A gradient heterogeneous structure metal-ceramic composite material and a preparation method thereof

Abstract

The present invention relates to the technical field of ceramic composite materials, and discloses a gradient heterogeneous structure metal-ceramic composite material and a preparation method thereof. The composite material is composed of a shell, a core and a transition zone; the shell has a gradient network structure, the ceramic volume fraction is 90-30 vol% and gradually decreases from outside to inside, and the ceramic layer thickness gradually transitions from 150-100 μm to 50-20 μm; the core has a uniform layered structure, the ceramic volume fraction is 10-30 vol%, and the ceramic layer thickness is 10-40 μm; the transition zone has a hybrid composition of the shell and the core. The composite material prepared by the present invention has the advantages of high strength and hardness of the shell, wear resistance, good plastic toughness of the core, firm bonding in the transition zone, and both strength and toughness, and combines multiple performance advantages in a single material; the preparation process described in the present invention has the advantages of strong compositional and structural designability, flexibility and controllability, and strong universality.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic composite materials, and particularly relates to a gradient heterogeneous structure metal-ceramic composite material and a preparation method thereof. Background Art

[0002] With the progress of technology, the requirements for material properties in the fields of aerospace, rail transit, and electronic power are getting higher and higher. When the performance and functions of a single material are difficult to meet the usage requirements, an effective method is to combine materials with different properties to form a composite material whose performance and functions far exceed those of a single material. On the other hand, traditional composite materials are mostly uniformly compounded, while in actual applications, some components require materials with zone-selective properties. For example, for a grinding disc or grinding wheel, only the outer surface in contact with the object needs to have good hardness and wear resistance, while the core requires good plasticity and toughness for convenient processing and fitting. A completely uniform composition and structure not only greatly reduce the overall plasticity and toughness of the composite material, increase the processing difficulty, and raise the cost, but also is not conducive to the exertion of the synergistic effect of components and the positive response to the environment and functions to a great extent.

[0003] In the prior art, the solid-phase construction method based on powder metallurgy or the centrifugal casting method based on liquid-phase transfer is the most commonly used method for manufacturing composite materials with performance or functional gradients. For example, in the patent application No. 202011482872.8, the invention title is "A preparation method of an aluminum-based gradient electronic packaging composite material with a high silicon content", which discloses a preparation method of an aluminum-based gradient electronic packaging composite material with a high silicon content: an aluminum-based gradient electronic packaging composite material with a high silicon content is prepared by powder metallurgy combined with processes such as multi-stage charging cold pressing and stepwise hot pressing. However, the gradient structure formed by this solid-phase construction method based on powder metallurgy is discontinuous, and only laminated materials with simple shapes can be prepared. In addition, the laying process is cumbersome, the processes are complex, and it is difficult to precisely control the layer thickness. In the patent application No. 202011349171.7, the invention title is "A hub made of a high-entropy alloy-reinforced aluminum-based gradient material and a manufacturing method thereof", which discloses a hub made of a high-entropy alloy-reinforced aluminum-based gradient material and a manufacturing method thereof: 6061 aluminum alloy is heated to a molten state and injected into a centrifugal casting device, and at the same time, reinforcing phase AlNiFeCrCoTi high-entropy alloy powder particles are added to the molten 6061 alloy, so that the aluminum alloy hub blank formed by centrifugal casting has functional gradient characteristics, and then a gradient-distributed hub finished product is obtained through machining. However, this traditional centrifugal casting method cannot separate two materials with close densities, and can only prepare composite materials with a single structure, unable to realize the optimized design and configuration of components and structures, which hinders the exertion of material performance or functions. Summary of the Invention

[0004] The object of the present invention is to solve the drawbacks existing in the prior art, and to provide a gradient heterogeneous structure metal-ceramic composite material and a preparation method thereof.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A gradient heterogeneous structure metal-ceramic composite material, which is composed of a shell, a core and a transition zone;

[0007] The shell has a gradient network structure, the ceramic volume fraction is 90-30 vol% and decreases gradually from outside to inside, and the thickness of the ceramic layer gradually transitions from 150-100 μm to 50-20 μm;

[0008] The core has a uniform layered structure, the ceramic volume fraction is 10-30 vol%, and the thickness of the ceramic layer is 10-40 μm;

[0009] The transition zone has a hybrid composition of the shell and the core, presenting a complex layered or layer-network composite structure, the ceramic volume fraction is 20-50 vol%, and the thickness of the ceramic layer is 20-80 μm.

[0010] Preferably, the ceramic material is one or a mixture of more of alumina, zirconia, mullite, silicon carbide, boron carbide, titanium carbide, silicon nitride; the powder diameter of the ceramic material is 100 nm - 30 μm; the metal material is one of pure Al and Al alloys.

[0011] The preparation method of the gradient heterogeneous structure metal-ceramic composite material includes the following steps:

[0012] Step 1: Mix ceramic powder A and ceramic powder B separately with deionized water, add dispersants respectively, and then ball mill and degas under vacuum to obtain uniformly dispersed aqueous ceramic slurries A and B; among them, ceramic slurry A is used to prepare the shell of the composite material, and ceramic slurry B is used to prepare the inner core of the composite material;

[0013] Step 2: Prepare an additive for adjusting the pore morphology, and add the prepared additive into ceramic slurry A, and ball mill and mix evenly;

[0014] Step 3: Inject ceramic slurry A into a mold, seal both ends of the mold, perform high-speed centrifugal rotation at room temperature, then immerse the aluminum rod at the bottom of the mold in a freezing medium, and continue to rotate at low temperature to obtain a hollow frozen shell;

[0015] Step 4: Heat a metal rod and make it contact with the hollow straight circular surface inside the frozen shell to melt and remove the ice layer. After withdrawing the metal rod, a regular inner cylindrical surface is formed;

[0016] Step 5: Fill the inner cylindrical part of the freezing shell with ceramic slurry B, and immerse the aluminum rod at the bottom of the mold in the freezing medium again to obtain a complete frozen preform;

[0017] Step 6: Vacuum-dry the frozen preform at a low temperature to sublime and remove the ice crystals in the preform, obtaining a porous preform;

[0018] Step 7: Debind and sinter the dried porous preform at a high temperature to obtain a porous ceramic body;

[0019] Step 8: Infiltrate and inject the liquid metal into the pores of the porous ceramic body under vacuum-pressure conditions to obtain a gradient heterogeneous structure metal-ceramic composite.

[0020] Preferably, in Step 1, the ceramic volume fraction in the water-based ceramic slurry A is 25-40 vol.%, and the dispersant added to the water-based ceramic slurry A accounts for 1-4 wt.% of the mass of the ceramic powder in the water-based ceramic slurry A;

[0021] The ceramic volume fraction in the water-based ceramic slurry B is 10-30 vol.%, and the dispersant added to the water-based ceramic slurry B accounts for 0.5-2 wt.% of the mass of the ceramic powder in the water-based ceramic slurry B;

[0022] The dispersant is one or a mixture of two of ammonium polyacrylate, ammonium polymethacrylate, sodium polymethacrylate, and sodium carboxymethyl cellulose;

[0023] The ball milling duration is 10-20 h, and the vacuum defoaming duration is 10-30 min.

[0024] Preferably, in Step 2, the additive is one or a mixture of gelatin, pectin, agarose, chitosan, and sodium alginate, and the content of the additive added to the water-based ceramic slurry A accounts for 2-6 wt.% of the mass of deionized water.

[0025] Preferably, in Step 3, the injection amount of the ceramic slurry A accounts for 20-80 vol.% of the entire mold volume; the centrifugal speed is 1000-3000 rpm, and the room temperature centrifugal rotation duration is 0.5 h; the freezing temperature is -10 to -90 °C, and the low-temperature freezing centrifugal rotation duration is 0.5-1 h.

[0026] Preferably, in Step 4, the outer diameter of the metal rod is greater than the diameter of the hollow inner circular surface of the freezing shell, the length is greater than the mold height, the heating temperature is 40-60 °C, and the contact duration with the hollow inner circular surface is 1-3 min.

[0027] Preferably, in Step 5, the freezing process is a freezing temperature of -10 to -50 °C, and the freezing duration is 0.5-1 h;

[0028] The low-temperature vacuum drying parameters described in Step 6 are: temperature -50°C, vacuum degree 10 Pa, and drying duration 48 - 72 h.

[0029] Preferably, the degreasing process described in Step 7 is: heating to 250°C at a rate of 5°C / min and holding for 0.5 h; heating from 250°C to 600°C at a rate of 1°C / min and holding for 0.5 h; the high-temperature sintering process is: after degreasing, heating from 600°C to 1300 - 1600°C at a rate of 5°C / min, holding for 2 h, and then cooling at a rate of 5°C / min.

[0030] Preferably, the impregnation process described in Step 8 is: placing the ceramic green body and the metal in an alumina crucible, then putting it into an impregnation furnace, evacuating to below 10 Pa at room temperature, heating to 700 - 900°C at a rate of 5°C / min, introducing high-purity argon gas into the furnace to 2 - 5 MPa, holding the pressure for 3 - 5 min, then cooling to below the melting point of the metal at a rate of 5°C / min, releasing the pressure, and cooling with the furnace to room temperature.

[0031] The beneficial effects of the present invention are:

[0032] 1. The composite material prepared by the present invention has the advantages of high shell strength and hardness, wear resistance, good plastic toughness in the core, firm bonding in the transition zone, and combines multiple performance advantages in a single material.

[0033] 2. The preparation process described in the present invention has the advantages of strong component and structure designability, flexibility and controllability, and strong universality.

[0034] 3. The preparation process described in the present invention separates the preparation of the ceramic preform and the metal infiltration composite, greatly simplifies the equipment requirements, and reduces the cost investment. Description of the Drawings

[0035] Figure 1 is the process flow chart of the preparation of the gradient heterogeneous structure metal-ceramic composite material described in the present invention;

[0036] Figure 2 are the photos of the ceramic skeleton and the composite material obtained in Example 1 of the present invention;

[0037] Figure 3 are the photos of the microstructures of regions I - V of the composite material in Example 1 of the present invention;

[0038] Figure 4 is the flexural stress-strain curve of regions I - V of the composite material in Example 1 of the present invention;

[0039] Figure 5 are the photos of the microstructures of regions I - V of the composite material in Example 2 of the present invention. Detailed Embodiments

[0040] Next, in combination with the accompanying drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0041] A gradient heterogeneous structure metal-ceramic composite material, the flow chart of its preparation method is as Figure 1 shown, and the specific steps are as follows:

[0042] Step 1: Mix ceramic powder A and ceramic powder B separately with deionized water, add appropriate amounts of dispersants respectively, then ball mill for 10-20 h, and remove bubbles under vacuum for 10-30 min to obtain uniformly dispersed aqueous ceramic slurries A and B; among them, ceramic slurry A is used to prepare the composite material shell, and ceramic slurry B is used to prepare the composite material core; the types of ceramics A and B can be the same or different;

[0043] Among them, the ceramic volume fraction in ceramic slurry A is 25-40 vol.%, and the dispersant is 1-4 wt.% of the mass of the ceramic powder; the ceramic volume fraction in ceramic slurry B is 10-30 vol.%, and the dispersant is 0.5-2 wt.% of the mass of the ceramic powder; the dispersant is one or a mixture of two of ammonium polyacrylate, ammonium polymethacrylate, sodium polymethacrylate or sodium carboxymethylcellulose;

[0044] Step 2: Prepare an additive for adjusting the pore morphology in a certain proportion, and add it to ceramic slurry A, and mix evenly after ball milling; the additive is one or a mixture of several of gelatin, pectin, agarose, chitosan, sodium alginate, and the content of the additive accounts for 2-6 wt.% of the mass of deionized water;

[0045] Step 3: Inject ceramic slurry A accounting for 20-80 vol.% of the mold volume into a nylon or polytetrafluoroethylene mold, seal both ends, and perform centrifugal rotation at room temperature, with a rotation speed of 1000-3000 rpm. After rotating for 0.5 h, immerse the aluminum rod at the bottom of the mold into a liquid nitrogen pool or other freezing medium, and control the temperature of the proximal end face of the aluminum rod in contact with the slurry to be -10 to -90 °C by adjusting the immersion depth of the aluminum rod into the freezing liquid surface. After continuing to rotate at low temperature for 0.5-1 h, a hollow frozen shell is obtained;

[0046] Step 4: Heat a metal rod with appropriate dimensions to 40-60 °C, contact the hollow straight circular surface inside the frozen shell for 1-3 min to melt and remove the ice layer, and then withdraw the metal rod to form a regular inner cylindrical surface. The metal rod is preferably a copper rod, with an outer diameter slightly larger than the diameter of the hollow inner circular surface of the frozen shell and a length slightly larger than the height of the mold;

[0047] Step 5: Rapidly fill the inner cylindrical part of the freezing shell with ceramic slurry B. Immerse the aluminum rod at the bottom of the mold into a liquid nitrogen bath or other freezing medium again, and control the freezing temperature of the proximal end face of the aluminum rod in contact with the slurry to be -10 to -50 °C. Keep it for 0.5 to 1 h to obtain a complete frozen preform;

[0048] Step 6: Vacuum dry the frozen preform at a temperature of -50 °C and a vacuum degree of 10 Pa for 48 to 72 h to sublime and remove the ice crystals in the preform, obtaining a porous preform;

[0049] Step 7: Debind and sinter the dried porous preform at a high temperature in a suitable atmosphere (air or argon) to obtain a porous ceramic body. The debinding process is as follows: Heat to 250 °C at a rate of 5 °C / min and keep it for 0.5 h; Heat from 250 °C to 600 °C at a rate of 1 °C / min and keep it for 0.5 h. The high-temperature sintering process is as follows: After debinding, heat from 600 °C to 1300 - 1600 °C at a rate of 5 °C / min, keep it for 2 h, and then cool at a rate of 5 °C / min;

[0050] Step 8: Infiltrate and inject liquid metal into the pores of the porous ceramic body under vacuum-pressure conditions to obtain a gradient heterogeneous structure metal-ceramic composite. The infiltration process is as follows: Place the ceramic body and the metal in an alumina crucible, then place it in an infiltration furnace. Evacuate to below 10 Pa at room temperature, heat to 700 - 900 °C at a rate of 5 °C / min, introduce high-purity argon gas into the furnace to 2 - 5 MPa, keep the temperature and pressure for 3 - 5 min, then cool to below the melting point of the metal at a rate of 5 °C / min, relieve the pressure, and cool with the furnace to room temperature.

[0051] The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to the following embodiments.

[0052] Example 1:

[0053] A gradient heterogeneous network / layer structure pure aluminum / (zirconia-alumina) composite material, and its preparation method includes the following steps:

[0054] Step 1: Mix zirconia powder (D50 = 1.2 μm, purity 99.9%), a dispersant (ammonium polyacrylate, accounting for 2 wt.% of the mass of the ceramic powder), and deionized water to prepare a zirconia ceramic slurry with a solid content of 40 vol.%; Mix alumina powder (D50 = 5 μm, purity 99.7%), a dispersant (sodium polymethacrylate, accounting for 1 wt.% of the mass of the ceramic powder), and deionized water to prepare an alumina ceramic slurry with a solid content of 15 vol.%. After ball milling (rotation speed of 100 r / min, ball milling for 12 h) and vacuum defoaming for 20 min, a water-based zirconia ceramic slurry for the shell and a water-based alumina ceramic slurry for the core are obtained respectively;

[0055] Step 2: Add gelatin (purity 99.9%) in an amount of 5 wt.% of the mass of deionized water to the zirconia ceramic slurry as a regulator for forming a network structure, and mix evenly after ball milling for 5 hours;

[0056] Step 3: Combine a nylon mold (size of φ30×40mm) with an aluminum rod, and then inject the uniformly mixed zirconium oxide slurry into the nylon mold, the injection amount accounting for 80vol.% of the entire mold volume, close the top of the mold, and pre-rotate at 2000rpm for 0.5h at room temperature so that the zirconium oxide particles in the slurry form a radial gradient distribution under the action of the centrifugal field; later, extend the bottom aluminum rod into the liquid nitrogen pool, adjust the insertion depth, and make the temperature of the proximal end surface of the aluminum rod contacting the slurry be -50°C, and continue to rotate the slurry under high-speed centrifugation for 0.5h to complete the directional solidification, and the gradient distribution state of the ceramic particles is frozen and retained to obtain a frozen shell with an inner pore diameter of φ8mm and a gradient mesh structure;

[0057] Step 4: Heat a copper rod with an outer diameter of φ10 mm and a length of 50 mm to 50°C and place it in contact with the hollow straight circular surface in the frozen shell for 1 minute to melt and remove the ice layer. After the copper rod is pulled out, a regular inner cylindrical surface is formed;

[0058] Step 5: quickly fill the inner cylindrical part of the freezing shell with alumina ceramic slurry, immerse the aluminum rod at the bottom of the mold into the liquid nitrogen pool again, control the freezing temperature of the proximal end surface of the aluminum rod contacting the slurry to -20°C, and keep it for 1 hour to obtain a complete frozen preform;

[0059] Step 6: vacuum drying the frozen preform at a temperature of -50°C and a vacuum degree of 10Pa for 48 hours to sublimate and remove ice crystals in the preform;

[0060] Step 7: Debindering and sintering the dried porous preform in air. The debinding process is: heating to 250℃ at 5℃ / min, keeping the temperature for 0.5h; heating from 250℃ to 600℃ at 1℃ / min, keeping the temperature for 0.5h; the sintering process is: heating from 600℃ to 1400℃ at 5℃ / min after debinding, keeping the temperature for 2h, and then cooling at 5℃ / min; the obtained porous ceramic body is as follows Figure 2 (a)

[0061] Step 8: Place the porous ceramic body and pure Al ingot into an alumina crucible in turn, and then put it into an infiltration furnace. Evacuate to below 10Pa at room temperature, heat to 850℃ at 5℃ / min, introduce high-purity argon into the furnace to 3MPa, keep the temperature and pressure for 5 minutes, then cool to 600℃ at 5℃ / min, release the pressure, and cool to room temperature with the furnace.

[0062] The composite material prepared in Example 1 was observed, and the macroscopic structure of the composite material on one quarter surface was as follows: Figure 2(b); it is radially divided into five regions (I-V), and the microstructure of each region is as follows Figure 3 shown, where regions I-III are the gradient networked shell, region IV is the transition zone, and region V is the uniform layered core; samples are taken axially from regions I-V of the composite material for a three-point bending test, and the bending stress-strain curve is as follows Figure 4 shown, where the shell part (regions I-III) has high strength and a gradient change, the transition zone (region IV) has both strength and toughness, and the core (region V) has good toughness.

[0063] Example 2:

[0064] A gradient heterogeneous network / layer structure 6061 aluminum / (3YSZ-aluminum oxide) composite material, and its preparation method includes the following steps:

[0065] Mix 3YSZ powder (D50 = 0.8 μm, purity 99.9%), a dispersant (ammonium polyacrylate, 2 wt.% of the mass of the ceramic powder), and deionized water to prepare a 3YSZ ceramic slurry with a solid content of 30 vol.%; mix alumina powder (D50 = 5 μm, purity 99.7%), a dispersant (sodium polymethacrylate, 1 wt.% of the mass of the ceramic powder), and deionized water to prepare an alumina ceramic slurry with a solid content of 15 vol.%; add agarose (purity 99.9%) accounting for 2 wt.% of the mass of deionized water to the 3YSZ ceramic slurry as an additive for adjusting pore morphology, and mix evenly after ball milling for 5 h; combine a nylon mold (size φ30×40 mm) with an aluminum rod, then inject the uniformly mixed 3YSZ slurry into the nylon mold, seal the top of the mold, and pre-rotate it at a rate of 1600 rpm at room temperature for 0.5 h. Later, insert the aluminum rod at the bottom into a liquid nitrogen pool so that the temperature of the near-end face of the aluminum rod contacting the slurry is -70 °C, and keep the aluminum rod in the liquid nitrogen for 0.5 h to obtain a hollow frozen shell with a gradient network structure; heat a copper rod with an outer diameter of φ10 mm and a length of 50 mm to 50 °C, contact it with the hollow straight circular surface inside the frozen shell for 1 min to melt and remove the ice layer, and after pulling out the copper rod, form a regular inner cylindrical surface; quickly fill the inner cylindrical part of the frozen shell with the alumina ceramic slurry, and immerse the aluminum rod at the bottom of the mold into the liquid nitrogen pool again, control the freezing temperature of the near-end face of the aluminum rod contacting the slurry to be -10 °C, and keep it static for 1 h to obtain a complete frozen preform; vacuum-dry the frozen preform at a temperature of -50 °C and a vacuum degree of 10 Pa for 48 h to sublimate and remove the ice crystals in the preform; sinter the freeze-dried porous preform in air for debinding to obtain a porous ceramic green body; the debinding process is: raise the temperature to 250 °C at a rate of 5 °C / min and hold for 0.5 h; raise the temperature from 250 °C to 600 °C at a rate of 1 °C / min and hold for 0.5 h; the high-temperature sintering process is: after debinding, raise the temperature from 600 °C to 1500 °C at a rate of 5 °C / min and hold for 2 h, and then cool at a rate of 5 °C / min; put the porous ceramic green body and 6061Al ingot into an alumina crucible in turn, then put it into an infiltration furnace, evacuate to below 10 Pa at room temperature, heat to 800 °C at a rate of 5 °C / min, introduce high-purity argon gas into the furnace to 3 MPa, hold the pressure for 5 min, then cool to 600 °C at a rate of 5 °C / min, release the pressure, and cool with the furnace to room temperature.

[0066] The microstructure of regions I-V of composite material I in Example 2 of the present invention is as Figure 5 shown, where regions I-III are the gradient network shell, region IV is the transition zone, and region V is the uniform layered core.

[0067] The present invention drives ceramic particles to form a continuous gradient distribution in a solvent by means of centrifugal action, and obtains an ordered orientation arrangement of crystals through directional freezing; constructs a network structure by reasonable selection of additives; and forms a network / layered composite structure by means of melting and then refreezing. By controlling the slurry components, centrifugation process, freezing parameters, etc., the structural parameters of the frozen green body can be regulated in a large scale range from sub-microns to hundreds of microns, so as to prepare a metal-ceramic composite material with a bionic configuration, so as to fully exert the synergistic effect of the components and the positive response to the environment and functions.

[0068] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A gradient heterogeneous structure metal-ceramic composite material, characterized in that, The composite material is composed of a shell, a core, and a transition zone; The shell has a gradient network structure, with a ceramic volume fraction of 90 - 30 vol% and a gradient decrease from the outside to the inside, and the thickness of the ceramic layer gradually transitions from 150 - 100 μm to 50 - 20 μm; The core has a uniform layered structure, with a ceramic volume fraction of 10 - 30 vol%, and the thickness of the ceramic layer is 10 - 40 μm; The transition zone has a hybrid composition of the shell and the core, with a ceramic volume fraction of 20 - 50 vol%, and the thickness of the ceramic layer is 20 - 80 μm.

2. A gradient heterogeneous structure metal-ceramic composite material according to claim 1, characterized in that, The ceramic material is one or a mixture of more than one of alumina, zirconia, mullite, silicon carbide, boron carbide, titanium carbide, and silicon nitride; the powder diameter of the ceramic material is 100 nm - 30 μm; the metal material is one of pure Al and Al alloys.

3. The preparation method of a gradient heterogeneous structure metal-ceramic composite material according to any one of claims 1-2, characterized in that, It includes the following steps: Step 1: Separately mix ceramic powder A and ceramic powder B with deionized water, and separately add a dispersant, then ball mill and remove bubbles under vacuum to obtain uniformly dispersed water-based ceramic slurries A and B; among them, ceramic slurry A is used to prepare the shell of the composite material, and ceramic slurry B is used to prepare the inner core of the composite material; Step 2: Prepare an additive for adjusting the pore morphology, and add the prepared additive to ceramic slurry A, and ball mill and mix evenly; Step 3: Inject ceramic slurry A into a mold, seal both ends of the mold, perform high-speed centrifugal rotation at room temperature, then immerse the aluminum rod at the bottom of the mold in a cryogenic medium, and continue to rotate at low temperature to obtain a hollow frozen shell; Step 4: Heat with a metal rod and contact the hollow straight circular surface inside the frozen shell to melt and remove the ice layer. After pulling out the metal rod, a regular inner cylindrical surface is formed; Step 5: Fill the inner cylindrical part of the frozen shell with ceramic slurry B, and immerse the aluminum rod at the bottom of the mold in the cryogenic medium again to obtain a complete frozen preform; Step 6: Vacuum dry the frozen preform at low temperature to sublime and remove the ice crystals in the preform to obtain a porous preform; Step 7: Debind and sinter the dried porous preform at high temperature to obtain a porous ceramic body; Step 8: Infiltrate and inject liquid metal into the pores of the porous ceramic body under vacuum-pressure conditions to obtain a gradient heterogeneous structure metal-ceramic composite material.

4. The preparation method of a gradient heterogeneous structure metal-ceramic composite material according to claim 3, characterized in that, In step 1, the ceramic volume fraction in water-based ceramic slurry A is 25 - 40 vol.%, and the dispersant added to water-based ceramic slurry A accounts for 1 - 4 wt.% of the mass of the ceramic powder in water-based ceramic slurry A; The ceramic volume fraction in water-based ceramic slurry B is 10 - 30 vol.%, and the dispersant added to water-based ceramic slurry B accounts for 0.5 - 2 wt.% of the mass of the ceramic powder in water-based ceramic slurry B; The dispersant is one or a mixture of two of ammonium polyacrylate, ammonium polymethacrylate, sodium polymethacrylate, and sodium carboxymethyl cellulose; The ball milling duration is 10 - 20 h, and the vacuum degassing duration is 10 - 30 min.

5. The preparation method of a gradient heterogeneous structure metal-ceramic composite material according to claim 3, characterized in that, In step 2, the additive is one or a mixture of more than one of gelatin, pectin, agarose, chitosan, and sodium alginate, and the content of the additive added to water-based ceramic slurry A accounts for 2 - 6 wt.% of the mass of deionized water.

6. The preparation method of a gradient heterogeneous structure metal-ceramic composite material according to claim 3, characterized in that, The injection amount of the ceramic slurry A described in step 3 accounts for 20 - 80 vol.% of the entire mold volume; the centrifugal speed is 1000 - 3000 rpm, and the room temperature centrifugal rotation duration is 0.5 h; the freezing temperature is -10 - -90 °C, and the low-temperature freezing centrifugal rotation duration is 0.5 - 1 h.

7. The preparation method of a gradient heterogeneous structure metal-ceramic composite material according to claim 3, characterized in that, The outer diameter of the metal rod described in step 4 is larger than the diameter of the hollow inner circular surface of the freezing shell, the length is greater than the mold height, the heating temperature is 40 - 60 °C, and the contact duration with the hollow inner circular surface is 1 - 3 min.

8. The preparation method of a gradient heterogeneous structure metal-ceramic composite material according to claim 3, characterized in that, The freezing process described in step 5 is: the freezing temperature is -10 - -50 °C, and the freezing duration is 0.5 - 1 h; The low-temperature vacuum drying parameters described in step 6 are: temperature -50 °C, vacuum degree 10 Pa, and drying duration 48 - 72 h.

9. The preparation method of a gradient heterogeneous structure metal-ceramic composite material according to claim 3, characterized in that, The debinding process described in step 7 is: rising to 250 °C at a rate of 5 °C / min and holding for 0.5 h; rising from 250 °C to 600 °C at a rate of 1 °C / min and holding for 0.5 h; the high-temperature sintering process is: after debinding, rising from 600 °C to 1300 - 1600 °C at a rate of 5 °C / min, holding for 2 h, and then cooling at a rate of 5 °C / min.

10. The preparation method of a gradient heterogeneous structure metal-ceramic composite material according to claim 3, wherein, The infiltration process described in step 8 is: placing the ceramic green body and the metal in an alumina crucible, then putting it into an infiltration furnace, evacuating to below 10 Pa at room temperature, heating to 700 - 900 °C at a rate of 5 °C / min, introducing high-purity argon gas into the furnace to 2 - 5 MPa, holding the pressure for 3 - 5 min, then cooling to below the melting point of the metal at a rate of 5 °C / min, relieving the pressure, and cooling with the furnace to room temperature.

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