Rapid solidification behaviour of undercooled levitated Fe-Ge alloy droplets

The solidification behaviour of Fe82Ge18 and Fe75Ge25 alloys is studied by using an electromagnetic levitation facility. The maximum undercooling attained in the case of Fe82Ge18 alloy is 240K. Growth velocity of alpha-(bcc) phase is measured using a photodiode technique and shows two distinct regimes. In the case of Fe75Ge25, the maximum undercooling attained is 165 K. At low undercoolings two recalescence events occur, corresponding to formation of alpha- and epsilon-phase (DO19). At large undercoolings the peritectic reaction (alpha + liquid --> epsilon) is suppressed. Microstructural analysis indicates morphological changes in the microstructure as well as a competition among phases nucleating at different levels of undercooling. (C) 2003 Elsevier B.V. All rights reserved.