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Quenching and partitioning (Q&P) process [1] is a heat treatment to produce steels with high strength and ductility. Chemical composition and process parameters control the final phase composition of a Q&P steel, thereby influencing its mechanical properties [2]. The objective of this work is to analyse computationally the effect of the composition and process parameters on the mechanical properties of Q&P steel.
The chemical composition is initially optimised in terms of alloying elements that strongly affect hardness. A set of most promising compositions are then used to evaluate the impact of process parameters by simulating different stages of the Q&P process. For the quenching process, the phases evolved at the end of the quenching process are predicted based on a coupled Finite Element- Thermo-kinetic approach. As a second step, the results of the quenching process are used as input for simulating the partitioning process. Here, a thermo-kinetic approach is employed to predict the microstructure evolution by varying parameters, such as prior austenite grain size, stop quenching temperature, and the partitioning time. The mechanical properties of the steel are estimated using the final phase fractions and their corresponding carbon contents obtained from the simulations.
[1] J. G. Speer, D. Matlock, B. C. De Cooman, and J. G. Schroth, “Carbon partitioning into austenite after martensite transformation”, Acta Materialia, vol. 51, pp. 2611-2622 (2003)
[2] Gawad J., Iaconeta I., Bhogireddy S.P., Hernaut P., Lebedev A., Wierink G., de Cooman B.C. “A numerical model for the prediction of microstructure distribution across thickness of quenched steel plates” Materials Science Forum, Vol. 949, pp. 32-39 (2019)