In recent years, with the rapid development of the automotive industry, aerospace, and electronic communication technology, the materials that are the basis of these industries are required to have basic strengths such as high strength, high modulus, and high temperature resistance. Grinding, corrosion resistance, photoelectricity and other properties put forward more requirements.
For a single material, it is often unable to meet the requirements of many performances, and it is necessary to combine materials with different properties to prepare a composite material, so as to make up for each other. The composite material is a material with special properties selected from two or more components or components with a certain amount ratio through artificial compounding to form a multiphase, three-dimensional combination with a clear interface between each phase . The biggest advantage of composite materials is that the properties of the materials are designable, and the design freedom of the materials is high, so the development is rapid.
In addition to the characteristics of high specific strength, high specific modulus and low coefficient of thermal expansion, metal matrix composites (Metal Matrix Composites, MMCs for short) also have higher temperature resistance, flame resistance, high lateral strength and rigidity, no moisture absorption, The advantages of high thermal conductivity and electrical conductivity, good radiation resistance, and no gas emission during use show the incomparable characteristics of resin-based composite materials, so it has been highly valued by researchers at home and abroad, especially favored by the aerospace department .
Carbon fiber reinforced metal matrix composites have high specific strength and specific modulus, and are ideal structural materials in high-tech fields such as aerospace and other high-tech fields that have strict requirements on component quality. In recent years, with the emergence of high-performance carbon fibers and the cost reduction due to the expansion of production, the preparation and application of carbon fiber-reinforced aluminum-based composite materials have received extensive attention.
Carbon fiber reinforced aluminum matrix composite
01 carbon fiber
Carbon fiber is a fibrous carbon material with a carbon content of more than 90%. Carbon fiber has high specific strength, high specific modulus, high temperature resistance, corrosion resistance, fatigue resistance, creep resistance, electrical conductivity, heat transfer and small thermal expansion coefficient. Excellent performance of the series. Commonly used carbon fiber can be divided into viscose fiber, PAN-based (polyacrylonitrile) fiber and pitch fiber according to the source of raw silk. Viscose fiber has low strength and low Young’s modulus, but due to its low cost, it is still used in the manufacture of certain composite materials. PAN-based carbon fiber has better performance but higher price, and is mainly used in the aerospace field with high performance requirements. Compared with PAN-based carbon fiber, pitch-based carbon fiber has a certain price advantage, and shows a good application prospect in the fields of automobiles, machinery and electronics.
02 Carbon fiber reinforced aluminum matrix composite material
In the field of metal matrix composites in recent years, the development of aluminum matrix composites has been particularly rapid. This is not only because it has a series of advantages, but also because of the rich resources in the world, coupled with the use of conventional equipment and technology processing and processing, so the preparation and production of aluminum-based composite materials is more economical and easier than other metal-based composite materials Promotion and application.
At present, Al-Mg-Si series and Al-Cu-Mg series heat treatable alloys are mainly used as the base aluminum alloy for preparing Cf/Al composite materials. The latest application of anti-rust aluminum LF6 is an Al-Mg alloy with high magnesium content. It has good weldability and corrosion resistance, low to medium strength, and cold deformation can increase the strength. It is suitable for the manufacture of mid-loaded components, liquid containers, pipelines and other parts .
Preparation process of Cf/Al composite material
The manufacturing methods of carbon fiber reinforced aluminum matrix composite materials are:
01 Melt infiltration method
The fiber bundle is infiltrated with liquid aluminum and aluminum alloy, so that each fiber is wetted by molten metal to remove excess metal to obtain a composite wire, and then extruded to obtain a composite material. The disadvantage is that molten aluminum and aluminum alloys may damage fiber properties.
02 Squeeze casting method
The molten aluminum and aluminum alloy are forcibly pressed into the fixed cavity of the built-in fiber preform, and the pressure is applied until the end of solidification, so that the liquid metal to solidification are under high pressure. The squeeze casting method improves the wettability of the metal melt due to high pressure, and the reaction between the reinforced fiber of the obtained composite material and aluminum and aluminum alloy is minimal, and there are no conventional casting defects such as voids and shrinkage holes.
03 Diffusion bonding method
Aluminum foil is laminated with carbon fiber wire or composite wire or single-layer board soaked with aluminum liquid after surface treatment in a prescribed order, and is formed by high-temperature pressure diffusion bonding under vacuum or inert gas conditions to obtain an aluminum-based composite material. .
04 powder metallurgy
Plasma spray method is used to spray metal aluminum powder on the arranged reinforcing fibers, or to disperse the metal aluminum powder in acrylic resin for coating to make a prefabricated plate, which are alternately overlapped in a vacuum or argon gas, near the aluminum Pressure sintering at melting temperature to obtain fiber reinforced aluminum matrix composites.
05 Vacuum pressure infiltration method
When the vacuum pressure impregnation method is used, the reinforced preform placed in the mold is first evacuated, and then pressure is applied to press the molten metal liquid into the mold for compounding, and the part is obtained after cooling.
Although this method has the disadvantages of expensive equipment and limited workpiece size, for small parts, it has many advantages, because in addition to the advantages of a large range of reinforcements and good product quality, it can also be achieved almost Volume molding, especially suitable for complex and precise parts.
Process parameters of vacuum pressure infiltration
The vacuum pressure infiltration process parameters of Cf/Al composite materials mainly include the following:
01 Infiltration temperature
The infiltration temperature is an important process parameter in the vacuum pressure infiltration process. Throughout the preparation process, the choice of temperature determines the fiber interface reaction after the material is formed. If the infiltration temperature is too high, it is easy to cause the high-temperature interface reaction between the fiber and the matrix, generating a large amount of interface reactant Al4C3 brittle phase, the interface between the matrix and the reinforcement is too strong; the infiltration temperature is too low, although the interface reaction is slowed, but The aluminum melt will quickly cool below the freezing point of aluminum during the infiltration process, resulting in the failure of material compounding.
02 Infiltration pressure
The infiltration pressure is another important process parameter in the vacuum pressure infiltration process. The infiltration pressure determines the process of the metal-impregnated fiber preform and affects the density of the final composite material.
03 Vacuum
The degree of vacuum in the material preparation process determines the degree of oxidative damage of the reinforcement fibers in the final composite material, which is of great significance to the final performance of the composite material.
Development level of aluminum matrix composites at home and abroad
01 Development level of foreign aluminum matrix composites
The research of aluminum-based composite materials began in the 1950s, and has made great progress both in theory and technology in the past 20 years. All countries have invested a lot of manpower and material resources in research and development. It is the most studied and the main composite material in metal matrix composites. Currently developed aluminum-based composite materials mainly include SiC/Al, B/Al, BC/A1, Al2O3/Al, etc. Among them, B/Al composite materials are developing rapidly. At present, the United States can manufacture various B/Al profiles of more than 2m, Pipes, etc. These materials are used in aircraft and can reduce the quality by 20%. Aluminum-based composite materials have been widely used in the manufacture of wings, rudders, flaps, fuselages, skins and other components of large aircraft such as annihilators and helicopters. US McDonnell Douglas used 1.8-2.25t fiber-reinforced aluminum-based composite materials (FRM) on the F-15 fighter, which reduced the quality of the fighter by 2%. The former Soviet Union Institute of Aeronautical Materials used boron fiber-reinforced aluminum-based composite materials for the An-28 and An-72 aircraft body structures. While improving reliability, the quality of parts was reduced by 25% to 40%. But for a long time, due to the complex preparation process, strict requirements on environment and equipment, and high cost of aluminum-based composite materials, its application has not been widespread.
There are three major companies that use powder metallurgy to produce particle-reinforced aluminum-based composite materials: DWA Aluminum Composite in the United States, Alyn, and Aerospace Metal Composites (AMC) in the United Kingdom. These companies already have large-scale production capacity and rich product specifications. The main products of DWA Aluminum Matrix Composites are composite materials with 6092, 2009 and 6063 as the matrix and SiC particles as the reinforcement. 6092/SiC is its early product series, mainly including plates and extruded profiles.
An example of aerospace applications is that in the 1980s, Lockheed Martin used 25% SiCP/6061A1 composite materials to make stents for holding instruments. Its rigidity is 65% higher than that of 7075 aluminum alloy. In the late 1990s, silicon carbide particles reinforced aluminum-based composite materials were widely used in large passenger aircraft. Pratt & Whitney started from the PW4084 engine, using extruded silicon carbide particles reinforced and deformed aluminum alloy matrix composite material (6092/SIC/17.5p-T6) produced by DWA company to make the fan outlet guide vane for the PW4000 series engine. On the Boeing 777 airliner.
Particle-reinforced aluminum-based composites have higher impact resistance than resin-based composites, and their erosion resistance is 7 times that of resin-based composites. It is easy to find various damages and reduce costs by more than 1/3.
For the first time, Toyota Japan used A12O3/A1 composite materials to prepare the piston of the engine. The weight was reduced by 5%-10%, and the thermal conductivity was increased by about 4 times. The connecting rod is the second component in the automotive engine that successfully uses metal matrix composites. The Al2O3/A1 alloy composite connecting rod made by Japan Mazda Company is 35% lighter than the steel connecting rod, with high tensile strength and fatigue strength of 560MPa and 392MPa, respectively; and the linear expansion coefficient is small.
China’s aluminum-based composite material technology development level
China has carried out more comprehensive research on aluminum-based composite materials, including fiber-reinforced, particle-reinforced, laminated composite, spray deposition, and in-situ generation, and has made progress and is moving towards practical use. The use of pressure-casting high-content SiCp/A1 composite materials to make pedestals to replace W-Cu pedestals and encapsulate microwave power devices is expected to replace W-Cu, Mo-Cu and other materials in the packaging field.
On the basis of strengthening mechanism and preparation and processing research, the development level of aluminum matrix composites has gradually matured. Through years of research and accumulation, it has made important breakthroughs in the plastic toughness and forming ability of aluminum-based composite materials after the 1990s. Although it lags behind advanced foreign countries, several typical aluminum-based composite materials (such as SiC/A1, A12O3 /A1) is gradually gaining recognition in the fields of aerospace, transportation and electronic instruments. In the future, with the steady improvement of research level and the development of new composite materials, aluminum-based composite materials will be expected to be applied in many fields.
In recent years, a new material with high strength, super wear resistance and good corrosion resistance, which can be widely used in aerospace manufacturing and automotive machinery industry-particle reinforced SiCp aluminum matrix composite material, was successfully developed in ZLSD. The density of this new aluminum-based composite material is only 1/3 of that of steel, but its specific strength is higher than that of pure aluminum and medium carbon steel. It has extremely strong wear resistance and can work stably at a high temperature of 300-350℃ Therefore, it is widely used in the manufacture of automobile engine pistons, gear boxes, aircraft landing gear, high-speed trains and precision instruments, etc., and forms a market-oriented production scale.
Throughout the world, the application research of aluminum matrix composites mainly focuses on SiC particle reinforced aluminum matrix composites, and has made great achievements. A few countries (such as the United States, Japan, and Canada) have entered the application stage and achieved significant economic benefits. Aluminum matrix composite materials have been widely used in many fields such as automobile industry, aerospace, electronics, military industry and sports since its advent. The key factors restricting its development (such as complex technology and high cost) are gradually being eliminated. Many countries have established industrial-scale factories for producing aluminum-based composite materials. It is believed that in the near future, the manufacturing process of aluminum-based composite materials will Simpler, the cost will be lower, and the scope of use will be wider.
03 Analysis of the application fields of aluminum matrix composites
Particle-reinforced aluminum matrix composite materials and fiber-reinforced aluminum matrix composite materials have entered the stage of commercial application.
3.1 Application in transportation
Transportation is always one of the important civil fields of aluminum-based composite materials. Considering the related factors such as cost and industrial application, continuous fiber-reinforced aluminum matrix composites and high-cost discontinuously reinforced aluminum matrix composites are excluded from this field. Cheap particles and short fiber reinforced aluminum matrix composites The material has the possibility of large-scale application.
Aluminum-based composite materials started earlier in the automotive industry. In the 1980s, Toyota Japan had used aluminum silicate fiber reinforced aluminum matrix composite materials to successfully manufacture automobile engine piston anti-wear rings and automobile connecting rods and other automobile parts. The Duralean company in the United States has developed a SiC particle reinforced aluminum matrix composite material to make automobile brake discs, which has reduced the quality of 40%-60%, and improved the wear resistance, noise has been significantly reduced, friction and heat dissipation; at the same time The company also uses SiC particle reinforced aluminum matrix composite materials to manufacture automobile engine pistons and gear boxes and other automobile parts. This kind of automobile piston has higher wear resistance, good high temperature resistance and seizure resistance than aluminum alloy pistons, and has a smaller thermal expansion coefficient and better thermal conductivity. Automotive gearboxes made of SiCp/Al composite materials are significantly improved in strength and wear resistance compared to aluminum alloy gearboxes. Aluminum alloy composite materials can also be used to manufacture brake rotors, brake pistons, brake pads and calipers and other brake system components, and can also be used to manufacture automobile drive shafts and rocker arms and other automobile parts. Units such as Shanghai Jiaotong University and the Academy of Ordnance Science have also conducted a lot of practical work on the application of aluminum-based composite materials in automobiles.
3.2 Application in the field of aerospace
The development of aluminum-based composite materials has made it possible to manufacture lightweight, flexible, and high-performance aircraft and satellites in the modern aerospace field. Cereast company developed a 20% Vo1+A357SIC composite material by investment casting process. Using this material instead of titanium alloy to manufacture aircraft camera mirror frame with a diameter of 180mm and a mass of 17.3kg, its cost and quality are significantly reduced, and its thermal conductivity is improved. . At the same time, the composite material can also be used to manufacture support frames for satellite reaction wheels and steering frames. American DWA Company replaced the 7075 with a 25% SiCp/6061 aluminum matrix composite material to manufacture guide grooves and angle bars for aerospace structures, which reduced its density by 17% and its modulus by 65%. Cast SiC particle reinforced A356 and A357 composite materials can be used to manufacture aircraft hydraulic pipes, helicopter landing gear and valve bodies.
Aluminum matrix composites are favored in aviation, aerospace and military sectors due to their own special advantages, and are widely used. For example, the Cr/A 1 composite material manufactured by DWC Special Composites is applied to NASA’s satellite waveguides. It has good conductivity and small thermal expansion coefficient, which is lighter than the original graphite/epoxy waveguides. About 30%. The Russian Aeronautical Materials Research Institute used B/Al composite materials for the fuselage structure of the An-28 aircraft, reducing the quality of parts by about 25%. In addition, A1-based composite materials are also used to manufacture optical and electronic parts. The University of Arizona has developed an ultra-light space telescope that uses SiC/A1 composite materials to manufacture racks, brackets, and secondary mirrors, which greatly reduce the quality. The American DWA company and the British AMC company used SiC/Al in batches for the EC-120 and EC-135 helicopter rotor systems, greatly improving the rigidity and life of the components. The successful application of these key structural parts shows that the application research of this material in the United States and the United Kingdom has been quite mature.
SiC particle-reinforced aluminum-based composite sheet will be used in the skin of advanced fighters and the reinforcement of the tail. NASA uses graphite/aluminum composite materials as the 20m cargo compartment frame of the shuttle.
3.3 Application in weaponry
In the past 10 years, the reduction of fiber prices and the emergence of composite processes such as squeeze casting, vacuum suction casting and vacuum pressure infiltration have made it possible for composite materials to be used in large quantities of conventional weapons. Fiber-reinforced aluminum-based composite materials have become more and more widely used in weapons because of their good comprehensive performance. Various advanced countries have invested a lot of research work to trial-produce connecting rods, pistons, tactical engine shells, and steering rudders in engines. Plate, warhead support frame, military battle bridge tension string, bridge tank bridge body and long rod armor-piercing projectile bolster, etc. As early as the late 1970s, the US Army conducted research on Al2O3/A206 composite materials for manufacturing track shoes. By using composite materials to manufacture track shoes, its quality can be reduced from 544-680kg of cast steel to 272-362kg. Nearly 50%. The U.S. Navy Ground Weapon Center uses SiC/A1 composite materials for ship structures and decks. It also intends to use this material for a variety of underwater engineering and torpedo and torpedo shells. The bridge with a span of 30m made of silicon carbide fiber reinforced aluminum alloy composite material has a mass of only 5t and a stiffness 30% higher than that of aluminum alloy. As the price and technical issues continue to be resolved, the application of such materials in the field of weapons will be more extensive.
3.4 Application in electronic and optical instruments
Aluminum-based composite materials, especially SiC-reinforced aluminum-based composite materials, have the advantages of low thermal expansion coefficient, low density and good thermal conductivity, and are suitable for manufacturing electronic devices such as lining materials for electronic equipment and heat sinks. The thermal expansion coefficient of the SiC particle-reinforced aluminum matrix composite material can completely match the thermal expansion of the electronic device material, and the electrical conductivity and thermal conductivity are also very good.
In the application research of precision instruments and optical instruments, aluminum-based composite materials are used to manufacture telescope brackets and secondary mirrors. In addition, aluminum-based composite materials can also manufacture precision parts and optical instruments such as precision parts of inertial navigation systems, rotating scanning mirrors, infrared observation mirrors, laser mirrors, laser gyros, reflectors, mirror bases, and optical instrument brackets.
Applied in the field of electronic packaging. Since the 1990s, some companies in developed countries have vigorously developed high-content SiCp/Al composite materials for electronic packaging. The development of metal matrix composites with high thermal conductivity and low thermal expansion for electronic device packaging is one of the development trends of new materials. The United States has successfully developed SiCp/Al, Sip/Al, C/Al and other high-performance electronic packaging composite materials, which become the key to solving the problem of rapid heat transfer and heat dissipation of electronic devices. The developed electronic packaging composite material is an aluminum-based composite material with a SiCp content of 60% to 75%.
3.5 Other applications
(1) Application of low-expansion aluminum-based composite materials in spaceborne high-power multiplexers.
(2) Application in the nuclear industry. B4C has the characteristic of absorbing neutrons, so B4C particles reinforced aluminum matrix composites have good application prospects in the storage of nuclear waste. DWA uses 41%B4Cp/Al composite materials to make dry storage barrels for nuclear waste, which has achieved large-scale application.
(3) Composite wire. Electri Plast materials have broad market prospects, and are expected to be used in wire and cable and de-icing systems in the aerospace field. Because the average mass of the material is 20% lighter than copper, the quality of cables that are several miles in length can be reduced by several tons.
(4) Nano-micron hybrid reinforced aluminum matrix composite material and its application.
The material can be widely used in the manufacture of civil and military motor vehicle engine pistons, cylinder blocks, cylinder heads, rocker arms, brake discs, tires, track shoes, light armor plates, and high-stability optoelectronic instruments and precision instrumentation parts. , Can also be applied to ships, aviation and electronic devices. At present, the military high-power supercharged diesel engine pistons produced with this material have passed the engine 800h bench test and 1.0×104km sports car test, and its comprehensive performance is better than that of the German Mahler company, and fully meets the requirements of imported piston materials.
(5) The application of graphite fiber reinforced aluminum matrix composite materials in the lens barrel structure of space remote sensors.
In the 1960s, the United States used B/Al composite pipe to make the main frame of the space shuttle orbiter, which was 45% lighter than the original designed aluminum alloy frame. The Hubble space telescope antenna suspension made of 42.2% P100 graphite fiber reinforced 6061 aluminum is a typical application of graphite fiber reinforced aluminum matrix composite materials in spacecraft.
The Canadian Space Agency uses ultra-light laser scanning mirrors made of silicon carbide-reinforced aluminum matrix composites and beryllium aluminum alloys to be used in the next-generation Space Vision System. A variety of other composite materials are also used in the satellite’s deployable antenna and the space camera’s mirror.
Beijing Space Electromechanical Research Institute used discontinuous silicon carbide reinforced aluminum matrix composite material (SiCp/Al) to make the mirror box and body of the space camera. Beijing Institute of Aeronautical Materials used a pressureless infiltration composite method to prepare high-volume SiC/Al composite materials used as space optomechanical structural parts. In addition, a variety of resin-based carbon fiber composite materials are also used to manufacture the hood, lens barrel and bottom plate of space cameras.
(6) Application of fiber-reinforced aluminum-based composite materials in power transmission wires.
Continuous alumina fiber reinforced aluminum matrix composite core power transmission wires are gradually paid attention by researchers due to their advantages of light weight, high strength, small creep and small linear expansion coefficient. Continuous alumina fiber-reinforced aluminum-based composite materials are used for the first time in transmission conductors as load-bearing parts of conductors.
The characteristics of aluminum-based composite materials make it widely used in the civil field. Toyota Japan successfully used the Al2O3/Al composite material to prepare the engine piston for the first time in 1983. Compared with the original cast iron engine piston, the mass was reduced by 5%-10%, and the thermal conductivity was increased by 4 times.
Aluminum-based composite materials are also widely used in the manufacture of bicycles, medical appliances, sports equipment and other high-performance components, such as electronic packaging composite materials, computer discs, and automobile brake discs, which have promoted these industries to become new economic growth points. . As a functional material, it is expected to be more widely used in industrial sectors such as machinery, metallurgy and building materials.
Application prospects of aluminum matrix composites
Carbon fiber reinforced aluminum matrix composites have high strength and high modulus, their density is less than that of aluminum alloys, but their modulus is 2 to 4 times higher than aluminum alloys. Therefore, the components made of composite materials have light weight, good rigidity, and the smallest available The wall thickness is made into a structurally stable member to improve the equipment capacity and loading capacity, and can be used in space shuttles, artificial satellites, high-performance aircraft and so on. Taking the mass of an airplane as an example, the mass of the fuselage of the airplane accounts for about 50% of the take-off mass, fuel accounts for 25%, and only 25% is reserved as a load. If lightweight and high-strength Cf/Al composites are used in aircraft manufacturing, as long as the mass is reduced by 10%, then the effective load will increase by 20%. As the most cost-effective way to reduce weight and increase efficiency of aircraft structural parts, the application of Cf/Al composite materials on aircraft structural parts is expanding.
The navigation system and aerospace antenna made of Cf/Al composite material can effectively improve its accuracy; the satellite parabolic antenna skeleton made of carbon fiber reinforced aluminum matrix composite material has a low thermal expansion coefficient and good thermal conductivity, which can be used at a large temperature Keeping its size stable within the range makes the satellite parabolic antenna gain efficiency increase by 4 times, while also significantly reducing the quality of the structure.
With the deepening of research and exploration, in addition to being the first to be used in aerospace, aviation and weapons, the application in the civil industry is also increasing day by day, and it is widely used in aircraft components, automotive engine parts, sliding parts, packaging materials for computer integrated circuits and Electronic equipment substrates, etc.
In recent years, the development of carbon fiber-reinforced aluminum-based composite materials has been particularly rapid. Because of the abundant aluminum resources and the appearance of high-performance carbon fibers and the reduction of carbon fiber costs worldwide, the preparation and processing of fiber-reinforced aluminum-based composite materials are better than other metal-based materials. Composite materials are more economical, easy to promote and apply, and are generally valued by people.
The cost of the Cf/Al composite material mainly comes from the cost of raw materials and preparation. In the spacecraft, for every kilogram of material used, the launch cost is reduced by 10,000 US dollars. Therefore, as long as the research cost is further reduced and the price/performance ratio is further increased, the high-strength Cf/Al composite material will have very broad prospects.