In-situ quantification and density functional theory elucidation of phase transformation in carbon steel during quenching and partitioning

Phase transformation in low alloyed Fe-C steels during quenching and partitioning (Q&P), though authentically attributed to carbon diffusion, is scarcely quantified experimentally terms of microstructural evolution lack fundamental backing at a quantum mechanics level. Herein, we report on combined in-situ high energy synchrotron X-ray diffraction density functional theory (DFT) study unveil the physical mechanism phase Q&P processed advanced steel. Beside small fraction bainite, air-quenching rate ∼6 °C/s Ms temperature range leads enrichment into untransformed austenite, which simultaneously turns up with later stage martensitic existing austenite/martensite interfaces. The resulting transformations are ascertained by DFT results second barrier ferrite/martensite facilitation diffusion austenite elevated temperatures, along well-known solubility difference/equilibrium martensite. development cubic martensite steel theoretically elucidated more probable hopping sites paths than austenite.