Austenite double decomposition into bainite in high carbon steels

This paper describes a model of bainitic transformation. The model takes into consideration a range of lower bainite in high carbon steels (the swing back effect near the temperature Ms). The models take into account a simultaneous decomposition of austenite into two transformation products: bainite at the austenite grain boundary and on martensite spines. Analyses concerning the nucleation of sub-plates have been presented. Having two models assumes that the subplate growth is of a logarithmic and exponential character. In order to calculate a volume fraction of two components of bainite fB1 and fB2 , formulas linking an actual volume increase of the components with their current growth have been applied, leading to extended volume. The results of dilatometric studies and quantitative analyses of micro structural components were used in optimizing procedures.