Effect of Sub-Structure and Precipitation Behavior on Mechanical Properties of Al–xCu–Li Alloys

The tensile properties and microstructure of extruded and cold rolled 2A55 Al–Li alloys with different Cu content were studied. After solution treatment, the strength of extruded sheets is slightly higher than that of cold rolled sheets due to strong deformation texture and high density of substructure. However, the strength change order is different with the increase of Cu content with T6-24 h. The extruded sample with higher Cu content have higher strength due to many dense T1 precipitates. The δ′/θ′/δ′ composite precipitates and θ′ precipitates suppress the formation of T1 precipitates, which cause cold rolled sample with higher Cu content shows lower strength. Additionally, many fine T1 precipitates nucleate at the sub-grain boundaries formed in the extrusion process, which have a significant effect on the mechanical property.