Solidus and liquidus surfaces of ternary systems
Equilibrium diagrams

If the constituents are fully miscible in both solid and liquid phases, they form binary diagrams with either a single solidification spindle, or a double spindle with a congruence point at a temperature extremum. The resulting ternary diagrams are generally of the same type. If no binary has a congruent melting composition, the same is generally true in ternary diagrams. If all binaries show a congruence point, the ternary diagram also has a ternary congruent melting composition distinct from the three binary congruent compositions. Ternary congruence is also conceivable in systems with a single or even two binary congruences. We won't go into detail here.