Crystallization of binary melts and decay of supersaturated solid solutions at the ostwald ripening stage under non-isothermal conditions

Abstract

In this paper a theory on the initial stages of binary melt crystallization and decay of supersaturated solid solutions at the Oswald ripening stage is developed. Examination of the crystallization is performed for systems forming a continuous series of solid solutions and systems which are insoluble in each other when in the solid state. The work consists of two parts. In the first part all the processes are considered for conservative systems. In so doing it is shown that heat fields formed due to evolution of latent heat of crystallization are imposed during the Ostwald ripening of nuclei of the new phase. In the second part, the effects of arrival or removal of matter and heat on processes originating in crystallization of binary melts and decay of supersaturated solid solutions are investigated. An entire set of equations describing the above processes is derived. As a result of an asymptotic solution, the size distribution functions for nuclei of the new phase are obtained. The relationship between changes in the mean radius and density of nuclei as a function of time is found. It is shown that sources (or sinks) of matter and heat are coupled with each other. It is also discussed how heating (or cooling) of a system and also sources (or sinks) of matter influence changes in the size distribution of nuclei of the new phase and their composition. The possibility of controlling the structure of decomposed solid solutions and crystallized binary melts is shown to exist. Our treatment can be used to examine other disperse systems which are at the Ostwald ripening stage.