An Al-5.1%Mg-2.1%Li-0.17%Sc-0.08%Zr (in mass%) alloy designated as 1421 Al was subjected to equal channel angular extrusion (ECAE) with rectangular shape of channels up to fixed true strains of ~4 and ~8 at a temperature of 325oC. This processing provided the formation of uniform recrystallized structures with micron scale average grain size. The 1421 Al after ECAE processing and in initial hot extruded condition was subjected to solution treatment followed by oil quenching and subsequent ageing. Fine grained structure evolved under ECAE remains essentially unchanged under solution treatment. However, this structure affects significantly the precipitation sequence during ageing. Relationships between microstructure and service mechanical properties are considered.