Rapid solidification behaviour of undercooled levitated Fe-Ge alloy droplets

摘要

The solidification behaviour of Fe_(82)Ge_(18) and Fe_(75)Ge_(25) alloys is studied by using an electromagnetic levitation facility. The maximum undercooling attained in the case of Fe_(82)Ge_(18) alloy is 240 K. Growth velocity of α- (bcc) phase is measured using a photodiode technique and shows two distinct regimes. In the case of Fe_(75)Ge_(25), the maximum undercooling attained is 165 K. At low undercoolings two recalescence events occur, corresponding to formation of α- and ε-phase (DO_(19)). At large undercoolings the peritectic reaction (α + liquid → ε) is suppressed. Microstructural analysis indicates morphological changes in the microstructure as well as a competition among phases nucleating at different levels of undercooling.