At the Paris International Aviation Fair in 1983, the two largest aluminum alloy manufacturers in the world, Alcon Aluminum Corporation of the United Kingdom and Alcor Aluminum Corporation of the United States, also announced the successful development of a new revolutionary material-aluminum-lithium alloy. Experts believe that aluminum-lithium alloy is another milestone in aluminum alloy research and development since the invention of aluminum-zinc high-strength alloy in 1943.
In fact, aluminum-lithium alloy is not a new concept. The understanding of this material has gone through a long time. Due to its small specific gravity and high solubility in aluminum, people have long regarded lithium as a close partner of aluminum. As early as the 1920s, scientific and technological workers made many comments on aluminum-lithium alloys. In 1924, Germany successfully developed an industrial aluminum-lithium alloy—Skelong. This is an aluminum-zinc alloy containing only 0.1% lithium. Its mechanical properties are slightly better than the prevailing aluminum-magnesium alloy-Duralumin. As Duralumin was recognized at that time, it affected the extensive attention that Scroton should receive. In 1943, the introduction of high-strength aluminum-zinc-magnesium-copper alloys once again underestimated the industrial value of aluminum-lithium alloys. In 1957, Britain successfully developed the X-2020 aluminum alloy containing 1.1% lithium. This alloy is used on the skins of the wings and horizontal tail of the US carrier-based supersonic attack aircraft. After replacing the aluminum alloy in the original design, the weight of the RA-5C aircraft is reduced by 6%. Scientists in the former Soviet Union also developed an aluminum alloy containing 2% lithium. After another 10 years of wandering, after the worldwide energy crisis occurred in 1967, countries have restarted large-scale research on aluminum-lithium alloys. Due to the development of metallurgical technology and related technologies, the emergence of aluminum-lithium alloys with larger lithium content, smaller specific gravity and higher strength has become possible. It is believed that many advanced fighter jets and civil aviation aircraft mostly use this alloy. The cost of aluminum-lithium alloy is only about 1/10 of that of carbon fiber reinforced plastic. If the aluminum-lithium alloy is used to make Boeing aircraft, the weight can be reduced by 14.6%, the fuel can be saved by 5.4%, the cost of the aircraft will be reduced by 2.1%, and the annual flight cost of each aircraft will be reduced by 2.2%. It can be expected that with the development of materials science, more and more new alloys will enter the aerospace industry, various industrial sectors and thousands of households.
Aluminum-lithium alloy is mainly developed for weight reduction of aircraft and aerospace equipment, so it is also mainly used in the aerospace field. It is also used in ordnance and nuclear reactor materials, tank armor-piercing bombs, torpedoes and other weapon structural parts, in addition to automobiles and robots. And other fields are also fully used. Beginning in the 1930s, Germany, the United States, Britain, and the former Soviet Union developed Al-Li alloys, but the real commercial value was the 1.1% lithium-containing 2020 alloy developed by Alcoa of the United States in 1957, which was used to make the navy. The horizontal stabilizer of the wing skin and tail of the TA-5CVigitante aircraft. The main aluminum-lithium alloys used are 2××× series (Al-Li-Cu-Zr) and 8××× series (Al-Li-Cu-Mg-Zr) and more than 10 grades, and the maximum ingot specification reaches 25t Above, its rolling, extrusion and forging processing technology has reached the level of conventional aluminum alloys.
Aviation applications of aluminum-lithium alloys
Al-Li alloy has been used or tried on military aircraft, civilian airliners and helicopters, mainly for fuselage frames, flaps and wings, vertical stabilizers, fairings, intake lip, hatch, fuel tanks, etc.
As early as the 1950s, the United States developed the x2020 aluminum-lithium alloy and later used it to replace 7075 for RA-SC early warning aircraft. An American company uses C-155 aluminum-lithium alloy for the vertical and flat tails of Boeing 777 and Airbus A330/340 aircraft. This alloy has better fatigue resistance and higher strength than ordinary aluminum alloys. Among them, each A330/340 aircraft uses 650kg of Al-Li alloy, which can reduce the weight of the aircraft by 4250kg, which can increase the effective load and reduce fuel consumption. McDonnell Douglas C-17 transport aircraft uses aluminum-lithium alloy plates and extruded profiles to manufacture cargo compartment floor beams, flaps and aileron skins and other structures. The amount is up to 2.8t, which is 208kg lighter than ordinary aluminum alloys. The French Phantom A large number of aluminum-lithium alloys are also used in fighter jets, and their cost is lower than thermoset plastics and metal matrix composites. In 1988, Lockheed Martin Tactical Aircraft Systems, Lockheed Martin Aviation Systems, and Reynolds Metals began a joint plan for the development of AA2l97 alloy to produce heavy-duty thicknesses for military fighter plane partitions and bulkheads. board. In June 1996, Reynolds Metals began to sell the first batch of AA2l97 alloy plates, which were used to replace other materials to manufacture the rear partitions (bulk walls) and other parts of the US Air Force F-16 aircraft. The front of the European experimental fighter EFA is made of 8090 thin plates, accounting for 9% of all materials, and a lot of A1-Li alloys are used in the cockpit. Among them, the electronics are manufactured by the A1-Li superplastic forming process. The cover of the equipment room is 1.5m long. A large number of A1-Li alloy plates and forgings are used on the frame, skin and internal structure of the large helicopter EH101 jointly produced by Britain and Italy, and the weight of each aircraft is reduced by 200kg. It is estimated that the economic benefit of the helicopter will increase by as much as 3000 pounds for every 1kg lightened during the entire service period.
In the research and application of aviation aluminum-lithium alloys, the former Soviet Union and Russia have always been in the leading position in the world. The more representative ones are 01420, 01421 (including scandium), 01423 (including scandium), 01430, 01440, 01450, etc. As early as the 1970s, the former Soviet Union used aluminum-lithium alloys to manufacture the main components of the Yak-36 aircraft, including the fuselage skin, tail, and wing ribs. The aircraft used in harsh ocean climate conditions with good performance. . In the early 1990s, 1420 alloy welded structures were used on MiG-29 and MiG-31 aircraft to further improve the weight reduction effect. MiG-29 uses 1420 alloy sheet, die forgings, extruded wall panels, etc. to manufacture the fuselage, cockpit, fuel tank, etc. The amount of aluminum-lithium alloy used for each aircraft is 3.8t. After using the welded fuel tank, the weight was reduced by 24%, of which 12% was due to the reduction in the proportion of materials, and 12% was achieved due to the reduction of rivets, screws, sealants and overlapping parts in the welded structure. The 1420 alloy is also used in other aircraft, such as transport aircraft, passenger aircraft, and helicopters. The dosage of An-124 is nearly 8t, the dosage of Figure-204 is 2.7t, the dosage of Mi-26 is 1.8t, and the Il-86 and An-72 also use Al-Li alloy. In recent years, Al-Li alloy has also been widely used in Su-27, Su-35, Su-37 and other fighters, as well as long-range missile warhead shells.
Aerospace applications of aluminum-lithium alloys
For the spacecraft structure, the reduction of mass can increase the effective load, and each increase of 1kg of the effective load can bring benefits of 4,400 to 110,000 US dollars. Therefore, due to the low density and good performance of Al-Li alloys, Al-Li alloy structures are used in many aerospace vehicles.
The aircraft manufactured by the American Lockheed Missile and Space Company (LMSC) uses low-density, medium-strength and high-rigidity materials, so a large number of Al-Li alloy products are used. Since the mid-1980s, a large number of 8090 and common processing methods have been used to produce various forgings, thick plates, thin plates and extrusions. LMSC uses 8090 plates on the Hercules payload adapter to reduce the weight by 180kg. The company uses AA2195 alloy to produce the new space shuttle "ultra-light fuel tank", which is 47m long and 8.4m in diameter, which is used to hold cryogenic fuel and liquid hydrogen. The use of AA2195 alloy reduces the fuel tank by 5% (weight reduction of nearly 3400kg), increases the strength by 30%, effectively increases the effective load, and saves about 75 million US dollars in cost. McDonnell Douglas Space Systems uses 2090-T81 plates to make a 2.44m diameter and 3.05m long cryogenic box for the delta-wing rocket containing fuel and liquid oxygen containers, reducing the mass by 15%. The three components of the US General Dynamics Space Company on Atlas and Centaur launch vehicles use 2090 alloy, the total amount is 70kg, and the mass is 8% less than 2024. In December 1997, the outer tank of the US Space Shuttle Endeavour replaced 2219 with 2195, which increased its carrying capacity by 3.4t.
Al-Li alloys also have many applications in the Russian aerospace industry. Russia added 0.20% Sc element on the basis of 1450 alloy to develop 1460 alloy, which has better performance, and applied it to the structural parts of the large-scale launch vehicle "Energy". In addition, it is also used on the structural parts of other rockets, the space shuttle "Blizzard" and the space station.