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W. Mayer, Y.V. Shan, E. Povoden-Karadeniz, E. Kozeschnik:
"A model for the disorder → order transformation during Fe₃C precipitation in martensite";
Talk: PTM 2015 Solid-Solid Phase Transformation in Inorganic Materials, Whistler; 2015-06-28 - 2015-07-03; in: "Proceedings of the International Conference on Solid-Solid Phase Transformations in Inorganic Materials 2015", (2015), ISBN: 978-0-692-43736-0; 283 - 284.

We present a new theoretical approach to simulate the sequence from metastable disordered C-rich cluster formation and defect segregation to stable cementite (Fe3C) precipitation in low and medium carbon martensitic steel. The freshly quenched virgin bct martensite is treated as a highly supersaturated solid solution of C in a heavily defect-loaded Fe matrix where, on tempering, a strong driving force for precipitation of carbides exists that are, however, experimentally not observed. In our model, in the 0th stage of tempering, C atoms either segregate to lattice defects (dislocations, grain and phase boundaries) or form Fe-rich C-clusters. These metastable configurations delay, or even suppress, the precipitation of Fe3C at low temperature. Using the thermo-kinetic software MatCalc we simulate tempering, taking into account the full sequence of C trapping to dislocations, the formation of C clusters and, finally, transformation to stable Fe3C carbide precipitates with an (ordered) orthorhombic crystal structure.

order-disorder transformation, early stage of precipitation, martensite, Fe3C