Cell/dendrite distribution in directionally solidified hypoeutectic Pb-Sb alloys

Abstract

The alloys Pb-2.2 wt pct Sb and Pb-5.8 wt pct Sb were directionally solidified with three different thermal gradients of 40, 86, and 140 K cm⁻¹ at growth rates ranging from 0.6 to 30 µm s⁻¹. A Gaussian peak amplitude analysis of the cell/dendrite spacing distribution shows a distinct peak corresponding to the nearest neighbors. The peaks corresponding to the second and the third nearest neighbor spacings are also brought out by this technique. The ratios of the second to the first nearest neighbor spacings and that of the third to the first neighbor spacings are 1.85 ± 0.11 and 2.70 ± 0.25, respectively. This indicates that the cells and dendrites both have a hexagonal distribution with a significant amount of superimposed noise. This is also confirmed by the frequency distribution of their number of nearest neighbors (coordination number).