Summary and latest research progress of aerospace new high performance materials
Countries all over the world attach great importance to the development of new materials and launch a number of strategic policies to promote the development of new materials technology. The new material industry in developed countries has its own characteristics and focuses on different fields. The United States focuses on scientific and technological research and development and maintains a leading position in the world. Japan attaches great importance to the research and development of new materials, while improving the performance of existing materials and making the best use of limited resources. The eu's new materials technology strategy aims to maintain competitive advantages in aerospace materials and other fields.
In this paper, the research and application status of new materials in international space industry are described in detail, the research results of new materials in domestic space industry are mainly introduced, and the future development trend of new materials in space industry is pointed out.
High performance light metal alloy
In order to meet the development needs of missile, rocket and other space equipment platforms such as lightweight, high reliability and high pushing ratio, high performance lightweight metal alloys developed abroad are mainly composed of third-generation aluminum lithium alloy, high strength magnesium alloy, low cost titanium alloy and high temperature resistant alloy.
1.1 the third generation aluminum lithium alloy
In the 1920s, Germany developed the first generation of aluminum-lithium alloy. The disadvantages are obvious, such as low ductility, poor toughness, difficulty in processing and high price, etc., which do not attract enough attention . After 1970, Europe and the United States and other countries developed second-generation aluminum lithium alloy products, including the former Soviet union's 1420 aluminum lithium alloy and the United States' 2090 aluminum lithium alloy. Problems also exist in the second generation of al-lithium alloys, including low strength and low plasticity .
In 2013, the Air Ware series third-generation aluminum lithium alloy launched by Canada's Ken alliance company has been used in airbus A350, bombardier's c-series aircraft and military aircraft such as f-16 and f-18, as shown in FIG. 1 . The new material, called "superalloy" by the us aviation community, was named by us magazine as one of 13 major aviation events of 2013. When adding lithium element, the third generation aluminum lithium alloy pays more attention to the balance between alloy strength and fatigue crack propagation performance. By reducing the lithium content (to 1wt% ~ 2wt%) and optimizing the heat treatment system, good comprehensive performance was obtained. It can reduce the aircraft structure by 25%, increase the corrosion resistance by 46% compared with traditional aluminum and lithium alloy, increase the fatigue resistance by 25%, and reduce the aircraft resistance by 6%. In addition, compared with composite materials, the machinability is also improved. The traditional aluminum alloy manufacturing process can be used to reduce risks and costs. Future applications will be targeted at the A320 and Boeing 737's successor narrow-body aircraft and will also be used for the spacer, cover and other structural components of the military aircraft f-35, f-16 and f-18.
In the future, the development of aluminum-lithium alloy should be strengthened in the following aspects:
(1) increase the toughness, shape and strength of al-li alloy; (2) reduce the structural quality of aluminum-lithium alloy; (3) improve the anisotropy of aluminum-lithium alloy.
1.2 high strength magnesium alloys
In the 1940s, magnesium alloys developed rapidly . However, due to the high price, the study of magnesium alloys has stalled.
In recent years, due to the increasingly prominent environmental and energy problems, as well as the huge performance potential and advantages of magnesium alloys, the research and application of magnesium alloys have been paid more and more attention by developed countries and regions such as Germany, the United States, Canada and so on. Led by the German association for science and technology, the largest magnesium alloy and magnesium alloy die-casting project in Europe, "SFB390", which was organized and implemented by Germany's klosta university and Hanover university, exceeded 53 million euros. The main objective was to study the application of magnesium alloy in structural parts . The federal government of Canada, Quebec and norsk hydro have jointly invested 11.4 million Canadian dollars to establish a new research center for magnesium alloys. The purpose of this center is to obtain magnesium alloy die-casting parts with good performance by optimizing design technology and materials, so as to further expand the application field of magnesium alloys.
Magnesium alloys form stable high temperature phase with rare earth elements through alloying to improve the high temperature performance of magnesium alloys.
The strength and toughness of the alloy can be improved by the use of aging strengthening and deformation strengthening. The research results of American scientists show that the strength and fracture toughness of ZK60 magnesium alloy after extrusion and heat treatment are greatly improved . At present, the yield strength of deformation magnesium alloys in foreign countries reaches up to 300 MPa at room temperature and the elongation rate reaches 5%.
The lightness of magnesium alloy is the most important factor for its application in aerospace industry.
1.3 low cost titanium alloy
FIG. 2 shows the change of the amount of titanium in aircraft structures over time . Because of its high price, it is often used in key parts with high bearing capacity. In order to expand the use of titanium alloy, a new low cost titanium alloy has been actively developed abroad. American Allegheny technology company has also developed a new formula ti-4al-2.5 v-1.5 fe-0.25 O titanium alloy by replacing vanadium element and oxygen enrichment technology with iron element. Its performance is similar to that of ti-6al-4v alloy.
Although titanium alloy has great advantages as engine material, it also faces great challenges  :
(1) the performance of titanium alloy is not up to the standard under high temperature conditions; (2) the price of titanium alloy is too high.
1.4 high temperature resistant alloys
High temperature alloy refers to the specific metal materials that can work for a long time under the action of high temperature and stress with iron, nickel and cobalt as matrix materials . High temperature alloy at above 600 ℃ has good strength, plasticity, toughness and fatigue resistance, etc. After decades of development, high temperature alloys have been relatively mature and have been widely used in power equipment of weapons equipment. With the upgrading of materials, engine turbine inlet temperature is 777 ~ 1 027 ℃ from the first generation jumped to the fourth generation of 1 577 ~ 1 715 ℃.
Compared with pure metal and alloy materials, intermetallic compounds have excellent resistance to high temperature and wear resistance. Therefore, in recent years, a lot of work has been carried out in foreign countries on the basic research, composition design, development and application of intermetallic compounds, which are used to replace traditional nickel-based high temperature alloys and nickel-based monocrystalline alloys. Of Ti - Al alloy is the most rapid development, rich niobium hong 璗 iAl alloy has developed into the third generation, plasticity and toughness are greatly improved, has got a lot of application in aeroengine blades, casting the contrast 璗 iAl low-pressure turbine blades in gathered, Leap - 1 b, the dosage of the Leap - 1 c is expected to reach 1.2 million pieces, PCC company in 2014 to the Ti - Al blade annual output has reached 40000 pieces of .
2 composite material
The composite material has the characteristics of high strength, convenient processing and forming, strong anti-corrosion ability and so on. It can replace the traditional steel, aluminum alloy and other materials to make the structural parts of weapon equipment, which can greatly reduce the quality of equipment while ensuring the performance of weapon equipment. At present, the aerospace high-performance composite materials developed abroad mainly include resin-based composite materials, aluminum matrix composite materials and ceramic matrix composite materials.
2.1 resin matrix composites
Resin-based composites are made of polymer based composites and fiber reinforced composites . Therefore, the amount of resin-based composite material has become an important mark to measure the development of aerospace technology. Figure 3 shows the specific strength and specific modulus of resin matrix composites and light metal materials.
American tomahawk cruise missiles large used composite materials, such as the nose cone used the Kevlar/polyimide, radar antenna mask, inlet used the glass fiber/epoxy resin, inlet fairing adopted carbon fiber/polyimide, tail using the glass fiber/epoxy resin, epoxy resin/Kevlar, tail cone using the epoxy resin/glass roving, etc. The "pygmy" small surface-to-surface icbm three-stage engine combustion chamber housing is made of carbon fiber/epoxy resin. Trident (d-5) first and second stage solid engine housing is made of carbon/epoxy, its performance is 30% higher than Kevlar/epoxy .
Thermoplastic resin is used as the matrix of composite materials, which is superior to thermosetting resin in terms of fracture toughness, impact strength and moisture absorption. It is superior to epoxy resin system in terms of high temperature resistance, moisture resistance, impact resistance, thermal stability and damage tolerance, and has become the development trend of composite resin matrix. In recent years, fiber reinforced thermoplastic composites have made remarkable progress in production, greatly reducing the cost of materials and improving their usability. The U.S. army has proposed the development of fiber-reinforced thermoplastic composite missile cylindrical seam welding technology, materials and analysis technology for the fusion of missile engines and missile body cylindrical joints. San Diego composite material co., LTD. Has designed a welding machine, which can be used to process thermoplastic composite cylinder and apply to missile structural parts.
2.2 aluminum matrix composites
The strength of sic/al matrix composites is also much higher than that of al when the content of sic fibers is low. Because the cost is much lower than beryllium, it can also replace beryllium as an inertial device, and has been used in an American missile inertial guidance system and inertial measurement unit.
The Hubble space telescope high-gain antenna tower structure using P100 ultra high modulus carbon fiber (40 vol %) toughening of 6061 aluminum matrix composites , manufactured diffusion bonding process, ensure the antenna azimuth space maneuver flight, it also because it has good electrical conductivity, so as to improve the function of the waveguide, safeguard electrical signal transmission between the spacecraft and antenna reflector, the entire unit 63% lighter than the carbon/epoxy materials.
2.3 ceramic matrix composites
Ceramic matrix composites, with their excellent high temperature resistance and high temperature mechanical properties, have become the candidate of thermal structure materials and have a very important application prospect in the missile field. The United States, France and other countries have conducted in-depth studies, designed the C /SiC composite sandwich structure with cooling structure for long-term flight and working missiles, and developed the scramjet combustion chamber with active cooling structure .
At present, the French academy of aeronautics and astronautics has used fiber winding method to produce tube parts with a diameter of 150 mm and a length of 100 mm and other complex shape components. The manufacturing maturity of the new material is said to have reached level 4.
Test pieces of the preliminary test shows that the material which can withstand temperatures up to 1 000 ℃, can satisfy the first phase of the "hypersonic aircraft flight plan requirements; The second phase will increase the material heat-resisting temperature to 2000 ℃ above, to suit the requirements of the speed more than 8 Mach. The advent of new ceramic matrix composites has provided new possibilities for missile and aerospace vehicle materials to improve high temperature strength, toughness, oxidation resistance and significantly reduce costs.
After years of development, the supporting technology of composite materials has become mature, and the following research needs to be strengthened:
(1) develop new low-cost lightweight composite materials; (2) develop intelligent composite material preparation technology; (3) enhance the development of micro-nano composite technology.
Special functional materials
In order to meet the requirements of heat prevention and heat insulation when re-entering the atmosphere of manned spacecraft's re-entry capsule, reusable launch vehicles (such as the space shuttle), intercontinental missiles and other re-entry vehicles, as well as space protection of low-orbit spacecraft, the foreign space field has actively developed and applied special functional materials.
3.1 high temperature alloy materials
High temperature alloys are important materials for aerospace engine components . The traditional high temperature alloy is close to the upper limit of its operating temperature, so it cannot further increase the operating temperature by adjusting the composition ratio, but can only resort to new technological approaches, such as directional solidification high temperature alloy.
The U.S. space agency NASA Marshall space flight center has developed a diffusion-enhanced molybdenum-rhenium alloy that USES vacuum plasma spraying to make high-temperature components. The high temperature performance of the developed molybdenum - rhenium alloys was improved compared with other non-dispersive - enhanced molybdenum - rhenium alloys.
DARPA grant kratos stark companies in the United States "small business innovation research program" project, application of the technology of material design, research and development has a greater ductility, oxidation resistance and 1 300 ℃ above creep performance of molybdenum alloy. The company plans to develop program structures and structural performance models based on a traditional database of multicomponent thermodynamics and flexibility, and use these tools and models to design advanced molybdenum alloys that can be manufactured through traditional processes. The improved molybdenum alloys are expected to be used in the next generation of carrier rocket components.
3.2 multi-layer thermal insulation materials
Multilayer insulation materials insulate by reducing the transmission of heat radiation.
NASA Goddard space center in the United States has developed aerogel matrix multilayer insulation material for the protection of microfluidic stars . This material integrates ultra-low density, high hydrophobicity and fiber-reinforced aerogel materials (2.5-3.8cm thick aerogel layer) into multi-layer thermal insulation materials to form integrated thermal insulation materials. Aerogels have high compressive strength and can resist high speed impact. Multilayer thermal insulation materials have very effective thermal insulation performance, the two together, so that this integrated thermal insulation materials have excellent thermal performance and significant robustness, so as to achieve real microfluidic star protection.
The disadvantage of multilayer heat insulation materials is that the cost is too high, and it needs to be reduced for promotion and application.
3.3 thermal protection materials
Thermal protection material is an important part to protect the aircraft from the thermal environment damage when flying at high speed.
Since 1960, the United States has developed a series of ceramic insulation tiles.
This is an important candidate material for the thermal insulation design of hypersonic vehicles in the United States. Europe's ultra-high speed supersonic aircraft also use techniques similar to insulation tiles, such as Germany's use of porous nanomaterials as insulation layers and Russia's use of fiberglass as thermal protection for cruise missiles.
In recent years, France's airbus defense and aerospace company (ADS) has completed the construction of two heat shields needed for the European Exo Mars mission .
Before and after the tank has two heat shield, among them former heat shield diameter of 2.4 m, the quality of 80 kg, by covering 90 piece of thermal protection tile carbon sandwich structure, phase in earth's atmosphere will suffer more than 1 850 ℃ high temperature; The rear heat shield has a mass of only 20 kg and consists of 93 heat shields of 12 different types fixed to the carbon structure, including a parachute deployed during a descent phase. The probe's scientific instruments are integrated into the front heat shield and the rear heat shield is assembled before the final assembly of the launch preparation. The company, which has successfully developed the heat shield for the huygens probe, is working on the next generation of thermal protection materials and systems for the return of samples from outer planets or space stations.
Ultra high speed aircraft to carry into the atmosphere when high temperature over 2000 ℃, and ultra high temperature ceramics in 3 above 000 ℃, melting point is an ideal candidate materials. Researchers at the advanced structural ceramics center at imperial college London, UK, have not only tested the applicability of ultra-high temperature ceramics in the aerospace field.
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