Microstructure and mechanical properties of a 2091 AlLi alloy—I. Microstructure investigated by SAXS and TEM

The microstructure of the 2091 alloy (AlLiCuMgZr) alloy has been studied and compared to that of two simpler AlLi and AlCuMg alloys. The SAXS, in situ SAXS and TEM techniques have been used for heat treatments at room temperature and at 150°C. The time evolution of the size and of the volume fraction of the δ′ precipitates and of the Cu-rich GPB zones have been determined. The δ′ precipitates are shown to follow a classical Lifschitz-Slyosov-Wagner law. Their interfacial energy has been estimated. S and S′ precipitates have also been characterized, respectively on grain boundaries and on helical dislocations, by TEM.