Glass Forming Ability of Bulk Metallic Glasses

The glass forming ability (GFA) of a liquid is defined as the ability of the melt to bypass crystallization and to freeze into a glass. In this sense, it is connected through the crystal nucleation and growth theory to the thermodynamics and kinetics of the system, namely the driving force for crystallization, the interfacial energy between the liquid and the primary crystalline phase, and the temperature dependent viscosity or diffusivity of the alloy. In this chapter, after a short introduction of some simple empirical rules for GFA, the concept of glass forming ability as the ability of the melt to bypass crystallization will be described in terms of thermodynamic and kinetics factors that determine the time-temperature-transformation (TTT) diagram.