CN103540873B - Liquid-state near-net forming method and device for continuous carbon fiber enhanced aluminum-based composite material - Google Patents

Abstract

The invention discloses a liquid-state near-net forming method and device for continuous carbon fiber reinforced aluminum-based composite materials (namely: vacuum-assisted pressure-regulating infiltration casting method and device). Infiltration, high-pressure solidification and rapid cooling are four processes. The device is composed of an alloy melting device, a vacuum-assisted pressure regulating impregnation device and a casting rapid cooling device. The characteristics of the present invention are: (1) low-oxygen temperature-controlled preheating of nickel-plated carbon fibers; (2) low-pressure impregnation and high-pressure solidification of aluminum matrix composites; (3) solidification of composite castings Cooling rate control. The invention solves the problems of oxidative burning loss during carbon fiber preheating, preform deformation during impregnation and interface reaction during solidification of composite materials. The invention can realize the liquid near-net shape of the continuous carbon fiber reinforced aluminum matrix composite material, and the prepared composite material has the advantages of compact structure, less interface reaction, high mechanical performance and the like.

Description

A liquid near-net-shaping method and device for continuous carbon fiber reinforced aluminum matrix composites

technical field

The invention belongs to the field of liquid near-net forming of high-performance metal-based composite materials, and in particular relates to a method and device for liquid-state near-net forming of continuous carbon fiber reinforced aluminum-based composite materials.

Background technique

Carbon fiber continuous reinforced aluminum matrix composites have excellent mechanical and physical properties, and have broad application prospects in high-tech engineering fields such as aerospace and advanced weapons. At present, the main preparation methods of this composite material are: solid-state high-temperature diffusion bonding method, extrusion Casting method, vacuum suction casting method and vacuum pressure infiltration method. Among them, the high-temperature diffusion bonding method has the advantages of less damage to fibers and strong designability of composite materials. The disadvantages are: complex process and high production cost; squeeze casting method has high composite pressure, complete liquid infiltration, can eliminate pores and Shrinkage cavity and other defects, improving the mechanical properties of composite materials, etc., but the disadvantages are: the shape of the casting is limited, it is difficult to achieve near-net shape, and the preform is easy to be damaged and cracked under high pressure, resulting in casting defects; the vacuum suction casting method can reduce the composite material. The occurrence of casting defects such as bubbles and inclusions in the material, the vacuum environment can also avoid the oxidation of aluminum liquid and fibers, but the disadvantages are: the wettability of fibers and aluminum liquid is poor, and high-temperature aluminum liquid is prone to serious interface reactions with fibers and damage Composite properties. The advantage of the vacuum pressure infiltration method is that the preparation process is simple, composite parts with complex shapes can be prepared, and the near-net shape of the composite material can be realized. Surface modification of carbon fibers to improve their wettability with molten aluminum and control interfacial reactions.

The above preparation methods have their own characteristics. Generally speaking, for the preparation of continuous fiber reinforced aluminum matrix composites, the vacuum pressure infiltration method has the advantages of simple preparation process, easy pressure control, not easy to cause deformation and damage of the preform, and can achieve near net shape. And other advantages, so it is suitable for the manufacture of complex precision parts with high performance requirements. In order to solve the problem of low wettability of carbon fiber and molten aluminum in vacuum pressure infiltration and control the interface reaction between the two, it is generally necessary to modify the surface of carbon fiber, and surface nickel plating is an ideal surface modification of carbon fiber. sexual method. However, the current vacuum pressure infiltration process of carbon fiber reinforced aluminum matrix composites has the following two deficiencies: (1) Surface oxidation and burning during preheating of nickel-plated carbon fibers not only damage the properties of the fiber itself, but also reduce its contact with aluminum The wettability of the liquid makes it difficult to prepare by low-pressure impregnation; (2) The contact time between the nickel-plated carbon fiber and the aluminum liquid is long at high temperature, and serious interface reactions will occur, which not only damages the integrity and performance of the fiber itself, but also easily generates a large amount of The interfacial brittle phase deteriorates the mechanical properties of the composite.

Invention content:

The first object of the present invention is to provide a liquid-state near-net forming method for continuous carbon fiber-reinforced aluminum matrix composites (i.e., vacuum-assisted pressure-regulating infiltration casting method), which solves the problems of high-temperature oxidation damage on the surface of carbon fibers and control of interface reactions. The two problems help to improve the density and integrity of composite materials, improve the mechanical properties of composite materials, and reduce their preparation costs, laying a technical foundation for the preparation of high-performance carbon fiber continuous reinforced aluminum matrix composites in liquid near-net shape.

The second object of the present invention is to provide a liquid near-net-shaping device for continuous carbon fiber reinforced aluminum matrix composites (namely: a vacuum-assisted pressure regulating infiltration casting device).

First purpose of the present invention is achieved like this:

A liquid near-net forming method for continuous carbon fiber reinforced aluminum matrix composites, characterized in that the steps are as follows:

A. According to the requirement of fiber volume fraction 35%-55%, prepare continuous carbon fiber prefabricated body, quantitatively cut aluminum alloy ingot to obtain matrix aluminum alloy, put carbon fiber prefabricated body and matrix aluminum alloy into mold and crucible respectively, and put the whole After the device is connected and sealed, perform an air tightness check;

B. Fiber preheating and alloy melting: Turn on the crucible heater and mold heater for aluminum alloy melting and carbon fiber preheating at the same time, open the vacuum pump valve and mold valve, and simultaneously evacuate the crucible and mold and maintain the air pressure of both Balance, when the vacuum of the crucible air pipe pressure gauge and the casting mold air pipe pressure gauge reaches 5-10Pa, stop vacuuming, close the vacuum pump valve, open the argon valve to feed high-purity argon gas into the crucible and mold, and the crucible air pipe pressure After the argon pressure of the gauge and cast air pipe pressure gauge reaches 20-30KPa, close the argon valve and keep the pressure for 10-20 minutes; open the vacuum pump valve to vacuum to a vacuum degree of 5-10Pa, then close the vacuum pump valve and open the argon valve Infuse argon and maintain the pressure. After reaching 20-30KPa, close the argon valve and maintain the pressure for 10-20 minutes. Repeat the above steps. By alternately vacuuming and argon, alloy melting and Fiber preheating, until the end of alloy melting and fiber preheating, the melting temperature of aluminum alloy is controlled by crucible thermocouple to 650-800°C, and the preheating temperature of carbon fiber is controlled by casting thermocouple to 400-650°C;

C. Vacuum-assisted air pressure infiltration: heat the aluminum alloy to 50-100°C above the liquidus temperature, and heat the carbon fiber preform to 400-650°C. After both are kept warm for 1 hour, turn off the crucible heater and the mold heater. Close the argon gas valve, open the vacuum pump valve, and evacuate the crucible and the mold at the same time to maintain the same environmental vacuum degree. Mold valve: open the argon valve, and pass argon gas with a pressure of 200-500KPa to the liquid surface of the aluminum melt in the crucible. Into the carbon fiber prefabricated body in the mold and fill the gaps of carbon fiber to realize the composite of aluminum alloy and carbon fiber, and complete the vacuum-assisted low-pressure infiltration of composite materials;

D. High-pressure solidification forming: Monitor the temperature change of the mold wall during the vacuum low-pressure impregnation process through the temperature changes of several mold thermocouples embedded in the mold wall. After the low-pressure impregnation is completed, adjust the argon valve to make the effect The argon pressure on the liquid surface of the aluminum melt in the crucible rises to 800-1000KPa, and at the same time, remove the mold heater and open the cooling water valve, and feed cooling water into the cooling water jacket, through which the cooling water in the mold The composite material casting is cooled rapidly, the cooling rate of the composite material casting is monitored by the mold thermocouple, the cooling rate of the composite material casting is controlled by adjusting the flow rate of the cooling water pump, and the degree of interface reaction between carbon fiber and aluminum alloy is controlled;

E. After the composite casting is cooled to room temperature, open the sealing connection bolts between the casting mold and the mold gas pipe, cooling water jacket, and liquid riser, remove the casting mold and demould, and obtain a continuous carbon fiber reinforced aluminum matrix composite casting.

In step B, the oxygen content in the crucible and the mold is controlled by alternately vacuuming and feeding high-purity argon, so as to realize the protection of the nickel-plated carbon fiber at high temperature.

The second purpose of the present invention is achieved like this:

A liquid near-net forming device for continuous carbon fiber reinforced aluminum-based composite materials, characterized by: including a crucible and a mold, the outer wall of the crucible containing aluminum alloy is covered with a crucible heater, and a sealing cover is fixed on the top edge of the crucible , the detection end of the crucible thermocouple passes through the crucible heater from the outside to the inside and is embedded in the wall of the crucible; the mold heater is installed on the sealing cover of the crucible, and the mold containing the carbon fiber preform is located on the mold heater In the mold, there is a cooling water jacket around the outer wall of the mold. One end of the cooling water jacket is connected to the circulating water tank, and the other end of the cooling water jacket is connected to the cooling water pump with a cooling water valve. Several mold thermocouples arranged in parallel up and down The detection ends of the detectors pass through the mold heater from the outside to the inside and are embedded in the wall of the mold; one end of the crucible air pipe with a crucible air pipe pressure gauge extends downward into the crucible through the sealing cover of the crucible, and the end of the crucible air pipe The other end is connected to the first port of the four-way connecting pipe, the suction end of the vacuum pump is connected to the second port of the four-way connecting pipe through the vacuum pump valve, the outlet end of the argon tank is connected to the end of the four-way connecting pipe through the argon valve. The third interface is connected. One end of the cast air pipe with cast air pipe pressure gauge extends downwards into the crucible, and the other end of the cast air pipe is connected to the fourth port of the four-way connecting pipe after being connected in series with the cast valve. The upper end of the liquid riser is connected to the bottom of the casting mold, and the lower end of the liquid riser passes downward through the sealing cover plate of the crucible and extends into the molten aluminum in the crucible.

Compared with the traditional method for preparing carbon fiber reinforced aluminum matrix composites, the method and device adopted in the present invention are characterized in that: (1) low-oxygen temperature-controlled preheating of nickel-plated carbon fibers is realized; (2) aluminum The preparation of low-pressure infiltration and high-pressure solidification of matrix composites; (3) Realized the cooling rate control in the solidification of composite castings. The invention solves the problems of oxidative burning loss during carbon fiber preheating, preform deformation during impregnation and interface reaction during solidification of composite materials.

The control of the preheating atmosphere of the carbon fiber and the control of the cooling process of the composite material casting are realized. On the one hand, the preheating atmosphere control avoids the oxidation and ablation at high temperature during the carbon fiber preheating process, ensures the integrity of the carbon fiber itself, and avoids damage to its mechanical properties; Wettability between aluminum melts, reducing liquid infiltration resistance, reducing fiber segregation and preform deformation; controlling the cooling process of composite materials can inhibit excessive interfacial reaction between C/Al, reduce damage to carbon fibers, and control interface Al ₄ The quantity and morphology of C ₃ brittle phases are helpful to improve the mechanical properties of composites. In addition, increasing the cooling rate of the composite material is beneficial to refine the matrix structure and further improve the mechanical properties of the composite material.

Using the method and device to prepare continuous carbon fiber reinforced aluminum matrix composites has the advantages of controllable process parameters, high process integration and low cost. At the same time, composite castings have excellent microstructure and mechanical properties, which can solve the problem of continuous carbon fiber reinforced aluminum matrix composites in the field of engineering applications. Technical problems of liquid near-net shape of fiber-reinforced metal matrix composites.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Figure 2 is a schematic diagram of a unidirectional continuously reinforced C _f /Al composite product;

Figure 3 is a microscopic schematic diagram of the microstructure of unidirectional continuous reinforced C _f /Al composites, in which : (a) vertical fiber bundles; (b) parallel fiber bundles;

Fig. 4 is a schematic diagram of the microstructure and morphology of the three-dimensional four-way continuously reinforced C _f /Al composite material.

Detailed ways:

The method of the present invention will be further described below in conjunction with the examples.

A liquid near-net forming method for continuous carbon fiber reinforced aluminum matrix composites, the steps are as follows:

A. According to the requirement of fiber volume fraction 35%-55%, prepare continuous carbon fiber prefabricated body, quantitatively cut aluminum alloy ingot to obtain matrix aluminum alloy, put carbon fiber prefabricated body and matrix aluminum alloy into mold and crucible respectively, and put the whole After the device is connected and sealed, perform an air tightness check;

B. Fiber preheating and alloy melting: Turn on the crucible heater and mold heater for aluminum alloy melting and carbon fiber preheating at the same time, open the vacuum pump valve and mold valve, and simultaneously evacuate the crucible and mold and maintain the air pressure of both Balance, when the vacuum of the crucible air pipe pressure gauge and the casting mold air pipe pressure gauge reaches 5-10Pa, stop vacuuming, close the vacuum pump valve, open the argon valve to feed high-purity argon gas into the crucible and mold, and the crucible air pipe pressure After the argon pressure of the gauge and cast air pipe pressure gauge reaches 20-30KPa, close the argon valve and keep the pressure for 10-20 minutes; open the vacuum pump valve to vacuum to a vacuum degree of 5-10Pa, then close the vacuum pump valve and open the argon valve Infuse argon and maintain the pressure. After reaching 20-30KPa, close the argon valve and maintain the pressure for 10-20 minutes. Repeat the above steps. By alternately vacuuming and argon, alloy melting and Fiber preheating, until the end of alloy melting and fiber preheating, the melting temperature of aluminum alloy is controlled by crucible thermocouple to 650-800°C, and the preheating temperature of carbon fiber is controlled by casting thermocouple to 400-650°C;

C. Vacuum-assisted air pressure infiltration: heat the aluminum alloy to 50-100°C above the liquidus temperature, and heat the carbon fiber preform to 400-650°C. After both are kept warm for 1 hour, turn off the crucible heater and the mold heater. Close the argon gas valve, open the vacuum pump valve, and evacuate the crucible and the mold at the same time to maintain the same environmental vacuum degree. Mold valve: open the argon valve, and pass argon gas with a pressure of 200-500KPa to the liquid surface of the aluminum melt in the crucible. Into the carbon fiber prefabricated body in the mold and fill the gaps of carbon fiber to realize the composite of aluminum alloy and carbon fiber, and complete the vacuum-assisted low-pressure infiltration of composite materials;

D. High-pressure solidification forming: Monitor the temperature change of the mold wall during the vacuum low-pressure impregnation process through the temperature changes of several mold thermocouples embedded in the mold wall. After the low-pressure impregnation is completed, adjust the argon valve to make the effect The argon pressure on the liquid surface of the aluminum melt in the crucible rises to 800-1000KPa, and at the same time, remove the mold heater and open the cooling water valve, and feed cooling water into the cooling water jacket, through which the cooling water in the mold The composite material casting is cooled rapidly, the cooling rate of the composite material casting is monitored by the mold thermocouple, the cooling rate of the composite material casting is controlled by adjusting the flow rate of the cooling water pump, and the degree of interface reaction between carbon fiber and aluminum alloy is controlled;

E. After the composite casting is cooled to room temperature, open the sealing connection bolts between the casting mold and the mold gas pipe, cooling water jacket, and liquid riser, remove the casting mold and demould, and obtain a continuous carbon fiber reinforced aluminum matrix composite casting.

In step B, the oxygen content in the crucible and the mold is controlled by alternately vacuuming and feeding high-purity argon, so as to realize the protection of the nickel-plated carbon fiber at high temperature.

A liquid near-net forming device for continuous carbon fiber reinforced aluminum-based composite materials, including a crucible 15 and a mold 22, the outer wall of the crucible 15 containing aluminum alloy is covered with a crucible heater 18, and a seal is fixed on the top edge of the crucible 15 The cover plate 19, the detection end of the crucible thermocouple 16 passes through the crucible heater 18 from the outside to the inside and is embedded in the wall of the crucible 15; the mold heater 23 is installed on the sealing cover plate 19 of the crucible 15, and contains a carbon fiber preform The mold 22 is located in the mold heater 23, the outer wall of the mold 22 is surrounded by a cooling water jacket 24, one end of the cooling water jacket 24 is connected to the circulating water tank 11, and the other end of the cooling water jacket 24 is connected to the The cooling water pump 8 of 21 is connected, and the detection ends of the three mold thermocouples 12, 13, 14 arranged in parallel up and down all pass through the mold heater 23 from the outside to the inside and are embedded in the wall of the mold 22; One end of the crucible gas pipe 20 of the pressure gauge 7 extends downward into the crucible 15 through the sealing cover plate 19 of the crucible 15, and the other end of the crucible gas pipe 20 is connected to the first interface of the four-way connecting pipe 4, and the suction of the vacuum pump 6 The gas end is connected to the second interface of the four-way connecting pipe 4 through the vacuum pump valve 5, and the gas outlet end of the argon gas tank 1 is connected to the third interface of the four-way connecting pipe 4 through the argon valve 2, with cast air pipe pressure gauge One end of the casting air pipe 10 of 9 extends downwards into the casting mold 22, and the other end of the casting air pipe 10 is connected with the fourth interface of the four-way connecting pipe 4 after the other end of the casting air pipe 10 is connected in series with the casting air pipe valve 3, and the liquid lifting pipe 17 The upper end of the upper end is connected with the bottom of the casting mold 22, and the lower end of the liquid riser 17 passes through the sealing cover plate 19 of the crucible 15 and extends into the aluminum liquid in the crucible 15. The molten aluminum in the crucible 15 enters the fiber preform of the mold 22 through the riser 17 under the pressure difference between the crucible and the mold. Adjusting the air pressure in the crucible 15 can complete the process of low-pressure liquid infiltration and high-pressure solidification.

Example 1:

In this embodiment, continuous carbon fibers are arranged in parallel and placed in a quartz tube to make a unidirectional fiber prefabricated body, and the unidirectional continuous reinforced C _f /Al composite material is formed by vacuum-assisted pressure regulation infiltration casting with a near-net shape, and the volume fraction of carbon fibers is 35%. , the aluminum alloy volume fraction is 65%. The nearly net-shaped continuous carbon fiber unidirectionally reinforced aluminum matrix composite product is shown in Figure 2, and its microstructure is shown in Figure 3.

3K nickel-plated carbon fiber T300 is selected, and aluminum alloy is selected ZL114A.

Example 2:

In this embodiment, the continuous carbon fiber is woven into a prefabricated body through three-dimensional four-way, and the three-dimensional four-way continuous reinforced C _f /Al composite material is formed by vacuum-assisted pressure regulation and infiltration casting. The volume fraction of carbon fiber is 45%, and the volume fraction of aluminum alloy is 45%. 55%. The microstructure of the prepared composite material is shown in Fig. 4.

Example 3:

In this embodiment, the continuous carbon fiber is woven into a prefabricated body through three-dimensional and four-way, and the C/Al composite material is formed by vacuum-assisted pressure regulation and infiltration casting. The volume fraction of carbon fiber is 55%, and the volume fraction of aluminum alloy is 45%.

Claims (2)

1. continuous carbon fibre strengthens a liquid near-net-shape method for aluminium base multiple material, it is characterized in that: step is as follows:

A, requirement according to fiber volume fraction 35%-55%, prepare continuous carbon fibre precast body, quantitatively cut aluminum alloy ingot and obtain aluminum matrix alloy, carbon fabric perform and aluminum matrix alloy be respectively charged in casting mold and in crucible, whole device connected the laggard row airtight test of sealing;

B, fiber preheating and alloy melting: open crucible heater and casting mold well heater carries out aluminium alloy smelting and carbon fiber preheating simultaneously, open vacuum pump valve and casting mold valve, crucible and casting mold are vacuumized and air pressure balance both keeping simultaneously, stop vacuumizing after the vacuum tightness of crucible tracheal pressure table and casting mold tracheal pressure table reaches 5-10Pa, close vacuum pump valve, open argon gas valve and pass into highly purified argon gas in crucible and casting mold, after the argon pressure of crucible tracheal pressure table and casting mold tracheal pressure table reaches 20-30KPa, close argon gas valve and keep pressure 10-20 minute, open vacuum pump valve and be evacuated to vacuum tightness 5-10Pa, then vacuum pump valve is closed, open argon gas valve and pass into argon gas and pressurize, after 20-30KPa, close argon gas valve and keep pressure 10-20 minute, repeat above step, by vacuumizing and the hocketing of logical argon gas, realize the alloy melting under hypoxic atmosphere and fiber preheating, until alloy melting and fiber preheating terminate, controlled the smelting temperature 650-800 DEG C of aluminium alloy by crucible thermopair, controlled the preheating temperature 400-650 DEG C of carbon fiber by casting mold thermopair,

C, vacuum aided gas pressure infiltration: aluminium alloy is heated to the above 50-100 DEG C of liquidus temperature, carbon fabric perform is heated to 400-650 DEG C, after the two is all incubated 1 hour, closing crucible well heater and casting mold well heater, close argon gas valve, open vacuum pump valve, crucible and casting mold are vacuumized simultaneously, the environment vacuum degree that both maintenances are identical, the vacuum tightness of crucible tracheal pressure table and casting mold tracheal pressure table, to 5-10Pa, closes vacuum pump valve and casting mold valve; Open argon gas valve, the argon gas that pressure is 200-500KPa is passed into the molten aluminium liquid level in crucible, under the differential pressure action of crucible and casting mold, make high temperature aluminum liquid with in controlled pressure permeation to the carbon fabric perform in casting mold and the space of filling carbon fiber, realize the compound of aluminium alloy and carbon fiber, complete the vacuum aided low pressure infiltration of matrix material;

D, High Pressure Solidification is shaped: the temperature variation being embedded mould wall in the temperature variation monitoring vacuum low-pressure infiltration process of the casting mold thermopair in mould wall by several, after low pressure infiltration terminates, regulate argon gas valve, the argon pressure of the molten aluminium liquid level acted in crucible is made to rise to 800-1000KPa, remove casting mold well heater simultaneously and open cooling water valve, water coolant is passed in watercooling jacket, by watercooling jacket, the composite castings in casting mold is cooled fast, by casting mold thermocouple monitoring composite castings rate of cooling, by regulating the speed of cooling of the flow control composite castings of cooling-water pump, control the surface reaction degree between carbon fiber and aluminium alloy,

After E, composite castings are cooled to room temperature, open the bolt that is tightly connected between casting mold and casting mold tracheae, watercooling jacket, riser pipe, take off the casting mold demoulding, obtain continuous carbon fibre reinforced aluminum matrix composites foundry goods.

2. liquid near-net-shape method according to claim 1, is characterized in that: in stepb, by vacuumizing and pass into the mode that high-purity argon gas hockets, controls the oxygen level in crucible and casting mold, realizes the protection to nickel-coated carbon fibers under high temperature.