Nucleation and Growth Model of Martensitic Phase Transition

Abstract

A two-dimensional idealized nucleation and growth (2D-ING) model is considered, in order to understand the experimental results relating to martensitic phase trasition. It is an extension of the Kakeshita model for nucleation process (Kakeshita et al.: Mater. Trans., JIM, 34 (1993), 423), based on the nucleation probability derived from a nucleation barrier. We extend the Kakeshita model to an ideal growth process by introducing the concept of a dynamic embryo and a frozen nucleus. A dynamic embryo is a “non-classical” nucleus in the non-equilibrium state. After the size of an embryo is over a critical size, the embryo is transformed into a frozen nucleus. Domains in the low-temperature phase are assumed to develop gathering frozen nuclei. The results of a computer simulation based on the above model show the presence of an incubation time, which is one of the essential properties of the first-order phase transition, and display the cooperative formation of domains and the fractal distribution of their size. The experimental results on the kinetics of the martensitic phase transition in In-Tl alloys have been interpreted in terms of the above simulation results.