Additivity and isokinetic behaviour in relation to diffusion controlled growth

Additivity and isokinetic behaviour in relation to transformations that involve coupled nucleation and growth have been examined. As a starting point, a numerical solution is presented which takes into account the independent variations of the nucleation and growth rate with temperature and matrix solute content. This solution is later used to check the validity of two analytical models, based on the internal state variable approach and the Avrami equation, respectively. It is concluded that the analytical solutions provide an approximate but adequate description of the overall transformation behaviour during continuous cooling. The latter is particularly true if the evolution equations are calibrated against experimental microstructure data, as frequently done in high-hierarchy models for process simulation.