THEORY OF LAYERED-STRUCTURE FORMATION IN PERITECTIC SYSTEMS

Two-phase growth in a peritectic system has been examined, and a theor etical model is developed for the formation of a layered structure in which two phases form alternate layers that are oriented parallel to t he interface. The width of each layer and the spacing between layers h ave been shown to be inversely proportional to velocity, and the propo rtionality constants depend upon the nucleation temperatures for the t wo phases. The nucleation temperatures for the two phases are shown to play a critical role in the formation and stability of layered struct ures. The range of compositions over which layered structures can form is identified, and it is shown that convection effects in the liquid will destabilize the layered structure. Several key experimental studi es have been identified to evaluate minimum undercoolings required for the nucleation of each of the two phases. The morphology of the trans ition interface is shown to depend upon the relative effects of nuclea tion and growth of the two phases.