AbstractSpecimens of the Bi–Cd–Sn ternary eutectic were solidified under closely controlled conditions and quenched during freezing to form a‘quenched interface’for subsequent observation. Very low growth rates, from 8 nm s−1to 1·1μm s−1, were used to produce a microstructure sufficiently coarse to show considerable detail at the quenched interface and thus reveal distinctly the mode of solidification of the alloy. The three phases formed on solidification of this eutectic alloy are Bi, Cd, and a–;βCd–Sn’phase derived from the hexagonal Sn rich phase of the Cd–Sn binary system. It was observed that the Bi and Cd phases both freeze in a faceted manner whereas theβCd–Sn phase is non-faceted. Under the growth conditions used, this eutectic showed a marked tendency to form regions of binary microstructure. At the higher growth rates examined, regions of Bi–βCd–Sn quasiregular binary microstructure, outlined by Cd flakes, were formed, whereas at the lower growth rates the Cd andβCd–Sn phases formed a nearly regular lamellar microstructure containing relatively large inclusions of Bi. It was observed that the Cd–Cd phase spacing varies only slowly, whereas the Bi–Bi phase spacing varies much more rapidly with growth rate in theβCd–Sn matrix phase. This variation is attributed to the different branching tendencies of the Bi and Cd phases and appears to account for the formation of regions of binary microstructure.MST/1551