Rapid solidification behaviour of undercooled levitated Fe-Ge alloy droplets

Abstract

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 240 K. Growth velocity of α- (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 α- and ε-phase (DO₁₉). 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.