CN113249686B - A kind of reinforcement modification method for casting aluminum-lithium matrix composites - Google Patents

Abstract

The invention relates to a reinforcement modification method for casting aluminum-lithium-based composite materials. The method is to use a turning device to make the reinforcement roll, and at the same time, the coating film material is uniformly deposited on the surface of the reinforcement by physical vapor deposition to form a uniform film layer. Then, the uniformly coated reinforcement is heat strengthened and ball milled to prepare a preform. After the aluminum-lithium alloy is smelted and refined, it is pressed into the prefabricated block and evenly stirred, and then poured to obtain a high-rigidity and high-strength aluminum-lithium-based composite material. During the physical vapor deposition process, the reinforcement is constantly flipped, and the rare earth coating can be evenly covered on the surface of the reinforcement instead of only covering the upper surface. The formed uniform surface coating can effectively solve the problem of the reaction between the reinforcement and the melt, and obviously hinder the agglomeration of reinforcement particles. Compared with the prior art, the method can fully exploit the strengthening potential of carbon nanotubes and graphene in casting aluminum-lithium-based composite materials, greatly improve the stiffness and strength of the aluminum-lithium alloy, and has simple process and low input cost.

Description

A kind of reinforcement modification method for casting aluminum-lithium matrix composites

technical field

The invention belongs to the technical field of preparation of aluminum-lithium alloys and composite materials, and particularly relates to a reinforcement modification method for casting aluminum-lithium-based composite materials.

Background technique

In recent years, with the continuous development of military, aviation and civil industrial technologies, the strength and stiffness requirements of materials have been continuously improved, and high Li content aluminum-lithium alloys have shown broad application prospects. Studies have shown that adding 1wt% of lithium to an aluminum alloy can increase the stiffness by about 6% and reduce the density by about 3%. However, the increase of lithium content brings problems such as high anisotropy and poor plasticity. At the same time, due to the high activity of lithium element, it is easy to be oxidized and burned, which has very high requirements on the quality of the melt. After a large number of experiments, it is found that the effective Li content does not exceed 3.2%, and the maximum possible stiffness of the Al-Li series alloy is 81GPa. If the stiffness of the aluminum alloy continues to increase, the composite material method should be considered.

It is known from semi-quantitative analysis that the elastic moduli of multiphase alloys are determined by the elastic moduli of their constituent phases and their volume fractions. As an advanced carbon material, carbon nanotubes have an elastic modulus of up to 1TPa, which is equivalent to the elastic modulus of diamond and about 5 times that of steel. It is different from other reinforcements for toughening and toughening. It plays an important role in composite materials. To the role of strengthening and toughening, it has become a hot spot for composite reinforcements. Graphene is one of the strongest materials known. It also has good toughness and can be bent. Graphene has a theoretical Young's modulus of 1.0TPa and an inherent tensile strength of 130GPa. In recent years, researchers have tried to add reinforcements such as graphene and carbon nanotubes to cast aluminum alloys by powder metallurgy. The powder metallurgy method can control the preparation temperature of the composite material to prevent excessive reaction of the alloy and the external reinforcing particles. However, Al-Li alloys with high Li content are not suitable for powder metallurgy forming due to their activity and easy oxidation. Sun Xiao and others from Shandong Binzhou Bohai Piston Co., Ltd. used gravity casting method to prepare Piston parts with complex shapes, but only press sintering is carried out in the preparation of preforms, and the reinforcement is directly exposed to the melt, which is not suitable for very active aluminum-lithium melts. Fan Guoqiang disclosed "a kind of graphene-enhanced Al-Si casting aluminum alloy and its preparation method" (publication number CN 111041287A), and directly smelting graphene and alloy in vacuum under the protection of argon, although there is a certain performance improvement, but large Some graphene will react with Al and fail, and the potential of graphene cannot be fully exploited. Zhang Min et al. disclosed "a graphene composite rare earth modified hypoeutectic Al-Si-Mg casting alloy and its preparation method" (publication number CN110512122A), which is only suitable for Al-Si-Mg series alloys. Ding Dehua et al. disclosed "Ultra-light and high elastic modulus carbon nanotube reinforced magnesium-lithium composite material and preparation method", the coating material used in this method is suitable for magnesium-lithium melt but not for aluminum-lithium melt, and ordinary The physical vapor deposition method has uneven coating and needs to be improved.

Compared with traditional aluminum alloys, the presence of very active metal element Li in aluminum-lithium alloys makes the preparation process more difficult. In addition to the reaction between C and Al to form Al ₄ C ₃ , carbon nanotubes and graphene are added to the aluminum-lithium alloy melt, and Li will react with C at high temperature to form Li ₂ C ₂ , which makes the carbon nanotubes and graphene more effective. The strengthening effect is not fully exerted. And with the increase of Li content, the reaction becomes more intense. The use of magnetron sputtering equipment to deposit large atoms of rare earth elements on the surface of carbon reinforcement particles can effectively protect them, but the commonly used magnetron sputtering equipment can only form coatings on a plane in a certain direction. Li Yangde et al. transformed the magnetron sputtering equipment, and disclosed "Physical Vapor Deposition Equipment and Physical Vapor Deposition Method" (publication number CN 107723675A), which increased the up-and-down vibration of the coated product, the inversion from the inside to the outside and along the predetermined direction. The rotating device, but the movement mode of up and down vibration makes the movement rate difficult to control, which is not conducive to nano-scale powder reinforcement coating. Therefore, the present invention takes the lead in transforming the magnetron sputtering equipment and adding a turning device, so that the reinforcement particles are continuously rolled during the phase deposition process, the movement rate is easy to control, the device transformation method is simple, and it is more suitable for the coating of nano-powders; in addition, the use of Ceramic material that withstands the high heat generated by the vapor deposition process and does not interfere with magnetic fields. The coating material uses rare earth elements that can effectively hinder the reaction between the carbon reinforcement and the aluminum-lithium melt as the target material, and uniformly coats the surface of the reinforcement to realize the dispersion and stable distribution of the fine carbon reinforcement in the aluminum-lithium melt. Effectively To explore the strengthening potential of carbon nanotubes and graphene, and greatly improve the elastic modulus and strength of the material.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a method for modifying the reinforcement of the cast aluminum-lithium-based composite material in view of the above-mentioned deficiencies in the prior art. In this method, a flipping device is designed and added to the magnetron sputtering equipment to improve the characteristic that magnetron sputtering can only perform phase deposition on a certain plane, and can perform uniform coating on the surface of the reinforcement. The coating material is made of large atomic rare earth elements, which can effectively protect the structural integrity of graphene and carbon nanotubes and are uniformly dispersed in the aluminum-lithium base.

The present invention utilizes a magnetron sputtering device with a flipping device added to perform uniform physical vapor deposition on the reinforcement. The reinforcement is placed in an inversion device made of non-conductive, high-temperature resistant ceramic materials, and the vapor phase of ionized Al ₂ Ce, Dy and La is uniformly deposited on the surface of the reinforcement to form a coating, and after the coating is completed, it is cooled to room temperature and Carry out heat treatment; make the surface-treated reinforcement into a prefabricated block, press the prefabricated block into the melt after refining in the smelting process and fully stir, and pour the melt to obtain a cast aluminum-lithium composite material strengthened by the modified reinforcement.

The object of the present invention can be realized through the following scheme:

In a first aspect, the present invention relates to a reinforcement modification method suitable for casting aluminum-lithium-based composite materials, the method comprising the following steps:

The reinforcing body is placed in a turning device and turned over, and at the same time, the coating film is bombarded by magnetron sputtering, and the generated ionized gas phase is deposited on the surface of the reinforcing body to form a uniform coating to obtain a modified reinforcing body.

As an embodiment of the present invention, the reinforcing body is one or two composite powders of graphene and carbon nanotubes.

As an embodiment of the present invention, the coating film is a mixed target of Al ₂ Ce, Dy and La with a weight ratio of 45-55:25-35:15-25.

As an embodiment of the present invention, the turning device is made of ceramic material; the rotational speed is controlled at 10-20 rad/min. The ceramic material is non-conductive and resistant to high temperatures.

As an embodiment of the present invention, the coating film is placed in a crucible and heated to 750-850° C. before bombarding the film with a magnetron sputtering electron beam; the bombardment time is 60-90 minutes.

As an embodiment of the present invention, the coated reinforcement is subjected to vacuum heat treatment, and the vacuum degree is 10 ^-3 to 10 ^-4 Pa; the heat treatment is to preheat and hold at a temperature of 200 to 250 ° C for 20-40 minutes; Incubate at 450～470℃ for 3～4h.

As an embodiment of the present invention, the reinforcement is cooled to room temperature before being placed in a vacuum furnace.

As an embodiment of the present invention, the heat-treated reinforcement and Al chips are mixed and ball-milled with 1:40-50 and 0.8-1.2% by mass of acidic aluminum phosphate to form a prefabricated block to obtain a modified reinforcement.

In the second aspect, the present invention also relates to an inversion device used in the aforementioned reinforcement modification method, the device includes a cathode, a ceramic inversion device, an anode, an air inlet, a vacuum pumping system, a high-voltage power supply, a vacuum chamber, a waiting enhance the object;

the ceramic turning device is located in the vacuum chamber;

The vacuum chamber is provided with an air inlet, and the vacuum chamber is also connected with a vacuum pumping system;

The object to be reinforced is located at the bottom of the ceramic flipping device;

The cathode is located in the ceramic inversion device, above the object to be reinforced;

The anode is located in the vacuum chamber, below the ceramic turning device, and below the object to be reinforced;

The cathode and anode are connected with a high voltage power supply.

In a third aspect, the present invention also relates to a method for preparing an aluminum-lithium-based composite material by utilizing the aforementioned modified reinforcement, the method comprising the following steps:

S1: Melt the aluminum-lithium-based components except Li, and then spread a mixed powder covering agent with a mass ratio of LiCl:LiF=3:1, add high-purity Li, and perform rotary injection of high-purity argon refining;

S2: mechanically stir the refined melt in an argon atmosphere, and press the prefabricated block into the melt after reducing the stirring rate when the melt temperature is 20-30°C above the solidus line; continue stirring for 15 After -25min, the reinforced aluminum-lithium-based composite material is obtained by pouring at 710-730 ℃; the prefabricated block is made by mixing the heat-treated modified reinforcement and Al chips at a ratio of 1:40-50 and adding 0.8-1.2% by mass. It is obtained by mixing and ball milling of acid aluminum phosphate.

In a fourth aspect, the present invention also relates to an aluminum-lithium-based composite material prepared according to the aforementioned preparation method. : 0.4-1.0%, Zr: 0.1-0.3%, Sc: 0.1-0.3%, Coated carbon nanotubes: 1.0-3.0%, Coated graphene: 0.1-0.5%, impurity elements not higher than 0.02%, the remainder The amount is Al.

The present invention firstly improves the magnetron sputtering equipment and adds a turning device made of ceramic material. Ceramic materials are suitable for improved devices for magnetron sputtering due to their high temperature resistance and non-magnetic properties. During the magnetron sputtering process, the device makes the carbon nanotubes and graphene of the reinforcement roll at a constant speed, and at the same time, the coating film materials Al ₂ Ce, Dy and La are uniformly deposited on the surface of the reinforcement by physical vapor deposition to form a uniform film layer. The turnover rate in the coating process should not be too high or too low, which is conducive to a more uniform coating; the coating time should not be too long or too short. Thickness will lead to a large mismatch with the aluminum matrix, causing stress concentration and even microcracks. Then, the uniformly coated reinforcement is heat strengthened and ball milled to prepare a preform. After the aluminum-lithium alloy is smelted and refined, it is pressed into the prefabricated block and evenly stirred, and then poured to obtain a high-rigidity and high-strength aluminum-lithium-based composite material. During the physical vapor deposition process, the inversion device forces the reinforcement to be turned continuously, so that the rare earth coating can be uniformly covered on the surface of the reinforcement instead of only covering the upper surface. Moreover, due to the particularity of the large atomic structure of the rare earth elements Dy and La used, the uniform surface coating formed can effectively solve the problem of the reaction between carbon nanotubes, graphene and the active Al-Li melt, and obviously hinder the reinforcement. Particle agglomeration. The method can fully explore the strengthening potential of carbon nanotubes and graphene in casting aluminum-lithium-based composite materials, greatly improve the stiffness and strength of aluminum-lithium alloys, the stiffness can reach 105GPa, the yield strength can reach 412MPa, and the process is simple and the investment cost is low. .

Compared with the prior art, the present invention has the following beneficial effects:

1. In the present invention, the magnetron sputtering equipment is improved, and a turning device made of ceramic material is added. The characteristics of the ceramic material can avoid interference to the magnetic field of physical vapor deposition, and can withstand high temperature, which can stably increase the Uniform physical vapor deposition of particles in all directions.

2. The device has the advantages of low cost, simple assembly, and easy control of the turnover rate, preventing the problem of uneven thickness of the coating caused by too high or too low movement speed.

3. When heat treating the coated reinforcement to enhance the bonding force, first preheat at low temperature to prevent the internal stress and strain caused by the different expansion rates of the film and the reinforcement directly under high temperature conditions.

4. The use of large atomic rare earth atoms Al ₂ Ce, Dy and La coating can effectively block carbon nanotubes and graphene from contacting the active Al-Li melt, which limits the reaction. And there is a certain limitation of agglomeration in the melt, so that the reinforcement is completely and uniformly distributed in the melt.

5. Due to the high Li content of the composite material involved in the present invention, and the addition of carbon nanotubes and graphene, the material density is lower than 2.5g/ ^m3 , and the elastic modulus can be as high as 95-105GPa, and the ultimate tensile strength is Above 550MPa, the elongation rate is 6%, and the comprehensive performance is far superior to ordinary aluminum-lithium alloys.

Description of drawings

Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings:

Fig. 1 is the schematic diagram of turning device;

The marks in the figure are as follows: 1, cathode; 2, ceramic turning device; 3, anode; 4, air inlet; 5, vacuum pumping system; 6, high voltage power supply; 7, vacuum chamber; 8, object to be strengthened.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, and provide detailed implementation manners and specific operation procedures, which will help those skilled in the art to further understand the present invention. It should be pointed out that the protection scope of the present invention is not limited to the following embodiments, and several adjustments and improvements made under the premise of the concept of the present invention all belong to the protection scope of the present invention.

Example 1

The present invention provides an inversion device, which includes a cathode 1, a ceramic inversion device 2, an anode 3, an air inlet 4, a vacuum pumping system 5, a high-voltage power supply 6, a vacuum chamber 7, and an object to be reinforced 8; the ceramic The turning device 2 is located in the vacuum chamber 7; the vacuum chamber 7 is provided with an air inlet 4, and the vacuum chamber 7 is also connected with the vacuum pumping system 5; the object to be reinforced 8 is located at the bottom of the ceramic turning device 2; the cathode 1 is located in the ceramic inversion device 2, above the object to be reinforced 8; the anode 3 is located in the vacuum chamber 7, below the ceramic inversion device 2, and below the object to be reinforced 8; the cathode 1, the anode 3 and the high-voltage power supply 6 connected.

The preparation steps of the prefabricated block reinforced cast aluminum-lithium-based composite are as follows:

Step 1. Put the carbon nanotube and graphene mixed reinforcement into the drum of the rotating device made of ceramic material, start the drum, and control the rotational speed to be 15r/min. Then, the mixed targets with Al ₂ Ce, Dy and La and 50, 30, and 20 parts by weight were placed in a crucible and heated to 800° C. The atoms were ionized by a low-pressure argon discharge, and the Al was bombarded with an electron beam. _2. The Ce, Dy and La targets were ionized and deposited on the surface of the tumbling carbon nanotubes and graphene to form a film. After 80 minutes, it was stopped, and the coating reinforcement was taken out when the temperature dropped to room temperature.

Step 2: Put the coated carbon nanotubes and graphene reinforcements into a vacuum furnace, preheat at 230°C for 30min, and then keep at 460°C for 3.5h, so that the film layer properly diffuses into the reinforcement to enhance the bonding force.

Step 3. The heat-treated reinforcement particles and Al chips are mixed and ball-milled into prefabricated blocks at a ratio of 1:50 and 1% by mass of acid aluminum phosphate.

Step 4: Smelting the aluminum-lithium base, the mass percentage of the designed alloy composition is: Li: 2.5%, Cu: 2.0%, Mg: 0.8%, Zr: 0.15%, Sc: 0.2%, and the carbon nanotubes strengthened by coating: 1.8%, coating-strengthened graphene: 0.4%, impurity elements not higher than 0.02%, and the balance is Al. After melting Cu, Mg, Zr, and Sc elements in the atmospheric environment, a covering agent is spread, and high-purity Li is added in an argon atmosphere, followed by refining.

Step 5. The refined melt is mechanically stirred under an argon atmosphere. When the melt temperature is 25°C above the solidus temperature, the stirring rate is reduced, and the prefabricated block is pressed into the melt, and the stirring is continued for about 20min. The carbon nanotube and graphene reinforced aluminum-lithium-based composite material can be obtained by casting at 720°C by controlling the temperature.

The density of the ultra-high stiffness Al-Li-based composite reinforced by the prefabricated block is 2.53 g/cm ³ and the elastic modulus is 101 GPa. After the solid solution and aging treatment, the tensile properties at room temperature are: yield strength 413MPa, tensile strength 572MPa, elongation 8.3%. The density of the composite material is determined by the Archimedes drainage method, the test samples and methods for tensile properties (yield strength, tensile strength and elongation) are in accordance with the national standard GB/T228.1-2010, the test samples for elastic modulus And the method is based on the national standard GB/T22315-2008, the same below.

Example 2

The preparation steps of the prefabricated block reinforced cast aluminum-lithium-based composite are as follows:

Step 1. Put the carbon nanotube and graphene mixed reinforcement into the drum of the rotating device made of ceramic material, start the drum, and control the rotational speed to be 10r/min. Subsequently, the mixed targets with the coating materials of Al ₂ Ce, Dy and La and 50, 30, 20 parts by weight were placed in a crucible and heated to 800° C. The atoms were ionized by a low-pressure argon discharge, and the Al was bombarded with an electron beam. _2. The Ce, Dy and La targets were ionized and deposited on the surface of the tumbling carbon nanotubes and graphene to form a film. After 60 minutes, it was stopped, and the coating reinforcement was taken out when the temperature dropped to room temperature.

Step 2: Put the coated carbon nanotubes and graphene reinforcements in a vacuum furnace, preheat at 200°C for 40 minutes, and then keep at 450°C for 3 hours, so that the film layer properly diffuses into the reinforcement to enhance the bonding force.

Step 3. The heat-treated reinforcement particles and Al chips are mixed and ball-milled into prefabricated blocks at a ratio of 1:40 and 1.2% by mass of stearic acid.

Step 4: Smelting the aluminum-lithium base, the mass percentages of the designed alloy components are: Li: 1.5%, Cu: 4.0%, Mg: 1.5%, Zr: 0.15%, Sc: 0.2%, and the carbon nanotubes strengthened by coating: 0.8%, coating-strengthened graphene: 0.3%, impurity elements not higher than 0.02%, and the balance is Al. After melting Cu, Mg, Zr, and Sc elements in the atmospheric environment, a covering agent is spread, and high-purity Li is added in an argon atmosphere, followed by refining.

Step 5. The refined melt is mechanically stirred under an argon atmosphere. When the melt temperature is 20°C above the solidus temperature, the stirring rate is reduced, and the prefabricated block is pressed into the melt, and the stirring is continued for about 20min. The carbon nanotubes and graphene reinforced aluminum-lithium-based composite materials can be obtained by casting at 710 °C by controlling the temperature.

The density of the ultra-high stiffness Al-Li-based composite reinforced by the prefabricated block is 2.63 g/cm ³ and the elastic modulus is 96 GPa. After the solid solution and aging treatment, the tensile properties at room temperature are: yield strength 408MPa, tensile strength 583MPa, elongation 7.5%.

Example 3

The preparation steps of the prefabricated block reinforced cast aluminum-lithium-based composite are as follows:

Step 1. Put the carbon nanotube and graphene mixed reinforcement into the drum of the rotating device made of ceramic material, start the drum, and control the rotational speed to be 20r/min. Then, the mixed targets with Al ₂ Ce, Dy and La and 50, 30, and 20 parts by weight were placed in a crucible and heated to 800° C. The atoms were ionized by a low-pressure argon discharge, and the Al was bombarded with an electron beam. ₂ The Ce, Dy and La targets are ionized and deposited on the surface of the tumbling carbon nanotubes and graphene to form a film, which can be stopped for 90 minutes, and the coating reinforcement can be taken out when the temperature drops to room temperature.

Step 2: Put the coated carbon nanotubes and graphene reinforcements into a vacuum furnace, preheat at 240°C for 30 minutes, and then keep at 470°C for 4 hours, so that the film layer properly diffuses into the reinforcement to enhance the bonding force.

Step 3: The heat-treated reinforcement particles and Al chips are mixed and ball-milled into prefabricated blocks at a ratio of 1:50 and 0.8% by mass of acid phosphate ester.

Step 4: Smelting the aluminum-lithium base, the mass percentages of the designed alloy components are: Li: 3.0%, Cu: 2.0%, Mg: 0.5%, Zr: 0.15%, Sc: 0.2%, and the carbon nanotubes strengthened by coating: 1.5%, coating-strengthened graphene: 0.4%, impurity elements not higher than 0.02%, and the balance is Al. After melting Cu, Mg, Zr, and Sc elements in the atmospheric environment, a covering agent is spread, and high-purity Li is added in an argon atmosphere, followed by refining.

Step 5. The refined melt is mechanically stirred under an argon atmosphere. When the melt temperature is 30°C above the solidus temperature, the stirring rate is reduced, and the prefabricated block is pressed into the melt, and the stirring is continued for about 20min. The carbon nanotube and graphene reinforced aluminum-lithium-based composite material can be obtained by casting at 720°C by controlling the temperature.

The density of the ultra-high stiffness Al-Li-based composite reinforced by the prefabricated block is 2.51 g/cm ³ and the elastic modulus is 105 GPa. After the solid solution and aging treatment, the tensile properties at room temperature are: yield strength 422MPa, tensile strength 554MPa, elongation 7.2%.

Comparative Example 1

This comparative example relates to a nano-scale mixed particle reinforced ultra-high-rigidity aluminum-lithium-rare-earth-based composite material. The mass percentage of each component of the composite material is the same as that in Example 1, and the preparation method is basically the same. The difference is that only ordinary The magnetron sputtering, pressed into preforms and added to the melt.

The measured room temperature tensile properties of the aluminum-lithium rare earth-based composite material after heat treatment are: yield strength 382MPa, tensile strength 486MPa, elongation 3.9%, and elastic modulus 86GPa.

The coating of carbon nanotubes and graphene that are only processed by conventional magnetron sputtering is uneven, and only covers the upper surface. After adding the melt, the uncoated area or the thin coated area is very easy to directly contact with the Al and Li of the melt. The reaction causes the nanoparticle structure to change and lose its strengthening effect, and it is easy to agglomerate and distribute unevenly, which leads to stress concentration during the stretching process, induces microcracks, and sharply reduces the elongation.

Comparative Example 2

This comparative example relates to a nano-scale mixed particle reinforced ultra-high-rigidity aluminum-lithium-rare-earth-based composite material. The mass percentage of each component of the composite material is the same as that of Example 2, and the preparation method is basically the same, the difference is that no magnetic control is performed. Sputtering, directly pressed into preforms and added to the melt.

The measured room temperature tensile properties of the aluminum-lithium rare earth-based composite material after heat treatment are: yield strength of 355 MPa, tensile strength of 423 MPa, elongation of 0.9 percent, and elastic modulus of 81 GPa.

Graphene and carbon nanotubes that are not coated by physical vapor deposition are directly exposed to the melt, and are very easy to directly react with Al and Li in the melt, resulting in changes in the nanoparticle structure, loss of strengthening effect, and easy agglomeration and uneven distribution. , resulting in stress concentration during the stretching process, inducing microcracks, and sharply reducing the elongation.

Comparative Example 3

This comparative example relates to a nano-scale mixed particle reinforced ultra-high-rigidity aluminum-lithium-rare-earth-based composite material. The mass percentage of each component of the composite material is the same as that in Example 2, and the preparation method is basically the same. The difference lies in the rotation speed control of the turning device. At 40rad/min, the coating time is 40min.

The measured tensile properties at room temperature of the aluminum-lithium rare earth-based composite material after heat treatment are: yield strength of 396 MPa, tensile strength of 543 MPa, elongation of 4.3 percent, and elastic modulus of 92 GPa.

Due to the high rotation speed of the turning device and the insufficient coating time, the thickness of the coating is thin and the protective effect is limited. This leads to uneven distribution of reinforcements, which reduces the strengthening effect and elongation.

Comparative Example 4

This comparative example relates to a nano-scale mixed particle reinforced ultra-high-rigidity aluminum-lithium-rare-earth-based composite material. The mass percentage of each component of the composite material is the same as that in Example 2, and the preparation method is basically the same. The difference lies in the rotation speed control of the turning device. At 50rad/min, the coating time is 120min.

The measured tensile properties at room temperature of the aluminum-lithium rare earth-based composite material after heat treatment are: yield 386MPa, tensile strength 497MPa, elongation 4.1%, and elastic modulus 90GPa. First, due to the excessively long coating time and the high turnover speed, the thickness of the rare earth coating on the surface of the reinforcement particles is extremely uneven, and some of the reinforcement particles fail.

Comparative Example 5

This comparative example relates to a nano-scale mixed particle reinforced ultra-high-rigidity aluminum-lithium-rare-earth-based composite material. The mass percentage of each component of the composite material is the same as that in Example 2, and the preparation method is basically the same. The difference lies in the rotation speed control of the turning device. At 5rad/min, the coating time is 40min.

The measured tensile properties at room temperature of the aluminum-lithium rare earth-based composite material after heat treatment are: yield 388MPa, tensile strength 489MPa, elongation 4.6%, and elastic modulus 89GPa. Too low turnover rate also results in uneven contact between the coating and the gas phase.

Comparative Example 6

This comparative example relates to an ultra-high stiffness aluminum-lithium-rare-earth-based composite material reinforced by nano-scale mixed particles. The mass percentage of each component of the composite material is the same as that in Example 1, and the preparation method is basically the same. The difference lies in the reinforcement in step 2. The body is placed in a vacuum furnace without preheating, and it is directly kept at high temperature.

The measured tensile properties at room temperature of the aluminum-lithium rare earth-based composite material after heat treatment are: yield 388MPa, tensile strength 484MPa, elongation 4.8%, and elastic modulus 91GPa. In this experiment, the reinforcement is preheated, which leads to a large stress due to the different expansion coefficients of the reinforcement and the outer metal when directly entering the high temperature, and then the strengthening effect is weakened.

Comparative Example 7

This comparative example relates to an ultra-high stiffness aluminum-lithium-rare-earth-based composite material reinforced by nano-scale mixed particles. The mass percentage of each component of the composite material is the same as that in Example 1, and the preparation method is basically the same. The difference lies in the reinforcement in step 2. The body is placed in a vacuum furnace with a preheating temperature of 150 °C.

The measured tensile properties at room temperature of the aluminum-lithium rare earth-based composite material after heat treatment are: yield 398MPa, tensile strength 533MPa, elongation 5.8%, and elastic modulus 94GPa.

Comparative Example 8

This comparative example relates to an ultra-high stiffness aluminum-lithium-rare-earth-based composite material reinforced by nano-scale mixed particles. The mass percentage of each component of the composite material is the same as that in Example 1, and the preparation method is basically the same. The difference lies in the reinforcement in step 2. The body is placed in a vacuum furnace with a preheating temperature of 320 °C.

The measured tensile properties at room temperature of the aluminum-lithium rare earth-based composite material after heat treatment are: yield 390MPa, tensile strength 506MPa, elongation 5.3%, and elastic modulus 95GPa.

Comparative Example 9

This comparative example relates to a nano-scale mixed particle reinforced ultra-high stiffness aluminum-lithium-rare-earth-based composite material. The mass percentage of each component of the composite material is the same as that in Example 1, and the preparation method is basically the same, except that the film in step 1 is different. The material is Al ₂ Ce.

The measured tensile properties at room temperature of the aluminum-lithium rare earth-based composite material after heat treatment are: yield 386MPa, tensile strength 508MPa, elongation 5.2%, and elastic modulus 88GPa.

Comparative Example 10

This comparative example relates to a nano-scale mixed particle reinforced ultra-high-rigidity aluminum-lithium-rare-earth-based composite material. The mass percentage of each component of the composite material is the same as that in Example 1, and the preparation method is basically the same. The device is made of cast iron material.

The measured tensile properties at room temperature of the aluminum-lithium rare earth-based composite material after heat treatment are: yield 376MPa, tensile strength 493MPa, elongation 3.3%, and elastic modulus 85GPa. Due to the use of the flipping equipment made of ordinary cast iron materials, it has a certain magnetic field interference during the magnetron sputtering process, resulting in disordered physical vapor deposition process and uneven coating.

The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above-mentioned specific embodiments, and those skilled in the art can make various variations or modifications within the scope of the claims, which do not affect the essential content of the present invention.

Claims (4)

1. a reinforcement modification method suitable for casting aluminum-lithium-based composite material, is characterized in that, described method comprises the following steps: The reinforcing body is placed in a turning device and turned over, and at the same time, the coating film is bombarded by magnetron sputtering, and the generated ionized gas phase is deposited on the surface of the reinforcing body to form a uniform coating to obtain a modified reinforcing body; The reinforcing body is one or two composite powders of graphene and carbon nanotubes; The coating material is a mixed target of Al ₂ Ce, Dy and La with a weight ratio of 45~55:25~35:15~25; The turning device is made of ceramic material; the speed is controlled at 10~20rad/min; Before bombarding the film with magnetron sputtering, place the coating film in a crucible and heat it to 750~850℃; the bombardment time is 60~90min; The coated reinforcement is subjected to vacuum heat treatment, and the vacuum degree is 10 ^-3 ~ 10 ^-4 MPa; the heat treatment is to first preheat and hold at a temperature of 200~250ºC for 20~40min; and then hold it at a temperature of 450~470ºC for 3~ 4h. 2. The reinforcement modification method suitable for casting aluminum-lithium-based composite materials according to claim 1 is characterized in that, the reinforcement and Al chips after heat treatment are mixed by 1:40~50 and then add 0.8~1.2% mass The percentage of acid aluminum phosphate is mixed and ball milled into preformed blocks. 3. A method for preparing an aluminum-lithium-based composite material using the modified reinforcement obtained by any one of claims 1-2, wherein the method comprises the following steps: S1: Melt the aluminum-lithium-based components except Li, and then spread a mixed powder covering agent with a mass ratio of LiCl:LiF=3:1, add high-purity Li, and perform rotary injection of high-purity argon refining; S2: The refined melt is mechanically stirred under an argon atmosphere, and the prefabricated block is pressed into the melt after reducing the stirring rate when the melt temperature is 20~30ºC above the solidus line; continue stirring for 15- After 25 minutes, the reinforced aluminum-lithium-based composite material is obtained by pouring at 710-730ºC; the prefabricated block is made by mixing the heat-treated modified reinforcement and Al chips at 1:40-50 and adding 0.8-1.2% by mass of acidic phosphoric acid Aluminium is produced by mixing ball milling. 4. an aluminum-lithium-based composite material prepared according to the method of claim 3, wherein the mass percentage of the composition of the aluminum-lithium-based composite material is: Li: 1.5~3.0%, Cu: 1.0~3.0%, Mg: 0.4~1.0%, Zr: 0.1~0.3%, Sc: 0.1~0.3 %, coating-strengthened carbon nanotubes: 1.0-3.0%, coating-strengthening graphene: 0.1-0.5%, impurity elements not higher than 0.02 %, the remainder is Al.

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