Si particle reinforced aluminum-based composite material and preparation method thereof

Abstract

The invention relates to a preparation method of a Si particle reinforced aluminum-based composite material, which comprises the following steps: mixing Si particles with a pore-forming agent to obtain mixed powder; adding a binder into the mixed powder, mixing, putting into a mold pressing mold, and carrying out compression molding, so as to obtain a Si preform rough blank; sintering the Si prefabricated body rough blank to obtain a Si prefabricated body; and finally, mixing the Si preform and an aluminum alloy in a vacuum environment, heating to melt the aluminum alloy, and then introducing inert gas to pressurize to assist infiltration, so as to obtain the Si particle reinforced aluminum-based composite material. According to the preparation method, firstly, Si particles and a pore forming agent are uniformly mixed, and after a binder is added, the mixture is pressed and sintered to prepare a Si preform rough blank, so that the distribution uniformity of the particles can be improved and enhanced; and then mixing the Si preform rough blank with an aluminum alloy, heating in a vacuum environment, and then preparing the Si particle reinforced aluminum-based composite material through auxiliary infiltration under the pressure of 300-500kPa. According to the preparation method, required equipment is low in cost, and the aluminum alloy is well combined with the particles.

Description

Technical Field

[0001] This invention relates to the field of metal composite materials technology, and in particular to a Si particle reinforced aluminum matrix composite material and its preparation method. Background Technology

[0002] Aluminum matrix composites not only possess high specific strength and specific modulus, excellent heat resistance, creep resistance, and wear resistance, but also retain the high electrical and thermal conductivity of aluminum alloys. Based on the type of reinforcing phase, aluminum matrix composites are mainly divided into continuously reinforced and discontinuously reinforced aluminum matrix composites. Compared to continuously reinforced aluminum matrix composites, discontinuously reinforced aluminum matrix composites, represented by silicon (Si) particle reinforcement, have broad development prospects in commercial and civilian fields due to their good processability and lower manufacturing costs. Currently, the commonly used methods for preparing Si particle-reinforced aluminum matrix composites are stirred casting and powder metallurgy. The stirred casting process involves melting aluminum alloy into molten aluminum, then adding Si particles to the molten aluminum and stirring the casting process to finally obtain Si particle-reinforced aluminum matrix composites, such as... Figure 1 As shown, this process has a short preparation cycle, but the volume fraction of Si particles is small and they are prone to agglomeration. Powder metallurgy first mixes Si particles with aluminum powder, and then sintersulates the mixture under high pressure and high temperature to obtain a composite material. The composite material prepared by this process has good performance, but the sintering process usually requires a temperature greater than 1000℃ and a pressure greater than 150MPa, so it has high requirements for equipment and consumes a lot of energy. Summary of the Invention

[0003] Based on this, the purpose of the present invention is to provide a Si particle reinforced aluminum matrix composite material and its preparation method, which allows the aluminum alloy to fully penetrate into the Si preform at lower pressure and lower temperature, while avoiding Si particle agglomeration.

[0004] First aspect:

[0005] A method for preparing a Si particle-reinforced aluminum matrix composite material includes the following steps:

[0006] Si particles are mixed with a pore-forming agent to obtain a mixed powder.

[0007] A binder is added to the mixed powder, and after mixing, it is placed in a molding die and pressed to obtain a Si preform blank.

[0008] The Si preform blank is sintered at 700-900℃ for 60-120 min to obtain the Si preform;

[0009] The Si preform and aluminum alloy are placed in a vacuum environment and heated to 650-750°C. Then, an inert gas is introduced to 300-500 kPa to obtain a Si particle-reinforced aluminum matrix composite material.

[0010] This invention first involves uniformly mixing Si particles and a pore-forming agent, then adding a binder and pressing and sintering to prepare a Si preform, which improves the uniformity of the reinforcing particle distribution. Next, the Si preform is mixed with an aluminum alloy, heated in a vacuum environment, and then impregnated with pressure of 300-500 kPa to prepare a Si particle-reinforced aluminum matrix composite material. The preparation method of this invention requires low-cost equipment and can produce composite materials with high volumetric properties, uniform particle distribution, and good bonding between the aluminum alloy and the particles.

[0011] As a preferred embodiment, the volume ratio of the Si particles to the pore-forming agent is (2-9):1. If there is too much pore-forming agent, a large amount of gas will escape, which will damage the preform structure. If there is too little pore-forming agent, too little gas will be generated, resulting in too few pores or even no pores, and the aluminum alloy liquid will not be able to enter the Si particles.

[0012] As a preferred embodiment, the Si particles have a particle size of 20-100 μm. Particles smaller than 20 μm tend to agglomerate; those larger than 100 μm are prone to breakage during subsequent pressing and molding.

[0013] As a preferred embodiment, the pore-forming agent comprises starch with a particle size of 5-20 μm. Further, industrial corn starch is selected as the pore-forming agent. The smaller particle size of the starch compared to the Si particles facilitates its entry into the interstices of the Si particles, thereby improving the pore-forming efficiency.

[0014] As a preferred embodiment, the binder comprises silica sol, and the volume ratio of the binder to the mixed powder is 1:15-20. If there is too little binder, the bonding strength is insufficient, and the sintered preform is prone to cracking and disintegration; if there is too much binder, the powder is too viscous, making demolding and sintering difficult. Silica sol is a colloidal solution, odorless and non-toxic, with excellent dispersibility and permeability. During the sintering process, the moisture in the silica sol evaporates, and the colloidal particles firmly adhere to the surface of the Si particles, forming silicon-oxygen bonds between the particles.

[0015] As a preferred embodiment, the Si preform blank is heated at a rate of 5–10 °C / min during sintering. This avoids the violent decomposition and release of the pore-forming agent during the heating process, which could lead to structural damage, cracking, and collapse of the preform.

[0016] As a preferred embodiment, the aluminum alloy comprises AlSi12. AlSi12 aluminum alloys possess excellent casting properties, thermal conductivity, and lightweight characteristics.

[0017] As a preferred embodiment, the pressure of the vacuum environment is no greater than 100 Pa, and after evacuation, the temperature is increased to 600-800°C at a heating rate of 5-8°C / min. The low vacuum level can reduce the oxidation of the molten aluminum during the heating process.

[0018] As a preferred method, the pressure is maintained for 3–60 seconds after the inert gas is introduced. Too short a holding time will not allow for complete impregnation, while too long a time will affect production efficiency.

[0019] The second aspect:

[0020] A Si particle-reinforced aluminum matrix composite material as described in the first aspect has a flexural strength of 252-305 MPa. Attached Figure Description

[0021] Figure 1 This is a microscopic morphology diagram of Si particle agglomeration;

[0022] Figure 2 Here is a macroscopic morphology image of the Si preform prepared in Example 1;

[0023] Figure 3 This is a three-dimensional tomographic image of the particle morphology of the Si preform prepared in Example 1;

[0024] Figure 4 Here is a macroscopic morphology image of the Si particle-reinforced aluminum matrix composite material prepared in Example 2;

[0025] Figure 5 This is a microscopic morphology diagram of the Si particle-reinforced aluminum matrix composite material prepared in Example 2. Detailed Implementation

[0026] A method for preparing a Si particle-reinforced aluminum matrix composite material includes the following steps:

[0027] Si particles with a particle size of 20-100μm are washed and then dried at 100-150℃ for 120-240min. The pore-forming agent is dried. The Si particles and the pore-forming agent are mixed at a volume ratio of (2-9):1 to obtain a mixed powder.

[0028] Silica sol is added to the mixed powder, and the volume ratio of the mixed powder to the silica sol binder is 15-20:1. After mixing, the mixture is placed in a molding die and pressed to obtain a Si preform blank.

[0029] The Si preform blank is heated to 700-900℃ at a heating rate of 5-10℃ / min and sintered for 60-120min to obtain the Si preform.

[0030] The Si preform is mixed with AlSi12 at a pressure below 100 Pa, and the temperature is raised to 650-750°C at a heating rate of 5-8°C / min. Then, nitrogen gas is introduced to 300-500 kPa and the pressure is maintained for 3-60 s to obtain a Si particle-reinforced aluminum matrix composite material.

[0031] The pore-forming agent includes industrial corn starch with a particle size of 5-20 μm.

[0032] A Si particle-reinforced aluminum matrix composite material with a flexural strength ranging from 252 to 305 MPa.

[0033] Example 1

[0034] A method for preparing a Si particle-reinforced aluminum matrix composite material includes the following steps:

[0035] The surfaces of commercially available AlSi20 aluminum alloy and industrial pure aluminum are polished, degreased, and cleaned with industrial alcohol. They are then placed in a crucible according to a certain ratio and put into a melting furnace, heated to 700℃ to melt, and cast to obtain AlSi12 aluminum alloy.

[0036] Si particles with a particle size of 50 μm were washed and then dried at 150 °C for 120 min. Industrial corn starch with a particle size of 10 μm was dried at 60 °C for 30 min. The Si particles and pore-forming agent were mixed evenly in a mixer at a volume ratio of 9:1 to obtain a mixed powder.

[0037] The mixed powder and silica sol binder are prepared at a volume ratio of 15:1, stirred evenly, and then placed into a molding die. The mixture is then pressed into shape by a hydraulic press to obtain a Si preform blank.

[0038] The Si preform blank is placed in a box furnace and heated to 900℃ at a heating rate of 10℃ / min and held for 60 min to obtain the Si preform.

[0039] The Si preform and AlSi12 aluminum alloy were placed together in a crucible and then placed in an infiltration furnace. The furnace was then evacuated to 100 Pa and heated to 750 °C at a heating rate of 8 °C / min to melt the AlSi12 aluminum alloy.

[0040] High-purity nitrogen gas was introduced and pressurized to 300 kPa to allow molten AlSi12 to enter the Si preform. The pressure was maintained for 60 s, and after cooling, Si particle-reinforced aluminum matrix composite material was obtained.

[0041] like Figure 2 The image shows the macroscopic morphology of the prepared Si preform.

[0042] like Figure 3 As shown, the three-dimensional tomographic image of the prepared Si preform shows that the particle distribution is relatively uniform.

[0043] Example 2

[0044] A method for preparing a Si particle-reinforced aluminum matrix composite material includes the following steps:

[0045] The surfaces of commercially available AlSi20 aluminum alloy and industrial pure aluminum are polished, degreased, and cleaned with industrial alcohol. They are then placed in a crucible according to a certain ratio and put into a melting furnace, heated to 700℃ to melt, and cast to obtain AlSi12 aluminum alloy.

[0046] Si particles with a particle size of 50 μm were washed and then dried at 100 °C for 200 min. Industrial corn starch with a particle size of 10 μm was dried at 40 °C for 60 min. The Si particles and pore-forming agent were mixed evenly in a mixer at a volume ratio of 4:1 to obtain a mixed powder.

[0047] The mixed powder and silica sol binder were prepared at a volume ratio of 18:1, stirred evenly, and then placed into a molding die. The mixture was then pressed into shape by a hydraulic press to obtain a Si preform blank.

[0048] The Si preform blank is placed in a box furnace and heated to 800℃ at a heating rate of 8℃ / min and held for 120min to obtain the Si preform.

[0049] The Si preform and AlSi12 aluminum alloy were placed together in a crucible and then placed in an infiltration furnace. The furnace was then evacuated to 100 Pa and heated to 700 °C at a heating rate of 6 °C / min to melt the AlSi12 aluminum alloy.

[0050] High-purity nitrogen gas was introduced and pressurized to 400 kPa to allow molten AlSi12 to enter the Si preform. The pressure was maintained for 30 seconds, and after cooling, Si particle-reinforced aluminum matrix composite material was obtained.

[0051] like Figure 4 The image shows the macroscopic morphology of the prepared Si particle-reinforced aluminum matrix composite.

[0052] like Figure 5 As shown in the figure, the microstructure of the prepared Si particle-reinforced aluminum matrix composite material is highly uniform in particle distribution and has few residual pores.

[0053] Example 3

[0054] A method for preparing a Si particle-reinforced aluminum matrix composite material includes the following steps:

[0055] The surfaces of commercially available AlSi20 aluminum alloy and industrial pure aluminum are polished, degreased, and cleaned with industrial alcohol. They are then placed in a crucible according to a certain ratio and put into a melting furnace, heated to 700℃ to melt, and cast to obtain AlSi12 aluminum alloy.

[0056] Si particles with a particle size of 20 μm were washed and then dried at 100 °C for 120 min. Industrial corn starch with a particle size of 5 μm was dried at 40 °C for 60 min. The Si particles and pore-forming agent were mixed evenly in a mixer at a volume ratio of 7:3 to obtain a mixed powder.

[0057] Mix the powder and silica sol binder at a volume ratio of 20:1, stir evenly, put them into a molding die, and press them into shape using a hydraulic press to obtain a Si preform blank.

[0058] The Si preform blank is placed in a box furnace and heated to 700℃ at a heating rate of 5℃ / min and held for 120min to obtain the Si preform.

[0059] The Si preform and AlSi12 aluminum alloy were placed together in a crucible and then placed in an infiltration furnace. The furnace was then evacuated to 100 Pa and heated to 700 °C at a heating rate of 5 °C / min to melt the AlSi12 aluminum alloy.

[0060] High-purity nitrogen gas was introduced and pressurized to 500 kPa to allow molten AlSi12 to enter the Si preform. The pressure was maintained for 3 seconds, and after cooling, Si particle-reinforced aluminum matrix composite material was obtained.

[0061] Example 4

[0062] A method for preparing a Si particle-reinforced aluminum matrix composite material includes the following steps:

[0063] The surfaces of commercially available AlSi20 aluminum alloy and industrial pure aluminum are polished, degreased, and cleaned with industrial alcohol. They are then placed in a crucible according to a certain ratio and put into a melting furnace, heated to 700℃ to melt, and cast to obtain AlSi12 aluminum alloy.

[0064] Si particles with a particle size of 100 μm were washed and then dried at 120 °C for 120 min. Industrial corn starch with a particle size of 20 μm was dried at 50 °C for 40 min. The Si particles and pore-forming agent were mixed evenly in a mixer at a volume ratio of 4:1 to obtain a mixed powder.

[0065] The mixed powder and silica sol binder are prepared at a volume ratio of 16:1, stirred evenly, and then placed into a molding die. The mixture is then pressed into shape by a hydraulic press to obtain a Si preform blank.

[0066] The Si preform blank is placed in a box furnace and heated to 750℃ at a heating rate of 6℃ / min and held for 100min to obtain the Si preform.

[0067] The Si preform and AlSi12 aluminum alloy were placed together in a crucible and then placed in an infiltration furnace. The furnace was then evacuated to 100 Pa and heated to 750 °C at a heating rate of 6 °C / min to melt the AlSi12 aluminum alloy.

[0068] High-purity nitrogen gas was introduced and pressurized to 400 kPa to allow molten AlSi12 to enter the Si preform. The pressure was maintained for 10 seconds, and after cooling, Si particle-reinforced aluminum matrix composite material was obtained.

[0069] Example 5

[0070] Bending strength test:

[0071] The Si particle-reinforced aluminum matrix composites prepared in Examples 1-3 were processed into rectangular strips with dimensions that met the ISO 14125 standard through a three-point bending test. A load was applied at a constant rate of 1 mm / min, and the load-displacement curve was recorded until the sample broke. The average value was calculated after multiple measurements.

[0072] The flexural strengths of the Si particle-reinforced aluminum matrix composites prepared in Examples 1-3 were measured to be 305 MPa, 278 MPa and 252 MPa, respectively. It can be seen that the higher the Si particle content, the higher the flexural strength of the prepared composite material.

[0073] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A method for preparing a Si particle-reinforced aluminum matrix composite material, characterized in that, Includes the following steps: Si particles are mixed with a pore-forming agent to obtain a mixed powder. A binder is added to the mixed powder, and after mixing, it is placed in a molding die and pressed to obtain a Si preform blank. The Si preform blank is sintered at 700-900℃ for 60-120 min to obtain the Si preform; The Si preform and aluminum alloy are placed in a vacuum environment and heated to 650-750°C. Then, an inert gas is introduced to 300-500 kPa to obtain a Si particle-reinforced aluminum matrix composite material.

2. The method for preparing a Si particle-reinforced aluminum matrix composite material according to claim 1, characterized in that, The volume ratio of the Si particles to the pore-forming agent is (2-9):

1.

3. The method for preparing a Si particle-reinforced aluminum matrix composite material according to claim 1, characterized in that, The Si particles have a particle size of 20-100 μm.

4. The method for preparing a Si particle-reinforced aluminum matrix composite material according to claim 1, characterized in that, The pore-forming agent includes starch with a particle size of 5-20 μm.

5. The method for preparing a Si particle-reinforced aluminum matrix composite material according to claim 1, characterized in that, The binder includes silica sol, and the volume ratio of the binder to the mixed powder is 1:15-20.

6. The method for preparing a Si particle-reinforced aluminum matrix composite material according to claim 1, characterized in that, The Si preform is heated at a rate of 5–10 °C / min during sintering.

7. The method for preparing a Si particle-reinforced aluminum matrix composite material according to claim 1, characterized in that, The aluminum alloy includes AlSi12.

8. The method for preparing a Si particle-reinforced aluminum matrix composite material according to claim 1, characterized in that, The pressure of the vacuum environment is no greater than 100 Pa, and after evacuation, the temperature is raised to 600-800°C at a rate of 5-8°C / min.

9. The method for preparing a Si particle-reinforced aluminum matrix composite material according to claim 8, characterized in that, After introducing the inert gas, maintain the pressure for 3 to 60 seconds.

10. A Si particle-reinforced aluminum matrix composite material prepared according to any one of claims 1 to 9, characterized in that, The flexural strength is 252-305 MPa.

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