A global optimization technique to identify overall transformation kinetics using dilatometry data—applications to austenitization of steels

This paper presents the development of a new algorithm that is able to accurately identify the overall kinetics of diffusional phase transformations, including austenitization from dilatometry data. Such algorithm is useful in the study of the role of microstructural features in the kinetics of austenitization. Specifically, the fundamental parameters governing the nucleation and growth of the new phase in diffusional transformations are determined by minimizing the error between the measured dilatometry curves and that calculated by the pre-specified kinetic model. In the process, the progress of transformation in the particular dilatometry tests can also be determined simultaneously. The accuracy and applicability of the developed algorithm is demonstrated by using the dilatometry data of AISI 1080 steel in austenitization as well as several hypothetical transformations. A TTT diagram of austenitization of AISI 1080 is generated.