PROCESSING AND APPLICATION OF Al-Li ALLOYS

1. PROCESSING AND APPLICATION
OF Al-Li ALLOYS
THIRUNAVUKARASU.H
13MY12
1/26/2017Friday, September 19, 2014
PSG COLLEGE OF TECHNOLOGY
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2. Aluminum–lithium alloys (Al-Li)
 Aluminum and lithium, often also including copper
and zirconium.
 Since lithium is the least dense elemental metal these alloys are
significantly less dense than aluminum.
 Commercial Al–Li alloys contain up to 2.45% by weight of
lithium
 The crystal structure for Al3Li and Al–Li, while based on the FCC
crystal system
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3. GRADES
 Three structures are 2195 and 2090 alloys.
 Al 2195 is an Al-Li alloy designed by Lockheed Martin and
Reynolds for storage of cryogenics.
 Al 2090 is a commercially available Al-Li alloy.
 Weldalite 049 that were introduced in the 1980s.
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4. Composition of aluminum-lithium alloys (wt. %)
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Alloy Cu Li Zr Others
2090 2.7 2.2 0.12 -
2091 2.1 2.0 0.1 -
8090 1.3 2.45 0.12 0.95 Mg
Weldalit
e
049
5.4 1.3 0.14 0.4 Ag
0.4 Mg
zirconium (Zr) are added to control the grain
microstructure during heat treatment

5. Mechanical properties of typical
near-peak aged AL-Li alloys
Alloy
Density
(g/cm3)
Ductility
( El % )
Elastic
Modulus
(GPa)
Tensile
Strength
(MPa)
Longitudin
al
Klc
(MPa
m1/2)
Melting
Temperatur
e
(oC)
2090 2.59 3-6 76 500 44 580-660
2091 2.58 6 75 550 >130 560-670
8090 2.55 4-5 77 480 75 600-655
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The 2090 alloy also offers superior corrosion resistance in
salt-spray (marine) environment than 7075-T6.

6. Processing of Al Li alloys
 Melting and Casting of Aluminum–Lithium Alloys
 Mechanical Working of Aluminum–Lithium Alloys
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7. Mechanical working
 Mechanical working of Al–Li alloys is primarily concerned with
aerospace alloy rolled products
 sheet and plate, extrusions, and to a lesser extent forgings.
 fabricated by hot working with intermittent and final heat
treatments.
 TMP can be rather complex for the modern 3rd generation Al-Li
alloys, but is necessary to obtain optimum combinations of
properties
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8. Alloying with lithium reduces
structural mass by three effects
 Displacement
 Strain hardening
 Precipitation hardening
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9. Displacement
 lithium atom is lighter than an aluminum atom
 Each lithium atom then displaces one aluminum atom from
the crystal lattice while maintaining the lattice structure.
 Every 1% by weight of lithium added to aluminum reduces the
density of the resulting alloy by 3%
 increases the stiffness by 5%. This effect works up to the
solubility limit of lithium in aluminum, which is 4.2%.
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10. Strain hardening
 Introducing another type of atom into the crystal strains the
lattice, which helps block dislocations.
 The resulting material is thus stronger, which allows less of it to
be used
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11. Precipitation hardening
 When properly aged, lithium forms a metastable Al3Li phase (δ')
with a coherent crystal structure.These precipitates strengthen the
metal by impeding dislocation motion during deformation
 The precipitates are not stable however and care must be taken to
prevent overaging with the formation of the stable AlLi (β)
phase. This also produces precipitate free zones (PFZs) typically
at grain boundaries and can reduce the corrosion resistance of the
alloy.
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12. Advantages of Al-Li alloys over
conventional aluminum alloys
 relatively low densities,
 high elastic modulus,
 excellent fatigue and cryogenic strength
 toughness properties,
 superior fatigue crack growth resistance
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13. Application
 Three structures are 2195 and 2090 alloys. AL 2195 is an Al-Li
alloy designed by Lockheed Martin and Reynolds for storage of
cryogenics.
 Al 2090 is a commercially available Al-Li alloy.
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14. components made up of al li alloys
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15. Aerospace
 weight advantage
 Al Li used in a few commercial jetliner airframes,
 fuel and oxidizer tanks in the SpaceX Falcon9 launch
vehicle, AgustaWestland EH101 helicopter
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16. At 2010
 The third and final version of the US Space Shuttle's external tank was principally made
of Al–Li.
 In addition, Al–Li alloys are also used on both the AtlasV and Delta IV EELV rockets,
and before its cancellation were to be used by NASA for Project Constellation, primarily,
on its Ares I and Ares V rockets, as well as the Orion spacecraft
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17. References
 Reference Manual. NASA. September 1988. Retrieved 2014-
01-19.
 http://www.sciencedirect.com/science/article/pii/B97801240
16989000082
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