Copper pyrophosphate aluminizing process

Abstract

The invention relates to the field of material science and engineering, and particularly discloses a copper pyrophosphate aluminizing process which comprises the following steps: S1, preparing a copper pyrophosphate preform by adopting an indirect 3D printing technology: S11, establishing a preform three-dimensional model; s12, an indirect 3D printer is used for printing a copper pyrophosphate green body; s13, the green body is placed in an n-heptane solvent to be degreased, the degreasing temperature is 50 DEG C, and the degreasing time is 36 hours; the indirect 3D printing technology and the optimized degreasing and sintering technology are combined, high-precision forming and uniform pore control of the copper pyrophosphate preform with the complex structure are achieved, and ideal basic conditions are provided for follow-up molten aluminum permeation; and through the step type temperature control sintering process and the aluminum alloy infiltration scheme with the specific proportion, the interface bonding of the composite material is remarkably enhanced, and the overall performance of the material is comprehensively improved.

Description

Technical Field

[0001] The invention belongs to the field of material science and engineering, and in particular relates to a process for copper pyrophosphate aluminizing. Background Art

[0002] In the field of materials science and engineering, metal-based composites (MMCs) are widely used in aerospace, electronic packaging, automotive manufacturing, and other fields due to their excellent mechanical, thermophysical, and wear resistance properties. Aluminum-based composites, in particular, have become a research hotspot due to their lightweight, high thermal conductivity, and excellent processability. Copper pyrophosphate, as a reinforcing phase, exhibits a high melting point, excellent thermal stability, and a controllable pore structure, effectively enhancing the strength, thermal conductivity, and high-temperature performance of aluminum-based composites.

[0003] At present, the preparation of aluminum-based composite materials mainly relies on powder metallurgy and melt infiltration technology: Powder metallurgy involves mixing metal powder with reinforcements, pressing and sintering the mixture. However, this method can lead to uneven reinforcement distribution and makes it difficult to create complex structures. Controlling porosity during sintering can also be challenging, impacting the material's density and mechanical properties.

[0004] Melt infiltration: Molten aluminum is infiltrated into a porous preform. However, traditional preforms rely on mold pressing or slurry casting, which results in poor molding accuracy for fine structures. Furthermore, the preforms are weak after demolding and are prone to collapse during infiltration. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a process for copper pyrophosphate aluminum infiltration to solve the problems of insufficient molding accuracy of complex structure preforms, uneven distribution of reinforcements and poor interface bonding strength during the infiltration process in the prior art.

[0006] A process for copper pyrophosphate aluminizing comprises the following steps: S1: A copper pyrophosphate preform is prepared using an indirect 3D printing technique, including: S11: Establishing a 3D model of the prefabricated body; S12: Printing copper pyrophosphate green body using indirect 3D printer; S13: Degreasing the green body in n-heptane solvent at a temperature of 50° C. for 36 hours; S14: Sintering the degreased green body: heating from 20°C to 300°C over 94 minutes and holding for 1 hour, then heating to 600°C over 100 minutes and holding for 1 hour, and finally heating to 1100°C over 168 minutes and holding for 2 hours, followed by cooling in the furnace; S2: Infiltrating the preform with an aluminum alloy melt, comprising: S21: heat aluminum ingots in a ratio of Al:Al-20Si=1:1 to 750℃ and melt; S22: Press (M Al +M Al-20Si )×0.3%×1.5 with magnesium block, wrapped with aluminum foil, add it to the aluminum liquid using tools, and react for 10 minutes; S23: adding 0.5% of the total mass of the aluminum ingot and magnesium block as a refining agent for slag removal; S24: preheating the preform and the mold to 600° C. S25: pouring aluminum liquid into the mold, holding the die casting pressure for 3 minutes and then cooling; S3: performing a performance test on the composite material.

[0007] Preferably, the structural parameters of the preform model in S11 include: a large circle diameter of 40 mm, a small circle diameter of 0.7 mm, and a height of 6 mm.

[0008] Preferably, the indirect 3D printer in S12 is a Huasheng 3D-UPS-250 model.

[0009] Preferably, the ratio of the volume of the n-heptane solvent to the volume of the model in S13 is ≥7:1.

[0010] Preferably, the refining agent in S22 is wrapped with aluminum foil and then added to the melt.

[0011] Preferably, the die-casting pressure in S24 is controlled in the range of 5-10 MPa.

[0012] Preferably, S3 includes performing a thermal conductivity test on the composite material.

[0013] Preferably, S3 includes a three-point bending strength test.

[0014] Preferably, S3 includes SEM microstructural testing.

[0015] Preferably, after degreasing in S13, the step further includes soaking the sample in kerosene for 30 minutes and drying it at 50° C. for 6 hours.

[0016] Compared with the prior art, the present invention has the following beneficial effects: By combining indirect 3D printing technology with an optimized debinding and sintering process, high-precision molding and uniform porosity control of complex structure copper pyrophosphate preforms were achieved, providing ideal basic conditions for subsequent aluminum liquid infiltration. Through the step-by-step temperature-controlled sintering process and the aluminum alloy infiltration scheme with a specific ratio, the interface bonding of the composite material is significantly enhanced, which comprehensively improves the overall performance of the material. By adopting an integrated debinding and sintering process, the production efficiency is greatly improved while avoiding the problem of preform strength loss in traditional processes. Through standardized parameter control and process optimization, significant improvements in process stability and repeatability have been achieved, providing a reliable technical path for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A three-dimensional diagram of the copper pyrophosphate preform of the present invention; Figure 2 This is a cross-sectional view of the copper pyrophosphate preform of the present invention; Figure 3 The finished product of the copper pyrophosphate preform of the present invention is shown; Figure 4 The copper pyrophosphate preform of the present invention is sintered; Figure 5 The finished product of the copper pyrophosphate preform of the present invention after aluminizing; Figure 6 The copper pyrophosphate preform of the present invention is a cut sample diagram; Figure 7 is the load and displacement diagram measured by the three-point bending test; Figure 8 is the thermal conductivity diagram of the sample's transverse interface; Figure 9 is the thermal expansion diagram of the sample cross section, and the serial number represents the cycle; Figure 10 This is the flow chart of the entire experiment; Figure 11 is a scanning electron microscope image of the sample cross section. DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] like Figures 1 to 10 As shown: Example 1: The present invention provides a process for copper pyrophosphate aluminizing, comprising the following steps: 1. Preparation of preform Print: Such as Figure 1 , use solidworks software to build the model. The diameter of the large circle is 40mm, the diameter of the small circle is 0.7mm, and the height is 6mm. Open the built model in the slicing software, set the printing parameters and save it. Use UPS-250 3D printer to print. According to the printing results, adjust the printing parameters on the slicing software until the printing is successful, such as Figure 2 .

[0020] Degreasing: The printed green body needs to be degreased to remove the glue contained in the raw material particles. Degreasing is divided into solvent degreasing and thermal degreasing. Since the glue in the preform is completely removed after thermal degreasing, the micropores in the preform become more numerous, such as Figure 3 , the preform has no strength, so the thermal degreasing and sintering are carried out together in this experiment. Solvent degreasing process: 1. Weighing: Weigh the model to be degreased with an electronic balance, 2. Determine the solvent volume: Calculate the model volume, weigh the n-heptane solvent according to the model volume, the n-heptane solvent volume / model volume ≥7:1. 3. Place the model: Place the container containing the n-heptane solvent in a water bath, set the water bath temperature to 50°C, and when the temperature of the n-heptane solvent rises to 50°C, place the model to be degreased in the container containing the n-heptane solvent for degreasing. The degreasing time is 36 hours. 4. Immerse in kerosene: After the specified degreasing time is reached, take out the container containing the n-heptane solvent and let it stand to room temperature. After standing, prepare another clean container of suitable size, take a certain amount of kerosene to ensure that the sample can be completely immersed; quickly transfer the sample from the n-heptane to the kerosene and soak for about 30 minutes. 5. Air drying: After soaking in kerosene, place the sample in a designated area to air dry for 2 hours. 6. Drying: Place the model in a drying oven, set the temperature to 50°C, and set the drying time to 6 hours.

[0021] Sintering: Place the degreased sample in a muffle furnace and set the program: initial temperature 20℃, raise to 300℃ in 94 minutes, keep warm for 1 hour. Raise to 600℃ in 100 minutes, keep warm for 1 hour. Raise to 1100℃ in 168 minutes, keep warm for 2 hours, and then cool in the furnace to obtain a preform. Figure 4 .

[0022] 2. Aluminizing 1. Open the first pit furnace for melting aluminum and raise the temperature to 200°C; 2. Clean the crucible, fixtures and other tools. Mainly to clean the previous release paint; 3. Apply new release paint and place in the first pit oven to dry for about 10 minutes; 4. Aluminum ingot (Al:Al-20si=1:1); 5. Place the prepared aluminum ingot into the crucible, then place the crucible into the first pit furnace and raise the temperature to 750°C; 6. Apply release coating to the mold and place it in the second pit furnace together with the preform (the preform and a base are glued together with high-temperature glue). Set the program to start at 30°C, increase to 600°C in 190 minutes, and hold at this temperature for 2000 minutes. The holding time should be as long as possible to ensure that the required operations can be completed within the holding time. 7. After about 3 hours, the temperature of the first pit furnace is 750℃. Press (M Al +MAl-20Si )×0.3%×1.5 magnesium block, wrapped in aluminum foil, added to the aluminum liquid using a tool, and reacted for 10 minutes; weighed the refining agent, the mass of which was 0.5% of the total mass of the aluminum ingot and magnesium block, wrapped in aluminum foil, and placed in the crucible in the first pit furnace, stirred with a graphite rod, and the scum on the surface was removed; 8. Turn on the press, test press an item to see the pressure, adjust the pressure to get the desired pressure and perform the die casting operation; 9. Place the lower gasket and base on the edge of the press operating table; 10. Take out the crucible from the first pit furnace, place it on a graphite gasket to cool, remove the scum on the surface of the aluminum liquid, and measure the temperature with a thermocouple; 11. When the aluminum liquid temperature approaches 750℃, take out the mold and preform from the second pit furnace, place them on the lower gasket, and use tools to push them to the middle of the press; 12. Pour the aluminum liquid into the mold and cover it with the pressure head; 13. Perform die casting and maintain pressure for 3 minutes. When the aluminum liquid temperature drops to 450℃, cool it in cold water. 14. Use a small press to take out the final product, such as Figure 5 .

[0023] Example 2: Use wire cutting machine to cut the finished product into required size, such as Figure 6 , and conduct some performance tests, such as three-point bending test (such as Figure 7 ), scanning electron microscopy (e.g. Figure 11 )wait; Flexural strength is a mechanical property parameter that characterizes a material's resistance to fracture under bending loads. Its physical significance lies in quantifying the maximum stress a material can withstand when subjected to bending deformation. It reflects a material's ability to resist bending failure under lateral forces and is an important basis for designing the load-bearing capacity of structural materials subjected to bending loads (e.g., beams and shafts). like Figure 7 After testing, the flexural strength is 96.20 MPa, indicating that the composite material prepared by the present invention has good mechanical properties.

[0024] Thermal conductivity (also known as thermal conductivity coefficient) is a thermal property parameter that describes a material's ability to conduct heat. Its physical meaning is the ratio of the amount of heat passing through a unit cross-sectional area per unit time to the temperature gradient. It characterizes the rate at which a material transfers heat, and its magnitude depends on the material's microstructure (such as lattice vibrations and free electron motion). It is a core indicator for measuring a material's thermal insulation or thermal conductivity. like Figure 8 After testing, its transverse thermal conductivity is 15.3W / (mK) at 350K, indicating that the composite material prepared by the present invention has good thermal conductivity.

[0025] Thermal expansion refers to the thermal phenomenon in which a material changes in volume or length when its temperature changes. Its physical meaning is that when a material is heated, the thermal motion of its molecules or atoms intensifies, leading to an increase in microscopic gaps, which manifests itself macroscopically as dimensional expansion (or contraction when the temperature drops). It is usually quantitatively described by the coefficient of thermal expansion (linear expansion coefficient or volume expansion coefficient), which is the relative change in length or volume caused by a unit temperature change. This parameter reflects the thermal stability of the material. like Figure 9 After testing, it was found that within the temperature range of 240-330K, the thermal expansion coefficient of the composite material was stable at 5.412ppm / K, indicating that the composite material prepared by the present invention has good stability; the serial numbers in the figure represent the number of cycles.

[0026] The embodiments of the present invention are provided for the purpose of illustration and description. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present invention. Any changes, modifications, replacements and variations of the above embodiments by ordinary technicians in this field within the scope of the present invention should be included in the scope of protection of the present invention.

Claims

1. A process for copper pyrophosphate aluminizing, characterized in that: The following steps are involved: S1: A copper pyrophosphate preform is prepared using an indirect 3D printing technique, including: S11: Establishing a 3D model of the prefabricated body; S12: Printing copper pyrophosphate green body using indirect 3D printer; S13: Degreasing the green body in n-heptane solvent at a temperature of 50° C. for 36 hours; S14: Sintering the degreased green body: heating from 20°C to 300°C over 94 minutes and holding for 1 hour, then heating to 600°C over 100 minutes and holding for 1 hour, and finally heating to 1100°C over 168 minutes and holding for 2 hours, followed by cooling in the furnace; S2: Infiltrating the preform with an aluminum alloy melt, comprising: S21: heat aluminum ingots in a ratio of Al:Al-20Si=1:1 to 750℃ and melt; S22: Press (M Al +M Al-20Si )×0.3%×1.5 with magnesium block, wrapped with aluminum foil, add it to the aluminum liquid using tools, and react for 10 minutes; S23: adding 0.5% of the total mass of the aluminum ingot and magnesium block as a refining agent for slag removal; S24: preheating the preform and the mold to 600° C. S25: pouring aluminum liquid into the mold, holding the die casting pressure for 3 minutes and then cooling to obtain a composite material; S3: performing a performance test on the composite material.

2. A process for copper pyrophosphate aluminizing as claimed in claim 1, characterized in that: The structural parameters of the preform model in S11 include: a large circle diameter of 40 mm, a small circle diameter of 0.7 mm, and a height of 6 mm.

3. A process for copper pyrophosphate aluminizing as claimed in claim 1, characterized in that: The indirect 3D printer described in S12 is the Huasheng 3D-UPS-250 model.

4. A process for copper pyrophosphate aluminizing as claimed in claim 1, characterized in that: The ratio of the volume of the n-heptane solvent to the volume of the model described in S13 is ≥7:

1.

5. A process for copper pyrophosphate aluminizing as claimed in claim 1, characterized in that: The refining agent in S22 is wrapped with aluminum foil and then added to the melt.

6. A copper pyrophosphate aluminizing process as claimed in claim 1, characterized in that: The die-casting pressure in S25 is controlled in the range of 5-10 MPa.

7. A copper pyrophosphate aluminizing process as claimed in claim 1, characterized in that: S3 involves thermal conductivity testing of composite materials.

8. A copper pyrophosphate aluminizing process as claimed in claim 1, characterized in that: S3 includes a three-point bending strength test.

9. A copper pyrophosphate aluminizing process as claimed in claim 1, characterized in that: S3 includes SEM microstructural testing.

10. A copper pyrophosphate aluminizing process as claimed in claim 1, characterized in that: After degreasing, S13 also included soaking the sample in kerosene for 30 minutes and drying it at 50°C for 6 hours.

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