Preparation method of graphene and silicon carbide hybrid reinforced aluminum matrix composite

Abstract

The present invention discloses a graphene and silicon carbide hybrid reinforced aluminum matrix composite material and a preparation method thereof, which relates to the technical field of composite material preparation, and includes the following steps: Step S1: Under the protection atmosphere of argon, nano silicon carbide particles, aluminum powder and a process control agent are mixed and ball-milled, and then graphene nanosheets are added, and after variable-speed ball-milling, a uniform graphene / nano silicon carbide / aluminum composite powder is obtained; Step S2: After pre-pressing the graphene / nano silicon carbide / aluminum composite powder, through vacuum spark plasma sintering and extrusion molding, a graphene and silicon carbide hybrid reinforced aluminum matrix composite material with a quasi-connected and layered distribution is obtained. The present invention effectively prevents excessive damage to the graphite nanosheet structure and improves its dispersion uniformity by adopting the method of pre-mixing nano silicon carbide particles and aluminum powder at the same speed and then adding graphene nanosheets for variable-speed ball-milling, and reduces interfacial adverse reactions through vacuum spark plasma sintering.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material preparation, and in particular, to a method for preparing a graphene and silicon carbide hybrid reinforced aluminum matrix composite material. Background Art

[0002] With the increasing popularity of the application of aluminum matrix composites, hybrid reinforced aluminum matrix composites show great advantages. They have excellent comprehensive properties such as low density, high strength and stiffness, high toughness, good wear resistance and fatigue resistance, and can be widely used in industries such as aerospace, energy, ocean engineering and transportation. Especially with the continuous in-depth research, when graphene nanoplatelets (GNP) and nano-silicon carbide particles (SiCnp) are simultaneously used as reinforcement phases and added to the matrix, the material can obtain more excellent properties than the aluminum matrix composite material with a single reinforcement phase under the condition of higher strength.

[0003] However, for the preparation of GNP and SiCnp hybrid reinforced aluminum matrix composites, there are usually the following problems at the present stage: 1) GNP-Al interfacial reaction problem: At present, the main preparation methods of GNP and SiCnp hybrid reinforced aluminum matrix composites are stir casting method and powder metallurgy method. When using the stir casting method, GNP is in direct contact with the molten metal at high temperature, and the interfacial reaction is difficult to control; currently, in the powder metallurgy method, the consolidation method mainly uses hot pressing sintering, and the hot pressing time is long, resulting in a serious interfacial reaction between GNP and Al that is unfavorable to the material properties; 2) GNP structure damage problem: At present, in the methods for preparing GNP and SiCnp hybrid reinforced aluminum matrix composites by powder metallurgy, the method of first preparing the GNP-SiC hybrid reinforcement phase and then mixing it evenly with the matrix is adopted. However, due to the very high hardness of SiC, the GNP structure is easily damaged to a greater extent during the mixing process of SiC and GNP, resulting in the formation of a brittle phase Al4C3 when GNP reacts with the matrix during the subsequent hot working process; 3) The dispersion uniformity of the reinforcement phase: The dispersion of nano-reinforcement phases is difficult, and whether it is uniform is the key to the quality of the material properties. Therefore, how to achieve uniform dispersion of the reinforcement phase in the matrix is very crucial. Summary of the Invention

[0004] The problem solved by the present invention is how to improve at least one of the problems that the interfacial reaction is difficult to control, the structure of graphite nanosheets is damaged too much, and the dispersion difficulty is large.

[0005] To solve the above problems, the present invention provides a method for preparing a graphene and silicon carbide hybrid reinforced aluminum matrix composite material, comprising the following steps:

[0006] Step S1: Under the protective atmosphere of argon, mix nano-silicon carbide particles, aluminum powder and a process control agent, and then ball-mill them. After that, add graphene nanosheets and perform variable-speed ball-milling to obtain a uniform graphene / nano-silicon carbide / aluminum composite powder.

[0007] Step S2: After pre-pressing the graphene / nano-silicon carbide / aluminum composite powder, perform vacuum discharge plasma sintering and extrusion molding to obtain a quasi-connected and layered-distributed graphene and silicon carbide hybrid-reinforced aluminum matrix composite.

[0008] Further, in step S1, the process control agent is stearic acid, and the volume fractions of the nano-silicon carbide particles, the graphene nanosheets, the aluminum powder and the stearic acid are 0.3 - 1.5 vol%, 3 - 5 vol%, 90.6 - 95.3 vol% and 1.4 - 2.9 vol% respectively.

[0009] Further, in step S1, the rotation speed of the ball-milling is 200 rpm, and the ball-milling time is 7 - 13 h.

[0010] Further, in step S1, the variable-speed ball-milling includes:

[0011] Ball-mill for 4 - 10 h under the condition that the ball-milling rotation speed is 100 - 200 rpm, and then ball-mill for 1 - 6 h under the condition that the ball-milling rotation speed is 300 - 400 rpm.

[0012] Further, in step S1, the grinding balls are stainless steel balls, and the ball-to-material ratio is (10 - 15):1.

[0013] Further, in step S2, after pre-pressing the graphene / nano-silicon carbide / aluminum composite powder, it includes:

[0014] After loading the graphene / nano-silicon carbide / aluminum composite powder into a mold, apply bi-directional pressure; the pressure value is 5 - 10 MPa, and the pre-pressing time is 10 mins.

[0015] Further, in step S2, the vacuum discharge plasma sintering includes:

[0016] Under the condition that the vacuum degree is 1×10 -3 Pa - 1×10 -5 Pa, heat the pre-pressed graphene / nano-silicon carbide / aluminum composite powder to the sintering temperature, and apply pressure. After heat preservation and pressure holding, naturally cool down to room temperature; the sintering temperature is 450 - 550 °C, the applied pressure is 30 - 50 MPa, and the heat preservation and pressure holding time is 5 - 10 mins.

[0017] Further, in step S2, the extrusion molding includes:

[0018] After heating and holding for a period of time in an extrusion die, it is extruded into a bar; wherein the heating temperature is 400-500 °C, the holding time is 90 mins, and the extrusion ratio is one of 9:1, 16:1, and 25:1.

[0019] Furthermore, in step S1, the particle size of the nano silicon carbide particles is 20-80 nm, the particle size of the aluminum powder is 5-25 μm, and the thickness of the graphene nanosheets is 5-10 nm.

[0020] The beneficial effects of the preparation method of the graphene and silicon carbide hybrid reinforced aluminum matrix composite material of the present invention compared with the prior art include:

[0021] 1. In the present invention, by adopting the method of pre-mixing nano silicon carbide particles and aluminum powder by high-speed ball milling at the same speed and then adding graphene nanosheets for variable-speed ball milling, the nano silicon carbide particles and aluminum powder are pre-mixed at the same speed, which not only realizes the uniform dispersion of the nano silicon carbide particles, but also makes the aluminum powder pre-deformed, changing from spherical aluminum powder with difficult attachment of graphene nanosheets to flaky aluminum powder with easier attachment of graphene nanosheets, which is beneficial to the uniform coating of graphene nanosheets on the surface of flaky aluminum powder in the later stage. At the same time, it avoids the drawback that when graphene nanosheets and nano silicon carbide particles are ball milled with aluminum powder at the same time in the past, the hard silicon carbide particles damage the flexible graphene structure, resulting in the deterioration of the material properties, improves the structural integrity of the graphene nanosheets, and maintains the excellent mechanical and physical properties of the graphene nanosheets.

[0022] 2. The present invention also mixes graphene nanosheets, nano silicon carbide particles, and aluminum powder evenly by variable-speed ball milling, first making the graphene nanosheets uniformly attach to the surface of flaky aluminum powder, and then embedding the graphene sheets into the aluminum matrix, which not only improves the bonding strength of the material, prevents further structural damage to the graphene nanosheets, but also promotes the good effect of the uniform dispersion of the graphene nanosheets in the aluminum matrix, avoiding the problem of large structural damage of the graphene nanosheets in the method of enhancing the uniform dispersion by ball milling at the same speed for a long time in the prior art.

[0023] 3. In order to further prevent the uneven dispersion and isolated distribution of the graphene nanosheets, the present invention combines vacuum discharge plasma sintering and extrusion molding, making the graphene in the aluminum matrix show a quasi-connected and layered distribution. At the same time, the added nano silicon carbide particles increase the matrix flow stress, promote the rotation of the graphene nanosheets and their distribution along the streamline direction; through the synergistic strengthening of the reinforcing phases, the graphene and silicon carbide hybrid reinforced aluminum matrix composite material has good uniform plastic deformation ability while improving strength and toughness.

[0024] 4. The preparation method described in the present invention adopts vacuum discharge plasma sintering, which greatly shortens the hot pressing time, effectively enhances the controllability of the interfacial reaction between graphene nanosheets and aluminum powder, and reduces the interfacial reaction that is unfavorable to the material properties.

[0025] To solve the above problems, the present invention also provides a graphene and silicon carbide hybrid reinforced aluminum matrix composite material, which is prepared according to the preparation method of the graphene and silicon carbide hybrid reinforced aluminum matrix composite material.

[0026] The beneficial effects of the graphene and silicon carbide hybrid reinforced aluminum matrix composite material provided by the present invention are the same as those of the preparation method of the graphene and silicon carbide hybrid reinforced aluminum matrix composite material, and will not be elaborated here. Brief Description of the Drawings

[0027] Figure 1 It is the preparation flow chart of the graphene and silicon carbide hybrid reinforced aluminum matrix composite material described in the present invention;

[0028] Figure 2 It is the XRD composition analysis curve of the sintered sample of the composite material prepared in Example 1 of the present invention;

[0029] Figure 3 It is the scanning electron microscope (SEM) image of the pre-mixed powder of nano-silicon carbide particles and aluminum powder in Example 1 of the present invention;

[0030] Figure 4 It is Figure 3 The enlarged view of the framed area;

[0031] Figure 5 It is the scanning electron microscope (SEM) image of the pre-mixed powder of nano-silicon carbide particles and aluminum powder in Comparative Example 1;

[0032] Figure 6 It is Figure 5 The enlarged view of the framed area

[0033] Figure 7 It is the scanning electron microscope (SEM) image of the pre-mixed powder of nano-silicon carbide particles and aluminum powder in Comparative Example 2;

[0034] Figure 8 It is the Raman spectrum analysis diagram of the composite powders in Example 1 of the present invention and Comparative Examples 1 and 2;

[0035] Figure 9 It is the scanning electron microscope (SEM) image of the sintered sample of the composite material prepared in Example 1 of the present invention;

[0036] Figure 10 It is the scanning electron microscope (SEM) image of the sintered sample of the composite material prepared in Comparative Example 1;

[0037] Figure 11 SEM image of the sintered sample of the composite material prepared in Comparative Example 2;

[0038] Figure 12 SEM image of the extruded sample of the composite material prepared in Example 1 of the present invention

[0039] SEM);

[0040] Figure 13 is Figure 12 The enlarged view within the frame area;

[0041] Figure 14 WDS spectrum composition distribution map of the extruded samples prepared in Examples 1, 2, and 3 of the present invention;

[0042] Figure 15 Tensile mechanical property curves of the extruded samples prepared in Examples 1, 2, and 3 of the present invention and Comparative Examples 3 and 4. Detailed implementation manners

[0043] The present invention will be further described in detail below with reference to the accompanying drawings: This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation manners are given, but the protection scope of the present invention is not limited to the following embodiments.

[0044] The embodiment of the present invention provides a method for preparing a graphene and silicon carbide hybrid reinforced aluminum matrix composite material, comprising the following steps:

[0045] Step S1: Under the protection atmosphere of argon, nano-silicon carbide particles, aluminum powder, and a process control agent are mixed and ball-milled, and then graphene nanosheets are added, and after variable-speed ball-milling, a uniform graphene / nano-silicon carbide / aluminum composite powder is obtained;

[0046] Step S2: After pre-pressing the graphene / nano-silicon carbide / aluminum composite powder, it is subjected to vacuum spark plasma sintering and extrusion molding to obtain a graphene and silicon carbide hybrid reinforced aluminum matrix composite material with a quasi-connected and layered distribution.

[0047] The preparation method of a graphene and silicon carbide hybrid reinforced aluminum-based composite material described in an embodiment of the present invention adopts a method of pre-mixing nano-silicon carbide particles and aluminum powder by ball milling at the same speed, and then adding graphene nanosheets and variable speed ball milling, so that the nano-silicon carbide particles and aluminum powder are pre-mixed at the same speed, which not only achieves uniform dispersion of the nano-silicon carbide particles, but also pre-deforms the aluminum powder, transforming it from spherical aluminum powder to which graphene nanosheets are difficult to attach to flaky aluminum powder to which graphene nanosheets are easier to attach, which is beneficial to the later uniform coating of the graphene nanosheets on the surface of the flaky aluminum powder, and at the same time avoids the disadvantage that when the graphene nanosheets and nano-silicon carbide particles are ball-milled with aluminum powder at the same time, the hard silicon carbide particles damage the flexible graphene structure, resulting in deterioration of material properties, thereby improving the structural integrity of the graphene nanosheets and maintaining the excellent mechanical and physical properties of the graphene nanosheets.

[0048] The embodiment of the present invention also mixes the graphene nanosheets with nano silicon carbide particles and aluminum powder evenly through variable speed ball milling, first making the graphene nanosheets evenly adhere to the surface of the flaky aluminum powder, and then embedding the graphene sheets into the aluminum matrix, which not only improves the bonding strength of the material and prevents the graphene nanosheets from further structural damage, but also promotes the good effect of uniform dispersion of the graphene nanosheets in the aluminum matrix, avoiding the problem of severe structural damage to the graphene nanosheets in the method of enhancing phase uniform dispersion by ball milling at the same speed for a long time in the prior art.

[0049] In order to further prevent the uneven dispersion and isolated distribution of graphene nanosheets, the embodiment of the present invention combines vacuum discharge plasma sintering and extrusion molding to make the graphene quasi-connected and layered in the aluminum matrix. At the same time, the added nano silicon carbide particles increase the rheological stress of the matrix to promote the rotation of the graphene nanosheets and the distribution along the streamline direction. Through the synergistic reinforcement of the reinforcing phase, the graphene and silicon carbide hybrid reinforced aluminum-based composite material has good uniform plastic deformation ability while improving strength and toughness.

[0050] The preparation method described in the embodiment of the present invention greatly shortens the hot pressing time by adopting the vacuum discharge plasma sintering method, effectively enhances the controllability of the interface reaction between the graphene nanosheets and the aluminum powder, and reduces the interface reaction that is unfavorable to the material properties.

[0051] Specifically, in step S1, a planetary ball mill is used for ball milling. After the nano-silicon carbide particles, aluminum powder and process control agent are mixed and fully ball milled, the ball mill is placed in a vacuum glove box to complete the addition of graphene nanosheets, and then the ball mill is taken out of the vacuum glove box and placed in a planetary ball mill for variable speed ball milling. In this way, the powder is prevented from reacting with air and affecting the performance of the later material.

[0052] Specifically, in step S2, the graphene / silicon carbide nanocomposite / aluminum composite powder obtained in step S1 is loaded into a mold. After pre-pressing, it is sintered by vacuum discharge plasma and cooled with the furnace to obtain a blank of graphene and silicon carbide hybrid reinforced aluminum matrix composite. The blank is placed in an extrusion mold, and by controlling the extrusion temperature and extrusion coefficient, a graphene and silicon carbide hybrid reinforced aluminum matrix composite with a quasi-connected and layered distribution is obtained. Thus, through pre-pressing and vacuum discharge plasma sintering, the preparation time of the blank of the graphene and silicon carbide hybrid reinforced aluminum matrix composite is greatly shortened, the preparation efficiency is improved, and the interfacial adverse reaction is reduced.

[0053] In some embodiments, in step S1, the process control agent is stearic acid, and the volume fractions of the silicon carbide nanoparticles, the graphene nanosheets, the aluminum powder, and the stearic acid are 0.3 - 1.5 vol%, 3 - 5 vol%, 90.6 - 95.3 vol%, and 1.4 - 2.9 vol%, respectively.

[0054] Thus, by controlling the contents of the silicon carbide nanoparticles, the aluminum powder, and the graphene nanosheets, the structural damage and interfacial reaction of the graphene are reduced, the dispersion uniformity of the reinforcing phase is improved, and at the same time, it is beneficial to improve the performance of the graphene and silicon carbide hybrid reinforced aluminum matrix composite.

[0055] In some embodiments, in step S1, the rotation speed of the ball milling is 200 rpm, and the ball milling time is 7 - 13 h. Thus, by ball milling the silicon carbide nanoparticles and the aluminum powder at the same rotation speed for a long time and sufficiently, the silicon carbide nanoparticles and the aluminum powder are uniformly mixed, and at the same time, the aluminum powder is pre-deformed, which is beneficial to improving the dispersion uniformity of the reinforcing phase.

[0056] In some embodiments, in step S1, the variable-speed ball milling includes:

[0057] Ball milling for 4 - 10 h under the condition that the ball milling rotation speed is 100 - 200 rpm, and then ball milling for 1 - 6 h under the condition that the ball milling rotation speed is 300 - 400 rpm.

[0058] Specifically, during the ball milling process of this embodiment, every 1 h interval, the rotation is stopped for 30 min to prevent excessive cold welding of aluminum powder caused by too long continuous ball milling time and too high temperature rise. In this embodiment, first, low-speed ball milling is used to uniformly attach graphene nanosheets to the surface of flaky aluminum powder, and then high-speed ball milling is used to embed the graphene nanosheets into the aluminum matrix to improve the bonding strength. Compared with the method of long-time ball milling at the same rotation speed in the prior art to enhance the uniform dispersion of phases, in this embodiment, low-speed ball milling is first used to disperse the graphene nanosheets while protecting the structure of the graphene nanosheets. Then, by reducing the time of high-speed ball milling, while achieving a good uniform dispersion effect, the degree of structural damage to the graphene is controlled. Thus, the structural degree of the graphene nanosheets during the ball milling process is further reduced, and the formation of adverse interfacial reactants during the subsequent heating process is avoided.

[0059] In some embodiments, in step S1, the grinding balls are stainless steel balls, and the ball-to-material ratio includes (10 - 15) : 1. Thus, the grinding balls have good stability, and the ball-to-material ratio can achieve sufficient grinding to obtain uniform dispersion of the reinforcing phase and good grinding effect.

[0060] In some embodiments, in step S2, after pre-pressing the graphene / nano-silicon carbide / aluminum composite powder, it includes:

[0061] After loading the graphene / nano-silicon carbide / aluminum composite powder into the mold, two-way pressure is applied; the pressure value is 5 - 10 MPa, and the pre-pressing time is 10 mins. Among them, the inner surface of the mold can be coated with a release agent or attached with graphite paper coated with a release agent, which can reduce the adhesion of the powder to the inner wall of the mold during the sintering process and facilitate demolding. Thus, the preparation efficiency is improved and the material loss is reduced.

[0062] In some embodiments, in step S2, the vacuum discharge plasma sintering includes:

[0063] Under the condition of a vacuum degree of 1×10 -3 Pa - 1×10 -5 Pa, the pre-pressed graphene / nano-silicon carbide / aluminum composite powder is heated to the sintering temperature and pressurized. After holding the pressure and temperature, it is naturally cooled to room temperature; the sintering temperature is 450 - 550 °C, the applied pressure is 30 - 50 MPa, and the holding pressure and temperature time is 5 - 10 mins.

[0064] Specifically, compared with the existing stirring casting method and powder metallurgy method, the plasma sintering method has the characteristics of short time and high efficiency, and can effectively solve the problem of adverse interfacial reactions between materials.

[0065] In some embodiments, in step S2, the extrusion molding includes:

[0066] After heating and holding for a period of time in an extrusion die, it is extruded into a bar; the heating temperature is 400 - 500 °C, the holding time is 90 mins, and the extrusion ratio is one of 9:1, 16:1, and 25:1.

[0067] Specifically, during the extrusion molding process, a composite lubricant obtained by mixing 46# hydraulic oil and graphite powder with a particle size less than 150 mesh in a mass ratio of 1:1 can be used as a lubricating material and applied to the inner surface of the extrusion die to reduce the friction between the billet and the die.

[0068] Thus, in this embodiment, by controlling the extrusion ratio, the billet is extruded and formed, enabling graphene to achieve a quasi-connected and layered distribution in the aluminum matrix. At the same time, it synergistically enhances the performance of the aluminum matrix material with silicon carbide, achieving more excellent mechanical properties of the material.

[0069] In some embodiments, in step S1, the particle size of the nano silicon carbide particles is 20 - 80 nm, the particle size of the aluminum powder is 5 - 25 μm, and the thickness of the graphene nanosheets is 5 - 10 nm. Thus, by optimizing the particle size and thickness, it is beneficial to the preparation and performance improvement of the graphene and silicon carbide hybrid reinforced aluminum matrix composite under the premise of excellent dispersibility and synergistic reinforcement of the reinforcing phase.

[0070] An embodiment of the present invention also provides a graphene and silicon carbide hybrid reinforced aluminum matrix composite, which is prepared according to the preparation method of the graphene and silicon carbide hybrid reinforced aluminum matrix composite.

[0071] The beneficial effects of the graphene and silicon carbide hybrid reinforced aluminum matrix composite provided by the embodiment of the present invention are the same as those of the preparation method of the graphene and silicon carbide hybrid reinforced aluminum matrix composite, and will not be elaborated here.

[0072] The present invention will be explained in detail below with reference to the embodiments.

[0073] Example 1

[0074] The preparation method of the graphene and silicon carbide hybrid reinforced aluminum matrix composite in this embodiment is as follows:

[0075] Step S1: Select pure aluminum powder with a particle size of 5 - 25 μm, the thickness of the graphene nanosheets is 5 - 10 nm, the average diameter is 1.6 μm, and the particle size of the nano silicon carbide particles is 20 - 80 nm. Among them, the volume fraction of the aluminum powder is 93.5 vol%, the volume fraction of the graphene nanosheets is 3.0 vol%, the volume fraction of the nano silicon carbide particles is 1.5 vol%, and stearic acid with a volume fraction of 2.0 vol% is used as a ball milling process control agent;

[0076] Add nano - silicon carbide particles, aluminum powder, and stearic acid into a 500 - ml planetary ball - milling jar. Fill the ball - milling jar with argon. Among them, the ball - to - powder ratio is 15:1, the ball - milling speed is 200 rpm, and the ball - milling time is 10 h. Then add the prepared graphene nanosheets and perform variable - speed ball - milling under an argon environment. The ball - to - powder ratio is 15:1. First, ball - mill at a low speed of 100 rpm for 8 h, and then ball - mill at a high speed of 300 rpm for 2 h to obtain a uniform graphene / nano - silicon carbide / aluminum composite powder;

[0077] Step S2: Load the uniformly mixed graphene / nano - silicon carbide / aluminum composite powder into the required mold. First, cold - press at 5 MPa for 10 mins, and then perform spark plasma sintering (SPS) under vacuum to obtain a composite material blank. The SPS parameters are as follows: heat up with the furnace before 450 °C, heat up to 530 °C within 90 s after 450 °C, the sintering temperature is 530 °C, apply a pressure of 40 MPa, and keep the temperature and pressure for 5 min to obtain a composite material blank;

[0078] Then load the obtained composite material blank into an extrusion mold for pre - heating, heat it to 490 °C, keep it at this temperature for 90 mins, and extrude it into a composite material rod with an extrusion ratio of 25:1 to obtain a graphene and silicon carbide hybrid - reinforced aluminum - matrix composite material with quasi - connected and layered distributions.

[0079] Perform mechanical property tests on the graphene and silicon carbide hybrid - reinforced aluminum - matrix composite material with quasi - connected and layered distributions prepared in Example 1. After testing, the tensile strength is 255.28 MPa, the yield strength is 177.49 MPa, and the elongation is 3.15%. As Figure 1 shown in the XRD composition analysis curve of the extruded - state sample, no interfacial reaction product Al4C3 is found.

[0080] Figure 2 This is the XRD composition analysis curve of the sintered - state sample of the composite material prepared in Example 1 of the present invention; it can be seen from the figure that there is no appearance of the Al4C3 peak, which can indicate that there is no serious interfacial reaction between GNP and Al during the ball - milling process, and no obvious generation of Al4C3 is found. Reducing the generation of the brittle phase of Al4C3 helps the graphene and silicon carbide hybrid - reinforced aluminum - matrix composite material achieve a better strengthening effect.

[0081] Comparative Example 1

[0082] The specific steps of the preparation method of the graphene and silicon carbide hybrid - reinforced aluminum - matrix composite material in this comparative example are the same as those in Example 1, except that in Step S1, the ball - milling time of nano - silicon carbide particles and aluminum powder at a speed of 200 rpm is 5 h.

[0083] Among them, the distribution of silicon carbide on the surface of the pre - mixed powder obtained by ball - milling nano - silicon carbide particles and aluminum powder in Example 1 is asFigure 3 and Figure 4 As shown in Figure 4 , no obvious agglomerated silicon carbide particles were found on the surface of the pre-mixed aluminum flakes in Example 1. As Figure 5 and Figure 6 shown, obvious agglomerated silicon carbide particles existed on the surface of the aluminum particles in Comparative Example 1, indicating that the nano-silicon carbide particles did not reach uniform dispersion under the set pre-ball milling time in Comparative Example 1.

[0084] Comparative Example 2

[0085] The specific steps of the preparation method of the graphene and silicon carbide hybrid reinforced aluminum matrix composite material in this comparative example are the same as those in Example 1, except that in step S1, the ball milling time of the nano-silicon carbide particles and aluminum powder is 15 h at a rotation speed of 200 rpm.

[0086] The thickness of the aluminum flakes in Comparative Example 2 increased significantly, and severe cold welding and stacking occurred. As Figure 7 shown, the cold welding phenomenon of the aluminum flakes in Comparative Example 2 was severe, which reduced the area where GNPs could adhere, resulting in more agglomeration of the reinforcing phase. At the same time, it would also cause an increase in the pore content and a decrease in the density of the composite material, indicating that the process adopted in Comparative Example 2 was not conducive to the uniform fraction of the reinforcing phase and the improvement of the density of the composite material.

[0087] Specifically, Figure 3 and Figure 4 are the SEM micrographs of the pre-mixed powder obtained by ball milling the nano-silicon carbide particles and aluminum powder for 10 h at a ball milling speed of 200 rpm in Example 1. Figure 5 and Figure 6 are the SEM micrographs of the pre-mixed powder obtained by ball milling the nano-silicon carbide particles and aluminum powder for 5 h at a ball milling speed of 200 rpm in Comparative Example 1. Figure 7 is the SEM micrograph of the pre-mixed powder obtained by ball milling the nano-silicon carbide particles and aluminum powder for 15 h at a ball milling speed of 200 rpm in Comparative Example 2. As the ball milling time increased, the composite powder underwent cold welding, gradually changing from the initial spherical particles to flaky particles, and finally experiencing the phenomenon of cold welding and then fragmentation. From Figure 5 and Figure 6 it can be seen that after the pre-ball milling time was 5 h, the spherical aluminum powder changed into elliptical aluminum particles, and a layer of silicon carbide particles was distributed on their surface. At a magnification, it could be observed that nano-silicon carbide particle agglomerates were unevenly distributed on the surface of the aluminum particles; when the pre-ball milling time reached 10 h, as can be seen from Fig. 4, the aluminum powder was cold-welded into flakes, and the diameter of the flaky aluminum powder could reach more than 100 μm, and the size distribution of the flaky aluminum powder was uniform. The nano-silicon carbide particles on the surface of the aluminum flakes were evenly distributed and the silicon carbide agglomeration was significantly reduced. When the ball milling time reached 15 h, as Figure 7 shown, the aluminum flakes were severely cold-welded and stacked, with a thickness of up to dozens of micrometers, and partial cold welding and fragmentation occurred, and the particle size distribution was uneven.

[0088] Figure 8 The Raman spectrum (Raman) analysis of the composite powder in Example 1 and Comparative Examples 1 and 2. It can be seen that the pre-milling time of nano-silicon carbide particles and aluminum powder affects the subsequent ball milling mixing effect of nano-silicon carbide particles and aluminum powder pre-mixed powder and graphene nanosheets. As can be seen from the figure, when the pre-milling time is 10h, the damage degree of GNP is the smallest. When the pre-milling time of aluminum powder and nano-silicon carbide particles is 5h, the silicon carbide hard particles have not been mixed evenly, and there are many nano-silicon carbide particles agglomerated and distributed on the surface of aluminum particles. In the process of ball milling with GNP, due to the high hardness of nano-silicon carbide particles, the structure of GNP is damaged; as the ball milling time increases, the nano-silicon carbide particles are further dispersed, and the aluminum particles are cold welded. Some nano-silicon carbide particles are cold welded into the interior of the aluminum particles, reducing the damage to GNP; when the ball milling time is 15h, the aluminum particles are severely cold welded, the surface is smooth, and a multi-layer stacking phenomenon occurs, which reduces the area where GNP can be attached, so that it cannot be well combined with the aluminum particles.

[0089] Figure 9 , 10 1 and 11 are SEM morphology images of the sintered samples of the composite materials prepared in Example 1, Comparative Example 1 and Comparative Example 2, respectively. It can be seen from the figure that the surface GNP of the sintered sample in Example 1 is well combined with the matrix, and the occurrence of holes and cracks is the least, and no obvious cracks and holes appear; the ball-milled powder in Comparative Example 2 has the most holes after sintering, and the cold welding and stacking of aluminum sheets are serious due to the long ball-milling time. The morphology of the ball-milled powder is directly related to the quality of the sintered sample.

[0090] Figure 12 and Figure 13 This is the SEM morphology of the interface of the extruded sample of the composite material prepared in Example 1 along the extrusion direction. Figure 9 Compared with the sintered state, the material is further densified, and the reinforcing phases such as graphene nanosheets are further dispersed. From the enlarged image of the yellow line dotted frame, it can be observed that the graphene nanosheets are distributed in streamlined layers along the extrusion direction.

[0091] In summary, if Figure 8 Raman spectroscopy analysis shows that the graphene structure in Example 1 has the least degree of damage. Figure 9 , 10 As shown in Figures 1 and 11, when the pre-milling time is 10 h, the reinforcement phase in the sintered sample has good distribution uniformity and the porosity is the lowest. Figure 12 and Figure 13 As shown, in Example 1, after the hot extrusion molding process, the reinforcement phase is further dispersed and distributed in a streamlined shape.

[0092] Example 2

[0093] The preparation method of the graphene and silicon carbide hybrid reinforced aluminum matrix composite material in this embodiment is as follows:

[0094] Step S1: Select pure aluminum powder with a particle size of 5 - 25 μm, the thickness of graphene nanosheets is 5 - 10 nm, the average diameter is 1.6 μm, and the particle size of nano silicon carbide particles is 20 - 80 nm. Among them, the volume fraction of aluminum powder is 94.1 vol%, the volume fraction of graphene nanosheets is 3.0 vol%, the volume fraction of nano silicon carbide particles is 0.9 vol%, and stearic acid with a volume fraction of 2.0 vol% is used as the ball milling process control agent;

[0095] Add the nano silicon carbide particles, aluminum powder, and stearic acid into a 500 ml planetary ball milling tank, and fill the ball milling tank with argon. Among them, the ball-to-powder ratio is 15:1, the ball milling speed is 200 rpm, and the ball milling time is 10 h. Then add the prepared graphene nanosheets, and perform variable-speed ball milling in an argon environment. The ball-to-powder ratio is 15:1. First, ball mill at a low speed of 100 rpm for 8 h, and then ball mill at a high speed of 300 rpm for 2 h to obtain a uniform graphene / nano silicon carbide / aluminum composite powder;

[0096] Step S2: Load the uniformly mixed graphene / nano silicon carbide / aluminum composite powder into the required mold, first cold press at 5 MPa for 10 mins, and then perform vacuum spark plasma sintering (SPS) to obtain a composite material blank. The SPS parameters are as follows: heat up with the furnace before 450 °C, heat up to 530 °C within 90 s after 450 °C, the sintering temperature is 530 °C, apply a pressure of 40 MPa, keep warm and press for 5 min to obtain a composite material blank; then load the prepared composite material blank into an extrusion mold for preheating, and heat it to 490 °C. Keep it at this temperature for 90 mins, and extrude it into a composite material rod with an extrusion coefficient of 25:1 to obtain a graphene and silicon carbide hybrid reinforced aluminum matrix composite material with a quasi-connected and layered distribution.

[0097] Perform mechanical property tests on the graphene and silicon carbide hybrid reinforced aluminum matrix composite material with a quasi-connected and layered distribution prepared in Example 2. After testing, the tensile strength is 252.87 MPa, the yield strength is 199.86 MPa, and the elongation is 7.91%.

[0098] Example 3

[0099] The preparation method of the graphene and silicon carbide hybrid reinforced aluminum matrix composite material in this embodiment is as follows:

[0100] Step S1: Select pure aluminum powder with a particle size of 5 - 25 μm. The thickness of graphene nanosheets is 5 - 10 nm, the average diameter is 1.6 μm, and the particle size of nano - silicon carbide particles is 20 - 80 nm. Among them, the volume fraction of aluminum powder is 94.7 vol%, the volume fraction of graphene nanosheets is 3.0 vol%, the volume fraction of nano - silicon carbide particles is 0.3 vol%, and stearic acid with a volume fraction of 2.0 wt% is used as the ball - milling process control agent;

[0101] Add nano - silicon carbide particles, aluminum powder, and stearic acid into a 500 - ml planetary ball - milling tank, and fill the ball - milling tank with argon. Among them, the ball - to - powder ratio is 15:1, the ball - milling speed is 200 rpm, and the ball - milling time is 10 h. Then add the prepared graphene nanosheets and carry out variable - speed ball - milling in an argon environment. The ball - to - powder ratio is 15:1. First, ball - mill at a low speed of 100 rpm for 8 h, and then ball - mill at a high speed of 300 rpm for 2 h to obtain a uniform graphene / nano - silicon carbide / aluminum composite powder;

[0102] Step S2: Load the uniformly mixed graphene / nano - silicon carbide / aluminum composite powder into the required mold, first cold - press at 5 MPa for 10 mins, and then carry out spark plasma sintering (SPS) under vacuum to obtain a composite material blank. The SPS parameters are as follows: heat up with the furnace before 450 °C, heat up to the sintering temperature within 90 s after 450 °C, the sintering temperature is 530 °C, apply a pressure of 40 MPa, keep warm and hold pressure for 5 min to obtain a composite material blank; then load the prepared composite material blank into an extrusion mold for pre - heating, heat it to 490 °C, keep it at this temperature for 90 mins, and extrude it into a composite material rod with an extrusion coefficient of 25:1 to obtain a quasi - connected and layered - distributed graphene - and - silicon - carbide hybrid - reinforced aluminum - matrix composite material.

[0103] Figure 14 It shows the distribution of reinforcement phases in the quasi - connected and layered - distributed graphene - and - silicon - carbide hybrid - reinforced aluminum - matrix composite materials prepared in Examples 1, 2, and 3. Conduct mechanical property tests on the quasi - connected and layered - distributed graphene - and - silicon - carbide hybrid - reinforced aluminum - matrix composite material prepared in Example 3. After testing, the tensile strength is 226.43 MPa, the yield strength is 190.95 MPa, and the elongation is 5.53%.

[0104] Figure 14 It is the WDS spectral composition distribution map of the extruded samples prepared in Examples 1, 2, and 3. Among them, (a) represents Example 3; (b) represents Example 2; (c) represents Example 1. It can be seen from Figure 14(b) that the distributions of Si element and C element in the matrix are the most uniform, indicating that the sample prepared in Example 2 with a volume ratio of GNP to SiCnp of 10:3 has the best uniformity and the GNP agglomeration is basically eliminated. Figure 14As shown in (a) and (c), there is a certain degree of aggregation of Si and C elements in the matrix. When the proportion of the reinforcing phase in Example 1 and Example 3 is 10:5 and 10:1, the uniformity of the samples is second only to that of Example 2.

[0105] Comparative Example 3

[0106] The specific steps of the preparation method of the graphene-reinforced aluminum matrix composite material in this comparative example are the same as those in Example 1, except that in step S1, the volume fraction of the aluminum matrix is 97.0 vol%, and the volume fraction of the graphene nanosheets is 3.0 vol%; and single aluminum powder is pre-ball milled without adding nano-silicon carbide particles.

[0107] The mechanical properties of the single graphene-reinforced aluminum matrix composite material (Al-3.0GNP) prepared in Comparative Example 3 were tested, as Figure 15 shown in Table 1. The measured tensile strength was 179.38 MPa, the yield strength was 138.56 MPa, and the elongation was 5.36%.

[0108] Comparative Example 4

[0109] The preparation method of the pure metal (Al-BM) is the same as that of Example 1, except that in step S1, no reinforcing phase graphene nanosheets and silicon carbide nanoparticles are added.

[0110] The mechanical properties of the pure metal material (Al-BM) prepared in Comparative Example 4 were tested, as Figure 15 shown in Table 1. The measured tensile strength was 196.66 MPa, the yield strength was 165.70 MPa, and the elongation was 17.13%.

[0111] Specifically, Figure 15 Fig. is the tensile mechanical property curves of the extruded samples prepared in Example 1, 2, 3 and Comparative Example 3, 4. Table 1 shows the specific data of the elastic modulus E, yield strength YS, tensile strength UTS and elongation after fracture δ of the extruded samples prepared in Example 1, 2, 3 and Comparative Example 3, 4. It can be seen from the figure that compared with the aluminum alloy (Al-BM) in Comparative Example 4 and the single GNP-reinforced composite material (Al-3.0GNP) prepared in Comparative Example 3, the strength and plasticity of the graphene and silicon carbide hybrid-reinforced aluminum matrix composites (Al-3.0GNP-1.5SiC, Al-3.0GNP-0.9SiC, Al-3.0GNP-0.3SiC) in Example 1, Example 2 and Example 3 have been significantly improved, and there is no phenomenon of processing softening, and the uniform plastic deformation ability has been greatly improved.

[0112] Table 1

[0113]

[0114] As described above, these are only the preferred specific embodiments of the present invention. These specific embodiments are different implementation manners based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A preparation method of a graphene and silicon carbide hybrid reinforced aluminum matrix composite, characterized in that, It includes the following steps: Step S1: Under the protection atmosphere of argon, mix nano silicon carbide particles, aluminum powder and a process control agent, ball-mill them, then add graphene nanosheets, and through variable-speed ball-milling, obtain a uniform graphene / nano silicon carbide / aluminum composite powder; The process control agent is stearic acid, and the volume fractions of the nano silicon carbide particles, the graphene nanosheets, the aluminum powder and the stearic acid are 0.3 - 1.5 vol%, 3 - 5 vol%, 90.6 - 95.3 vol% and 1.4 - 2.9 vol% respectively; The rotation speed of the ball-milling is 200 rpm, and the ball-milling time is 7 - 13 h; The variable-speed ball-milling includes: ball-milling for 4 - 10 h under the condition that the ball-milling rotation speed is 100 - 200 rpm, and then ball-milling for 1 - 6 h under the condition that the ball-milling rotation speed is 300 - 400 rpm; The grinding balls used for the ball-milling are stainless steel balls, and the ball-to-material ratio during the ball-milling process is (10 - 15):1; Step S2: After pre-pressing the graphene / nano silicon carbide / aluminum composite powder, through vacuum spark plasma sintering and extrusion forming, obtain a graphene and silicon carbide hybrid reinforced aluminum matrix composite material with a quasi-connected and layered distribution; After pre-pressing the graphene / nano silicon carbide / aluminum composite powder, it includes: loading the graphene / nano silicon carbide / aluminum composite powder into a mold and applying bi-directional pressure; the pressure value of the bi-directional pressure is 5 - 10 MPa, and the pre-pressing time is 10 min; The vacuum discharge plasma sintering includes: under the condition of a vacuum degree of 1×10 -3 Pa - 1×10 -5 Pa, heating the pre-pressed graphene / nano-silicon carbide / aluminum composite powder to the sintering temperature, applying pressure, and after heat preservation and pressure holding, naturally cooling to room temperature; the sintering temperature is 450 - 550 °C, the applied pressure is 30 - 50 MPa, and the heat preservation and pressure holding time is 5 - 10 min; The extrusion forming includes: heating and maintaining for a period of time in an extrusion mold and then extruding into a rod; wherein the heating temperature is 400 - 500 °C, the maintaining time is 90 min, and the extrusion ratio is one of 9:1, 16:1 and 25:1; The particle size of the nano silicon carbide particles is 20 - 80 nm, the particle size of the aluminum powder is 5 - 25 μm, and the thickness of the graphene nanosheets is 5 - 10 nm.

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