Disruption of an Aligned Dendritic Network by Bubbles During Re-melting in a Microgravity Environment

摘要

The Pore Formation and Mobility Investigation (PFMI) utilized quartz tubes containing succinon-itrile and 0.24 wt% water "alloys" for directional solidification (DS) experiments which were conducted in the microgravity environment aboard the International Space Station (ISS; 2002-2006). The sample mixture was initially melted back under controlled conditions in order to establish an equilibrium solid-liquid interface. During this procedure thermocapillary convection initiated when the directional melting exposed a previously trapped bubble. The induced fluid flow was capable of detaching and redistributing large arrays of aligned dendrite branches. In other cases, rapidly translating bubbles originating in the mushy zone dislodged dendrite fragments from the interface. The detrimental consequence of randomly oriented dendrite arms at the equilibrium interface upon reinitiating controlled solidification is discussed.