Published online by Cambridge University Press: 15 February 2011
A model is developed that is capable of simulating simultaneous nucleation, growth, and coarsening. Growth and coarsening are simulated with a 2-D Phase Field model and nucleation is simulated by a stochastic algorithm. The actual nucleation events are simulated by placing ordered particles in the matrix, according to the local supersaturation, with the mean rate of introduction matching that of the nucleation rate. The nucleation rates are input parameters that could, for example, be supplied by experiment or atomistic modeling. Isothermal results for this model under conditions approaching constant nucleation show excellent agreement with the Johnson-Mehl- Avrami-Kolmogorov (JMAK) theory of isothermal transformations involving nucleation and growth. Because the Phase Field simulation is interrupted in order to put particles in, problems can arise due to the mismatch of the assumed diffusion field about the nucleating particles and that would be obtained as a result of growth. This can lead to numerical instabilities as the simulation parameters are adjusted to approach the site saturation extreme as well as underestimating the transformation rate by a small transient time. Preliminary step quench results showed the method to be stable enough to simulate non-isothermal transformations with a series of step quench operations.