Contribution to the study of mechanisms involved in the formation of rheocast structure

The work presents some results obtained when producing rheocast structures of Al–(4.5wt.%)Cu alloys, by heat treatment of dendritic material (in as-cast and cold deformed conditions) at temperature above solidus. Macro and microstructures were analysed in order to investigate the evolution mechanisms involved in the structure modifications. Results show that coarsening and coalescence phenomena can lead to a significant difference between the sizes of grain and globule, therefore being necessary to distinguish between micro and macroconstituents. Results also show that, for deformed dendritic structure, a phenomenon of recrystallisation plus boundaries wetting leads to structures where one globule of the primary phase corresponds to one grain in the macrostructure.