What are aluminum-lithium alloys and why are they used?

Aluminum-lithium alloys add lithium (1-3%) to aluminum base. Benefits: Reduced density - Each 1% Li reduces density by 3% (up to 10% lighter than conventional Al); Increased stiffness - Each 1% Li increases modulus by 6%; Good fatigue properties - Similar to 2xxx/7xxx; Improved damage tolerance - Better than 7xxx. Alloys: First generation (8090, 2090) had issues with anisotropy, toughness; Third generation (2050, 2195, 2060) overcame most issues. Applications: Wing structures (A380 uses Al-Li), Fuel tanks (Space Shuttle, 2195), Fuselage skins, and Cryogenic applications (good low-temperature properties). Challenges: Higher cost (lithium expensive, processing sensitive), Anisotropic properties (directionality), Requires careful processing (lithium reactive). Third-generation Al-Li alloys increasingly specified for new aircraft (A350, 787) where weight savings justify premium. Processing similar to conventional aluminum with added precautions.