Editors : P. D. Bristowe, D. E. Fowler, A. D. Romig
a1 Metallurgy Division, National Institute of Standards and Technology Gaithersburg, Maryland 20899
The morphology of directionally solidified CuAl-Pb monotectic alloys has been studied. The structure consisted of a hexagonal array of Pb rods in a Cu-based matrix. In addition, elongated grain boundaries in the Cu-based matrix with lens-shaped Pb fibers on the boundary and a “denuded zone”, depleted of Pb rods, were observed. Existence of these boundaries is shown to reduce the overall surface energy of the system leading to the formation of the elongated grain boundaries.