Document Type

Article

Publication Date

11-15-2018

Publication Title

Journal of Crystal Growth

Abstract

The morphology and distribution of primary dendrites have been examined in Pb-2.2, 5.8 and 10.8 wt. pct. Sb alloy samples directionally solidified (DSed) in ampoules shaped like an hour-glass to examine the influence of cross-section change induced advective flow on the cellular/dendritic interface. This sample design increases the advective flow of the melt towards the array tips, as the liquid-solid interface enters the neck of the ampoule, and then decreases it as the interface exits the neck. The warm solute-rich melt flowing towards the growth front suppresses the extent of side-branching, decreases the primary dendrite spacing, and increases the primary dendrite trunk diameter as observed in the Pb-5.8 and 10.8 Sb alloys. The flow appears to suppress the formation of cells. A cellular interface growing in the Pb-2.2Sb alloy became planar as the solidification front entered the neck, becoming cellular again as it exited the neck.

Comments

This research was supported by grants from NASA-Marshall SpaceFlight Center (Huntsville, AL) and NASA-Glenn Research Center(Cleveland, OH).

Volume

502

DOI

10.1016/j.jcrysgro.2018.09.005

Version

Postprint

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