Droplet fluctuations in the morphology and kinetics of martensites

Abstract

We derive a coarse grained, free-energy functional which describes droplet configurations arising on nucleation of a product crystal within a parent. This involves a new 'slow' vacancy mode that lives at the parent-product interface. A mode-coupling theory suggests that a slow quench from the parent phase produces an equilibrium product, while a fast quench produces a metastable martensite. In two dimensions, the martensite nuclei grow as 'lens-shaped' strips having alternating twin domains, with well-defined front velocities. Several empirically known structural and kinetic relations drop out naturally from our theory.