The presence of bainite in the microstructure of steels to obtain a proper combination of strength and toughness has always been desired. The previous works however have shown that the presence of preferred bainite morphologies in the microstructure of any steel would not be readily accessible. In addition, the appearance of different bainite morphologies in the microstructure of any steel is dictated by different factors including the steel initial microstructure, austenitization characteristics, thermomechanical processing parameters and so on. Accordingly, in the present work, the effect of prior austenite grain size and the amount of austenite hot deformation on the bainite formation characteristics were investigated in 0.12C-2.5 Ni-1.2Cr steels. The results indicated that the prior austenite grain size and the amount of deformation in the austenite no-recrystallization region resulted in significant changes of the bainite formation kinetics and morphology.

Keywords: Bainite morphology, TMP, Low carbon steel, Ultra fine ferrite (UFF)