A method for preparing a multi-scale SiC particle heterostructure reinforced magnesium-based composite material

Abstract

The application relates to a preparation method of a multi-scale SiC particle heterostructure reinforced magnesium-based composite material, and belongs to the field of metal matrix composite materials and preparation thereof. In the application, a second phase is generated in-situ by adding rare earth elements, micron, submicron and nanoscale SiC reinforcing body particles form a heterostructure due to size difference, and after a subsequent plastic deformation process, the multi-scale reinforcing body particles form a layered distribution characteristic heterostructure, second phase strengthening, reinforcing body particle strengthening and heterostructure strengthening effects are generated, and the modulus and strength of the magnesium-based composite material are improved. Moreover, the magnesium-based composite material is prepared by using a stirring casting mode, the production process is shortened, the production cost is reduced, the magnesium-based composite material with high modulus and high strength is prepared, the application of the high-performance magnesium-based composite material is promoted, and the application range of the magnesium-based composite material in the fields of automobile industry and aerospace is expanded, which has important significance.

Description

Technical Field

[0001] The present invention belongs to the field of metal-based composite materials and their preparation, and particularly relates to a method for preparing a multi-scale SiC particle heterostructure reinforced magnesium-based composite material. Background Art

[0002] Magnesium alloy has low density (density ~1.8g / cm 3 ) and high specific strength are widely used in aerospace, automobile and other fields. However, since the modulus of magnesium alloy is only 45GPa, which is significantly lower than the elastic modulus of Al alloy (70GPa), and the density of Al alloy is about 1.5 times that of magnesium alloy (2.7g / cm 3 ), under the same stiffness design conditions, using magnesium alloys instead of aluminum alloys only reduces weight by 10-20%, which is not a significant effect. Therefore, the development of high-modulus, high-strength magnesium alloys is conducive to improving the weight reduction of magnesium alloy structural parts and has become one of the key issues that need to be addressed in the application of magnesium alloy materials.

[0003] Heterostructured materials, as an emerging material system, exhibit mechanical properties superior to homogeneous materials through variations in composition, phase, and microstructure, such as layered structures, gradient structures (in composition, grain size, or texture), bimodal structures, and harmonic structures. Their structural design draws inspiration from natural materials such as shells and bamboo. By designing the three-dimensional spatial distribution, geometry, and scale of the materials, and employing a multi-material integrated manufacturing process, they create high-performance, ultra-high-performance, and multi-performance materials and components with heterogeneous and regularly distributed internal structures. Based on their structural characteristics, heterogeneous, heterogeneous materials can be divided into three categories: The first category is heterogeneous materials formed by differences in grain size based on the Hall-Patch effect, primarily including gradient nanostructured materials, bimodal materials, and core-shell materials. The second category is dual-phase materials resulting from phase transitions leading to differences in crystal structure. The third category is layered heterogeneous materials formed by differences in hardness, softness, or size. Layered materials are composed of different hardnesses or components with significantly different sizes, exhibiting a layered distribution and consisting of layers of overlapping components. The preparation methods of layered structure materials generally include plastic deformation, plastic deformation + annealing, powder metallurgy + annealing, etc.

[0004] The elastic modulus of magnesium alloy is different from the strength and plasticity, and it is difficult to improve by regulating the chemical composition, phase type and distribution, grain size and the like, and at present, the effective method is to add high modulus reinforcing body particles to improve the elastic modulus of magnesium alloy. SiC particles are stable ceramic materials with high hardness and strength, and the production cost is low, and it is easy to prepare and secondary processing, and it is an ideal reinforcing body of magnesium matrix composite. The related research shows that the SiC particles can be added as reinforcing body to some composite materials to improve and enhance the performance of the alloy material, and the comprehensive performance can be improved, so that the application range of the magnesium alloy is expanded. Moreover, how to realize the continuous and rapid production of the magnesium matrix composite is another problem faced by the field. Among various preparation methods of metal matrix composites, the stir casting method has the characteristics of low cost and large-scale production, and can realize low-cost and short-process industrial production.

[0005] Based on this, the application provides a preparation method of a multi-scale SiC particle heterogeneous structure reinforced magnesium matrix composite, rare earth elements are introduced by composition design to generate in-situ generated second phases, and the size difference heterogeneous structure is formed by micron, submicron and nanoscale SiC particles, and the subsequent plastic deformation process forms the layered distribution characteristic heterogeneous structure, the second phase strengthening, reinforcing body particle strengthening and heterogeneous structure strengthening effects are generated, the modulus and strength of the magnesium matrix composite are improved, the magnesium matrix composite is prepared by the stir casting method, the production process is shortened, the production cost is reduced, the magnesium matrix composite with high modulus and high strength is prepared, and the application range of the magnesium matrix composite is expanded. SUMMARY

[0006] The application aims at the problems in the prior art, and provides a preparation method of a multi-scale SiC particle heterogeneous structure reinforced magnesium matrix composite.

[0007] Firstly, the application generates in-situ generated Al2Y second phases by adding trace Y elements, and the modulus and strength of the material are improved, wherein the in-situ generated nanoscale precipitated phase Al2Y has high modulus, based on the Hashin-Shtrikman elastic theory model, the modulus of the material can be improved in cooperation with the added high modulus SiC reinforcing body particles, and the material has a double reinforcing body configuration of "in-situ generated nanoscale precipitated phase Al2Y+added SiC reinforcing body", and the modulus of the magnesium matrix composite is significantly improved.

[0008] Secondly, micron, submicron and nanoscale SiC particles with different particle sizes are added, the modulus of the material is improved by adding the reinforcing body particles, and the strength of the material is improved by forming the layered heterogeneous structure due to the size difference of the multi-scale SiC particles.

[0009] Thirdly, by performing air blowing, stirring and ultrasonic treatment during the melting process, the SiC particle reinforcement can be suspended inside the melt, which improves the dispersion and uniformity of the composite ingot reinforcement particles and further enhances the heterogeneous structure strengthening effect of the SiC particles.

[0010] Finally, plastic deformation further evenly disperses the SiC particles, resulting in a layered distribution of micron- and nanometer-sized SiC reinforcement particles along the extrusion direction. Submicron SiC transitions between the coarse and fine layers, forming a heterogeneous structure with layered distribution characteristics. This further enhances the SiC particle heterogeneous reinforcement effect. This preparation method can produce magnesium-based composites with high modulus and strength.

[0011] The purpose of the present invention can be achieved by the following solutions:

[0012] The present invention provides a method for preparing a multi-scale SiC particle heterostructure reinforced magnesium-based composite material, comprising the following steps:

[0013] S1, ball-milling micron-, submicron-, and nanometer-sized SiC particles with Al powder particles to obtain SiC-Al mixed powder, and then cold-pressing to obtain a SiC-Al composite powder prefabricated block;

[0014] S2. Weigh other raw materials according to the alloy ratio, smelt them, add the SiC-Al composite powder prefabricated block into the smelted melt, continue smelting, and then cast to obtain a composite material ingot; the other raw materials include Mg element, Al element, and Mg-Y master alloy;

[0015] S3. The composite material ingot is homogenized and hot extruded to obtain a multi-scale SiC particle heterostructure reinforced magnesium-based composite material.

[0016] As an embodiment of the present invention, in step S1, before ball milling, the SiC particles of micron, submicron, and nanometer sizes and the Al powder are ultrasonically cleaned, and oil stains and impurities on the surface of the particles are removed using anhydrous ethanol.

[0017] As an embodiment of the present invention, in step S1, the particle size of the micron-sized SiC particles is 1-20 μm, the particle size of the submicron-sized SiC particles is 0.2-0.4 μm, and the particle size of the nano-sized SiC particles is 50-70 nm.

[0018] As one embodiment of the present invention, in step S1, the SiC particles include, by mass percentage, 30-40% micron-sized SiC particles, 30-40% submicron-sized SiC particles, and 30-40% nano-sized SiC particles. The closer the content, the more uniform the distribution and the better the reinforcement effect.

[0019] The present invention adopts micron-sized particles with larger particle sizes, and its agglomeration phenomenon is weakened compared with small-sized nano-sized particles. In addition, by increasing the proportion of nano-sized and submicron-sized particles (40%, 30%), the "coarse-fine" distribution characteristics are more obvious, thereby significantly improving the modulus and mechanical properties of magnesium-based composite materials. The present invention uses nano-scale and micron-scale SiC reinforcement particles. During the stirring casting process, due to the large difference in particle size, the nano-scale SiC particles are easily agglomerated and have poor dispersibility. Nano-scale, submicron-scale and micron-scale SiC particles are ball-milled and mixed with Al powder, and a prefabricated block is obtained by cold pressing. During the preparation process of the stirring casting magnesium-based composite material, a multi-level reinforcement particle distribution characteristic of "nano-scale-submicron-scale, submicron-micron-scale" is generated. Compared with the "nano-micron-scale" particle distribution, the three different-scale reinforcement particles are evenly dispersed in the melt through the buffering effect of the submicron-scale particles preferentially agglomerating with the nano-scale particles. Compared with the simultaneous addition of nano-scale and micron-scale SiC reinforcement particles, the agglomeration phenomenon is weakened, thereby improving the effect of heterogeneous structure strengthening.

[0020] As an embodiment of the present invention, in step S1 , the particle size of the Al powder particles is 10 to 100 μm.

[0021] As an embodiment of the present invention, in step S1, the mass ratio of SiC particles to Al powder particles is 2:1 to 1:1. Using a higher Al content will result in an excessively high Al content in the alloy, which will reduce elongation and increase density.

[0022] As an embodiment of the present invention, in step S1, the rotation speed is 100-400 rpm, the ball milling time is 4-24 hours, and the ball-to-material ratio is 6:1-20:1.

[0023] If SiC particles are added directly to the melt, the wettability of the reinforcement particles to the matrix alloy is poor, resulting in poor dispersion uniformity of the reinforcement particles and lower modulus and mechanical properties of the material. The present invention uses low-energy mixed powder ball milling to form a reinforcement particle pretreatment method with the characteristics of a "metal carrier-core-shell structure", which improves the uniformity and wettability of the reinforcement SiC particles in the matrix alloy, making the nano-scale, submicron-scale, and micron-scale SiC reinforcement particles evenly distributed and dispersed, avoiding agglomeration of the reinforcement particles when added, and enhancing the strengthening effect of the "coarse-fine-coarse-fine" layered heterogeneous structure characteristics, so that the magnesium-based composite material has a higher modulus while still maintaining good mechanical properties.

[0024] As one embodiment of the present invention, in step S1, the cold pressing pressure is 50-80 MPa, and the holding time is 10-30 minutes. The mold used for cold pressing to prepare the composite powder preform is a stainless steel cylindrical mold. Cold pressing reduces the volume of the Al powder and SiC particle powders after ball milling. After cold pressing into a block, the preforms are easily added to the melt during smelting.

[0025] As an embodiment of the present invention, in step S2, the smelting is performed under a protective atmosphere.

[0026] In one embodiment of the present invention, in step S2, the SiC-Al composite powder preform is added by mixing the SiC-Al composite powder preform with Ar gas and adding the mixture to the melt via a rotary injection device. The Ar gas flow rate during rotary injection is 1.6 to 2 L / h, and the rotation speed is 200 to 400 rpm.

[0027] As one embodiment of the present invention, in step S2, while continuing to smelt, the melt is subjected to low-speed and high-speed mechanical stirring, supplemented by ultrasonic treatment. The low-speed stirring time is 2 to 4 minutes at a rotation speed of 200 to 400 rpm; the high-speed stirring time is 10 to 20 minutes at a rotation speed of 600 to 800 rpm; and the ultrasonic treatment time is 20 to 40 minutes at a power of 400 to 600 W.

[0028] As an embodiment of the present invention, in step S3, the homogenization temperature is 400-420° C., and the holding time is 18-20 h.

[0029] As an embodiment of the present invention, in step S3, the extrusion temperature of the hot extrusion is 320-350° C., and the extrusion ratio is 16:1-25:1.

[0030] As an embodiment of the present invention, the multi-scale SiC particle heterostructure reinforced magnesium-based composite material obtained in step S3 comprises, by mass percentage, 6-12% Al, 0.8-1.2% Y, 8-12% SiC particles, and the balance Mg.

[0031] If the content of Y element is increased, due to the limited solid solubility of Y element, Y element will aggregate, and the in-situ self-generated AlY2 phase cannot be obtained, and the reinforcement effect cannot be achieved.

[0032] The multi-scale SiC particle heterostructure reinforced magnesium-based composite material comprises, by mass percentage, 6-12% Al, 0.5-2% Zn, 0.8-1.2% Y, 8-12% SiC particles, and the balance Mg. More preferably, the composition is 9% Al, 1% Zn, 1% Y, 10% SiC particles, and the balance Mg.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1) The matrix alloy is Mg-9Al-1Zn-1Y. Compared with Mg-9Al-1Zn alloy (AZ91), the added Y element and Al element generate Al2Y in-situ self-generated second phase particles, which enhances the modulus and strength of the material.

[0035] 2) Due to the size differences of micron-, submicron-, and nanometer-sized SiC particles, a heterogeneous structure is formed, which produces a heterogeneous structural strengthening effect. Although the plasticity is slightly reduced, its yield strength and tensile strength are improved compared with AZ91 alloy; and due to the addition of SiC particles, its modulus is greatly improved.

[0036] 3) During the vacuum melting process, the melt is stirred by rotary blowing, bell jar and ultrasonic treatment, so that the SiC particle reinforcement can be suspended inside the melt, thereby improving the dispersion and uniformity of the composite material ingot reinforcement particles, and further enhancing the heterogeneous structure strengthening effect of micron, submicron and nanometer SiC particles.

[0037] 4) Then, through subsequent plastic deformation, the SiC particles of different sizes are further dispersed evenly, and due to the influence of the extrusion direction, the particles are arranged along the extrusion direction, and the particles show a layered distribution characteristic of "coarse, fine, coarse, fine"; among them, one layer is micron-sized SiC particles, one layer is submicron-sized SiC particles, and one layer is nano-sized SiC particles, which alternate with each other and show a layered distribution characteristic, forming a heterogeneous structure with layered distribution characteristics, further enhancing the strengthening effect of the SiC particle heterogeneous structure, such as Figure 4 shown.

[0038] 5) Therefore, by adding rare earth elements to generate an in-situ autogenous second phase, adding multi-scale SiC particles, and undergoing subsequent plastic deformation, the effects of second-phase strengthening, particle reinforcement, and heterogeneous structure strengthening are achieved, simultaneously enhancing the modulus and strength of the magnesium-based composite. This method enables the preparation of magnesium-based composites with high modulus and strength, improving the mechanical properties of high-modulus magnesium-based composites and having important implications for expanding the application of magnesium-based composites in fields such as aerospace. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0040] Figure 1 Schematic diagram of the preparation process of SiC-Al composite powder prefabricated blocks.

[0041] Figure 2 Young's modulus and density of the magnesium-based composite material prepared by the present invention.

[0042] Figure 3 The room temperature mechanical properties of the magnesium-based composite material prepared in the present application.

[0043] Figure 4 The metallographic picture of the magnesium-based composite material prepared in Example 3 of the present application;

[0044] Figure 5 The picture of the microstructure of the magnesium-based composite material prepared in Example 3 of the present application, which is perpendicular to the extrusion direction. DETAILED DESCRIPTION

[0045] The present application will be described in detail below with specific examples. The following examples will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application. These are all within the scope of protection of the present application.

[0046] Example 1

[0047] This embodiment relates to a preparation method of a multi-scale SiC particle heterostructure reinforced magnesium-based composite material, wherein the mass percentage of each component is Al: 9%, Zn: 1%, Y: 1%, SiC particle: 10%, and the balance is Mg. The multi-scale SiC particles used have diameters of micrometer level: 20 μm, sub-micrometer level: 0.4 μm, and nanometer level: 70 nm, and the micrometer Al powder used has a diameter of 100 μm.

[0048] The preparation method of the multi-scale SiC particle heterostructure reinforced magnesium-based composite material is as follows:

[0049] 1) Use an ultrasonic cleaning device to ultrasonically clean the micrometer, sub-micrometer and nanometer SiC particles of different particle sizes and the micrometer Al powder in anhydrous ethanol, to sufficiently remove oil stains, impurities and oxides on the surface of the particles, and then perform filtration and drying treatment.

[0050] 2) Mix the SiC particles of different particle sizes and the Al powder on a planetary ball mill to prepare SiC-Al mixed powder, and the mass ratio of the mixed powder is SiC: Al = 2: 1, wherein the mass percentage of the micrometer, sub-micrometer and nanometer SiC particles is 30%, 30% and 40% respectively; the rotation speed is 400 rpm, the ball milling time is 4 h, and the ball-to-material ratio is 10: 1.

[0051] 3) Cold pressing the mixed powders prepared by ball milling micron-, submicron-, and nanometer-sized SiC particles with Al powder; using a stainless steel cylindrical mold, the ball-milled mixed powders were added to the mold and cold pressed at a pressure of 50 MPa for 30 minutes to obtain SiC-Al composite powder preforms of different particle sizes for subsequent smelting and preparation of magnesium-based composite materials. Figure 1 Schematic diagram of the preparation process of multi-scale SiC-Al composite powder prefabricated blocks for preparing magnesium-based composite materials according to the present invention.

[0052] 4) Melting process under protective atmosphere: Melting is carried out in a vacuum melting furnace. First, magnesium, Al, zinc, and magnesium-yttrium master alloy are melted in proportion under a protective atmosphere, and then stirred at 680°C for 5 minutes. Next, the SiC-Al composite powder preform and Ar gas are mixed and added to the melt through a rotary blowing device. The Ar gas flow rate is 2 L / h and the rotation speed is 400 rpm. At the same time, a bell jar is used to cover it and stir it so that the particle reinforcement can be suspended in the melt. Secondly, the composite powder preform is added, and the melt is mechanically stirred and ultrasonically treated by a stirring device in a vacuum melting furnace. Specifically, low-speed stirring for 6 minutes, a speed of 400 rpm, then high-speed stirring for 20 minutes, a speed of 800 rpm, and then ultrasonic treatment for 40 minutes at a power of 600 W. Finally, when the temperature is raised to 720°C, it is poured into a steel mold to obtain a composite material ingot.

[0053] 5) The composite material ingot was homogenized and hot extruded, with a homogenization temperature of 420°C, a holding time of 20 h, an extrusion temperature of 350°C, and an extrusion ratio of 25:1.

[0054] The modulus of the modified multi-scale SiC particle reinforced magnesium matrix composite prepared according to Example 1 is 57 GPa and the density is 1.83 g / cm 3 ,like Figure 2 As shown; the room temperature mechanical properties are: yield strength 231MPa, tensile strength 343MPa, elongation 8.6%, as shown Figure 3 The test specimens and methods for tensile properties are based on the standard GB / T228.1-2010, and the test specimens and methods for density and elastic modulus are based on the standard GB / T22315-2008.

[0055] Example 2

[0056] The embodiment relates to a preparation method of a multi-scale SiC particle heterostructure reinforced magnesium-based composite material, wherein the mass percentage of each component is as follows: Al: 9%, Zn: 1%, Y: 1%, SiC particle: 10%, and the balance is Mg. The diameters of the multi-scale SiC particles are as follows: micron level: 1 mu m, submicron level: 0.2 mu m, and nanometer level: 50 nm; and the diameter of the micron Al powder is 100 mu m.

[0057] The preparation method of the multi-scale SiC particle heterostructure reinforced magnesium-based composite material is as follows:

[0058] 1) An ultrasonic cleaning device is used to perform ultrasonic cleaning treatment on micron, submicron and nanometer SiC particles with different particle sizes and micron Al powder in anhydrous ethanol, so that oil stains, impurities and oxides on surfaces of the particles are removed, and then the particles are filtered and dried.

[0059] 2) The SiC particles with different particle sizes and the Al powder are ball milled on a planetary ball mill to prepare SiC-Al mixed powder, and the mass ratio of the mixed powder is SiC: Al = 2: 1, wherein the mass percentage of the micron, submicron and nanometer SiC particles is 30%, 30% and 40% respectively; the rotating speed is 400 rpm, the ball milling time is 4 h, and the ball-to-material ratio is 10: 1.

[0060] 3) The mixed powder prepared by ball milling the micron, submicron and nanometer SiC particles and the Al powder is subjected to cold pressing treatment; the mixed powder after ball milling is added into a stainless steel cylindrical mold for cold pressing treatment, the cold pressing pressure is 50 MPa, and the pressure maintaining time is 30 min, so that the SiC-Al composite powder preform block with different particle sizes is obtained and used for subsequent melting preparation of the magnesium-based composite material. Figure 1 The preparation process of the multi-scale SiC-Al composite powder preform block for the magnesium-based composite material is shown in the figure.

[0061] 4) Under the protection of atmosphere, the melting process is carried out in a vacuum melting furnace, first, magnesium, Al, zinc, magnesium-yttrium intermediate alloy are melted in the protection of atmosphere according to the proportion, then stirring at 680℃ for 5min; Next, the SiC-Al composite powder preform and Ar gas are mixed and added to the melt through the rotating spray device, the Ar gas flow is 1.6L / h, the rotating speed is 200rpm, at the same time, the bell jar is used to cover it and the stirring is used to make the particle reinforcement suspended in the melt; Secondly, the composite powder preform is added, and the melt is mechanically stirred and ultrasonically treated by the stirring device in the vacuum melting furnace, specifically: first low speed stirring for 2min, the rotating speed is 200rpm, then high speed stirring for 10min, the rotating speed is 600rpm, and then ultrasonic treatment for 20min, the power is 400W; Finally, when the temperature rises to 720℃, it is poured into a steel mold to obtain a composite ingot.

[0062] 5) The composite ingot is subjected to homogenization treatment and hot extrusion, the homogenization temperature is 420℃, the holding time is 20h, the extrusion temperature is 350℃, and the extrusion ratio is 25:1.

[0063] The modulus of the deformed multi-scale SiC particle reinforced magnesium matrix composite prepared according to example 2 is 61GPa, and the density is 1.84g / cm 3 As shown in Figure 2 ; the room temperature mechanical properties are: yield strength 238MPa, tensile strength 385MPa, elongation 5.6%, as shown in Figure 3 ; the test sample and method of tensile properties are according to standard GB / T228.1-2010, and the test sample and method of density and elastic modulus are according to standard GB / T22315-2008.

[0064] Example 3

[0065] This example relates to a method for preparing a multi-scale SiC particle heterostructure reinforced magnesium matrix composite, in which the mass percentage of each component is Al: 9%, Zn: 1%, Y: 1%, SiC particle: 10%, and the balance is Mg. The multi-scale SiC particles used have diameters of: micron level: 1μm, submicron level: 0.4μm, and nanometer level: 50nm, and the micron Al powder used has a diameter of 100μm.

[0066] The method for preparing the multi-scale SiC particle heterostructure reinforced magnesium matrix composite is as follows:

[0067] 1) Use ultrasonic cleaning equipment to ultrasonically clean micron, submicron and nanometer SiC particles of different particle sizes and micron Al powder in anhydrous ethanol, and then filter and dry.

[0068] 2) SiC particles of different particle sizes were ball-milled with Al powder in a planetary ball mill to prepare a SiC-Al mixed powder. The mass ratio of the mixed powder was SiC:Al = 2:1, wherein the mass percentages of micron-sized, submicron-sized, and nanometer-sized SiC particles were 30%, 30%, and 40%, respectively. The rotation speed was 400 rpm, the ball-milling time was 4 h, and the ball-to-material ratio was 10:1.

[0069] 3) Cold pressing the mixed powders prepared by ball milling micron-, submicron-, and nanometer-sized SiC particles with Al powder; using a stainless steel cylindrical mold, the ball-milled mixed powders were added to the mold and cold pressed at a pressure of 50 MPa for 30 minutes to obtain SiC-Al composite powder preforms of different particle sizes for subsequent smelting and preparation of magnesium-based composite materials. Figure 1 Schematic diagram of the preparation process of multi-scale SiC-Al composite powder prefabricated blocks for preparing magnesium-based composite materials according to the present invention.

[0070] 4) Melting process under protective atmosphere: Melting is carried out in a vacuum melting furnace. First, magnesium, Al, zinc, and magnesium-yttrium master alloy are melted in proportion under a protective atmosphere, and then stirred at 680°C for 5 minutes; then, the SiC-Al composite powder preform and Ar gas are mixed and added to the melt through a rotary blowing device. The Ar gas flow rate is 1.8 L / h and the rotation speed is 300 rpm. At the same time, a bell jar is used to cover it and stir it so that the particle reinforcement can be suspended in the melt; secondly, the composite powder preform is added, and the melt is mechanically stirred and ultrasonically treated by a stirring device in a vacuum melting furnace, specifically: first, low-speed stirring for 4 minutes, a speed of 300 rpm, then high-speed stirring for 15 minutes, a speed of 700 rpm, and then ultrasonic treatment for 30 minutes, with a power of 500 W; finally, when the temperature is raised to 720°C, it is poured into a steel mold to obtain a composite material ingot.

[0071] 5) The composite material ingot was homogenized and hot extruded, with a homogenization temperature of 420°C, a holding time of 20 h, an extrusion temperature of 350°C, and an extrusion ratio of 25:1.

[0072] The modulus of the modified multi-scale SiC particle reinforced magnesium matrix composite prepared according to Example 3 is 62 GPa and the density is 1.88 g / cm 3 ,like Figure 2 As shown; the room temperature mechanical properties are: yield strength 242MPa, tensile strength 390MPa, elongation 4.7%, as shown Figure 3The test specimens and methods for tensile properties are in accordance with the standard GB / T228.1-2010, and the test specimens and methods for density and elastic modulus are in accordance with the standard GB / T22315-2008. The metallographic picture of the magnesium-based composite material prepared in Example 3 of the present invention is shown in FIG. Figure 4 As shown in the figure, the black particles are micron-sized SiC particles. If you continue to zoom in, you will find black submicron-sized and nano-sized particles, which show a "coarse-fine" layered distribution along the extrusion direction. The structure of the magnesium-based composite material perpendicular to the extrusion direction is shown in the figure. Figure 5 shown.

[0073] Comparative Example 1

[0074] This comparative example relates to a preparation method of a multi-scale SiC particle heterostructure reinforced magnesium-based composite material, which is basically the same as Example 1, except that: no Y element is included and the SiC particles account for 11%.

[0075] The magnesium-based composite material prepared by this method has a yield strength of 202 MPa, a tensile strength of 316 MPa, an elongation of 10.2%, an elastic modulus of 55 GPa, and a density of 1.83 g / cm 3 .

[0076] It can be concluded from the experimental data of Comparative Example 1 that, although the SiC particles are increased to ensure the content of the reinforcing phase, the overall performance of the magnesium-based composite material is reduced due to the lack of the synergistic effect of the Y element.

[0077] Comparative Example 2

[0078] This comparative example relates to a method for preparing a multi-scale SiC particle heterostructure reinforced magnesium-based composite material, which is basically the same as Example 1, except that SiC particles of different particle sizes and Al powder are not prepared into prefabricated blocks, but are directly added to the melt.

[0079] The magnesium-based composite material prepared by this method has a yield strength of 212 MPa, a tensile strength of 328 MPa, an elongation of 6.5%, an elastic modulus of 53 GPa, and a density of 1.82 g / cm 3 .

[0080] It can be concluded from the experimental data of Comparative Example 2 that direct addition of SiC particles results in poor dispersion, aggregation of SiC particles, and degradation of material properties.

[0081] Comparative Example 3

[0082] This comparative example relates to a preparation method of a multi-scale SiC particle heterostructure reinforced magnesium-based composite material, which is basically the same as Example 1, except that the mass percentages of micron-scale, submicron-scale and nanometer-scale SiC particles are 40%, 10% and 50% respectively.

[0083] The magnesium-based composite material prepared by this method has a tensile strength of 219 MPa, a yield strength of 332 MPa, an elongation of 5.8%, an elastic modulus of 56 GPa, and a density of 1.85 g / cm 3 .

[0084] The mechanical properties of the composite material in this comparative example are reduced, which may be due to the low content of submicron SiC particles, resulting in a poor transition between the "coarse and fine" layered structures, poor heterogeneous structural strengthening effect, and affected material performance.

[0085] Comparative Example 4

[0086] This comparative example relates to a preparation method of a multi-scale SiC particle heterostructure reinforced magnesium-based composite material, which is basically the same as Example 1, except that the mass percentages of micron-sized, submicron-sized and nanometer-sized SiC particles are 15%, 15% and 70% respectively.

[0087] The magnesium-based composite material prepared by this method has a yield strength of 211 MPa, a tensile strength of 338 MPa, an elongation of 5.2%, an elastic modulus of 53 GPa, and a density of 1.86 g / cm 3 .

[0088] The mechanical properties of the composite material in this comparative example are reduced, which may be due to the low content of micron- and submicron-sized SiC particles and the large difference between the content and that of nano-sized SiC particles, resulting in unclear "coarse and fine" layered structures and poor heterogeneous structural reinforcement, which affects the performance of the material.

[0089] Comparative Example 5

[0090] This comparative example relates to a preparation method of a multi-scale SiC particle heterostructure reinforced magnesium-based composite material, which is basically the same as Example 1, except that the Y element is replaced by the Gd element.

[0091] The magnesium-based composite material prepared by this method has a yield strength of 216 MPa, a tensile strength of 322 MPa, an elongation of 6.3%, an elastic modulus of 54 GPa, and a density of 1.85 g / cm 3 .

[0092] The Y element is replaced by the Gd element, but the Gd element is easy to agglomerate, the generated Al2Gd phase is small, and the enhancement effect is not obvious.

[0093] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a multi-scale SiC particle heterostructure reinforced magnesium-based composite material, characterized in that: The steps include: S1, ball-milling micron-, submicron-, and nanometer-sized SiC particles with Al powder particles to obtain SiC-Al mixed powder, and then cold-pressing to obtain a SiC-Al composite powder prefabricated block; S2. Weigh other raw materials according to the alloy ratio, smelt them, add the SiC-Al composite powder prefabricated block into the smelted melt, continue smelting, and then cast to obtain a composite material ingot; the other raw materials include Mg element, Al element, and Mg-Y master alloy; S3, homogenizing and hot extruding the composite ingot to obtain a multi-scale SiC particle heterostructure reinforced magnesium-based composite material; In step S1, the particle size of the micron-sized SiC particles is 1 to 20 μm, the particle size of the submicron-sized SiC particles is 0.2 to 0.4 μm, and the particle size of the nano-sized SiC particles is 50 to 70 nm. In terms of mass percentage, the SiC particles include: 30-40% micron-sized SiC particles, 30-40% submicron-sized SiC particles, and 30-40% nano-sized SiC particles.

2. The method for preparing a multi-scale SiC particle heterostructure reinforced magnesium-based composite material according to claim 1, characterized in that: In step S1 , the particle size of the Al powder particles is 10 to 100 μm.

3. The method for preparing a multi-scale SiC particle heterostructure reinforced magnesium-based composite material according to claim 1, characterized in that: In step S1 , the mass ratio of SiC particles to Al powder particles is 2:1 to 1:

1.

4. The method for preparing a multi-scale SiC particle heterostructure reinforced magnesium-based composite material according to claim 1, characterized in that: In step S1, the rotation speed is 100-400 rpm, and the ball milling time is 4-24 hours.

5. The method for preparing a multi-scale SiC particle heterostructure reinforced magnesium-based composite material according to claim 1, characterized in that: In step S1 , the pressure of the cold pressing treatment is 50 to 80 MPa, and the holding time is 10 to 30 minutes.

6. The method for preparing a multi-scale SiC particle heterostructure reinforced magnesium-based composite material according to claim 1, characterized in that: In step S2 , the SiC-Al composite powder preform is added by mixing the SiC-Al composite powder preform with Ar gas and adding the mixture into the melt through a rotary blowing device.

7. The method for preparing a multi-scale SiC particle heterostructure reinforced magnesium-based composite material according to claim 1, characterized in that: In step S2, while continuing to smelt, the melt is subjected to low-speed mechanical stirring, high-speed mechanical stirring, and then ultrasonic treatment; The low-speed stirring time is 2 to 4 minutes, the rotation speed is 200 to 400 rpm; the high-speed stirring time is 10 to 20 minutes, the rotation speed is 600 to 800 rpm; the ultrasonic treatment time is 20 to 40 minutes, the power is 400 to 600W.

8. The method for preparing a multi-scale SiC particle heterostructure reinforced magnesium-based composite material according to claim 1, characterized in that: In step S3, the homogenization temperature is 400-420°C and the holding time is 18-20 hours; And / or, in step S3, the extrusion temperature of the hot extrusion is 320-350° C., and the extrusion ratio is 16:1-25:

1.

9. The method for preparing a multi-scale SiC particle heterostructure reinforced magnesium-based composite material according to claim 1, characterized in that: The multi-scale SiC particle heterostructure reinforced magnesium-based composite material obtained in step S3 comprises, by mass percentage, 6-12% Al, 0.8-1.2% Y, 8-12% SiC particles, and the balance Mg.

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