Reduced graphene oxide / high entropy alloy reinforced aluminum alloy rods and their preparation methods

Abstract

This invention discloses a reduced graphene oxide / high entropy alloy reinforced aluminum alloy rod and its preparation method, belonging to the field of aluminum alloy composite material technology. This invention uses a mechanical ball milling method to attach a high entropy alloy to the surface of nano-reduced graphene oxide. Using powder metallurgy, the nano-reduced graphene oxide / high entropy alloy particles are hot-pressed and sintered with aluminum alloy powder, followed by extrusion to obtain the reduced graphene oxide / high entropy alloy reinforced aluminum alloy rod. The hot-pressing pre-sintering creates a preliminary metallurgical effect on the surface of the metal billet, thereby improving the quality problems of wrinkles, peeling, and low density in the subsequent hot extrusion process. The high entropy alloy formed from Al, Fe, Ni, Cr, and Co, along with nano-reduced graphene oxide as reinforcing particles, combined with aluminum alloy and hot extruded, further improves the comprehensive mechanical properties of the aluminum alloy rod and reduces microscopic defects, thus effectively solving the technical problem of poor mechanical properties in aluminum alloy rods.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy and nanomaterial synthesis technology, specifically to reduced graphene oxide / high entropy alloy reinforced aluminum alloy rods and their preparation methods. Background Technology

[0002] Aluminum matrix composites (AMCs) are high-strength, high-modulus, high-stiffness, and low-cost high-performance structural materials widely used in the automotive, aerospace, transportation, and military industries, offering significant environmental and economic benefits. Powder metallurgy is one of the main methods for preparing AMCs, ensuring the uniformity and accuracy of material composition and producing materials with high precision and consistency. However, previous preparation processes involved cold pressing followed by extrusion of rods, which easily led to product quality issues such as surface wrinkles, peeling, and low density.

[0003] When using reinforcing particles to reinforce composite materials, the composition and preparation process of the reinforcing particles are of great concern. The influence of different types of reinforcing particles on the material properties and the design of forming processes are key research areas for aluminum-based composite materials. Patent publication number CN116479274A discloses a method for preparing aluminum alloy composite materials from 6061 aluminum alloy by adding nano-reduced graphene oxide / alumina particles. This method involves preparing alumina via a hydrothermal method and simultaneously loading it onto the surface of nano-reduced graphene oxide to obtain nano-reduced graphene oxide / alumina particles. However, this method has a long cycle time and poor adhesion of alumina to the surface of nano-reduced graphene oxide, which increases the contact area between the aluminum matrix and the reduced graphene oxide. This makes it easy for the two to react during high-temperature extrusion to form the brittle Al4C3 phase, resulting in poor mechanical properties of the aluminum alloy composite material. In addition, patent publication number CN118993713A discloses a toughened ceramic material and an additive manufacturing method. Although alumina, as a type of ceramic particle, has high hardness and high temperature stability, it has problems with poor fracture toughness and weak fatigue resistance, which leads to poor mechanical properties of the prepared composite material. Summary of the Invention

[0004] This invention provides aluminum alloy rods reinforced with reduced graphene oxide / high entropy alloy and their preparation method. It effectively solves the quality problems of surface wrinkling, peeling, and low density caused by cold pressing followed by extrusion of rods in existing aluminum alloy composite material preparation methods. It also addresses the technical problems of poor toughness and fatigue resistance in aluminum alloy composite rods due to the use of alumina as reinforcing particles, and the formation of the Al4C3 brittle phase during high-temperature extrusion of the aluminum matrix and reduced graphene oxide, leading to a decrease in the mechanical properties of the aluminum alloy composite material. This invention uses nano-reduced graphene oxide and high entropy alloy as reinforcing particles, and mechanically combines the two types of reinforcing particles, significantly shortening the experimental cycle and improving the adhesion rate of the high entropy alloy to the surface of reduced graphene oxide. The composite reinforcing particles are then combined with the aluminum alloy matrix, and a hot-pressing sintering step is performed before hot extrusion, thereby improving the density and mechanical properties of the aluminum alloy rods.

[0005] The first objective of this invention is to provide a method for preparing reduced graphene oxide / high-entropy alloy reinforced aluminum alloy rods, comprising the following steps:

[0006] High-entropy alloy was loaded onto reduced graphene oxide by mechanical ball milling in a protective atmosphere to obtain reduced graphene oxide / high-entropy alloy particles; the high-entropy alloy was composed of Al, Fe, Ni, Cr and Co in a weight ratio of 0.5:1:1:1:1.

[0007] Using the reduced graphene oxide / high entropy alloy particles as reinforcing particles and aluminum alloy powder as the matrix, aluminum alloy rods reinforced with reduced graphene oxide / high entropy alloy are obtained by hot pressing and sintering and extrusion through powder metallurgy. The mass of the reduced graphene oxide / high entropy alloy particles is 0.1% to 0.3% of the mass of the aluminum alloy powder.

[0008] In a preferred embodiment, the mass ratio of the reduced graphene oxide to the high-entropy alloy is 1:0.8~1.2.

[0009] As a preferred embodiment, during hot pressing sintering, the temperature is raised to 420℃~450℃, the pressure is raised to 10MPa~15MPa, and the hot pressing sintering time is 60min~70min.

[0010] In a preferred embodiment, stainless steel grinding balls with diameters of 5 mm, 8 mm, and 10 mm and a mass ratio of 3:2:1 are used to grind the high-entropy alloy and reduced graphene oxide at a rotation speed of 400 r / min to 450 r / min and a ball-to-material ratio of 10 to 20:1 for 4 to 6 hours.

[0011] As a preferred embodiment, during ball milling, 1% to 3% of the total mass of reduced graphene oxide and high-entropy alloy n-heptane is added, and ball milling is paused for 10 minutes after 1 hour.

[0012] As a preferred embodiment, before hot pressing and sintering, the reduced graphene oxide / high entropy alloy particles are mixed with aluminum alloy powder and ball-milled for 8 to 10 hours at a speed of 200 rpm to 240 rpm and a ball-to-material ratio of 5 to 6:1.

[0013] In one preferred embodiment, a preform is obtained after hot pressing and sintering. The preform is then placed in an extrusion mold, heated to 450°C~500°C, held for 30min~40min, and extruded.

[0014] The second objective of this invention is to provide a reduced graphene oxide / high-entropy alloy reinforced aluminum alloy rod prepared by the above-described preparation method.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] This invention provides a method for preparing aluminum alloy rods reinforced with reduced graphene oxide / high entropy alloy. The method involves ball milling nano-reduced graphene oxide and high entropy alloy in a protective atmosphere. The impact and grinding action generated by the mechanical ball milling method creates a high-strength mechanical adhesion between the nano-reduced graphene oxide and the high entropy alloy, thereby improving the adhesion of the high entropy alloy to the surface of the nano-reduced graphene oxide, resulting in nano-reduced graphene oxide / high entropy alloy particles. Using powder metallurgy, the nano-reduced graphene oxide / high entropy alloy particles are hot-pressed and sintered with aluminum alloy powder, followed by extrusion to obtain aluminum alloy rods reinforced with reduced graphene oxide / high entropy alloy. The hot-pressing pre-sintering creates a preliminary metallurgical effect on the surface of the metal blank, thereby improving quality problems such as wrinkles, peeling, and low density in the subsequent hot extrusion process. The high-entropy alloy formed by Al, Fe, Ni, Cr and Co used in this invention has excellent strength, hardness, toughness and fatigue resistance. The high-entropy alloy and nano-reduced graphene oxide are used as reinforcing particles and then composited with aluminum alloy through hot extrusion. This further improves the comprehensive mechanical properties of the aluminum alloy rod and reduces micro-defects, thereby effectively avoiding the technical problem of poor mechanical properties of aluminum alloy composite materials caused by the formation of the Al4C3 brittle phase during high-temperature extrusion of aluminum matrix and reduced graphene oxide. Attached Figure Description

[0017] Figure 1 The image shows a SEM image of the reduced graphene oxide / high-entropy alloy particles prepared in Example 1 of this invention. HEA represents the high-entropy alloy.

[0018] Figure 2 The transverse SEM microstructure of the aluminum alloy rod prepared by the present invention is shown in Figure (a), which is Comparative Example 1, Figure (b) is Example 1, Figure (c) is Example 2, and Figure (d) is Example 3.

[0019] Figure 3 The SEM microstructure of the fracture morphology of the tensile specimen of the aluminum alloy bar prepared in this invention is shown in Figure 1, (a) is Comparative Example 1, (b) is Example 1, (c) is Example 2, (d) is Example 3, (e) is Comparative Example 3, and (f) is Comparative Example 2.

[0020] Figure 4 The images show the XRD patterns of the aluminum alloy bars prepared in Examples 1 to 3 and Comparative Examples 1 to 3 of the present invention.

[0021] Figure 5 The image shows the Vickers hardness curves of the aluminum alloy bars prepared in Comparative Examples 1 to 3 and Examples 1 to 3 of this invention.

[0022] Figure 6 The true stress-strain curves of the aluminum alloy bars prepared in Comparative Example 1 and Examples 1 to 3 of this invention are shown in the tensile test.

[0023] Figure 7 This is a bar chart showing the tensile strength, yield strength, and elongation of the aluminum alloy bars prepared in Comparative Examples 1 to 3 and Examples 1 to 3 of the present invention. Detailed Implementation

[0024] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention is further described below with reference to specific embodiments. However, the embodiments are not intended to limit the invention. Unless otherwise specified, the following test methods and detection methods are conventional methods; unless otherwise specified, the reagents and raw materials are commercially available.

[0025] To address the following technical problems with existing aluminum-based composite materials: First, the preparation process involves cold pressing followed by extrusion into rods, which easily leads to surface wrinkles, peeling, and low density, resulting in poor product quality. Second, the preparation of reinforcing particles in aluminum-based composite materials involves hydrothermal alumina loading onto nano-reduced graphene oxide. This method is time-consuming, and the adhesion of alumina to the nano-reduced graphene oxide surface is poor, increasing the contact area between the aluminum matrix and the reduced graphene oxide. This makes them prone to reacting during high-temperature extrusion to form the brittle Al4C3 phase, resulting in poor mechanical properties of the aluminum alloy composite material. Third, although alumina has high hardness, its toughness and fatigue resistance are relatively weak. Based on these technical problems, this invention provides reduced graphene oxide / high-entropy alloy reinforced aluminum alloy rods and their preparation method.

[0026] The technical solution of the present invention will be described in detail below.

[0027] This invention first provides a method for preparing reduced graphene oxide / high-entropy alloy reinforced aluminum alloy rods, comprising the following steps:

[0028] High-entropy alloy was loaded onto reduced graphene oxide by mechanical ball milling in a protective atmosphere to obtain reduced graphene oxide / high-entropy alloy particles; the high-entropy alloy was composed of Al, Fe, Ni, Cr and Co in a weight ratio of 0.5:1:1:1:1.

[0029] Using the reduced graphene oxide / high entropy alloy particles as reinforcing particles and aluminum alloy powder as the matrix, aluminum alloy rods reinforced with reduced graphene oxide / high entropy alloy are obtained by hot pressing and sintering and extrusion through powder metallurgy.

[0030] In the above technical solution, the impact and grinding action generated by mechanical ball milling creates a high-strength mechanical bond between the reduced graphene oxide and the high-entropy alloy, thereby improving the adhesion of the high-entropy alloy to the surface of the reduced graphene oxide. Hot pressing pre-sintering creates a preliminary metallurgical effect on the surface of the metal billet, thus improving quality issues such as wrinkles, peeling, and low density in subsequent hot extrusion processes. Hot extrusion of a composite aluminum alloy using a high-entropy alloy formed from Al, Fe, Ni, Cr, and Co as reinforcing particles and reduced graphene oxide further improves the comprehensive mechanical properties of the aluminum alloy rod and reduces microscopic defects. This effectively avoids the technical problem of poor mechanical properties of the aluminum alloy composite material caused by the formation of the brittle Al4C3 phase during high-temperature extrusion of the aluminum matrix and reduced graphene oxide.

[0031] In a preferred embodiment, the mass ratio of reduced graphene oxide to high-entropy alloy is 1:0.8~1.2. If the amount of high-entropy alloy used is less than 0.8, that is, the amount of high-entropy alloy used is small, it will lead to a decrease in the loading rate of high-entropy alloy on reduced graphene oxide and a decrease in its reinforcing effect. If the amount of high-entropy alloy used is greater than 1.2, that is, the amount of high-entropy alloy used is too large, it will lead to graphene agglomeration, thereby reducing the mechanical properties of aluminum alloy rods.

[0032] It should be noted that the high-entropy alloy used in this invention is composed of Al, Fe, Ni, Cr and Co in a weight ratio of 0.5:1:1:1:1, and the high-entropy alloy was purchased from Aero Engine New Materials Technology Co., Ltd.

[0033] To improve the mechanical strength of the aluminum alloy matrix, the mass of the reduced graphene oxide / high entropy alloy particles is 0.1% to 0.3% of the mass of the aluminum alloy powder. If the mass percentage of the reduced graphene oxide / high entropy alloy particles is less than 0.1%, the improvement in mechanical properties will be insignificant, and the reinforcing effect will be small. If the mass percentage of the reduced graphene oxide / high entropy alloy particles is greater than 0.3%, it will lead to local agglomeration, thereby reducing the mechanical properties of the aluminum alloy rod.

[0034] To further improve the mechanical strength of aluminum alloy bars and facilitate the placement of the mixture of high-entropy alloy and reduced graphene oxide into the extrusion die, the temperature is raised to 420℃~450℃ and the pressure is raised to 10MPa~15MPa during hot pressing sintering, and the hot pressing sintering time is 60min~70min.

[0035] To improve the adhesion of high-entropy alloy to the surface of reduced graphene oxide, stainless steel grinding balls with diameters of 5 mm, 8 mm, and 10 mm and a mass ratio of 3:2:1 were used. The high-entropy alloy and reduced graphene oxide were ball-milled at a speed of 400 r / min to 450 r / min and a ball-to-material ratio of 10 to 20:1 for 4 to 6 hours.

[0036] To prevent cold welding caused by excessively high temperature during ball mill operation and to improve the ball milling effect, 1%~3% of the total mass of reduced graphene oxide and high-entropy alloy n-heptane is added during ball milling, and the milling is paused for 10 minutes after 1 hour.

[0037] To improve the dispersion uniformity of reduced graphene oxide / high entropy alloy particles in the aluminum alloy matrix, before hot pressing and sintering, the reduced graphene oxide / high entropy alloy particles are mixed with aluminum alloy powder and ball-milled for 8 to 10 hours at a speed of 200 rpm to 240 rpm and a ball-to-material ratio of 5 to 6:1.

[0038] In order to prepare aluminum alloy rods with excellent mechanical properties, a preform is obtained after hot pressing and sintering. The preform is placed in an extrusion die, heated to 450℃~500℃, held for 30min~40min, and then extruded.

[0039] The invention will now be described in detail through the following embodiments and comparative examples.

[0040] Example 1

[0041] A method for preparing reduced graphene oxide / high-entropy alloy reinforced aluminum alloy rods includes the following steps:

[0042] S1. Graphene oxide was prepared by the improved Hummers method: Graphene oxide was dispersed in deionized water to form a graphene oxide suspension with a concentration of 0.04 g / mL. The graphene oxide suspension was added to a hydrothermal reactor lined with polytetrafluoroethylene. After sealing, the reactor was hydrothermally reacted at 180°C for 8 h to obtain reduced graphene oxide, denoted as RGO.

[0043] S2, 1g of high-entropy alloy and 1g of RGO were weighed separately. Using stainless steel grinding balls of three specifications (5mm, 8mm, and 10mm in diameter) with a mass ratio of 3:2:1, the high-entropy alloy and RGO were ball-milled for 5 hours at a speed of 450r / min and a ball-to-material ratio of 10:1 to achieve mechanical bonding. Argon gas was introduced during the ball milling process for protection to prevent oxidation of the high-entropy alloy during mechanized ball milling. Then, 1% of the total mass of the high-entropy alloy and RGO was added as a process inhibitor, n-heptane, to prevent cold welding due to excessive temperature during equipment operation. The ball mill was stopped for 10 minutes every hour of operation. After ball milling, the particles were centrifuged and cleaned with anhydrous ethanol, and then dried to obtain reduced graphene oxide / high-entropy alloy particles.

[0044] S3. Based on the mass of 6061 aluminum alloy powder, 0.1 wt% of reduced graphene oxide / high entropy alloy particles were added to the 6061 aluminum alloy powder. Grinding balls with a mass ratio of 1:3:1, diameters of 10 mm, 8 mm, and 4 mm, and a total mass of 600 g were used. The mixture was ball-milled for 10 h at a speed of 200 r / min and a ball-to-material ratio of 5:1. The total mass of the 6061 aluminum alloy powder and the reduced graphene oxide / high entropy alloy particle powder was 120 g, thus obtaining aluminum-based composite powder.

[0045] S4. The aluminum-based composite powder is loaded into a hot-pressing sintering mold, pressurized at 15MPa and heated to 420℃ for sintering for 60 minutes, and then cooled in the furnace to obtain the preform.

[0046] S5. The preform is placed in an extrusion die, heated to 500°C and held for 30 minutes, and then extruded at an extrusion ratio of 1:16 to obtain a reduced graphene oxide / high entropy alloy reinforced aluminum alloy rod.

[0047] Example 2

[0048] A method for preparing reduced graphene oxide / high-entropy alloy reinforced aluminum alloy rods includes the following steps:

[0049] S1. Graphene oxide was prepared by the improved Hummers method: Graphene oxide was dispersed in deionized water to form a graphene oxide suspension with a concentration of 0.04 g / mL. The graphene oxide suspension was added to a hydrothermal reactor lined with polytetrafluoroethylene. After sealing, the reactor was hydrothermally reacted at 180°C for 8 h to obtain reduced graphene oxide, denoted as RGO.

[0050] S2, 1g of high-entropy alloy and 1g of RGO were weighed separately. Using stainless steel grinding balls of three specifications (5mm, 8mm, and 10mm in diameter) with a mass ratio of 3:2:1, the high-entropy alloy and RGO were ball-milled for 5 hours at a speed of 450r / min and a ball-to-material ratio of 10:1 to achieve mechanical bonding. Argon gas was introduced during the ball milling process for protection to prevent oxidation of the high-entropy alloy during mechanized ball milling. Then, 1% of the total mass of the high-entropy alloy and RGO was added as a process inhibitor, n-heptane, to prevent cold welding due to excessive temperature during equipment operation. The ball mill was stopped for 10 minutes every hour of operation. After ball milling, the particles were centrifuged and cleaned with anhydrous ethanol, and then dried to obtain reduced graphene oxide / high-entropy alloy particles.

[0051] S3. Based on the mass of 6061 aluminum alloy powder, 0.2wt% of reduced graphene oxide / high entropy alloy particles were added to the 6061 aluminum alloy powder. Grinding balls with a mass ratio of 1:3:1, diameters of 10mm, 8mm, and 4mm, and a total mass of 600g were used. The mixture was ball-milled for 10h at a speed of 200r / min and a ball-to-material ratio of 5:1. The total mass of the 6061 aluminum alloy powder and the reduced graphene oxide / high entropy alloy particle powder was 120g, resulting in aluminum-based composite powder.

[0052] S4. The aluminum-based composite powder is loaded into a hot-pressing sintering mold, pressurized at 15MPa and heated to 420℃ for sintering for 60 minutes, and then cooled in the furnace to obtain the preform.

[0053] S5. The preform is placed in an extrusion die, heated to 500°C and held for 30 minutes, and then extruded at an extrusion ratio of 1:16 to obtain a reduced graphene oxide / high entropy alloy reinforced aluminum alloy rod.

[0054] Example 3

[0055] A method for preparing reduced graphene oxide / high-entropy alloy reinforced aluminum alloy rods includes the following steps:

[0056] S1. Graphene oxide was prepared by the improved Hummers method: Graphene oxide was dispersed in deionized water to form a graphene oxide suspension with a concentration of 0.04 g / mL. The graphene oxide suspension was added to a hydrothermal reactor lined with polytetrafluoroethylene. After sealing, the reactor was hydrothermally reacted at 180°C for 8 h to obtain reduced graphene oxide, denoted as RGO.

[0057] S2, 1g of high-entropy alloy and 1g of RGO were weighed separately. Using stainless steel grinding balls of three specifications (5mm, 8mm, and 10mm in diameter) with a mass ratio of 3:2:1, the high-entropy alloy and RGO were ball-milled for 5 hours at a high-energy planetary ball mill speed of 450r / min and a ball-to-material ratio of 10:1 to achieve mechanical bonding. Argon gas was introduced during the ball milling process for protection to prevent oxidation of the high-entropy alloy during mechanized ball milling. Then, 1% of the total mass of the high-entropy alloy and RGO was added as a process inhibitor, n-heptane, to prevent cold welding due to excessive temperature during equipment operation. The ball mill was stopped for 10 minutes every hour of operation. After ball milling, the particles were centrifuged and cleaned with anhydrous ethanol, and then dried to obtain reduced graphene oxide / high-entropy alloy particles.

[0058] S3. Based on the mass of 6061 aluminum alloy powder, 0.3wt% of reduced graphene oxide / high entropy alloy particles were added to the 6061 aluminum alloy powder. Grinding balls with a mass ratio of 1:3:1, diameters of 10mm, 8mm, and 4mm, and a total mass of 600g were used. The mixture was ball-milled for 10h at a speed of 200r / min and a ball-to-material ratio of 5:1. The total mass of the 6061 aluminum alloy powder and the reduced graphene oxide / high entropy alloy particle powder was 120g, resulting in aluminum-based composite powder.

[0059] S4. The aluminum-based composite powder is loaded into a hot-pressing sintering mold, pressurized at 15MPa and heated to 420℃ for sintering for 60 minutes, and then cooled in the furnace to obtain the preform.

[0060] S5. The preform is placed in an extrusion die, heated to 500°C and held for 30 minutes, and then extruded at an extrusion ratio of 1:16 to obtain a reduced graphene oxide / high entropy alloy reinforced aluminum alloy rod.

[0061] To further illustrate the effects of the present invention, comparative examples are also provided, as follows:

[0062] Comparative Example 1

[0063] The difference compared to Example 1 is that reduced graphene oxide / high entropy alloy particles are not added to the aluminum alloy rods; only pure 6061 aluminum alloy is used to prepare the aluminum alloy rods.

[0064] A method for preparing aluminum alloy rods includes the following steps:

[0065] S1. Pure 6061 aluminum powder particles are ball-milled for 10 hours in a high-energy ball mill with a mass ratio of 1:3:1, diameters of 10mm, 8mm and 4mm, and a total mass of 600g, using grinding balls. The ball-to-particle ratio is 5:1 and the mass of the 6061 aluminum alloy matrix is ​​120g, thus obtaining aluminum-based powder.

[0066] S2, the aluminum-based powder is loaded into a hot pressing sintering mold, pressurized at 15MPa and heated to 420℃ for sintering for 60min, and then cooled in the furnace to obtain the preform.

[0067] S3. Place the preform in an extrusion die, heat it to 500°C and hold it for 30 minutes, then extrude it at an extrusion ratio of 1:16 to obtain an aluminum alloy rod.

[0068] Comparative Example 2

[0069] The difference from Example 1 is that reduced graphene oxide is not added to the aluminum alloy rod; instead, only a high-entropy alloy and 6061 aluminum alloy are used to prepare the aluminum alloy rod.

[0070] A method for preparing high-entropy alloy reinforced aluminum alloy rods includes the following steps:

[0071] S1, based on the mass of 6061 aluminum alloy powder, 0.1 wt% high-entropy alloy is added to the 6061 aluminum alloy powder. Grinding balls with a mass ratio of 1:3:1, diameters of 10 mm, 8 mm, and 4 mm, and a total mass of 600 g are used. The high-entropy alloy and 6061 aluminum alloy powder are ball-milled for 10 h at a speed of 200 r / min and a ball-to-material ratio of 5:1. The total mass of 6061 aluminum alloy powder and high-entropy alloy particles is 120 g, thus obtaining aluminum-based composite powder.

[0072] S3, the aluminum-based composite powder is loaded into a hot pressing sintering mold, pressurized at 15MPa and heated to 420℃ for sintering for 60min, and then cooled in the furnace to obtain the preform.

[0073] S4. The preform is placed in an extrusion die, heated to 500°C and held for 30 minutes, and then extruded at an extrusion ratio of 1:16 to obtain a high-entropy alloy reinforced aluminum alloy rod.

[0074] Comparative Example 3

[0075] The difference from Example 1 is that no high-entropy alloy is added to the aluminum alloy rod; instead, only reduced graphene oxide and 6061 aluminum alloy are used to prepare the aluminum alloy rod.

[0076] A method for preparing reduced graphene oxide reinforced aluminum alloy rods includes the following steps:

[0077] S1. Graphene oxide was prepared by the improved Hummers method: Graphene oxide was dispersed in deionized water to form a graphene oxide suspension with a concentration of 0.04 g / mL. The graphene oxide suspension was added to a hydrothermal reactor lined with polytetrafluoroethylene. After sealing, the reactor was hydrothermally reacted at 180°C for 8 h to obtain reduced graphene oxide, denoted as RGO.

[0078] S2, based on the mass of the 6061 aluminum alloy matrix, 0.1 wt% reduced graphene oxide was added to the 6061 aluminum alloy matrix. Grinding balls with a mass ratio of 1:3:1, diameters of 10 mm, 8 mm, and 4 mm, and a total mass of 600 g were used. The mixture was ball-milled for 10 h at a speed of 200 r / min and a ball-to-material ratio of 5:1. The total mass of the 6061 aluminum alloy matrix and the reduced graphene oxide was 120 g, resulting in aluminum-based composite powder.

[0079] S3, the aluminum-based composite powder is loaded into a hot pressing sintering mold, pressurized at 15MPa and heated to 420℃ for sintering for 60min, and then cooled in the furnace to obtain the preform.

[0080] S4. The preform is placed in an extrusion die, heated to 500°C and held for 30 minutes, and then extruded at an extrusion ratio of 1:16 to obtain a reduced graphene oxide reinforced aluminum alloy rod.

[0081] The performance of the aluminum alloy bars provided in Examples 1 to 3 and Comparative Examples 1 to 3 was tested respectively, and the results are as follows.

[0082] Figure 1 This is a SEM image of the reduced graphene oxide / high-entropy alloy particles prepared in Example 1 of this invention. Figure 1 It can be seen that the high-entropy alloy is clearly attached to the surface of the reduced graphene oxide, which proves that the present invention introduces two reinforcing particles, high-entropy alloy and reduced graphene oxide, into the 6061 aluminum alloy matrix.

[0083] Figure 2 The images show the transverse SEM microstructure of the aluminum alloy rods prepared according to this invention, wherein (a) is Comparative Example 1, (b) is Example 1, (c) is Example 2, and (d) is Example 3. Figure 2 It can be seen that in Examples 1 to 3, the reduced graphene oxide / high entropy alloy was used as reinforcing particles and was closely bonded to the 6061 aluminum alloy matrix, and there were no obvious voids or defects in the material.

[0084] Figure 3 The images show the SEM microstructure of the fracture surface morphology of the tensile specimens of the aluminum alloy rods prepared according to this invention. Figure (a) shows Comparative Example 1, Figure (b) shows Example 1, Figure (c) shows Example 2, Figure (d) shows Example 3, Figure (e) shows Comparative Example 3, and Figure (f) shows Comparative Example 2. Figure 3It can be seen that the aluminum alloy rods with reduced graphene oxide / high entropy alloy added in Examples 1 to 3 have smaller fracture dimples. In contrast, Comparative Example 1, without added reinforcing particles, and Comparative Example 2, using only high entropy alloy as reinforcing particles, showed that the reduced fracture dimples promoted the growth and merging of micropores during stretching due to the uneven deformation caused by the strength difference between the HEA and the aluminum alloy matrix. In Comparative Example 3, using only reduced graphene oxide as reinforcing particles, the agglomeration of graphene resulted in larger dimples, leading to a decrease in the mechanical properties of the aluminum alloy rod.

[0085] Figure 4 The XRD analysis results are for the aluminum alloy rods prepared according to this invention. Figure 4 It can be seen that: after adding reduced graphene oxide / high entropy alloy particles to the 6061 aluminum alloy matrix, no Al4C3 peak appeared. That is, the aluminum alloy rod prepared by this invention does not contain a brittle phase that would cause poor mechanical properties. Therefore, the aluminum alloy rod prepared by this invention has better comprehensive mechanical properties.

[0086] Figure 5 This is a graph showing the average Vickers hardness of the aluminum alloy bars prepared in Comparative Examples 1-3 and Examples 1-3 of this invention. Figure 5 It can be seen that, compared with Comparative Example 1, the addition of 0.1% (by weight) of reduced graphene oxide / high-entropy alloy particles to the 6061 aluminum alloy matrix in Example 1 increased the average Vickers hardness of the aluminum alloy rod by 45.7%. Compared with Comparative Example 2, the average Vickers hardness of the aluminum alloy rod in Example 1 increased by 9.3%. Compared with Comparative Example 3, the average Vickers hardness of the aluminum alloy rod in Example 1 increased by 58.4%.

[0087] Figure 6 The true stress-strain curves of the aluminum alloy bars prepared in Comparative Examples 1, 3, and Examples 1-3 of this invention are shown in the tensile test. Figure 6 It can be seen that, in Example 1, the aluminum alloy rod prepared with the best comprehensive mechanical properties is when the amount of reduced graphene oxide / high entropy alloy added is 0.1 wt.%.

[0088] Figure 7 This is a bar chart showing the tensile strength, yield strength, and elongation of the aluminum alloy bars prepared in Comparative Example 1 and Examples 1-3 of this invention. Figure 7 It can be seen that the aluminum alloy bar prepared in Example 1 has the best comprehensive mechanical properties, with tensile strength increased by 36.2%, yield strength increased by 46.5%, and elongation increased by 2.56%.

[0089] Compared with the performance of the aluminum alloy bars prepared in the examples, the performance of the aluminum alloy bars obtained in Comparative Examples 1 to 3 is inferior. The main reason for this is that:

[0090] In Comparative Example 1, the simple 6061 aluminum alloy bar has no reinforcing particles in the matrix, resulting in large internal grains and no dislocation pile-up after hot extrusion. During the stretching process, the grain boundaries are prone to slippage, which leads to a decrease in mechanical properties.

[0091] In Comparative Example 2, only high-entropy alloys were added as reinforcing particles to the 6061 aluminum alloy matrix. Due to the local agglomeration of the high-entropy alloys, the internal stress distribution in the matrix was uneven, which made the material tend to become brittle and thus reduced the mechanical properties of the aluminum alloy rod.

[0092] In Comparative Example 3, only reduced graphene oxide was added as reinforcing particles to the 6061 aluminum alloy matrix. Due to the local agglomeration of the reduced graphene oxide, the mechanical properties of the aluminum alloy rod were reduced.

[0093] In summary, this invention uses a mechanical ball milling method to attach a high-entropy alloy to the surface of reduced graphene oxide. Then, using powder metallurgy, the reduced graphene oxide / high-entropy alloy particles are hot-pressed and sintered with aluminum alloy powder, followed by extrusion to obtain aluminum alloy rods reinforced with reduced graphene oxide / high-entropy alloy. The hot-pressing pre-sintering creates a preliminary metallurgical effect on the surface of the metal billet, thereby improving quality issues such as wrinkles, peeling, and low density during subsequent hot extrusion. The combination of a high-entropy alloy formed from Al, Fe, Ni, Cr, and Co, along with reduced graphene oxide as reinforcing particles, and the aluminum alloy composite, further improves the overall mechanical properties of the aluminum alloy rods and reduces microscopic defects, thus solving the technical problem of poor mechanical properties in aluminum alloy rods.

[0094] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing reduced graphene oxide / high-entropy alloy reinforced aluminum alloy rods, characterized in that, Includes the following steps: High-entropy alloy was loaded onto reduced graphene oxide by mechanical ball milling in a protective atmosphere to obtain reduced graphene oxide / high-entropy alloy particles; the high-entropy alloy was composed of Al, Fe, Ni, Cr and Co in a weight ratio of 0.5:1:1:1:1; the mass ratio of reduced graphene oxide to high-entropy alloy was 1:0.8~1.

2. The mechanical ball milling process uses stainless steel grinding balls with diameters of 5mm, 8mm, and 10mm and a mass ratio of 3:2:

1. The high-entropy alloy and reduced graphene oxide are ball-milled at a speed of 400r / min to 450r / min and a ball-to-material ratio of 10 to 20:1 for 4 hours to 6 hours. Using the reduced graphene oxide / high entropy alloy particles as reinforcing particles and aluminum alloy powder as the matrix, aluminum alloy rods reinforced with reduced graphene oxide / high entropy alloy are obtained by hot pressing and sintering using powder metallurgy. The mass of the reduced graphene oxide / high entropy alloy particles is 0.1% to 0.3% of the mass of the aluminum alloy powder. During hot pressing and sintering, the temperature is raised to 420℃ to 450℃, the pressure is raised to 10MPa to 15MPa, and the hot pressing and sintering time is 60min to 70min.

2. The method for preparing reduced graphene oxide / high-entropy alloy reinforced aluminum alloy rods according to claim 1, characterized in that, During ball milling, add 1% to 3% of the total mass of reduced graphene oxide and high-entropy alloy in n-heptane.

3. The method for preparing reduced graphene oxide / high-entropy alloy reinforced aluminum alloy rods according to claim 1, characterized in that, Before hot pressing and sintering, the reduced graphene oxide / high entropy alloy particles are mixed with aluminum alloy powder and ball-milled for 8 to 10 hours at a speed of 200 rpm to 240 rpm and a ball-to-material ratio of 5 to 6:

1.

4. The method for preparing reduced graphene oxide / high-entropy alloy reinforced aluminum alloy rods according to claim 1, characterized in that, After hot pressing and sintering, a preform is obtained. The preform is placed in an extrusion mold, heated to 450℃~500℃, held for 30min~40min, and then extruded.

5. A reduced graphene oxide / high entropy alloy reinforced aluminum alloy rod prepared by the preparation method according to any one of claims 1 to 4.

Images