HETEROGENEOUS NUCLEATION OF PB PARTICLES EMBEDDED IN A ZN MATRIX

Zinc-10 and 20 wt pct Pb alloys have been rapidly solidified by melt spinning to obtain a very fine scale dispersion of nanometer-sized Pb particles embedded in Zn matrix. The microstructure and crystallography of the Pb particles have been studied using transmission electron microscopy (TEM). Each embedded Pb particle is a single crystal, with a truncated hexagonal biprism shape with the 6/mmm Zn matrix point group symmetry surrounded by {0001}, {1010BAR}, and {1011BAR} facets. The Pb particles solidify with a well-defined orientation relationship with the Zn matrix of (0001)Zn parallel-to (111)Pb and [1120BAR]Zn parallel-to [110BAR]Pb. The melting and solidification behavior of the Pb particle have been studied using differential scanning calorimetry (DSC). The Pb particles solidify with an undercooling of approximately 30 K, by heterogeneous nucleation on the {0001} facets of the surrounding Zn matrix, with an apparent contact angle of 23 deg.