Study of austempering kinetics of high silicon bainitic cast steels

Abstract

This study investigates the effect of chemical composition and microsegregation on the bainitic transformation of high Si cast steels at two different austempering temperatures. The advance of the bainite precipitation as a function of time and temperature was monitored through measurements of the amount of retained austenite by X-ray diffraction, the evolution of hardness and microstructural characterization. The results showed that the bainitic transformation starts preferentially at zones with lower contents of alloying elements but later covers the entire matrix. The austempering heat treatments resulted in an apparently homogeneous bainitic microstructure throughout the entire matrix after a short period of time. The results encourage the continuation of the development of high Si steels suitable to produce carbide-free austempered cast parts.