CHARACTERIZATION OF THE BANDED STRUCTURE IN RAPIDLY SOLIDIFIED AL-CU ALLOYS

Rapid solidification treatments by laser processing have been performed on a series of Al-Cu alloys between 1 and 33 wt.% Cu. For all the alloys, except 1 wt.% Cu, there is a critical growth rate at which the dendritic or eutectic structure is replaced by a banded structure. This latter structure consists of a succession of light (microsegregation-free) and dark (dendritic or eutectic) bands lying approximately parallel to the solid-liquid interface. A phenomenological model which describes the formation of such bands is presented.