Atomistic Modelling of η-Fe2C Formation During Low-Temperature Tempering of Martensitic Carbon Steel

Kurzfassung

The control of carbide formation is crucial for the development of advanced steels. One of the more stable carbides occurring at room temperature ageing of martensite is η-Fe2C. In this work, we study structural transformations which occur during low-temperature ageing in Fe-C martensite using computer modelling based on the atomic density field method. It is shown that homogeneous bct solid solution with 2at.% of C undergoes bct → η-Fe2C transformation. An important result is that the ordering Fe2C structure may be considered a deformed rutile structure. In addition, the link between η-carbide and other meta-stable carbides is discussed based on the Fe2n+1Cn (n=1,2,3,…) Magnéli phases. The Magnéli phases comprise a sequence of carbon-rich 110α′ layers with different periods to accommodate the loss in stoichiometry. The simulated microstructure is compared to experimental data found in the literature.