intermediate phases

Phase Diagrams with Intermediate Phases
and Compounds
Terminal phase: a solid solution of one component in another for which one boundary of the phase field is a pure component.
Intermediate phase: a phase whose composition range is between those of terminal phases.



Phase diagrams with intermetallic compounds:
Besides solid solutions, intermetallic compounds, that
have precise chemical compositions can exist in some
systems.When using the lever rules, intermetallic compounds are treated like any other phase, except they appear not as a
wide region but as a vertical line.
This diagram can be thought of as two joined eutectic
diagrams, for Mg-Mg2Pb and Mg2Pb-Pb. In this case
compound Mg2Pb can be considered as a component.

Congruent phase transformations:
A congruent transformation involves no change in
composition (e.g., allotropic transformation such as ?-Fe to
?-Fe or melting transitions in pure solids).
For an incongruent transformation, at least one phase
changes composition (e.g. eutectic, eutectoid, peritectic
reactions).