Method for producing metal particle reinforced magnesium matrix composites by semi-solid injection molding

Abstract

The application belongs to the field of metal matrix composite material preparation, and specifically discloses a method for preparing a metal particle reinforced magnesium matrix composite material by semi-solid injection molding, which comprises the following steps: mixing and grinding magnesium alloy particles with metal particles to obtain mixed particles; heating the mixed particles to semi-solid state in the process of shear mixing to obtain a semi-solid slurry; injecting the semi-solid slurry into a mold, and then applying pressure to make the semi-solid slurry solidify and form the metal particle reinforced magnesium matrix composite material. The preparation method in the application can make the mixed particles uniformly distributed by heating the mixed particles to semi-solid slurry under the action of shear mixing, solve the common macrosegregation and local agglomeration defects of the composite material, and make the shape of the solid particles in the semi-solid slurry tend to be spherical, thereby improving the flexibility and mechanical properties of the prepared composite material at room temperature and high temperature.

Description

Technical Field

[0001] This invention belongs to the field of metal matrix composite material preparation, specifically relating to a method for preparing metal particle reinforced magnesium matrix composite material by semi-solid injection molding. Background Technology

[0002] Magnesium alloys possess a range of advantages, including low density, high specific strength, and easy recyclability, making them important lightweight structural materials. However, their low strength and toughness at both room temperature and high temperatures severely limit their application as high-stability structural components. With the rapid development of industries such as new energy vehicles, drones, and 3C products, there is an urgent need to develop magnesium-based composite materials with high strength, high toughness, and relatively high-temperature strength to achieve lightweight and reliable equipment. Metal particle-reinforced magnesium-based composites combine the low density of magnesium alloys with the high strength, high toughness, and high-temperature strength of metal particles, demonstrating significant application potential and attracting widespread attention. However, composites prepared by conventional stir casting suffer from uneven particle distribution, numerous porosity and looseness defects, resulting in poor mechanical properties at both room temperature and high temperatures. In particular, the preparation of high-fraction metal particle-reinforced magnesium-based composites faces challenges due to the high melt viscosity and difficulty in feeding during solidification, leading to a sharp decline in the material's mechanical properties.

[0003] Existing technology discloses a semi-solid molding method for magnesium-based composite materials. This method involves mixing magnesium alloy powder with ceramic reinforcing phase powder, cold-pressing the mixture into a composite material billet, heating the billet to 300-650°C, and then injecting the solid-liquid mixture into a mold to obtain the composite material. However, this method does not stir the solid-liquid mixture before injection, resulting in numerous angular precipitates of the primary solid phase in the alloy, making it difficult to form spherical shapes. Furthermore, due to the density difference between the reinforcing material and the magnesium alloy melt, sedimentation occurs, easily leading to the formation of macroscopic reinforcing particles in the prepared composite material. Additionally, the solidus temperature of AZ91 alloy is 468°C, and its liquidus temperature is 598°C. Injection molding cannot be performed in the 300-470°C range, while it is liquid at 650°C, which is suitable for liquid injection molding. At this temperature, without stirring and holding for 15 minutes, TiC particles will significantly settle, resulting in an uneven distribution of the reinforcing phase in the final composite material. In addition, the magnesium alloy used in this scheme is micron-sized and belongs to magnesium powder, which is extremely explosive and can only be used for powder metallurgy, not for injection molding. Summary of the Invention

[0004] In order to overcome at least one of the technical problems existing in the prior art, one of the objectives of the present invention is to provide a method for preparing a magnesium-based composite material reinforced with metal particles, wherein the magnesium-based composite material reinforced with metal particles prepared by the method has excellent mechanical properties at both room temperature and high temperature.

[0005] The second objective of this invention is to provide the application of the above-mentioned method for preparing magnesium-based composite materials reinforced with metal particles in the fields of new energy vehicles, drones, or 3C products.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of the present invention provides a method for preparing a magnesium-based composite material reinforced with metal particles, comprising the following steps:

[0008] Magnesium alloy particles are mixed and ground with metal particles to obtain mixed particles;

[0009] The mixed particles are heated to a semi-solid state during the shearing and mixing process to obtain a semi-solid slurry;

[0010] The semi-solid slurry is injected into a mold, and then a holding pressure is applied to solidify the semi-solid slurry to obtain the metal particle reinforced magnesium matrix composite material.

[0011] This invention involves mixing and grinding magnesium alloy particles with metal particles to ensure that the metal particles are evenly distributed on the surface of the magnesium alloy particles. The mixed particles are then heated to form a semi-solid slurry. During the heating process, shearing and mixing are performed to further disperse the metal particles. The semi-solid slurry is then injected into molds and solidified under holding pressure, thereby achieving a shrinkage compensation effect during the solidification process of the semi-solid slurry.

[0012] In some embodiments of the present invention, the mass ratio of the metal particles to the metal particle-reinforced magnesium matrix composite material is (2.5-45):100; in some embodiments of the present invention, the mass ratio of the metal particles to the metal particle-reinforced magnesium matrix composite material is 2.5:100, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, 9:100, 10:100, 11:100, 12:100, 13:100, 14:100, 15:100, 16:1 The range of values ​​formed by any one of the following: 00, 17:100, 18:100, 19:100, 20:100, 21:100, 22:100, 23:100, 24:100, 25:100, 26:100, 27:100, 28:100, 29:100, 30:100, 31:100, 32:100, 33:100, 34:100, 35:100, 36:100, 37:100, 38:100, 39:100, 40:100, or any combination thereof. When the mass ratio of metal particles to composite material is (2.5-30):100, the solid fraction (the weight percentage of non-dendritic primary α-Mg precipitated in the magnesium alloy slurry) in the semi-solid slurry is controlled at 30-51% by adjusting the injection temperature; when the mass ratio of metal particles to composite material is (30-45):100, the solid fraction in the semi-solid slurry is controlled at 20-30% by adjusting the injection temperature. The semi-solid slurry in this invention contains liquid magnesium alloy, solid primary α-Mg, and solid metal particles. The solid fraction refers to the proportion of solid primary α-Mg in the magnesium alloy, excluding solid metal particles. The purpose of adjusting the solid fraction in this invention is to control the total solid fraction (i.e., (primary α-Mg + solid metal particles) / semi-solid slurry) from being too high. An excessively high solid fraction results in a very high viscosity of the semi-solid slurry, making injection molding impossible. To ensure that the semi-solid slurry can be injection molded, the total solid content needs to be controlled within the range of 35-75%, and ideally, it needs to be controlled at around 50%. Therefore, when the amount of metal particles is increased, the solid content needs to be reduced, and when the amount of metal particles is reduced, the solid content needs to be increased, so that the solid content in the semi-solid slurry is maintained at around 50%.

[0013] In some embodiments of the present invention, the solid fraction of the semi-solid slurry is 20-51%.

[0014] In some embodiments of the present invention, the magnesium alloy particles include at least one of Mg-Al-Zn alloy and Mg-Al-Mn alloy.

[0015] In some embodiments of the present invention, the metal particles are selected from at least one of Ti, Mn, and TC4. The metal particles do not react with the magnesium alloy particles and have low solubility in the magnesium alloy melt.

[0016] In some embodiments of the present invention, the magnesium alloy particles are obtained by cutting magnesium alloy ingots into metal particles.

[0017] In some embodiments of the present invention, the magnesium alloy particles are rectangular, spherical, or irregular in shape.

[0018] In some embodiments of the present invention, the particle size of the magnesium alloy particles is 0.2-2.5 mm; in some embodiments of the present invention, the particle size of the magnesium alloy particles is any value or a range formed by any two of the following: 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm, 2.0 mm, 2.2 mm, 2.4 mm, and 2.5 mm. If the particle size of the magnesium alloy particles is less than 0.2 mm, the cutting and granulation process of cutting the magnesium alloy ingot into particles is difficult and inefficient. If the particle size of the magnesium alloy particles is greater than 2.5 mm, the size difference with the metal particles is too large, making it difficult for the metal particles to be evenly distributed on the surface of the magnesium alloy particles during grinding and mixing.

[0019] In some embodiments of the present invention, the particle size of the metal particles is 0.1 μm-20 μm; in some embodiments of the present invention, the particle size of the metal particles is any value or a range formed by any two of the following: 0.1 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm.

[0020] In this invention, the particle size of the magnesium alloy particles is 0.2-2.5 mm, and the particle size of the metal particles is 0.1 μm-20 μm. During the mixing and grinding process of the magnesium alloy particles and the metal particles, the metal particles gather on the surface of the magnesium alloy and are evenly distributed on the surface of the magnesium alloy, which is beneficial to improving the dispersion uniformity of the metal particles in the composite material.

[0021] In some embodiments of the present invention, the metal particles are spherical or irregular in shape.

[0022] In some embodiments of the present invention, the rotational speed of the mixing and grinding is 100-200 r / min; in some embodiments of the present invention, the rotational speed of the mixing and grinding is any value or a range formed by any two of 100 r / min, 110 r / min, 120 r / min, 130 r / min, 140 r / min, 150 r / min, 160 r / min, 170 r / min, 180 r / min, 190 r / min, and 200 r / min.

[0023] In some embodiments of the present invention, the mixing and grinding time is 1-10 hours; in some embodiments of the present invention, the mixing and grinding time is 2-3 hours. If the grinding time is too short, the metal particles cannot adhere to the magnesium alloy particles and disperse on the surface of the magnesium alloy particles. If the grinding time is too long, even under vacuum or inert gas protection, oxidation will occur, reducing the performance and strength of the obtained magnesium-based composite material.

[0024] In some embodiments of the present invention, the atmosphere for the mixing and grinding is a vacuum or an inert gas.

[0025] In some embodiments of the present invention, the inert gas is selected from at least one of nitrogen, argon, and helium.

[0026] In some embodiments of the present invention, the liquidus temperature of the magnesium alloy particles is T. 液相 ℃, the temperature of the semi-solid slurry is T℃, then (T 液相 -20)≤T≤T 液相 If the temperature of the semi-solid slurry is lower than (T) 液相 At -20℃, the semi-solid slurry begins to solidify before being injected into the mold cavity, making injection molding impossible; if the temperature of the semi-solid slurry is higher than T... 液相 If the temperature is below a certain level, a semi-solid slurry cannot be formed, resulting in poor mechanical properties of the magnesium-based composite material obtained after injection molding.

[0027] In some embodiments of the present invention, the rotational speed of the shear mixing is 200-300 r / min; in other embodiments, the rotational speed of the shear mixing is any value or a range formed by any two of the following: 200 r / min, 210 r / min, 220 r / min, 230 r / min, 240 r / min, 250 r / min, 260 r / min, 270 r / min, 280 r / min, 290 r / min, and 300 r / min. When the rotational speed of the shear mixing is below 200 r / min, the shear mixing effect is weakened, the transport speed is slow, and the preparation efficiency is low. When the rotational speed of the shear mixing is above 300 r / min, the requirements for the rigidity of the screw and the equipment motor are too high, which is difficult to achieve with current equipment.

[0028] In some embodiments of the present invention, the shear mixing is performed using a screw. When using a screw for shear mixing, on the one hand, the mixing particles are conveyed to the injection position by the screw, and the mixing particles are heated into a semi-solid slurry (metal particles are solid, magnesium alloy particles are melted into a semi-solid state). On the other hand, the rotation of the screw also serves to shear and stir the mixture. Through shearing and stirring, the solid phase distribution in the metal particles and magnesium alloy becomes more uniform, preventing them from settling in the semi-solid or liquid melt; and on the other hand, the dendritic primary α-Mg solid phase in the magnesium alloy transforms from a polygonal, irregular shape into a spherical shape under external force, which is beneficial for improving the flexibility and impact resistance of the composite material.

[0029] In some embodiments of the present invention, the semi-solid slurry is prepared by a method comprising the following steps:

[0030] The mixed granules are added to the hopper of the injection molding equipment, and then conveyed to the barrel at a temperature of T℃ by the feed screw in the hopper. The screw in the barrel rotates at a rate of 200-300 r / min to feed the granules, and the mixed granules are heated into a semi-solid slurry in the barrel.

[0031] In some embodiments of the present invention, the temperature of the barrel is T℃, the temperature of the barrel is the same as that of the semi-solid slurry, and the mixed particles are heated in the barrel at a set temperature of T℃ to become a semi-solid slurry.

[0032] In some embodiments of the present invention, the temperature of the mold is 200-300°C; in other embodiments, the temperature of the mold is any value or a range formed by any two of 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, and 300°C. A mold temperature below 200°C is not conducive to the filling of the semi-solid slurry, and defects such as incomplete filling of the semi-solid slurry within the mold are easily observed. A mold temperature above 300°C results in a slow cooling rate of the semi-solid slurry, which facilitates the growth of the second phase and affects the mechanical properties of the resulting composite material.

[0033] In some embodiments of the present invention, the injection speed is 3-5 m / s; in other embodiments, the injection speed is any value or a range formed by any two of the following: 3 m / s, 3.1 m / s, 3.2 m / s, 3.3 m / s, 3.4 m / s, 3.5 m / s, 3.6 m / s, 3.7 m / s, 3.8 m / s, 3.9 m / s, 4 m / s, 4.1 m / s, 4.2 m / s, 4.3 m / s, 4.4 m / s, 4.5 m / s, 4.6 m / s, 4.7 m / s, 4.8 m / s, 4.9 m / s, and 5 m / s. When the injection speed is below 3 m / s, it is not conducive to the filling of the semi-solid slurry, and defects such as incomplete filling of the semi-solid slurry in the mold are easily encountered. When the injection speed is above 5 m / s, air entrapment is easily formed during the filling of the semi-solid slurry, and pores are easily formed in the resulting composite material.

[0034] In some embodiments of the present invention, the holding pressure is 200-350 MPa; in other embodiments, the holding pressure is any value or a range formed by any two of the following: 200 MPa, 210 MPa, 220 MPa, 230 MPa, 240 MPa, 250 MPa, 260 MPa, 270 MPa, 280 MPa, 290 MPa, 300 MPa, 310 MPa, 320 MPa, 330 MPa, 340 MPa, and 350 MPa. When the holding pressure is less than 200 MPa, microscopic porosity defects are prone to appear in the resulting composite material. If the holding pressure is greater than 350 MPa, the tendency for pinhole defects to form inside the resulting composite material increases. The injection molding process of the present invention is stable, and pressure compensation exists during solidification, resulting in fewer pore defects and higher density in the composite material, which can undergo T6 heat treatment. The present invention applies a holding pressure after the semi-solid slurry is injected into the mold cavity and before it solidifies, which is beneficial for compensating for shrinkage of the semi-solid slurry. If the holding pressure is applied after the semi-solid slurry has solidified, it will not have the effect of compensating for shrinkage.

[0035] In some embodiments of the present invention, the composite material has a tensile strength of 308–386 MPa at 25°C.

[0036] In some embodiments of the present invention, the composite material has a yield strength of 208–245 MPa at 25°C.

[0037] In some embodiments of the present invention, the composite material has an elongation at break of 8.5 to 12.5% ​​at 25°C.

[0038] In some embodiments of the present invention, the composite material has a tensile strength of 152–196 MPa at 100°C.

[0039] In some embodiments of the present invention, the composite material has a yield strength of 98–125 MPa at 100°C.

[0040] In some embodiments of the present invention, the composite material has an elongation at break of 25-38% at 100°C.

[0041] In some embodiments of the present invention, the method for preparing the metal particle-reinforced magnesium-based composite material includes the following steps:

[0042] Magnesium alloy particles and metal particles are mixed and ground under vacuum or inert atmosphere to obtain mixed particles;

[0043] The mixed granules are added to the hopper of the injection molding equipment and then conveyed to the barrel through the feed screw of the hopper. The screw in the barrel rotates at a rate of 200-300 r / min to feed the granules, and the mixed granules are heated into a semi-solid slurry in the barrel.

[0044] The liquidus temperature of the magnesium alloy particles is T. 液相 ℃, the temperature of the semi-solid slurry is T℃, then (T 液相 -20)≤T≤T 液相 ;

[0045] The semi-solid slurry is injected into a mold at a temperature of 200-300℃ at an injection speed of 3-5m / s, and then a holding pressure of 200-350MPa is applied to solidify the semi-solid slurry to obtain the metal particle reinforced magnesium matrix composite material.

[0046] This invention involves adding mixed particles into the hopper of an injection molding machine. A rotating screw in the hopper continuously feeds the mixed particles into a barrel heated to a set temperature T. The rotating screw in the barrel pushes the mixed particles towards the cavity in front of the punch (i.e., the injection position). The mixed particles move and mix under the shearing force of the rotating screw in the barrel, and during this movement, they are heated to a semi-solid state, becoming a semi-solid slurry (the reinforcing particles are solid, and the magnesium alloy melts into a semi-solid state). Besides pushing the mixed particles or slurry, the rotating screw in the barrel also acts as a shearing and stirring mechanism. This shearing and stirring makes the solid phase distribution in the metal particles and magnesium alloy matrix more uniform, preventing sedimentation in the semi-solid or liquid melt. Simultaneously, under external force, the solid phase in the magnesium alloy matrix transforms from a polygonal, irregular shape into a spherical shape, which is beneficial for improving the toughness of the composite material. If the screw rotation speed in the barrel is too low and the shearing force is too small, the particles are prone to agglomeration. In the semi-solid slurry, about 50% is liquid magnesium alloy. The density of the added metal particles is greater than that of the magnesium alloy melt. Without the shearing force of the screw, the metal particles will naturally settle, resulting in uneven composition distribution.

[0047] The second aspect of the present invention provides the application of the preparation method of the metal particle reinforced magnesium matrix composite material described in the first aspect of the present invention in the fields of new energy vehicles, drones or 3C products.

[0048] The beneficial effects of this invention are as follows: The preparation method of this invention heats the mixed particles to a semi-solid slurry under shear mixing, which can make the mixed particles uniformly distributed, solving the common macroscopic segregation and local agglomeration defects of composite materials. Furthermore, it makes the shape of the solid primary α-Mg in the semi-solid slurry tend to be spherical, improving the flexibility and mechanical properties of the obtained composite material at room temperature and high temperature. Specifically, the tensile strength of the composite material at 25℃ is 308–386 MPa, the yield strength is 208–245 MPa, and the elongation at break is 8.5–12.5%; the tensile strength of the composite material at 100℃ is 152–196 MPa, the yield strength is 98–125 MPa, and the elongation at break is 25–38%. It maintains good flexibility and mechanical properties even at high temperatures, which is beneficial for the long-term use of the composite material in high-temperature environments. Attached Figure Description

[0049] Figure 1 This is a photograph of the AZ91D magnesium alloy matrix particles in Example 1.

[0050] Figure 2 This is a SEM image of the mixed particles in Example 1.

[0051] Figure 3 The image shows a SEM image of the composite material prepared in Example 1. Detailed Implementation

[0052] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0053] Example 1

[0054] This example provides a method for preparing metal particle-reinforced magnesium matrix composites by semi-solid injection molding, specifically including the following steps:

[0055] Step 1: Using a granulator, commercially available AZ91D ingots are processed into irregularly shaped elongated particles to obtain AZ91D magnesium alloy matrix particles (see image below). Figure 1 As shown), the length dimension is 2mm.

[0056] Step 2: Using Ti particles as reinforcement, the average particle size of the titanium particles used was 15 μm. The materials were proportioned according to a Ti particle mass percentage of 12.5% ​​and an AZ91D particle mass percentage of 87.5% in the composite material. The Ti particles and AZ91D particles were then added to a vacuum ball mill for mixing at a speed of 150 r / min for 2.5 h to obtain mixed particles. SEM images of the mixed particles were obtained using scanning electron microscopy (SEM), as shown below. Figure 2 As shown. Figure 2 The white particles are Ti particles, and the dark particles are AZ91D particles, indicating that after ball milling, the Ti particles adhere to and are evenly distributed on the surface of the AZ91D particles.

[0057] Step 3: Add the mixed granules from Step 2 into the hopper of a semi-solid injection molding machine with a clamping force of 350 tons. Start the motor of the hopper feed screw to feed the mixed granules into the preheated barrel. The screw in the barrel rotates at 250 r / min. Adjust the power of the electric heating element on the outside of the barrel so that the temperature of the mixed granules reaches 585℃ (the liquidus of AZ91D magnesium alloy is 595℃) when it enters the cavity in front of the punch, thus obtaining a semi-solid slurry.

[0058] Step 4: When the volume of semi-solid slurry in the cavity in front of the punch reaches the set amount, the injection system of the semi-solid injection molding machine pushes the punch to inject the semi-solid slurry through the nozzle. The mold temperature is 250℃, the injection speed is 3m / s, and after the slurry fills the mold cavity, a pressure of 300MPa is applied to hold the pressure.

[0059] Step 5: After the semi-solid slurry solidifies and forms in the mold, open the mold, remove the composite material casting, and obtain the metal particle reinforced magnesium matrix composite material in this example.

[0060] The SEM images of the composite material prepared in this example were obtained using scanning electron microscopy, as shown below. Figure 3 As shown. By Figure 3 It can be seen that titanium particles in composite materials ( Figure 3 The medium-white particles are macroscopically uniformly distributed and do not exhibit macroscopic segregation, microscopic agglomeration, or defects such as pores.

[0061] Example 2

[0062] This example provides a method for preparing metal particle-reinforced magnesium matrix composites by semi-solid injection molding, specifically including the following steps:

[0063] Step 1: Using a granulator, process commercially available AM60B ingots into irregularly shaped long strips of granules with a length dimension of 1mm.

[0064] Step 2: Using Ti particles as reinforcement, the average particle size of the titanium particles used is 10μm. The materials are prepared according to the following formula: the mass percentage of titanium particles in the composite material is 20% and the mass percentage of AM60B particles in the composite material is 80%. The Ti particles and AM60B particles are added to a vacuum ball mill for mixing. The ball mill speed is 300r / min and the mixing time is 3h to obtain mixed particles.

[0065] Step 3: Add the mixed granules from Step 2 to the hopper of the semi-solid injection molding machine, start the motor, and the mixed granules enter the barrel. The screw in the barrel rotates at 250 r / min. Adjust the power of the electric heating element on the outside of the barrel so that the temperature of the mixed granules reaches 610℃ (the liquidus of AM60B magnesium alloy is 615℃) when it enters the cavity in front of the punch, to obtain a semi-solid slurry;

[0066] Step 4: When the volume of semi-solid slurry in the cavity in front of the punch reaches the set amount, the injection system pushes the punch to inject the semi-solid slurry through the nozzle at an injection speed of 4 m / s. After the semi-solid slurry fills the mold cavity, a pressure of 320 MPa is applied and held.

[0067] Step 5: After the semi-solid slurry solidifies and forms in the mold, open the mold, remove the composite material casting, and obtain the metal particle reinforced magnesium matrix composite material in this example.

[0068] Example 3

[0069] The method for preparing metal particle-reinforced magnesium matrix composites in this example differs from that in Example 1 only in that:

[0070] (1) In step 2, the mass percentage of Ti particles in the composite material is 2.5%, and the mass percentage of AZ91D particles in the composite material is 97.5%.

[0071] (2) In step 3, the temperature of the mixed particles reaches 585°C when they enter the cavity in front of the punch.

[0072] (3) In step 4, the injection speed is 3.5 m / s.

[0073] Example 4

[0074] The method for preparing metal particle-reinforced magnesium matrix composites in this example differs from that in Example 1 only in that:

[0075] (1) In step 2, the mass percentage of Ti particles in the composite material is 45%, and the mass percentage of AZ91D particles in the composite material is 55%.

[0076] (2) In step 3, the temperature of the mixed particles reaches 593°C when they enter the cavity in front of the punch.

[0077] (3) In step 4, the injection speed is 4.5 m / s

[0078] Example 5

[0079] The method for preparing metal particle-reinforced magnesium matrix composites by semi-solid injection molding in this example differs from that in Example 1 only in that: in step 3, the screw in the barrel rotates at a speed of 210 r / min.

[0080] Example 6

[0081] The method for preparing metal particle-reinforced magnesium matrix composites by semi-solid injection molding in this example differs from that in Example 1 only in that, in step 3, the screw in the barrel rotates at a speed of 295 r / min.

[0082] Example 7

[0083] The method for preparing metal particle-reinforced magnesium matrix composites in this example differs from that in Example 1 only in that: in step 5, a pressure of 210 MPa is applied and held.

[0084] Example 8

[0085] The method for preparing metal particle-reinforced magnesium matrix composites in this example differs from that in Example 1 only in that: in step 5, a pressure of 350 MPa is applied and held.

[0086] Example 9

[0087] The method for preparing metal particle-reinforced magnesium matrix composites in this example differs from that in Example 1 only in that the mold temperature is 205°C in step 4.

[0088] Example 10

[0089] The method for preparing metal particle-reinforced magnesium matrix composites in this example differs from that in Example 1 only in that the mold temperature is 296°C in step 4.

[0090] Comparative Example 1

[0091] The method for preparing metal particle-reinforced magnesium matrix composites by injection molding in this example differs from that in Example 1 only in that the particle size of the Ti particles in step 2 is approximately 40 μm.

[0092] Comparative Example 2

[0093] The method for preparing metal particle-reinforced magnesium matrix composites by injection molding in this example differs from that in Example 1 only in that: in step 2, the mass percentage of Ti particles in the composite material is 1.5%, and the mass percentage of AZ91D particles in the composite material is 98.5%.

[0094] Comparative Example 3

[0095] The method for preparing metal particle-reinforced magnesium matrix composites by injection molding in this example differs from that in Example 1 only in that, in step 3, the temperature of the mixed particles reaches 570°C when they enter the cavity in front of the punch.

[0096] Comparative Example 4

[0097] The method for preparing metal particle-reinforced magnesium matrix composites by injection molding in this example differs from that in Example 1 only in that: in step 2, the mass percentage of Ti particles in the composite material is 50%, and the mass percentage of AZ91D particles in the composite material is 50%.

[0098] Comparative Example 5

[0099] The method for preparing metal particle-reinforced magnesium matrix composites by injection molding in this example differs from that in Example 1 only in that, in step 3, the temperature of the mixed particles reaches 600°C when they enter the cavity in front of the punch.

[0100] Comparative Example 6

[0101] The method for preparing metal particle-reinforced magnesium matrix composites by injection molding in this example differs from that in Example 1 only in that, in step 3, the screw in the barrel rotates at 150 r / min.

[0102] Comparative Example 7

[0103] The method for preparing metal particle-reinforced magnesium matrix composites by injection molding in this example differs from that in Example 1 only in that the mold temperature is 180°C in step 4.

[0104] Comparative Example 8

[0105] The method for preparing metal particle-reinforced magnesium matrix composites in this example differs from that in Example 1 only in that the mold temperature is 315°C in step 4.

[0106] Comparative Example 9

[0107] The method for preparing metal particle-reinforced magnesium matrix composites by injection molding in this example differs from that in Example 1 only in that: in step 4, a pressure of 380 MPa is applied and held.

[0108] Comparative Example 10

[0109] The method for preparing metal particle-reinforced magnesium matrix composites by injection molding in this example differs from that in Example 1 only in that: in step 4, a pressure of 185 MPa is applied and held.

[0110] Comparative Example 11

[0111] The method for preparing metal particle-reinforced magnesium matrix composites by injection molding in this example differs from that in Example 1 only in that: in step 3, the temperature of the mixed particles reaches 572°C when they enter the cavity in front of the punch.

[0112] Comparative Example 12

[0113] The method for preparing metal particle-reinforced magnesium matrix composites in this example differs from that in Example 1 in that:

[0114] 1) In step 2, Ti particles and AZ91D particles are added to a vacuum ball mill for mixing. The ball mill speed is 150 r / min and the mixing time is 0.5 h to obtain mixed particles.

[0115] 2) In step 3, the screw in the barrel rotates at 400 r / min, and the temperature of the mixed particles reaches 585℃ when they enter the cavity in front of the punch.

[0116] 3) Step 4: When the volume of semi-solid slurry in the cavity in front of the punch reaches the set amount, the injection system of the semi-solid injection molding machine pushes the punch to inject the semi-solid slurry through the nozzle. The mold temperature is 380℃, the injection speed is 50mm / min, and after the slurry fills the mold cavity, a pressure of 70MPa is applied to hold the pressure.

[0117] Comparative Example 13

[0118] The method for preparing metal particle-reinforced magnesium matrix composites in this example differs from that in Example 1 in that:

[0119] 1) In step 2, Ti particles and AZ91D particles are added to a vacuum ball mill for mixing. The ball mill speed is 150 r / min and the mixing time is 0.5 h to obtain mixed particles.

[0120] 2) In step 3, the screw in the barrel rotates at 400 r / min, and the temperature of the mixed particles reaches 585℃ when they enter the cavity in front of the punch.

[0121] 3) Step 4: When the volume of semi-solid slurry in the cavity in front of the punch reaches the set amount, the injection system of the semi-solid injection molding machine pushes the punch to inject the semi-solid slurry through the nozzle. The mold temperature is 380℃, the injection speed is 3m / s, and after the slurry fills the mold cavity, a pressure of 70MPa is applied to hold the pressure.

[0122] Comparative Example 14

[0123] The method for preparing metal particle-reinforced magnesium matrix composites in this example differs from that in Example 1 in that:

[0124] 1) In step 2, Ti particles and AZ91D particles are added to a vacuum ball mill for mixing. The ball mill speed is 150 r / min and the mixing time is 0.5 h to obtain mixed particles.

[0125] 2) In step 3, the screw in the barrel rotates at 400 r / min, and the temperature of the mixed particles reaches 585℃ when they enter the cavity in front of the punch.

[0126] 3) Step 4: When the volume of semi-solid slurry in the cavity in front of the punch reaches the set amount, the injection system of the semi-solid injection molding machine pushes the punch to inject the semi-solid slurry through the nozzle. The mold temperature is 380℃, the injection speed is 3m / s, and after the slurry fills the mold cavity, a pressure of 300MPa is applied to hold the pressure.

[0127] Performance testing:

[0128] The density, average α-Mg grain size, and solid fraction of the composite materials prepared in Examples 1-10 and Comparative Examples 1-14 were tested respectively. The solid fraction was tested as follows: Samples were taken from the prepared composite materials, polished, and then etched with an etchant. Metallographic images were taken using an optical microscope. The 50x magnified metallographic images were imported into image processing software, and all spherical primary α-Mg particles were selected and circled. The percentage of the circled area in the image was calculated to obtain the solid fraction. The average diameter of the equal-area circle of primary α-Mg was taken as the average grain size of α-Mg. The density was measured according to GB / T 3850-2015. The performance data obtained according to the above testing method are shown in Table 1 below.

[0129] Table 1 Performance data of composite materials

[0130]

[0131] As shown in Table 1, the density of the magnesium-based composite materials prepared in Examples 1-10 of this invention is 1.8-2.5 g / cm³. 3 The average α-Mg grain size is 47–81 μm, and the solid fraction is 31–51%. It is lightweight and produces small α-Mg grains, which is beneficial for improving the mechanical properties of magnesium-based composites. In Comparative Examples 3–4 and 11–12, the melt solidified at the nozzle; and in Comparative Example 9, the casting had severe flash defects and was not properly formed, making it impossible to test the density, average α-Mg grain size, and solid fraction parameters.

[0132] The properties of the composite materials prepared in Examples 1-10 and Comparative Examples 1-14 were tested respectively. The test standards for room temperature (25℃) tensile strength, yield strength and elongation after fracture were in accordance with GB / T16865-2013, and the test standards for high temperature (100℃) tensile strength, yield strength and elongation after fracture were in accordance with GB / T228.2-2015. The mechanical property data of the composite materials prepared in Examples 1-10 and Comparative Examples 1-14 obtained according to the above test methods are shown in Table 2 below.

[0133] Table 2 Mechanical property data of composite materials

[0134]

[0135]

[0136] As shown in Table 2, the metal particle-reinforced magnesium-based composite materials prepared by semi-solid injection molding in Examples 1-10 of this invention exhibit good mechanical properties. Specifically, the tensile strength of the composite material at 25℃ is 302-386 MPa, the yield strength is 208-245 MPa, and the elongation at break is 10.3-12.8%. At 100℃, the tensile strength is 152-196 MPa, the yield strength is 98-127 MPa, and the elongation at break is 30.2-39.5%, demonstrating good mechanical properties even at high temperatures. At high temperatures, the elongation at break of the composite materials in Examples 1-10 of this invention is significantly higher than that in Comparative Examples 1-14, indicating that the composite materials of this invention possess good toughness and impact resistance at high temperatures.

[0137] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for preparing a magnesium-based composite material reinforced with metal particles, characterized in that: Includes the following steps: Magnesium alloy particles are mixed and ground with metal particles to obtain mixed particles; The mixed particles are heated to a semi-solid state during the shearing and mixing process to obtain a semi-solid slurry; The semi-solid slurry is injected into a mold, and then a holding pressure is applied to solidify the semi-solid slurry to obtain the metal particle reinforced magnesium matrix composite material. The mass ratio of the metal particles to the metal particle-reinforced magnesium matrix composite material is (2.5~45):100; The metal particles have a particle size of 0.1 μm. _ 20 μm; The liquidus temperature of the magnesium alloy particles is T. 液相 ℃, the temperature of the semi-solid slurry is T ℃, then (T 液相 -20)≤T≤T 液相 ; The rotational speed for shear mixing is 210-300 r / min; The temperature of the mold is 200-300℃; the holding pressure is 210-350MPa. The magnesium alloy particles include at least one of Mg-Al-Zn alloy and Mg-Al-Mn alloy; The metal particles are selected from at least one of Ti, Mn, and TC4; The metal particle-reinforced magnesium matrix composite material has a tensile strength of 152–196 MPa, a yield strength of 98–125 MPa, and an elongation at break of 25–38% at 100°C.

2. The method for preparing the metal particle-reinforced magnesium-based composite material according to claim 1, characterized in that: The magnesium alloy particles have a particle size of 0.2-2.5 mm.

3. The method for preparing the metal particle-reinforced magnesium-based composite material according to claim 1, characterized in that: The shear mixing is performed using a screw.

4. The method for preparing the metal particle-reinforced magnesium-based composite material according to claim 1, characterized in that: The injection speed is 3-5 m / s.

5. The application of the preparation method of the metal particle reinforced magnesium matrix composite material according to any one of claims 1 to 4 in the fields of new energy vehicles, drones or 3C products.

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