CN113290245B - A process for preparing metal matrix ceramic composites by applying secondary pressure - Google Patents

Abstract

The invention relates to a process for preparing a metal matrix ceramic composite material by secondary pressure application, which comprises a product forming die assembly, a sleeve die, a bottom plate, a press ejector rod, a workbench and a secondary pressure base plate, wherein the workbench is arranged on a press, the upper surface of the workbench is provided with the sleeve die in a matching way, the middle part of the sleeve die is provided with the bottom plate in a matching way, the product forming die assembly is placed above the bottom plate, the bottom surface of the bottom plate is abutted with the press ejector rod, the press ejector rod penetrates through the workbench, and the bottom plate and the product forming die assembly are controlled to move up and down in a cavity of the sleeve die by the lifting of the press ejector rod; powder is directly filled into a product forming die assembly, so that the preparation process of a prefabricated part is omitted; in the process of die-casting metal infiltration, secondary pressure is applied to the gradually solidified metal core part; the composite material prepared by the method has high compactness and low porosity, and the quality and the performance of the product are greatly improved.

Description

A process for preparing metal matrix ceramic composites by applying secondary pressure

technical field

The invention relates to the technical field of composite material preparation technology, in particular to a technology for preparing a metal matrix ceramic composite material by applying secondary pressure.

Background technique

In recent years, with the rapid development of science and technology and economy, the large demand for lightweight, high thermal conductivity and low expansion materials has prompted the rapid development of metal matrix composite materials. Metal matrix composites have both the properties of metal itself and the comprehensive properties of non-metals, and are far superior to matrix metals in terms of strength and toughness, wear resistance, heat resistance, heat dissipation, and hardness.

The main reason for preparing metal matrix composites is to improve the thermal conductivity and low expansion properties of metal matrix composites, and at the same time improve the tensile strength, proof stress, elastic modulus and heat resistance of metal matrix composites. These properties can be adjusted in a number of ways, depending on the material and reinforcement levels added, and the matrix/reinforcement compound used. Metal matrix composites therefore have good comprehensive properties.

Particle-reinforced metal matrix ceramic composites have good thermal conductivity, low thermal expansion performance and small density characteristics, which can meet the requirements of modern electronic components for heat dissipation, packaging and welding, and lightweight. Particle-reinforced metal matrix ceramic composites are considered to be the most promising new generation of advanced composite materials in the 21st century, and have been widely used in aerospace, electronics industry, military radar, rail transit and other fields.

At present, the preparation process of metal matrix ceramic composites is mainly divided into two categories: solid phase process and liquid phase process. The solid phase process includes powder metallurgy, hot isostatic pressing, spark plasma sintering, etc., and the liquid phase process includes stirring. Fusion casting method, pressureless infiltration method, pressure casting method, etc. The above methods have their own advantages and disadvantages, but if you need to consider mass production, die-casting technology is the best choice. It has high production efficiency, and is suitable for forming parts with complex structures and high dimensional accuracy, enabling large-scale, low-cost manufacturing. .

The traditional die-casting technology of metal matrix ceramic composites is to prepare preforms of reinforcement particles first, and then preheat the preforms together with the mold, and then press the metal into the preforms under the action of the press, and then press and hold the pressure. Steps such as cooling and demolding are performed to obtain a blank of the metal matrix ceramic composite material. Although the process is efficient and simple, there are still some problems in actual production. On the one hand, the prepared preform needs to add a binder or a pore-forming agent, whether it is wet preparation (drying moisture and then sintering) or dry preparation (molding After forming and sintering), the residual binder in the preform will affect the performance of the composite material to a certain extent, and problems such as uneven mixing of the binder, cracking during drying, and stress deformation during metal infiltration are very likely to occur. On the other hand, the traditional die-casting technology usually performs die-casting at a higher melting temperature of the molten metal. When the molten metal at high temperature contacts the ceramic particles, a chemical reaction will occur, resulting in undesirable compounds that affect the performance and quality of the composite material. If a lower molten metal melting temperature is used, the generation of undesirable compounds can be greatly reduced, but during the metal infiltration process, when the mold and the indenter contact the high-temperature molten metal, a large amount of heat from the molten metal will be absorbed, resulting in contact with the mold. The molten metal rapidly solidifies, and the solidified metal has a certain supporting force on the indenter, which greatly reduces the pressure exerted by the indenter on the molten metal. During the cooling process of the molten metal, the temperature of the core of the mold is higher than that of the outside, and the continuously decreasing pressure hinders the infiltration effect of the molten metal in the gaps of the core reinforcement particles, resulting in a higher density of each part of the composite material. Differences, especially for core composite materials, due to insufficient pressure of molten metal penetration, defects such as shrinkage porosity and pores are easily generated during the cooling process, which seriously affects the performance and quality of the product.

SUMMARY OF THE INVENTION

Aiming at the shortcomings of the above-mentioned existing production technology, the applicant provides a process for preparing metal matrix ceramic composite materials by applying secondary pressure, so as to strictly control the temperature at which the molten metal is poured into the sleeve, so that the molten metal can be melted or semi-solid solution. Infiltrating the ceramic particles in the state, avoiding the occurrence of adverse reactions between the molten metal and the ceramic particles at high temperature, and effectively improving the quality of the composite material. The gap generates negative pressure. In addition, after the first pressure holding, in order to avoid the problem of low infiltration rate caused by insufficient pressure holding of the aluminum liquid in the center of the forming die, the method of applying secondary pressure with a secondary pressure plate is adopted. It greatly improves the infiltration rate of molten aluminum, which is more conducive to the full infiltration of molten metal into the gaps of ceramic particles. The composite material thus prepared has high density and low porosity, and the quality and performance of the product are greatly improved.

The technical scheme adopted in the present invention is as follows:

A process for preparing a metal matrix ceramic composite material by applying secondary pressure, comprising a product forming die assembly, a sleeve die, a bottom plate, a press ejector and a worktable,

The worktable is installed on the press, the upper surface of the worktable is fitted with a set of molds, the middle of the set of molds is equipped with a bottom plate, the product forming mold assembly is placed above the bottom plate, and the bottom surface of the bottom plate is abutted with a bottom plate. Press ejector rod, which passes through the worktable, and moves up and down in the cavity of the sleeve mold through the lifting of the press ejector rod to control the bottom plate and the product forming die assembly;

The specific process steps are as follows:

The first step: evenly spray the release agent on the inner wall, bottom plate and upper surface of the ejector pin of the sleeve mold;

The second step: Mix and fully stir several ceramic reinforcement powders with different particle sizes to prepare the powder to be filled;

The third step: disassemble all the parts that constitute the product forming mold assembly, and spray the release agent evenly on the surface of each part;

Step 4: Assemble the parts whose surfaces have been evenly coated with release agent in the third step into a product forming die assembly;

Step 5: Fill the powder that has been stirred evenly in the second step into the cavity of the assembled product forming die assembly, vibrate and compact;

Step 6: Put the product forming mold components into the preheating furnace, preheat to 500-700 ° C, and keep the temperature for 3-5 hours, uniformly heat the product forming mold components and powder;

Step 7: The middle section of the sleeve mold is equipped with a high-frequency heater, and the high-frequency heater is activated to heat the middle section of the sleeve mold, and the heating temperature is about 200°C-500°C;

Step 8: Raise the ejector pin of the press and the bottom plate placed on the top surface of the ejector pin, the upper surface of the bottom plate is raised to be higher than the upper surface of the sleeve mold, and the preheated product forming mold assembly is placed on the upper surface of the bottom plate;

The ninth step: lower the top rod of the press, so that the bottom plate and the product forming mold components are slowly put into the sleeve mold along the inner wall of the sleeve mold, and the bottom plate is in contact with the upper surface of the worktable;

The tenth step: inject the pretreated molten metal into the inner cavity of the sleeve mold, the pouring temperature of the molten metal is controlled at 100-200°C above the melting point of the molten metal, and the molten metal floods the product forming mold components;

Step 11: There is a center hole in the middle of the bottom plate, which is connected with the air extraction channel of the press ejector. When the molten metal is injected, the external vacuum pump is turned on, and the interior of the product forming mold assembly is vacuumized from the bottom air channel to make the Negative pressure is generated inside the product forming die assembly;

The twelfth step: start the press, press down the pressure head into the sleeve mold, apply pressure to the metal liquid to infiltrate the metal liquid into the gap of the powder, maintain the pressure for 3-7 minutes, and close the external vacuum pump;

The thirteenth step: After the pressure is maintained, the temperature drops, and the molten metal in contact with the inner wall of the sleeve first becomes a solidified layer. The pressure of the head to the center of the unsolidified metal liquid;

Step 14: Press the press up button, lift the indenter, immediately place the secondary pressure plate on the center surface of the molten metal, then press down the press down button to lower the indenter. The secondary pressure plate is pressurized, so that a higher pressure is applied to the center of the molten metal for the second time, so that the molten metal can be more fully infiltrated into the gaps of the powder, and the secondary pressure is maintained for 5-12 minutes;

Step 15: After the molten metal solidifies, turn off the high-frequency heater, withdraw the indenter from the die, and lift it up to the original height;

The sixteenth step: the ejector rod of the press is raised, and the bottom plate is driven to push the metal ingot containing the product forming mold component out of the cavity of the sleeve mold;

Step 17: Perform sawing and demoulding operations on the product forming mold components, take out the blank of the metal matrix ceramic composite product, and then machine the blank according to the product requirements to obtain the final product.

Its further technical solution is:

The secondary pressing plate has a flat structure.

The secondary pressure plate has a rectangular parallelepiped structure.

The outer diameter of the head of the indenter matches the inner diameter of the die.

In the seventh step, the heating temperature of the high-frequency heater is 200°C-500°C.

The sleeve mold is a circular sleeve structure with the diameter of the chassis larger than the diameter of the cylinder.

The bottom of the bottom plate is provided with a first step, the bottom of the sleeve mold is opened with a diameter smaller than that of the top opening, and the bottom opening is provided with a second step, the first step and the second step cooperate to clamp the bottom plate.

The ceramic reinforcement powder adopts diamond powder, silicon carbide powder or silicon powder.

The central hole is communicated with the air extraction channel, the central hole is communicated with the gap of the product forming die assembly, and the air extraction channel is connected with the vacuum pump through a pipeline.

The air extraction channel is a right-angle structure.

The beneficial effects of the present invention are as follows:

The invention has compact and reasonable structure and convenient operation. The preparation process of the prefabricated part is omitted by directly filling the powder material into the product forming mold assembly; during die casting, the outer middle section of the sleeve mold adopts continuous high-frequency heating to control the temperature field of the sleeve mold. ;The product forming mold is heated and preheated, and the molten metal is poured into the sleeve mold during die-casting, so that the temperature of the molten metal inside and outside the product forming mold assembly is basically the same during the die-casting process, and the pressure inside and outside the mold is basically equal. The indenter exerts secondary pressure on the molten metal in the sleeve die, which not only avoids the deformation of the product forming die components during the die casting process and affects the dimensional accuracy of the die casting product, but also avoids the temperature difference of each part of the product forming die during die casting. Large, resulting in uneven metal penetration pressure, resulting in inconsistent performance and quality of various parts of the product.

In the process of die-casting metal, when the sleeve die and the indenter are in contact with the high-temperature molten metal, they will absorb a large amount of heat from the molten metal, causing the molten metal in contact with the die to rapidly solidify, and the solidified metal will provide a certain support for the indenter. The key problem is that the pressure exerted by the pressure head on the molten metal is greatly reduced.

The invention adopts the method of adding a second pressure plate after the first pressure application to carry out the second pressure holding and solidification, which solves the above problem well.

The invention strictly controls the temperature at which the molten metal is poured into the sleeve mold, so that the molten metal penetrates into the ceramic particles in a molten or semi-solid solution state, thereby avoiding the occurrence of adverse reactions between the molten metal and the ceramic particles (such as diamond) at high temperature, and effectively improving the At the same time, a vacuum channel is added at the bottom of the sleeve mold, which can generate negative pressure in the gap of the ceramic particles during the die-casting process. Insufficient liquid holding pressure leads to the problem of low infiltration rate. The method of using a secondary pressure pad with a secondary pressure pad can greatly improve the infiltration rate of the molten metal, which is more conducive to the full infiltration of the molten metal into the gaps of the ceramic particles. The composite material thus prepared has high density and low porosity, and the quality and performance of the product are greatly improved.

The invention not only simplifies the process of preparing the preform, avoids the problems of mold deformation, cracking of the preform, binder residue, etc., but also regulates the control by preheating the forming mold assembly before die casting and heating the sleeve during die casting. The temperature field of the molten metal and its solidification time are ensured to ensure that the molten metal can evenly penetrate into the gaps of the ceramic particles in the molten state, and the vacuum is drawn from the bottom of the mold during high-pressure die casting, so that the molten metal can penetrate downwards more smoothly. The penetration rate of the molten metal is improved. After the first pressure holding, in order to avoid the solidified metal offsetting the pressure and the pressure holding is insufficient, the second pressure is carried out to realize the true isostatic die casting.

The invention effectively realizes the control of defects in the material die casting and effective exhaust, the density, quality and performance of the composite material are greatly improved, and the mold can be reused, which provides a new idea for the mass production of metal matrix ceramic composite materials. .

Description of drawings

FIG. 1 is a schematic diagram of the matching structure of a sleeve die and a press ejector pin according to the present invention.

Figure 2 is a schematic structural diagram of the forming die after powder filling of the present invention.

FIG. 3 is a schematic diagram of the seventh step of the present invention.

FIG. 4 is a schematic diagram of the operation of the eighth step of the present invention.

FIG. 5 is a schematic diagram of the ninth step of the present invention.

FIG. 6 is a schematic diagram of the tenth step of the present invention.

FIG. 7 is a schematic diagram of the eleventh step of the present invention.

FIG. 8 is a schematic diagram of the operation of the twelfth step of the present invention.

FIG. 9 is a schematic diagram of the operation of the fourteenth step of the present invention.

FIG. 10 is a schematic diagram of the operation of the sixteenth step of the present invention.

Among them: 1. Powder; 2. Product forming mold components; 3. Bottom plate; 4. Set of molds; 5. Press ejector; 6. Workbench; ; 10. Secondary pressure plate; 11. High frequency heater; 12. Vacuum pump;

301, the center hole; 302, the first step;

401. The second step.

Detailed ways

The specific embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in Fig. 1-Fig. 10, the process for preparing metal matrix ceramic composite material by applying secondary pressure in this embodiment includes a product forming die assembly 2, a sleeve die 4, a base plate 3, a press ejector pin 5 and a worktable 6,

The worktable 6 is installed on the press, the upper surface of the worktable 6 is fitted with a sleeve mold 4, the middle of the sleeve mold 4 is equipped with a bottom plate 3, the product forming mold assembly 2 is placed above the bottom plate 3, and the bottom surface of the bottom plate 3 abuts with a base plate 3. The press mandrel 5, the press mandrel 5 passes through the table 6, and the bottom plate 3 and the product forming die assembly 2 are moved up and down in the cavity of the sleeve mold 4 through the lifting of the press mandrel 5;

The specific process steps are as follows:

The first step: evenly spray the release agent on the inner wall of the sleeve mold 4, the bottom plate 3 and the upper surface of the press ejector rod 5;

Step 2: Mix and fully stir several ceramic reinforcement powders with different particle sizes to prepare powder 1 to be filled;

The third step: disassemble all the parts that constitute the product forming die assembly 2, and spray the release agent evenly on the surface of each part;

Step 4: Assemble the parts whose surfaces have been evenly coated with release agent in the third step into a product forming die assembly 2;

Step 5: Fill the powder 1 that has been stirred evenly in the second step into the cavity of the assembled product forming die assembly 2, vibrate and compact;

Step 6: Put the product forming die assembly 2 into the preheating furnace, preheat to 500-700°C, and keep the temperature for 3-5 hours to uniformly heat the product forming die assembly 2 and the powder 1;

The seventh step: the high-frequency heater 11 is installed outside the middle section of the sleeve mold 4, and the high-frequency heater 11 is activated to heat the middle section of the sleeve mold 4, and the heating temperature is about 200°C-500°C;

The eighth step: lift up the press ejector rod 5 and the bottom plate 3 placed on the top surface of the ejector rod 5, the upper surface of the bottom plate 3 is raised to be higher than the upper surface of the sleeve mold 4, and the preheated product forming mold assembly 2 is placed. on the upper surface of the base plate 3;

The ninth step: lower the ejector rod 5 of the press, so that the bottom plate 3 together with the product forming die assembly 2 is slowly put into the sleeve mold 4 along the inner wall of the sleeve mold 4, and the bottom plate 3 is brought into contact with the upper surface of the workbench 6;

The tenth step: inject the pretreated molten metal 7 into the inner cavity of the sleeve mold 4, the pouring temperature of the molten metal 7 is controlled at 100-200°C above the melting point of the molten metal, and the molten metal 7 submerges the product forming mold assembly 2;

The eleventh step: a center hole 301 is provided in the middle of the bottom plate 3, which is communicated with the air extraction channel 8 of the press ejector rod 5. When the molten metal 7 is injected, the externally connected vacuum pump 12 is turned on, and the mold assembly 2 is formed from the bottom air channel. The interior is vacuumed to generate negative pressure inside the product forming die assembly 2;

The twelfth step: start the press, press the pressure head 9 down into the sleeve mold 4, apply pressure to the molten metal 7 to infiltrate the molten metal 7 into the gap of the powder 1, maintain the pressure for 3-7 minutes, and close the external connected vacuum pump 12;

The thirteenth step: After the pressure is maintained, the temperature drops, and the molten metal in contact with the inner wall of the sleeve die 4 first becomes a solidified layer. The pressure of the pressure head 9 to the central unsolidified metal liquid 7;

The fourteenth step: press the press up button, lift the press head 9, immediately place the secondary pressure plate 10 on the center surface of the molten metal 7, then press the press down button to lower the press head 9, The secondary pressing plate 10 is pressurized by the indenter 9, so that a higher pressure is applied to the central part of the molten metal 7 for the second time, so that the molten metal 7 is more fully infiltrated into the gap of the powder 1, and the secondary pressure is maintained for 5 -12 minutes;

The fifteenth step: after the molten metal 7 is solidified, turn off the high-frequency heater 11, and the indenter 9 exits the die set 4 and lifts up to the original height;

The sixteenth step: the ejector rod 5 of the press is raised, and the bottom plate 3 is driven to push the metal ingot containing the product forming mold assembly 2 out of the cavity of the sleeve mold 4;

Step 17: Perform sawing and demoulding operations on the product forming die assembly 2, take out the blank of the metal matrix ceramic composite product, and then machine the blank according to the product requirements to obtain the final product.

The secondary pressing plate 10 has a flat structure.

The secondary pressure plate 10 has a rectangular parallelepiped structure.

The outer diameter of the head of the indenter 9 matches the inner diameter of the sleeve mold 4 .

In the seventh step, the heating temperature of the high-frequency heater 11 is 200°C-500°C.

The sleeve mold 4 is a circular sleeve structure with the diameter of the chassis larger than the diameter of the cylinder.

The bottom of the bottom plate 3 is provided with a first step 302, the bottom of the sleeve mold 4 is provided with a diameter smaller than that of the top opening, and a second step 401 is provided at the bottom opening. The first step 302 and the second step 401 cooperate to clamp the bottom plate 3. .

The ceramic reinforcement powder adopts diamond powder, silicon carbide powder or silicon powder.

The central hole 301 communicates with the air extraction channel 8 , the central hole 301 communicates with the gap of the product forming die assembly 2 , and the air extraction channel 8 is connected to the vacuum pump 12 through a pipeline.

The air extraction channel 8 is a right-angled structure.

The area and thickness of the secondary pressing plate 10 are determined according to thermal simulation calculations.

Specific implementation one:

In the manufacturing process of the present invention, a manufacturing tool needs to be used, and its specific structure is as follows:

It mainly includes product forming die assembly 2, sleeve die 4, bottom plate 3, pressure head 9, secondary pressure plate 10 and so on.

The preheated product forming mold assembly 2 is placed on the bottom plate 3 in the cavity of the sleeve mold 4, and the bottom plate 3 with the product forming mold assembly 2 is placed on the worktable 6 in the cavity of the sleeve mold 4. The sleeve mold 4 is connected to the working table. Between the tables 6, between the press ejector rod 5 and the worktable 6, there is a sealing groove and a sealing ring is placed to seal, the press ejector rod 5 is left with an air extraction channel 8, and the bottom plate 3 is provided with a connection with the air extraction channel 8 in the middle. In the central hole 301 , the press ejector pin 5 can drive the product forming die assembly 2 to rise and fall in the cavity of the sleeve die 4 through the top and bottom plate 3 .

The molten metal 7 is poured into the cavity of the sleeve mold 4 .

The bottom plate 3 and the product forming mold assembly 2 can be moved up and down in the cavity of the sleeve mold 4 by the lifting and lowering of the ejector rod 5 of the press.

The sleeve mold 4 is a circular sleeve structure with the diameter of the bottom plate larger than the diameter of the cylinder body, and the diameter of the bottom opening is slightly smaller than the diameter of the inner wall of the cavity.

The sleeve mold 4 is a circular cylinder, the bottom opening diameter is smaller than the top opening diameter, and the bottom opening is provided with a second step 401, the bottom of the bottom plate 3 is provided with a first step 302, and the first step 302 is matched with the second step 401, The bottom plate 3 will not slide down.

The inner wall of the cavity of the sleeve mold 4 has a lower small and upper large draft slope from the height of the bottom of the product forming mold assembly to a certain height above the product forming mold assembly. Above this height until the upper end face of the opening is vertical without slope inner wall.

Process steps of the present invention are:

The first step: evenly spray the release agent on the inner wall of the sleeve mold 4, the bottom plate 3 and the upper surface of the press ejector rod 5;

Step 2: Mix and fully stir several ceramic reinforcement powders with different particle sizes to prepare powder 1 to be filled;

The third step: disassemble all the parts that constitute the product forming die assembly 2, and spray the release agent evenly on the surface of each part;

Step 4: Assemble the parts whose surfaces have been evenly coated with release agent in the third step into a product forming die assembly 2;

Step 5: Fill the powder 1 that has been stirred evenly in the second step into the cavity of the assembled product forming die assembly 2, vibrate and compact;

The sixth step: put the product forming mold assembly 2 into the preheating furnace, preheat to 500-700 ° C, and keep the temperature for 3-5 hours, uniformly heat the product forming mold assembly 2 and the powder 1;

The seventh step: the middle section of the sleeve mold 4 is equipped with a high-frequency heater 11, and the high-frequency heater 11 is activated to heat the middle section of the sleeve mold 4, and the heating temperature is about 200°C-500°C;

Step 8: Raise the press ejector pin 5 and the bottom plate 3 placed on the top surface of the ejector pin, the upper surface of the bottom plate 3 is raised to be higher than the upper surface of the sleeve mold 4, and the preheated product forming mold assembly 2 is placed on the bottom. the upper surface of the plate 3;

The ninth step: lower the ejector rod 5 of the press, so that the bottom plate 3 together with the product forming die assembly 2 is slowly put into the sleeve mold 4 along the inner wall of the sleeve mold 4, and the bottom plate 3 is brought into contact with the upper surface of the workbench 6;

The tenth step: inject the pretreated molten metal 7 into the inner cavity of the sleeve mold 4, the pouring temperature of the molten metal 7 is controlled at 100-200°C above the melting point of the molten metal, and the molten metal 7 submerges the product forming mold assembly 2;

The eleventh step: a center hole 301 is provided in the middle of the bottom plate 3, which is communicated with the air extraction channel 8 of the press ejector rod 5. When the molten metal 7 is injected, the externally connected vacuum pump 12 is turned on, and the mold assembly 2 is formed from the bottom air channel. The interior is vacuumed to generate negative pressure inside the product forming die assembly 2;

The twelfth step: start the press, press the pressure head 9 down into the sleeve mold 4, apply pressure to the molten metal 7 to infiltrate the molten metal 7 into the gap of the powder 1, maintain the pressure for 3-7 minutes, and close the external connected vacuum pump 12;

The thirteenth step: After the pressure is maintained, the temperature drops, and the molten metal in contact with the inner wall of the sleeve mold 4 first becomes a solidified layer. The pressure of the pressure head 9 to the central unsolidified metal liquid 7;

The fourteenth step: press the press up button, lift the press head 9, immediately place the secondary pressure plate 10 on the center surface of the molten metal 7, then press the press down button to lower the press head 9, The secondary pressing plate 10 is pressurized by the indenter 9, so that a higher pressure is applied to the center of the molten metal 7 for the second time, so that the molten metal 7 is more fully infiltrated into the gap of the powder 1, and the secondary pressure is maintained for 5 -12 minutes;

The fifteenth step: after the molten metal 7 is solidified, turn off the high-frequency heater 11, and the indenter 9 exits the die set 4 and lifts up to the original height;

The sixteenth step: the ejector rod 5 of the press is raised, and the bottom plate 3 is driven to push the metal ingot 7 containing the product forming mold assembly 2 out of the cavity of the sleeve mold 4;

Step 17: Perform sawing and demoulding operations on the product forming die assembly 2, take out the blank of the metal matrix ceramic composite product, and then machine the blank according to the product requirements to obtain the final product.

Embodiment 2: The difference between this embodiment and Embodiment 1 is that the ceramic reinforcement powder in the second step is diamond powder, the preheating temperature in the sixth step is 500-600°C, the holding time is 3h, and the other The specific embodiment one is the same.

Embodiment 3: The difference between this embodiment and Embodiment 1 is: in the second step, the ceramic reinforcement powder is silicon carbide powder, in the sixth step, the preheating temperature is 600-700°C, and the holding time is 4h. It is the same as the specific embodiment 1.

Embodiment 4: The difference between this embodiment and Embodiment 1 is that the ceramic reinforcement powder in the second step is silicon powder, the preheating temperature in the sixth step is 500-700°C, and the holding time is 5h. It is the same as the specific embodiment 1.

The invention is simple to operate, effectively realizes the control of defects in the material die-casting and the effective exhaust by means of twice pressurization, and greatly improves the density, quality and performance of the composite material.

The above description is an explanation of the present invention, not a limitation of the present invention. For the limited scope of the present invention, refer to the claims, and any form of modification can be made within the protection scope of the present invention.

Claims (9)

1. A process for preparing a metal matrix ceramic composite material by secondary pressure application is characterized in that: comprises a product forming die assembly (2), a cover die (4), a bottom plate (3), a press ejector rod (5) and a workbench (6),

the device comprises a workbench (6), a sleeve die (4), a bottom plate (3), a product forming die assembly (2), a press ejector rod (5) and a product forming die assembly (2), wherein the workbench (6) is installed on a press, the upper surface of the workbench (6) is provided with the sleeve die (4) in a matching manner, the middle part of the sleeve die (4) is provided with the bottom plate (3) in a matching manner, the product forming die assembly (2) is placed above the bottom plate (3), the bottom surface of the bottom plate (3) is abutted to the press ejector rod (5), and the bottom plate (3) and the product forming die assembly (2) are controlled to move up and down in a cavity of the sleeve die (4) through the lifting of the press ejector rod (5);

the specific process steps are as follows:

the first step is as follows: uniformly spraying a release agent on the inner wall of the cover die (4), the bottom plate (3) and the upper surface of the press ejector rod (5);

the second step is that: mixing and fully stirring a plurality of ceramic reinforcement powder with different particle sizes to prepare powder (1) to be filled;

the third step: all parts forming the product forming die assembly (2) are disassembled, and a release agent is uniformly sprayed on the surface of each part;

the fourth step: assembling the parts of which the surfaces are uniformly coated with the release agent in the third step into a product forming die assembly (2);

the fifth step: filling the uniformly stirred powder (1) in the second step into a cavity of an assembled product forming die assembly (2), vibrating and compacting;

and a sixth step: placing the product forming mold assembly (2) into a preheating furnace, preheating to 500-;

the seventh step: a high-frequency heater (11) is arranged outside the middle section of the sleeve die (4), the high-frequency heater (11) is started, and the middle section of the sleeve die (4) is heated at the temperature of 200-500 ℃;

eighth step: lifting a press ejector rod (5) and a bottom plate (3) arranged on the top surface of the press ejector rod (5), lifting the upper surface of the bottom plate (3) to be higher than the upper surface of a sleeve mold (4), and placing a preheated product forming mold assembly (2) on the upper surface of the bottom plate (3);

the ninth step: a press ejector rod (5) is lowered, so that the bottom plate (3) and the product forming die assembly (2) are slowly placed into the sleeve die (4) along the inner wall of the sleeve die (4), and the bottom plate (3) is in contact with the upper surface of the workbench (6);

the tenth step: injecting the pretreated molten metal (7) into the inner cavity of the cover die (4), controlling the pouring temperature of the molten metal (7) to be 100-200 ℃ above the melting point of the molten metal, and submerging the product forming die assembly (2) by the molten metal (7);

the eleventh step: the middle part of the bottom plate (3) is provided with a central hole (301) which is communicated with an air exhaust channel (8) of a press ejector rod (5), when metal liquid (7) is injected, a vacuum pump (12) which is externally connected is started, and the interior of the product forming mold assembly (2) is vacuumized from a bottom air passage, so that negative pressure is generated in the product forming mold assembly (2);

the twelfth step: starting a press, descending a pressure head (9) to press into a sleeve die (4), applying pressure to molten metal (7) to enable the molten metal (7) to be impregnated into the gaps of the powder (1), maintaining the pressure for 3-7 minutes, and closing an externally connected vacuum pump (12);

the thirteenth step: after pressure maintaining, the temperature is reduced, the molten metal in contact with the inner wall of the cover die (4) is firstly changed into a solidified layer which is annular and forms reverse supporting force for a press head (9) of a press, and the pressure of the press head (9) to the central unsolidified molten metal (7) is reduced;

the fourteenth step is that: pressing a press lifting button, lifting a pressure head (9), immediately placing a secondary pressurizing plate (10) on the central surface of molten metal (7), immediately pressing a press descending button, descending the pressure head (9), pressurizing the secondary pressurizing plate (10) through the pressure head (9), and thus applying higher pressure to the central part of the molten metal (7) for the second time to enable the molten metal (7) to be more fully infiltrated into the gaps of the powder material (1), and maintaining the pressure for the second time for 5-12 minutes;

the fifteenth step: after the molten metal (7) is solidified, the high-frequency heater (11) is closed, the pressure head (9) is withdrawn from the cover die (4) and lifted to the original height;

sixteenth, step: the ejector rod (5) of the press rises to drive the bottom plate (3) to eject the metal ingot containing the product forming die assembly (2) out of the cavity of the sleeve die (4);

seventeenth step: and (3) performing saw cutting and demoulding operation on the product forming die assembly (2), taking out a blank of the metal matrix ceramic composite material product, and machining the blank according to the product requirement to obtain a final product.

2. The process for preparing a metal matrix ceramic composite material by secondary pressing according to claim 1, wherein: the secondary pressurizing plate (10) is of a flat structure.

3. The process for preparing a metal matrix ceramic composite material by secondary pressing according to claim 1, wherein: the secondary pressurizing plate (10) is of a cuboid structure.

4. The process for preparing a metal matrix ceramic composite material by secondary pressing according to claim 1, wherein: the outer diameter of the head part of the pressure head (9) is matched with the inner diameter of the cover die (4).

5. The process for preparing a metal matrix ceramic composite material by secondary pressing according to claim 1, wherein: the cover die (4) is of a circular sleeve structure with the diameter of the bottom plate larger than that of the cylinder body.

6. The process for preparing a metal matrix ceramic composite material by secondary pressing according to claim 1, wherein: the bottom of bottom plate (3) is provided with first step (302), and the bottom opening diameter of cover mould (4) is less than top opening diameter, and the bottom opening part is provided with second step (401), first step (302) and second step (401) cooperation are blocked bottom plate (3).

7. The process for preparing a metal matrix ceramic composite material by secondary pressing according to claim 1, wherein: the ceramic reinforcement powder adopts diamond powder, silicon carbide powder or silicon powder.

8. The process for preparing a metal matrix ceramic composite material by secondary pressing according to claim 1, wherein: the central hole (301) is communicated with an air exhaust channel (8), the central hole (301) is communicated with a gap of the product forming die assembly (2), and the air exhaust channel (8) is connected with a vacuum pump (12) through a pipeline.

9. The process for preparing a metal matrix ceramic composite material by secondary pressing according to claim 8, wherein: the air exhaust channel (8) is of a right-angle structure.

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