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 1
- 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 1/26/2017 2
- 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. 1/26/2017 3
- 4. Composition of aluminum-lithium alloys (wt. %) 1/26/2017 4 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 1/26/2017 5 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 1/26/2017 6
- 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 1/26/2017 7
- 8. Alloying with lithium reduces structural mass by three effects Displacement Strain hardening Precipitation hardening 1/26/2017 8
- 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%. 1/26/2017 9
- 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 1/26/2017 10
- 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. 1/26/2017 11
- 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 1/26/2017 12
- 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. 1/26/2017 13
- 14. components made up of al li alloys 1/26/2017 14
- 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 1/26/2017 15
- 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 1/26/2017 16
- 17. References Reference Manual. NASA. September 1988. Retrieved 2014- 01-19. http://www.sciencedirect.com/science/article/pii/B97801240 16989000082 1/26/2017 17