Dendritic Segregation of Zn-Al Eutectoid Alloys

The structural investigations performed and described in this paper are focused on both the segregation phenomenon at the dendrite level, and on the external structure in the equilibrium state. Qualitative and quantitative investigations of the Zn-Al eutectoid alloy (22% Al) structures in equilibrium and non-equilibrium states were considered and studied, revealing that, in this composition, dendritic segregation determines the eutectic transformation. Solidification in non-equilibrium conditions controls both the eutectic transformation and the significant variation of the chemical composition within the dendritic unit, as well as in other constituents. The most important effect of dendritic segregation is on the ratio of the different phases and on their geometry and distribution within the metallic matrix, which determines the material topology. The phenomena involved in such conditions are governed by the structural transformations, which take place during solidification and cooling in a solid state.