Copper is a malleable, ductile and excellent conductor of heat and electricity. It is used in various industries, including electrical, construction, automotive, and plumbing. There are different grades and standards of copper materials, and here are some of them:
In recent years, while continuing to pay attention to the safety of aircraft and engines, the domestic and foreign aviation community is also increasingly concerned about saving resources, reducing costs, protecting the environment and other issues. Under this background, the green aviation industry has made certain progress. Green aviation covers the whole development and use process of aircraft design, manufacturing, use, maintenance, retirement, recovery, etc., involving technical fields including green materials, green manufacturing, green maintenance, etc.
The so-called green material refers to the maximization of resource utilization and the minimization of use cost and environmental impact during the whole cycle of material design, raw material selection, processing and manufacturing, packaging and transportation, use, recovery and reuse. Our country has begun to vigorously develop new material technology, each new material technology has been made a breakthrough, aviation new material research has made gratifying achievements. Looking into the future, new aviation materials will be developed in the direction of multi-purpose, high performance, new processes, low cost and new concepts. With the improvement of China's independent research and development level in the field of new aviation materials, we need to comprehensively improve the technical level of green aviation materials from the aspects of material design, preparation process, material development, recycling and other aspects, and jointly create a better future of green aviation.
First, the necessity of developing green aviation industry
2021 is the first year of the 14th Five-Year Plan. As the core position of the entire military industry chain, the new material sector is expected to usher in a larger space for development. The 20th century is a century of rapid development of modern science and technology, one of the important symbols is the brilliant achievements human beings have made in the field of aeronautics and astronautics. In the 21st century, the aerospace industry has shown a broader prospect for development, and high-level or ultra-high level aerospace activities have become more frequent. The great achievements of aerospace industry are inseparable from the development and breakthrough of aerospace material technology. Materials are the foundation and forerunner of modern high technology and industry, and to a large extent are the prerequisite for the breakthrough of high technology. The development of aerospace materials plays a strong role in supporting and guaranteeing the aerospace technology. In turn, the development needs of aerospace technology greatly lead and promote the development of aerospace materials. It can be said that the progress of materials plays a key supporting role in the upgrading of aircraft.
Aeronautical materials are not only the material guarantee for the development and production of aeronautical products, but also the technical basis for the upgrading of aeronautical products. Materials play an important role in the development of aviation industry and aviation products. In the 21st century, aviation materials are developing towards the direction of high performance, high function, multi-function, structure and function integration, compound, intelligent, low cost and environment compatibility.
In his 2022 government Work report, former Premier Li Keqiang proposed to continuously improve the ecological environment, promote green and low-carbon development, strengthen pollution control and ecological protection and restoration, strike a balance between development and emission reduction, and promote harmonious coexistence between man and nature. In recent years, while continuing to pay attention to aircraft safety, the domestic and foreign aviation community is also increasingly concerned about resource saving, cost reduction, environmental protection and other issues. In this context, green aviation has made certain progress. Aircraft towards more safe and reliable, lightweight, tough, green direction of development, thus put forward higher and higher requirements for materials, but also promote the aircraft in flight speed, reliability, low cost, high efficiency and comfort and other aspects of the upgrade. Under the new industrial situation, developing high-end aviation green materials and its preparation and processing technology is of great significance to support the sustainable development of Chinese aviation industry. In a word, driven by the rapid development of global modern industry, the green development of aviation materials is an inevitable trend and an urgent requirement of economic development.
Ii. Research progress of new aeronautical materials
Aircraft materials to some extent determine the cost of manufacturing aircraft body structure. Since China's aviation equipment was mainly introduced in the early stage, it mainly uses the foreign material system in the material selection. In recent years, China has begun to vigorously develop new material technology, and the new material technology has made continuous breakthroughs, and the research on new aviation materials has also made gratifying achievements. However, there is still a large gap between the overall level of aviation new material industry and the international advanced level.
(A) Titanium alloy: excellent properties of the "universal metal"
Titanium has the characteristics of low specific gravity and high specific strength, and its alloy is of great significance for increasing thrust-weight ratio of aircraft in the aerospace field, and has been widely used in recent years. In addition to military and aerospace fields, titanium alloy is also widely used in chemical, metallurgy, medical, sports and leisure and other fields.
Development status of titanium alloy materials for aviation abroad
1) High-temperature titanium alloy: high-temperature titanium alloy is mainly used in aircraft flap slide rail, bearing housing, bracket, engine hood, compressor disc and blade, casing and other structural frame parts. These components require high specific strength, fatigue strength, creep resistance and structural stability at 300 ~ 600℃. At present, on behalf of the international advanced level of high temperature titanium alloy brands mainly include the United States Ti-6242S, Ti-1100, IMI834, Russia's BT36 and so on.
2) High strength titanium alloy: High strength titanium alloy usually refers to the tensile strength of more than 1000MPa titanium alloy, mainly used to replace the high-strength structural steel commonly used in aircraft structure, can achieve 10% weight reduction. At present, the high strength titanium alloys used in aircraft are mainly β-type titanium alloys, representative of the main Ti-1023, BT22, Ti-153, β-21S and so on.
3) Flame retardant titanium Alloy: Currently, the typical flame retardant titanium alloys are Alloy C in the United States and BTT-1 in Russia. Alloy C (Ti-35V-15Cr), developed in the United States, is a β-type titanium alloy with good high-temperature strength and oxidation resistance. It has been applied to the high-pressure compressor casing, guide vane and vector-tail nozzle of Fl19 engine. Ti-Cu-Al BTT-1 flame retardant titanium alloy developed in Russia has good thermal workability and has been used in engine compressor casing and blades.
Development status of titanium alloy materials for domestic aviation
1) High temperature titanium alloy: Ti-60 alloy is a 600℃ high temperature titanium alloy independently developed by our country. The alloy is based on TAl₂ (Ti-55) alloy adding Al, Sn, Si elements with appropriate content, so as to further improve the thermal stability, high temperature creep and high temperature oxidation resistance of the alloy.
2) High strength structural titanium alloy: A batch of high strength structural titanium alloy was independently developed in the 1970s to 1990s. The strength of these titanium alloys can reach the level of 1100-1300MPa. At the beginning of the 21st century, there are two kinds of representative beta titanium alloy: ① nearly β titanium Ti-B18, tensile strength can reach 1150 ~ 1350MPa; ② Metastable β titanium alloy Ti-B20, tensile strength up to 1200 ~ 1600MPa.
3) Flame retardant titanium alloy: Over the years, China has conducted in-depth research on flame retardant titanium alloy. Referring to AlloyC alloy, Ti-V-Cr-Al, Ti-Mo-Cr-Al, Ti-Mo-V-Cr-Al3 series of flame retardant titanium alloys were designed respectively, and the anti-combustion mechanism was studied by means of computer simulation. In addition, TF1(Ti-V-Cr-C series) and TF2 (Ti-Cu series) flame retardant titanium alloys were designed after systematic analysis of different systems of the United States, Britain and Russia. Ti-40 (Ti-V-Cr-Si) alloy is a β-type flame retardant titanium alloy independently developed in China. Compared with conventional titanium alloy, Ti-40 alloy has excellent flame retardant and mechanical properties. At present, the alloy research has developed from the laboratory scale to the semi-industrial scale, has been able to prepare Ti40 ton ingot, large size bar and ring forgings.
Due to the late start of the domestic aviation manufacturing industry, titanium and titanium alloy materials in the domestic aviation field consumption is not large, titanium materials used in the aviation field accounted for less than 20%, far below the international average level of about 50%, and titanium industry compared to developed countries there is still a large gap: First, high-end titanium alloy products are still mainly imitation, the level of material development is low, the range of application is narrow, high comprehensive performance and low-cost titanium alloy development is mostly in the laboratory stage; Second, the quality of metallurgy is not stable, fewer varieties, incomplete specifications; Third, the research progress of related supporting technologies is slow, and the self-developed titanium alloy material system needs to be improved.
(2) Superalloy: focusing on the needs of military engines
Superalloy, for high temperature
Traditional steel softens above 300 degrees Celsius and cannot cope with high temperatures. In order to pursue higher energy conversion efficiency, the field of thermal engine power needs higher and higher working temperature. As a result, superalloys have been bred to work stably at temperatures above 600 degrees Celsius, and the technology continues to improve.
Superalloys are divided into iron - based superalloys and nickel - based superalloys according to the main elements of the alloy. According to Zhiyan Consulting, divided by product process in 2018, the output of nickel-based superalloy accounted for 80%, iron based superalloy 14.3% and cobalt based superalloy 5.7%.
Superalloy is the key material of aeroengine. Superalloy has been used in aeroengine since its birth and is an important material for aerospace engine manufacturing. The performance level of the engine largely depends on the performance level of the superalloy material. In modern aero-engines, the amount of superalloy material accounts for 40% ~ 60% of the total weight of the engine. It is mainly used in four hot end components: combustion chamber, guide, turbine blade and turbine disc. In addition, it is also used in casing, ring parts, afterburner and tail nozzle.
The Chinese high-temperature alloy industry is currently in the growth period, and the industrial chain enterprises have broad development space in the future. The number of superalloy production enterprises in China is limited, and the production level lags behind that of the United States, Russia and other countries. However, in recent years, the production capacity and output value have been significantly improved. Many superalloy production capacity projects of Lianshi Aviation, Western Superconductor and other companies are under construction and put into operation.
The properties of superalloy for aeroengine are developing continuously
1) Iron base superalloy: one of the characteristics of Chinese superalloy system.
Due to the lack of nickel and little cobalt in Chinese resources, the development, production and application of iron base superalloy became a brilliant scene in the 1960s and 1970s.
Iron-based superalloys are generally used in engine parts with low operating temperatures (600~850 ° C), such as turbine discs, casing and shafts. However, Fe-base superalloy has good mechanical properties at medium temperature, comparable to or better than similar nickel-base alloys. Besides, it is cheap and easy to deform in hot working. Therefore, Fe-base superalloy is still widely used as turbine disc and turbine blade materials in the field of medium temperature.
2) Nickel base superalloy: deformation/casting/new alloy upgrade by generation.
Nickel-based superalloys generally work under certain stress conditions above 600℃. They not only have good oxidation resistance and corrosion resistance at high temperature, but also have high temperature strength, creep strength and lasting strength, as well as good fatigue resistance. It is mainly used in the aerospace field for structural components working under high temperature conditions, such as the working blades, turbine disks, combustion chambers of aeroengines, etc.
According to the manufacturing process, nickel base superalloy can be divided into variable alloy, casting superalloy, new superalloy. Nickel-based cast superalloy is mainly used in turbine guide blades in engines, where the operating temperature can reach more than 1100°C, or can also be used in turbine blades, whose temperature is lower than the corresponding guide blade 50-100°C.
As the heat resistant alloy working temperature is higher and higher, the strengthening elements in the alloy are more and more, the composition is more complex, resulting in some alloys can only be used in the cast state, can not be hot working deformation. In addition, the increase of alloying elements makes the composition segregation of nickel base alloy serious after solidification, resulting in uneven microstructure and properties. Using powder metallurgy process to produce superalloy can solve the above problems. Because the powder particle is small, the cooling speed is fast when powder is made, the segregation is eliminated, the hot workability is improved, the alloy that can only be cast is changed into the deformation superalloy that can be hot worked, the yield strength and fatigue properties are improved, the powder superalloy has produced a new way for the production of higher strength alloy. Powder superalloy is mainly used in the manufacture of turbine disc of advanced aero-engine with high thrust ratio, and also in the production of compressor disc, turbine shaft, turbine baffle and other high temperature hot end parts of advanced aero-engine.
3) cobalt-based superalloy: corrosion resistance and other special fields have broad prospects.
The oxidation resistance of cobalt-based superalloy is poor, but its thermal corrosion resistance is better than nickel. Cobalt-based superalloy also has stronger high-temperature strength, thermal corrosion resistance, thermal fatigue and creep resistance than nickel-based superalloy, which is suitable for manufacturing gas turbine guide blades and nozzles.
Due to limited resources, cobalt base alloys such as K40, GH188 and L605 have been developed in our country. Since 2001, GE's research in cobalt-based superalloys has focused on using cobalt-based superalloys as substrate materials for gas turbines and preparing coatings such as thermal barrier coatings on the surface of the alloys to improve corrosion resistance.
Because of material limitations, cobalt is relatively rare and expensive on Earth. At present, the heat of cobalt-based research has decreased, and many scientific researches remain in the theoretical stage such as digital modeling experiment.
The first generation of military aircraft alloy, engine with high temperature alloy or enter the rapid volume period
The temperature requirements of the engine are increasing. A high thrust-to-weight ratio requires a higher nozzle temperature and a material support at a higher operating temperature. In the development of superalloy in the world, engine blade and disc materials have experienced four stages, namely deformation, casting, orientation and single crystal. The temperature is gradually increased from 600°C to more than 1100°.
The upgrading of military aircraft has been accompanied by the upgrading of superalloys. The core material of the first generation turbofan engine is deformed superalloy, and the working temperature of the core material is 650°C. By the fourth generation turbofan engine, the working temperature of the core material has reached 1200°C, and the single crystal superalloy is adopted. The upgrading of military aircraft has been accompanied by the upgrading of superalloy, the core material of engine. The upgrade of superalloy needs research