Bi-level micro / nano ceramic particle reinforced magnesium matrix composites, their preparation methods and applications

Abstract

This invention provides a bi-level micro / nano ceramic particle reinforced magnesium-based composite material, its preparation method, and its applications. The bi-level micro / nano ceramic particle reinforced magnesium-based composite material comprises Mg-xZn-yAl-zCa and silicon carbide particles, wherein 2≤x≤8, 1≤y≤5, 0.3≤z≤1, and x, y, and z are mass percentages; the silicon carbide particles include micron-sized silicon carbide and nano-sized silicon carbide. This invention employs a chemical dispersion method to effectively break up the agglomeration of nanoparticles, allowing the nanoparticles to adhere to the micron-sized particles, and also effectively prevents the inhalation of nanoparticle dust into the lungs, reducing the risk of pneumoconiosis. Furthermore, the use of a staged stirring method effectively reduces the oxidation of the melt, resulting in a composite material with fewer internal defects, a denser structure, and superior mechanical properties compared to the direct stirring method. Moreover, this invention has the advantages of simple equipment and easy operation, greatly improving the preparation efficiency of magnesium-based composite materials.

Description

Technical Field

[0001] This invention relates to magnesium-based composite material technology, and more particularly to a bi-level micro / nano ceramic particle reinforced magnesium-based composite material, its preparation method, and its applications. Background Technology

[0002] Currently, most engine blocks on the market are manufactured using aluminum alloys combined with pressure casting, achieving engine efficiency of approximately 35%. Further reducing vehicle weight is a crucial method for increasing fuel efficiency. Magnesium and its alloys, due to their lightweight, high specific strength and stiffness, and good vibration damping properties, hold promise as a next-generation lightweight structural material to replace aluminum alloys in engine block manufacturing. However, compared to aluminum alloys, magnesium and its alloys suffer from lower absolute strength, poorer wear resistance, and lower high-temperature performance. Adding ceramic particles to magnesium alloys can produce novel magnesium-based composite materials that possess both room-temperature and high-temperature strength. Among these, silicon carbide particles (SiC) are particularly valuable. p α-SiC is widely available, inexpensive, and... p Having the same close-packed hexagonal structure as magnesium alloys, it is beneficial for the wetting between particles and the matrix and for particle distribution. While the addition of micron-sized SiCp (m-SiCp) can significantly improve the strength of the material, it often comes with a substantial loss of toughness. Introducing nanoparticles can effectively alleviate this contradiction. The addition of nano-SiCp (n-SiCp) can not only significantly refine the grain size but also significantly improve the alloy strength through the Orowan strengthening effect. However, nanoparticles have high surface energy and are prone to agglomeration during preparation, which is detrimental to the improvement of material properties. Furthermore, magnesium melt is highly susceptible to oxidation and combustion during preparation, further reducing material properties.

[0003] Therefore, how to make SiC p Uniform dispersion within the matrix and reduced oxidation of the alloy melt are of great significance for the preparation of high-performance magnesium-based composite materials. Summary of the Invention

[0004] The purpose of this invention is to address the problems of nanoparticles easily agglomerating in traditional magnesium-based composite materials, which is detrimental to the improvement of material performance; and the fact that traditional magnesium melts are prone to oxidation and combustion during the preparation process, which further reduces the material performance. The invention proposes a bi-level micro / nano ceramic particle-reinforced magnesium-based composite material, in which nanoparticles are attached to micron-sized particles. The presence of micron-sized particles results in better dispersion of nanoparticles, leading to a denser structure and superior mechanical properties in the magnesium-based composite material.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a dual-level micro / nano ceramic particle reinforced magnesium-based composite material includes Mg-xZn-yAl-zCa and silicon carbide particles, wherein 2≤x≤8, 1≤y≤5, 0.3≤z≤1, and x, y, and z are mass percentages; wherein the silicon carbide particles include micron-sized silicon carbide and nano-sized silicon carbide, the content of micron-sized silicon carbide is 5% to 10%, and the content of nano-sized silicon carbide is 0.3% to 1%. Unless otherwise specified, % in the present invention refers to mass percentages.

[0006] Furthermore, the preferred content range is 4≤x≤6, 1≤y≤3, and 0.3≤z≤0.6.

[0007] Furthermore, the preferred content of the micron-sized silicon carbide is 8% to 10%, and the preferred content of the nano-sized silicon carbide is 0.5% to 1%.

[0008] Further, the size of the micron-sized silicon carbide is 5–15 μm, and the size of the nano-sized silicon carbide is 40–80 nm. Preferably, the size of the micron-sized silicon carbide is 8–10 μm, and the size of the nano-sized silicon carbide is 40–60 nm.

[0009] Furthermore, the strength of the bi-level micro / nano ceramic particle reinforced magnesium matrix composite material is 180–210 MPa, and the elongation is 3%–5%.

[0010] Another objective of this invention discloses a method for preparing a bi-level micro / nano ceramic particle reinforced magnesium-based composite material, comprising the following steps:

[0011] Step 1: Prepare the dispersant solution;

[0012] Step 2: Pour the silicon carbide particles into the dispersant solution and disperse them by mechanical stirring so that the nanoparticles adhere to the surface of the micron particles.

[0013] Step 3: Heat and dry the mixed silicon carbide solution until the liquid is completely evaporated to obtain dried mixed silicon carbide particles;

[0014] Step 4: Melt the magnesium alloy at 700-750℃, then cool the melt to a semi-solid state. Insert the preheated stirring paddle into the melt, start the stirring paddle, and after a stable vortex is formed, add the preheated mixed silicon carbide particles.

[0015] Step 5: Stir using a staged stirring method;

[0016] Step 6: Heat to 700-720℃, use non-vortex stirring, heat the melt to 710-725℃, pour it into a mold preheated to 400-500℃, and solidify it under a pressure of 150-200MPa to obtain a bi-level micro-nano ceramic particle reinforced magnesium-based composite material.

[0017] Furthermore, the dispersant solution in step one is a mixed solution of ethanol and polyethylene glycol 400.

[0018] Furthermore, in step one, the concentration of polyethylene glycol 400 in the dispersant solution is 2-5 wt%, preferably 2-4 wt%.

[0019] Furthermore, in step two, the mass ratio of silicon carbide particles to dispersant solution is 1:3 to 5; the total mass fraction of silicon carbide particles in the composite material is 5.3% to 11%.

[0020] Furthermore, in step two, the silicon carbide particles include micron-sized silicon carbide particles and nano-sized silicon carbide particles, and the mass ratio of the micron-sized silicon carbide particles to the nano-sized silicon carbide particles is 4 to 14:1, preferably 5 to 10:1.

[0021] Furthermore, in step two, the mechanical stirring rate is 200–400 r / min, and the stirring time is 0.5–2 h. Preferably, the mechanical stirring rate is 300–3802 r / min, and the stirring time is 1–1.5 h.

[0022] Furthermore, the drying temperature in step three is 40–70°C, preferably 50–65°C.

[0023] Furthermore, in step four, the magnesium alloy is Mg-xZn-yAl-zCa, where 2≤x≤8, 1≤y≤5, 0.3≤z≤1, and x, y, and z are mass fractions.

[0024] Furthermore, in step four, the melt is cooled to a semi-solid temperature range of 600–630°C at a cooling rate of 2–4°C / min.

[0025] Furthermore, in step four, the position of the stirring paddle is such that the distance between the stirring paddle and the bottom of the crucible is one-quarter to one-half of the melt height.

[0026] Furthermore, in step four, the temperature of the preheated mixed silicon carbide particles is 400–500°C, and the preheating time is not less than 2 hours.

[0027] Furthermore, in step four, the mixed silicon carbide particles are added by mechanical vibration, and all the particles are added within 5 to 15 minutes, with the preferred time being 8 to 12 minutes.

[0028] Furthermore, the specific operation of the graded stirring method in step five is as follows: First, stir at a high speed of 1000-1200 r / min for 1-3 min to generate a large eddy current that entrains the particles into the melt and completes the initial dispersion of the particles. Then, reduce the speed to 800-950 r / min and stir for 2-5 min to complete the macroscopic dispersion of the particles. Finally, reduce the speed to 600-750 r / min and stir for 3-5 min to further disperse the particles.

[0029] Furthermore, in step six, the stirring speed without vortex is 100–300 r / min, and the stirring time is 5–15 min, preferably 150–270 r / min, and the stirring time is 6–10 min. Vortex stirring has a high speed and forms large vortices, making it easier to add particles. Furthermore, the melt shear force generated by vortex stirring is high, making it easier to disperse particles. However, this is only a preliminary dispersion; some macroscopic agglomeration still exists. Also, by step six, the melt is already in a liquid state, and using vortex stirring in the liquid state would cause severe gas entrapment. Therefore, vortex-free stirring is used. Vortex-free stirring is used to further disperse macroscopic particle agglomeration without damaging the melt surface.

[0030] Another objective of this invention is to disclose the use of a bi-level micro / nano ceramic particle reinforced magnesium matrix composite material in the automotive field.

[0031] Furthermore, the dual-stage micro / nano ceramic particle reinforced magnesium matrix composite material has applications in automotive steering wheels and seats.

[0032] This invention first disperses mixed silicon carbide particles using a low-boiling-point chemical solution, then evaporates to remove the chemical solution; followed by semi-solid staged stirring; liquid-state vortex-free stirring; and finally, solidification under pressure. This invention aims to solve the dispersion problem of SiCp (p represents particles) during composite material preparation using a simple method. This invention also solves the problems of nanoparticle agglomeration and reducing alloy melt oxidation. Specifically, this invention has the following advantages compared to existing technologies:

[0033] 1) This invention uses a chemical dispersion method to fully disperse nanoparticles and attach them to micron-sized particles to obtain uniformly mixed dual-size particles. The semi-solid stirring technology can prepare magnesium-based composite materials with uniformly dispersed particles, and reduces the risk of inhaling nanoparticles into the lungs during particle mixing.

[0034] 2) The application of the graded stirring method in this invention, compared with the traditional semi-solid stirring method, can effectively disperse micro and macro agglomerates of particles and successfully reduce the oxidation of the melt. Ordinary stirring casting processes use a fixed stirring rate, stirring for a certain time in a semi-solid state before directly pouring the mixture at a higher temperature. Gas entrapment in the casting of magnesium-based composite materials mainly occurs during semi-solid stirring. Therefore, this invention explores graded stirring. First, a high stirring speed is used to disperse the main agglomerates of particles, then the stirring rate is reduced. This reduces eddies, thereby reducing the possibility of gas absorption in the melt. Furthermore, after large particle agglomerates are dispersed, small particle agglomerates can also be well dispersed at a lower stirring rate. This not only reduces melt oxidation but also ensures good particle dispersion. The magnesium-based composite material prepared by the graded stirring method of this invention has fewer internal defects, a denser structure, and superior mechanical properties compared to the direct stirring method. Its strength can reach 180–210 MPa, significantly higher than the 130–150 MPa of the magnesium matrix. Figure 4 As shown.

[0035] 3) The present invention also has the advantages of simple equipment and easy operation, which greatly improves the preparation efficiency of magnesium-based composite materials. Attached Figure Description

[0036] Figure 1 A schematic diagram of the die-casting structure used in this invention:

[0037] Figure 2 Microstructure diagram of the bi-dimensional silicon carbide particle-reinforced magnesium matrix composite material prepared under the conditions of the example;

[0038] Figure 3 The microstructure of the magnesium matrix composite material reinforced with bi-dimensional silicon carbide particles prepared under comparative conditions is shown in the figure.

[0039] Figure 4 This is a comparison chart of the mechanical properties of the composite materials prepared under the conditions of the examples;

[0040] Figure 5 This is a comparison chart of the mechanical properties of composite materials prepared under comparative conditions. Detailed Implementation

[0041] The present invention will be further described below with reference to the embodiments:

[0042] A schematic diagram of the die-casting structure used in the bi-level micro / nano ceramic particle reinforced magnesium matrix composite material of this invention is shown below. Figure 1As shown in the diagram. 1 represents the pressure sensor, 2 represents the guide pillar, 3 represents the insulation system, 4 represents the upper pressure block, 5 represents the composite material melt, 6 represents the mold, 7 represents the lower pad block, 8 represents the lower support plate, and 9 represents the safety buffer. The working principle is as follows: The mold and insulation system are placed on the safety buffer. The purpose of adding the buffer is to mitigate pressure impact and maintain pressure, effectively reducing the risk of mold cracking and increasing safety. First, the lower pressure block is placed at the bottom of the mold to prevent melt overflow during die casting. Then, the stirred melt is poured into the mold. The mold is preheated at a certain temperature, and the upper pressure block and guide pillar are placed in sequence. Pressure is then applied until a specified value is reached, and after maintaining the pressure for a certain time, the pressure is released. Finally, the mold is inverted, and the composite material is removed.

[0043] Example 1:

[0044] This embodiment discloses a bi-level micro / nano ceramic particle-reinforced magnesium-based composite material. This magnesium-based composite material incorporates m-SiC... p and n-SiC p m-SiC p The average size is 8 μm, n-SiC p The average size is 60 nm, and the total amount of added silicon carbide particles is 10 wt%, with a mass ratio of micron-sized to nano-sized silicon carbide of 9:1. The magnesium alloy composition consists of 6.0% Zn, 3.0 wt% Al, and 0.5% Ca.

[0045] The specific preparation steps of the bi-level micro / nano ceramic particle reinforced magnesium-based composite material are as follows:

[0046] Step 1: Prepare a mixed solution of polyethylene glycol 400 with 2wt% ethanol. Pour micron and nano SiCp into the mixed solution and stir mechanically at 300r / min for 1.5h to obtain a silicon carbide mixed solution.

[0047] Step 2: Transfer the mixed solution to a drying oven and set the temperature to 60°C. After the solution has completely evaporated and the silicon carbide has completely dried, transfer it to a crucible and preheat it at 400-500°C for at least 3 hours.

[0048] Step 3: After melting the magnesium alloy at 750℃, lower the temperature of the alloy melt to 610℃ to a semi-solid state. Insert a preheated stirring paddle to half the height of the melt and start the stirring paddle at 1000r / min to form a stable vortex.

[0049] Step 4: Add the mixed silicon carbide particles to the melt within 6 minutes, stir at 1000 r / min for 2 minutes, then reduce the speed to 850 r / min and stir for 5 minutes, and finally reduce the speed to 680 r / min and stir for 5 minutes before stopping the stirring.

[0050] Step 5: Heat the melt to 700℃, stir at a low speed of 170r / min for 10min, then heat the melt to 715℃, pour it into a mold at 500℃, and solidify it under a pressure of 150MPa to obtain a magnesium-based composite material with dispersed particles and bi-level micro-nano ceramic particles.

[0051] The microstructure of the prepared bi-level micro / nano ceramic particle reinforced magnesium matrix composite material is as follows: Figure 2 As shown, compared to Comparative Example 1, the silicon carbide particles are more evenly distributed and have fewer internal defects.

[0052] Example 2:

[0053] This embodiment discloses a method for preparing SiCp-reinforced Mg-Zn-based composite materials. The elemental ratios are the same, and the preparation method is similar to that in Example 1, except that:

[0054] In step one, the concentration of polyethylene glycol 400 in the dispersant is 5 wt%.

[0055] The microstructure of SiCp-reinforced Mg-Zn-based composites is as follows: Figure 2 As shown.

[0056] Example 3:

[0057] This embodiment discloses a method for preparing SiCp-reinforced Mg-Zn-based composite materials. The elemental ratios are the same, and the preparation method is similar to that in Example 1, except that:

[0058] The mechanical powder feeding process in step four takes 10 minutes.

[0059] The microstructure of SiCp-reinforced Mg-Zn-based composites is as follows: Figure 2 As shown.

[0060] Example 4:

[0061] This embodiment discloses a method for preparing SiCp-reinforced Mg-Zn-based composite materials. The elemental ratios are the same, and the preparation method is similar to that in Example 1, except that:

[0062] In step three, the temperature of the melt during semi-solid stirring is 600℃.

[0063] The microstructure of SiCp-reinforced Mg-Zn-based composites is as follows: Figure 2 As shown.

[0064] Example 5:

[0065] This embodiment discloses a method for preparing SiCp-reinforced Mg-Zn-based composite materials. The elemental ratios are the same, and the preparation method is similar to that in Example 1, except that:

[0066] In step three, the temperature of the melt during semi-solid stirring is 620℃.

[0067] The microstructure of SiCp-reinforced Mg-Zn-based composites is as follows: Figure 2 As shown

[0068] Example 6:

[0069] This embodiment discloses a method for preparing SiCp-reinforced Mg-Zn-based composite materials. The elemental ratios are the same, and the preparation method is similar to that in Example 1, except that:

[0070] Step four, the staged stirring process for semi-solid mixing, is as follows: stir at 1100 r / min for 2 min, then reduce the speed to 800 r / min for 5 min, and finally reduce the speed to 700 r / min for 5 min.

[0071] Microstructure diagram of SiCp reinforced Mg-Zn based composite material as shown below Figure 2 As shown.

[0072] Example 7:

[0073] This embodiment discloses a method for preparing SiCp-reinforced Mg-Zn-based composite materials. The preparation method is similar to that in Example 1, except that:

[0074] After the semi-solid stirring is completed, step five involves heating the melt to 700℃ and stirring at a speed of 200r / min for 10 minutes.

[0075] The microstructure of SiCp-reinforced Mg-Zn-based composites is as follows: Figure 2 As shown.

[0076] Example 8:

[0077] This embodiment discloses a method for preparing SiCp-reinforced Mg-Zn-based composite materials. The preparation method is similar to that in Example 1, except that:

[0078] The elemental ratios are different, with elemental contents of 4.5wt% Zn, 2wt% Al, and 1wt% Ca.

[0079] The microstructure of SiCp-reinforced Mg-Zn-based composites is as follows: Figure 2 As shown.

[0080] Example 9:

[0081] This embodiment discloses a method for preparing SiCp-reinforced Mg-Zn-based composite materials. The preparation method is similar to that in Example 1, except that:

[0082] The elemental ratios are different, with the elemental contents being 7wt% Zn, 3wt% Al, and 0.5wt% Ca, while all other conditions are the same.

[0083] The microstructure of SiCp-reinforced Mg-Zn-based composites is as follows: Figure 2 As shown.

[0084] Comparative Example 1:

[0085] This comparative example discloses a method for preparing SiCp-reinforced Mg-Zn-based composite materials. The preparation method is similar to that in Example 1, except that:

[0086] Step five involves stirring at a high speed of 1000 rpm for 12 minutes, followed by solidification at 150 MPa. The resulting microstructure is as follows: Figure 3 As shown.

[0087] Comparative Example 2:

[0088] This comparative example discloses a method for preparing SiCp-reinforced Mg-Zn-based composite materials. The preparation method is similar to that in Example 1, except that:

[0089] Steps one and two are replaced with ball milling to mix micron and nano-sized silicon carbide particles, the microstructure of which is as follows: Figure 3 As shown.

[0090] Comparative Example 3:

[0091] This comparative example discloses a method for preparing SiCp-reinforced Mg-Zn-based composite materials. The preparation method is similar to that in Example 1, except that:

[0092] Step five employs a liquid stirring method, with a melt temperature of 650℃. Its microstructure is as follows: Figure 3 As shown.

[0093] Comparative Example 4:

[0094] This comparative example discloses a method for preparing SiCp-reinforced Mg-Zn-based composite materials. The preparation method is similar to that in Example 1, except that:

[0095] In step five, after stirring the semi-solid material, the temperature is raised to 700℃, and the mixture is stirred at 300 rpm for 10 minutes. Its microstructure is as follows: Figure 3 As shown.

[0096] Comparative Example 5:

[0097] This comparative example discloses a method for preparing SiCp-reinforced Mg-Zn-based composite materials. The preparation method is similar to that in Example 1, except that:

[0098] In step three, during semi-solid stirring, the distance between the stirring paddle and the bottom of the crucible is three-quarters of the melt height. Its microstructure is as follows: Figure 3 As shown.

[0099] Comparative Example 6:

[0100] This comparative example discloses a method for preparing SiCp-reinforced Mg-Zn-based composite materials. The preparation method is similar to that in Example 1, except that:

[0101] In step five, the staged mixing process is as follows: mix at 1000 rpm for 5 minutes, then reduce to 850 rpm for 6 minutes, and finally reduce to 680 rpm for 6 minutes. The resulting microstructure is as follows: Figure 3 As shown.

[0102] Comparative Example 7

[0103] This comparative example discloses a method for preparing SiCp-reinforced Mg-Zn-based composite materials. The preparation method is similar to that in Example 1, except that:

[0104] The elemental composition is different, with the following elemental contents: 1 wt% Zn, 0.5 wt% Al, and 2 wt% Ca. Testing revealed its yield strength, tensile strength, and elongation to be 100 MPa, 136 MPa, and 1.6%, respectively.

[0105] Comparative Example 8

[0106] This comparative example discloses a method for preparing SiCp-reinforced Mg-Zn-based composite materials. The preparation method is similar to that in Example 1, except that:

[0107] The elemental composition is different, with the following elemental contents: 10wt% Zn, 10wt% Al, and 2wt% Ca. Testing revealed its yield strength, tensile strength, and elongation to be 114 MPa, 162 MPa, and 2.2%, respectively.

[0108] Performance testing

[0109] The performance of the bi-level micro / nano ceramic particle reinforced magnesium matrix composites prepared in Examples 1-9 and the materials prepared in Comparative Examples 1-6 were tested respectively. The test results are as follows: Figure 2-5 As shown:

[0110] Figure 2 Microstructure diagram of the bi-dimensional silicon carbide particle-reinforced magnesium matrix composite material prepared under the conditions of the example; Figure 3The microstructure of the magnesium matrix composite material reinforced with bi-dimensional silicon carbide particles prepared under comparative conditions is shown in the figure. Figure 4 This is a comparison chart of the mechanical properties of the composite materials prepared under the conditions of the examples; Figure 5 This is a comparison chart of the mechanical properties of composite materials prepared under comparative conditions.

[0111] It is evident that chemical dispersion and staged stirring casting are effective methods for preparing Mg-Zn-based composite materials with well-dispersed particles and excellent performance. Currently, stirring casting is commonly used for the preparation of Mg-Al composites. Mg-Al alloys possess good fluidity and oxidation resistance, thus conventional stirring methods can be used to prepare composites with good performance. However, Mg-Zn alloys are prone to oxidation. Staged stirring is employed, involving initial dispersion under short-duration high-speed stirring, followed by a reduction in stirring rate for secondary dispersion, and finally, vortex-free stirring in a liquid state for further particle dispersion. The high surface area of ​​nanoparticles facilitates their aggregation, while chemical dispersion allows nanoparticles to adhere to micron-sized particles, effectively dispersing them. Staged stirring avoids the gas absorption problem caused by prolonged stirring at high rates, thus significantly reducing the oxidation level of the melt.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bi-level micro / nano ceramic particle reinforced magnesium-based composite material, characterized in that, include: The mixture comprises Mg-xZn-yAl-zCa and silicon carbide particles, wherein 2≤x≤8, 1≤y≤5, 0.3≤z≤1, and x, y, and z are mass percentages; wherein the silicon carbide particles include micron-sized silicon carbide and nano-sized silicon carbide, wherein the content of micron-sized silicon carbide is 5% to 10%, and the content of nano-sized silicon carbide is 0.3% to 1%.

2. The bi-level micro / nano ceramic particle reinforced magnesium-based composite material according to claim 1, characterized in that, The micron-sized silicon carbide has a size of 5–15 μm, and the nano-sized silicon carbide has a size of 40–80 nm.

3. A method for preparing the bi-level micro / nano ceramic particle reinforced magnesium-based composite material as described in claim 1 or 2, characterized in that, Includes the following steps: Step 1: Prepare the dispersant solution; Step 2: Pour the silicon carbide particles into the dispersant solution and disperse them by mechanical stirring so that the nanoparticles adhere to the surface of the micron particles. Step 3: Heat and dry the mixed silicon carbide solution until the liquid is completely evaporated to obtain dried mixed silicon carbide particles; Step 4: Melt the magnesium alloy at 700-750℃, then cool the melt to a semi-solid state. Insert the preheated stirring paddle into the melt, start the stirring paddle, and after a stable vortex is formed, add the preheated mixed silicon carbide particles. Step 5: Stir using a staged stirring method; Step 6: Heat to 700-700℃, use non-vortex stirring, heat the melt to 710-725℃, pour it into a mold preheated to 400-500℃, and solidify it under a pressure of 150-200MPa to obtain a bi-level micro-nano ceramic particle reinforced magnesium-based composite material.

4. The preparation method of the bi-level micro / nano ceramic particle reinforced magnesium-based composite material according to claim 3, characterized in that, In step one, the dispersant solution is a mixture of ethanol and polyethylene glycol 400.

5. The preparation method of the bi-level micro / nano ceramic particle reinforced magnesium-based composite material according to claim 3, characterized in that, In step two, the mass ratio of silicon carbide particles to dispersant is 1:3 to 5.

6. The method for preparing the bi-level micro / nano ceramic particle reinforced magnesium-based composite material according to claim 3, characterized in that, In step two, the silicon carbide particles include micron-sized silicon carbide particles and nano-sized silicon carbide particles, and the mass ratio of the micron-sized silicon carbide particles to the nano-sized silicon carbide particles is 4 to 14:

1.

7. The method for preparing the bi-level micro / nano ceramic particle reinforced magnesium-based composite material according to claim 3, characterized in that, In step four, the magnesium alloy is Mg-xZn-yAl-zCa, where 2≤x≤8, 1≤y≤5, 0.3≤z≤1, and x, y, and z are mass fractions.

8. The method for preparing the bi-level micro / nano ceramic particle reinforced magnesium-based composite material according to claim 3, characterized in that, In step four, the temperature of the preheated mixed silicon carbide particles is 400-500°C, and the preheating time is not less than 2 hours.

9. The method for preparing the bi-level micro / nano ceramic particle reinforced magnesium-based composite material according to claim 3, characterized in that, The specific operation of the graded stirring method in step five is as follows: first, stir at a high speed of 1000-1200 r / min for 1-3 minutes, then reduce the speed to 800-950 r / min and stir for 2-5 minutes, and finally reduce the speed to 600-750 r / min and stir for 3-5 minutes.

10. Use of the bi-level micro / nano ceramic particle reinforced magnesium matrix composite material according to claim 1 or 2 in the automotive field.

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