Solid state phase transformation kinetics: a modular transformation model

A modular model for the kinetics of solid state phase transformations has been discussed, recognising three mechanisms: nucleation, growth, and impingement of growing new phase particles. For each of the three constituting mechanisms, several model descriptions can be incorporated. The choice for one specific (mathematical) description is based on microstructural information, thermodynamic data and available knowledge of the kinetics about the phase transformation concerned. The model is valid for both isothermally as well as non-isothermally conducted transformations. The model kinetic parameters are independent of the time-temperature program. In certain specific cases, the model can be simplified such that it reduces to so-called Johnson-Mehl-Avrami kinetics. From the kinetic model a method resulted to obtain the activation energies for nucleation and growth separately. The model has been applied successfully to a number of diverse transformations, involving the crystallisation of Pd40Cu30P20Ni10, the crystallisation of amorphous Mg-Cu and the austinite-ferrite transformation in Fe-Mn alloys.