Application of transformation diagrams to predict phase transformation in alloys

Abstract

Equilibrium phase diagrams give information on the phases present and their compositions at equilibrium in alloy systems. Most metallurgical processes deviate significantly from equilibrium due to constraints imposed by kinetics of heat and mass transfer. The transformation diagrams can be used to study the non-equilibrium phase transformation processes as well as phase equilibria. They can be employed to address several questions which arise during the modeling of the processes but are analysed conventionally through empirical means. For example, these can be used to predict the interface composition in under-cooled melts and similar cases. These can be adopted to predict the conditions under which meta-stable phases are formed. The construction of these diagrams is similar to that of the conventional phase diagrams. They can be easily constructed using conventional data bases on the thermodynamics of alloys. The construction of these diagrams, their salient features and application are discussed.