Effects of melt flow on the primary dendrite spacing of Pb-Sn binary alloy during directional solidification

The influences of melt flow generated by traveling magnetic fields (TMFs) on dendrite growth during the upward-directional solidification of Pb-33 wt% Sn binary alloy were investigated under the condition of 1 x g gravity. When the direction of the TMF was changed from upward to downward, the primary dendrite spacing gradually increased, and the peak of distribution of the primary dendrite spacing shifted to the narrower values. This was caused by the different intensities of melt flow, which was controlled by TMFs. The effects of TMFs on melt flow were similar to those of adjustments in gravity levels; thus, the primary dendrite spacing varied. The effective gravity acceleration, which was used to modulate melt flow, decreased for downward-TMFs and increased for upward-TMFs. As the drawing speed increased, the modulated flow showed more significant influences on primary dendrites spacing. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.