Phase-field simulation of nucleation and growth of M23C6 carbide and ferromagnetic phases during creep deformation in Type 304 steel

A phase-field method was applied to the simulation of simultaneous nucleation and growth of both M23C6 carbide and ferromagnetic α phases during the creep process in Type 304 steel. Nucleation events of these product phases were explicitly introduced through a probabilistic Poisson seeding process based on local nucleation rates that were calculated as a function of local concentration. The defect energy of the creep dislocations near the carbides, which increases during creep, was integrated into the nucleation driving force for the α phase. The simulation used in this study accurately reproduced changes in the amounts of the precipitated phases as a function of creep time. Furthermore, we examine the effect of the dislocation density on precipitation of the α phase, and show that the phase-field method is useful for examining the stochastic and kinetic phenomenon of phase transformation.