A eutectic alloy is
a) one which behaves like a pure or single metal on heating. In other words it melts from solid
to liquid with no transition through some pasty phase.
b) It is the lowest melting point composition.

If you have a non eutectic composition what happens on heating is the eutectic mixture will melt
and the "surplus" constituent will still be solid. A liquid with solids mixed into it is a
paste.

So if you have say, a mixture of equal portions of tin and lead (50Sn/50Pb), on heating the
eutectic (63/37) will melt into a liquid leaving the surplus lead floating around till it too
melts / dissolves.
This is what the phase diagrams you see in text books/supplier literature etc are describing.

Mike

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