Directional solidification methods have been used to examine the growth of fibrous, or tubular, composite samples in alloys close to the monotectic reaction: Liquid 1 Solid + Liquid 2. The binary systems Al-In, Cu-Pb and Cd-Ga have been examined and some use made of a transparent analogue, succinnonitrile-water. The solidification behavior appears to relate to the height of the miscibility gap in such systems and it is demonstrated how ternary additions which change this height (Sn to Al-In, Al to Cu-Pb) modify the microstructures dramatically. These structural changes are discussed with reference to the relative surface energies between two immiscible liquids and a third (solid) phase. The phase spacings and transitions in microstructure are discussed in terms of diffusion processes at the monotectic front.

Alloy solidification in systems containing a liquid miscibility gap

Casting alloys of eutectic composition are of great practical importance. Good microstructural control of these alloys is essential in obtaining the required properties in the cast state. P...

Dendrite growth in eutectic alloys: the coupled zone

Chemistry of eutectic and monotectic; phenanthrene-succinonitrile system

Terminal solid solubility limits in the AlAg2Al eutectic system

Molten specimens of Cd-Zn eutectic alloy (26.50 at.% Zn) were undercooled by the glass-slag technique using glass-forming ZnCl2 as the slag. The microstructure of the solidified samples, weighing about 20 g each, was found to be a function of the undercooling produced. At lower undercoolings the microstructure consisted of supersaturated primary cadmium dendrites co-existing with the eutectic, while at higher coolings duplex structures were observed. Possible causes for the differences in microstructure are discussed with due importance given to the recorded recalescence effects.

G.R Armstrong

Papers

Composition and volume fraction changes in Ag-Al eutectic alloys