MICROSTRUCTURE OF BI-CD-PB TERNARY EUTECTIC

Specimens of the Bi-Cd-Pb ternary eutectic were solidified unidirectio nally at very low speeds and quenched to form a representative solid/l iquid interface for subsequent study. This eutectic was found to be of the Bi(faceted)-Cd(faceted)-Pb2Bi(non-faceted) type. A 'double binary ' microstructure was formed on freezing, consisting of binary quasireg ular regions composed of Bi and Pb2Bi and binary regions of broken lam ellar Cd-Pb2Bi microstructure. Comparison with systems studied previou sly suggests that a faceted-faceted-non-faceted ternary eutectic of pr imarily lamellar form will tend to assume a double binary microstructu re on freezing, the non-faceted phase will be common to the two binary structures, and each binary structure will take the form correspondin g to that expected for a binary eutectic of similar volume fraction of faceting phase. (C) 1996 The Institute of Materials.