Relation between the deformation sub-structure after rolling or tension and the recrystallization mechanisms of an IF steel

The characteristics of the deformation microstructure of an IF steel sample have been studied using TEM after 40% cold rolling and 35% strain in tension. Different microstructures can be distinguished: lamellar bands for the {1 1 1} 〈1 1 2〉 grains belonging to the γ fibre and equiaxed cells for the {1 1 1} 〈1 1 0〉 grains that belong to both γ and α fibres as well as the {0 0 1} 〈1 1 0〉 grains that belong exclusively to the α fibre. Whatever the initial dislocation structure, the first steps of nucleus formation are characterized by coalescence and growth of deformation cells. The first steps of recrystallization mainly take place via continuous growth of subgrains for both orientations and are followed by bulging of grain boundaries in the case of the {1 1 1} 〈1 1 0〉 subgrains. The role of the morphology and size of the subgrains as well as that of the deformation energy stored by the sub-boundaries are discussed within the framework of the nucleation processes of low carbon steels.