After alloying, the composition of the
master alloy was measured using inductively coupled
plasma atomic emission spectrometry (ICP-AES) and
the mean composition was determined as Fe–4.35 at.%
Ni. The samples, each weighing 5 g, were undercooled
using glass fluxing. After solidification, the samples were
rapidly quenched into a Ga–In–Sn bath to suppress
solid-state solute diffusion. The detailed procedure is
described elsewhere [26]. The thermal behavior of the
sample was monitored by a two-color pyrometer with
a relative accuracy of ±3 K and a response time of
5 ms. In order to investigate the phase transformation
after solidification, isothermal annealing for 30 min at
1623 K (i.e. in the c single-phase area of the phase diagram)
was performed on the sample. After annealing,
the sample was rapidly water-quenched to avoid the
eutectoid reaction c ! a-Fe + FeNi3 [23].