Dual-Phase (DP) steels are low-alloy steels with microstructures composed of ferrite and martensite. The dispersed martensite on the soft matrix of ferrite in DP steels results in superior cold formability due to the continuous yielding behavior, the low proof stress to tensile strength ratio as well as the high uniform and total elongation values.
This work focuses on simulating the intercritical annealing of DP steels. The modelling approach is a combination of thermodynamic and kinetic calculations as well as semi empirical models. Specifically, thermodynamic calculations were performed using the CHALPAD method with the commercial software Thermo-Calc and the TCFE6 database. Kinetic simulations were carried out using the multi component diffusion module DICTRA, coupled with the TCFE6 thermodynamic and the MOBFE2 kinetic database. For the cooling part, following intercritical annealing, a semi empirical Matlab model is employed. In order to determine the M_S temperature in austenite and the transformation fraction profiles of the final microstructure, the Barbier equation  and the Koistinen-Marburger model  are incorporated into the Matlab code.
The simulation predicts the evolution of the volume fractions of phases as well as the carbon content of martensite in the microstructure of DP steels. A map is constructed including volume fraction martensite and associated carbon content as a function of intercritical annealing temperature, time and other process parameters. These maps can be used for the design of heat treatment for optimized DP steel compositions.