Kinetics and Microstructural Control

· The T-T-T diagram involves Isothermal transitions through the start-finish contours for the γ -> α + Fe3C reactions.
· The initial state above TE is a homogeneous polycrystalline Austenite that is rapidly cooled to the temperature of the desired isotherm, missing the "nose" of the T-T-T curve.
· Pearlite and Bainite are equilibrium two-phase materials consisting of

Ferrite (αFe) and Cementite ( Fe3C).
· In Pearlite, Iron carbide nucleates at the Austenite grain boundaries removing carbon from the αFe.