Additivity and isokinetic behaviour in relation to diffusion controlled growth

Additivity and isokinetic behaviour in relation to transformations that inv olve coupled nucleation and growth have been examined. As a starring point, a numerical solution is presented which takes into account the independent variations of the nucleation and growth rate with temperature and matrix s olute content. This solution is later used to check the validity of two ana lytical models, based on the internal state variable approach and the Avram i equation, respectively. II is concluded that the analytical solutions pro vide 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 dat a, as frequently done in high-hierarchy models for process simulation. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights r eserved.