening. The nitrogen-argon composite rotary air refining + aluminum-rare earth purification technology is used to realize the multi-stage deep purification of the aluminum melt, and the protective layer is formed on the surface of the melt by using the argon density higher than the air, and the introduction of the aluminum-rare earth intermediate alloy is combined. Produces intermediate compounds with a density greater than that of particles, effectively achieving deep and efficient purification. Finally, through the new low-pressure forming technology of sequential solidification + rapid crystallization, due to the shortening of crystallization time, the secondary dendrite arm spacing in the microstructure of the casting becomes shorter, the microstructure is refined, and the feeding effect is enhanced, the casting structure is more dense, and high-strength plasticity is obtained. High fatigue resistance and high density of the hub.

The manufacturing method of the present invention comprises the following steps:

(1) Melting of the alloy: The A356.2 alloy was melted at 720-780 ° C for 10 min. The A356.2 alloy is a commercial alloy, and its chemical composition is: Si 6.5-7, Mg 0.3-0.4, Fe 0.1-0.15, Cu ≤ 0.1, Mn ≤ 0.05, Zn ≤ 0.05, and the balance is Al.

(2) In-situ synthesis of nanoparticles: The melt melted and kept in step (1) is rapidly heated to 830-870 ° C, and the dried reactant powder is added through a high-purity graphite bell jar while applying an acousto-magnetic coupling field reaction. 30 min, then cool down to 720-760 ° C insulation.

(3) Adjustment of Mg and Si content and introduction of modifier and refiner: pure Mg and Al-Si intermediate alloy are added to the melt obtained in step (2), and the mixture is rotated by graphite to promote mixing and heat preservation for 10 min. Then, the Al-Sr and Al-RE composite modifiers and the Al-Ti-B and Al-Ti-C composite refiners were stirred with graphite and kept for 15 minutes.

(4) Purification of the melt: the step (3) is obtained to raise the temperature of the melt to 750-780 ° C, and the refining agent is sprayed into the melt through a spray gun for preliminary purification, and then the Al-Ce intermediate alloy is added, and the mixture is allowed to stand and kept warm for 10 -15min, secondary purification; finally, a certain proportion of nitrogen and argon are mixed and then passed into a graphite gas rotating nozzle, a graphite nozzle rotating at 300-600r/min is inserted into the melt, and then the mixed gas is A flow rate of 0.2-0.5 m ³ /h was sprayed into the melt for 10-20 min, and allowed to stand for 5-10 min.

(5) Low-pressure casting molding: the melt temperature obtained in step (4) is lowered to 720-750 ° C, and the melt is placed in a graphite crucible furnace sealed at a low-pressure casting machine (temperature is 680-750 ° C), and then introduced. Dry air, the melt rises along the riser tube at a speed of 25-45mm/s at a gas pressure of 0.04-0.08 MPa into a mold with a temperature of 300-400 ° C. After the mold is filled, the water cools the mold and increases. The pressure of 0.006-0.04MPa, the pressure is maintained at 250-400s, and the pressure is taken out to obtain the in-situ nano-composite reinforced aluminum alloy casting.

(6) Heat treatment: the wheel casting obtained in step (5) is subjected to T6 heat treatment, solution hardening: temperature 530-550 ° C, holding time 4 h-8 h, water quenching; artificial aging: temperature 170-180 ° C, holding time 2 6h. Finally, high strength in-situ nano-reinforced aluminum alloy wheels are obtained.

The composition of the in-situ synthesized nanoparticles in the step (2) is according to the weight percentage of the melt in the step (2): 1-3% of nano ZrB ₂ , 2-4% of nano Al ₂ O ₃ and 1-5% of nano TiB ₂ ternary particles. ZrB ₂ and TiB ₂ are uniformly distributed along the grain boundary, which can effectively pin the grain boundary and hinder the migration of grain boundaries, refine the grains, and Al ₂ O ₃ is uniformly distributed in the crystal, and the bonding strength with the matrix is high, which is dispersed. Strengthen the effect and improve the mechanical properties of the composite.

The reactant powders for the preparation of the reinforcing particles are K ₂ ZrF ₆ , K ₂ TiF ₆ and Na ₂ B ₄ O ₇ . The mass ratio is: 6-8:7-9:10-12 (in order to prevent the formation of Al ₃ Zr and Al ₃ Ti, the borax needs to be excessively 50%-70%), and the powder is added in the amount of the melt in the step (2). 20-40%.

The acousto-magnetic coupling field is a combination field of a low-frequency pulse magnetic field and a high-energy ultrasonic field, a low-frequency pulse magnetic field, a frequency of 10-20 Hz, a magnetic current of 100-200 A, a high-energy ultrasonic field, a power of 1000-1500 W, and a frequency of 15-30 kHz. The acoustic-magnetic coupling field can generate sound flow in two directions, avoiding the phenomenon of particle segregation outside the single magnetic field and the acoustic flow of a single ultrasonic field causing the cavitation bubble to be axially distributed along the horn; The coupling field ensures that the mass transfer heat transfer process of the entire aluminum alloy melt is completely carried out, so that the concentration of each region in the aluminum alloy melt is uniform, and the growth of the particles is suppressed. Therefore, the acousto-magnetic coupling field can not only avoid the disadvantages of a single physics field, but also amplify the advantages of a single physics field.

The content of Mg and Si is adjusted so that the content of Mg reaches 0.4-0.45, and the content of Si reaches 6.5-7.5. The purpose is to supplement the Mg and Si elements consumed by the high temperature reaction on the one hand, and further optimize Mg and on the other hand. The content of Si element increases the volume fraction of the Mg ₂ Si aging precipitation phase, enhances the aging precipitation strengthening, and improves the tensile strength of the material.

The composite modificator is 0.1-0.2 wt.% of the Al-10% Sr master alloy and 0.1-0.2 wt.% of the Al-10%RE master alloy obtained in the step (2), which can improve the conventional The metamorphism effect of Al-Sr master alloy tends to be degraded with the increase of the melt holding time. Therefore, the composite metamorphism technology is developed to ensure a good combination of the deterioration effect and the use time, so that the coarse eutectic Si phase becomes fine fiber and improves. Its strong plasticity.

The composite refiner is 0.1-0.2 wt.% of the melt mass obtained in the step (2), and the Al-5% Ti-1% B intermediate alloy and 0.1-0.2 wt.% of the Al-5% Ti- 0.2%C intermediate alloy, on the one hand, Al-Ti-C can compensate for the “poisoning” phenomenon in the refining process of Al-Ti-B intermediate alloy (TiB ₂ particles are easy to settle, the refining effect is reduced, and it is easy to become a crack propagation source. On the other hand, in the Al-Ti-C refiner, due to the small size of the TiC particles, the particles with small size cannot reduce the nucleation curvature of the critical nucleus, and the refinement effect is not as good as that of the Al-Ti-B intermediate alloy. Refinement technology to achieve the best refinement effect, through the fine-grained strengthening to improve the material's strong plasticity and fatigue properties.

The purification of the melt is mainly divided into rare earth purification and rotary jet refining. After the preliminary purification, 0.1 to 0.3 wt.% of the Al-10% Ce master alloy of the melt mass obtained in the step (3) is added to react with the Al ₂ O ₃ particles to form a density much larger than that of the Al ₂ O _{3 .} Ce ₂ O ₃ , its sinking speed is faster, effectively eliminating the inclusion of fine Al ₂ O ₃ inclusions; then using nitrogen-argon composite rotary blowing refining, the volume ratio of nitrogen to argon is: 3-6 : 1-5, using argon gas density greater than the characteristics of air to form a layer on the surface of the melt, reducing the phenomenon of inhalation during the refining of aluminum liquid, reducing the gas content of the aluminum liquid, the porosity of the cast aluminum parts, pinhole defects are significantly reduced, Combined with the excellent refining effect of nitrogen, it achieves high-efficiency purification effect, reduces defects caused by gases and inclusions, and improves material properties.

The low pressure casting molding refers to a new low pressure molding technology of sequential solidification + rapid crystallization. On the one hand, the low-pressure casting mold is changed from the traditional air-cooling to the water-cooling, which increases the cooling rate of the casting, accelerates the sequential solidification, shortens the crystallization time, shortens the secondary dendrite arm spacing in the microstructure of the casting, and refines the structure; Increasing the pressure during solidification crystallization of low-pressure casting, solidifying under pressure after the filling of aluminum liquid, continuously applying pressure to the aluminum liquid, and simultaneously solidifying and solidifying the melt under pressure while improving the feeding effect, realizing densification of the hub and crystal Grain refinement significantly improves the ductility and fatigue properties.

The invention relates to a lightweight high-strength in-situ nano-reinforced aluminum alloy wheel hub and a preparation method thereof, which utilizes multi-component composite nano-enhancement technology + composite metamorphism refining technology + deep purification technology + low-pressure forming technology to obtain uniform distribution of in-situ nanoparticles (particles) In-situ nano-reinforced aluminum alloy wheels with a size of 20-100 nm), fine grain (refinement of grain to ASTM standard 4) and fine-grained eutectic Si phase, the properties of which reach tensile strength ≥ 320 MPa, yield strength ≥240MPa, elongation ≥8%, so the wheel hub prepared by the invention can reduce the energy consumption of the new energy vehicle, enhance the endurance ability, make the braking, turning and speed increasing more sensitive and improve the safety.

DRAWINGS

Figure 1 is a flow chart of the manufacturing process of the present invention

2 is a (a) metallographic structure diagram of a conventional A356.2 alloy casting, and (b) a metallographic structure of the in-situ nano-reinforced aluminum alloy casting of the present invention. As can be seen from the two metallographic diagrams, the wheel castings produced by the present invention have fine crystal grains, and the fine fibrous Si phase is distributed along the grain boundaries.

Figure 3 is a diagram showing the distribution and topography of in-situ nanoparticles. It can be seen from the figure that the in-situ nanoparticles in the hub casting made by the invention are uniformly distributed along the grain boundary, and the particles are hexagonal, spherical and square, respectively ZrB ₂ , Al ₂ O ₃ and TiB ₂ .

Figure 4 is a tensile curve of the material, (a) a conventional A356.2 alloy casting, and (b) an in-situ nano-reinforced aluminum alloy wheel casting of the present invention.

detailed description

The embodiments of the present invention are further described below with reference to the accompanying drawings. The following embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation procedures are given, but the scope of protection of the present invention is not limited to the following. Example.

Example 1:

Preparation of in-situ nano-particle reinforced composite material: 100Kg commercial A356.2 alloy raw material is melted at 750 ° C for 10 min, and the temperature is further increased to 850 ° C. The K ₂ ZrF ₆ is dried and mixed and ground at 200 ° C in batches. , K ₂ TiF ₆ and Na ₂ B ₄ O ₇ powders (the amount of which is 4174 g, 5714 g, 7415 g, respectively, the mass ratio of the generated ZrB ₂ , TiB ₂ and Al ₂ O ₃ particles is 1:1: 2) Simultaneously open the acousto-magnetic coupling field (magnetic field: frequency 10 Hz, magnetic current 100 A; ultrasonic: power 1000 W, frequency 20 kHz) for 30 min, the reaction ends to remove the scum on the surface of the melt, and the temperature is lowered to 750 ° C for heat preservation.

Adjustment of composition and addition of composite deterioration refiner: 0.4wt.% of pure Mg of melt mass and 0.35wt.% of Al-20%Si intermediate alloy are added into the melt, and at the same time, the rotation of the graphite stirring rotor is promoted. Mix and keep for 10 min, then 0.1 wt.% Al-10% Sr and 0.1 wt.% Al-10% RE composite modifier and 0.1 wt.% Al-5% Ti-1% B and 0.1% Al-5% Ti-0.5% C composite refiner, immediately open the graphite rotor and stir for 15 min.

Purification of the melt: the melt is heated to 780 ° C, sprayed with the refining agent hexachloroethane for preliminary purification, then 0.1 wt.% of Al-10% Ce intermediate alloy is added, allowed to stand and kept for 10-15 min, twice Purification, finally, a ratio of 3:1 nitrogen and argon gas into a graphite gas rotating nozzle, a graphite nozzle rotating at 300r / min into the aluminum melt, mixed inert gas at a flow rate of 0.2m ³ / h It was sprayed into the melt for 20 minutes and allowed to stand for 10 minutes.

Low pressure casting: After the melt temperature drops to 750 ° C, the melt is placed in a graphite crucible furnace sealed at a low pressure casting machine (temperature is 750 ° C), and the dry air is introduced, and the melt pressure is 0.05 MPa. The mold is raised along the riser pipe at a speed of 25mm/s into a mold with a temperature of 300°C. When the mold is filled, the pressure is increased by 0.03MPa, the pressure is maintained for 300s, and the pressure is taken out to obtain the in-situ nano-composited aluminum alloy die-casting part. .

T6 heat treatment: the die-casting blank for cutting the pouring riser and the flashing edge is placed in the heat treatment furnace, solid solution quenching: temperature 545 ° C, holding time 4 h, water quenching; artificial aging: temperature 180 ° C, holding time 6 h. Finally, high strength in-situ nano-reinforced aluminum alloy wheels are obtained.

The mechanical properties of the sample were tested on the hub, the tensile strength was 325 MPa, the yield strength was 243 MPa, and the elongation was 11.5%. Under the conditions of bending moment of 2554N·m, rotation speed of 500r/min and nut torque of 120N·m, the bending fatigue test life is more than 6×10 ⁵ times, and the increase amount does not exceed 20% of the initial offset. qualified.

Example 2

Preparation of in-situ nano-particle reinforced composite material: 100Kg commercial A356.2 alloy raw material is melted at 750 ° C for 10 min, and the temperature is further increased to 850 ° C. The K ₂ ZrF ₆ is dried and mixed and ground at 200 ° C in batches. , K ₂ TiF ₆ and Na ₂ B ₄ O ₇ powders (the amount of addition is: 3542 g, 5134 g, 6844 g, the mass ratio of the generated ZrB ₂ , TiB ₂ and Al ₂ O ₃ particles is 1:2: 2, simultaneously open the acousto-magnetic coupling field (magnetic field: frequency 10Hz, magnetic current 100A; ultrasonic: power 1000W, frequency 20kHz) reaction for 30min, the reaction ends to remove the scum on the surface of the melt, until the temperature drops to 750 ° C insulation.

Adjustment of composition and addition of composite deterioration refiner: 0.4wt.% of pure Mg of melt mass and 0.35wt.% of Al-20%Si intermediate alloy are added into the melt, and at the same time, the rotation of the graphite stirring rotor is promoted. Mix and keep for 10 min, then 0.2 wt.% Al-10% Sr and 0.2 wt.% Al-10% RE composite modifier and 0.2 wt.% Al-5% Ti-1% B and 0.2 wt. % Al-5% Ti-0.5% C composite refiner, immediately open the graphite rotor and stir for 15 min.

Purification of the melt: the melt is heated to 780 ° C, sprayed with the refining agent hexachloroethane for preliminary purification, then 0.2 wt.% of Al-10% Ce intermediate alloy is added, allowed to stand and kept for 10-15 min, twice Purification, finally, a ratio of 3:1 nitrogen and argon gas into a graphite gas rotating nozzle, a graphite nozzle rotating at 300r / min into the aluminum melt, mixed inert gas at a flow rate of 0.2m ³ / h It was sprayed into the melt for 20 minutes and allowed to stand for 10 minutes.

Low-pressure casting: After the melt temperature drops to 750 °C, the melt is placed in a graphite crucible furnace sealed at a low-pressure casting machine (temperature is 750 °C), and the dry air is passed. The melt pressure is 0.06 MPa. The mold is raised along the riser tube at a speed of 25mm/s into a mold with a temperature of 300°C. When the mold is filled, the pressure is increased by 0.035MPa, the pressure is maintained for 300s, and the pressure is taken out to obtain the in-situ nano-composited aluminum alloy wheel casting. .

T6 heat treatment: the low-pressure casting blanks of the refining riser and the flashing edge are placed in a heat treatment furnace, and the solution quenching is performed at a temperature of 545 ° C, a holding time of 4 h, and water quenching; artificial aging: temperature of 180 ° C, holding time of 6 h. Finally, high strength in-situ nano-reinforced aluminum alloy wheels are obtained.

The mechanical properties of the sample were tested on the hub, the tensile strength was 320 MPa, the yield strength was 240 MPa, and the elongation was 9.1%. Under the conditions of bending moment of 2554N·m, rotation speed of 500r/min and nut torque of 120N·m, the bending fatigue test life is more than 6×10 ⁵ times, and the increase amount does not exceed 20% of the initial offset. qualified.

Example 3

Preparation of in-situ nano-particle reinforced composite material: 100Kg commercial A356.2 alloy raw material is melted at 750 ° C for 10 min, and the temperature is further increased to 850 ° C. The K ₂ ZrF ₆ is dried and mixed and ground at 200 ° C in batches. , K ₂ TiF ₆ and Na ₂ B ₄ O ₇ powders (the amount of which is 4174 g, 5714 g, 8786 g, respectively, the mass ratio of the generated ZrB ₂ , TiB ₂ and Al ₂ O ₃ particles is 1:1: 3) Simultaneously open the acousto-magnetic coupling field (magnetic field: frequency 10Hz, magnetic current 100A; ultrasonic: power 1000W, frequency 20kHz) for 30min, the reaction ends to remove the scum on the surface of the melt, and the temperature is lowered to 750 °C to keep warm.

Adjustment of composition and addition of composite deterioration refiner: 0.4wt.% of pure Mg of melt mass and 0.35wt.% of Al-20%Si intermediate alloy are added into the melt, and at the same time, the rotation of the graphite stirring rotor is promoted. Mix and keep for 10 min, then 0.1 wt.% Al-10% Sr and 0.1 wt.% Al-10% RE composite modifier and 0.1 wt.% Al-5% Ti-1% B and 0.1 wt. % Al-5% Ti-0.5% C composite refiner, immediately open the graphite rotor and stir for 15 min.

Low-pressure casting: After the melt temperature drops to 750 °C, the melt is placed in a graphite crucible furnace sealed at a low-pressure casting machine (temperature is 750 °C), and the dry air is introduced, and the melt pressure is 0.07 MPa. The mold is raised along the riser pipe at a speed of 25 mm/s into a mold with a temperature of 300 ° C. When the mold is filled, the pressure is increased by 0.04 MPa, the pressure is maintained for 300 s, and the pressure is taken out to obtain the in-situ nano-composited reinforced aluminum alloy wheel casting. .

The mechanical properties of the sample were tested on the hub, the tensile strength was 330 MPa, the yield strength was 250 MPa, and the elongation was 13.65%. Under the conditions of bending moment of 2554N·m, rotation speed of 500r/min and nut torque of 120N·m, the bending fatigue test life is more than 6×10 ⁵ times, and the increase amount does not exceed 20% of the initial offset. qualified.

In summary, the embodiments of the present invention have the following remarkable effects: tensile strength, yield strength, elongation and fatigue strength are significantly improved; the above examples have a content of particles, a content of a composite deterioration refiner, and a coagulation pressure. Differently, it can be seen that the composite refinement and deterioration refiner should not be added too much, and it is easy to produce over-deterioration and refinement effect, and appropriately increasing the crystallization solidification pressure and the content of the granule can increase the density of the material and improve the overall performance of the material. It can be seen that the comprehensive performance of the inventive example 3 is the best, the performance index always shows better performance than the base alloy, and various mechanical properties can meet the requirements of the material of the automobile hub.

The invention provides a lightweight high-strength in-situ nano-reinforced aluminum alloy wheel hub and a manufacturing method thereof, and an innovative development of a multi-component composite nano-strengthening technology + a composite metamorphic refining technology + a deep purification technology + a low-pressure forming technology to obtain a light and high strength The automobile wheel hub provides a reference for the preparation of high-performance lightweight wheels in the future, and has broad market prospects and economic value.

The above description is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims

The invention relates to a method for manufacturing an in-situ nano-reinforced aluminum alloy wheel hub for a new energy automobile, which is characterized in that a multi-component nano-reinforced particle is prepared by in-situ synthesis and applying an acousto-magnetic coupling field with a mixed powder containing a reinforcing element as a reactant. Through the in-situ chemical reaction of the melt, the nanoparticle composite strengthening is achieved by Orowan strengthening + fine grain strengthening; then pure Mg, Al-Si intermediate alloy, Al-Sr+Al-RE long-acting composite modifier and Al-Ti- are added. B+Al-Ti-C composite refiner, integrated long-acting composite modification, and composite refinement to achieve fine-grained strengthening; using nitrogen-argon composite rotary blowing refining + aluminum-rare earth purification technology to achieve multi-stage aluminum melt Deep purification, using a argon density greater than the characteristics of air to form a protective layer on the surface of the melt, combined with the introduction of aluminum-rare earth intermediate alloy to produce intermediate compounds with a density greater than the particles, effectively achieving deep and efficient purification; by sequential solidification + rapid crystallization The low-pressure casting technology shortens the crystallization time, shortens the distance between the secondary dendrite arms in the microstructure of the casting, refines the structure, and enhances the feeding effect, making the casting structure more compact. Finally, Obtained by heat treating the casting of high strength plastic, high fatigue resistance and high densification of the hub.
The method for manufacturing an in-situ nano-reinforced aluminum alloy wheel hub for a new energy vehicle according to claim 1, wherein the specific steps are as follows:

(1) Melting of the alloy: melting the A356.2 alloy at 720-780 ° C for 10 min;

(2) In-situ synthesis of nanoparticles: The melt melted and kept in step (1) is rapidly heated to 830-870 ° C, and the dried reactant powder is added through a high-purity graphite bell jar while applying an acousto-magnetic coupling field reaction. 30min, then cooled to 720-760 ° C insulation;

(3) Adjustment of Mg and Si content and introduction of modifier and refiner: pure Mg and Al-Si intermediate alloy are added to the melt obtained in step (2), and the mixture is rotated by graphite to promote mixing and heat preservation for 10 min. Then, the Al-Sr and Al-RE composite modifier and the Al-Ti-B and Al-Ti-C composite refiner are stirred by graphite and kept for 15 minutes;

(4) Purification of the melt: the step (3) is obtained to raise the temperature of the melt to 750-780 ° C, and the refining agent is sprayed into the melt through a spray gun for preliminary purification, and then the Al-Ce intermediate alloy is added, and the mixture is allowed to stand and kept warm for 10 -15min, secondary purification; finally, nitrogen and argon are mixed and then passed into a graphite gas rotating nozzle, a graphite nozzle rotating at 300-600r/min is inserted into the melt, and then the mixed gas is 0.2-0.5. The flow rate of m 3 /h is sprayed into the melt for 10-20 min, and allowed to stand for 5-10 min;

(5) Low-pressure casting molding: the melt temperature obtained in the step (4) is lowered to 720-750 ° C, and the melt is placed in a graphite crucible furnace sealed at a low pressure casting machine at a temperature of 680-750 ° C, and then dried. The air, the melt rises along the riser tube at a speed of 25-45 mm/s at a gas pressure of 0.04-0.08 MPa into a mold with a temperature of 300-400 ° C. After the mold is filled, the water cools the mold and increases by 0.006. -0.04MPa pressure, pressure holding 250-400s, pressure release take-up, to obtain in-situ nano-composite reinforced aluminum alloy castings;

(6) Heat treatment: the wheel casting obtained in step (5) is subjected to T6 heat treatment, solution hardening: temperature 530-550 ° C, holding time 4 h-8 h, water quenching; artificial aging: temperature 170-180 ° C, holding time 2 6h; Finally, in-situ nano-reinforced aluminum alloy wheels for new energy vehicles were obtained.
The method for manufacturing an in-situ nano-reinforced aluminum alloy wheel hub for a new energy vehicle according to claim 2, wherein the composition of the in-situ synthesized nanoparticles in the step (2) is in accordance with step (2) The weight percentage of the melt is: 1-3% of nano ZrB 2 , 2-4% of nano Al 2 O 3 and 1-5% of nano TiB 2 ternary particles; ZrB 2 and TiB 2 are uniformly distributed along the grain boundary It can effectively pin the grain boundary and hinder the migration of grain boundaries, refine the grains, and Al 2 O 3 is evenly distributed in the crystal, and has high bonding strength with the matrix, which acts as a dispersion strengthening and improves the mechanical properties of the composite. .
A method of manufacturing an in-situ nano-reinforced aluminum alloy wheel for a new energy vehicle according to claim 2, wherein the reactant powder for preparing the reinforcing particles is K 2 ZrF 6 , K 2 TiF 6 and Na 2 . B 4 O 7 , the mass ratio is: 6-8:7-9:10-12, in order to prevent the formation of Al 3 Zr and Al 3 Ti, the borax needs an excess of 50%-70%, the powder addition amount is the step (2 ) 20-40% of the melt.
The method for manufacturing an in-situ nano-reinforced aluminum alloy wheel hub for a new energy vehicle according to claim 2, wherein the acousto-magnetic coupling field is a combination field of a low-frequency pulse magnetic field and a high-energy ultrasonic field, and a low-frequency pulse magnetic field. The frequency is 10-20Hz, the magnetic current is 100-200A; the high-energy ultrasonic field has a power of 1000-1500W and the frequency is 15-30kHz; the acoustic-magnetic coupling field can generate sound flow in two directions, which can avoid particles caused by a single magnetic field. The phenomenon of the outer side of the segregation and the acoustic flow of the single ultrasonic field cause the cavitation bubbles to be distributed along the axial direction of the horn; and the acoustic-magnetic coupling field ensures that the mass transfer heat transfer process of the entire aluminum alloy melt is completely performed, so that the aluminum alloy melt The concentration of each region is uniform, and the growth of the particles is suppressed. The acoustic-magnetic coupling field can not only avoid the disadvantages of a single physical field, but also magnify the advantages of a single physical field.
The method for manufacturing an in-situ nano-reinforced aluminum alloy wheel hub for a new energy automobile according to claim 2, wherein the Mg and Si content are adjusted so that the content of Mg reaches 0.4-0.45, and the content of Si It reaches 6.5-7.5, the purpose of which is to supplement the Mg and Si elements consumed by the high temperature reaction on the one hand, and further optimize the content of Mg and Si elements on the other hand, increase the volume fraction of the Mg 2 Si aging precipitation phase, enhance the aging precipitation strengthening, and improve The tensile strength of the material.
The method for manufacturing an in-situ nano-reinforced aluminum alloy wheel hub for a new energy vehicle according to claim 2, wherein the composite modificator is 0.1-0.2 wt of the melt mass obtained in the step (2). % Al-10%Sr master alloy and 0.1-0.2wt.% Al-10%RE master alloy can improve the deterioration of conventional Al-Sr master alloy and tend to decline with the increase of melt holding time, so development The composite metamorphism technology ensures a good combination of the deterioration effect and the use time, so that the coarse eutectic Si phase becomes a fine fiber and improves its strong plasticity.
The method for manufacturing an in-situ nano-reinforced aluminum alloy wheel hub for a new energy vehicle according to claim 2, wherein the composite refiner is 0.1-0.2 wt of the melt mass obtained in the step (2). .% Al-5% Ti-1% B master alloy and 0.1-0.2 wt.% Al-5% Ti-0.2% C master alloy, on the one hand Al-Ti-C can make up for Al-Ti-B master alloy The “poisoning” phenomenon that occurs during the refining process, that is, TiB 2 particles are easy to settle, the refining effect is reduced, and it is easy to become a crack propagation source. On the other hand, the Al-Ti-C refiner has small size and small size due to TiC particles. The particles can not reduce the nucleation curvature of the critical nucleus, and the refinement effect is not as good as that of the Al-Ti-B intermediate alloy. Therefore, the composite refining technology is developed to achieve the best refinement effect, and the strong plasticity of the material is improved by fine grain strengthening. Fatigue performance.
The method for manufacturing an in-situ nano-reinforced aluminum alloy wheel hub for a new energy automobile according to claim 2, wherein the purification of the melt is mainly divided into rare earth purification and rotary jet refining, after preliminary purification, added in step (3) 0.1-0.3wt.% of the melt mass obtained intermediate Al-10% Ce alloy, reacted with Al 2 O 3 particles occurs, generating much greater than the density of Al Ce 2 O 3 2 O 3 of The sinking speed is faster, and the removal of fine Al 2 O 3 inclusions is effectively realized; then, the nitrogen-argon composite rotary air blowing refining is adopted, and the volume ratio of nitrogen to argon is 3-6:1-5. The argon gas density is greater than the characteristics of air to form a layer on the surface of the melt, which reduces the gettering phenomenon during the refining of the aluminum liquid, reduces the gas content of the aluminum liquid, and significantly reduces the pores and pinhole defects of the cast aluminum part, and is excellent in combination with nitrogen. Refining effect, achieving high-efficiency purification effect, reducing defects caused by gases and inclusions, and improving material properties.
A method for manufacturing an in-situ nano-reinforced aluminum alloy wheel hub for a new energy vehicle according to claim 2, wherein said low-pressure casting molding refers to a novel low-pressure molding technique of sequential solidification + rapid crystallization; The low-pressure casting mold is changed from the traditional air-cooling to the water-cooling, which increases the cooling rate of the casting, accelerates the sequential solidification, shortens the crystallization time, shortens the distance between the secondary dendrite arms in the microstructure of the casting, and refines the structure; The pressure at the time of casting solidification crystallization is solidified under pressure after the filling of the aluminum liquid, and the pressure is continuously applied to the aluminum liquid, and the melt is crystallized and solidified under pressure while improving the shrinking effect, thereby realizing densification of the hub and fine grain. Chemically, significantly improve the strong plasticity and fatigue properties.