Forming mechanism of metastable “dendrite core” in undercooled Fe–Ni alloy

In order to investigate forming mechanism of the metastable “dendrite core” in undercooled Fe–7.5 at.%Ni alloy melt, alloy samples subjected to undercoolings above the critical value for metastable phase formation were quenched and heat-treated. It was evidenced that solid-state transformation, i.e. from metastable δ phase to stable γ phase, cannot be completed during solidification, thus the remained δ phase forms the so-called metastable “dendrite core”. Meanwhile the solidification behavior during the second recalescence was described applying peritectic reaction theory.