ABSTRACT
In a ternary system, application of the Phase Rule shows that there are three degrees of freedom; thus it is necessary to define the temperature and the concentrations of two components to define the state. To represent completely the phase equilibria at constant pressure in a ternary system, a three dimensional model, commonly termed a space model, is required; the representation of composition requires two dimensions, and that of temperature, a third dimension. Regarding the composition triangle the three corners represent the three components, points on the sides represent binary alloys, and points within the triangle ternary alloys. In a ternary solution, one type of atom may be located substitutionally and another interstitially. In general, except for relatively simple cases, it is difficult to depict clearly by means of perspective diagrams the complete ternary space model with its constituent spaces, curves, and points. The chapter also presents an overview of the key concepts discussed in this book.
