Mössbauer Effect Study on the Isothermal Transformation of Austenite in a SUP6 Steel

The isothermal transformation of austenite in a SUP6 steel has been investigated by means of Mössbauer spectroscopy. The amount of retained austenite and its carbon content are measured as a function of holding time at an annealing temperature.Carbon content of retained austenite increases with time up to 1.8%, which may be overestimated by the thickness effect, during annealing at 723 K. The amount of retained austenite at room temperature changes linearly with carbon content of austenite. Retained austenite is formed when its carbon content exceeds about 1.0%. The decrease in carbon content and the amount of retained austenite is accompanied by the formation of χ-Fe5C2 carbide.