Most textbooks on phase diagrams or heterogeneous
equilibria treat only the simplest case, namely the monotectic
E-type decomposition of L0 in the reaction
L0 = L00 + solid1 + solid2 [4,5]. Real alloy examples given
are Pb–Zn–Sn, Pb–Zn–Ag and Ga–Pb–Cd [5] or C–Fe–S
[4] and the special case of an isolated ternary miscibility gap generating this reaction in Cu–Fe–P, Fe–P–Sb and
Fe–Sb–Si systems [4]. The first thermodynamic calculation
of such an isolated ternary immiscibility dates back to the
pioneering work of Meijering [6] for a solution phase where
the excess Gibbs energy of one binary subsystem is much
more negative than in the two other subsystems. In a real
alloy system this case was confirmed by Gro¨bner et al. [7]
for the Al–Mg–Sc system. The particularities of ternary
invariant monotectic reactions were not detailed in these
works.