Microstructure of ternary eutectic alloys in Bi-Cd-In system

Two ternary eutectic reactions are known to occur in the Bi-Cd-In ternary system: one takes place at 334.6 K and the other at 350,6 K. Experiments were conducted to determine the microstructures that result from these eutectic reactions, as well as the phases present and the volume fraction of each phase. The phases present in the 334.6 K eutectic are the major phase (BiIn₂), Cd solid solution, and an In rich phase which subsequently decomposes eutectoidally. The room temperature In phase is α In. Lamellae of both minor phases are embedded in the major phase with a configuration ABCBA…, similar to that of the Cd-Pb-Sn ternary eutectic. A represents the BiIn₂ phase, B the In rich phase, and C the Cd rich phase. The measured volume fractions are 60%BiIn₂ 4%Cd, and 36% In rich phase. The phases present in the 350.6 K eutectic are BiIn₂, BiIn, and Cd solid solution. The structure, which is not regular, consists of the major phase (BiIn₂) in which are embedded perforated plates of the BiIn phase and thin plates of the Cd phase. The volume fractions of the phases are 64%BiIn₂, 22%BiIn, and 14% Cd solid solution.