Kinetics of the peritectic phase transformation: In-situ measurements and phase field modeling |
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Authors: | Dominic Phelan Mark Reid Rian Dippenaar |
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Affiliation: | (1) the Faculty of Engineering, BHP Steel Institute, University of Wollongong, NSW, Australia |
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Abstract: | An experimental study has been conducted into the role of cooling rate on the kinetics of the peritectic phase transformation
in a Fe-C alloy. The interfacial growth velocities of the peritectic phase transformation were measured in situ for cooling rates of 100, 50, and 10 K/min. In-situ observations were obtained using high-temperature laser scanning confocal microscopy (HTLSCM) in a concentric solidification
configuration. The experimentally measured interface velocities of the liquid/austenite (L/γ) and austenite/delta-ferrite
(γ/δ) interphase boundaries were observed to increase with higher cooling rates. A unique finding of this study was that as
the cooling rate increased, there was a transition point where the L/γ interface propagated at a higher velocity than the
γ/δ interface, contrary to the findings of previous researchers. Phase field modeling was conducted using a commercial multicomponent,
multiphase package. Good correlation was obtained between model predictions and experimental observations in absolute values
of interface velocities and the effect of cooling rate. Analysis of the simulated microsegregation in front of the L/γ and
γ/δ interfaces as a function of cooling rate revealed the importance of solute pileup. This microsegregation plays a pivotal
role in the propagation of interfaces; thus, earlier modeling work in which complete diffusion in the liquid phase was assumed
cannot fully describe the rate of propagation of the L/γ and δ/γ interfaces during the course of the peritectic transformation. |
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