Bubbles engulfment and entrapment by cellular and dendritic interfaces during directional solidification

The purpose of this work was to investigate bubbles engulfment and entrapment by cellular and dendritic interfaces during directional solidification. The experiments were performed in succinonitrile-based transparent alloys (SCN-1.5 wt%ACE). While the solid–liquid interface is cellular, the solid–liquid interface is separated into two layers by the bubble. Experimental results show that a cellular–planar–cellular transition for solid–liquid interface occurs on the lower layer and the stability of the tubular bubble is determined by local microstructure on the upper layer. When the interface is dendritic, morphological instability occurs on the solid thin film attached to the bubble after the solid–liquid interface hits the bubble. We analyzed the evolution of such cells (some cells become dendrites with time) as a function of the angle between the opposite growth direction of dendritic array and the small cell growth direction. It is demonstrated that the relative position between the existing bubble and the dendritic tip influences on the local growth pattern of dendritic array.

► We investigated bubbles engulfment and entrapment by cellular and dendritic interfaces in solidification.
► The stability of the tubular bubble is determined by local microstructure.
► We studied the morphological instability occurs on the solid film enveloping the bubble.
► The changes of the dendritic array depend on the size of the bubble and the relative position of the bubble.
► Microstructure of the solid–liquid interface determines the final shape of the bubble.