CN113249686B - Method for modifying reinforcement for casting aluminum-lithium-based composite material - Google Patents

Method for modifying reinforcement for casting aluminum-lithium-based composite material Download PDF

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CN113249686B
CN113249686B CN202110534854.8A CN202110534854A CN113249686B CN 113249686 B CN113249686 B CN 113249686B CN 202110534854 A CN202110534854 A CN 202110534854A CN 113249686 B CN113249686 B CN 113249686B
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reinforcement
aluminum
lithium
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CN113249686A (en
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张晋硕
张亮
吴国华
刘文才
张小龙
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Shanghai Jiaotong University
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
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    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/14—Metallic material, boron or silicon
    • C23C14/18—Metallic material, boron or silicon on other inorganic substrates
    • C23C14/185—Metallic material, boron or silicon on other inorganic substrates by cathodic sputtering
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22C1/00—Making non-ferrous alloys
    • C22C1/10—Alloys containing non-metals
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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/10—Alloys containing non-metals
    • C22C1/1036—Alloys containing non-metals starting from a melt
    • C22C1/1047—Alloys containing non-metals starting from a melt by mixing and casting liquid metal matrix composites
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    • C22C21/00—Alloys based on aluminium
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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C26/00—Alloys containing diamond or cubic or wurtzitic boron nitride, fullerenes or carbon nanotubes
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/223—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating specially adapted for coating particles
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/35—Sputtering by application of a magnetic field, e.g. magnetron sputtering
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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22C26/00—Alloys containing diamond or cubic or wurtzitic boron nitride, fullerenes or carbon nanotubes
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Abstract

The invention relates to a method for modifying a reinforcement for casting an aluminum-lithium-based composite material. The method is characterized in that a turnover device is utilized to roll the reinforcement, and a coating film is uniformly deposited on the surface of the reinforcement through physical vapor deposition to form a uniform film. And then heating, strengthening and ball-milling the uniformly coated reinforcement to prepare a prefabricated block. After the aluminum lithium alloy is smelted and refined, the aluminum lithium alloy is pressed into the prefabricated block and then is uniformly stirred, and then the aluminum lithium alloy composite material with high rigidity and high strength is obtained by casting. In the physical vapor deposition process, the reinforcement is continuously turned over, the rare earth coating can be uniformly covered on the surface of the reinforcement instead of only on the upper surface, and the formed uniform surface coating can effectively solve the problem of the reaction between the reinforcement and a melt and obviously prevent the particles of the reinforcement from agglomerating. Compared with the prior art, the method can fully explore the reinforcing potential of the carbon nano tube and the graphene in casting the aluminum-lithium-based composite material, greatly improves the rigidity and the strength of the aluminum-lithium alloy, and has the advantages of simple process and low investment cost.

Description

Method for modifying reinforcement for casting aluminum-lithium-based composite material
Technical Field
The invention belongs to the technical field of preparation of aluminum lithium alloy and composite materials, and particularly relates to a reinforcement modification method for casting an aluminum lithium-based composite material.
Background
In recent years, with the continuous development of military, aviation and civil industrial technologies, the requirements on the strength and rigidity of materials are continuously improved, and the high-Li-content aluminum-lithium alloy shows wide application prospects. Studies have shown that adding 1 wt% lithium to an aluminum alloy increases stiffness by about 6% and decreases density by about 3%. However, the increase of the lithium content brings about the problems of high anisotropy, poor plasticity and the like, and simultaneously, the high activity of the lithium element causes the easy oxidation and burning loss, and has very high requirements on the melt quality. A large number of experiments prove that the effective Li content is not more than 3.2 percent, the maximum possible rigidity of the Al-Li series alloy is 81GPa, and a composite material mode is considered if the rigidity of the aluminum alloy is continuously improved.
Semi-quantitative analysis it is known that the elastic modulus of a multi-phase alloy is determined by the elastic modulus of its constituent phases and their volume fractions. The carbon nano tube is used as an advanced carbon material, the elastic modulus of the carbon nano tube can reach 1TPa, is equivalent to that of diamond and is about 5 times of that of steel, and the carbon nano tube is different from other reinforcements in reinforcing and toughening, plays a role in reinforcing and toughening in a composite material and becomes a hot spot of a reinforcement of the composite material. Graphene is one of the materials with the highest known strength, has good toughness and can be bent, the theoretical Young modulus of the graphene reaches 1.0TPa, and the inherent tensile strength is 130 GPa. In recent years, researchers have attempted 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 and prevent the excessive reaction of the alloy and the external reinforced particles. However, the Al-Li alloy with high Li content is not suitable for being formed by powder metallurgy due to the activity and the easy oxidation. Piston parts with complex shapes can be prepared by a gravity casting method in research on gravity casting ceramic fiber local reinforced aluminum alloy pistons (internal combustion engine and accessories, 2-3 years 2010 and 19-22 pages) of Sunxiao et al of Bohai sea piston GmbH, Shandong Binshinan, but a prefabricated part is prepared only by pressing and sintering, and a reinforcement body is directly exposed in a melt and is not suitable for a very active aluminum-lithium melt. The Van Guo strongly discloses a graphene reinforced Al-Si cast aluminum alloy and a preparation method thereof (publication No. CN 111041287A), graphene and the alloy are directly subjected to vacuum melting under the protection of argon, although the performance is improved to a certain extent, most of graphene reacts with Al to lose efficacy, and the potential of the graphene cannot be fully explored. Zhangmin et Al disclose a graphene composite rare earth modified hypoeutectic Al-Si-Mg casting alloy and a preparation method thereof (publication No. CN110512122A), which is only suitable for Al-Si-Mg series alloys. Tdingehua et al disclose an ultralight high elastic modulus carbon nanotube reinforced magnesium lithium composite material and a preparation method, the coating material used by the method is suitable for magnesium lithium melt but not for aluminum lithium melt, and the common physical vapor deposition method has uneven coating and needs improvement.
Compared with the traditional aluminum alloy, the aluminum lithium alloy has very active metalThe element Li, makes the preparation process more difficult. Except that C reacts with Al to form Al4C3Adding carbon nano tube and graphene into an aluminum-lithium alloy melt, and reacting Li with C at high temperature to generate Li2C2And the strengthening effect of the carbon nano tube and the graphene cannot be fully exerted. And the reaction becomes more intense as the Li content increases. The large-atom rare earth elements are deposited on the surfaces of the carbon reinforcement particles by utilizing magnetron sputtering equipment to play an effective protection role, but the common magnetron sputtering equipment can only form a coating film on a plane in a certain direction. Li Yangde et al have disclosed physical vapor deposition equipment and physical vapor deposition method (publication No. CN 107723675A), and added with a device for making the coated product generate up-and-down vibration, turning from inside to outside and rotation along a predetermined direction, but the motion mode of up-and-down vibration makes the motion rate difficult to control, and is not beneficial to coating nano-scale powder reinforcement. Therefore, the invention firstly modifies the magnetron sputtering equipment and adds the turnover device, so that the particles of the reinforcement body continuously roll in the phase deposition process, the movement rate is convenient to control, the modification method of the device is simple, and the device is more suitable for coating the nano powder; in addition, the ceramic material can bear a large amount of heat generated in the vapor deposition process and cannot generate interference on a magnetic field. The coating material uses rare earth elements which can effectively hinder the reaction of the carbon reinforcement and the aluminum lithium melt as a target material, and the surface of the reinforcement is uniformly coated with a film, so that the fine carbon reinforcement is dispersed and stably distributed in the aluminum lithium melt, the reinforcement potential of the carbon nano tube and the graphene is effectively explored, and the elastic modulus and the strength of the material are greatly improved.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for modifying a reinforcement for a cast aluminum-lithium based composite material aiming at the defects in the prior art. The method firstly designs a turning device to be added into the magnetron sputtering equipment so as to improve the characteristic that magnetron sputtering can only carry out phase deposition on a certain plane and carry out uniform film coating on the surface of the reinforcement. The coating material adopts large-atom rare earth elements, can effectively protect the structural integrity of graphene and carbon nanotubes, and is uniformly dispersed in an aluminum-lithium matrix.
The invention utilizes the magnetron sputtering equipment added with the turning device to carry out uniform physical vapor deposition on the reinforcement. Placing the reinforcement body in a turning device made of non-conductive high-temperature-resistant ceramic material to turn over, and ionizing Al2Ce. Uniformly depositing Dy and La gas phase on the surface of the reinforcement to form a coating, cooling to room temperature after the coating is finished, and carrying out heat treatment; and preparing the reinforcement subjected to surface treatment into a prefabricated block, pressing the prefabricated block into a melt after refining in the smelting process, fully stirring, and pouring the melt to obtain the modified reinforcement reinforced cast aluminum-lithium composite material.
The purpose of the invention can be realized by the following scheme:
In a first aspect, the present invention relates to a method for modifying a reinforcement suitable for use in casting a lithium aluminum matrix composite, the method comprising the steps of:
and (3) placing the reinforcement body in a turnover device for turnover, bombarding the coating film material by utilizing magnetron sputtering, and depositing the generated ionized gas phase on the surface of the reinforcement body to form a uniform coating to obtain the modified reinforcement body.
As an embodiment of the present invention, the reinforcement is one or two composite powders of graphene and carbon nanotubes.
In one embodiment of the invention, the coating film material is Al with the weight ratio of 45-55: 25-35: 15-252Ce. Dy and La mixed target material.
As an embodiment of the present invention, the turning device is made of a ceramic material; the rotating speed is controlled to be 10 to 20 rad/min. The ceramic material is non-conductive and high temperature resistant.
As an embodiment of the invention, before bombarding the film material by magnetron sputtering electron beams, the film material of the coating layer is firstly placed in a crucible and heated to 750-850 ℃; the bombardment time is 60-90 min.
As an embodiment of the invention, the reinforcement after coating is subjected to vacuum heat treatment with a vacuum degree of 10-3～10-4Pa; the heat treatment is to preheat and preserve heat for 20-40min at the temperature of 200-250 ℃; then 450 And preserving the heat for 3-4 hours at the temperature of 470 ℃.
As an embodiment of the invention, the reinforcement is cooled to room temperature prior to being placed in the vacuum furnace.
According to one embodiment of the invention, the reinforcement body and the Al scrap after heat treatment are mixed and ball-milled into a precast block according to the mass percent of 1: 40-50 and 0.8-1.2% of acidic aluminum phosphate, so as to obtain the modified reinforcement body.
In a second aspect, the invention also relates to a turnover device used in the reinforcement modification method, wherein the device comprises a cathode, a ceramic turnover device, an anode, an air inlet, a vacuum pumping system, a high-voltage power supply, a vacuum chamber and an object to be reinforced;
the ceramic turnover device is positioned in the vacuum chamber;
the vacuum chamber is provided with an air inlet and is also connected with a vacuum pumping system;
the object to be enhanced is positioned at the bottom of the ceramic turnover device;
the cathode is positioned in the ceramic turnover device and above the object to be reinforced;
the anode is positioned in the vacuum chamber, below the ceramic turnover device and below the object to be enhanced;
the cathode and the 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 using the modified reinforcement, which comprises the following steps:
S1: melting the components except Li based on aluminum and lithium, then spreading a mixed powder covering agent with the mass ratio of LiCl to LiF of 3:1, adding high-purity Li, and carrying out rotary blowing high-purity argon refining;
s2: mechanically stirring the refined melt in an argon atmosphere, and pressing the precast block into the melt after the stirring rate is reduced when the temperature of the melt is 20-30 ℃ above the solidus line; continuously stirring for 15-25min, and pouring at 710-730 ℃ to obtain a reinforced lithium-aluminum matrix composite; the precast block is prepared by mixing the modified reinforcement after heat treatment and Al chips according to the proportion of 1: 40-50, adding 0.8-1.2% of acidic aluminum phosphate by mass, mixing and ball-milling.
In a fourth aspect, the invention also relates to an aluminum lithium-based composite material prepared by the preparation method, wherein the aluminum lithium-based composite material comprises the following components in percentage by mass: li: 1.5 to 3.0%, Cu: 1.0-3.0%, Mg: 0.4-1.0%, Zr: 0.1-0.3%, Sc: 0.1-0.3%, carbon nanotube coated with film: 1.0-3.0%, coated graphene: 0.1-0.5%, impurity elements not higher than 0.02%, and the balance of Al.
The invention firstly improves the magnetron sputtering equipment and adds a turnover device made of ceramic materials. The ceramic material is suitable for the improved device of magnetron sputtering by virtue of the characteristics of high temperature resistance and non-magnetism. In the magnetron sputtering process, the device is utilized to roll the enhanced carbon nano tube and the graphene at a constant speed, and simultaneously, the coating material Al is coated 2Ce. Dy and La are uniformly subjected to physical vapor deposition on the surface of the reinforcement to form a uniform film layer. The turnover rate in the plating process is not too high or too low, which is beneficial to the uniformity of the plating; the film coating time is not suitable to be too long or too short, the protective effect of the thin film layer is weakened due to the too short film coating time, and the large mismatching degree with the aluminum substrate is caused due to the too thick film layer due to the too long film coating time, so that stress concentration and even microcracks are caused. And then heating and strengthening the uniformly coated reinforcement and performing ball milling to prepare a precast block. After the aluminum lithium alloy is smelted and refined, the aluminum lithium alloy is pressed into the precast block and then is uniformly stirred, and then the aluminum lithium base composite material with high rigidity and high strength is obtained by casting. In the physical vapor deposition process, the turnover device forces the reinforcement to turn over continuously, and the rare earth coating can be uniformly covered on the surface of the reinforcement instead of only the upper surface. And due to the particularity of large atomic structures of the rare earth elements Dy and La, the formed uniform surface coating can effectively solve the problem of reaction of the carbon nano tube, the graphene and the active Al-Li melt and obviously hinder the agglomeration of reinforcement particles. The method can fully explore the reinforcing potential of the carbon nano tube and the graphene in casting the aluminum-lithium-based composite material, greatly improves the rigidity and the strength of the aluminum-lithium alloy, and has the advantages of rigidity reaching 105GPa, yield strength reaching 412MPa, simple process and low investment cost.
Compared with the prior art, the invention has the following beneficial effects:
1. in the invention, the magnetron sputtering equipment is improved, the turning device made of the ceramic material is added, the characteristics of the ceramic material can avoid the interference on the magnetic field of physical vapor deposition, and the ceramic material can bear high temperature and can stably and uniformly carry out the physical vapor deposition on the reinforced particles in all directions.
2. The device has low cost and simple assembly, and the turnover rate is easy to control, thereby preventing the problem of uneven plating thickness caused by overhigh or overlow motion rate.
3. When the heat treatment is carried out on the plated reinforcement to enhance the bonding force, the reinforcement is preheated at low temperature to prevent internal stress strain caused by the difference of the expansion rates of the film material and the reinforcement under the high-temperature condition.
4. Using macroatomic rare earth atoms Al2Ce. Dy and La are coated to effectively prevent the carbon nano tube and the graphene from contacting with the active Al-Li melt, so that the reaction is limited. And has certain agglomeration limiting function in the melt, so that the reinforcing bodies are completely and uniformly distributed in the melt.
5. The composite material has high Li content, and the addition of the carbon nano tube and the graphene enables the density of the material to be lower than 2.5g/m 3Meanwhile, the elastic modulus can reach 95-105 GPa, the ultimate tensile strength reaches more than 550MPa, the elongation rate reaches 6%, and the comprehensive performance is far superior to that of the common aluminum-lithium alloy.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a schematic view of a flipping mechanism;
the figures are labeled as follows: 1. a cathode; 2. a ceramic turnover device; 3. an anode; 4. an air inlet; 5. a vacuum pumping system; 6. a high voltage power supply; 7. a vacuum chamber; 8. the object to be enhanced.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments. The following examples, which are set forth to provide a detailed description of the invention and a detailed description of the operation, will help those skilled in the art to further understand the present invention. It should be noted that the scope of the present invention is not limited to the following embodiments, and that several modifications and improvements made on the premise of the idea of the present invention belong to the scope of the present invention.
Example 1
The invention provides a turnover device, which comprises a cathode 1, a ceramic turnover 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 enhanced 8; the ceramic turnover device 2 is positioned 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 a vacuum pumping system 5; the object 8 to be enhanced is positioned at the bottom of the ceramic turnover device 2; the cathode 1 is positioned in the ceramic turnover device 2 and above an object 8 to be enhanced; the anode 3 is positioned in the vacuum chamber 7, below the ceramic turnover device 2 and below the object to be reinforced 8; the cathode 1 and the anode 3 are connected with a high-voltage power supply 6.
The preparation steps of the precast block reinforced cast aluminum-lithium based composite material are as follows:
putting the carbon nano tube and graphene mixed reinforcement into a roller of a rotating device made of ceramic materials, starting the roller, and controlling the rotating speed to be 15 r/min. Then the coating film material is Al2Ce. Dy and La, 50, 30 and 20 parts by weight of mixed target material are placed in a crucible to be heated to 800 ℃, atoms are ionized by low-pressure argon discharge, and Al is bombarded by electron beams2Ce. And ionizing Dy and La targets, depositing the Dy and La targets on the surfaces of the rolled carbon nanotubes and graphene to form a film, continuing for 80min, stopping, and taking out the coating reinforcement when the temperature is reduced to room temperature.
And secondly, preheating the coated carbon nano tube and the graphene reinforcement body in a vacuum furnace at 230 ℃ for 30min, and then preserving heat at 460 ℃ for 3.5h to ensure that the film layer is properly diffused into the reinforcement body to reinforce the bonding force.
And step three, mixing and ball-milling the heat-treated reinforcing body particles and Al scraps according to the weight ratio of 1:50 and 1% of acidic aluminum phosphate to form a precast block.
Step four, smelting the aluminum lithium base, and designing the alloy components in percentage by mass as follows: li: 2.5%, Cu: 2.0%, Mg: 0.8%, Zr: 0.15%, Sc: 0.2%, coating-strengthened carbon nanotube: 1.8%, coating-strengthened graphene: 0.4 percent, impurity elements not higher than 0.02 percent and the balance of Al. After Cu, Mg, Zr and Sc elements are melted in the atmospheric environment, a covering agent is spread, high-purity Li is added in the argon atmosphere, and then refining is carried out.
And step five, mechanically stirring the refined melt in an argon atmosphere, reducing the stirring speed when the temperature of the melt is 25 ℃ above the solidus temperature, pressing the prefabricated block into the melt, and continuously stirring for about 20 min. And controlling the temperature to be 720 ℃ and pouring to obtain the carbon nano tube and graphene reinforced aluminum-lithium based composite material.
The density of the super-high rigidity aluminum lithium-based composite material reinforced by the precast block is 2.53g/cm3The elastic modulus was 101 GPa. After the solution treatment in aging treatment, the normal temperature tensile property is as follows: the yield strength is 413MPa, the tensile strength is 572MPa, and the elongation is 8.3%. The density of the composite material is measured by an Archimedes drainage method, the test sample and the method for tensile properties (yield strength, tensile strength and elongation) are according to the national standard GB/T228.1-2010, and the test sample and the method for elastic modulus are according to the national standard GB/T22315-2008, the same below.
Example 2
The preparation method of the precast block reinforced cast aluminum-lithium based composite material comprises the following steps:
step one, putting the carbon nano tube and graphene mixed reinforcement into a roller of a rotating device made of ceramic materials, starting the roller, and controlling the rotating speed to be 10 r/min. Then the coating film material is Al2Ce. Dy and La, 50, 30 and 20 parts by weight of mixed target material are placed in a crucible to be heated to 800 ℃, atoms are ionized by low-pressure argon discharge, and Al is bombarded by electron beams 2Ce. And ionizing Dy and La targets, depositing the Dy and La targets on the surfaces of the rolled carbon nanotubes and graphene to form a film, stopping the film after the film lasts for 60min, and taking out the film-coated reinforcement when the temperature is reduced to room temperature.
And secondly, preheating the coated carbon nano tube and the graphene reinforcement body in a vacuum furnace at 200 ℃ for 40min, and then preserving heat at 450 ℃ for 3h to ensure that the film layer is properly diffused into the reinforcement body to reinforce the bonding force.
Step three, mixing and ball-milling the heat-treated reinforcing body particles and Al scraps according to the mass percent of 1:40 and 1.2% of stearic acid to form a prefabricated block.
Step four, smelting the aluminum lithium base, and designing the mass percentage of alloy components as follows: li: 1.5%, Cu: 4.0%, Mg: 1.5%, Zr: 0.15%, Sc: 0.2%, coating-strengthened carbon nanotube: 0.8%, coating-strengthened graphene: 0.3 percent, impurity elements not higher than 0.02 percent and the balance of Al. After Cu, Mg, Zr and Sc elements are melted in the atmospheric environment, a covering agent is spread, high-purity Li is added in the argon atmosphere, and then refining is carried out.
And step five, mechanically stirring the refined melt in an argon atmosphere, reducing the stirring speed when the temperature of the melt is 20 ℃ above the solidus temperature, pressing the prefabricated block into the melt, and continuously stirring for about 20 min. And (3) pouring at the temperature of 710 ℃ to obtain the carbon nano tube and graphene reinforced aluminum-lithium based composite material.
The density of the precast block reinforced ultra-high rigidity aluminum-lithium based composite material is 2.63g/cm3The elastic modulus was 96 GPa. After the solution treatment in aging treatment, the normal temperature tensile property is as follows: the yield strength is 408MPa, the tensile strength is 583MPa, and the elongation is 7.5 percent.
Example 3
The preparation method of the precast block reinforced cast aluminum-lithium based composite material comprises the following steps:
step one, putting the carbon nano tube and graphene mixed reinforcement into a roller of a rotating device made of ceramic materials, starting the roller, and controlling the rotating speed to be 20 r/min. Then the coating film material is Al2Ce. Dy and La, 50, 30 and 20 parts by weight of mixed target material are placed in a crucible to be heated to 800 ℃, atoms are ionized by low-pressure argon discharge, and Al is bombarded by electron beams2Ce. And (3) ionizing the Dy and La target materials, depositing the Dy and La target materials on the surfaces of the rolled carbon nano tubes and the graphene to form a film, stopping the film for 90min, and taking out the film-coating reinforcement body when the temperature is reduced to room temperature.
And secondly, putting the coated carbon nano tube and the graphene reinforcement into a vacuum furnace, preheating for 30min at 240 ℃, and then preserving heat for 4h at 470 ℃ to ensure that the film layer is properly diffused into the reinforcement to reinforce the bonding force.
And step three, mixing and ball-milling the heat-treated reinforcing body particles and Al scraps according to the mass percent of 1:50 and 0.8% of acid phosphate into a precast block.
Step four, smelting the aluminum lithium base, and designing the mass percentage of alloy components as follows: li: 3.0%, Cu: 2.0%, Mg: 0.5%, Zr: 0.15%, Sc: 0.2%, coating-strengthened carbon nanotube: 1.5%, coating-strengthened graphene: 0.4 percent, impurity elements not higher than 0.02 percent and the balance of Al. After Cu, Mg, Zr and Sc elements are melted in the atmospheric environment, a covering agent is spread, high-purity Li is added in the argon atmosphere, and then refining is carried out.
And step five, mechanically stirring the refined melt in an argon atmosphere, reducing the stirring speed when the temperature of the melt is 30 ℃ above the solidus temperature, pressing the prefabricated block into the melt, and continuously stirring for about 20 min. And controlling the temperature to be 720 ℃ and pouring to obtain the carbon nano tube and graphene reinforced aluminum-lithium based composite material.
The density of the super-high rigidity aluminum lithium-based composite material reinforced by the precast block is 2.51g/cm3The elastic modulus was 105 GPa. After the solution treatment in aging treatment, the normal temperature tensile property is as follows: the yield strength is 422MPa, the tensile strength is 554MPa, and the elongation is 7.2 percent.
Comparative example 1
The comparative example relates to a nanoscale mixed particle reinforced ultra-high rigidity aluminum-lithium rare earth-based composite material, the mass percentages of the components of the composite material are the same as those in example 1, the preparation method is basically the same, and the difference is that only ordinary magnetron sputtering is carried out, and the components are added into a melt after being pressed into a prefabricated block.
The tensile property at room temperature measured after the aluminum-lithium-rare earth-based composite material is subjected to heat treatment is as follows: yield strength 382MPa, tensile strength 486MPa, elongation 3.9 percent and elastic modulus 86 GPa.
The carbon nano tube and graphene which are only subjected to conventional magnetron sputtering treatment are not uniform in coating, only cover the upper surface, and after the melt is added, the non-coated area or the thin coated area is very easy to directly contact and react with Al and Li of the melt, so that the structure of the nano particles is changed, the strengthening effect is lost, the nano particles are easy to agglomerate and distribute unevenly, stress concentration is caused in the stretching process, microcracks are induced, and the elongation is reduced rapidly.
Comparative example 2
The comparative example relates to a nanoscale mixed particle reinforced ultra-high rigidity aluminum-lithium-rare earth-based composite material, the mass percentages of the components of the composite material are the same as those of the example 2, the preparation method is basically the same, and the difference is that magnetron sputtering is not carried out, and the components are directly pressed into a precast block and then added into a melt.
The tensile property at room temperature measured after the aluminum-lithium-rare earth-based composite material is subjected to heat treatment is as follows: 355MPa of yield strength, 423MPa of tensile strength, 0.9 percent of elongation and 81GPa of elastic modulus.
The graphene and the carbon nano tube which are not subjected to physical vapor deposition coating are directly exposed in the melt and are very easy to directly contact and react with Al and Li of the melt, so that the structure of the nano particles is changed, the strengthening effect is lost, the nano particles are easy to agglomerate and are unevenly distributed, stress concentration is caused in the stretching process, microcracks are induced, and the elongation is sharply reduced.
Comparative example 3
The comparative example relates to a nanoscale mixed particle reinforced ultra-high rigidity aluminum-lithium-rare earth matrix composite material, the mass percentages of the components of the composite material are the same as those of the composite material in example 2, and the preparation method is basically the same, except that the rotating speed of a turnover device is controlled at 40rad/min, and the coating time is 40 min.
The tensile property at room temperature measured after the aluminum-lithium-rare earth-based composite material is subjected to heat treatment is as follows: the yield strength is 396MPa, the tensile strength is 543MPa, the elongation is 4.3 percent, and the elastic modulus is 92 GPa.
Because the rotating speed of the turnover device is too high, the coating time is not enough, the coating thickness is thin, the protection effect is limited, and the coating is easy to damage after contacting with the melt, so that part of particles are exposed in the melt, and the exposed particles of the reinforcement are agglomerated, the distribution of the reinforcement is uneven, and the reinforcement effect and the elongation are reduced.
Comparative example 4
The comparative example relates to a nanoscale mixed particle reinforced ultra-high rigidity aluminum-lithium-rare earth matrix composite material, the mass percentages of the components of the composite material are the same as those of the composite material in example 2, and the preparation method is basically the same, except that the rotating speed of a turnover device is controlled at 50rad/min, and the coating time is 120 min.
The tensile property at room temperature measured after the aluminum-lithium-rare earth-based composite material is subjected to heat treatment is as follows: yield of 386MPa, tensile strength of 497MPa, elongation of 4.1 percent and elastic modulus of 90 GPa. Firstly, the film coating time is too long and the turnover speed is high, so that the thickness of the rare earth coating on the surfaces of the particles of the reinforcement is extremely uneven, and partial particles of the reinforcement lose effectiveness.
Comparative example 5
The comparative example relates to a nanoscale mixed particle reinforced ultra-high rigidity aluminum-lithium rare earth-based composite material, the mass percentages of the components of the composite material are the same as those in example 2, and the preparation method is basically the same, except that the rotating speed of a turnover device is controlled at 5rad/min, and the coating time is 40 min.
The tensile property at room temperature measured after the aluminum-lithium-rare earth-based composite material is subjected to heat treatment is as follows: yield 388MPa, tensile strength 489MPa, elongation 4.6 percent and elastic modulus 89 GPa. Too low a turnover rate also results in uneven contact of the coating with the gas phase.
Comparative example 6
The comparative example relates to a nanoscale mixed particle reinforced ultra-high rigidity aluminum-lithium-rare earth-based composite material, the mass percentages of the components of the composite material are the same as those of the composite material in the example 1, and the preparation method is basically the same, except that in the second step, the reinforcement body is placed in a vacuum furnace without preheating, and is directly subjected to high-temperature heat preservation.
The tensile property at room temperature measured after the aluminum-lithium-rare earth-based composite material is subjected to heat treatment is as follows: yield 388MPa, tensile strength 484MPa, elongation 4.8 percent and elastic modulus 91 GPa. In the experiment, the reinforcement is subjected to preheating treatment, so that when the reinforcement directly enters high temperature, the metal expansion coefficients of the reinforcement and the outer layer are different, and larger stress is generated, and the reinforcement effect is weakened.
Comparative example 7
The comparative example relates to a nanoscale mixed particle reinforced ultra-high rigidity aluminum-lithium rare earth based composite material, the mass percentages of the components of the composite material are the same as those of the composite material in example 1, and the preparation method is basically the same, except that the reinforcing body in the second step is placed in a vacuum furnace for preheating at the temperature of 150 ℃.
The tensile property at room temperature measured after the aluminum-lithium-rare earth-based composite material is subjected to heat treatment is as follows: yield 398MPa, tensile strength 533MPa, elongation 5.8 percent and elastic modulus 94 GPa.
Comparative example 8
The comparative example relates to a nanoscale mixed particle reinforced ultra-high rigidity aluminum-lithium-rare earth-based composite material, the mass percentages of the components of the composite material are the same as those of the composite material in example 1, and the preparation method is basically the same, except that in the second step, the reinforcement is placed into a vacuum furnace to be preheated at 320 ℃.
The tensile property at room temperature measured after the aluminum-lithium-rare earth-based composite material is subjected to heat treatment is as follows: 390MPa of yield, 506MPa of tensile strength, 5.3 percent of elongation and 95GPa of elastic modulus.
Comparative example 9
The comparative example relates to a nanoscale mixed particle reinforced ultra-high rigidity aluminum-lithium rare earth-based composite material, the mass percentages of the components of the composite material are the same as those in example 1, the preparation method is basically the same, and the difference is that in the first step, the membrane material is Al 2Ce。
The tensile property at room temperature measured after the aluminum-lithium-rare earth-based composite material is subjected to heat treatment is as follows: yield of 386MPa, tensile strength of 508MPa, elongation of 5.2 percent and elastic modulus of 88 GPa.
Comparative example 10
The comparative example relates to a nanoscale mixed particle reinforced ultra-high rigidity aluminum-lithium-rare earth-based composite material, the mass percentages of the components of the composite material are the same as those of the composite material in example 1, the preparation method is basically the same, and the difference is that in the step one, the overturning device is made of cast iron material.
The tensile property at room temperature measured after the aluminum-lithium-rare earth-based composite material is subjected to heat treatment is as follows: yield 376MPa, tensile strength 493MPa, elongation 3.3 percent and elastic modulus 85 GPa. Because the overturning equipment made of common cast iron materials is used, certain magnetic field interference exists in the magnetron sputtering process, the physical vapor deposition process is disordered, and the coating is uneven.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.

Claims (4)

1. A method for modifying a reinforcement suitable for casting a lithium aluminum-based composite material, the method comprising the steps of:
Placing the reinforcement body in a turnover device for turnover, bombarding a coating film material by utilizing magnetron sputtering, and depositing the generated ionized gas phase on the surface of the reinforcement body to form a uniform coating to obtain a modified reinforcement body;
the reinforcement is one or two composite powders of graphene and carbon nano tubes;
the coating film material is Al with the weight portion ratio of 45-55: 25-35: 15-252Ce. Dy and La mixed target material;
the turnover device is made of ceramic materials; the rotating speed is controlled to be 10-20 rad/min;
before bombarding the film material by magnetron sputtering, firstly placing the film material of the coating layer in a crucible and heating to 750-850 ℃; the bombardment time is 60-90 min;
carrying out vacuum heat treatment on the coated reinforcement body with the vacuum degree of 10-3~10-4MPa; the heat treatment is to preheat at 200-250 ℃ and preserve heat for 20-40 min; and then preserving the heat for 3-4 h at the temperature of 450-470 ℃.
2. The method for modifying the reinforcement suitable for casting the aluminum-lithium based composite material as claimed in claim 1, wherein the reinforcement and the Al scrap after the heat treatment are mixed according to a ratio of 1: 40-50, and then 0.8-1.2% by mass of acidic aluminum phosphate is added to the mixture to be mixed and ball-milled to form a precast block.
3. A method of making a lithium aluminum-based composite using the modified reinforcement of any of claims 1-2, comprising the steps of:
S1: melting the components except Li based on aluminum lithium, then spreading a mixed powder covering agent with the mass ratio of LiCl to LiF =3:1, adding high-purity Li, and carrying out rotary blowing high-purity argon refining;
s2: mechanically stirring the refined melt in an argon atmosphere, and pressing the precast block into the melt after the stirring speed is reduced when the temperature of the melt is 20-30 ℃ above the solidus; after continuously stirring for 15-25min, pouring at 710-730 ℃ to obtain a reinforced lithium-aluminum base composite material; the precast block is prepared by mixing the modified reinforcement after heat treatment and Al chips according to the proportion of 1: 40-50, adding 0.8-1.2% of acidic aluminum phosphate by mass, mixing and ball-milling.
4. The aluminum-lithium-based composite material prepared by the method of claim 3, wherein the aluminum-lithium-based composite material comprises the following components in percentage by mass: 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%, carbon nanotube reinforced by coating film: 1.0-3.0%, coating film reinforced graphene: 0.1-0.5%, impurity elements not higher than 0.02%, and the balance of Al.
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