Al-Li alloys are a series of alloys of aluminium and lithium, often also including copper and zirconium. Since lithium is the least dense elemental metal, these alloys are significantly less dense than aluminium. Commercial Al-Li alloys contain up to 2.45 wt% lithium. Alloying with lithium reduces structural mass by two effects: Displacement- a lithium atom is lighter than an aluminium atom; each lithium atom then displaces one aluminium atom from the crystal lattice, while maintaining the latti… (More on Al-li)