From the cooling curve for pure liquid metals with high
Tm, the supercooling of liquid state, T, was evaluated by the
relation, T ¼ Tr TC, where Tr is the constant temperature
after the recalescence, namely Tm, and TC the temperature of
supercooling limit of liquid phase. Together with literature
values,7,8) the obtained T was summarized in Table 1. The
typical examples of cooling curve for liquid Ni-Nb system
are shown in Fig. 2. Figure 2(c) indicates that after the
recalescence a constant temperature was able to be observed
for the sample of Ni-71 at% Nb. This is derived from the
fact that on the recalescence the homogeneous liquid of
Ni-71 at% Nb in the supercooled state changed into the
coexisting state of three phases, liquid, intermetallic compound
(Ni6Nb7) and solid Nb.20) Gibbs phase rule2) allows
only the unique temperature, 1563 K, under atmosphere
pressure for this coexisting state of three-phases. Similarly,
as can be seen in Fig. 2(b), the supercooling of homogeneous
liquid phase for the eutectic composition (Ni-40.5 at% Nb)
provided the eutectic temperature (1448 K) as the constant
temperature after the recalescence, which is also derived
from the coexistence of three phases, two solid phases, and
liquid phase (Gibbs phase rule2)). On the other hand, as can
be seen in Fig. 2(a), the cooling curve of Ni-35 at%Nb