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Dr. Dmitri Kopeliovich
Aluminum-lithium (Li) alloys were developed for reducing weights of aircraft and aerospace structures.
Aluminum-lithium alloys have decreased density because of very low density of metallic lithium 33.7 lb/ft³ (540 kg/m³). Addition of 1% of lithium results in decreasing density of the alloy by 3%.
Aluminum-lithium alloys may contain also copper (Cu), magnesium (Mg), zirconium (Zr) and silver (Ag) as minor alloying elements.
Aluminum-lithium alloys are heat-treatable.
Solution treatment followed by either artificial or natural aging allows considerable increasing the yield strength (3-5 times). Ductility of the alloy decreases as a result of the heat treatment.
Hardening of the alloys from this group is achieved due to precipitation of the phases Al3Li, Al2CuLi or Al2CuMg occurring during aging.
Aluminum-lithium alloys possess increased Modulus of Elasticity, high specific stiffness,increased fatigue strength and cryogenic strength. Alloys, containing silver, have also good weldability. Zirconium is added to aluminum-lithium alloys for controlling grain structure during heat treatment.
Aluminum-lithium alloys are used for manufacturing aircraft structures, aerospace vehicle skins, spacecraft fuel tanks (liquid Hydrogen and oxygen).
| Designation | Li,% | Cu,% | Mg,% | Zr,% | Other,% |
|---|---|---|---|---|---|
| 2020 | 1.3 | 4.5 | - | - | Mn 0.5, Cd 0.25 |
| 2090 | 2.2 | 2.7 | - | 0.12 | - |
| 2091 | 2.0 | 2.1 | 1.5 | 0.10 | - |
| 8090 | 2.4 | 1.3 | 0.9 | 0.1 | - |
| 8091 | 2.6 | 1.9 | 0.9 | 0.12 | - |
| 8092 | 2.4 | 0.65 | 1.2 | 0.12 | - |
| Weldalite 049 | 1.3 | 4.5 | 0.4 | 0.14 | Ag 0.4 |
| 1420 | 2.0 | - | 5.2 | 0.11 | - |
aluminum concentration - balance
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