Ternary eutectic growth in microgravity environment

Rapid growth of Ag38.5Cu33.4Ge28.1 ternary eutectic alloy was accomplished in a 3m drop tube and its phase selection and growth mechanism were investi gated. The experimental results revealed that the semiconductor phase (Ge) was the primary nucleating phase during solidification, which agrees with t he calculated results of nucleation rate. The solid solution phase (Ag) and intermetallic compound phase eta(Cu-5 Ge-2) grew cooperatively and lamella r structures similar to binary eutectic formed. Moreover, with the decreasi ng of droplet size, the growth morphology of primary (Ge) phase transformed from plate-like to granular shape and a kind of anomalous ternary eutectic formed. The microgravity environment has a significant effect on the cryst al growth process, which makes the (Ge) phase distribute homogeneously and the anomalous eutectic grains show good geometrical symmetry. The calculati on of cooling rate versus droplet diameter showed that it was the: high coo ling rate and large undercooling that brought about the eutectic growth mor phology transition.