Cellular breakdown of the planar interface in unidirectional solidification of Al- Cu alloy

The preferred grain boundary segregation occurred prior to the breakdown of the planar interface. Small holes appeared at random on the solidliquid interface at the beginning of the transition. The holes were aligned or distributed regularly to form an elongated cell. The solidification proceeded, entrapping the liquid phase at the bottom of the holes and resulted in the '%'rosary- like segregation'%'. The '%'rosarylike segregation'%' was also observed in hexagonal cell nodes.