Method for preparing metal particle reinforced magnesium-based composite material through semi-solid injection molding

Abstract

The invention belongs to the field of metal-based composite material preparation, and particularly discloses a method for preparing a metal particle reinforced magnesium-based composite material through semi-solid injection molding, and the method comprises the following steps: mixing and grinding magnesium alloy particles and metal particles to obtain mixed particles; the mixed particles are heated to be in a semi-solid state in the shearing and mixing process, and semi-solid slurry is obtained; and injecting the semi-solid slurry into a mold, and then applying pressure to solidify and mold the semi-solid slurry to prepare the metal particle reinforced magnesium-based composite material. According to the preparation method disclosed by the invention, the mixed particles are heated into the semi-solid slurry under the action of shearing and mixing, so that the mixed particles can be uniformly distributed, the common defects of macrosegregation and local agglomeration of the composite material are overcome, and the solid particles in the semi-solid slurry tend to be spherical; the flexibility and the mechanical property of the prepared composite material at room temperature and high temperature are improved.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of metal matrix composites, and particularly relates to a method for preparing metal particle-reinforced magnesium matrix composites by semi-solid injection molding. Background Art

[0002] Magnesium alloys have a series of advantages such as low density, high specific strength, and easy recyclability, and are important lightweight structural materials. However, magnesium alloys have disadvantages such as low strength and toughness at room and high temperatures, which severely limit the application of magnesium alloys as high-stability support structural components. With the rapid development of industries such as new energy vehicles, unmanned aerial vehicles, and 3C, there is an urgent need to develop magnesium matrix composites with high strength, high toughness, and relatively high high-temperature strength to achieve the lightweight and safety reliability of equipment. Metal particle-reinforced magnesium matrix composites combine the low density of magnesium alloys and the high strength, high toughness, and high high-temperature strength of metal particles, and have great application potential, receiving extensive attention. However, the composites prepared by conventional stir casting have uneven particle distribution, many porosity and looseness defects, resulting in poor mechanical properties at room and high temperatures. Especially for preparing metal particle-reinforced magnesium matrix composites with a high mass fraction, due to the high melt viscosity and difficult feeding during solidification, the mechanical properties of the material decrease sharply.

[0003] The prior art discloses a semi-solid forming method for magnesium matrix composites. After mixing magnesium alloy powder and ceramic reinforcement phase powder, they are cold-pressed into a composite blank, and then the blank is placed in a heating device and heated to 300 - 650 °C. Then, the solid-liquid mixture is injected and filled into a mold to obtain a composite material. Before injection, the solid-liquid mixed slurry is not stirred, and the primary solid phase precipitated in the alloy has many sharp corners and is difficult to form a spherical shape. At the same time, due to the density difference between the reinforcement and the magnesium alloy melt, sedimentation will occur, and the prepared composite material is prone to macroscopic segregation of reinforcement particles. In addition, the solidus temperature of AZ91 alloy is 468 °C, and the liquidus temperature is 598 °C. Injection molding cannot be carried out in the temperature range of 300 - 470 °C, and at 650 °C, it is in a liquid state, belonging to liquid injection molding. Without taking stirring measures and keeping warm for 15 min at this temperature, obvious sedimentation of TiC particles will occur, resulting in uneven distribution of the reinforcement phase in the prepared composite material. In addition, the magnesium alloy used in this scheme is micron-sized, belonging to magnesium powder, which is extremely explosive and can only be used for powder metallurgy and cannot be used for injection molding. Summary of the Invention

[0004] In order to overcome at least one of the above technical problems existing in the prior art, one of the purposes of the present invention is to provide a method for preparing metal particle-reinforced magnesium matrix composites, and the metal particle-reinforced magnesium matrix composites prepared by this preparation method have excellent mechanical properties at both room and high temperatures.

[0005] The second object of the present invention is to provide an application of the preparation method of the above-mentioned metal particle-reinforced magnesium matrix composite material in the fields of new energy vehicles, drones or 3C products.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The first aspect of the present invention provides a preparation method of a metal particle-reinforced magnesium matrix composite material, comprising the following steps:

[0008] Mix and grind magnesium alloy particles and metal particles to obtain mixed particles;

[0009] Heat the mixed particles to a semi-solid state during shear mixing to obtain a semi-solid slurry;

[0010] Inject the semi-solid slurry into a mold, and then apply a holding pressure to solidify the semi-solid slurry to form the metal particle-reinforced magnesium matrix composite material.

[0011] In the present invention, by mixing and grinding magnesium alloy particles and metal particles, the metal particles are uniformly distributed on the surface of the magnesium alloy particles, and then the mixed particles are heated to make the mixed particles into a semi-solid slurry. Shear mixing is carried out during the heating process, which can make the metal particles more uniformly dispersed. Then the semi-solid slurry is injection molded and solidified under the holding pressure to realize the feeding effect on 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 is (2.5 to 45):100; in some embodiments of the present invention, the mass ratio of the metal particles to the metal particle-reinforced magnesium matrix composite 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, 16:100, 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 value formed by any two of them. When the mass ratio of the metal particles to the composite is (2.5 to 30):100, by adjusting the injection temperature, the solid fraction (the weight percentage of non-dendritic primary α-Mg precipitated in the magnesium alloy in the magnesium alloy slurry) in the semi-solid slurry is controlled at 30-51%; when the mass ratio of the metal particles to the composite is (30 to 45):100, by adjusting the injection temperature, the solid fraction in the semi-solid slurry is controlled at 20-30%. The semi-solid slurry in the present invention contains magnesium alloy liquid, 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 the present invention is to control the total solid fraction (i.e., (primary α-Mg + solid metal particles) / semi-solid slurry) from being too high. If the solid fraction is too high, the viscosity of the semi-solid slurry will be very high and it cannot be injection molded. To ensure that the semi-solid slurry can be injection molded, the total solid fraction needs to be controlled within the range of 35-75%. Preferably, the solid fraction needs to be controlled at about 50%. Therefore, when increasing the amount of metal particles, the solid fraction needs to be reduced, and when reducing the amount of metal particles, the solid fraction needs to be increased, so as to maintain the solid fraction in the semi-solid slurry at about 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 a magnesium alloy ingot into metal particles.

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

[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 among 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, 2.5 mm or the range value formed by any two of them. When the particle size of the magnesium alloy particles is less than 0.2 mm, it is difficult to cut and granulate the magnesium alloy ingot into particles, and the efficiency is too low. When the particle size of the magnesium alloy particles is greater than 2.5 mm, the size difference from the metal particles is too large, and it is 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 among 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 or the range value formed by any two of them.

[0020] In the present 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 process of mixing and grinding the magnesium alloy particles and the metal particles, the metal particles aggregate 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 shape of the metal particles is spherical or irregular.

[0022] In some embodiments of the present invention, the rotation speed of the hybrid grinding is 100 - 200 r / min; in some embodiments of the present invention, the rotation speed of the hybrid grinding is any value among 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, 200 r / min or the range value formed by any two of them.

[0023] In some embodiments of the present invention, the time of the hybrid grinding is 1 - 10 h; in some embodiments of the present invention, the time of the hybrid grinding is 2 - 3 h. 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 the protection of vacuum or inert gas, oxidation will occur, reducing the performance and strength of the prepared magnesium matrix composite material.

[0024] In some embodiments of the present invention, the atmosphere of the hybrid grinding is vacuum or 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 °C, and the temperature of the semi-solid slurry is T °C, then (T 液相 - 20) ≤ T ≤ T 液相 . If the temperature of the semi-solid slurry is lower than (T 液相 - 20) °C, the semi-solid slurry has started to solidify before being injected into the cavity of the mold, and injection molding cannot be achieved; if the temperature of the semi-solid slurry is higher than T 液相 °C, then no semi-solid slurry can be formed, and the mechanical properties of the magnesium matrix composite material obtained after injection molding are poor.

[0027] In some embodiments of the present invention, the rotation speed of the shear mixing is 200 - 300 r / min; in some embodiments of the present invention, the rotation speed of the shear mixing is any value among 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, 300 r / min or the range value formed by any two of them. When the rotation speed of the shear mixing is lower than 200 r / min, the shear mixing effect is weakened, the transmission speed is slow, and the preparation efficiency is low. When the rotation speed of the shear mixing is higher than 300 r / min, the requirements for the stiffness of the screw and devices such as the equipment motor are too high, and it is difficult to achieve with current equipment.

[0028] In some embodiments of the present invention, the shear mixing is carried out by a screw. When carrying out shear mixing by a screw, on the one hand, the mixed particles are conveyed by the screw to the injection position, and the mixed particles are heated into a semi-solid slurry (the metal particles are solid, and the magnesium alloy particles are melted into a semi-solid state). On the other hand, the rotation of the screw also plays a role in shear stirring and mixing. Through shear stirring, not only the distribution of the metal particles and the solid phase in the magnesium alloy becomes more uniform, avoiding their sedimentation in the semi-solid or liquid melt, but also the dendritic primary α-Mg solid phase in the magnesium alloy is transformed from a multi-angular irregular shape into a spherical shape under the action of external force, which is beneficial to 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 preparation method including the following steps:

[0030] The mixed particles are added into the hopper of the injection molding device, and then conveyed to the barrel at a temperature of T °C through the feeding screw of the hopper. The screw in the barrel rotates and feeds at a rate of 200 - 300 r / min, and the mixed particles 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 °C, and the temperature of the barrel is the same as that of the semi-solid slurry. The mixed particles are heated in the barrel at a set temperature of T °C and become a semi-solid slurry.

[0032] In some embodiments of the present invention, the temperature of the mold is 200 - 300 °C; in some embodiments of the present invention, the temperature of the mold is any value among 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, 250 °C, 260 °C, 270 °C, 280 °C, 290 °C, 300 °C or any range value formed by any two of them. If the temperature of the mold is lower than 200 °C, 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 likely to occur. If the temperature of the mold is higher than 300 °C, the cooling rate of the semi-solid slurry is too slow, and the second phase is likely to grow, affecting the mechanical properties of the obtained composite material.

[0033] In some embodiments of the present invention, the injection speed is 3 - 5 m / s; in some embodiments of the present invention, the injection speed is any value among 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, 5 m / s or the range value formed by any two of them. When the injection speed is lower than 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 likely to occur. When the injection speed is higher than 5 m / s, the semi-solid slurry is prone to entrap air during filling, and pores are likely to form in the obtained composite material.

[0034] In some embodiments of the present invention, the holding pressure is 200 - 350 MPa; in some embodiments of the present invention, the holding pressure is any value among 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, 350 MPa or the range value formed by any two of them. When the holding pressure is less than 200 MPa, micro-porosity defects are likely to occur in the obtained composite material. If the holding pressure is greater than 350 MPa, the tendency to generate pinhole defects in the obtained composite material increases. The injection molding process of the present invention is stable, and there is pressure feeding during the solidification process. The composite material has few pore defects and high density, and can be subjected to T6 heat treatment. After the semi-solid slurry is injected into the cavity of the mold in the present invention, the holding pressure is applied before solidification, which is beneficial to the feeding of the semi-solid slurry. If the holding pressure is applied after the semi-solid slurry solidifies, the feeding effect cannot be achieved.

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

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

[0037] In some embodiments of the present invention, the elongation at break of the composite material at 25 °C is 8.5 - 12.5%.

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

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

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

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

[0042] Mix and grind magnesium alloy particles and metal particles under vacuum or inert atmosphere to obtain mixed particles;

[0043] Add the mixed particles into the hopper of an injection molding device, and then convey them to the barrel through the feeding screw of the hopper. The screw in the barrel rotates at a rate of 200-300 r / min to feed the material, and the mixed particles are heated into semi-solid slurry in the barrel;

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

[0045] Inject the semi-solid slurry into a mold at a temperature of 200-300 °C at an injection speed of 3-5 m / s, and then apply a holding pressure of 200-350 MPa to solidify and form the semi-solid slurry, thereby obtaining the metal particle-reinforced magnesium matrix composite material.

[0046] In the present invention, the mixed particles are added into the hopper of the injection molding device; the feeding screw in the hopper continuously feeds the mixed particles into the barrel that has been heated to the set temperature T °C through rotation; the screw in the barrel rotates to push the mixed particles towards the cavity in front of the punch (i.e., the injection position), and the mixed particles move and mix under the rotational shear force of the screw in the barrel, and are heated up to reach the semi-solid state during movement, becoming semi-solid slurry (the reinforcing particles are solid, and the magnesium alloy melts into semi-solid). In addition to pushing the mixed particles or slurry, the rotation of the screw in the barrel also plays a role of shear stirring. Through shear stirring, the solid-phase distribution of the metal particles and the magnesium alloy matrix becomes more uniform, avoiding their settlement in the semi-solid or liquid melt; at the same time, the solid phase in the magnesium alloy matrix changes from a multi-edged irregular shape to a spherical shape under the action of external force, which is beneficial to improving the toughness of the composite material. If the rotation speed of the screw in the barrel is too low and the shear force is too small, the particles are prone to agglomeration. About 50% of the semi-solid slurry is liquid magnesium alloy, and the density of the added metal particles is greater than that of the magnesium alloy melt. Without the shear force of the screw, the metal particles will settle naturally, resulting in uneven composition distribution.

[0047] The second aspect of the present invention provides an 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 the present invention are as follows: In the preparation method of the present invention, by heating the mixed particles to semi-solid slurry under the action of shear mixing, the distribution of the mixed particles can be made uniform, solving the common macroscopic segregation and local agglomeration defects of composite materials, and making the shape of the primary α-Mg in the semi-solid slurry tend to be spherical, improving the flexibility and mechanical properties of the prepared composite material at room temperature and high temperature. Specifically, the tensile strength of the composite material at 25°C 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°C is 152-196 MPa, the yield strength is 98-125 MPa, and the elongation at break is 25-38%. It still maintains good flexibility and mechanical properties at high temperature, which is beneficial to the long-term use of the composite material in a high-temperature environment. Description of the Drawings

[0049] Figure 1 It is a physical picture of the AZ91D magnesium alloy matrix particles in Example 1.

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

[0051] Figure 3 It is an SEM image of the composite material prepared in Example 1. Detailed Embodiments

[0052] The following further describes in detail the specific implementation of the present invention in conjunction with the drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that for the processes not specifically described in detail below, those skilled in the art can all realize or understand them with reference to the prior art. The reagents or instruments used without indicating the manufacturer can all be conventional products that can be purchased through the market.

[0053] Example 1

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

[0055] Step 1: Using a granulator, process commercially available AZ91D ingots into irregular long strip-shaped particles to obtain AZ91D magnesium alloy matrix particles (the physical picture is as Figure 1 shown), and the size in the length direction is 2 mm.

[0056] Step 2: Use Ti particles as reinforcement, the average particle size of the titanium particles used is 15μm, and the mass percentage of Ti particles in the composite material is 12.5%, and the mass percentage of AZ91D particles in the composite material is 87.5%. Add Ti particles and AZ91D particles into a vacuum ball mill for mixing. The ball mill speed is 150r / min, and the mixing time is 2.5h to obtain mixed particles. The SEM image of the mixed particles is tested by scanning electron microscopy, as shown in the following figure. Figure 2 shown. Figure 2 The white particles are Ti particles, and the dark particles are AZ91D particles, indicating that the Ti particles adhere to and are evenly distributed on the surface of the AZ91D particles after ball milling.

[0057] Step 3: Add the mixed particles in 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 feeding screw, input the mixed particles into the preheated barrel, and rotate the screw in the barrel at 250r / min. Adjust the power of the electric heating element outside the barrel so that the temperature of the mixed particles reaches 585℃ (the liquidus line of AZ91D magnesium alloy is 595℃) when entering the cavity in front of the punch, and obtain a semi-solid slurry;

[0058] Step 4: When the volume of the 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°C and the injection speed is 3m / s. After the slurry fills the mold cavity, a pressure of 300MPa is applied to maintain the pressure.

[0059] Step 5: After the semi-solid slurry is solidified in the mold, the mold is opened and the composite material casting is taken out to obtain the metal particle reinforced magnesium-based composite material in this example.

[0060] The SEM image of the composite material prepared in this example was tested by scanning electron microscopy. Figure 3 As shown. Figure 3 It can be seen that the titanium particles in the composite material ( Figure 3 The white particles are evenly distributed in the macroscopic manner, without any defects such as macroscopic segregation, microscopic agglomeration, or holes.

[0061] Example 2

[0062] This example provides a method for preparing a metal particle reinforced magnesium-based composite material by semi-solid injection molding, which specifically includes the following steps:

[0063] Step 1: Use a granulator to process the commercially available AM60B ingot into irregular long strips of particles with a length dimension of 1 mm.

[0064] Step 2: Use Ti particles as reinforcement. The average particle size of the titanium particles used is 10 μm. 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%. Add the Ti particles and AM60B particles into a vacuum ball mill for mixing. The ball mill speed is 300 r / min and the mixing time is 3 hours to obtain mixed particles.

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

[0066] Step 4: When the volume of the 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 4m / s. After the semi-solid slurry fills the mold cavity, a pressure of 320MPa is applied to maintain the pressure;

[0067] Step 5: After the semi-solid slurry is solidified in the mold, the mold is opened and the composite material casting is taken out to obtain the metal particle reinforced magnesium-based composite material in this example.

[0068] Example 3

[0069] The method for preparing metal particle reinforced magnesium-based composite materials by semi-solid injection molding in this example is different 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 entering 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-based composite materials by semi-solid injection molding in this example is different 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 entering 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 the metal particle-reinforced magnesium matrix composite by semi-solid injection molding in this example is only different from that in Example 1 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 the metal particle-reinforced magnesium matrix composite by semi-solid injection molding in this example is only different from that in Example 1 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 the metal particle-reinforced magnesium matrix composite by semi-solid injection molding in this example is only different from that in Example 1 in that: in Step 5, a pressure of 210 MPa is applied for pressure holding.

[0084] Example 8

[0085] The method for preparing the metal particle-reinforced magnesium matrix composite by semi-solid injection molding in this example is only different from that in Example 1 in that: in Step 5, a pressure of 350 MPa is applied for pressure holding.

[0086] Example 9

[0087] The method for preparing the metal particle-reinforced magnesium matrix composite by semi-solid injection molding in this example is only different from that in Example 1 in that: in Step 4, the mold temperature is 205 °C.

[0088] Example 10

[0089] The method for preparing the metal particle-reinforced magnesium matrix composite by semi-solid injection molding in this example is only different from that in Example 1 in that: in Step 4, the mold temperature is 296 °C.

[0090] Comparative Example 1

[0091] The method for preparing the metal particle-reinforced magnesium matrix composite by injection molding in this example is only different from that in Example 1 in that: in Step 2, the particle size of the Ti particles is about 40 μm.

[0092] Comparative Example 2

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

[0094] Comparative Example 3

[0095] The method for preparing the metal particle-reinforced magnesium matrix composite material by injection molding in this example is only different from that in Example 1 in that: in Step 3, the temperature of the mixed particles reaches 570 °C when entering the cavity in front of the punch.

[0096] Comparative Example 4

[0097] The method for preparing the metal particle-reinforced magnesium matrix composite material by injection molding in this example is only different from that in Example 1 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 the metal particle-reinforced magnesium matrix composite material by injection molding in this example is only different from that in Example 1 in that: in Step 3, the temperature of the mixed particles reaches 600 °C when entering the cavity in front of the punch.

[0100] Comparative Example 6

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

[0102] Comparative Example 7

[0103] The method for preparing the metal particle-reinforced magnesium matrix composite material by injection molding in this example is only different from that in Example 1 in that: in Step 4, the mold temperature is 180 °C.

[0104] Comparative Example 8

[0105] The method for preparing the metal particle-reinforced magnesium matrix composite material by injection molding in this example is only different from that in Example 1 in that: in Step 4, the mold temperature is 315 °C.

[0106] Comparative Example 9

[0107] The method for preparing the metal particle-reinforced magnesium matrix composite material by injection molding in this example is only different from that in Example 1 in that: in Step 4, a pressure of 380 MPa is applied for pressure holding.

[0108] Comparative Example 10

[0109] The method for preparing the metal particle-reinforced magnesium matrix composite material by injection molding in this example is only different from that in Example 1 in that: in Step 4, a pressure of 185 MPa is applied for pressure holding.

[0110] Comparative Example 11

[0111] The difference between the method for preparing metal particle-reinforced magnesium matrix composite by injection molding in this example and that in Example 1 is only that: in step 3, the temperature of the mixed particles reaches 572 °C when entering the cavity in front of the punch.

[0112] Comparative Example 12

[0113] The difference between the method for preparing metal particle-reinforced magnesium matrix composite by injection molding in this example and that in Example 1 lies in:

[0114] 1) In step 2, Ti particles and AZ91D particles are added to a vacuum ball mill for powder mixing. The rotation speed of the ball mill 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 °C when entering the cavity in front of the punch;

[0116] 3) Step 4: When the volume of the semi-solid slurry at 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 °C, the injection speed is 50 mm / min, and after the slurry fills the mold cavity, a pressure of 70 MPa is applied for pressure holding.

[0117] Comparative Example 13

[0118] The difference between the method for preparing metal particle-reinforced magnesium matrix composite by injection molding in this example and that in Example 1 lies in:

[0119] 1) In step 2, Ti particles and AZ91D particles are added to a vacuum ball mill for powder mixing. The rotation speed of the ball mill 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 °C when entering the cavity in front of the punch;

[0121] 3) Step 4: When the volume of the semi-solid slurry at 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 °C, the injection speed is 3 m / s, and after the slurry fills the mold cavity, a pressure of 70 MPa is applied for pressure holding.

[0122] Comparative Example 14

[0123] The difference between the method for preparing metal particle-reinforced magnesium matrix composite by injection molding in this example and that in Example 1 lies in:

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

[0125] 2) In step 3, the screw in the barrel rotated at 400 r / min, and the temperature of the mixed particles reached 585 °C when entering the cavity in front of the punch;

[0126] 3) Step 4: When the volume of the semi-solid slurry at the cavity in front of the punch reached the set amount, the injection system of the semi-solid injection molding machine pushed the punch to inject the semi-solid slurry through the nozzle. The mold temperature was 380 °C, the injection speed was 3 m / s, and after the slurry filled the mold cavity, a pressure of 300 MPa was applied for pressure holding.

[0127] Performance test:

[0128] The density, average grain size of α-Mg, and solid fraction of the composite materials prepared in Examples 1 to 10 and Comparative Examples 1 to 14 were tested respectively. Among them, the test method for the solid fraction was as follows: First, samples were taken from the prepared composite materials. After the samples were polished, they were corroded with a corrosion solution, and then metallographic photos were taken with an optical microscope. The metallographic pictures magnified 50 times were imported into the graphic processing software, and all spherical primary α-Mg were selected and circled, and the proportion of the circled area in the picture was calculated to obtain the solid fraction. The average equivalent circle diameter of the primary α-Mg was used as the average grain size of α-Mg; the measurement standard for density referred to "GB / T 3850-2015", and the performance data measured according to the above test method are shown in Table 1 below.

[0129] Table 1 Performance data of the composite materials

[0130]

[0131] As can be seen from Table 1, the density of the magnesium-based composite materials prepared in Examples 1 to 10 of the present invention was 1.8 - 2.5 g / cm 3 , the average grain size of α-Mg was 47 - 81 μm, and the solid fraction was 31 - 51%. It had the characteristics of light weight and smaller grain size of the generated α-Mg crystals, which was beneficial to improving the mechanical properties of the magnesium-based composite materials. In Comparative Examples 3 - 4, the melt solidified at the nozzle, and in Comparative Example 9, due to serious flash defects in the casting and non-forming, the density, average grain size of α-Mg, and solid fraction parameters could not be tested.

[0132] The properties of the composite materials prepared in Examples 1-10 and Comparative Examples 1-14 were tested separately. Among them, the test standards for tensile strength, yield strength and elongation after fracture at room temperature (25 °C) refer to "GB / T 16865-2013", and the test standards for tensile strength, yield strength and elongation after fracture at high temperature (100 °C) refer to "GB / T 228.2-2015". The mechanical property data of the composite materials prepared in Examples 1-10 and Comparative Examples 1-14 measured 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 can be seen from Table 2, the metal particle-reinforced magnesium matrix composite materials prepared by semi-solid injection molding in Examples 1-10 of the present invention have good mechanical properties. Specifically, the tensile strength of the composite material at 25 °C is 302-386 MPa, the yield strength is 208-245 MPa, and the elongation at break is 10.3-12.8%. The tensile strength of the composite material at a high temperature of 100 °C is 152-196 MPa, the yield strength is 98-127 MPa, and the elongation at break is 30.2-39.5%. It still has good mechanical properties at high temperature. At high temperature, the elongation at break of the composite materials in Examples 1-10 of the present invention is significantly higher than that of Comparative Examples 1-14, indicating that the composite materials in the present invention have good toughness and impact resistance at high temperature.

[0137] The above has described the embodiments of the present invention in detail. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the purpose of the present invention. In addition, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

Claims

1. A method for preparing a metal particle reinforced magnesium-based composite material, characterized in that: The following steps are involved: Mixing and grinding magnesium alloy particles with metal particles to obtain mixed particles; heating the mixed particles to a semi-solid state during shear mixing 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-based composite material.

2. The method for preparing the metal particle reinforced magnesium-based composite material according to claim 1, characterized in that: The mass ratio of the metal particles to the metal particle reinforced magnesium-based composite material is (2.5-45):

100.

3. The method for preparing the metal particle reinforced magnesium-based composite material according to claim 1 or 2, characterized in that: The magnesium alloy particles include at least one of Mg-Al-Zn alloy and Mg-Al-Mn alloy; And / or, the metal particles are selected from at least one of Ti, Mn, and TC4.

4. The method for preparing the metal particle reinforced magnesium-based composite material according to claim 1 or 2, characterized in that: The particle size of the magnesium alloy particles is 0.2-2.5 mm; And / or, the particle size of the metal particles is 0.1 μm-20 μm.

5. The method for preparing the metal particle reinforced magnesium-based composite material according to claim 1, characterized in that: 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 Mutually.

6. The method for preparing the metal particle reinforced magnesium-based composite material according to claim 1, characterized in that: The rotation speed of the shear mixing is 200-300r / min; And / or, the shear mixing is performed by using a screw.

7. The method for preparing the metal particle reinforced magnesium-based composite material according to claim 1, characterized in that: The temperature of the mold is 200-300°C.

8. 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.

9. The method for preparing the metal particle reinforced magnesium-based composite material according to claim 1, characterized in that: The holding pressure is 200-350 MPa.

10. Application of the preparation method of the metal particle reinforced magnesium-based composite material according to any one of claims 1 to 9 in the fields of new energy vehicles, unmanned aerial vehicles or 3C products.

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