Segregation substructures in dilute Al–Cu alloys directionally solidified

Directional growth of dilute Al–0.2 wt.% Cu alloy was performed under conditions of controlled solidification. Proper metallographic analysis of the segregation patterns behind the solid–liquid (S–L) interface gives information about the effect of the local solidification conditions that determines the microsegregation. In order to explain the apparition of different solidification substructure as a function of the parameter (GL/VC0)(GL/VC0) (GLGL, thermal gradient in the liquid in front of the S–L interface; V  , solidification rate and C0C0, nominal composition of the alloy), as well as the small segregated instabilities detected at the cellular walls, a mechanism based on the morphological stability theory is proposed.