Methods of Obtaining Experimental Data for the Construction of Phase Diagrams

The construction of a phase diagram of a multi-component system requires knowledge of the equilibrium phase relations of that system. This means establishing the phases existing at various temperatures for selected compositions within the system. The positions of invariant points, liquidus lines or surfaces, and other points, lines, or surfaces at which phase reactions occur must represent phase relations for equilibrium conditions. This can be especially difficult for many systems, such as the silicate systems, in which many metastable conditions exist and equilibrium phases are difficult to attain. Below is a list of important factors that must be considered in the determination of phase-equilibrium relations.

With the criteria listed above in mind, phase equilibria relations are determined through many techniques, each falling under one of the following categories:

Once phase equilibrium relations are established, it is necessary to identify the phases present in the specimen. The primary methods of phase identification are the following:

These methods account for over 95% of direct phase identification. Other techniques include: (you can find a discussion on these topics in Volume I of Phase Diagrams: Materials Science and Technology, edited by Allen M. Alper, or in any book about phase diagrams)

Susana Castro 4/28/96

Project Hompage | Experimental Page | Reference Page