Aluminum alloy has the advantages of light weight, high specific strength and corrosion resistance. Aluminum alloy has been developing with the progress of aviation industry since the world's first aircraft made of aluminum alloy in 1903. Lithium is the lightest metal element. For every 1% increase in lithium in aluminum alloy, the density of aluminum alloy can be reduced by 3% and the modulus can be increased by 6%. In addition to the above advantages, aluminum lithium alloy materials can also greatly improve the fatigue resistance and low-temperature toughness. Therefore, Al Li alloy has become an important aviation material for all countries.
The research and development of Al Li alloy has roughly experienced three stages. The first generation is 2020 and ba Д 23 is the representative; The second generation is represented by 1420 and 2090; At present, it has developed to the third generation of aluminum lithium alloys, which have good comprehensive properties. Recently developed and improved 1460, 2198, 2199, 2050 and other aluminum lithium alloys are widely used in advanced large passenger aircraft and spacecraft. In order to meet the needs of aerospace industry, the world's large aluminum companies and scientific research institutions have begun to develop the fourth generation of aluminum lithium alloys. Compared with the third generation, the lithium content of the new generation of aluminum lithium alloys will be reduced, while the strength and fracture toughness will be improved, the elongation will be reduced, and other properties can still reach or even exceed the level of the third generation of aluminum lithium alloys.
At present, foreign countries with complete Al Li alloy production system are mainly distributed in five developed regions, namely, the United States, Russia, Britain, France and Italy, with a total production capacity of about 200000 t / A. These countries have established a complete system of melting casting processing, in which melting casting is the key process for the production of aluminum lithium alloy materials. The United States is at the forefront of the world in the R & D, production and application of aluminum lithium alloys. Its production capacity accounts for about 50% of the world. Its products cover plate, strip, extrusion, rod, wire and forging. The representative alloys include weldlite, airware, 2099, 7055, etc. the main production enterprises include okunink aluminum company, kenlian aluminum company and Aleris aluminum company. Okonenko Aluminum Co., Ltd. is the largest aluminum lithium alloy manufacturer in the world, with a production capacity of about 55000 T / A. okonenko's production capacity is mainly distributed in Davenport rolling plant, Lafayette forging and extrusion plant, Langwei Aluminum Co., Ltd., kitzgreen Aluminum Co., Ltd., Italy Fusina Aluminum Co., Ltd. and Changyuan extrusion plant in South Korea; The main customers include Boeing, Airbus, Lockheed Martin, Gulfstream aerospace, COMAC and many other large civil and military aircraft
manufacturer. The production of aluminum lithium alloy of kenlian Aluminum Co., Ltd. is completed in the izouar rolling plant in France, with a production capacity of about 14000 T / A. its main customers include European aerospace, Airbus and Bombardier. Aleris aluminum's aluminum lithium alloy production plant is located in Koblenz, Germany. In the 1950s, the United States used the earliest industrial aluminum lithium alloy 2020 on ra-5c early warning aircraft, reducing the total weight of the aircraft by 6%; After the 1990s, the third generation aluminum lithium alloy was used in the F-16 rear spacer frame, Boeing 787 girder and the outer storage box of the space shuttle Endeavour, and achieved good weight reduction results. The C-17 transport aircraft uses 2.8T aluminum lithium alloy plate and extruded profile to make the floor beam, flap, aileron skin and other structures of the cargo compartment, which is 208kg lighter than that of ordinary aluminum alloy.
Russia's R & D, production and application of Al Li alloy began in the former Soviet Union. It is the second largest R & D, production and application country in the world after the United States; The production capacity accounts for about 25% of the world, and the types of processed materials are similar to those in the United States. The representative alloys include 1420, 1450 and 1460. The production enterprises are mainly Ural kamensk Aluminum Co., Ltd., a Russian United aluminum company, and the market is mainly for the domestic aerospace sector. In the early 1970s, Russia used 1420 Al Li alloy for MiG-29
The weight reduction effect of fuselage, fuel tank, cockpit and other parts reaches 24%; When it comes to the third generation of Al Li alloy, Russia will also use the new Al Li alloy in the liquid hydrogen storage tank of the space shuttle blizzard, MiG-29, Su-27, Tu-144 and other civil and military aircraft. For example, the consumption of Al Li alloy of each MiG-29 aircraft is up to 3.8t, and the consumption of Su-27 Al Li alloy accounts for 3% of the total weight of the fuselage.
The R & D, production and application of aluminum lithium alloy in Europe are distributed in Britain, France and Italy. These countries have lagged behind the United States and Russia in the R & D of the third generation aluminum lithium alloy, and the production is carried out by the branches of American companies in Europe. For example, the former French Puji aluminum company has been incorporated into the United States Ken Lian aluminum company; Kitzgreen rolling plant in the UK and Fusina rolling plant in Italy are all part of okonenko aluminum company in the United States. Users include Airbus, Agusta Westland, Eurofighter, etc. All sheet parts in the front of the Typhoon fighter are made of 8090 aluminum lithium alloy sheet, accounting for 9% of all materials. The cover plate of the electronic equipment room in the cockpit is up to 1 5m; The frame, skin and internal structure of eh101 helicopter fuselage are largely made of aluminum lithium alloy plates and forgings,
The weight of each aircraft is reduced by 200kg.
Aluminum lithium alloy has been used in military aircraft, civil airliners, helicopters and spacecraft. It is mainly used in fuselage frame, flap rib, vertical stabilizer, fairing, inlet lip, hatch, fuel tank, etc. In the design and manufacture of new aircraft, light weight and weight reduction are often "debated" in the aviation field. The use of aluminum lithium alloy can reduce the mass of aircraft aluminum alloy parts by 14% ~ 30%. The effect of weight reduction is that the annual flight cost of each aircraft will be reduced by 2.5% More than 2%, so Al Li alloy is considered to be the most ideal structural material for aerospace.
At present, China has made three key strides in the general aircraft manufacturing industry, namely the regional jet ARJ21-700, the single channel jet C919 and the dual channel jet c929. Aluminum parts of ARJ21-700 aircraft mostly use hard aluminum alloy materials such as aluminum copper alloy and aluminum zinc alloy, but aluminum lithium alloy has not been applied. The third generation aluminum lithium alloy is used in the fuselage skin, truss, floor beam, slide rail, boundary beam, floor support structure and other components of C919 large aircraft, and the aluminum lithium alloy material of the whole aircraft accounts for 15.5% 5%, the dosage reached 14T, and the good effect of comprehensive weight reduction of 7% was achieved. Aluminum lithium alloy plates are widely used in the front straight section of C919 fuselage manufactured by AVIC Hongdu and the large parts of C919 fuselage and aileron manufactured by AVIC Xi'an. However, the third generation aluminum lithium alloy used by C919 large aircraft is from okunink aluminum. In June 2018, the overall shape and dimensions of the c929 long-range wide body airliner were officially determined, and the preliminary design (G3) is under way. It can be determined that the third generation or even the fourth generation aluminum lithium alloy will be widely used in c929 aluminum parts in the future.
In addition to a large number of applications in civil aircraft, another major application market of aluminum lithium alloy is military aircraft. According to statistics, in 2017, the number of Chinese military combat aircraft reached 1453, mainly the second and third generation combat aircraft, accounting for 10% of the world, only half of that of the United States, ranking second. With the improvement of China's national strength, in order to alleviate the pressure of land transportation and protect homeland security and overseas interests, the state has continuously increased its investment in the aerospace industry. During the 13th Five Year Plan period, the Chinese air force will usher in the "third five year plan"
The "third generation and a half" fighters include the replacement peak of j-10c, j-11d, j-16 and su-35sk. The scale of "third generation and a half" fighters will leap to the second in the world. The production capacity of these tactical aircraft is expected to exceed 115 aircraft / year, and the fourth generation fighters j-20 and j-31 have been in service. In addition, the production capacity of strategic aircraft is about 10 aircraft / year, It has become the country with the highest output of military aircraft in the world, and this situation will not change greatly in the next decade. If it is produced at this rate, the annual demand of aluminum lithium alloy for Chinese military aircraft will reach nearly 500t.
Aluminum lithium alloy can be used in the aerospace field to manufacture space shuttle fuel tank, rocket fuel storage tank and space station structural parts. To sum up, the average annual demand of domestic civil and military aircraft in the next decade will reach about 550, and the annual demand of aluminum lithium alloy materials will be more than 1500t.
At present, Chalco aluminum has carried out basic research on aluminum lithium alloy, and can produce and replace imported products to meet the needs of aluminum lithium alloy for domestic military and civil aircraft.
