Intercritical continuous cooling transformation diagram for the manufacture of low-alloyed low-carbon multiphase steels

[Display omitted] •Intercritical continuous cooling transformation diagram for multiphase steels.•Intercritical austenite transforms into proeutectoid ferrite, bainite and martensite.•Multiphase steels obtained in a wide range of cooling rates (1 °C/s to 100 °C/s).•Temperatures for martensite decrease with the decrease in cooling rate. This paper deals with the construction of an experimental intercritical continuous cooling transformation (CCT) diagram for the manufacture of low-alloyed low-carbon multiphase steels. An in-situ dilatometric study was conducted both to determine the critical transformation temperatures and to follow the evolution of austenite on continuous heating. A quantitative analysis of the transformed austenite was conducted from the dilation curves using the lever rule method to further investigate the intercritical austenite decomposition for different cooling rates. Time and temperatures required for phase transformations were determined from the first derivative of the dilation curves, obtained as a function of cooling rate. Critical points were then plotted to construct the corresponding CCT diagram. Results show that the experimental CCT diagram can be used to design thermal cycles for the development of multiphase steels.