Microstructures formed by directional solidification of two ternary eutectic alloys of Bi-Cd-In system

摘要

Microstructures of the two ternary eutectic alloys of the Bi - Cd - In system were studied using slow unidirectional solidification, followed by quenching to form a representative solid/liquid interface for subsequent observation. The eutectic reactions were found to take the form L?BiIn + BiIn_2 + Cd at 77.5 deg C and L?BiIn_2 + #epsilon# + Cd at 61.5 deg C. The 77.50C eutectic was observed to be of the faceted (BiIn) - faceted (Cd) - non-faceted (BiIn_2) type, while all three phases of the 61.50C eutectic showed faceting. The Bun and BiIn_2 phases of the 77.50C eutectic formed a quasiregular microstructure with the Cd phase growing relatively independently. The phases of the 61.50C eutectic tended to form a lamellar microstructure with a BiIn2 - #epsilon# - Cd - #epsilon# - BiIn_2 phase sequence. Both eutectics were observed to obey the usual phase spacing law, #lambda#~2R = constant, where A is the phase spacing and #lambda# is the growth rate.