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[en] Highlights: • Fine grained bainite–aided DP steel was produced by CGP and intercritical annealing with the achieved grain size of 470 nm. • Fine morphologies, high dislocation densities and carbon content of bainite resulted in the largest BH value. • Flow curves of DP steels before and after BH can be fairly described by micromechanics based model and RVE simulation. • DP microstructure with bainite showed more homogeneous stress and strain distributions and large energy absorption value. Bake hardening (BH) effects of dual phase (DP) steels with consideration of grain size and bainitic phase were investigated. Basically, after BH process, DP steels exhibited complex microstructure characteristic including Cottrell atmosphere, precipitation in ferrite and tempered martensite. Firstly, severe plastic deformation, namely, constrained groove pressing (CGP) was applied to a ferrite–pearlite low carbon steel for producing fine grain microstructure with submicron size. Subsequently, DP steel and DP steel with bainite were generated by intercritical annealing following by water and oil quenching, respectively. The BH at the temperature of 160 °C for 20 min was performed for steel samples with different microstructures after pre-straining to 2, 6 and 10%. Obviously, fine grain structure and bainite could effectively increase the bake hardenability of the examined steels. Additionally, micromechanics based modeling for describing flow stress behavior of the DP steels after BH was done. Hereby, influences of carbon accumulation, occurred carbides and softened martensite were incorporated. Accordingly, the flow curves of the investigated DP steels before and after BH were fairly predicted by means of representative volume element (RVE) finite element (FE) simulations. The increased yield strengths, BH values and resulting strain hardening curves could be accurately described.