Kinetics of Quenches.

Order-disorder transitions have been studied for many years. The great number of experiments done on binary alloys makes condensed matter physics very appealing since it allows theory and experiment to progress side by side. Using field theoretic methods, we study many aspects of physical systems such as binary alloys, which are taken out of thermodynamic equilibrium. In the introduction, an expose of basic notions is given. In the second chapter, we review an analytical method describing phase separation processes resulting from a critical quench. Physically, the latter phenomena could represent an initially disordered binary alloy, in which, following a drop in temperature, the atoms spontaneously order into a crystalline lattice. We will then study the effect a conserved field has on the kinetics of phase separation. This conserved field represents the local concentration of atoms of the alloy. In Chapter 4, we describe a theory formulated to explain some non -trivial relaxation of the structure factor seen experimentally for an initially ordered system suddenly cooled. Finally, we propose a theoretical model describing polymorphous crystallization. The model is studied via computer simulations. The results so obtained are compared to the experiment.