WO2021035776A1

WO2021035776A1 - Method for preparing magnesium-based composite material

Info

Publication number: WO2021035776A1
Application number: PCT/CN2019/104192
Authority: WO
Inventors: 乐启炽; 赵大志; 李小强; 任良; 宝磊; 王彤
Original assignee: 东北大学
Priority date: 2019-08-29
Filing date: 2019-09-03
Publication date: 2021-03-04
Also published as: CN110438373B; US20210254194A1; CN110438373A

Abstract

A method for preparing a magnesium-based composite material, comprising the following steps: (1) preparing magnesium ingot as a raw material; and preparing a salt flux and a reinforcement; (2) placing the salt flux in a crucible and heating same to prepare a salt flux melt; and adding the reinforcement; (3) pouring the product into a crucible at normal temperature, and cooling same to normal temperature to obtain a precursor; (4) pre-heating an iron crucible to a red heat state, and adding raw materials and melting same at 953 to 1043K; (5) putting the precursor into the raw material melt, stirring, then adding a refining agent under the condition of a temperature of 953 to 993K, stirring and refining same, controlling the temperature, and standing the mixture to form scum and a melt; and (6) removing the scum, lowering the temperature to 973 to 982K and performing casting. The method makes the reinforcement uniformly dispersed in the molten salt, so that the reinforcement is easily uniformly dispersed in a matrix; has a simple process and low costs, and can be used for preparing a magnesium-based composite structural member having a large volume, and the product of which can be automated.

Description

Method for preparing magnesium-based composite material

Technical field

The invention relates to a method for preparing a composite material, in particular to a method for preparing a magnesium-based composite material.

Background technique

Magnesium alloy has the advantages of low density, high specific strength, and excellent vibration damping, electromagnetic shielding and machining performance. It is an ideal material for lightweight structure. In recent years, the research and application of magnesium alloys have received great attention. However, magnesium alloys also have problems such as great difficulty in melting and casting, difficult plastic deformation, poor high temperature creep resistance, and poor corrosion resistance; among them, low strength and easy yield deformation are an important reason for the limitation of magnesium alloy application fields. Generally, it can only be used as a secondary force component, which severely restricts its application fields; therefore, it is urgent to produce high-performance, low-cost, high-performance, and lightweight magnesium-based composite materials.

Compared with traditional magnesium and its alloys, magnesium-based composites not only have excellent mechanical properties, but also have some special properties and other good comprehensive properties; at present, the main method of preparing reinforced magnesium-based composites is traditional mechanical stirring. Casting method, squeeze casting method, injection molding method, in-situ composite method, etc.

The traditional mechanical stirring casting method is to add particles, whiskers, fibers and other reinforcements into the molten metal, and use mechanical stirring to make the reinforcements evenly distributed in the matrix. The advantages of the traditional mechanical stirring casting method are its low cost, simple process flow, mass production and mass production, and it is widely used in aerospace, automobile manufacturing and other industries. How to distribute the reinforcement uniformly in the molten metal is a key issue for the preparation of magnesium-based composites; however, most reinforcements often agglomerate or precipitate when entering the molten metal, making it difficult to evenly disperse in the melt. In addition, during the stirring process, gas impurities will be mixed with the stirring, and the reinforcement particles will increase the melt viscosity, making it difficult for the gas to escape, so the requirements for mechanical stirring are very high. This phenomenon occurs when the reinforcement is in the melt; the essence is that there is a difference in density between the reinforcement and the metal, so specific gravity segregation is bound to occur; the reinforcement has poor wettability for liquid metal, and it is impossible to be very good. Ground is dispersed in the matrix.

The squeeze casting method is a precision casting method that uses high pressure to fill and solidify liquid metal or semi-solid metal. First, the reinforcement is preformed, heated and then poured into the molten metal or melt, and then pressed in with a mold and cooled. Obtain composite castings. The squeeze casting method can reduce the influence of gas impurities on the quality of products, and has low requirements on wettability, and can obtain dense and uniform castings. The volume fraction of reinforcements that can be added is also increased, which can reach 30-50%. Significantly improve the performance of composite materials. However, there is a problem that the pressure affects the quality of the casting. When the pressure is high, the molten magnesium will flow turbulently, causing magnesium oxidation and gas retention; when the pressure is low, part of the gas cannot be removed, resulting in the phenomenon that the casting is not dense. In addition, the squeeze casting method cannot produce large-volume castings, nor can it be mass-automatically produced.

The injection molding method uses rare gas to atomize molten metal for spraying, mix with the reinforcement conveyed by the rare gas at the other end, and deposit and cool on the platform to obtain composite parts. The injection molding method uses rapid metal solidification technology to inhibit the growth of crystal grains and the formation of segregation, so that the crystal grains are refined and the reinforcements are evenly distributed. Atomized metal and mixed deposition are the two major influencing factors of spray molding. The process of atomizing metal is accompanied by gas transmission, which makes the parts often have a large porosity and shrinkage; if the solidification is too fast after deposition The composite effect of the reinforcement and the matrix is not good or even does not occur. If the solidification is slow, it will cause uneven distribution of the reinforcement and even segregation; and the injection molding method, as a new type of composite material preparation method, is costly, so it is not Suitable for automated mass production.

The in-situ composite method is a new method of preparing metal matrix composite materials; this method does not directly add reinforcements, but uses chemical reactions or other special reactions to generate reinforcements in the melt, nucleate and grow All are completed in the matrix, so there is no incompatibility or poor combination with the matrix, thereby avoiding the influence of wetting conditions and making the composite material uniform and pure. This method has low cost, simple process flow, and good quality of the parts obtained; however, the method of using chemical reactions to generate reinforcements has the limitation of a small number of reinforcements, and therefore cannot meet the requirements of mass production.

The method of powder metallurgy is to mix metal powder and reinforcement powder by means of ball milling, and then sinter it by hot pressing under vacuum conditions. The powder metallurgy method does not need to heat the matrix alloy to a molten state, so that the matrix and the reinforcement can avoid the reaction of the interface. After mixing, the reinforcement is uniformly distributed in the matrix and plays a good strengthening effect. However, due to the large differences in the size, shape and performance of the reinforcement and the base alloy, compared with the composite material produced by the casting method, the combination will lead to a decrease in the bonding strength of the composite material interface. In addition, the process method of powder metallurgy determines that it is more suitable for small functional materials, but not for larger structural materials; its process flow is relatively cumbersome, the cost is high, and there are many problems in the transportation process. Therefore, the method of powder metallurgy greatly limits the preparation and production of magnesium-based composite materials as structural materials.

For the selection of reinforcement, attention should be paid to whether there is good wettability between the reinforcement and the matrix, whether the interface bonding strength is appropriate, and whether the interface is chemically reacted. At present, reinforcements are roughly divided into three types: whiskers, fibers, and particles, such as lanthanum oxide particles, cerium oxide particles, silicon carbide whiskers, and carbon fibers. Among them, the cost of fiber reinforced body is high, and it will form a strong texture, which makes the performance of composite material poor. Whiskers and particle-reinforced magnesium-based alloy materials have the advantages of easy processing and dimensional stability. The rare earth oxide particle reinforcement has a high melting point, and will not melt when added to the molten magnesium or magnesium alloy, and will not chemically react with the matrix; if it can be uniformly present in the matrix, the segregation of interstitial impurities at the grain boundary will be reduced , It can increase the strength of the grain boundary; in addition, the rare earth oxide acts as a pin for the dislocation and hinders the movement of the dislocation, so that the strength of the magnesium alloy is improved, and the plasticity will not decrease too much; but directly Rare earth oxides added to the matrix melt will cause the particles to agglomerate due to poor wettability and cannot be well dispersed in the matrix, thus failing to achieve the effect of dispersion strengthening.

The solution to the problem

Technical solutions

The purpose of the present invention is to provide a method for preparing a magnesium-based composite material, by dispersing the reinforcement with a salt flux to improve the surface wettability, and then adding it to the magnesium melt to solve the wettability between the reinforcement and the matrix. The problem is to improve the strength of magnesium-based composite materials while simplifying the process.

The method of the present invention is carried out in the following steps:

(1) Prepare magnesium ingot as a raw material; prepare a salt flux and a reinforcement; the salt flux is a mixture of barium chloride, magnesium chloride, sodium chloride and calcium chloride, wherein barium chloride accounts for 35 ~ of the total mass of the salt flux 50%, magnesium chloride accounts for 10-20% of the total mass of the salt flux, sodium chloride accounts for 10-20% of the total mass of the salt flux, the rest is calcium chloride and impurities, and the impurities account for ≤1% of the total mass of the salt flux; The reinforcement is elemental metal, rare earth oxide, carbide, boride or metal oxide; the elemental metal is W, Mo or Ni, the rare earth oxide is La ₂ O ₃ , CeO ₂ or Y ₂ O ₃ , and the carbide is TiC or SiC, the boride is ZrB ₂ , the metal oxide is MgO or SiO ₂ ; the reinforcement is 0.1-30% of the total volume of the raw material; the reinforcement is 1-50% of the total volume of the salt flux;

(2) Put the salt flux in a clay crucible or graphite crucible and heat it to 773～923K to make a salt flux melt; add the reinforcement into the salt flux melt, stir to make the reinforcement uniformly dispersed, and make a liquid-solid mixture ；

(3) Pour the liquid-solid mixture into a clay crucible or graphite crucible at room temperature, and cool to room temperature to obtain a precursor;

(4) Preheat the iron crucible to a red hot state where the crucible body is dark red, and then place the raw materials in the iron crucible. The raw materials are melted at 953～1043K to form a raw material melt;

(5) Put the precursor into the raw material melt at a temperature of 953～1043K, stir to disperse the precursor uniformly, and then add a refining agent at a temperature of 953～993K and stir for refining. After refining, the temperature is controlled at 1013～ 1023K, stand still to separate impurity components and composite material components, forming scum and composite material melt;

(6) Remove the scum on the surface of the composite material melt, then lower the temperature of the composite material melt to 973-982K, and cast it into a magnesium-based composite material.

The purity of the above-mentioned magnesium ingot is ≥99.85%.

The shape of the above-mentioned reinforcement is fiber, particle or whisker; the particle diameter is 300nm-20μm; the diameter of the whisker is 0.1-1μm and the length is 10-100μm; the diameter of the fiber is 5-20μm and the continuous length is 10-70mm.

In the above step (5), the precursor is first crushed to a particle size ≤ 5 cm, and then put into the raw material melt.

In the above step (2), the stirring speed is 100-200 r/min, and the time is 2-10 min.

In the above step (5), the stirring speed is 100-300 r/min, and the time is 5-15 min.

In the above step (2), when the reinforcement is added to the salt flux melt, all the reinforcements are added in 3 to 5 times, and the addition amount each time is less than 50% of the total mass of the reinforcement.

In the above step (5), before refining, the material in the iron crucible is degassed with a mixed gas. The mixed gas is made by mixing sulfur hexafluoride, carbon dioxide and air, and contains hexafluoride by volume percentage. Sulfur is 0.2-0.3%, carbon dioxide is 25-50%, and the rest is air.

In the above step (5), the standing time is 10-30 minutes.

In the above step (1), the magnesium ingot and other metal components are prepared as raw materials; when step (4) is performed, the magnesium ingot and other metal components are placed in an iron crucible, melted and mixed uniformly to form a raw material melt The other metal components are one or more of aluminum ingot, zinc ingot, manganese chloride, magnesium rare earth alloy, magnesium zirconium alloy and magnesium silicon alloy, and aluminum, zinc, manganese, rare earth, Zirconium and silicon account for ≤10% of the total mass of raw materials.

In the above step (4), a covering agent is sprinkled on the surface of the raw material melt to prevent magnesium from burning; the covering agent is the No. 2 flux; when the step (5) is performed, the covering agent is mixed with the scum; When step (6) is performed, the covering agent is removed together with the scum.

In the above step (5), the refining agent is No. 2 flux.

In the above-mentioned magnesium-based composite material, the raw material component accounts for 80-99.9% of the total volume, and the reinforcement component accounts for 0.1-24% of the total volume.

The beneficial effects of the invention

Beneficial effect

The present invention is characterized in that: the reinforcement is put into the molten salt flux, the reinforcement is uniformly dispersed in the molten salt through mechanical stirring, and the good wetting properties of the reinforcement and the molten salt are used to improve the surface wettability; Due to the large difference between the density of barium chloride in the selected molten salt and the density of magnesium melt, after being added to the magnesium melt, the reinforcement is separated from the molten salt; and after surface modification, it wets well with the magnesium melt , It can be evenly dispersed in the magnesium melt; the salt flux used can effectively refine the melt, remove impurities and cover the melt to prevent magnesium from over-burning. Salts such as barium chloride can improve the wettability of the reinforcement and make it easy to uniformly disperse the reinforcement in the matrix; the method of the present invention has simple process and low cost, and can greatly improve the strength of magnesium-based composite materials; and can be used to prepare large volumes Magnesium-based composite structural parts can be produced automatically, which is of great significance to the development of the magnesium industry.

Brief description of the drawings

Description of the drawings

Figure 1 is an SEM image of the lanthanum oxide reinforced magnesium-based composite material in Example 1 of the present invention; in the figure, (b) is a partial enlarged view of (a);

2 is the XRD pattern of the lanthanum oxide reinforced magnesium-based composite material in Example 1 of the present invention; (a) is the La ₂ O ₃ standard peak, (b) is the magnesium-based composite material;

Fig. 3 is an SEM image of the ceria-reinforced magnesium-based composite material in Example 2 of the present invention; in the figure, (b) is a partial enlarged view of (a).

Invention embodiment

Embodiments of the present invention

The invention will be described in detail below in conjunction with embodiments.

In the embodiment of the present invention, a thermocouple is used to detect temperature to ensure the accuracy of temperature measurement.

The purity of the aluminum ingot and zinc ingot of the present invention is 98.9-99.9%.

The manganese chloride of the present invention is of industrial grade purity.

The magnesium rare earth alloy, magnesium zirconium alloy and magnesium silicon alloy of the present invention are collectively referred to as master alloys, and the rare earth, zirconium and silicon in the master alloy respectively account for 10-40% of the total mass of the master alloy.

The magnesium ingot, reinforcement and No. 2 flux used in the embodiment of the present invention are commercially available products.

The barium chloride, magnesium chloride, sodium chloride and calcium chloride used in the embodiments of the present invention are commercially available industrial grade products.

The electron microscope used in the embodiment of the present invention is Shimadzu SSX550.

The X-ray diffraction observation equipment used in the embodiment of the present invention is the Dutch PANalytical Xpertpro.

In the embodiment of the present invention, the magnesium-based composite material uses X-ray fluorescence spectroscopy to calculate the reinforcement mass percentage, and then converts it into volume percentage.

The purity of the magnesium ingot in the embodiment of the present invention is ≥99.85%.

The shape of the reinforcement in the embodiment of the present invention is fiber, particle or whisker; wherein the particle diameter is 300nm-20μm; the whisker diameter is 0.1-1μm and the length is 10-100μm; the fiber diameter is 5-20μm and the continuous length is 10 ~70mm.

In the embodiment of the present invention, before refining, a mixed gas is used to degas the materials in the iron crucible. The mixed gas is made from a mixture of sulfur hexafluoride, carbon dioxide and air, and contains 0.2 to 0.2% of sulfur hexafluoride by volume. 0.3%, 25-50% carbon dioxide, the rest is air; the time for the mixed gas to pass is 2-5min.

The adding amount of the refining agent in the embodiment of the present invention is 0.5-0.8% of the total mass of all the melt in the iron crucible.

Example 1

Prepare magnesium ingot as a raw material; prepare salt flux and reinforcement; the salt flux is a mixture of barium chloride, magnesium chloride, sodium chloride and calcium chloride, in which barium chloride accounts for 45% of the total mass of the salt flux, and magnesium chloride accounts for 20% of the total mass of the salt flux, sodium chloride accounts for 15% of the total mass of the salt flux, the rest is calcium chloride and impurities, and the impurities account for less than 1% of the total mass of the salt flux; the reinforcement is a rare earth oxide that is La ₂ O ₃ particles; the reinforcement is 0.5% of the total volume of the raw material; the reinforcement is 3% of the total volume of the salt flux;

Put the salt flux in a clay crucible and heat it to 803K to make a salt flux melt; add the reinforcement into the salt flux melt, stir to make the reinforcement uniformly dispersed, and make a liquid-solid mixture; stirring speed 100r/min, time 10min; when the reinforcement is added to the salt flux melt, all the reinforcements are added in 3 times, and the amount of each addition is less than 50% of the total mass of the reinforcement;

Pour the liquid-solid mixture into a clay crucible at room temperature, and cool to room temperature to obtain a precursor;

Preheat the iron crucible to the red hot state of the crucible body, and then place the raw materials in the iron crucible. The raw materials are melted at 973K to form a raw material melt; a covering agent is sprinkled on the surface of the raw material melt to prevent magnesium from burning; The covering agent is No. 2 flux;

First crush the precursor to a particle size ≤ 5cm, then put it into the raw material melt at a temperature of 973K, stir to disperse the precursor uniformly, and then add a refining agent at a temperature of 973K and stir for refining. The refining agent is No. 2 flux. The stirring speed is 100r/min, the time is 15min, the temperature is raised to 1013K after the refining is finished, and the impurity components and the composite material components are separated by standing to form scum and composite material melt; standing time is 30min;

Remove the scum on the surface of the composite material melt, then lower the temperature of the composite material melt to 973K, and cast it into a magnesium-based composite material; the reinforcement component of the magnesium-based composite material accounts for 0.41% of the total volume, and the rest are raw material components;

The SEM image of the magnesium-based composite material (lanthanum oxide reinforced magnesium-based composite material) is shown in Figure 1, and the XRD image is shown in Figure 2. It can be seen from the figure that the La ₂ O ₃ phase is evenly distributed in the matrix;

Under the same conditions, adjust the amount of reinforcement for parallel testing. The reinforcements are respectively 1%, 3%, 5%, 7%, 9%, 15% and 20% of the total volume of the raw materials. The final formation of lanthanum oxide reinforced magnesium In the matrix composite material, 80-90% of the total mass of the reinforcement is retained in the matrix.

Example 2

The method is the same as in Example 1, the difference is:

(1) In the salt flux, barium chloride accounts for 50% of the total mass of the salt flux, magnesium chloride accounts for 10% of the total mass of the salt flux, and sodium chloride accounts for 20% of the total mass of the salt flux;

(2) The reinforcement is CeO ₂ particles of rare earth oxide;

(3) The reinforcement is 1% of the total volume of the raw material; the reinforcement is 5% of the total volume of the salt flux;

(4) Put the salt flux in the graphite crucible and heat it to 773K to make the salt flux melt; the stirring speed is 200r/min, the time is 2min; when the reinforcement is added to the salt flux melt, all the reinforcements are divided into 4 times Join

(5) Pour the liquid-solid mixture into a graphite crucible at room temperature;

(6) The raw material in the iron crucible is melted at 953K to form a raw material melt;

(7) After the precursor is broken, put it into the raw material melt at a temperature of 953K; add a refining agent at a temperature of 953K and stir for refining at a stirring speed of 300r/min for 5min. After the refining is completed, the temperature is raised to 1023K; standing time is 10min;

(8) The temperature of the composite material melt is reduced to 982K for casting; the reinforcement component of the magnesium-based composite material accounts for 0.85% of the total volume, and the rest is the raw material component;

The SEM image of the magnesium-based composite material (ceria-reinforced magnesium-based composite material) is shown in Figure 3. The CeO ₂ phase is uniformly distributed in the matrix.

Example 3

The method is the same as in Example 1, the difference is:

(1) Prepare magnesium ingots and other metal components as raw materials; the other metal components are aluminum ingots, which account for 5% of the total mass of the raw materials; the barium chloride in the salt flux accounts for 35% of the total mass of the salt flux, and magnesium chloride accounts for the total mass of the salt flux. 15% of the mass, sodium chloride accounts for 10% of the total mass of the salt flux;

(2) The reinforcement is ZrB ₂ boride;

(3) The reinforcement is 10% of the total volume of the raw material; the reinforcement is 15% of the total volume of the salt flux;

(4) Put the salt flux in the graphite crucible and heat it to 883K to make the salt flux melt; stirring speed 150r/min, time 5min; when the reinforcement is added to the salt flux melt, all the reinforcements are divided into 5 times Join

(5) Pour the liquid-solid mixture into a graphite crucible at room temperature;

(6) Put the magnesium ingot and other metal components together in an iron crucible, and the raw materials in the iron crucible are melted at 1043K to form a raw material melt;

(7) After the precursor is broken, put it into the raw material melt at a temperature of 1043K; add a refining agent at a temperature of 1043K and stir for refining at a stirring speed of 200r/min for 10min. After refining, the temperature is reduced to 1013K; standing time is 20min;

(8) The temperature of the composite material melt is lowered to 978K for casting; the reinforcement component of the magnesium-based composite material accounts for 8.1% of the total volume, and the rest are raw material components.

Example 4

The method is the same as in Example 1, the difference is:

(1) Prepare magnesium ingots and other metal components as raw materials; the other metal components are zinc ingots, accounting for 2% of the total mass of raw materials;

(2) The reinforcement is elemental metal W;

(3) The reinforcement is 15% of the total volume of the raw material; the reinforcement is 25% of the total volume of the salt flux;

(4) Put the salt flux in a graphite crucible and heat it to 923K to make the salt flux melt; stirring speed 120r/min, time 8min;

(5) Pour the liquid-solid mixture into a graphite crucible at room temperature;

(7) After the precursor is broken, put it into the raw material melt at a temperature of 1043K; add a refining agent at a temperature of 1043K and stir for refining. After the refining is completed, the temperature is reduced to 1018K; the standing time is 15min;

(8) The temperature of the composite material melt is lowered to 980K for casting; the reinforcement component of the magnesium-based composite material accounts for 13.3% of the total volume, and the rest is the raw material component.

Example 5

The method is the same as in Example 1, the difference is:

(1) Prepare magnesium ingots and other metal components as raw materials; the other metal components are magnesium rare earth alloys, and rare earths account for 4% of the total mass of the raw materials; in the salt flux, barium chloride accounts for 40% of the total mass of the salt flux, and magnesium chloride accounts for the salt 20% of the total mass of the flux, sodium chloride accounts for 20% of the total mass of the salt flux;

(2) The reinforcement is TiC carbide;

(3) The reinforcement is 22% of the total volume of the raw materials; the reinforcement is 40% of the total volume of the salt flux;

(4) Put the salt flux in the graphite crucible and heat it to 828K to make the salt flux melt; the stirring speed is 180r/min, the time is 3min; when the reinforcement is added to the salt flux melt, all the reinforcements are divided into 4 times Join

(5) Pour the liquid-solid mixture into a graphite crucible at room temperature;

(6) Put the magnesium ingot and other metal components together in an iron crucible, and the raw materials in the iron crucible are melted at 988K to form a raw material melt;

(7) After the precursor is broken, put it into the raw material melt at a temperature of 988K; add a refining agent at a temperature of 988K and stir for refining, at a stirring speed of 300r/min, for 5min, and heat up to 1023K after refining; standing time 25min;

(8) The temperature of the composite material melt is lowered to 979K for casting; the reinforcement component of the magnesium-based composite material accounts for 18.6% of the total volume, and the rest is the raw material component.

Example 6

The method is the same as in Example 1, the difference is:

(1) Prepare magnesium ingots and other metal components as raw materials; the other metal components are magnesium-zirconium alloys and magnesium-silicon alloys of equal mass, zirconium and silicon account for 10% of the total mass of the raw materials; in the salt flux, barium chloride accounts for the salt flux 50% of the total mass, magnesium chloride accounts for 10% of the total mass of the salt flux, and sodium chloride accounts for 10% of the total mass of the salt flux;

(2) The reinforcement is a metal oxide SiO ₂ ;

(3) The reinforcement is 26% of the total volume of the raw material; the reinforcement is 45% of the total volume of the salt flux;

(4) Heat to 873K to make a salt flux melt; stirring speed 160r/min, time 4min; when the reinforcement is added to the salt flux melt, all the reinforcements are added in 5 times;

(5) Put the magnesium ingot and other metal components together in an iron crucible, and the raw materials in the iron crucible are melted at 993K to form a raw material melt;

(6) After the precursor is broken, put it into the raw material melt at a temperature of 993K; add a refining agent at a temperature of 993K and stir for refining, at a stirring speed of 200r/min, for 10min, and heat up to 1013K after refining; standing time 25min;

(7) The temperature of the composite material melt is lowered to 976K for casting; the reinforcement component of the magnesium-based composite material accounts for 21.1% of the total volume, and the rest is the raw material component.

Claims

A preparation method of magnesium-based composite material is characterized in that it is carried out according to the following steps:

(1) Prepare magnesium ingot as a raw material; prepare a salt flux and a reinforcement; the salt flux is a mixture of barium chloride, magnesium chloride, sodium chloride and calcium chloride, wherein barium chloride accounts for 35 ~ of the total mass of the salt flux 50%, magnesium chloride accounts for 10-20% of the total mass of the salt flux, sodium chloride accounts for 10-20% of the total mass of the salt flux, the rest is calcium chloride and impurities, and the impurities account for ≤1% of the total mass of the salt flux; The reinforcement is elemental metal, rare earth oxide, carbide, boride or metal oxide; the elemental metal is W, Mo or Ni, the rare earth oxide is La 2 O 3 , CeO 2 or Y 2 O 3 , and the carbide is TiC or SiC, the boride is ZrB 2 , the metal oxide is MgO or SiO 2 ; the reinforcement is 0.1-30% of the total volume of the raw material; the reinforcement is 1-50% of the total volume of the salt flux;

(2) Put the salt flux in a clay crucible or graphite crucible and heat it to 773～923K to make a salt flux melt; add the reinforcement into the salt flux melt, stir to make the reinforcement uniformly dispersed, and make a liquid-solid mixture ；

(3) Pour the liquid-solid mixture into a clay crucible or graphite crucible at room temperature, and cool to room temperature to obtain a precursor;

(4) Preheat the iron crucible to a red hot state where the crucible body is dark red, and then place the raw materials in the iron crucible. The raw materials are melted at 953～1043K to form a raw material melt;

(5) Put the precursor into the raw material melt at a temperature of 953～1043K, stir to disperse the precursor uniformly, and then add a refining agent at a temperature of 953～993K and stir and refine. After the refining is completed, the temperature is controlled at 1013～ 1023K, stand still to separate the impurity components and composite material components to form scum and composite material melt;

(6) Remove the scum on the surface of the composite material melt, then lower the temperature of the composite material melt to 973-982K, and cast it into a magnesium-based composite material.
The method for preparing a magnesium-based composite material according to claim 1, wherein the purity of the magnesium ingot is ≥99.85%.
The method for preparing a magnesium-based composite material according to claim 1, wherein the shape of the reinforcement is fiber, particle or whisker; wherein the particle size is 300nm-20μm; the whisker diameter is 0.1- 1μm, length 10-100μm; fiber diameter 5-20μm, continuous length 10-70mm.
The method for preparing a magnesium-based composite material according to claim 1, wherein in step (2), the stirring speed is 100-200 r/min and the time is 2-10 min.
The method for preparing a magnesium-based composite material according to claim 1, wherein in step (5), the stirring speed is 100-300 r/min and the time is 5-15 min.
The method for preparing a magnesium-based composite material according to claim 1, wherein in step (5), the standing time is 10-30 minutes.
The method for preparing a magnesium-based composite material according to claim 1, wherein in step (1), magnesium ingots and other metal components are prepared as raw materials; when step (4) is performed, magnesium ingots and other metal The components are placed together in an iron crucible, melted and mixed evenly to form a raw material melt; the other metal components are one of aluminum ingot, zinc ingot, manganese chloride, magnesium rare earth alloy, magnesium zirconium alloy and magnesium silicon alloy One or more kinds, and the aluminum, zinc, manganese, rare earth, zirconium and silicon in other metal components account for less than 10% of the total mass of the raw materials.
The method for preparing a magnesium-based composite material according to claim 1, wherein in step (4), a covering agent is sprinkled on the surface of the raw material melt to prevent magnesium from burning; the covering agent is No. 2 Flux; when step (5) is performed, the covering agent is mixed with scum; when step (6) is performed, the covering agent and scum are removed together.
The method for preparing a magnesium-based composite material according to claim 1, wherein in step (5), the refining agent is No. 2 flux.
The method for preparing a magnesium-based composite material according to claim 1, characterized in that the raw material components in the magnesium-based composite material account for 80-99.9% of the total volume, and the reinforcement component accounts for 0.1-24% of the total volume. .