ABSTRACT
The description of phase changes and the influence of pressure are important technologically. This chapter considers the field of phase transformations. The subject of solid-solid transformations is a very complex one both from the thermodynamic and the kinetic point of view. Thermodynamic factors governing the equilibrium transition at high pressures can be conveniently illustrated with the case of the graphite-to-diamond equilibrium line. The basic principles of solid-vapor equilibrium are essentially the same as liquid-vapor equilibrium. Kinetic factors in practice play the most important role in phenomena associated with solid-solid transformations. The rate of transformation is the key variable in nucleation and growth processes. An increase in pressure can change the character of phase diagrams, make components soluble or insoluble in one another, and in the case of solids allow new phases to be created, and in some cases retained. There are few applications of high pressure to commercial processes involving solid-solid transformations.
