DROPLET FLUCTUATIONS IN THE MORPHOLOGY AND KINETICS OF MARTENSITES

We present a mode-coupling theory which describes the morphology and k inetics of the nucleation of twinned martensite droplets within a pare nt crystal. This involves a ''slow'' vacancy field that Lives at the p arent-product interface. Our theory suggests that a slow quench from t he parent phase produces an equilibrium product, while a fast quench p roduces a metastable martensite. In two dimensions, the martensite nuc lei grow as strips having alternating twin domains, with well-defined front velocities. Several empirically known structural and kinetic rel ations drop out naturally from our theory.