Structure and diffuseness model of solid-liquid interface for binary alloys

•Evaluation of the size and the number of atomic layers at the solid–liquid interface for a fixed solidification velocity using the maximum entropy production rate (MEPR) principle.•The formation of cellular faceted and non-faceted cellular morphologies from a planar front is because of entropy generation and maximization rate principle.•Discussion on the formation of cellular faceted and non-cellular faceted from a planar interface through a unification of Cahn interface diffuseness theory and Jackson diffuseness model, as a function of the solidification velocity and temperature gradient.•The model sheds light on the structure of the solid–liquid interface and addresses its implications on the formation of faceted and non-faceted cellular morphologies in binary alloys. Using the morphological instability at the solid–liquid interface as a basis by the maximum entropy production rate principle (MEPR), a model is presented on the morphological structure and diffuseness of the interface during directional solidification of binary alloys. It is shown that, the independent diffuseness theory of Cahn and the Jackson roughness criterion can be unified at a limiting condition under this new MEPR solidification model. The model under the principle of MEPR is applied to describe the evolution of atomistically smooth and rough interfaces through the evaluation of the size of the solid–liquid interface and the of number atomic layers. The model is tested with data for binary alloys of aluminium, lead, and tin at varying solute concentrations. The results showed strong agreement with available data from experimental measurements.