Microstructure of severely deformed Al–3Mg and its evolution during annealing Original Research Article

The submicron microstructure developed here after heavy deformation of Al–3Mg by equal channel angular pressing (ECAP) is shown to consist of an elongated grain and cell structure of width 70–80nm and 300–400nm length. There is also a high dislocation density inside these grains with some tendency to dislocation arrangement as a cell structure. Many of the grain boundaries are shown to be of low–medium angle and are not the randomly misoriented, high-angle boundaries generally assumed to be present. Annealing at low temperatures leads to a reduction of dislocation density, some reduction of grain length as transverse boundaries form in the elongated grains, and grain coarsening. At higher temperatures a duplex structure forms as some regions show localized recrystallization. The relationship of grain boundary misorientation and high-temperature coarsening and recrystallization to the applied heavy strain and alloy composition is discussed.