Eutectic, Eutectic Temperature
Index
The phase diagram between lead and tin shows the eutectic invariant reaction between these two constituents. At the eutectic temperature of 183 C, three phases exist in equilibrium: (Pb) with the composition Pb-19 wt % Sn, (Sn) with the composition Pb-97.5 wt% Sn, and the liquid with the eutectic composition Pb-61.9 wt% Sn. Application of the Gibbs Phase Rule to this system indicates that at the eutectic temperature there are no degrees of freedom, and the temperature and compositions of the three phases present are fixed at the values given.
From: Askeland, "The Science and Engineering of Materials," PWS (1994)