Phase selection in undercooled peritectic Fe–Mo alloys

Abstract The change of the primary solidification mode of undercooled peritectic Fe–Mo melts has been studied by in situ observation of recalescence events during electromagnetic levitation. A maximum melt undercooling up to 380 K has been achieved. Levitated drops of controlled undercooling were quenched onto chill substrates and subjected to phase and microstructure analysis. A transition from the primary bcc-Mo to the peritectic σ-phase solidification mode beyond a critical undercooling of 345 K was revealed for the Fe47Mo53 alloy and in a similar way for other compositions between Fe45Mo55 and Fe54Mo46. The suppression of the properitectic bcc-Mo phase was also achieved for subcritical undercooling in substrate-quenched Fe45Mo55 samples. In Fe61Mo39 a transition from the primary σ- to the peritectic R-phase solidification mode beyond a critical undercooling of 150 K was inferred from recalescence processes and X-ray investigation of as-quenched undercooled samples.