This thesis describes a study of the fundamental aspects of banding in steel. The banded structure is simulated by means of layer diffusion couples. Consideration is given to the amount of carbon pre-­segregation that occurs in the austenitic state due to activity differ­ences arising from a non-uniform distribution of alloying elements as well as to the segregation which occurs during subsequent transformation. A new method for the experimental determination of the off-diagonal diffusion coefficients which control the pre-segregation in ternary systems is described. Different cooling rates are used to investigate the contribution of transformation segregation toward the final structure. The effect of cooling rates on the final structure is investigated metallographically. / Thesis / Master of Science (MS)