Numerical model of solid phase transformations governed by nucleation and growth. Microstructure development during isothermal crystallization

TL;DR

This paper introduces a flexible and simple numerical model for simulating solid phase crystallization, capable of handling various nucleation and growth conditions, and validated against analytical models.

Contribution

It presents a novel, easy-to-implement algorithm for modeling grain size distribution during isothermal crystallization with multiple nucleation mechanisms.

Findings

The model accurately predicts grain size distributions.

Universal grain size distribution is observed for certain nucleation regimes.

The Kolmogorov-Johnson-Mehl-Avrami model is validated for different conditions.

Abstract

A simple numerical model which calculates the kinetics of crystallization involving randomly distributed nucleation and isotropic growth is presented. The model can be applied to different thermal histories and no restrictions are imposed on the time and the temperature dependencies of the nucleation and growth rates. We also develop an algorithm which evaluates the corresponding emerging grain size distribution. The algorithm is easy to implement and particularly flexible making it possible to simulate several experimental conditions. Its simplicity and minimal computer requirements allow high accuracy for two- and three-dimensional growth simulations. The algorithm is applied to explore the grain morphology development during isothermal treatments for several nucleation regimes. In particular, thermal nucleation, pre-existing nuclei and the combination of both nucleation mechanisms are analyzed. For the first two cases, the universal grain size distribution is obtained. The high accuracy of the model is stated from its comparison to analytical predictions. Finally, the validity of the Kolmogorov-Johnson-Mehl-Avrami model is verified for all the cases studied.