A process for copper pyrophosphate aluminizing

Abstract

The application relates to the field of material science and engineering, and particularly discloses a process for aluminizing copper pyrophosphate, which comprises the following steps: S1: preparing a copper pyrophosphate preform by adopting an indirect 3D printing technology, comprising the following steps: S11: establishing a three-dimensional model of the preform; S12: printing a green body of the copper pyrophosphate by using an indirect 3D printer; and S13: placing the green body in a n-heptane solvent for debinding, wherein the debinding temperature is 50 DEG C, and the debinding time is 36 hours; the process combines the indirect 3D printing technology with an optimized debinding and sintering process, realizes high-precision forming and uniform pore control of the complex-structure copper pyrophosphate preform, and provides ideal basic conditions for subsequent liquid aluminum infiltration; through a sintering process with ladder-type temperature control and a specific proportioning aluminum alloy infiltration scheme, the interface bonding of the composite material is significantly enhanced, and the overall performance of the material is comprehensively improved.

Description

TECHNICAL FIELD

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

[0002] In the field of material science and engineering, metal matrix composites are widely used in aerospace, electronic packaging, automobile manufacturing, etc. due to their excellent mechanical properties, thermal physical properties and wear resistance. Among them, aluminum matrix composites have become a research hotspot due to the light weight, high thermal conductivity and good processing performance of aluminum. Copper pyrophosphate, as a reinforcing phase, has a high melting point, good thermal stability and controllable pore structure, which can effectively improve the strength, thermal conductivity and high temperature performance of aluminum matrix composites.

[0003] Currently, the preparation of aluminum matrix composites mainly relies on powder metallurgy and melt infiltration technology:

[0004] Powder metallurgy: metal powder and reinforcing phase are mixed and then pressed and sintered. However, this method can easily lead to uneven distribution of reinforcing bodies, and it is difficult to prepare complex structures. The porosity control during sintering is difficult, which affects the material density and mechanical properties.

[0005] Melt infiltration: molten aluminum is infiltrated into a porous preform. However, the traditional preform relies on mold pressing or slurry casting, which has poor forming precision for microstructures, and the preform has low strength after demolding, which can easily collapse during infiltration. SUMMARY

[0006] To solve the above technical problems, the present application provides a process for copper pyrophosphate aluminizing to solve the problems of insufficient forming precision of complex structure preform, uneven distribution of reinforcing bodies and poor interfacial bonding strength during melt infiltration in the prior art.

[0007] A process for copper pyrophosphate aluminizing, comprising the following steps:

[0008] S1: preparing a copper pyrophosphate preform using indirect 3D printing technology, comprising:

[0009] S11: establishing a three-dimensional model of the preform;

[0010] S12: printing a green body of copper pyrophosphate using an indirect 3D printer;

[0011] S13: placing the green body in a n-heptane solvent for debinding, with a debinding temperature of 50℃ and a debinding time of 36 hours;

[0012] S14: sintering the debound green body: heating from 20℃ to 300℃ for 94 minutes, holding for 1 hour, then heating from 300℃ to 600℃ for 100 minutes, holding for 1 hour, and finally heating from 600℃ to 1100℃ for 168 minutes, holding for 2 hours, and cooling in the furnace;

[0013] S2: infiltrating the preform with aluminum alloy melt, comprising:

[0014] S21: proportioning aluminum ingot according to Al:Al-20Si=1:1, heating to 750℃ and melting;

[0015] S22: proportioning magnesium block according to (M Al +M Al-20Si )×0.3%×1.5, wrapping with aluminum foil, adding into aluminum liquid using tools, and reacting for 10 minutes;

[0016] S23: adding refining agent to remove slag, the refining agent accounting for 0.5% of the total mass of aluminum ingot and magnesium block;

[0017] S24: preheating the preform and mold to 600℃;

[0018] S25: pouring aluminum liquid into the mold, pressure casting for 3 minutes, and cooling;

[0019] S3: testing the performance of the composite material.

[0020] Preferably, the structural parameters of the preform model in S11 include: large circle diameter 40mm, small circle diameter 0.7mm, and height 6mm.

[0021] Preferably, the indirect 3D printer in S12 is Huisheng Three-Dimensional-UPS-250.

[0022] Preferably, the volume ratio of n-heptane solvent to model in S13 is ≥7:1.

[0023] Preferably, the refining agent in S22 is wrapped with aluminum foil before being added into the melt.

[0024] Preferably, the pressure casting pressure in S24 is controlled in the range of 5-10MPa.

[0025] Preferably, S3 includes testing the thermal conductivity of the composite material.

[0026] Preferably, S3 includes three-point bending strength test.

[0027] Preferably, S3 includes SEM microstructure test.

[0028] Preferably, after debinding in S13, the sample is soaked in kerosene for 30 minutes and dried at 50℃ for 6 hours.

[0029] Compared with the prior art, the present application has the following beneficial effects:

[0030] By combining indirect 3D printing technology with optimized debinding and sintering process, high-precision forming and uniform pore control of complex structure copper pyrophosphate preform are realized, which provides ideal foundation conditions for subsequent aluminum liquid infiltration.

[0031] Through the sintering process of step temperature control and the specific ratio of aluminum alloy infiltration scheme, the interface bonding of the composite material is significantly enhanced, and the overall performance of the material is comprehensively improved.

[0032] By using an integrated debinding and sintering process, the preparation efficiency is greatly improved, and the problem of preform strength loss in traditional process is avoided.

[0033] Through standardized parameter control and process optimization, the process stability and repeatability are significantly improved, providing a reliable technical path for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A three-dimensional view of the copper pyrophosphate preform of the present application;

[0035] Figure 2 A slice view of the copper pyrophosphate preform of the present application;

[0036] Figure 3 A finished product view of the copper pyrophosphate preform of the present application;

[0037] Figure 4 The preform after sintering of the copper pyrophosphate preform of the present application;

[0038] Figure 5 A finished product view of the copper pyrophosphate preform after aluminum infiltration of the present application;

[0039] Figure 6 A cut sample view of the copper pyrophosphate preform of the present application;

[0040] Figure 7 A load and displacement graph measured by three-point bending test;

[0041] Figure 8 A thermal conductivity graph of the sample cross-section interface;

[0042] Figure 9 A thermal expansion graph of the sample cross-section, the serial number represents the cycle;

[0043] Figure 10 A flowchart of the entire experiment;

[0044] Figure 11 A scanning electron microscope view of the sample cross-section. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0046] As shown in Figures 1 to 10 ,

[0047] Embodiment one: the present application provides a process for copper pyrophosphate aluminizing, comprising the following steps:

[0048] I. Preparation of the preform

[0049] Printing: as Figure 1 , a model is established using solidworks software. The large circle diameter is 40 mm, the small circle diameter is 0.7 mm, and the height is 6 mm. The established model is opened in the slicing software, the printing parameters are set and saved. The UPS-250 type 3D printer is used for printing. According to the printing result, the printing parameters are adjusted on the slicing software until the printing is successful, as Figure 2 .

[0050] 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 after thermal degreasing is completely removed, the micro-pores in the preform are increased, as Figure 3 , the preform has no strength, so the thermal degreasing and sintering are carried out at the same time in this experiment. The solvent degreasing process is as follows: 1. Weighing: the model to be degreased is weighed with an electronic balance, 2. Determining the volume of the solvent: the volume of the model is calculated, and the n-heptane solvent is weighed according to the volume of the model, the volume of the n-heptane solvent / model volume≥7:1. 3. Put into the model: put the container containing the n-heptane solvent into the water bath, and set the water bath temperature to 50℃. When the temperature of the n-heptane solvent rises to 50℃, put the model to be degreased into the container containing the n-heptane solvent for degreasing, and the degreasing time is 36 hours. 4. Soak in kerosene: after reaching the specified degreasing time, take out the container containing the n-heptane solvent, and stand until room temperature. After standing, another suitable and clean container is prepared, a certain amount of kerosene is taken to ensure that the sample can be completely immersed; the sample is quickly transferred from n-heptane to kerosene for soaking for about 30 minutes. 5. Natural air drying: after soaking in kerosene, the sample is placed in the specified area for natural air drying, and the natural air drying time is 2 hours. 6. Drying: the model is placed in the drying box, the temperature is set to 50℃, and the time is set to 6 hours for drying.

[0051] Sintering: Put the defatted sample in the muffle furnace, set the program: initial temperature 20℃, 94 minutes to 300℃, 1 hour holding. 100 minutes to 600℃, 1 hour holding. 168 minutes to 1100℃, 2 hours holding, then end, and get the preform after cooling down with the furnace, such as Figure 4 .

[0052] II. Aluminizing

[0053] 1. Start the first pit furnace for melting aluminum, and heat it to 200℃;

[0054] 2. Clean the crucible, clamp and other tools. Mainly to clean the previous release coating;

[0055] 3. Brush the new release coating and put it in the first pit furnace for drying for about 10 minutes;

[0056] 4. Prepare the aluminum ingot (Al:Al-20si=1:1);

[0057] 5. Put the prepared aluminum ingot into the crucible, and then put the crucible into the first pit furnace, and raise the temperature to 750℃;

[0058] 6. Apply release coating to the mold, and put it into the second pit furnace together with the preform (the preform and a pedestal are bonded together with high-temperature glue), set the program: initial temperature 30℃, 190 minutes to 600℃, holding time 2000 minutes. The holding time should be as long as possible to ensure that the required operation can be completed within the holding time;

[0059] 7. After about 3 hours, the temperature of the first pit furnace is 750℃. According to (M Al +M Al-20Si )×0.3%×1.5, prepare magnesium blocks, wrap them with aluminum foil, and add them to the aluminum liquid using tools, and react for 10 minutes; weigh the refining agent, which is 0.5% of the total mass of the aluminum ingot and magnesium blocks, wrap it with aluminum foil, and put it into the crucible in the first pit furnace, and use a graphite rod to stir and remove the surface dross;

[0060] 8. Start the press, test the pressure of an article to adjust the pressure to the desired pressure for die casting operation;

[0061] 9. Place the lower gasket and base on the edge of the press operation table;

[0062] 10. Take out the crucible from the first pit furnace and place it on the graphite gasket to cool down, remove the surface dross of the aluminum liquid, and measure the temperature with a thermocouple;

[0063] 11. When the temperature of the aluminum liquid approaches 750℃, take out the mold and preform from the second pit furnace and place them on the lower gasket, and use tools to push them to the middle of the press;

[0064] 12. Pour the liquid aluminum into the mold, cover the press head;

[0065] 13. Perform die casting, keep pressure for 3 minutes, and put into cold water to cool when the temperature of the liquid aluminum drops to 450℃;

[0066] 14. Use a small press to take out the final product, such as Figure 5 .

[0067] Example Two:

[0068] Use a wire cutting machine to cut the finished product into the required size, such as Figure 6 , and perform some performance tests, such as three-point bending test (such as Figure 7 ), scanning electron microscope (such as Figure 11 ), etc.;

[0069] Bending strength is a mechanical property parameter that characterizes the resistance of a material to fracture under bending load. Its physical meaning is to quantify the maximum stress value that the material can withstand when subjected to bending deformation. It reflects the ability of the material to resist bending failure under lateral force, and is an important basis for the design of the carrying capacity of structural materials under bending load conditions (such as beams and shafts);

[0070] For example Figure 7 , the bending strength is 96.20 MPa, indicating that the composite material prepared by the application has good mechanical properties.

[0071] Thermal conductivity (also known as thermal conductivity) is a thermal property parameter that describes the heat conduction ability of a material. Its physical meaning is the ratio of heat passing through a unit cross-sectional area per unit time to the temperature gradient. It represents the rate of heat transfer in a material, and its size depends on the microstructure of the material (such as lattice vibration, free electron motion, etc.), which is a core indicator for measuring the heat insulation or heat conduction performance of a material;

[0072] For example Figure 8 , the transverse thermal conductivity is 15.3 W / (m.K) at 350K, indicating that the composite material prepared by the application has good thermal conductivity.

[0073] Thermal expansion is a thermal phenomenon that refers to the change in volume or length of a material when the temperature changes. Its physical meaning is that when a material is heated, the molecular or atomic thermal motion intensifies, causing the micro gap to increase, which is manifested as expansion in size (contraction when cooled). The thermal expansion coefficient (linear expansion coefficient or volume expansion coefficient) is used to quantitatively describe the relative change in length or volume caused by a unit temperature change. This parameter reflects the thermal stability of the material;

[0074] For example Figure 9The tested thermal expansion coefficient of the composite material is stabilized at 5.412 ppm / K in the temperature range of 240-330 K, indicating that the composite material prepared by the application has good stability; and the serial number in the figure represents the cycle number.

[0075] The embodiments of the present application are given for example and description, although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and the changes, modifications, replacements and variations of the above embodiments made by the ordinary skilled in the art within the scope of the present application shall be included in the protection scope of the present application.

Claims

1. A process for copper pyrophosphate aluminizing, characterized in that: The following steps are involved: S1: Preparation of a copper pyrophosphate preform using indirect 3D printing technology, 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 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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