CN115044843B - A method for preparing rolled carbon fiber reinforced aluminum alloy composite materials - Google Patents

Abstract

The invention relates to the technical field of carbon fiber reinforced aluminum matrix composite materials, in particular to a preparation method of rolled carbon fiber reinforced aluminum alloy. The structural design method comprises the following steps: firstly, wrapping metal tin around the carbon fiber cloth folded into the corrugated shape to form a tin-wrapped carbon fiber corrugated interlayer; and then implanting the interlayer into an aluminum alloy matrix to construct a tin-coated corrugated carbon fiber reinforced aluminum matrix composite ingot, wherein the volume content of tin is Sn/(Al+Sn) =0.020. Then hot rolling the cast ingot, wherein the metal tin is in a liquid state in the hot rolling process and is extruded into the carbon fiber bundles, so that the load on the carbon fiber cloth can be released to a greater extent, the stress concentration on the carbon fiber cloth is effectively overcome, and the fiber damage is reduced; the fluidity of the liquid state gives the carbon fiber cloth a relatively free distribution condition, and can promote the cooperative extension of the corrugated carbon fiber coupled aluminum alloy. Finally, carrying out multistage heat treatment to enable tin and aluminum alloy to be in solid solution, eliminating redundant metallic tin, and further enhancing the mechanical properties of the composite material. The tin-coated corrugated carbon fiber-aluminum alloy multilayer structure is constructed, so that the carbon fiber and aluminum alloy matrix cooperatively extend, the integrity of the carbon fiber in the rolling process is protected, and technical support can be provided for novel light-weight high-strength carbon fiber reinforced aluminum-based composite in aerospace in China.

Description

A method for preparing rolled carbon fiber reinforced aluminum alloy composite materials

Technical field

The invention relates to a method for preparing rolled carbon fiber reinforced aluminum alloy composite materials and belongs to the technical field of special structure composite material preparation.

Background technique

Compared with traditional structural materials, aluminum alloys have been widely used in aerospace, automotive industry, civil engineering and other fields due to their lightweight, high strength and excellent corrosion resistance. With the rapid development of science and technology and increasingly fierce market competition, my country's aluminum-based composite materials field is also facing huge challenges. Innovative design and preparation problems of new lightweight and high-strength aluminum matrix composite materials need to be solved urgently to adapt to their increasingly extreme service environments.

As a new and excellent strategic material, carbon fiber has the advantages of high modulus, high strength, light weight, high temperature resistance, and corrosion resistance. Its density is only a quarter of steel, but its strength is 5 to 7 times that of steel. Compared with aluminum alloy, its weight reduction effect can reach 20% to 40%. Carbon fiber reinforced aluminum matrix composite materials have excellent properties such as high specific strength, specific stiffness, specific modulus, low thermal expansion coefficient, good electrical and thermal conductivity, and good impact toughness, and have broad application prospects in aerospace and other fields. my country's increasingly frequent aerospace activities have put forward new requirements for the damage resistance and load-bearing capacity of carbon fiber reinforced aluminum matrix composites. At present, carbon fiber reinforced aluminum matrix composite materials are divided into two types: cast state and rolled state, and the mechanical properties and damage resistance of the rolled state are better than those of the cast state. The fuselage skin, satellite mount, antenna frame, etc. are all made of rolled aluminum matrix composite materials. However, a common problem with rolled carbon fiber reinforced aluminum matrix composites is that stress concentration is prone to occur on the carbon fiber cloth, leading to premature fracture and failure of the carbon fiber cloth. Researchers have solved the problem of ductility difference between carbon fiber cloth and aluminum matrix by designing corrugated carbon fiber reinforced aluminum matrix composite materials (patent country: China, patent publication number: CN111085674A, patent publication date: 2020.05.01). This kind of The design can achieve synergistic extension between the continuous carbon fiber cloth and the aluminum matrix, but it cannot avoid the problem of damage to the carbon fiber cloth due to shear loads during the rolling process, nor can it prevent stress concentration on the surface of the carbon fiber cloth, so it is not fundamentally Solve the problem of carbon fiber cloth damage during the rolling deformation process of composite materials.

Contents of the invention

(1) Key issues to be solved

What this invention aims to solve is the problem that carbon fiber reinforced aluminum matrix composite materials are prone to fracture and failure during plastic deformation. Based on the previous method of folding carbon fiber cloth into a corrugated shape and directly implanting it into an aluminum alloy matrix to achieve synergistic extension of the reinforcement phase and the alloy matrix, the present invention provides a tin-coated corrugated carbon fiber cloth-aluminum alloy multi-layer Preparation method of layer structure composite materials. In the ingot with this structure, the internal tin interlayer melts first during the hot rolling process, so that the carbon fiber cloth is sandwiched in a layer of liquid tin melt, so the stress will be evenly distributed on the carbon fiber cloth and greatly reduced, which is very good Protect the carbon fiber cloth from breaking and failing during deformation. The innovation of this structure is that on the basis of the corrugated carbon fiber cloth reinforced aluminum matrix composite material designed by other researchers to achieve the coordinated extension of the metal matrix and reinforcement, a layer of low melting point metal tin is added around the carbon fiber cloth, and the hot rolling process The metal tin in the medium melts into a liquid state. The liquid tin layer around the carbon fiber cloth avoids the extrusion and cutting effect caused by the direct contact between the carbon fiber cloth and the solid aluminum, which can effectively prevent the carbon fiber cloth from being damaged due to excessive load or stress concentration. . At the same time, the carbon fiber cloth soaked in liquid tin has the conditions for free distribution in the liquid, which is more conducive to achieving coordinated extension with the aluminum matrix during the rolling process, fundamentally protecting the integrity of the carbon fiber cloth. Liquid metal tin with a volume ratio of 0.02% is squeezed into the carbon fiber bundle during the rolling process, protecting the integrity of the carbon fiber cloth. The tin that is not squeezed into the carbon fiber bundle is solid-solved with the aluminum alloy through heat treatment, ensuring the composite material mechanical properties.

(2) Technical solutions

The technical solution of this invention is as follows:

The design concept of a rolled carbon fiber reinforced aluminum alloy composite material. The idea is to fold the carbon fiber cloth into a corrugated shape and implant it into tin to prepare a tin-coated corrugated carbon fiber cloth sandwich, and then cast the aluminum alloy around it. The melt is used to construct a tin-coated corrugated carbon fiber cloth-aluminum alloy multi-layered structure composite material, in which the volume ratio of tin is Sn/(Al+Sn)=0.020. During the hot rolling process, the molten tin is squeezed into Inside the carbon fiber bundle, the direct contact between the carbon fiber cloth and the solid aluminum is avoided to cause stress concentration and fracture failure. On the other hand, during the heat treatment process after hot rolling, the excess liquid tin is solidly dissolved with the aluminum alloy, ensuring the mechanical properties of the composite material.

As mentioned above, the design concept of a rolled carbon fiber reinforced aluminum alloy composite material is to fold the carbon fiber cloth into a corrugated shape and implant it into the tin. The tin melt should be tightly distributed around the carbon fiber cloth. The thickness of the tin interlayer can be determined by two layers. The width of the inner wall of each graphite insert plate is controlled.

A device for preparing rolled carbon fiber reinforced aluminum alloy composite materials includes five parts: a graphite crucible, a U-shaped stainless steel fixture, a graphite insert plate, a fixing device, and a stainless steel mold.

As described above, in the device for preparing rolled carbon fiber reinforced aluminum alloy composite materials, preferably, there is a corrugated channel slightly wider than the thickness of the carbon fiber cloth on each side of the U-shaped stainless steel clamp for implanting the carbon fiber cloth. The inner walls of the two graphite insert plates should be corrugated for pouring into a tin-coated corrugated carbon fiber cloth sandwich (hereinafter referred to as the corrugated tin sandwich).

As described above, in the device for preparing rolled carbon fiber reinforced aluminum alloy composite materials, preferably, the corrugated tin sandwich should be fixed at the center of the stainless steel mold to ensure that equal amounts of aluminum alloy melt are poured on both sides.

A method for preparing rolled carbon fiber reinforced aluminum alloy composite materials, which includes the following steps:

S1. Melt the tin and aluminum alloy in a resistance furnace respectively, and then keep them warm for a period of time after they completely become liquid to make their internal temperature field and composition uniform. Note that the interface fluctuations should be prevented during the insulation process of aluminum alloy to avoid damage to the surface oxide layer and oxidation of the internal aluminum or other alloys.

S2. Preheat the carbon fiber cloth in a muffle furnace with a preheating temperature of 400°C and a preheating time of 0.5h. Implant the preheated carbon fiber cloth into the corrugated channel of the U-shaped stainless steel fixture, and then place the U-shaped stainless steel fixture in the graphite crucible. Place two graphite insert plates vertically on both sides of the stainless steel insert plate. Place the graphite crucible and stainless steel mold equipped with U-shaped stainless steel fixtures and graphite inserts in a resistance furnace to preheat at a preheating temperature of 300°C and a preheating time of 2 hours. After preheating is completed, a tin melt with a volume ratio of Sn/(Al+Sn) = 0.020 is poured into the gap of the plug-in board. After it is completely solidified, it is taken out to obtain a corrugated tin sandwich.

S3. Fix the corrugated tin sandwich in the stainless steel mold, pour the heat-insulated aluminum alloy melt into the stainless steel mold, and take it out after the melt is completely solidified.

S4. The obtained ingot can be rolled in multiple passes on the hot rolling mill. Before rolling, the sample needs to be kept at the corresponding rolling temperature for 1 hour. The hot rolling experiment was conducted in four passes, divided into two parts: rough rolling and fine rolling. The first rough rolling reduction rate is controlled at about 35%, and the rolling temperature is 350°C; the subsequent three finishing rolling reductions are 5% each time, and the rolling temperature is 300°C, ensuring the total reduction rate after rolling. 50%. The rolling rate during the sample rolling process is controlled at around 0.5s ^-1 .

S5. The rolled samples are first placed in a heat treatment furnace for solution treatment. The solution temperature is 350°C and the solution time is 36 hours. The samples were then taken out and quenched in water at 30°C. Finally, artificial aging treatment is carried out, the aging temperature is 150°C, and the aging time is 8 hours. After heat treatment, the finished product of tin-coated corrugated carbon fiber cloth-aluminum alloy multi-layer structure is obtained.

In a preferred embodiment, the melting temperature of the aluminum alloy in step S1 is 700°C, the holding temperature is 680°C, and the holding time is 25 minutes; the melting temperature of the tin is 330°C, and the casting temperature is 300°C.

In a preferred experimental plan, in step S2, the carbon fiber cloth is preheated in a muffle furnace to remove glue, the preheating temperature is 400°C, and the preheating time is 0.5h. The graphite crucible and stainless steel mold equipped with U-shaped stainless steel fixtures and graphite inserts are placed in a resistance furnace to preheat. The preheating temperature is 300°C and the preheating time is 2 hours. The size of the inner wall of the graphite crucible is 52×42×100mm, the size of the stainless steel insert plate is 40×30×100mm, the length of the graphite insert plate is 40mm, and the height is 100mm.

In a preferred experimental plan, in step S3, the corrugated tin sandwich is fixed in the middle of the stainless steel mold using a fixing device. The size of the stainless steel mold is 60×60×100mm.

(3) Beneficial effects

The beneficial effects of the present invention are:

The tin-coated corrugated carbon fiber cloth-aluminum alloy multi-layer structure constructed by the present invention enables the corrugated carbon fiber cloth structure to overcome the ductility mismatch between the aluminum alloy matrix and the carbon fiber cloth during the rolling deformation process of the composite material. . If the tin layer is not added, stress concentration will easily occur on the carbon fiber cloth, causing premature breakage and failure of the carbon fiber cloth. The tin layer around the corrugated carbon fiber cloth melts into a liquid state during the hot rolling process, which avoids the stress concentration caused by direct contact between the carbon fiber cloth and the solid aluminum alloy, thus preventing the carbon fiber cloth from breaking during the rolling process. This design method can greatly improve the thermoplasticity and mechanical properties of composite materials, and can provide new structural design ideas for new lightweight and high-strength aluminum-based composite materials required in my country's aerospace field.

Just adding a thin layer of tin can greatly improve the thermoplasticity and tensile properties of the composite material without increasing its weight, giving it good specific modulus and specific strength. In addition, aluminum alloys have the advantages of low density, good thermal conductivity, large load-bearing capacity, and high fatigue strength, which can also improve the damage resistance and fatigue resistance of composite materials.

Description of the drawings

Figure 1 is a schematic diagram of the design concept of a rolled carbon fiber reinforced aluminum alloy composite material;

Figure 2 shows three views of the graphite insert plate;

Figure 3 shows three views of the U-shaped stainless steel clamp;

Figure 4 is a diagram of the preparation process of the corrugated tin interlayer;

Figure 5 is a diagram showing the preparation process of tin-coated corrugated carbon fiber cloth-aluminum alloy multi-layer structure ingot.

The components in the drawings are marked as follows:

1: Graphite plug-in board;

2: U-shaped stainless steel clamp;

3: Corrugated groove;

4: Tin sandwich;

5: Carbon fiber cloth;

6: Graphite crucible;

7: Aluminum alloy melt;

8: Stainless steel mold.

Detailed ways

The present invention will be introduced in detail below with reference to the accompanying drawings and through specific implementation examples, so that the advantages and features of the present invention can be more easily understood by those skilled in the art.

Example

The preparation method of a tin-coated corrugated carbon fiber cloth-aluminum alloy multi-layered structure composite material is as follows:

First, the carbon fiber cloth is folded into a corrugated shape and implanted into metal tin to form a corrugated tin interlayer. The volume ratio of tin is Sn/(Al+Sn) = 0.020. Then the aluminum alloy is poured around the corrugated tin interlayer. After cooling to room temperature, the resulting composite material ingot is rolled on a hot rolling mill. During the hot rolling process, the internal low melting point metal tin first melts into a liquid state. On the one hand, the liquid tin serves as an intermediate layer to block direct contact between the carbon fiber cloth and the solid aluminum. On the other hand, the fluidity of the liquid tin can provide free distribution of the carbon fiber. Under the conditions, during the rolling deformation process, the carbon fiber cloth is driven to straighten by liquid tin extrusion, which promotes the synergistic extension of the carbon fiber cloth coupled with the aluminum matrix, so that during the plastic deformation process, the carbon fiber cloth can not only couple the aluminum alloy to synergistic extension, but also prevent the carbon fiber cloth from Premature fracture failure due to stress concentration. Finally, aluminum and tin are diffused and interlocked through heat treatment, eliminating excess soft tin, further improving the mechanical properties of the composite material, and obtaining the final product tin-coated corrugated carbon fiber cloth-aluminum alloy multi-layer structure composite material.

A device for preparing tin-coated corrugated carbon fiber cloth-aluminum alloy multi-layer structure composite materials is shown in Figures 2, 3, 4 and 5. Specifically, it consists of five parts: graphite insert plate (1), U-shaped stainless steel clamp (2), carbon fiber cloth (5), graphite crucible (6), and stainless steel mold (8). There is a corrugated groove (3) on each side of the U-shaped stainless steel clamp. The two grooves are parallel and used to fix the carbon fiber cloth. The shape parameters of the corrugated groove are as shown in Figure 3, A=8mm, B=15mm, D=2mm, and the position parameter P=18mm. The outer side of the two graphite insert plates is a flat surface and the inner side is a corrugated surface. The parameters of the corrugated surface match the corrugated parameters of the U-shaped stainless steel fixture. The distance M between the two graphite insert plates is 10 mm. The two graphite insert plates are placed perpendicularly to the two sides of the U-shaped stainless steel fixture and serve as molds in the process of casting the corrugated tin sandwich. The thickness of the carbon fiber cloth is 0.8mm. There are 5 bundles of fibers in every 10mm in the warp and weft directions, and each bundle contains about 3,000 fibers. The graphite crucible is used to place the U-shaped stainless steel fixture and graphite insert plate embedded in the corrugated carbon fiber cloth. The two sides of the U-shaped stainless steel fixture are close to the left and right sides of the graphite crucible, and the outer sides of the two graphite insert plates are close to the graphite crucible. Front and back sides. Pour the tin melt (4) smelted in the resistance furnace into the graphite crucible to complete the composite process with the carbon fiber cloth to produce a corrugated tin interlayer. The stainless steel mold is used to place the corrugated tin interlayer and contain the aluminum alloy melt (7) melted by the resistance furnace to complete the composite process of the two.

The preparation process of a tin-coated corrugated carbon fiber cloth-aluminum alloy multi-layered structure composite material is shown in Figures 4 and 5.

S1. Melting of metallic tin: In the experiment, metallic tin was selected as the material for wrapping the carbon fiber cloth, and a resistance furnace was used to smelt the metallic tin. The melting temperature was set to 330°C. After it is completely melted into a liquid state, it is kept warm at 300°C for later use. During the smelting and heat preservation processes, liquid level fluctuations should be minimized to prevent the tin from being severely oxidized.

S2. Composite of carbon fiber cloth and metal tin: Before the composite process, first place the carbon fiber cloth in a muffle furnace to preheat and remove glue. The preheating temperature is 400°C and the preheating time is 0.5h. The preheated carbon fiber cloth is implanted into the corrugated grooves on the side of the U-shaped stainless steel fixture to fix its corrugated shape. The corrugated structure size factor A value is 8mm, B value is 15mm, D value is 2mm, and the position parameter P value is 18mm. Then place the U-shaped stainless steel fixture inserted with corrugated carbon fiber cloth in the graphite crucible, and then insert the two graphite insert plates vertically into the graphite crucible on both sides of the U-shaped stainless steel fixture. The gap width between the two graphite insert plates The M value is 10mm. Finally, the graphite crucible and stainless steel mold equipped with U-shaped stainless steel fixtures and graphite insert plates were placed in a resistance furnace for preheating. The preheating temperature was 300°C and the preheating time was 2 hours. Pour the metal tin melt in S1 into the graphite crucible, the pouring temperature is 300°C, and the volume ratio of metal tin is Sn/(Al+Sn)=0.020. After it is completely solidified and cooled to normal temperature, take it out as a tin sandwich.

S3. Melting of aluminum alloy: The melting temperature of aluminum alloy is 700℃, the holding temperature is 680℃, and the holding time is 25min. During the melting and heat preservation process, it is necessary to prevent liquid level fluctuations from destroying the oxide film on the surface of the aluminum alloy melt and causing the internal aluminum alloy melt to be oxidized.

S4. Composite of aluminum alloy and corrugated tin interlayer: Fix the corrugated tin interlayer prepared in S2 in a stainless steel mold, and then pour the insulated aluminum alloy melt in S3 into the stainless steel mold at a pouring temperature of 680°C. . Take it out after it has completely solidified and returned to normal temperature.

S5. Finished product hot rolling process: The composite ingot obtained in S4 must undergo a hot rolling process to detect its thermoplasticity. Cut the ingot into samples of 100×40×40mm size, place the samples in a resistance furnace adjusted to the rolling temperature and keep them warm for 1 hour, and then roll them on a hot rolling mill. Four passes of rolling are carried out, and the rolling parameters are as follows: the deformation rate of the first rough rolling is controlled at 35%, and the rolling temperature is 350°C; the deformation rate of each of the last three finishing rollings is controlled at 5% to ensure that the ingot is cast. The total deformation is 50%, and the rolling temperature of finishing rolling is set to 300°C. The rolling rate is controlled at 0.5s ^-1 during the entire thermoplastic deformation process. After each rolling pass, the surface of the sample was treated with a wire brush, and the oxide layer and grease on the surface of the sample were cleaned with acetone. During the experiment, graphite powder and engine oil were used as lubricant between the sample and the pressure head.

After the hot rolling process, the samples were subjected to multi-stage heat treatment. First, place the sample in the heat treatment furnace, close the furnace door, and perform solution treatment. The solution treatment parameters are set to: temperature 350°C, holding time 36 hours. After the heat preservation is completed, the sample is taken out and quenched in water at 30°C. After quenching, place the sample in the heat treatment furnace, close the furnace door, and perform artificial aging treatment. The aging treatment parameters are set to: temperature 150°C, holding time 8 hours. After taking out the sample, the tin and aluminum in the sample have been completely dissolved. The mechanical properties of the obtained tin-coated corrugated carbon fiber cloth-aluminum alloy multi-layered composite composite material have been further improved.

It was measured through tensile experiments that the finished composite material with a tin-coated corrugated carbon fiber cloth-aluminum alloy multi-layered structure has a post-break elongation of 24.2% and a tensile strength of 226MPa.

Comparative example

In order to explore the improvement effect of the addition of liquid tin interlayer on the properties of composite materials, the same process conditions as in the example were used to directly implant the corrugated carbon fiber cloth into the aluminum alloy. It was measured through tensile experiments that the post-break elongation of the carbon fiber cloth-reinforced aluminum matrix composite material without tin interlayer was 19.2%, and the tensile strength was 163MPa.

Comparing the comparative example and the example, it can be seen that the post-fracture elongation and tensile strength of the composite material with the tin interlayer are significantly increased, and the weight is increased by 3.39% compared with the composite material without the tin interlayer. This shows that the addition of the tin interlayer can protect the carbon fiber cloth during the plastic deformation process of the composite material, greatly improving the thermoplastic and mechanical properties of the composite material, while avoiding the improvement of the overall mechanical properties to the greatest extent. The specific mechanical parameters of the examples and comparative examples are shown in Table 4.

The above descriptions are only embodiments with better effects of the present invention, and are not intended to limit the patent scope of the present invention. Any simple deformation or equivalent transformation made by skilled persons on the basis of the contents of the present invention, or directly or indirectly applied in other related technical fields, shall be included in the patent protection scope of the present invention.

Table 1 Composition (%) of aluminum alloy chemistry used

Table 2 Process parameters for the production of corrugated tin sandwich prefabricated parts

Table 3 Preparation and processing parameters of finished products

Table 4 Heat treatment process parameters

Table 5 Mechanical parameters of examples and comparative examples

Claims (3)

1. A method for preparing rolled carbon fiber reinforced aluminum alloy composite materials, which includes the following steps: S1. Melt the tin in a resistance furnace, turn it into a liquid state and then keep it warm; the preheating and degluing process of the carbon fiber is carried out in the muffle furnace, and the deglued carbon fiber is inserted into the corrugated channel of the U-shaped stainless steel fixture. And place the U-shaped stainless steel fixture in the graphite crucible; place two graphite insert plates perpendicular to both sides of the U-shaped stainless steel fixture in the graphite crucible; S2. Place the stainless steel mold and the graphite crucible equipped with U-shaped stainless steel fixtures and graphite inserts in a resistance furnace for preheating. After preheating, pour the insulated tin melt into the gap between the graphite inserts and wait until it is completely solidified. Then take it out to make a tin-coated carbon fiber corrugated interlayer; smelt the aluminum alloy matrix in a resistance furnace until it completely becomes a liquid and then keep it warm; S3. Take out the preheated stainless steel mold from the resistance furnace, and fix the tin-coated carbon fiber corrugated interlayer in S2 in the middle of the mold; pour the insulated aluminum alloy melt into the stainless steel mold, and take it out after it is completely solidified. , the composition of the obtained ingot is Sn/(Al+Sn)=0.020, and then hot rolling can be performed. 2. The preparation method according to claim 1, characterized in that the preparation device includes five parts: a graphite crucible, a U-shaped stainless steel fixture, a graphite insert plate, a fixing device, and a stainless steel mold; the size of the inner wall of the graphite crucible is 52×42×100mm. , the size of the U-shaped stainless steel fixture is 40×30×100mm, the length of the graphite insert plate is 40mm, the height is 100mm, and the size of the stainless steel mold is 60×60×100mm. 3. The preparation method according to claim 1, characterized in that the melting temperature of metallic tin is 330°C, the pouring temperature is 300°C, the ingot rolling temperature is 350°C, and the total rolling deformation is 50%.