Equalization of Primary Dendrite Arm Spacing during Growth of Columnar Dendrite

Abstract

  In this study, the mechanism of equalization for λ₁ has been investigated using succinonitrile-1.0 mass% water alloy. Approximately 15 columnar dendrites have been observed and the maximum and the minimum value of λ₁ (λ₁^Max and λ₁^Min, respectively) have been characterized. It is found that λ₁^Max decreased and λ₁^Min increased with time, i.e., the tip of primary arm grow to the region of wide from region of narrow of dendrite arm spacing. And also, Local primary arm spacings are gradually equalized due to propagation of position of primary trunk. The time necessary for the equalization for λ₁ is found to be longer than that of the process for adjusting dendrite tip radius and the change in λ₁ due to branching or over growth. This may suggest that solutal filed in the interdendritic region plays and important role for equalization for λ₁.