Carbon nanotube reinforced aluminum alloy composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of metal-based composite materials, in particular to a carbon nano tube reinforced aluminum alloy composite material and a preparation method and application thereof.The preparation method comprises the following steps that (1) an aluminum alloy raw material is divided into two parts, one part is melted into a low-temperature melt, and the other part is melted into a high-temperature melt; 2) mixing a carbon nanotube with the low-temperature melt to form a low-temperature composite melt; and (3) the high-temperature melt and the low-temperature composite melt are mixed, and the mixed melt is subjected to degassing, refining and die-casting forming. According to the preparation method of the carbon nanotube reinforced aluminum alloy composite material, the problems that carbon nanotubes are prone to agglomeration and poor in dispersity in a high-temperature melt are solved, and the mechanical property and the heat-conducting property of the composite material are remarkably improved; meanwhile, the preparation method is simple in condition, environmentally friendly, suitable for industrial production and capable of being widely applied to manufacturing of high-performance light-weight parts in the fields of automobiles, aerospace and the like.

Description

Technical Field

[0001] This invention relates to the field of metal matrix composites, specifically to a carbon nanotube-reinforced aluminum alloy composite material, its preparation method, and its application. Background Technology

[0002] ADC12 aluminum alloy, as a typical hypoeutectic aluminum-silicon alloy, has become the preferred material for key components such as automotive engine blocks and transmission housings due to its excellent casting fluidity, low hot cracking tendency, and high corrosion resistance. However, with the increasing demand for lightweight, high-strength and tough materials in the fields of new energy vehicles and aerospace, the mechanical properties (such as tensile strength, which is usually below 300 MPa) and thermal conductivity (approximately 96 W / m·K) of traditional ADC12 alloys are no longer sufficient to meet the performance requirements under extreme operating conditions.

[0003] To overcome performance bottlenecks, researchers have attempted to introduce carbon nanotubes (CNTs) as a reinforcing phase, utilizing their ultra-high strength (~63 GPa) and thermal conductivity (>3000 W / m·K) to improve the performance of composite materials. However, existing preparation processes for CNTs-reinforced aluminum alloys have the following technical defects: 1. CNT damage and agglomeration caused by high-temperature melt: Traditional processes directly add CNTs to aluminum melt above 700℃, but under high-temperature conditions: the CNTs surface oxidizes (generating CO / CO2), leading to structural defects (Raman spectrum D peak intensity increases by >30%); the melt viscosity decreases, and CNTs are more prone to agglomeration due to weakened Brownian motion (SEM shows cluster size >5 μm). Despite using a protective atmosphere (such as Ar gas covering), the loss of mechanical properties of CNTs cannot be avoided (tensile strength decreases by 15%-20%); 2. Limitations of dispersion processes: Pure mechanical stirring: Conventional paddle stirring (500-1000 rpm) can only produce macroscopic flow, with limited effect on the nanoscale dispersion of CNTs (dispersion uniformity <80%), and high speed easily entraps gas (porosity >1.5%); Single ultrasonic treatment: Although ultrasonic cavitation (20-40 kHz) can break up clusters, cavitation in high-temperature melts is limited. Poor bubble stability and short effective action time (<10 minutes) make it difficult to achieve uniform dispersion of the entire melt; homogeneous electromagnetic stirring: existing technologies mostly use unidirectional / same-frequency electromagnetic fields, resulting in a single melt flow field and disordered CNT orientation (anisotropy index <0.3), which cannot take into account both macroscopic convection and microscopic shear; 3. Bottleneck in industrial production: existing processes rely on high-energy ball milling for pre-dispersion or complex jet deposition equipment (increasing costs by 30%-50%), and are difficult to adapt to the high-speed filling requirements of die casting production lines (filling time <100ms).

[0004] Therefore, it is of great significance to improve the mechanical and thermal properties of ADC12 aluminum alloy and solve the problem of poor dispersion of carbon nanotubes in high-temperature melts. Summary of the Invention

[0005] The purpose of this invention is to provide a carbon nanotube-reinforced aluminum alloy composite material and its preparation method. The preparation method of this carbon nanotube-reinforced aluminum alloy composite material is based on a stepwise melt mixing process. The ADC12 aluminum alloy raw material is divided into two parts: a low-temperature melt and a high-temperature melt. By pre-mixing carbon nanotubes with the low-temperature melt of ADC12 aluminum alloy, and then adding the high-temperature melt of ADC12 aluminum alloy to the low-temperature melt, the problem of easy agglomeration and poor dispersibility of carbon nanotubes in the high-temperature melt is solved, and the mechanical properties and thermal conductivity of the composite material are significantly improved. At the same time, the preparation method of this invention is simple, environmentally friendly, and suitable for industrial production. It can be widely used in the manufacture of high-performance lightweight components in the automotive, aerospace and other fields.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing carbon nanotube-reinforced aluminum alloy composite materials, the method comprising the following steps: 1) Divide the aluminum alloy raw material into two parts: one part is melted into a low-temperature melt, and the other part is melted into a high-temperature melt; 2) Carbon nanotubes are mixed with a low-temperature melt to form a low-temperature composite melt; 3) Mix the high-temperature melt with the low-temperature composite melt, degas the mixed melt, refine it, and then die-cast it.

[0007] Preferably, in step 1), the aluminum alloy raw material is of type ADC12.

[0008] Preferably, in step 1), the cryogenic melt is melted at a temperature of 580℃-640℃, and its mass fraction in the aluminum alloy raw material is 30%-40%. The high-temperature melt is melted at a temperature of 760℃-860℃, and its mass fraction in the aluminum alloy raw material is 60%-70%.

[0009] Preferably, in step 2), the amount of carbon nanotubes added is 0.1%-2.0% of the total weight of the ADC12 aluminum alloy.

[0010] Preferably, in step 2), the mixing conditions include: mechanical stirring at a stirring rate of 300 rpm to 800 rpm for 5 min to 10 min, followed by ultrasonication at an ultrasonic frequency of 20 kHz to 40 kHz for 15 min to 20 min.

[0011] Preferably, in step 2), the surface of the carbon nanotubes is modified with a coupling agent.

[0012] Preferably, the coupling agent modification includes: dispersing carbon nanotubes in a coupling agent ethanol solution after acidification treatment, stirring the reaction for 2-4 hours, and removing the solvent to obtain carbon nanotubes modified with the coupling agent.

[0013] Preferably, the coupling agent is a silane coupling agent and / or a titanate coupling agent.

[0014] Preferably, in step 3), the mass ratio of the high-temperature melt to the low-temperature composite melt is 2-4:1.

[0015] Preferably, in step 3), the mixing conditions include: adding the high-temperature melt to the low-temperature composite melt at a rate of 5 kg / min to 15 kg / min under the condition of a temperature of 650℃-680℃, while simultaneously performing electromagnetic stirring under the conditions of a magnetic field frequency of 20 Hz-100 Hz and a magnetic induction intensity of 0.1 T-0.5 T for a stirring time of 20 min-40 min; The direction of the electromagnetic stirring is opposite to the direction of the mechanical stirring in step 2) when mixing carbon nanotubes and low-temperature melt.

[0016] In a second aspect, the present invention provides a carbon nanotube-reinforced aluminum alloy composite material, which is prepared by the preparation method described in the first aspect.

[0017] Thirdly, the present invention provides an application of carbon nanotube-reinforced aluminum alloy composite material in the manufacture of high-performance lightweight components in the automotive and aerospace fields, wherein the carbon nanotube-reinforced aluminum alloy composite material is the carbon nanotube-reinforced aluminum alloy composite material described in the second aspect.

[0018] Compared with the prior art, the carbon nanotube-reinforced aluminum alloy composite material, its preparation method, and its application of the present invention have at least the following beneficial effects: 1) First, pre-disperse carbon nanotubes (CNTs) in a low-temperature melt (580℃-640℃) to avoid high-temperature damage to the carbon nanotubes; then, maintain the melt viscosity by gradient heating (650℃-680℃) to inhibit the CNTs from floating. 2) Using coupling agents to modify CNTs, the coupling agent layer reacts with Al³⁺ in the aluminum melt to form Al-O-Si bonds, which can enhance the interfacial bonding force between CNTs and metal, thereby improving the interfacial bonding strength. 3) Set up reverse electromagnetic-mechanical stirring to create turbulent shearing (shear rate > 500 s⁻¹) to achieve a CNT dispersion uniformity > 95%; 4) This invention can be directly adapted to the melting and heat preservation system of a die-casting machine without the need for additional equipment, and has good process compatibility; This invention utilizes core technologies such as stepwise melt mixing process, carbon nanotube (CNT) surface modification, and electromagnetic-mechanical synergistic control to produce carbon nanotube reinforced aluminum alloy composite material (CNTs-ADC12 aluminum alloy composite material). This material significantly surpasses traditional ADC12 aluminum alloy in terms of mechanical properties, thermal conductivity, and industrial adaptability, and can be more widely used in the manufacture of high-performance lightweight components in the automotive, aerospace, and other fields.

[0019] Meanwhile, the preparation method of the present invention is simple, the reaction conditions are mild, and it is green and environmentally friendly, with broad application prospects.

[0020] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 The image shows a scanning electron microscope (SEM) image of CNT clusters in the low-temperature composite melt in step (3) of Example 1. Figure 2 The fracture morphology of the 0.1 wt.% CNTs-ADC12 aluminum alloy composite material prepared in Example 1 is shown. Figure 3 The fracture morphology of ADC12 aluminum alloy raw material. Detailed Implementation

[0022] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] In a first aspect, the present invention provides a method for preparing carbon nanotube-reinforced aluminum alloy composite materials, the method comprising the following steps: 1) Divide the aluminum alloy raw material into two parts: one part is melted into a low-temperature melt, and the other part is melted into a high-temperature melt; 2) Carbon nanotubes are mixed with a low-temperature melt to form a low-temperature composite melt; 3) Mix the high-temperature melt with the low-temperature composite melt, degas the mixed melt, refine it, and then die-cast it.

[0025] In a preferred embodiment of the present invention, in step 1), the aluminum alloy raw material is of type ADC12.

[0026] In a preferred embodiment of the present invention, in step 1), the low-temperature melt is melted at a temperature of 580℃-640℃, and the mass fraction of the aluminum alloy raw material is 30%-40%. 30%-40% of the ADC12 aluminum alloy raw material is melted at 580℃-640℃ to form a low-temperature melt. Within this temperature range, the melt viscosity is relatively high (3.0 MPa·s - 3.8 MPa·s), which is beneficial for encapsulating CNTs and inhibiting their oxidation (oxidation weight loss rate <3%).

[0027] In a preferred embodiment of the present invention, in order to ensure that the alloying elements (such as Si and Cu) are fully dissolved and to avoid component segregation, in step 1), the high-temperature melt is melted at a temperature of 760°C-860°C and has a mass fraction of 60%-70% in the aluminum alloy raw material.

[0028] In a preferred embodiment of the present invention, in step 2), the amount of carbon nanotubes added is 0.1%-2.0% of the total weight of the ADC12 aluminum alloy.

[0029] In a preferred embodiment of the present invention, in step 2), the mixing conditions include: mechanical stirring at a stirring rate of 300 rpm to 800 rpm for 5 min to 10 min, followed by ultrasonication at an ultrasonic frequency of 20 kHz to 40 kHz for 15 min to 20 min, which can reduce the size of CNT clusters from the original 5 μm to 10 μm to 0.5 μm to 1.0 μm, with a dispersion uniformity >90%.

[0030] In a preferred embodiment of the present invention, in step 2), the surface of the carbon nanotubes is modified with a coupling agent.

[0031] In a preferred embodiment of the present invention, the coupling agent modification includes: dispersing carbon nanotubes in a coupling agent ethanol solution after acidification treatment, stirring the reaction for 2-4 hours, and removing the solvent to obtain carbon nanotubes modified with the coupling agent.

[0032] In a preferred embodiment of the present invention, the acidification treatment conditions include: placing CNTs in a 3 mol / L-5 mol / L nitric acid solution and refluxing at 80°C for 3 hours to introduce -COOH / -OH functional groups.

[0033] In a preferred embodiment of the present invention, the acidification treatment conditions include: placing CNTs in a mixed acid solution of nitric acid and sulfuric acid with a volume ratio of 1:3, and refluxing at 80°C for 3 hours.

[0034] In a preferred embodiment of the present invention, the coupling agent is a silane coupling agent and / or a titanate coupling agent.

[0035] In a preferred embodiment of the present invention, the conditions for coupling agent modification include: dispersing acidified CNTs in an ethanol solution containing 1 wt%-3 wt% silane coupling agent (KH550 / KH560), stirring at 60°C for 3 hours to form Si-OC covalent bonds.

[0036] In a preferred embodiment of the present invention, the conditions for modification with coupling agent include: dispersing acidified CNTs in an ethanol solution containing 0.5wt%-5wt% titanate coupling agent (NDZ-201), stirring at 70°C for 4 hours to obtain modified CNTs.

[0037] In a preferred embodiment of the present invention, the solvent removal conditions include: vacuum drying at 50°C for 12 hours to obtain modified CNTs with a surface-coated coupling agent layer.

[0038] In a preferred embodiment of the present invention, in step 3), the mass ratio of the high-temperature melt to the low-temperature composite melt is 2-4:1.

[0039] In a preferred embodiment of the present invention, in order to avoid the oxidation of CNTs caused by direct contact between the low-temperature melt and the high-temperature melt, the system temperature is gradually increased by utilizing the heat of the high-temperature melt to maintain a semi-solid state (solidity 10-20%) and suppress the floating of CNTs (segregation rate <5%). In step 3), the mixing conditions include: adding the high-temperature melt to the low-temperature composite melt at a rate of 5 kg / min-15 kg / min under the condition of a temperature of 650℃-680℃, and simultaneously performing electromagnetic stirring under the conditions of a magnetic field frequency of 20 Hz-100 Hz and a magnetic induction intensity of 0.1 T-0.5 T for a stirring time of 20 min-40 min. The direction of the electromagnetic stirring is opposite to the direction of the mechanical stirring in step 2) when mixing carbon nanotubes and low-temperature melt.

[0040] In a preferred embodiment of the present invention, the electromagnetic stirring further includes: a. Segmented control of magnetic field frequency: The magnetic field frequency is 20 Hz - 40 Hz in the initial injection stage to promote melt convection, and the magnetic field frequency is 50 Hz - 80 Hz in the later dispersion stage to enhance micro-shearing. b. Magnetic induction intensity gradient design: Set up 3-5 stirring zones along the melt flow direction, with the intensity increasing from 0.1 T to 0.3 T to form a progressive turbulent field; c. The stirring direction is opposite to that in step 2) when the carbon nanotubes are mixed with the low-temperature melt. For example, if the mechanical paddle rotates clockwise, the electromagnetic field rotates counterclockwise, and the shear rate is superimposed to 800 s⁻¹-1000 s⁻¹.

[0041] By setting such electromagnetic stirring conditions, a synergistic effect is achieved, which increases the uniformity of CNT dispersion to 98%, and they are oriented along the magnetic field direction with an anisotropy index >0.7.

[0042] In a preferred embodiment of the present invention, in step 3), the mixed melt is degassed using a rotary degasser with a vacuum degree of <5 kPa.

[0043] In a preferred embodiment of the present invention, in step 3), the refining conditions include: 0.2 wt% C2Cl6 addition.

[0044] In a preferred embodiment of the present invention, in step 3), the die-casting conditions include: die-casting at 580℃-620℃, filling time <100 ms, which is directly compatible with the existing die-casting machine heat preservation system.

[0045] In a second aspect, the present invention provides a carbon nanotube-reinforced aluminum alloy composite material, which is prepared by the preparation method described in the first aspect.

[0046] Thirdly, the present invention provides an application of carbon nanotube-reinforced aluminum alloy composite material in the manufacture of high-performance lightweight components in the automotive and aerospace fields, wherein the carbon nanotube-reinforced aluminum alloy composite material is the carbon nanotube-reinforced aluminum alloy composite material described in the second aspect.

[0047] The present invention will be described in detail below through examples. In the following examples, the pharmaceuticals and agents are all conventional commercially available products.

[0048] Preparation Example 1 Carbon nanotubes (CNTs) were placed in a 4 mol / L nitric acid solution and refluxed at 80°C for 3 hours to obtain acidified CNTs. Acidified CNTs were dispersed in an ethanol solution containing 2 wt% silane coupling agent (KH550) and stirred at 60°C for 3 hours to obtain modified CNTs.

[0049] Preparation Example 2 The modified CNTs were prepared by replacing the "silane coupling agent (KH550)" in Preparation Example 1 with "silane coupling agent (KH560)".

[0050] Preparation Example 3 Carbon nanotubes (CNTs) were placed in a mixed acid solution (v HNO3 :v H2SO4 In a mixture of 1:3, the mixture was refluxed at 80°C for 3 hours to obtain acidified CNTs; Acidified CNTs were dispersed in an ethanol solution of 3 wt% titanate coupling agent (NDZ-201) and stirred at 70 °C for 4 hours to obtain modified CNTs.

[0051] Example 1 (1) Raw material preparation: The total weight of the ADC12 aluminum alloy is 10 kg: 3 kg for the low-temperature section and 7 kg for the high-temperature section. The modified carbon nanotubes (CNTs) added in Preparation Example 1 were 0.1 wt%: 10 g; (2) Melt preparation: 3 kg of ADC12 aluminum alloy was melted at 580℃ to obtain a cryogenic melt; 7 kg of ADC12 aluminum alloy was melted at 800℃ to obtain a high-temperature melt; (3) Preparation of composite materials: Modified CNTs were added to the low-temperature melt, and then mechanically stirred at a stirring rate of 500 rpm, while being ultrasonically treated at an ultrasonic frequency of 30 kHz for 20 min to obtain the low-temperature composite melt. High-temperature melt was injected into low-temperature composite melt at a rate of 10 kg / min, and electromagnetic stirring was started simultaneously. The working conditions were 30 Hz / 0.2 T for the first 10 minutes and 60 Hz / 0.4 T for the next 20 minutes. The mixing temperature was 650℃ and the total stirring time was 30 minutes, thus obtaining the alloy composite material. (4) The alloy composite material obtained in step (3) was degassed and refined and then die-cast into standard specimens to obtain 0.1wt.%CNTs-ADC12 aluminum alloy composite material.

[0052] Example 2 (1) Raw material preparation: The total weight of the ADC12 aluminum alloy is 10 kg: 3 kg for the low-temperature section and 7 kg for the high-temperature section. Preparation Example 2: Modified CNTs addition amount 0.5 wt%: 50 g, (2) Melt preparation: 3 kg of ADC12 aluminum alloy was melted at 600℃ to obtain a cryogenic melt; 7 kg of ADC12 aluminum alloy was melted at 800℃ to obtain a high-temperature melt; (3) Preparation of composite materials: Modified CNTs were added to the low-temperature melt, and then mechanically stirred at a stirring rate of 600 rpm, while being ultrasonically treated at an ultrasonic frequency of 30 kHz for 20 min to obtain the low-temperature composite melt. High-temperature melt was injected into low-temperature composite melt at a rate of 10 kg / min, and electromagnetic stirring was started simultaneously. The working conditions were 30 Hz / 0.3 T for the first 10 minutes and 60 Hz / 0.3 T for the next 20 minutes. The mixing temperature was 660℃ and the total stirring time was 30 minutes, thus obtaining the alloy composite material. (4) The alloy composite material obtained in step (3) was degassed and refined and then die-cast into standard specimens to obtain 0.1wt.%CNTs-ADC12 aluminum alloy composite material.

[0053] Example 3 (1) Raw material preparation: The total weight of ADC12 aluminum alloy is 10 kg: 4 kg for the low-temperature section and 6 kg for the high-temperature section. The modified CNTs added in Preparation Example 3 were 1.5 wt% : 150 g; (2) Melt preparation: 4 kg of ADC12 aluminum alloy was melted at 630℃ to obtain a cryogenic melt; 6 kg of ADC12 aluminum alloy was melted at 800℃ to obtain a high-temperature melt; (3) Preparation of composite materials: Modified CNTs were added to the low-temperature melt, and then mechanically stirred at a stirring rate of 700 rpm, while being ultrasonically treated at an ultrasonic frequency of 35 kHz for 20 min to obtain the low-temperature composite melt. High-temperature melt was injected into low-temperature composite melt at a rate of 8 kg / min, and electromagnetic stirring was started simultaneously. The working conditions were 40 Hz / 0.2 T for the first 10 minutes and 70 Hz / 0.4 T for the next 20 minutes. The mixing temperature was 680℃ and the total stirring time was 30 minutes, thus obtaining the alloy composite material. (4) The alloy composite material obtained in step (3) was degassed and refined and then die-cast into standard specimens to obtain 1.5wt.%CNTs-ADC12 aluminum alloy composite material.

[0054] Test Example 1 Scanning electron microscopy (SEM) analysis was performed on the fracture surfaces of the low-temperature composite melt in step (3) of Example 1, the 0.1 wt.% CNTs-ADC12 aluminum alloy composite material prepared in Example 1, and the ADC12 aluminum alloy raw material. The results are as follows: Figure 1-3 As shown.

[0055] Depend on Figure 1-3 From the content, we can know that Figure 1 The image shows the clusters of CNTs dispersed in the low-temperature composite melt after ultrasonication. It can be seen that the size of the CNT clusters after ultrasonic dispersion is reduced compared to the original size, and the dispersion uniformity is improved.

[0056] Figure 2 The fracture morphology of the 0.1 wt.% CNTs-ADC12 aluminum alloy composite material prepared in Example 1 is shown. Figure 3 The fracture morphology of ADC12 aluminum alloy raw material.

[0057] Depend on Figure 3 As can be seen from the content, the fracture morphology of ADC12 aluminum alloy raw material is composed of coarse dimples and cleavage steps. It is mainly brittle cleavage fracture with low crack propagation resistance and poor toughness. Figure 2 As can be seen from the content, after strengthening with 0.1wt.% CNTs, the fracture morphology of the 0.1wt.% CNTs-ADC12 aluminum alloy composite material prepared in Example 1 is composed of fine equiaxed dimples, which are interspersed with CNTs. It is mainly a ductile-brittle mixed fracture, with significantly improved crack propagation resistance and enhanced toughness.

[0058] Test Example 2 The performance of the carbon nanotube-reinforced ADC12 aluminum alloy composites prepared in Examples 1-3 was compared with that of the ADC12 aluminum alloy raw material. The performance test results are shown in Table 1.

[0059] Table 1

[0060] As shown in Table 1, the CNTs-ADC12 aluminum alloy composite materials produced in Examples 1-3 using the method of the present invention through stepwise melt mixing process, carbon nanotube (CNTs) surface modification and electromagnetic-mechanical synergistic control and other core technologies significantly surpass the traditional ADC12 aluminum alloy in terms of mechanical properties, thermal conductivity and industrial adaptability. They can be more widely used in the manufacture of high-performance lightweight components in the automotive, aerospace and other fields.

[0061] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0062] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0063] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing carbon nanotube-reinforced aluminum alloy composite materials, characterized in that, The preparation method includes the following steps: 1) Divide the aluminum alloy raw material into two parts: one part is melted into a low-temperature melt, and the other part is melted into a high-temperature melt; 2) Carbon nanotubes are mixed with a low-temperature melt to form a low-temperature composite melt; 3) Mix the high-temperature melt with the low-temperature composite melt, degas the mixed melt, refine it, and then die-cast it.

2. The preparation method according to claim 1, characterized in that, In step 1), the aluminum alloy raw material is of type ADC12.

3. The preparation method according to claim 1 or 2, characterized in that, In step 1), the low-temperature melt is melted at a temperature of 580℃-640℃, and its mass fraction in the aluminum alloy raw material is 30%-40%. The high-temperature melt is melted at a temperature of 760℃-860℃, and its mass fraction in the aluminum alloy raw material is 60%-70%.

4. The preparation method according to claim 1, characterized in that, In step 2), the amount of carbon nanotubes added is 0.1%-2.0% of the total weight of the aluminum alloy raw material.

5. The preparation method according to claim 1, characterized in that, In step 2), the mixing conditions include: mechanical stirring at a stirring rate of 300 rpm to 800 rpm for 5 min to 10 min, followed by ultrasonication at an ultrasonic frequency of 20 kHz to 40 kHz for 15 min to 20 min.

6. The preparation method according to claim 1, characterized in that, In step 2), the surface of the carbon nanotubes is modified with a coupling agent; Preferably, the coupling agent modification includes: dispersing carbon nanotubes in a coupling agent ethanol solution after acidification treatment, stirring the reaction for 2-4 hours, and removing the solvent to obtain carbon nanotubes modified with the coupling agent. More preferably, the coupling agent is a silane coupling agent and / or a titanate coupling agent.

7. The preparation method according to any one of claims 1-6, characterized in that, In step 3), the mass ratio of the high-temperature melt to the low-temperature composite melt is 2-4:

1.

8. The preparation method according to claim 5, characterized in that, In step 3), the mixing conditions include: adding the high-temperature melt to the low-temperature composite melt at a rate of 5 kg / min to 15 kg / min under the condition of a temperature of 650℃-680℃, while simultaneously performing electromagnetic stirring under the conditions of a magnetic field frequency of 20 Hz-100 Hz and a magnetic induction intensity of 0.1 T-0.5 T for a stirring time of 20 min-40 min; The direction of the electromagnetic stirring is opposite to the direction of the mechanical stirring in step 2) when mixing carbon nanotubes and low-temperature melt.

9. A carbon nanotube-reinforced aluminum alloy composite material, characterized in that, The carbon nanotube reinforced aluminum alloy composite material is prepared by the preparation method described in claims 1-8.

10. The application of a carbon nanotube-reinforced aluminum alloy composite material in the manufacture of high-performance lightweight components for the automotive and aerospace fields, characterized in that... The carbon nanotube-reinforced aluminum alloy composite material is the carbon nanotube-reinforced aluminum alloy composite material as described in claim 9.

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