TRANSFORMATION KINETIC-EQUATIONS FOR THE STUDY OF NONEQUILIBRIUM PRIMARY CRYSTALLIZATION

An important tool in the study of non-equilibrium crystallization proc esses is the use of the Johnson-Mehl-Avrami-Kolmogorov theory, recentl y re-derived by Cahn, which is intended to apply when homogeneous nucl eation 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 hom ogeneous nucleation. Growth in the initial steps is assumed to occur a t a constant rate while it becomes diffusion limited as crystallizatio n proceeds. Examples of application to calorimetric kinetic data of pr imary crystallization for Fe76Nd16B6, Fe73.5Cu1Nb3Si13.5B9 and Al87Ni7 Nd3Cu3 amorphous alloys under isothermal treatment are given.