Preparation method of three-dimensional connected porous high volume fraction chopped carbon fiber doped SiC particle reinforced magnesium-based composite rod

Abstract

A method for preparing a three-dimensionally connected porous high volume fraction chopped carbon fiber doped SiC particle reinforced magnesium-based composite rod relates to a method for preparing a reinforced magnesium-based composite rod. The present invention aims to solve the technical problem that existing high volume fraction reinforcement reinforced magnesium-based composite materials cannot undergo subsequent thermal deformation and secondary processing to obtain high modulus, high strength magnesium-based rods. The present invention first improves the interfacial activity between chopped carbon fibers and SiC particles through ultrasonic electromagnetic stirring, and the temperature differential segmented binder crystal phase transformation makes the preform three-dimensionally connected and the structure stable; then, multi-directional graded capillary infiltration allows the melt to fill the entire preform cavity to improve the interface bonding strength, and isothermal multi-stage variable ratio rapid molding refines the grains, directionalizes the fiber distribution, and improves the interface bonding; the strength and modulus of the magnesium-based composite rod prepared by multi-directional graded capillary infiltration and isothermal multi-stage variable ratio rapid molding under the action of ultrasonic electromagnetic stirring and differential temperature segmented control are significantly improved.

Description

Technical Field

[0001] The invention relates to a preparation method of a dual-phase (SiC particles+chopped carbon fibers) reinforced magnesium-based composite rod. Background Art

[0002] Currently, traditional magnesium alloys have defects such as low yield strength and tensile strength, low elastic modulus, and poor creep resistance, making them unable to meet the requirements of high-tech fields for high-strength, high-modulus materials. Magnesium-based composites reinforced with high volume fraction reinforcements not only have a low thermal expansion coefficient and good thermal conductivity, but also have good strength and a high elastic modulus. However, since the reinforcements are all ceramic hard phase particles, their disadvantages are also obvious. They cannot undergo subsequent thermal deformation and secondary processing, resulting in the inability to further refine the grains through deformation, improve interfacial bonding, and thus improve the performance of the material. In previous studies, magnesium-based composites with a single ceramic reinforcement volume fraction higher than 30% have not been subjected to deformation treatments such as hot extrusion. Summary of the Invention

[0003] The present invention aims to solve the technical problem that existing high volume fraction reinforcement reinforced magnesium-based composite materials cannot undergo subsequent thermal deformation and secondary processing, and provides a preparation method for three-dimensional interconnected porous high volume fraction short carbon fiber doped SiC particle reinforced magnesium-based composite rods.

[0004] The preparation method of the three-dimensional interconnected porous high volume fraction chopped carbon fiber doped SiC particle reinforced magnesium-based composite rod of the present invention is carried out by the following steps:

[0005] 1. Preparation of a three-dimensional interconnected porous high volume fraction short carbon fiber doped silicon carbide particle dual-phase preform: chopped carbon fiber and SiC particles are mixed together, and then deionized water is added, followed by a binder and a dispersant. The mixture is ultrasonically and electromagnetically stirred at 30°C to 60°C for 50min to 70min, poured into a pre-pressing mold for compression molding, freeze-dried at low temperature to remove moisture, and then subjected to differential temperature segmentation control and naturally cooled to room temperature to obtain a three-dimensional interconnected porous high volume fraction short carbon fiber doped silicon carbide particle dual-phase preformed cylinder. The pore diameter of the preform rod is 10μm to 50μm, and the porosity is 45% to 55%;

[0006] The volume ratio of the chopped carbon fibers to the SiC particles is 1:(4-19);

[0007] The binder is acidic aluminum phosphate, wherein the atomic ratio of P element to Al element is 23:1;

[0008] The volume ratio of the binder to deionized water is 1:(10-15), the volume ratio of the binder to the reinforcement is (1.5-3):15, and the reinforcement is a mixture of chopped carbon fibers and SiC particles;

[0009] The dispersant is polyacrylamide particles, the mass ratio of the reinforcement to the dispersant is 1:(0.004-0.005), and the reinforcement is a mixture of chopped carbon fibers and SiC particles;

[0010] The process of differential temperature segmented control is as follows: heat preservation is performed at four temperature points of 200°C, 400°C, 600°C and 800°C in order from low to high, the heat preservation time at 200°C, 400°C and 600°C is 25min to 30min, and the heat preservation time at 800°C is 180min to 190min;

[0011] 2. The three-dimensional connected porous high volume fraction short carbon fiber doped SiC particle two-phase prefabricated cylinder obtained in step 1 is placed in a forming mold with the central axes of the two coinciding, and then the forming mold is preheated to 480°C to 520°C, and a 700°C magnesium alloy solution is cast into the forming mold. Under two-stage isothermal pressurization, the magnesium alloy solution is multi-directionally coated on the preform for multi-directional graded capillary infiltration; isothermal multi-stage variable ratio rapid forming is then performed to obtain a high volume fraction short carbon fiber doped SiC particle reinforced magnesium-based composite rod;

[0012] The inner cavity of the forming mold is cylindrical, and the ratio of the inner diameter of the forming mold to the diameter of the preform is 8:(5-7);

[0013] The steps of multi-directional capillary infiltration of the preform by the magnesium alloy solution under two-stage isothermal pressure are as follows: first stage: all-directional infiltration and pressure holding in the mold cavity for 3 minutes to 7 minutes under the conditions of temperature of 480°C to 520°C and pressure of 140kN to 230kN; second stage: capillary infiltration of all pores of the preform for 5 minutes to 10 minutes under the conditions of temperature of 480°C to 520°C and pressure of 140kN to 230kN; the hot pressing temperature of the first stage and the second stage is the same, the pressure of the first stage is lower than that of the second stage, and the pressure holding time of the first stage is lower than that of the second stage;

[0014] The isothermal multi-stage variable ratio rapid prototyping process comprises the following steps: performing a first extrusion at a temperature of 450° C. to 500° C., a pressure of 360 MPa to 480 MPa, and a speed of 0.05 mm / s to 0.01 mm / s, wherein the extrusion ratio of the first extrusion is 10:(1 to 3); and performing a second extrusion at a temperature of 450° C. to 500° C., a pressure of 480 MPa to 690 MPa, and a speed of 0.01 mm / s to 0.05 mm / s, wherein the extrusion ratio of the second extrusion is 8:(4 to 5).

[0015] The design principle of the present invention is as follows: Due to the different sizes of chopped carbon fibers and SiC particles, the chopped carbon fibers and SiC particles are formed into a porous preform with a three-dimensional cavity skeleton structure through a binder. The preform has the advantages of high porosity, good permeability and high temperature resistance, which is conducive to subsequent secondary processing; secondly, the chopped carbon fibers can release stress by adjusting the distribution direction during the thermal deformation of the material, thereby playing a role in coordinating deformation.

[0016] The present invention improves the interfacial activity of chopped carbon fibers and SiC particles through ultrasonic electromagnetic stirring in step one, and the temperature-differential segmented binder crystal transformation makes the preform three-dimensionally connected and the structure stable; in step two, multi-directional graded capillary infiltration allows the melt to fill the entire preform cavity, thereby improving the interface bonding strength, and isothermal multi-stage variable ratio rapid molding refines the grains, orients the fibers, and improves the interface bonding; the strength and modulus of the magnesium-based composite rods prepared by multi-directional graded capillary infiltration and isothermal multi-stage variable ratio rapid molding under the action of ultrasonic electromagnetic stirring and temperature-differential segmented control are significantly improved.

[0017] Beneficial effects of the present invention:

[0018] The present invention prepares a three-dimensional interconnected porous high volume fraction short carbon fiber doped silicon carbide particle two-phase preform in the first step, forms a three-dimensional cavity skeleton structure by overlapping the short carbon fiber and the SiC particles, achieves high porosity and strong permeability, and then combines with low-temperature freeze drying to remove moisture, and differential temperature segmented control to promote the decomposition and transformation of the binder crystal form in different temperature ranges, thereby improving the strength and high temperature resistance of the preform; in the second step, the preform obtained in the first step is subjected to isothermal multi-directional graded capillary infiltration, and the melt is promoted to flow from multiple directions by realizing the radial difference between the mold and the preform (the inner diameter of the mold is larger than the diameter of the preform). The melt is then infiltrated simultaneously into the preform's three-dimensional network cavity. Graded capillary infiltration enhances melt fluidity and eliminates alloy inclusions. The isothermal, multi-directional interaction enables the melt to quickly and fully infiltrate the porous preform with a three-dimensional cavity skeleton structure, effectively increasing the material's density and enhancing the interfacial bonding with the magnesium alloy matrix, eliminating agglomeration and casting defects. The preform is then placed in an extrusion cup for multi-stage variable ratio rapid prototyping, significantly refining the grains. The multi-stage variable ratio improves the preform's pore structure, altering the orientation distribution of the chopped carbon fibers, further enhancing interfacial bonding strength and promoting rapid prototyping. The strength and modulus of the three-dimensionally interconnected, porous, high-volume-fraction chopped carbon fiber-doped silicon carbide particle dual-phase preform, and the composite rods produced through multi-stage variable ratio rapid prototyping, are significantly improved, with tensile strength exceeding 320 MPa and modulus reaching 156 GPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a photo of the three-dimensional interconnected porous high volume fraction short carbon fiber doped silicon carbide particle dual-phase prefabricated cylinder prepared in step 1 of experiment 1;

[0020] Figure 2 This is a photo of the as-cast composite material after multi-directional capillary infiltration of the preform by multi-directionally coating the preform with a magnesium alloy solution under two-stage isothermal pressure in step 2 of experiment 1;

[0021] Figure 3 Schematic diagram of the forming mold in step 2 of experiment 1;

[0022] Figure 4 Actual photo of the high volume fraction reinforced magnesium-based composite extruded rod prepared in Experiment 1;

[0023] Figure 5 This is a schematic diagram of the extrusion cup used for isothermal multi-stage variable ratio rapid prototyping in step 2 of experiment 1;

[0024] Figure 6 The engineering stress-engineering strain curves of test 1 and test 2 are shown;

[0025] Figure 7 This is the low-magnification OM image of the high volume fraction reinforced magnesium-based composite extruded rod prepared in Experiment 1;

[0026] Figure 8 This is a high-magnification OM image of the high volume fraction reinforced magnesium-based composite extruded rod prepared in Experiment 1;

[0027] Figure 9 This is a low-magnification SEM image of the tensile fracture of the high volume fraction reinforced magnesium-based composite extruded rod in Experiment 1;

[0028] Figure 10 This is a high-magnification SEM image of the tensile fracture of the high volume fraction reinforced magnesium-based composite extruded rod in test 1;

[0029] Figure 11 The engineering stress-engineering strain curves of Test 3 and Test 4 are shown. DETAILED DESCRIPTION

[0030] Specific embodiment 1: This embodiment is a method for preparing a three-dimensional connected porous high volume fraction short carbon fiber doped SiC particle reinforced magnesium-based composite rod, which is specifically carried out in the following steps:

[0031] 1. Preparation of a three-dimensional interconnected porous high volume fraction short carbon fiber doped silicon carbide particle dual-phase preform: the short carbon fiber and SiC particles are mixed together, and then deionized water is added, followed by a binder and a dispersant. The mixture is ultrasonically and electromagnetically stirred at 30°C to 60°C for 50min to 70min, poured into a pre-pressing mold for compression molding, freeze-dried at low temperature to remove moisture, and then subjected to differential temperature segmentation control and naturally cooled to room temperature to obtain a three-dimensional interconnected porous high volume fraction short carbon fiber doped silicon carbide particle dual-phase preformed cylinder;

[0032] The volume ratio of the chopped carbon fibers to the SiC particles is 1:(4-19);

[0033] The binder is acidic aluminum phosphate, wherein the atomic ratio of P element to Al element is 23:1;

[0034] The volume ratio of the binder to deionized water is 1:(10-15), the volume ratio of the binder to the reinforcement is (1.5-3):15, and the reinforcement is a mixture of chopped carbon fibers and SiC particles;

[0035] The dispersant is polyacrylamide particles, the mass ratio of the reinforcement to the dispersant is 1:(0.004-0.005), and the reinforcement is a mixture of chopped carbon fibers and SiC particles;

[0036] The process of differential temperature segmented control is as follows: heat preservation is performed at four temperature points of 200°C, 400°C, 600°C and 800°C in order from low to high, the heat preservation time at 200°C, 400°C and 600°C is 25min to 30min, and the heat preservation time at 800°C is 180min to 190min;

[0037] 2. The three-dimensional connected porous high volume fraction short carbon fiber doped SiC particle two-phase prefabricated cylinder obtained in step 1 is placed in a forming mold with the central axes of the two coinciding, and then the forming mold is preheated to 480°C to 520°C, and a 700°C magnesium alloy solution is cast into the forming mold. Under two-stage isothermal pressurization, the magnesium alloy solution is multi-directionally coated on the preform for multi-directional graded capillary infiltration; isothermal multi-stage variable ratio rapid forming is then performed to obtain a high volume fraction short carbon fiber doped SiC particle reinforced magnesium-based composite rod;

[0038] The inner cavity of the forming mold is cylindrical, and the ratio of the inner diameter of the forming mold to the diameter of the preform is 8:(5-7);

[0039] The steps of multi-directional capillary infiltration of the preform by the magnesium alloy solution under two-stage isothermal pressure are as follows: first stage: all-directional infiltration and pressure holding in the mold cavity for 3 minutes to 7 minutes under the conditions of temperature of 480°C to 520°C and pressure of 140kN to 230kN; second stage: capillary infiltration of all pores of the preform for 5 minutes to 10 minutes under the conditions of temperature of 480°C to 520°C and pressure of 140kN to 230kN; the hot pressing temperature of the first stage and the second stage is the same, the pressure of the first stage is lower than that of the second stage, and the pressure holding time of the first stage is lower than that of the second stage;

[0040] The isothermal multi-stage variable ratio rapid prototyping process comprises the following steps: performing a first extrusion at a temperature of 450° C. to 500° C., a pressure of 360 MPa to 480 MPa, and a speed of 0.05 mm / s to 0.01 mm / s, wherein the extrusion ratio of the first extrusion is 10:(1 to 3); and performing a second extrusion at a temperature of 450° C. to 500° C., a pressure of 480 MPa to 690 MPa, and a speed of 0.01 mm / s to 0.05 mm / s, wherein the extrusion ratio of the second extrusion is 8:(4 to 5).

[0041] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the particle size of the SiC particles in step 1 is 20 μm to 40 μm. Other aspects are the same as those of specific embodiment 1.

[0042] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that the length of the chopped carbon fibers in step 1 is 0.5 mm and the diameter is 7 μm to 10 μm. Other aspects are the same as specific embodiment 1 or 2.

[0043] Specific Embodiment 4: This embodiment differs from Specific Embodiments 1 to 3 in that the preparation method of the acidic aluminum phosphate described in step 1 is to thoroughly mix 85% by mass phosphoric acid and Al(OH)3 at an atomic ratio of P to Al of 23:1, and then heat at 150°C for 10 minutes. Other aspects are the same as Specific Embodiments 1 to 3.

[0044] Specific embodiment 5: This embodiment differs from specific embodiment 4 in that the magnesium alloy described in step 2 is AZ91. Other aspects are the same as specific embodiment 4.

[0045] The present invention is verified by the following test:

[0046] Experiment 1: This experiment is a preparation method for a three-dimensional interconnected porous high volume fraction chopped carbon fiber doped SiC particle reinforced magnesium-based composite rod, which is specifically carried out in the following steps:

[0047] 1. Preparation of a three-dimensional interconnected porous high volume fraction short carbon fiber doped silicon carbide particle dual-phase preform: the short carbon fiber and SiC particles are mixed together, and then deionized water is added, followed by a binder and a dispersant. The mixture is ultrasonically and electromagnetically stirred at 50°C for 60 minutes, poured into a pre-pressing mold for compression molding, freeze-dried at low temperature to remove moisture, and then subjected to differential temperature segmentation control and naturally cooled to room temperature to obtain a three-dimensional interconnected porous high volume fraction short carbon fiber doped silicon carbide particle dual-phase preformed cylinder;

[0048] The particle size of the SiC particles in step 1 is 20 μm to 40 μm;

[0049] The chopped carbon fibers in step 1 have a length of 0.5 mm and a diameter of 7 μm to 10 μm;

[0050] The volume ratio of the chopped carbon fibers to the SiC particles is 1:10;

[0051] The binder is acidic aluminum phosphate, wherein the atomic ratio of P element to Al element is 23:1. The preparation method of the acidic aluminum phosphate is: fully mix 85% by mass phosphoric acid and Al(OH)3 at an atomic ratio of P element to Al element of 23:1, and then heat at 150°C for 10 minutes.

[0052] The volume ratio of the binder to deionized water is 1:12, the volume ratio of the binder to the reinforcement is 2.5:15, and the reinforcement is a mixture of chopped carbon fibers and SiC particles;

[0053] The dispersant is polyacrylamide particles, the mass ratio of the reinforcement to the dispersant is 1:0.004, and the reinforcement is a mixture of chopped carbon fibers and SiC particles;

[0054] The process of differential temperature segmented control is as follows: heat preservation is performed at four temperature points of 200°C, 400°C, 600°C and 800°C in order from low to high, the heat preservation time at 200°C, 400°C and 600°C is 25 minutes, and the heat preservation time at 800°C is 180 minutes;

[0055] 2. The three-dimensional connected porous high volume fraction short carbon fiber doped SiC particle two-phase prefabricated cylinder obtained in step 1 is placed in a forming mold with the central axes of the two coinciding, and then the forming mold is preheated to 520°C, and a 700°C magnesium alloy solution is cast into the forming mold. Under two-stage isothermal pressurization, the magnesium alloy solution is multi-directionally coated on the preform for multi-directional graded capillary infiltration; then isothermal multi-stage variable ratio rapid forming is performed to obtain a high volume fraction short carbon fiber doped SiC particle reinforced magnesium-based composite rod;

[0056] The inner cavity of the forming mold is cylindrical, and the ratio of the inner diameter of the forming mold to the diameter of the preform is 4:3;

[0057] The magnesium alloy is AZ91, and its composition is: Mg mass fraction is 90.5wt.% to 89.5wt.%, Al mass fraction is 6.5wt.% to 7.5wt.%, and other trace elements;

[0058] The steps of multi-directional capillary infiltration of the preform by the magnesium alloy solution under two-stage isothermal pressure are as follows: first stage: all-directional infiltration and pressure holding in the mold cavity at a temperature of 520°C and a pressure of 170 kN for 6 minutes; second stage: capillary infiltration of all pores of the preform at a temperature of 520°C and a pressure of 230 kN for 9 minutes;

[0059] The isothermal multi-stage variable ratio rapid prototyping process comprises the following steps: performing a first extrusion at a temperature of 480°C, a pressure of 380 MPa, and a speed of 0.01 mm / s, with an extrusion ratio of 5:1; and performing a second extrusion at a temperature of 480°C, a pressure of 650 MPa, and a speed of 0.03 mm / s, with an extrusion ratio of 16:9.

[0060] Figure 1 This is a photo of the three-dimensional interconnected porous high volume fraction short carbon fiber doped silicon carbide particle two-phase prefabricated cylinder prepared in step 1 of experiment 1. It can be seen that the surface of the prepared preform is smooth without defects such as cracks and impurities.

[0061] Figure 2 This is a physical photograph of the product after multi-directional graded capillary infiltration of the preform by multi-directionally coating the preform with magnesium alloy solution under two-stage isothermal pressure in step 2 of experiment 1. The black part is the cast composite material obtained by fully infiltrating the magnesium alloy liquid into the preform structure, and the gray part is the uninfiltrated magnesium alloy around the preform. It can be seen that the cast composite material (black part) has no obvious defects, is dense inside, and has no bright alloy layer bands.

[0062] Figure 3 This is a schematic diagram of the forming mold in step 2 of experiment 1, where 1 is the magnesium alloy melt, 2 is the prefabricated cylinder prepared in step 1, 3 is the upper pad, 4 is the upper pressure head, 5 is the porous graphite pad, and 6 is the mold wall.

[0063] Figure 4 This is a real photo of the high volume fraction reinforced magnesium-based composite extruded rod prepared in Experiment 1. It can be seen that the surface of the extruded rod is smooth and there are no extrusion defects such as cracks and breakage.

[0064] Figure 5 Schematic diagram of the extrusion cup used for isothermal multi-stage variable ratio rapid prototyping in step 2 of experiment 1. No. 7 is the first extrusion area located at the top, with an extrusion ratio of 5:1; No. 8 is the second extrusion area located at the bottom, with an extrusion ratio of 16:9.

[0065] Experiment 2: This experiment was a comparative experiment. The difference from Experiment 1 was that in step 1, the chopped carbon fibers and SiC particles from step 1 were subjected to ultrasonic electromagnetic stirring at 90°C. The mixture was then kept at 300°C for 25 minutes, 500°C for 25 minutes, 700°C for 25 minutes, and finally at 900°C for 180 minutes. Through differential temperature control, a three-dimensional, interconnected, porous, and high-volume-fraction chopped carbon fiber-doped silicon carbide particle dual-phase preform was obtained. Other conditions were the same as Experiment 1.

[0066] The performance test of high volume fraction chopped carbon fiber doped SiC particles reinforced magnesium matrix composite rods was carried out at room temperature, and the engineering stress-engineering strain curve was obtained as follows: Figure 6 As shown, curve 9 is the high volume fraction chopped carbon fiber doped SiC particle reinforced magnesium matrix composite rod prepared in experiment 1, and curve 10 is the high volume fraction chopped carbon fiber doped SiC particle reinforced magnesium matrix composite rod prepared in experiment 2; Figure 6 It can be seen that the tensile strength of the composite rod prepared in Experiment 2 is 291 MPa and the modulus is 146 GPa; the tensile strength of the composite rod prepared in Experiment 1 reaches 322 MPa and the modulus is 156 GPa.

[0067] Figure 7 This is the low magnification OM image of the high volume fraction reinforced magnesium-based composite extruded rod prepared in Experiment 1. Figure 8 The high-magnification OM image of the high-volume fraction reinforced magnesium-based composite extruded rod prepared in Experiment 1 shows that the interface between the reinforcement and the matrix is ​​tightly bonded and the interface strength is high; the fibers break after extrusion and are distributed parallel to the extrusion direction, which greatly coordinates the extrusion deformation of the material and reduces stress concentration, particle breakage, and the initiation of microcracks.

[0068] Figure 9 This is a low-magnification SEM image of the tensile fracture of a high volume fraction reinforced magnesium-based composite extruded rod. Figure 10 This is a high-magnification SEM image of the tensile fracture of a high volume fraction reinforced magnesium-based composite extruded rod. It can be seen that the fracture is a typical brittle fracture. The debonding and breakage of most particles and fibers at the fracture, and the generation and expansion of microcracks are the main factors leading to material fracture.

[0069] Experiment 3: This experiment differs from Experiment 1 in that the volume ratio of the chopped carbon fibers to the SiC particles in step 1 is 3:17. Other conditions are the same as Experiment 1.

[0070] Experiment 4: This experiment was a comparative test. The difference from Experiment 1 was that in step 2, the three-dimensional interconnected, porous, high-volume-fraction chopped carbon fiber-doped SiC particle dual-phase preform obtained in Step 1 was preheated to 560°C, a 750°C magnesium alloy solution was cast into the mold, and then a single-stage multi-directional capillary infiltration process was performed at a pressure of 270 kN for 15 minutes. All other aspects were the same as Experiment 1.

[0071] The performance test of high volume fraction chopped carbon fiber doped SiC particles reinforced magnesium matrix composite rods was carried out at room temperature, and the engineering stress-engineering strain curve was obtained as follows: Figure 11 As shown, curve 11 is the high volume fraction chopped carbon fiber doped SiC particle reinforced magnesium matrix composite rod prepared in experiment 3, and curve 12 is the high volume fraction chopped carbon fiber doped SiC particle reinforced magnesium matrix composite rod prepared in experiment 4. Figure 11 It can be seen that in step 1 of experiment 3, the composite rod prepared by chopped carbon fiber and SiC particles with different volume fraction ratios has a tensile strength of 304 MPa and a modulus of 151 GPa; the composite rod prepared in experiment 4 has a tensile strength of 288 MPa and a modulus of 144 GPa.

Claims

1. A method for preparing a three-dimensional interconnected porous high volume fraction chopped carbon fiber doped SiC particle reinforced magnesium-based composite rod, characterized in that The preparation method of the three-dimensional connected porous high volume fraction chopped carbon fiber doped SiC particle reinforced magnesium matrix composite rod is carried out according to the following steps:

1. Preparation of a three-dimensional interconnected porous high volume fraction short carbon fiber doped silicon carbide particle dual-phase preform: the short carbon fiber and SiC particles are mixed together, and then deionized water is added, followed by a binder and a dispersant. The mixture is ultrasonically and electromagnetically stirred at 30°C to 60°C for 50min to 70min, poured into a pre-pressing mold for compression molding, freeze-dried at low temperature to remove moisture, and then subjected to differential temperature segmentation control and naturally cooled to room temperature to obtain a three-dimensional interconnected porous high volume fraction short carbon fiber doped silicon carbide particle dual-phase preformed cylinder; The volume ratio of the chopped carbon fibers to the SiC particles is 1:(4-19); The binder is acidic aluminum phosphate, wherein the atomic ratio of P element to Al element is 23:1; The volume ratio of the binder to deionized water is 1:(10-15), the volume ratio of the binder to the reinforcement is (1.5-3):15, and the reinforcement is a mixture of chopped carbon fibers and SiC particles; The dispersant is polyacrylamide particles, the mass ratio of the reinforcement to the dispersant is 1:(0.004-0.005), and the reinforcement is a mixture of chopped carbon fibers and SiC particles; The process of differential temperature segmented control is as follows: heat preservation is performed at four temperature points of 200°C, 400°C, 600°C and 800°C in order from low to high, the heat preservation time at 200°C, 400°C and 600°C is 25min to 30min, and the heat preservation time at 800°C is 180min to 190min; 2. The three-dimensional connected porous high volume fraction short carbon fiber doped SiC particle two-phase prefabricated cylinder obtained in step 1 is placed in a forming mold with the central axes of the two coinciding, and then the forming mold is preheated to 480°C to 520°C, and a 700°C magnesium alloy melt is cast into the forming mold. Under two-stage isothermal pressurization, the magnesium alloy melt multi-directionally covers the preform for multi-directional graded capillary infiltration; then, isothermal multi-stage variable ratio rapid forming is performed to obtain a high volume fraction short carbon fiber doped SiC particle reinforced magnesium-based composite rod; The inner cavity of the forming mold is cylindrical, and the ratio of the inner diameter of the forming mold to the diameter of the preform is 8:(5-7); The steps of multi-directional capillary infiltration of the preform by the magnesium alloy melt under two-stage isothermal pressure are as follows: first stage: full-directional infiltration and pressure holding in the mold cavity for 3 minutes to 7 minutes at a temperature of 480°C to 520°C and a pressure of 140kN to 230kN; Second stage: capillary infiltration of all pores of the preform is then carried out at a temperature of 480°C to 520°C and a pressure of 140kN to 230kN, with the pressure maintained for 5 to 10 minutes; the hot pressing temperature of the first and second stages is the same, the pressure of the first stage is lower than that of the second stage, and the holding time of the first stage is shorter than that of the second stage; The isothermal multi-stage variable ratio rapid prototyping process comprises the following steps: performing a first extrusion at a temperature of 450° C. to 500° C., a pressure of 360 MPa to 480 MPa, and a speed of 0.05 mm / s to 0.01 mm / s, wherein the extrusion ratio of the first extrusion is 10:(1 to 3); and performing a second extrusion at a temperature of 450° C. to 500° C., a pressure of 480 MPa to 690 MPa, and a speed of 0.01 mm / s to 0.05 mm / s, wherein the extrusion ratio of the second extrusion is 8:(4 to 5).

2. The method for preparing a three-dimensional interconnected porous high volume fraction chopped carbon fiber doped SiC particle reinforced magnesium-based composite rod according to claim 1, characterized in that The particle size of the SiC particles in step 1 is 20 μm to 40 μm.

3. The method for preparing a three-dimensional interconnected porous high volume fraction chopped carbon fiber doped SiC particle reinforced magnesium-based composite rod according to claim 1, characterized in that The chopped carbon fibers described in step 1 have a length of 0.5 mm and a diameter of 7 μm to 10 μm.

4. The method for preparing a three-dimensional interconnected porous high volume fraction chopped carbon fiber doped SiC particle reinforced magnesium-based composite rod according to claim 1, characterized in that The preparation method of the acidic aluminum phosphate described in step 1 is: fully mix 85% mass fraction of phosphoric acid and Al(OH)3 according to the atomic ratio of P element to Al element of 23:1, and then place it at 150°C and keep it for 10 minutes.

5. The method for preparing a three-dimensional interconnected porous high volume fraction chopped carbon fiber doped SiC particle reinforced magnesium-based composite rod according to claim 1, characterized in that The magnesium alloy described in step 2 is AZ91.

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