A method for graphene-reinforced aluminum alloy

Abstract

The present invention provides a method for graphene-reinforced aluminum alloys. The method uses an intermittent ball milling process to reduce graphene structural damage during the milling process and slow the reaction between copper oxide on the graphene surface and aluminum powder. Under casting conditions, the copper oxide on the graphene surface improves the wettability of the graphene with molten aluminum. Ultrasonic vibration is used to disperse the copper oxide to coat the graphene. The in-situ reaction between aluminum and the copper oxide on the graphene surface allows copper atoms to migrate into the aluminum matrix, forming a transition zone between the graphene and aluminum. This strengthens the interfacial bonding between the graphene and the aluminum matrix, hinders the aluminum-carbon reaction, and protects the graphene structure. T6 treatment is used to obtain more dispersed phases, enhancing the dispersion strengthening effect. The method is simple to operate, has a stable process, and well preserves the graphene structure. The prepared graphene-reinforced aluminum-based composite material exhibits good interfacial bonding between the graphene and the matrix.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal material manufacturing, and in particular relates to a method for strengthening aluminum alloy with graphene. Background Art

[0002] Aluminum-based composites are valued for their lightweight, high specific strength, excellent electrical and thermal conductivity, and wear resistance. Modern industrial development, in particular, is driving a surge in demand for high-performance aluminum-based composites, driven by the increasing demand for high-strength and lightweight metal products. Since its discovery, graphene has exhibited excellent mechanical and functional properties, such as ultra-high strength and Young's modulus. Consequently, graphene has been extensively studied and considered an ideal reinforcement for composites. However, the widespread adoption of graphene-reinforced aluminum-based composites has been hampered by three key issues: poor wettability with molten aluminum, strong agglomeration of graphene in molten aluminum, and low interfacial bonding strength between the graphene and the aluminum matrix.

[0003] In patent CN115156505A, entitled "A Method for Preparing a Highly Oriented Graphene Aluminum-Based Composite," a composite sheet is prepared by ball-milling a mixture of SiC, tungsten powder, graphene, graphene oxide, KCl, MgO, and NH₄HCO₃ and then impregnating it with a copper solution. The aluminum / graphene solution, prepared by mechanical stirring, is then cast in a mold lined with a thin sheet in a predetermined orientation to produce the graphene / aluminum composite. This graphene / aluminum composite exhibits high electrical and thermal conductivity, but the graphene easily agglomerates and exhibits poor wettability with molten aluminum, making it difficult to disperse in the molten aluminum. Furthermore, the interfacial bonding of the prepared graphene / aluminum composite is uncontrollable. In patent CN112281012B, entitled "A Copper-Coated Graphene Aluminum-Based Composite and Its Preparation Method," copper is plated on the graphene surface, followed by magnetic stirring to prepare a copper-coated graphene / aluminum composite powder. The copper-coated graphene / aluminum composite powder is then subjected to spark plasma sintering to obtain the copper-coated graphene / aluminum composite. This process can achieve a relatively uniform dispersion of graphene in the aluminum matrix, but the solid solubility of copper in the aluminum matrix is ​​relatively high. During the preparation process, the copper on the graphene surface will diffuse into the aluminum matrix, resulting in direct contact between the graphene and the aluminum matrix in the copper-plated graphene aluminum-based composite material. The interface bonding strength between the graphene and the aluminum matrix is ​​low, and the aluminum-carbon reaction between the graphene and aluminum will also destroy the graphene structure. Therefore, the copper-plated graphene aluminum-based composite material prepared by this process cannot fully exert the strengthening effect of graphene. In patent CN108359852B, entitled "A graphene-enhanced high-silicon aluminum-based composite material and its preparation method", a blank is prepared by long-term ball milling of a mixed powder of silicon, copper, magnesium, titanium, boron, graphene and aluminum in a certain proportion, followed by hot pressing and sintering. The graphene-enhanced high-silicon aluminum-based composite material is then obtained by heat treating the blank and then performing 5 to 10 forging and annealing treatments. The graphene-reinforced high-silicon aluminum-based composite material prepared by this process has high hardness, but the bonding strength between graphene and the aluminum matrix is ​​low, and the preparation process is too cumbersome. The powder metallurgy process cannot produce parts with complex shapes, and multiple forging passes will also reduce the output speed of the finished product, making it unsuitable for large-scale production in industry.

[0004] In view of this, the present invention aims to explore a graphene-enhanced aluminum alloy preparation technology that can better solve the above problems. Summary of the Invention

[0005] In response to the problems existing in the preparation of graphene-reinforced aluminum-based composite materials in the background technology, the present invention provides a method for graphene-reinforced aluminum alloy, which mainly includes using copper oxide-coated graphene as a reinforcement, pre-dispersing the copper oxide-coated graphene through intermittent ball milling while reducing structural damage to the graphene, introducing ultrasonic vibration during smelting, and forming a transition zone between graphene and aluminum through in-situ reaction, thereby improving the graphene / aluminum interface bonding strength and hindering aluminum-carbon reaction, protecting the structure of the graphene, and using T6 heat treatment to allow the introduced copper element to be uniformly precipitated in the form of a dispersed phase, thereby improving the performance of the composite material.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] The present invention provides a method for strengthening aluminum alloy with graphene, comprising the following steps:

[0008] Step 1: Add copper sulfate pentahydrate (CuSO4·5H2O) and hexadecyltrimethylammonium bromide (C 16 H 33 (CH3)3NBr), the mixed solution is stirred and heated, filtered and dried to obtain a precursor, and the precursor is calcined to obtain copper oxide-coated graphene powder;

[0009] Step 2: The copper oxide-coated graphene powder obtained in step 1 is mixed with aluminum powder and stearic acid and subjected to ball milling;

[0010] Step 3: cold pressing the mixed powder obtained by ball milling in step 2 into a prefabricated block;

[0011] Step 4: heating and melting the aluminum alloy and removing the slag, adding the prefabricated block obtained in step 3 to the obtained melt and simultaneously ultrasonically treating it, and cooling it to obtain a billet;

[0012] Step 5: Take the blank obtained in step 4 and perform T6 heat treatment to obtain a graphene-reinforced aluminum alloy composite material.

[0013] Preferably, the ratio of graphene oxide to copper sulfate pentahydrate added in step 1 is such that copper oxide accounts for 40%-60% of the total mass of the copper oxide-coated graphene powder.

[0014] Preferably, the temperature of the mixed solution stirred and heated in step 1 is 120° C., and the pH value needs to be adjusted to 10-11; the precursor is calcined in an argon environment at a temperature of 300-400° C.

[0015] Preferably, in step 2, the mass ratio of copper oxide-coated graphene powder to stearic acid is 2:1.

[0016] Preferably, the mixed ball milling conditions in step 2 are: ball milling speed 200-300 rpm, ball-to-material ratio 8-10:1; stop and stand for 5-10 minutes after each ball milling for 30 minutes, and the total ball milling time is 2-4 hours.

[0017] Preferably, the cold pressing pressure in step 3 is 500 MPa, and the holding time is 5-10 min.

[0018] Preferably, the power of the ultrasonic treatment in step 4 is 2.8 kW and the frequency is 20 kHz.

[0019] Preferably, in step 4, the aluminum alloy is heated to a melting temperature of 760-780°C; the temperature of the blank obtained by cooling is 730°C, and the cooling rate is 3-6°C / min.

[0020] The main principles of the present invention are:

[0021] Cu(OH)2=CuO+H2O(1)

[0022] 3CuO+2Al=Al2O3+3Cu(2)

[0023] In the mixed solution, the functional groups on the surface of graphene oxide adsorb copper ions to form Cu(OH)2. 16 H 33 (CH3)3NBr controls the growth rate and size of Cu(OH)2, and then the Cu(OH)2 is pyrolyzed to obtain copper oxide-coated graphene oxide powder. During the subsequent smelting process, the copper oxide and the aluminum matrix react in situ on the surface of the graphene oxide, forming a transition zone between the graphene oxide and the aluminum matrix and releasing a large amount of energy, and the copper atoms quickly migrate into the aluminum matrix.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. Join C 16 H 33 (CH3)3NBr controls the morphology of copper oxide, and the copper oxide particles reach nanometer scale;

[0026] 2. Use intermittent ball milling to reduce graphene structural damage during the ball milling process and slow down the reaction between copper oxide and aluminum powder on the graphene surface;

[0027] 3. Use copper oxide on the graphene surface to improve wettability. Under high temperature conditions, copper oxide reacts with the aluminum matrix in situ on the graphene surface, forming a transition zone between the graphene and the aluminum matrix, which strengthens the interface bonding between the graphene and the aluminum matrix and hinders the aluminum-carbon reaction, while protecting the graphene structure.

[0028] 4. A large amount of energy is released during the in-situ reaction, and copper atoms migrate into the aluminum matrix. More dispersed phases are obtained through T6 heat treatment, enhancing the dispersion strengthening effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 TEM image of the interface between graphene and aluminum matrix in the graphene-reinforced A380 composite material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] To make the objects, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be described clearly and completely below in conjunction with the examples. Where specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or the conditions recommended by the manufacturer. Where the manufacturer of the reagents or instruments is not specified, all are commercially available conventional products.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art in the art. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0032] Example 1

[0033] 1. Graphene oxide was dispersed in anhydrous ethanol to obtain a dispersion, copper sulfate pentahydrate and hexadecyltrimethylammonium bromide were added thereto, the mixture was magnetically stirred, a pH regulator was added to adjust the pH to 10.5, and the mixture was heated at 120° C. in a reactor, filtered, and dried to obtain a precursor, which was calcined at 350° C. to obtain copper oxide-coated graphene powder (the ratio of graphene oxide to copper sulfate pentahydrate was controlled so that the mass proportion of copper oxide was 40%).

[0034] Take 2.50g of the prepared copper oxide-coated graphene powder, 1.25g of stearic acid, 21.25g of aluminum powder and 250g of zirconium dioxide balls and place them in a ball mill. After nitrogen is introduced to isolate the air, ball mill at 200rpm for 30min, then turn off the ball mill and let it stand for 8min. Repeat the above steps until the mixed powder ball milling time reaches 4h.

[0035] 2. The mixed powder obtained by ball milling was placed in a mold and cold pressed at room temperature to obtain a prefabricated block with a graphene mass fraction of 6 wt.%; the pressure during cold pressing was 500 MPa and the holding time was 5 min.

[0036] 3. Cut the obtained prefabricated block into small pieces and place them in a vacuum drying oven at 60°C for drying.

[0037] 4. Take 125g of A380 aluminum alloy and put it into a dried graphite crucible. Then put the crucible into a resistance furnace and heat it to 760℃. Keep it warm for more than 30 minutes. After the aluminum alloy is completely melted, introduce argon gas into the resistance furnace.

[0038] 5. Take 2.50 g of hexachloroethane and add it to the melt obtained in the above step to remove the slag.

[0039] 6. Add the obtained prefabricated blocks to the melt after slag removal, apply high-energy ultrasound (ultrasonic power of 2.8 kW, frequency of 20 kHz) when adding the prefabricated blocks, continue ultrasound after the addition of the prefabricated blocks, and cool the resistance furnace at the same time at a cooling rate of 4 ° C / min. When the temperature drops to 730 ° C, turn off the ultrasound and argon, and pour the melt into the mold to obtain the billet.

[0040] 7. The obtained blank was treated at a temperature field of 515°C for 2 hours and then water quenched to room temperature to obtain a solid solution blank; the solid solution blank was treated at a temperature field of 170°C for 12 hours and then air-cooled to room temperature to obtain a graphene-reinforced A380 composite material with a graphene mass fraction of 1.0 wt.%.

[0041] Figure 1 TEM image of the interface between graphene and aluminum matrix in the prepared graphene-reinforced A380 composite material.

[0042] The copper oxide-coated graphene / aluminum-based composite material (graphene-enhanced A380 composite material) prepared in this embodiment has significantly improved mechanical properties compared with the uncoated graphene / aluminum-based composite material (graphene oxide-enhanced A380 composite material not coated with copper oxide): its yield strength (203.4 MPa) is 19.2% higher than that of the uncoated graphene / aluminum-based composite material (170.6 MPa); the ultimate tensile strength (317.4 MPa) is 27.3% higher than that of the uncoated graphene / aluminum-based composite material (249.3 MPa).

[0043] Example 2

[0044] 1. Graphene oxide was dispersed in anhydrous ethanol to obtain a dispersion, copper sulfate pentahydrate and hexadecyltrimethylammonium bromide were added thereto, the mixture was magnetically stirred, a pH regulator was added to adjust the pH to 10.5, and the mixture was heated at 120° C. in a reactor, filtered, and dried to obtain a precursor, which was calcined at 350° C. to obtain copper oxide-coated graphene powder (the ratio of graphene oxide to copper sulfate pentahydrate was controlled so that the mass proportion of copper oxide was 48%).

[0045] Take 2.90g of the prepared copper oxide-coated graphene powder, 1.45g of stearic acid, 20.66g of aluminum powder and 250g of zirconium dioxide balls and place them in a ball mill. After nitrogen is introduced to isolate the air, ball mill at 200rpm for 30min, then turn off the ball mill and let it stand for 8min. Repeat the above steps until the mixed powder ball milling time reaches 4h.

[0046] 2. The mixed powder obtained by ball milling was placed in a mold and cold pressed at room temperature to obtain a prefabricated block with a graphene mass fraction of 9 wt.%; the pressure during cold pressing was 500 MPa and the holding time was 8 minutes.

[0047] 3. Cut the obtained prefabricated block into small pieces and place them in a vacuum drying oven at 60°C for drying.

[0048] 4. Take 125g of 2024 aluminum alloy and put it into a dried graphite crucible. Then put the crucible into a resistance furnace and heat it to 780℃. Keep it warm for more than 30 minutes. After the aluminum alloy is completely melted, introduce argon gas into the resistance furnace.

[0049] 5. Take 2.50 g of hexachloroethane and add it to the melt obtained in the above step to remove the slag.

[0050] 6. Add the obtained prefabricated blocks to the melt after slag removal, apply high-energy ultrasound (ultrasonic power of 2.8 kW, frequency of 20 kHz) when adding the prefabricated blocks, continue ultrasound after the addition of the prefabricated blocks, and cool the resistance furnace at the same time at a cooling rate of 5 ° C / min. When the temperature drops to 730 ° C, turn off the ultrasound and argon, and pour the melt into the mold to obtain the billet.

[0051] 7. The obtained blank was treated at a temperature field of 495°C for 2 hours and then water quenched to room temperature to obtain a solid solution blank; the solid solution blank was treated at a temperature field of 180°C for 10 hours and then air-cooled to room temperature to obtain a graphene-reinforced 2024 composite material with a graphene mass fraction of 1.0 wt.%.

[0052] The copper oxide-coated graphene / aluminum-based composite material (graphene-enhanced 2024 composite material) prepared in this embodiment has significantly improved mechanical properties compared with the uncoated graphene / aluminum-based composite material (graphene oxide-enhanced 2024 composite material not coated with copper oxide): its yield strength (225.6 MPa) is 21.6% higher than that of the uncoated graphene / aluminum-based composite material (185.5 MPa); the ultimate tensile strength (350.4 MPa) is 31.4% higher than that of the uncoated graphene / aluminum-based composite material (266.7 MPa).

[0053] Example 3

[0054] 1. Graphene oxide was dispersed in anhydrous ethanol to obtain a dispersion, copper sulfate pentahydrate and hexadecyltrimethylammonium bromide were added thereto, the mixture was magnetically stirred, a pH regulator was added to adjust the pH to 10.5, and the mixture was heated at 120° C. in a reactor, filtered, and dried to obtain a precursor, which was calcined at 350° C. to obtain copper oxide-coated graphene powder (the ratio of graphene oxide to copper sulfate pentahydrate was controlled so that the mass proportion of copper oxide was 58%).

[0055] Take 3.76g of the prepared copper oxide-coated graphene powder, 1.88g of stearic acid, 19.37g of aluminum powder and 250g of zirconium dioxide balls and place them in a ball mill. After nitrogen is introduced to isolate the air, ball mill at 250rpm for 30min, then turn off the ball mill and let it stand for 10min. Repeat the above steps until the mixed powder ball milling time reaches 4h.

[0056] 2. The mixed powder obtained by ball milling is placed in a mold and cold pressed at room temperature to obtain a prefabricated block with a graphene mass fraction of 10 wt.%; the pressure during cold pressing is 500 MPa and the holding time is 10 min.

[0057] 3. Cut the obtained prefabricated block into small pieces and place them in a vacuum drying oven at 60°C for drying.

[0058] 4. Take 125g of 6061 aluminum alloy and put it into a dried graphite crucible. Then put the crucible into a resistance furnace and heat it to 760℃. Keep it warm for more than 30 minutes. After the aluminum alloy is completely melted, introduce argon gas into the resistance furnace.

[0059] 5. Take 2.40 g of hexachloroethane and add it to the melt obtained in the above step to remove the slag.

[0060] 6. Add the obtained prefabricated blocks to the melt after slag removal, apply high-energy ultrasound (ultrasonic power of 2.8 kW, frequency of 20 kHz) when adding the prefabricated blocks, continue ultrasound after the addition of the prefabricated blocks, and cool the resistance furnace at the same time at a cooling rate of 5 ° C / min. When the temperature drops to 730 ° C, turn off the ultrasound and argon, and pour the melt into the mold to obtain the billet.

[0061] 7. The obtained blank was treated at a temperature field of 530°C for 1 hour and then water quenched to room temperature to obtain a solid solution blank; the solid solution blank was treated at a temperature field of 175°C for 48 hours and then air-cooled to room temperature to obtain a graphene-reinforced 6061 composite material with a graphene mass fraction of 1.0 wt.%.

[0062] The copper oxide-coated graphene / aluminum-based composite material (graphene-enhanced 6061 composite material) prepared in this embodiment has significantly improved mechanical properties compared with the uncoated graphene / aluminum-based composite material (graphene oxide-enhanced 6061 composite material not coated with copper oxide): its yield strength (205.5 MPa) is 18.5% higher than that of the uncoated graphene / aluminum-based composite material (173.4 MPa); the ultimate tensile strength (308.8 MPa) is 25.7% higher than that of the uncoated graphene / aluminum-based composite material (245.6 MPa).

[0063] The embodiments described above merely represent several preferred embodiments of the present invention. While the descriptions are relatively specific and detailed, they are not intended to limit the present invention. It should be noted that those skilled in the art will readily appreciate that the present invention is susceptible to various variations and modifications. Any modifications, equivalent substitutions, or improvements within the scope of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A method for strengthening aluminum alloy with graphene, characterized in that: The following steps are involved: Step 1: adding copper sulfate pentahydrate and hexadecyltrimethylammonium bromide to an ethanol dispersion of graphene oxide, stirring and heating the mixture, filtering, and drying to obtain a precursor, and calcining the precursor to obtain copper oxide-coated graphene powder; Step 2: The copper oxide-coated graphene powder obtained in step 1 is mixed with aluminum powder and stearic acid and subjected to ball milling; The mixed ball milling conditions are as follows: a ball milling speed of 200-300 rpm, a ball-to-material ratio of 8-10:1; after each 30-minute ball milling, the mixture is allowed to stand for 5-10 minutes, and the total ball milling time is 2-4 hours. Step 3: cold pressing the mixed powder obtained by ball milling in step 2 into a prefabricated block; Step 4: heating and melting the aluminum alloy and removing the slag, adding the prefabricated block obtained in step 3 to the obtained melt and simultaneously ultrasonically treating it, and cooling it to obtain a billet; Step 5: Take the blank obtained in step 4 and perform T6 heat treatment to obtain a graphene-reinforced aluminum alloy composite material.

2. The method for graphene-enhanced aluminum alloy according to claim 1, wherein: In step 1, the ratio of the added amount of graphene oxide to copper sulfate pentahydrate is such that copper oxide accounts for 40%-60% of the total mass of the copper oxide-coated graphene powder.

3. The method for graphene-enhanced aluminum alloy according to claim 1, wherein: In step 1, the temperature for the mixed solution stirring and heating treatment is 120° C., and the pH value needs to be adjusted to 10-11; the precursor is calcined in an argon environment at a temperature of 300-400° C.

4. The method for graphene-enhanced aluminum alloy according to claim 1, wherein: In step 2, the mass ratio of copper oxide-coated graphene powder to stearic acid is 2:

1.

5. The method for graphene-enhanced aluminum alloy according to claim 1, wherein: The cold pressing pressure in step 3 is 500 MPa, and the holding time is 5-10 min.

6. The method for graphene-enhanced aluminum alloy according to claim 1, wherein: The power of the ultrasonic treatment in step 4 is 2.8 kW and the frequency is 20 kHz.

7. The method for graphene-enhanced aluminum alloy according to claim 1, wherein: Step 4: The aluminum alloy is heated to a melting temperature of 760-780°C; the temperature of the blank obtained by cooling is 730°C.

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