A method for preparing a multi-scale reinforcement body coupled reinforced magnesium-based composite material

Abstract

The application discloses a preparation method of a multi-scale reinforcing body coupled reinforced magnesium-based composite material, and belongs to the technical field of composite materials, and comprises the following steps: S1, pretreating micrometer reinforcing bodies and a matrix; S2, building a high-temperature high-viscosity dispersion framework to form a magnesium melt containing graphene nanosheets and magnesium oxide nanoparticles (GNPs & MgOnp); S3, filling the high-temperature high-viscosity dispersion framework to obtain a multi-scale coupled reinforced magnesium-based composite material melt; and S4, performing die casting and thermal deformation treatment. Based on a liquid metallurgy method, the application realizes the regulation of the viscosity of the magnesium melt by in-situ autogenesis of nanometer reinforcing bodies through gas-liquid reaction, avoids the oxidation and combustion of the nanometer particles, creates a high-temperature high-viscosity dispersion environment containing a large number of nanometer reinforcing bodies, solves the problems of poor interface combination and difficult dispersion of micrometer particles, realizes the uniform dispersion of the micrometer reinforcing bodies and the good interface combination between the micrometer reinforcing bodies and the magnesium matrix, and realizes the synergistic reinforcement of the micrometer and nanometer reinforcing bodies on the magnesium matrix.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite material preparation, in particular to a preparation method of magnesium-based composite material coupled with multi-scale reinforcing bodies. BACKGROUND

[0002] In the field of new energy transportation, communication equipment and electronic industry with high demand for weight reduction, magnesium alloy is widely used as a light metal structural material. In order to broaden its application range, high volume fraction (10% to 25 vol.%) of micron reinforcing bodies are added to magnesium alloy to prepare magnesium-based composite material, such as micron silicon carbide SiC and micron titanium carbide TiC, which can effectively improve the strength, stiffness, wear resistance and thermal stability of magnesium alloy, but significantly reduce its plasticity. In order to alleviate the plasticity loss caused by micron particles, carbon nanotubes CNTs, graphene nanosheets GNPs and nano-aluminum oxide Al2O3 are added as nano-reinforcing bodies to avoid stress concentration and achieve material toughening. At present, due to the technical difficulty of dispersing nano-particles, the content of the added nano-particles is limited (≤2 vol.%), which cannot fully exert the advantages of strength and toughness. In order to further exert the reinforcing effect of reinforcing bodies, multi-scale reinforcing bodies are introduced into magnesium matrix to synergistically improve the comprehensive performance of magnesium-based composite material. Different scales (such as adding nano and micron SiC particles) of reinforcing bodies can hinder the movement of dislocations in multiple scales, which can effectively improve the modulus of magnesium alloy and reduce the loss of plasticity.

[0003] However, due to the large size difference between nano-reinforcing bodies (50-200 nm) and micron-reinforcing bodies (5-50 μm), the preparation of magnesium-based composite material not only faces the problem of dispersion of single nano-reinforcing bodies, but also faces the problem of difficult dispersion of micro-nano reinforcing bodies. For example, high temperature is needed for dispersing nano-particles, but high temperature can easily lead to gravity sedimentation of micron particles, and the specific surface energy of nano-reinforcing bodies is large, so the amount of addition is limited. It is difficult to realize multi-type, multi-scale and hybrid reinforced magnesium-based composite material.

[0004] At present, there are many forms of preparation methods of magnesium-based composite material reinforced by micro-nano reinforcing bodies, mainly including stirring casting method, powder metallurgy method, stirring friction method and ultrasonic assisted stirring method.

[0005] In the aspect of micron-reinforcement dispersion, the micron-scale SiC particles can be dispersed into the magnesium matrix by semi-solid stirring casting, effectively improving the stiffness and wear resistance of the material. However, the dispersion of micron-SiC particles is greatly affected by the melt temperature and gravity sedimentation, and a lower semi-solid temperature range makes it difficult to achieve uniform dispersion. The limitation of powder metallurgy is that magnesium powder is easy to oxidize, which ultimately affects the overall performance of the composite material. Magnesium powder is flammable, explosive and easy to oxidize, which poses a great safety hazard. The processing area of friction stir processing is limited to the metal matrix near the stirring head, which is not suitable for processing and dispersion of large-sized metals. At the same time, due to the disorder of the severe plastic deformation process, the stability of the composite material performance is poor, and there is a high size constraint.

[0006] In the aspect of nano-reinforcement dispersion, the uniform dispersion of 0.5% mass fraction of 50 nm particles (SiC, TiC) can be achieved to some extent by using some auxiliary technologies such as high-energy ultrasonic dispersion. However, once the volume fraction of nano-particles increases, agglomeration is easy to form, and the additional nano-reinforcement is easy to oxidize and burn at high temperature, resulting in poor dispersion effect.

[0007] In summary, the current preparation method of multi-scale coupled reinforced magnesium matrix composites has the following shortcomings. First, it is difficult to add both nano-reinforcement and micron-reinforcement at the same time. Nano-reinforcement is easy to adsorb impurities, oxidize and agglomerate, and cannot achieve good interface bonding with the magnesium matrix. Second, there is a mismatch in the optimal dispersion temperature of multi-scale reinforcement. In the traditional semi-solid stirring method, the dispersion of micron-reinforcement is usually limited by the semi-solid temperature range (580-620°C). If the composite temperature is too low, the dispersion effect will be poor due to the shear force brought by mechanical stirring. With the increase of temperature (680-720°C), although it is helpful for the dispersion of nano-reinforcement, it will reduce the viscosity of magnesium melt, resulting in obvious gravity sedimentation of micron-reinforcement. Finally, pure magnesium has no semi-solid state, and most binary magnesium alloy systems (Mg-Mn, Mg-Ca, etc.) or low-alloyed magnesium alloy systems (Mg-Zn-Ca, Mg-Zn-Y, Mg-Zn-Gd, etc.) have a very narrow semi-solid temperature range, which is completely not suitable for semi-solid stirring dispersion.

[0008] Therefore, exploring a multi-scale reinforcement dispersion process suitable for most magnesium alloy systems, avoiding the oxidation and burning of nano-particles, improving the viscosity of magnesium melt while reducing the dispersion temperature difference, and achieving uniform dispersion of micro-nano reinforcement in magnesium at high temperature as much as possible, has become a key factor in improving the preparation process. SUMMARY

[0009] The application aims to provide a preparation method of a multi-scale reinforcing body coupled enhanced magnesium-based composite material, which is based on a liquid metallurgy method, realizes viscosity regulation of a magnesium melt by in-situ autogenic introduction of nano-reinforcing bodies through a gas-liquid reaction, avoids oxidation and combustion of the nano particles, creates a dispersion environment under high-temperature and high-viscosity conditions containing a large number of nano-reinforcing bodies, effectively solves the problems of difficult dispersion of micro-reinforcing bodies and poor interface combination, significantly improves the dispersion temperature of the micro-reinforcing bodies, realizes uniform dispersion of the micro-reinforcing bodies and good interface combination with the magnesium matrix, and realizes synergistic enhancement of the micro-nano reinforcing bodies on the magnesium matrix.

[0010] To achieve the above-mentioned purpose, the application provides a preparation method of a multi-scale reinforcing body coupled enhanced magnesium-based composite material, which comprises the following steps:

[0011] S1, pretreating the micro-reinforcing bodies and the matrix;

[0012] S2, building a high-temperature and high-viscosity dispersion framework: melting the matrix under the condition of 720 DEG C, then introducing a carbon source gas into the melted matrix to perform a gas-liquid reaction, controlling the gas flow rate to be 0.5-1.5 L / min and the gas flow time to be 20 min-2 h, in-situ autogenically generating nano-reinforcing bodies with good interface combination with the magnesium matrix, and forming a magnesium melt containing graphene nano sheets and magnesium oxide nano particles (GNPs & MgOnp);

[0013] S3, filling the micro particles into the high-temperature and high-viscosity dispersion framework: adding the micro-reinforcing bodies into the magnesium melt containing graphene nano sheets and magnesium oxide nano particles (GNPs & MgOnp) in a stirring process under the condition of 680-780 DEG C, to obtain a multi-scale coupled enhanced magnesium-based composite material melt;

[0014] S4, performing die casting and hot deformation treatment on the composite material melt treated in S3.

[0015] Preferably, in the pretreatment process of S1, the matrix is soaked and cleaned by using a 5%-8% sulfuric acid or hydrochloric acid solution, and the micro-reinforcing bodies are subjected to drying treatment, and the drying temperature is 250 DEG C.

[0016] Preferably, in S1, the matrix is pure magnesium or a magnesium alloy; the micro-reinforcing bodies are silicon carbide particles, titanium carbide particles or pure metal titanium particles, and the size is 5-25 mu m, preferably 10 mu m.

[0017] Preferably, in S1, the magnesium alloy is a magnesium alloy system that does not react with carbon elements, and the magnesium alloy is preferably Mg-6Zn.

[0018] Preferably, in the S2, the substrate is first melted at high temperature under a protective atmosphere, the protective atmosphere is CO2 and SF6 with a ratio of 40:1, then a carbon source gas is introduced for gas-liquid reaction, the carbon source gas is CO2 with a purity of 99% or CO.

[0019] Preferably, in the S2, a gas flow meter is used to control the gas flow rate and the gas flow time, so as to accurately control the content of the graphene nanosheet and the magnesium oxide nanoparticle (GNPs & MgOnp), the reaction process is continuously stirred, the stirring rate is 1000-1800 r / min, and the magnesium melt containing the graphene nanosheet and the magnesium oxide nanoparticle (GNPs & MgOnp) is formed at high temperature.

[0020] Preferably, in the S2, the substrate is melted at 720℃, the gas flow rate is controlled to be 0.85 L / min, and the gas flow time is controlled to be 50 min, so as to generate 0.32 vol.% of the graphene nanosheet and 1.3 vol.% of the magnesium oxide nanoparticle.

[0021] Preferably, in the S3, the temperature for adding the micron-reinforcing body is 720℃, the stirring rate is 1000 r / min, and the stirring time is 20 min.

[0022] Preferably, in the S3, the volume fraction of the micron-reinforcing body is 5-25%, preferably 10%, the micron-reinforcing body is preheated before being added, the preheating temperature is 400-500℃, and the preheating time is 30 min.

[0023] Preferably, in the S4, the obtained multi-scale coupling reinforced magnesium-based composite melt is pressure-cast in a steel mold preheated at 450℃, and a composite ingot is obtained after cooling; then, the composite ingot is subjected to low-speed hot extrusion at a temperature of 300-400℃, and a final product is obtained.

[0024] Preferably, the pressure of the pressure casting is 150 Mpa, and the time is 5 min.

[0025] The speed of the hot extrusion is 0.1-1 mm / s, and the extrusion ratio is 16:1.

[0026] Therefore, the method for preparing the multi-scale coupling reinforced magnesium-based composite material has the following beneficial effects:

[0027] (1) The purpose of the present application is to realize the dispersion of multiscale reinforcements in magnesium. In order to preferentially solve the dispersion and interface bonding problems of nanoparticles, the nanoreinforcements with good interface bonding with the magnesium matrix are in-situ generated by a gas-liquid reaction in the magnesium melt, which is simple in process and has good thermal stability. Not only is the phenomenon of oxidation and combustion of nanoreinforcements avoided, but also the rheological properties of the magnesium melt are improved, and a dispersion framework composed of nanoreinforcements and magnesium melt is built, which lays a good foundation for the dispersion of micrometer reinforcements.

[0028] The presence of nanoparticles increases the internal friction of the melt. The increase in internal friction leads to a decrease in the flowability of the melt, thereby increasing the viscosity. In the process of high-speed rheology, nanoparticles can inhibit the shear thinning behavior of the melt, and the viscosity will not decrease significantly even at high shear rate. Therefore, the framework still has high melt viscosity under high-temperature high-speed stirring, which creates a dispersion temperature significantly higher than that of traditional semi-solid stirring for the dispersion of micrometer reinforcements. The high-viscosity magnesium melt not only forms a thick liquid layer around the particles, which helps to provide mechanical resistance and prevent direct contact and agglomeration between particles, but also increases the cohesion of the liquid, thereby helping to prevent the sedimentation and agglomeration of micrometer particles, facilitating the filling of the dispersion framework by micrometer reinforcements at high temperature, effectively improving the uneven distribution of traditional micrometer reinforcements in the matrix, and realizing the preparation of high-quality multiscale reinforcement coupled magnesium matrix composite materials.

[0029] (2) The present application raises the dispersion temperature of micrometer reinforcements to 720℃, which is about 100℃ higher than the traditional semi-solid temperature and is not limited by the semi-solid temperature range. It can be stably maintained and is suitable for more magnesium alloy systems, shortening the addition time of micrometer reinforcements and effectively improving the quality and efficiency of the preparation of magnesium matrix composite materials.

[0030] (3) The construction of a high-temperature high-viscosity dispersion framework can significantly increase the viscosity of the melt through nanoparticles in the melt, effectively increase the shear force on micrometer reinforcements, thereby weakening the agglomeration of micrometer reinforcements and obtaining good dispersion effect. The dispersion under high-temperature conditions can also significantly improve the interface bonding between micrometer reinforcements and the magnesium matrix. The present application uses a short process and low-cost liquid metallurgy method to realize the efficient addition of micrometer and nanometer reinforcements and the synergistic reinforcement of the magnesium matrix.

[0031] The technical solutions of the present application will be further described in detail below through the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The preparation flowchart of the present application is shown in the figure.

[0033] Figure 2SEM comparison chart of the present application example 1 and comparative example 1, wherein (a) is the SEM picture of example 1, (b) is the SEM picture of comparative example 1;

[0034] Figure 3 SEM picture of the present application comparative example 2;

[0035] Figure 4 SEM picture of the present application comparative example 3;

[0036] Figure 5 Performance comparison chart of the present application example 1 and comparative example 1;

[0037] Figure 6 TEM picture of the present application example 2 GNPs & MgO np ; wherein (a) is the TEM picture of graphene nanosheet extracted from magnesium melt, (b) is the macroscopic picture of graphene nanosheet extracted from magnesium melt, (c) is the diffraction ring of magnesium oxide nanoparticles in magnesium melt, (d) is the TEM picture of magnesium oxide nanoparticles in magnesium melt;

[0038] Figure 7 SEM picture of the present application example 2. DETAILED DESCRIPTION

[0039] The technical solutions of the present application are further described below by means of the accompanying drawings and examples.

[0040] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely below by combining the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application.

[0041] The present application provides a preparation method of a multi-scale reinforcement coupled reinforced magnesium-based composite material, and the preparation process is shown as follows: Figure 1 and specifically includes the following steps:

[0042] 1) Selecting a pure magnesium matrix or a magnesium alloy matrix, the magnesium alloy being a magnesium alloy system which does not react with carbon elements, and the magnesium alloy being preferably Mg-6Zn; for the selected matrix, first, pre-treatment is performed, and the matrix is cleaned by immersion in a 5% to 8% sulfuric acid or hydrochloric acid solution; selecting 5 μm to 25 μm silicon carbide particles, titanium carbide particles or pure metal titanium particles as micron reinforcements, and the size being preferably 10 μm; and the selected micron reinforcements are dried at 250°C;

[0043] S2, melting the pure magnesium matrix or magnesium alloy matrix under the condition of 720℃, in a protective atmosphere of CO2 and SF6 with a ratio of 40:1, obtaining the molten matrix, then cooling to 680℃, and then introducing 99% pure CO2 or CO into the molten pure magnesium matrix or magnesium alloy matrix to carry out gas-liquid reaction, controlling the gas flow rate to be 0.5-1.5 L / min, and the gas flow time to be 20 min-2 h, in-situ self-generating nanometer reinforcing bodies which are well combined with the magnesium matrix, not only avoiding the phenomenon of oxidation and combustion of the nanometer reinforcing bodies, but also improving the rheological properties of the magnesium melt, continuously stirring under the condition that the stirring rate is 1000-1800 r / min, obtaining the magnesium melt containing GNPs&MgOnp, and forming a dispersion framework composed of the nanometer reinforcing bodies and the magnesium melt, which lays a good foundation for the dispersion of the micron reinforcing bodies;

[0044] S3, increasing the temperature to 720℃, and adding 10% volume fraction of silicon carbide particles, titanium carbide particles or pure titanium metal particles into the magnesium melt containing GNPs&MgO in the stirring process, the presence of the nanometer particles increases the internal friction of the melt, and the increase of the internal friction leads to the decrease of the flowability of the melt, thereby increasing the viscosity, and the nanometer particles can inhibit the shear thinning behavior of the melt, and the viscosity will not be significantly reduced under high shear rate; after stirring for a period of time, a multiscale coupling reinforced magnesium matrix composite melt is obtained;

[0045] S4, pressing the obtained multiscale coupling reinforced magnesium matrix composite melt in a steel mold preheated to 450℃, under a pressure of 150 Mpa for 5 min, and obtaining a composite ingot after cooling; then, the composite ingot is subjected to low-speed hot extrusion at a temperature of 300-400℃, the speed of the hot extrusion is 0.1-1 mm / s, and the extrusion ratio is 16:1, and finally, a product with uniform structure and better compactness is obtained.

[0046] In the present application, the dispersion temperature of the micron reinforcing bodies is about 100℃ higher than the traditional semi-solid temperature, the micron reinforcing bodies are dispersed at high temperature, which is suitable for more magnesium alloy systems, especially pure magnesium or low-alloyed magnesium alloys without semi-solid state or with extremely narrow semi-solid temperature range, the adding time of the micron reinforcing bodies is shortened, and the quality and efficiency of the preparation of the magnesium matrix composite are effectively improved.

[0047] The present application will be further described below through examples and comparative examples.

[0048] Example 1

[0049] Preparation of GNPs&MgO-SiCp / Mg-6Zn includes the following steps:

[0050] 1) According to the mass of the Mg-6Zn matrix, 10 μm, 10 vol.% of silicon carbide particles are configured;

[0051] 2) The impurities on the surface of Mg-6Zn were cleaned by soaking in a 8% sulfuric acid solution, and the micron-sized reinforcements were dried at 250°C to remove the water adsorbed on their surfaces;

[0052] 3) The Mg-6Zn was melted at 720°C in a protective atmosphere (40:1 ratio of CO2 and SF6), and after maintaining for 20 minutes, 6% Mg-6Zn by mass was added;

[0053] 4) The temperature was lowered to 680°C, and by the gas-liquid reaction of the carbon source gas and the Mg-6Zn melt, the gas flow rate was controlled to be 0.85 L / min and the gas flow time was controlled to be 50 min, to generate 0.32 vol.% graphene nanosheets and 1.3 vol.% nano-magnesium oxide particles in the magnesium, the reaction process was continuously stirred at a stirring rate of 1000 r / min, to form a Mg-6Zn melt containing GNPs & MgOnp at high temperature.

[0054] 5) The temperature was raised to 720°C, and then 10 vol.% silicon carbide particles were added into the Mg-6Zn melt containing GNPs & MgO in the stirring process, and after the addition was completed, the stirring was continued for 20 minutes.

[0055] 6) After the micron-sized reinforcements were added, the size-coupled magnesium matrix composite melt was die-cast in a preheated steel mold at 450°C, the pressure was 150 MPa, and the duration was 5 min; after cooling, a composite ingot was obtained.

[0056] 7) The prepared composite ingot was subjected to low-speed hot extrusion at a temperature of 300°C, the extrusion speed was 0.5 mm / s, and the extrusion ratio was 16:1, to obtain a composite material with uniform structure and better density.

[0057] The SEM picture of the composite material prepared in this example is shown as (a) in FIG. 1. Figure 2 The micron-sized reinforcements are uniformly distributed.

[0058] Comparative Example 1

[0059] The SiCp / Mg-6Zn was prepared, including the following steps:

[0060] 1) 10 μm, 10 vol.% silicon carbide particles were configured according to the mass of the Mg-6Zn matrix;

[0061] 2) The impurities on the surface of Mg-6Zn were cleaned by soaking in a 8% sulfuric acid solution, and the micron-sized reinforcements were dried at 250°C to remove the water adsorbed on their surfaces;

[0062] 3) Melting Mg-6Zn at 720℃ under protective atmosphere (40:1 ratio of CO2 and SF6) for 20 minutes, then adding 6% of Mg-6Zn by mass;

[0063] 4) Keeping the temperature at 720℃, adding 10 vol.% of SiC particles into the Mg-6Zn melt in the process of stirring, and continuing to stir for 20 minutes after the addition.

[0064] 5) After adding the micron-reinforcement, carrying out die casting in a preheated steel mold at 450℃, with a pressure of 150 MPa for 5 minutes; and obtaining the composite ingot after cooling.

[0065] 6) Carrying out low-speed hot extrusion on the prepared composite ingot at a temperature of 300℃, with an extrusion speed of 0.5 mm / s and an extrusion ratio of 16:1, to obtain the composite.

[0066] The SEM image of the composite prepared in the present comparative example is shown in (b) of FIG. 1, from which it can be seen that the micron-reinforcement is unevenly distributed. Compared with Example 1, the present comparative example does not carry out gas-liquid reaction, and does not in-situ generate the nanometer-reinforcement which is well combined with the magnesium matrix. In comparison, the method in Example 1 is more conducive to the dispersion of the micron-reinforcement. Figure 2

[0067] The performance comparison of the composites prepared in Example 1 and Comparative Example 1 shows that the composite prepared in Example 1 has better performance. Figure 5

[0068] Comparative Example 2

[0069] Preparation of SiCp / Mg-6Zn, including the following steps:

[0070] 1) Configuring 10 μm, 10 vol.% of SiC particles according to the mass of the Mg-6Zn matrix;

[0071] 2) Soaking and cleaning the impurities on the surface of Mg-6Zn with 8% sulfuric acid solution, and drying the micron-reinforcement at 250℃ to remove the water adsorbed on the surface thereof;

[0072] 3) Melting Mg-6Zn at 720℃ under protective atmosphere (40:1 ratio of CO2 and SF6) for 20 minutes, then adding 6% of Mg-6Zn by mass;

[0073] 4) Adding 10 vol.% of SiC particles into the Mg-6Zn melt in the process of stirring at 585℃, and continuing to stir for 20 minutes after the addition.

[0074] ​​5) After adding the micron-reinforced material, it was die-cast in a preheated steel mold at 450°C at a pressure of 150 MPa for 5 minutes; after cooling, a composite material ingot was obtained.

[0075] 6) The prepared composite material ingot was subjected to low-speed hot extrusion at a temperature of 300℃, with an extrusion speed of 0.5 mm / s and an extrusion ratio of 16:1 to obtain the composite material.

[0076] The SEM image of the composite material prepared in this comparative example is shown below. Figure 3 As shown, the distribution of the micron-reinforced material can be seen. Compared with Example 1, this comparative example shows that the micron-particles added at low temperature are unevenly dispersed and prone to agglomeration. The dispersion temperature in Example 1 is about 100°C higher than the traditional semi-solid temperature, which realizes the dispersion of micron-reinforced material at high temperature and is suitable for more magnesium alloy systems.

[0077] Comparative Example 3

[0078] The preparation of GNPs & MgO-SiCp / Mg-6Zn includes the following steps:

[0079] 1) Prepare silicon carbide particles of 10 μm and 10 vol.% according to the mass of the Mg-6Zn matrix;

[0080] 2) The impurities on the surface of Mg-6Zn were soaked and cleaned with an 8% sulfuric acid solution, and the micron-reinforced body was dried at 250°C to remove the adsorbed moisture on its surface.

[0081] 3) Melt Mg-6Zn at 720℃ in a protective atmosphere (40:1 ratio of CO2 and SF6), hold for 20 minutes, then add 6% Mg-6Zn by mass; then add 0.32 vol.% graphene nanosheets and 1.3 vol.% nano magnesium oxide particles, stirring continuously during the addition process to form a magnesium melt containing GNPs & MgOnp.

[0082] 4) Heat to 720℃, then add 10 vol.% silicon carbide particles into the magnesium melt containing GNPs & MgO while stirring. Continue stirring for 20 minutes after the addition is complete.

[0083] 5) After adding the micron-reinforced material, it was die-cast in a preheated steel mold at 450°C at a pressure of 150 MPa for 5 minutes; after cooling, a composite material ingot was obtained.

[0084] 6) The prepared composite material ingot was subjected to low-speed hot extrusion at a temperature of 300℃, with an extrusion speed of 0.5 mm / s and an extrusion ratio of 16:1 to obtain the composite material.

[0085] The composite prepared in Comparative Example 3 is directly added with graphene nanosheets and nano magnesium oxide particles, and no nano-reinforcement well combined with the magnesium matrix interface is in-situ generated during its preparation process, so in this process, the nano-particles are easily oxidized and burned with the magnesium melt, and the higher the temperature, the easier the nano-particles are oxidized with the magnesium melt. At the same time, it can also be seen from Figure 4 that the micro-reinforcement is unevenly distributed.

[0086] Example 2

[0087] Preparation of SiCp-GNPs&MgO / Mg, including the following steps:

[0088] 1) According to the mass of the pure magnesium matrix, 10 μm, 10 vol.% of silicon carbide particles are configured;

[0089] 2) The impurities on the surface of the pure magnesium are soaked and cleaned with 8% sulfuric acid solution, and the micron-reinforcement is dried at 250°C to remove the water adsorbed on its surface;

[0090] 3) The pure magnesium is melted at 720°C in a protective atmosphere (40:1 ratio of CO2 and SF6), and after maintaining for 20 minutes, 6% pure Zn by mass is added;

[0091] 4) The temperature is lowered to 680°C, and by the gas-liquid reaction of the carbon source gas and the pure magnesium melt, the air speed is controlled at 0.85 L / min and the air time is controlled at 50 min, 0.32 vol.% of graphene nanosheets and 1.3 vol.% of nano magnesium oxide particles are generated in the magnesium, the reaction process is continuously stirred, and the stirring rate is 1000 r / min, forming a magnesium melt containing GNPs&MgOnp at high temperature.

[0092] 5) The temperature is raised to 720°C, and then 10 vol.% of silicon carbide particles are added into the magnesium melt containing GNPs&MgO in the stirring process, and after the addition is completed, the stirring is continued for 20 minutes.

[0093] 6) After adding the micro-reinforcement, the size-coupled reinforced magnesium matrix composite melt is pressure cast in a preheated 450°C steel mold, the pressure is 150 MPa, and the pressure casting lasts for 5 min; after cooling, the composite ingot is obtained.

[0094] 7) The prepared composite ingot is subjected to low-speed hot extrusion at a temperature of 300°C, the extrusion speed is 0.5 mm / s, and the extrusion ratio is 16:1, and a composite material with uniform structure and better density is obtained.

[0095] The TEM picture of GNPs&MgO np in this example is shown in Figure 6 , and the SEM picture is shown in Figure 7As shown, it can be seen that the micron reinforcing bodies are uniformly distributed.

[0096] By comparing the above examples and comparative examples, by using the method protected by the present application, the multiscale reinforced composite material is obtained by in-situ autogenesis of gas-liquid, the content of GNPs & MgO np is controlled within a suitable range, thereby increasing the internal friction of the melt, the increase of internal friction will lead to the decrease of melt fluidity, thereby increasing the viscosity; and due to the presence of GNPs & MgO np , the shear thinning behavior of the melt can be inhibited, that is, the viscosity will not decrease significantly even at high shear rate, which creates a higher dispersion temperature for the dispersion of micron reinforcing bodies, and the magnesium melt with higher viscosity not only can form a thicker liquid layer around the particles, which helps to provide mechanical resistance to prevent direct contact and agglomeration between particles; but also can increase the cohesion of the liquid, thereby helping to prevent the sedimentation and agglomeration of micron particles, so that the micron reinforcing bodies are uniformly distributed in the matrix.

[0097] Therefore, the present application is a preparation method of a multiscale reinforcing body coupled magnesium matrix composite material, which is based on liquid metallurgy, introduces nano reinforcing bodies by in-situ autogenesis of gas-liquid to realize the viscosity control of magnesium melt, avoids the oxidation and combustion of nano particles, creates a dispersion environment under high temperature and high viscosity conditions containing a large number of nano reinforcing bodies, effectively solves the problems of difficult dispersion of micron reinforcing bodies and poor interface bonding, significantly improves the dispersion temperature of micron reinforcing bodies, realizes the uniform dispersion of micron reinforcing bodies and the good interface bonding with magnesium matrix, and simultaneously realizes the synergistic reinforcement of micron and nano reinforcing bodies to magnesium matrix.

[0098] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application but not to limit it, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: it can still modify or equivalently replace the technical solutions of the present application, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A method of making a multiscale reinforcement body coupled reinforced magnesium-based composite material, characterized in that, The method comprises the following steps: S1, pretreating the micron reinforcing agent and the matrix; the matrix is pure magnesium or a magnesium alloy; the micron reinforcing agent is silicon carbide particles, titanium carbide particles or pure titanium particles; the magnesium alloy is a magnesium alloy system that does not react with carbon elements; S2, building a high-temperature and high-viscosity dispersion framework: melting the pure magnesium matrix or the magnesium alloy matrix under the protection of a CO2 and SF6 atmosphere with a ratio of 40:1 at 720 DEG C, obtaining a molten matrix, then cooling to 680 DEG C, and performing a gas-liquid reaction on the molten pure magnesium matrix or the magnesium alloy matrix with 99% pure CO2 or CO, controlling the aeration speed to be 0.5-1.5 L / min and the aeration time to be 20 min-2 h, in-situ autogenously generating nanometer reinforcing agents that are well combined with the magnesium matrix interface, continuously stirring at a stirring rate of 1000-1800 r / min, obtaining a magnesium melt containing graphene nanosheets and magnesium oxide nanoparticles, and forming a dispersion framework composed of the nanometer reinforcing agents and the magnesium melt; S3, filling the high-temperature and high-viscosity dispersion framework with micron particles: the temperature for adding the micron reinforcing agent is 720 DEG C, the micron reinforcing agent is added to the magnesium melt containing graphene nanosheets and magnesium oxide nanoparticles in the stirring process, and a multi-scale coupling reinforced magnesium matrix composite melt is obtained; the stirring rate is 1000 r / min, and the stirring time is 20 min; S4, performing die casting and thermal deformation treatment on the composite melt treated in S3; specifically, the obtained multi-scale coupling reinforced magnesium matrix composite melt is subjected to die casting in a preheated 450 DEG C steel mold, and a composite ingot is obtained after cooling; then the composite ingot is subjected to low-speed thermal extrusion at a temperature of 300-400 DEG C, and a final product is obtained.

2. A method of producing a multiscale reinforcement body-coupled reinforced magnesium-based composite material according to claim 1, characterized by: In S1, the size of the micron reinforcing agent is 5-25 μm.

3. A method of producing a multiscale reinforcement body-coupled reinforced magnesium-based composite material according to claim 2, characterized by: In S1, the magnesium alloy is Mg-6Zn.

4. The method of claim 1, wherein the method further comprises: In S2, a gas flow meter is used to control the aeration speed and the aeration time, the content of the graphene nanosheets and the magnesium oxide nanoparticles is accurately controlled, the reaction process is continuously stirred, the stirring rate is 1000-1800 r / min, and a magnesium melt containing graphene nanosheets and magnesium oxide nanoparticles at high temperature is formed.

5. A method of producing a multiscale reinforcement body-coupled reinforced magnesium-based composite material according to claim 4, characterized by: In S2, the matrix is melted at 720 DEG C, the aeration speed is controlled to be 0.85 L / min, the aeration time is controlled to be 50 min, 0.32 vol.% of graphene nanosheets and 1.3 vol.% of nanometer magnesium oxide particles are generated.

6. The method of claim 1, wherein the method further comprises: In S3, the volume fraction of the micron reinforcing agent is 5-25%, the micron reinforcing agent is preheated before being added, the preheating temperature is 400-500 DEG C, and the preheating time is 30 min.

7. The method of claim 1, wherein the method further comprises: The pressure of the die casting is 150 MPa, and the time is 5 min; The speed of the thermal extrusion is 0.1-1 mm / s, and the extrusion ratio is 16:1.

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