ABSTRACT
This chapter talks about phase transformations in closed thermodynamic systems. It is appropriate to first define the terms phase and phase transformation. Each phase in a material system generally exhibits a characteristic set of physical, mechanical and chemical properties and is, in principle, mechanically separable from the whole. Phase transformation in a material system occurs when one or more of the phases in a system change their state of aggregation, crystal structure, and degree of order or composition resulting from a reconfiguration of the constituent particles comprising the phase. This reconfiguration is a change in the thermodynamic state leading to a more stable condition described by appropriate thermodynamic potentials such as a decrease in the Gibbs free energy (G) at constant temperature (T) and pressure (P). The decrease in free energy accompanying the reconfiguration is often referred to as the thermodynamic "driving force" for the phase change. The chapter discusses selected aspects of the thermodynamics of phase transformations.
