This thesis describes a Master of science research program of duration May, I960 to April, 1961 inclusive. It represents part of an extensive research program designed to investigate the thermodynamic aspects of phase transformations. A great deal of effort has been devoted to the application of multicomponent diffusion theory to (de)carburisation, pearlite, and segregation reactions; particularly in ferrous alloys. This fundamental research program is here extended to a general study of the morphological aspects of phase transformation interfaces. Substantially all industrial metallurgical phase transformations are accompanied by the development of non-planar morphologies with attendant segregation. Previous investigations have demonstrated that the factors controlling the type and degree of morphological development are varied and complex. It is apparent that the structural character of an interface is determined, to a large extent, by the system’s phasial constitution in terms of the concentration, temperature, and pressure variables. Therefore, an examination of the relation between these parameters and the structural form of non-planar interfaces was suggested as a potentially valuable field of endeavour. / Thesis / Master of Science (MSc)