A method for preparing ceramic-sphere-containing aluminum foam based on a strong magnetic field

Abstract

The application discloses a preparation method of ceramic ball-containing closed-cell foam aluminum based on a strong magnetic field. The method ensures the uniformity of the distribution of the composite material through the action of the strong magnetic field on molten aluminum liquid and ceramic balls. The preparation method effectively inhibits the sedimentation movement of the ceramic balls in the molten aluminum liquid due to the density difference in the strong magnetic field environment, thereby preparing a solid ceramic ball closed-cell foam aluminum-based composite material with uniform distribution. The closed-cell foam aluminum composite material containing solid ceramic balls has the characteristics of light weight and high specific strength in structure, and can fully play the energy dissipation mechanism of ceramic ball fragmentation and the excellent properties of closed-cell foam metal, such as small density, energy absorption and anti-impact, and plays an important role in the fields of chemical industry, machinery, building, transportation and armored protection.

Description

Technical Field

[0001] The invention belongs to the technical field of composite materials and relates to a method for preparing foamed aluminum containing ceramic balls based on a strong magnetic field. Background Art

[0002] Aluminum foam is a porous metal foam material with excellent properties such as light weight, high specific stiffness, sound insulation, noise reduction, energy absorption, and impact resistance. It is widely used in a variety of fields, including weapons engineering and mechanical construction. Ceramics, with their high hardness and low density, are widely used in protective armor due to their ability to dissipate energy when shattered by impact. Strong magnetic fields, generally referring to those above 5T, can alter the dynamic viscosity of fluids. These fields are also widely used in other fields, including industry and agriculture. By combining a metal phase with ceramic particles, the application of ceramic particles and metal matrices is expanded, which has significant implications for the field of armor protection.

[0003] Currently, most of the foam composite materials containing ceramic balls are hollow ceramic balls and open-pore aluminum foam materials. The uneven distribution of ceramic balls and the connection of open pores have greatly weakened the energy dissipation capacity of the material in the field of armor protection.

[0004] Wang Lucai, Wu Jianguo, Wang Fang, You Xiaohong. Foam aluminum alloy reinforced with ceramic balls and its preparation method (application number: 200910075521.2) describes a preparation method in which ceramic balls are mixed with saturated salt water, pressurized, heated and dried, and finally washed with running water to remove salt particles. The patent found through experimental verification that the sample collapsed and foam aluminum material containing ceramic balls could not be prepared.

[0005] Cui Dongbo, Chen Xiang. A solid ball foam aluminum composite material and its preparation method (application number: 202110110055.8) describes a preparation method of an aluminum-based ceramic composite material. The composite material prepared by uniform stirring and dispersion in this patent cannot guarantee the uniform distribution of ceramic balls in the aluminum matrix.

[0006] In summary, the existing technology has problems such as uneven internal distribution and material collapse of the foam aluminum composite material containing ceramic balls, and does not involve a method for preparing the foam aluminum composite material containing ceramic balls using a strong magnetic field. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for preparing foam aluminum containing ceramic balls based on a strong magnetic field. Through the influence of the strong magnetic field on different materials, ceramic balls and closed-cell foam aluminum materials are combined together to improve the energy absorption capacity of the materials.

[0008] The technical solution adopted in the present invention is:

[0009] A method for preparing foamed aluminum containing ceramic balls in a strong magnetic field ensures the uniformity of the prepared composite material by the action of the strong magnetic field on molten aluminum and ceramic balls.

[0010] The specific steps include:

[0011] 1) Place an alumina substrate at the bottom of the hollow column;

[0012] 2) Placing a steel mesh on the alumina substrate;

[0013] 3) Filling the hollow tube with aluminum blocks or alumina powder and ceramic balls according to the required porosity and internal ceramic ball distribution;

[0014] 4) Place a layer of steel mesh on top of the composite material;

[0015] 5) Open the plunger and pour in the molten aluminum liquid. After pouring, close the plunger;

[0016] 6) Turn on the superconducting strong magnetic field device to generate a transverse static magnetic field and adjust the magnetic field strength;

[0017] 7) Turn on the heater, control the temperature to 1200°C via a thermocouple, and introduce argon gas through the vent;

[0018] 8) After heat preservation and cooling, a foamed aluminum composite material containing ceramic balls is obtained.

[0019] Furthermore, the magnetic field strength can be adjusted within a range of 10-12T.

[0020] Furthermore, the ceramic ball is one or more of silicon carbide, aluminum oxide, zirconium oxide, and boron carbide ceramics.

[0021] Furthermore, the metallic aluminum is one or more of metallic aluminum blocks and aluminum powders.

[0022] Furthermore, the diameter of the ceramic balls ranges from 3 to 10 mm, and the ceramic balls account for 30% to 50% of the total volume of the composite material.

[0023] Furthermore, the direction of the enhanced magnetic field is horizontal, and the flow direction of the molten aluminum liquid is vertical.

[0024] Furthermore, after the composite material is cooled along with the device, the aluminum oxide substrate and the steel mesh at the bottom are removed to obtain a foam aluminum composite material containing ceramic balls.

[0025] The present invention provides a device for preparing foamed aluminum containing ceramic balls based on a strong magnetic field, the device comprising

[0026] Hollow pipe string;

[0027] a plunger that cooperates with the hollow tubular column;

[0028] The hollow pipe column is provided with an air guide hole, a vent, a heater and an inserted thermocouple;

[0029] The inner wall of the hollow column is coated with graphite coating, the bottom is supported by an alumina substrate; the middle is filled with ceramic balls and metal aluminum, and a steel mesh is set on the top to separate the molten aluminum liquid.

[0030] In addition, a strong magnetic field is set outside the device.

[0031] The present invention has the following characteristics:

[0032] The entire device is in a strong magnetic field;

[0033] The ceramic balls and metallic aluminum are separated from the molten aluminum and alumina substrate by a steel mesh.

[0034] The graphite coating is evenly applied to the inner wall of the hollow tube.

[0035] The plunger cooperates with the hollow tubing column.

[0036] The present invention has the following advantages:

[0037] 1. The present invention provides a method for preparing foamed aluminum containing ceramic balls, which can meet the required porosity and other structural parameters by presetting the number and distribution of ceramic balls;

[0038] 2. The present invention provides a method for preparing foam aluminum containing ceramic balls, which can prepare uniformly distributed ceramic balls and closed-cell foam aluminum composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of the structure of a device for preparing foam aluminum containing ceramic balls based on a strong magnetic field.

[0040] In the accompanying drawings: 1—plunger; 2—air guide hole; 3—graphite coating; 4—steel mesh; 5—metal aluminum; 6—thermocouple; 7—heater; 8—hollow tube; 9—vent; 10—molten aluminum; 11—ceramic ball; 12—strong magnetic field; 13—alumina substrate.

[0041] Figure 2 This is a process flow chart of a device for preparing foamed aluminum containing ceramic balls based on a strong magnetic field. DETAILED DESCRIPTION

[0042] The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

[0043] The present invention provides a method for preparing foamed aluminum containing ceramic balls based on a strong magnetic field, such as Figure 1 As shown, the device used for preparation includes a plunger, a gas guide hole, a graphite coating, a steel mesh, metal aluminum, a thermocouple, a heater, a hollow tube column, a vent, molten aluminum liquid, a ceramic ball, a strong magnetic field and an alumina substrate.

[0044] The working principle of the present invention is:

[0045] Since the density of the ceramic ball is greater than that of the metallic aluminum liquid, the ceramic ball tends to sink in the metallic aluminum liquid. By applying a high-intensity magnetic field, the longitudinal movement of the molten aluminum liquid cuts the magnetic flux lines to generate a circular current. The interaction between the high-intensity magnetic field and the induced current generates an electromagnetic force. Since the ceramic ball has poor electrical conductivity, while the molten aluminum liquid has good electrical conductivity, the ceramic ball will be subjected to an electromagnetic squeezing force in the opposite direction of the electromagnetic force. In the molten aluminum liquid, the resultant force on the ceramic ball is:

[0046] F=F fv +F fp +F L +F p -F s

[0047] Among them, F fv is the viscous resistance of the ceramic ball, F fp F is the pressure difference resistance of the ceramic ball. L is the buoyancy of the ceramic ball, F p is the electromagnetic extrusion force on the ceramic ball, F g is the gravity acting on the ceramic ball.

[0048] The expression of viscous resistance is:

[0049] F fv =4πrη B v

[0050] Where v is the final velocity of the ceramic ball, r is the radius of the ceramic ball, η B is the dynamic viscosity of molten aluminum.

[0051] The expression of pressure differential resistance is:

[0052] F fp =2πrη B v

[0053] The expression for buoyancy is:

[0054]

[0055] Where ρ is the density of molten aluminum and g is the acceleration due to gravity.

[0056] Since ceramics are non-metallic particles and their electrical conductivity tends to zero, the electromagnetic extrusion force they experience is:

[0057]

[0058] Where f is the frequency of the electromagnetic field, σ is the electrical conductivity of the molten aluminum, μ is the magnetic permeability of the molten aluminum, and B0 is the magnetic induction intensity.

[0059] For molten aluminum, the expression for the viscosity of the metal melt under a strong magnetic field is:

[0060] η B =η+kB 2

[0061] Where η B is the effective viscosity of the melt, η is the dynamic viscosity of the molten aluminum liquid, and the coefficient k is:

[0062]

[0063] Where Ha is:

[0064]

[0065] The expression for gravity is:

[0066]

[0067] Where ρ1 is the density of the ceramic ball.

[0068] Among them, the dynamic viscosity of molten aluminum liquid η=4.5×10 -3 Pa·S, density of molten aluminum liquid ρ=2.37×10 3 kg / m 3 , the electrical conductivity of molten aluminum liquid σ=4.1322×10 6 Ω -1 m -1 , the magnetic permeability of molten aluminum is μ=4π×10 -7 H / m, ceramic ball density ρ1=3.15×10 3 kg / m 3 , electromagnetic field frequency f = 20kHz.

[0069] By simultaneous calculation, such as Figure 2 When the selected magnetic field strength is between 10-12T and the diameter of the ceramic ball is in the range of 3-10mm, since the viscosity of the metal melt in the magnetic field is proportional to the strength of the magnetic field, by increasing the magnetic field strength, the viscosity of the metal melt is increased, thereby increasing the viscous resistance to movement of the ceramic particles, resulting in the ceramic ball's sedimentation movement being not obvious, which meets the design requirements.

[0070] In summary, by introducing a strong magnetic field, the sedimentation movement of ceramic balls in the molten aluminum due to density differences was effectively suppressed.

[0071] Example 1

[0072] A method for preparing foamed aluminum containing ceramic balls based on a strong magnetic field comprises the following steps:

[0073] Graphite coating is evenly applied on the inner wall of the Φ70mm hollow pipe column, and the thickness of the graphite coating is 2mm.

[0074] An alumina substrate is placed at the bottom of the hollow tube column, and the thickness of the alumina substrate is 10 mm.

[0075] A steel mesh was placed on top of the alumina substrate.

[0076] Take ceramic balls with a diameter of 3 mm and metal aluminum blocks and place them evenly on the steel mesh inside the hollow column.

[0077] A layer of steel mesh is placed over the composite material.

[0078] Open the plunger and pour in the molten aluminum liquid. After pouring, close the plunger.

[0079] Turn on the superconducting high magnetic field device to generate a transverse static magnetic field and adjust the magnetic field strength to 10T.

[0080] The heater was turned on, the temperature was controlled at 1200° C. by a thermocouple, and argon gas was introduced through the vent.

[0081] After heat preservation and cooling, a foamed aluminum composite material containing ceramic balls is obtained.

[0082] Through cutting, it was found that the internal ceramic balls were evenly distributed and did not sink, meeting the requirements.

[0083] Example 2

[0084] The diameter of the ceramic balls was changed to 6 mm, and the above operation was repeated to obtain a foam aluminum composite material containing ceramic balls with uniform distribution.

[0085] Example 3

[0086] The diameter of the ceramic balls was changed to 10 mm, and the above operation was repeated to obtain a foam aluminum composite material containing ceramic balls with relatively uniform distribution.

[0087] Example 4

[0088] The diameter of the ceramic balls was changed to 15 mm, and the above operation was repeated. Through cutting, it was found that a few of the internal ceramic balls were bonded and the distribution was relatively uneven.

[0089] Example 5

[0090] The diameter of the ceramic balls was selected to be 3 mm, the strong magnetic field was changed to 8 T, and the above operation was repeated. Through cutting, it was found that the internal ceramic balls were bonded and unevenly distributed.

[0091] Example 8

[0092] The diameter of the ceramic balls was selected to be 3 mm, the strong magnetic field was changed to 9 T, and the above operation was repeated. Through cutting, it was found that the internal ceramic balls were sticking together and unevenly distributed.

[0093] Example 6

[0094] The diameter of the ceramic balls was selected to be 3 mm, the strong magnetic field was changed to 11 T, and the above operation was repeated. Through cutting, it was found that the internal ceramic balls were evenly distributed and there was no adhesion.

[0095] Example 7

[0096] The diameter of the ceramic balls was selected to be 3 mm, the strong magnetic field was changed to 12 T, and the above operation was repeated. Through cutting, it was found that the internal ceramic balls were evenly distributed and there was no adhesion.

[0097] Example 8

[0098] The diameter of the ceramic balls was selected to be 6 mm, the strong magnetic field was changed to 12 T, and the above operation was repeated. Through cutting, it was found that the internal ceramic balls were evenly distributed and there was no adhesion.

[0099] Example 9

[0100] Select a ceramic ball with a diameter of 10 mm, change the strong magnetic field to 10 T, repeat the above operation, and through cutting, find that the internal ceramic balls are evenly distributed and there is no adhesion.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing foamed aluminum containing ceramic balls based on a strong magnetic field, characterized in that: The following steps are involved: 1) Place an alumina substrate at the bottom of the hollow column; 2) Place a steel mesh on the alumina substrate; 3) Fill the hollow tube with aluminum blocks or alumina powder and ceramic balls according to the required porosity and internal ceramic ball distribution; 4) Place a layer of steel mesh on top of the composite material; 5) Open the plunger and pour in the molten aluminum. After pouring, close the plunger; 6) Turn on the superconducting high magnetic field device to generate a transverse static magnetic field and adjust the magnetic field strength; 7) Turn on the heater, control the temperature to 1200°C using a thermocouple, and introduce argon gas through the vent; 8) After heat preservation and cooling, a foamed aluminum composite material containing ceramic balls is obtained; Wherein, the strong magnetic field is a magnetic field above 5T.

2. The method for preparing foamed aluminum containing ceramic balls based on a strong magnetic field according to claim 1, characterized in that: The magnetic field strength adjustment range is 8-10T.

3. The method for preparing foamed aluminum containing ceramic balls based on a strong magnetic field according to claim 1, characterized in that: The ceramic balls are one or more of silicon carbide, aluminum oxide, zirconium oxide, and boron carbide ceramics.

4. The method for preparing foamed aluminum containing ceramic balls based on a strong magnetic field according to claim 1, characterized in that: The diameter of the ceramic balls ranges from 3 to 10 mm, and the ceramic balls account for 30% to 50% of the total volume of the composite material.

5. The method for preparing foamed aluminum containing ceramic balls based on a strong magnetic field according to claim 1, characterized in that: The inner wall of the hollow tubular column contains a graphite coating.

6. The method for preparing foamed aluminum containing ceramic balls based on a strong magnetic field according to claim 1, characterized in that: After the composite material is cooled along with the device, the aluminum oxide substrate and the steel mesh at the bottom are removed to obtain a foam aluminum composite material containing ceramic balls.

7. The method for preparing foamed aluminum containing ceramic balls based on a strong magnetic field according to claim 1, wherein: The device used in the method includes a hollow tube column (8), a plunger (1) matched with the hollow tube column (8), an air guide hole (2), a vent (9), a heater (7) and an inserted thermocouple (6) are provided on the hollow tube column (8), a graphite coating (3) is coated on the inner wall of the hollow tube column (8), and an alumina substrate (13) is supported on the bottom; ceramic balls (11) and metal aluminum (5) are filled in the middle, and a steel mesh (4) is provided on the top to separate the molten aluminum liquid (10); in addition, a strong magnetic field (12) is provided outside the device.

8. A device for the method for preparing foamed aluminum containing ceramic balls based on a strong magnetic field according to any one of claims 1 to 7, characterized in that: The device includes Hollow tube column (8); A plunger (1) engaged with the hollow tubular column (8); An air guide hole (2), a vent (9), a heater (7) and an inserted thermocouple (6) are provided on the hollow tube column (8); A graphite coating (3) is applied to the inner wall of the hollow tube column (8), and an alumina substrate (13) is supported at the bottom; ceramic balls (11) and metal aluminum (5) are filled in the middle, and a steel mesh (4) is provided above to separate the molten aluminum liquid (10). Furthermore, a strong magnetic field (12) is set outside the device.

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