DIFFUSION-CONTROLLED GRAIN-GROWTH IN PRIMARY CRYSTALLIZATION - AVRAMIEXPONENTS REVISITED

The anomalous behaviour of the Avrami exponents found in the primary c rystallization of amorphous alloys leading to nanostructured materials is considered. A kinetic model able to adequately treat such phase tr ansformation has been formulated by means of the implementation of a s oft-impingement diffusion mechanism after a transient interface contro lled growth. A decrease in the nucleation rate as crystallization proc eeds has also been considered. Comparison of the model with experiment al data is performed, giving excellent agreement. The soft-impingement diffusion mechanism is demonstrated to be responsible for the anomalo us behaviour of the Avrami exponent, the decreasing nucleation rate be ing a second-order effect.