Phase Diagram

EUTECTOID AND PERITECTIC REACTIONS

The Eutectic Reaction

The Peritectic Reaction

• Examples: Cu-Zn, Fe-C, Ag-Pt

The Eutectoid Reaction

• Examples: Fe-C, Cu-Zn

The Peritectoid Reaction

• Examples: Ag-Al, Al-Cu

The Monotectic Reaction

• Examples: Cu-Pb

THE GIBBS PHASE RULE• This rule represents a criterion for the number of

phases that will coexist within a system at equilibrium, and is expressed by the simple equation

• P is the number of phases present• F is termed the number of degrees of freedom or the number

of externally controlled variables (e.g., temperature, pressure, composition)

• C is the number of components in the system.• N is the number of non compositional variables (e.g.,

temperature and pressure).