Transformation kinetic equations for the study of non-equilibrium primary crystallization

An important tool in the study of non-equilibrium crystallization processes is the use of the Johnson-Mehl-Avrami-Kolmogorov theory, recently re-derived by Cahn, which is intended to apply when homogeneous nucleation and crystal growth control the transformation. In this paper an attempt is presented to apply this theory to primary crystallization processes when nuclei are mostly either pre-quenched or created by homogeneous nucleation. Growth in the initial steps is assumed to occur at a constant rate while it becomes diffusion limited as crystallization proceeds. Examples of application to calorimetric kinetic data of primary crystallization for Fe76Nd16B8, Fe73.5Cu1Nb3Si13.5B9 and Al87Ni7Nd3Cu3 amorphous alloys under isothermal treatment are given.