TERMS USED IN EQUILIBRIUM DIAGRAMS

The following terms are frequently used in the study of solid phases and phase diagrams:

 i. Alloy

 ii. System

 iii. Components

 iv. Phase

 v. Phase diagram

 vi. Phase Equilibrium

 vii. Phase Transformation

 viii. Structural constituents

 ix. GIBB’S PHASE RULE OR THE PHASE RULE OR CONDENSED PHASE RULE 

Phase diagram

          A graphical representation of the relationship between environmental constraints (e.g. temperature and sometimes pressure), composition, and region of phase stability, ordinarily under conditions of equilibrium.

          Most phase diagrams are prepared by using slow cooling conditions whereby phases are in equilibrium. One can get following important information's from the phase diagrams

• Phases at different composition and temperature
• Equilibrium solubility of one element or compound in another element
• Melting points of different phases in an alloy
• Temperature of solidification or range of solidification of an alloy. 

Phase Equilibrium & Phase Transformation

Phase Equilibrium:

          The state of a system where the phase charecteristics remain constant over indefinite time periods. At equilibrium the free energy is a minimum.

        In an equilibrium diagram, liquid is one phase and solid solution is another phase.

Phase Transformation:

          A change in the number and/or character of the phases that constitute the microstructure of an alloy.