Characterization and modeling of mechanical behavior of quenching and partitioning steels

Q&P annealing was applied to cold rolled carbon-manganese steel with Si. Q&P cycles with different partitioning temperature and time were simulated and the evolution of microstructure and mechanical properties was investigated. All the microstructures were composed of three constituents: partitioned martensite, laths of retained austenite and MA islands. Fine microstructure characterization confirmed that C diffusion plays an important role for the stabilization of retained austenite at room temperature and further TRIP effect during mechanical loading. Good compromise between yield strength (~1200 MPa) and uniform elongation (~11%) was found in the case of 400 °C partitioning for 300 s due to the enhanced mechanical stability of retained austenite. Evolution of microstructure and mechanical properties was discussed and some mechanisms were proposed to explain the observations. Mechanical model for the prediction of stress-strain curves of Q&P steels was proposed, based on the obtained experimental data. Accurate prediction of stress-strain curves using model was achieved.