The effect of Be addition on the precipitation behaviors and the morphological variations in Al-Li alloys

Al-Li-(Be) alloys and Al-Li-Cu-Zr-(Be) alloys have been prepared by an ingot metallurgy. The effects of the beryllium addition on the precipitation behaviors and microstructural changes in Al-Li alloys, which have lower toughness and ductility than conventional high-strength aluminium alloys, have been investigated by means of a differential scanning calorimetry and a transmission electron microscopy. The results showed that (1) in Al-Li binary alloy the formation of δ double-prime phase and the precipitation and dissolution of δ ' or δ phase were accelerated by beryllium addition and the coarsening rate of δ' phase was also increased when aged at 463K, and (2) in Al-Li-Cu-Zr(2090) alloy the precipitation of δ double-prime (G.P.II zone), θ', and T1 phases was accelerated by minor beryllium addition and the precipitation of θ double-prime and θ' phases which have been known as an effective barrier to the planar slip was also increased when aged at 463K for 24hours