Gumennyk K. Phenomenological theory of ordering and segregation processes in antiphase domains of solid substitution solutions

The thesis is devoted to investigation of polydomain ordering in two-componenet substitutional solid solutions with fcc and bcc lattices. Analitical expressions are obtained, describing temporal evolution of the specific volume and average thickness of antiphase boundaries in a rapidly cooled fcc alloy of the AuCu3 type. It is shown that the too small (nanoscale) size of a sample may cause preserving of the disordered phase in its interior even at temperatures lower than the spinodal. The latter result is verified by the available electron microscope observations. A phenomenological model is developed for description of the simultaneous progress of ordering and diffusion processes in binary bcc alloys of an arbitrary composition. It is established that under a disorder- order transformation, at first for "microscopic" times occurs formation of an ordered polydomain structure, which is then followed by a much more slower process of segregation of the major alloy component in the regions of antiphase boundaries.