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, thermal gradient in the liquid in front of the S-L interface; V, solidification rate and C0, 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.