Isothermal transformation of low-carbon microalloyed steels

The microstructures of isothermal transformation products and time-temperature-transformation (TTT) diagrams of two low-carbon microalloyed steels have been investigated by the means of dilatation and microscopy. The results show there are three independent “C-shape” curves in the TTT diagrams of low-carbon microalloyed steels, namely, the polygonal ferrite/pearlite transformation “C-shape” curve, the massive ferrite transformation “C-shape” curve and the bainitic transformation “C-shape” curve, respectively. The effects of the carbon and Mo content on massive ferritic transformation are discussed.