Nucleation of recrystallization: A new approach to consider the evolution of the substructure in the system

The mechanisms of nucleation during dynamic and static recrystallization still remain unclear, particularly with respect to their precise formulation into equations, and the specific implications of subgrains features on these mechanisms. In this paper, it is proposed to correlate the grain nucleation with subgrains and low-angle boundaries misorientation evolution. A nucleation criterion that takes into account the low-angle boundary density evolution in the system is established based on thermodynamic considerations. This new approach is based on a reformulation of the Bailey-Hirsch criterion and is derived from calculations of the equilibrium pressure on grain boundaries. The free energy calculations associated with this criterion allow a fine phenomenological description of the associated nucleation frequency. This new approach is tested in the case of recrystallization of a ferritic stainless steel grade during hot compression tests. The evolution of the substructure is then studied for different holding times up to 20 s after hot compression. It appears that the nucleation frequency based on the proposed nucleation criterion is in agreement with the nucleation frequency derived from experimental observations. This approach allows a better understanding of the mechanisms governing the ability of a subgrain to nucleate in a given system, using rather simple assumptions.