Solidification of undercooled peritectic Fe-Ge alloy

Bulk samples of Fe-25 at.% Ge peritectic alloy are undercooled up to 260 K using electromagnetic levitation technique. The growth rate of the primary phase is measured using a capacitance proximity sensor technique. Solidification microstructure is studied as a function of undercooling. The microstructure of samples at low undercoolings consists of a residual primary phase (alpha)2, peritectic phase (epsilon) and inter-dendritic (epsilon)-(beta) eutectic. Microstructure at higher undercoolings is nearly phase-pure (epsilon). Time resolved diffraction analysis of the levitated droplets using synchrotron radiation indicates the nucleation of primary (alpha)2 in all cases. The growth rate is analysed using current theories to explain the experimental observations. Interfacial undercooling is found to play an important role in the growth kinetics. Our results also suggest suppression of peritectic reaction.