OVERVIEW OF GEOMETRIC EFFECTS ON COARSENING OF MUSHY ZONES

An overview is presented of the thermodynamic, kinetic, statistical, a nd geometric factors that govern phase coarsening in dendritic mushy z ones. The coarsening behavior of such systems is best quantified throu gh the kinetics of the decay rate of the specific surface area, S-v. T he geometry of the complex solid-melt interfaces comprising a mushy zo ne is described statistically as an areal distribution of local curvat ure parameters. These parameters capture both the intensive and extens ive thermodynamic characteristics of the mushy zone. The effects of lo cal interface shape, negative mean, and Gaussian curvatures and the ap pearance of inactive lengthscales on the coarsening kinetics of dendri tic structures are discussed. The combined contribution of all these g eometrical effects yields global coarsening rates for ramified mushy z ones that are comparable to those predicted from theory for a collecti on of spherical particles having the identical volume fraction of soli d.