Quenching and partitioning (Q&P) treatment is a novel process to produce advanced high-strength steel. In this study a medium-carbon steels with high Ni content (9.8 wt%) steel is designed for the study of kinetics of carbon partitioning. Atom probe tomography were utilized to gain insights into phenomena that occur (such as carbon partitioning from martensite to austenite, carbon atom clustering/dislocation trapping). We also elucidated here the mechanistic contribution of the application of low temperature partitioning to this steel in obtaining a multiphase microstructure comprising of martensite and austenite (blocky retained austenite) that exhibited tensile strength of 2000MPa and to total elongation of 17% (Fig.1). The excellent mechanical properties are attributed to the stabilities of austenite and the good ductility of martensite by the carbon partitioning process at low temperature. Effective variations of the austenite stability is a contribution to ductility. Austenite becomes mechanically more stable and transforms at higher strains, hence the associated strain hardening effectively increases resistance to necking and fracture. Moderate strength ratio of austenite and martensite retard stress concentrations. The high density of clusters and dislocation in martensite provide an extra contribution to ductility and strength. The simple low temperature partitioning treatment is an effective way to obtain high stength high ductility steels.
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