The approach to equilibrium during tempering of a bulk nanocrystalline steel: an atom probe investigation
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A local electrode atom probe has been used to analyze the solute partitioning during bainite transformation in a novel, nanocrystalline bainitic steel. Atom probe results show the absence of any partitioning of substitutional elements between the phases involved. The results are fully consistent with the diffusionless transformation of austenite to bainite. However, substitutional elements are expected to redistribute approaching an equilibrium phase boundary as the mixture of bainitic ferrite and retained austenite is tempered. The compositional analysis of the austenite/ferrite interface by atom probe tomography indicates that retained austenite decomposes during tempering before equilibrium is reached at the interface.
KeywordsFerrite Austenite Bainite Atom Probe Bainitic Ferrite
The authors acknowledge financial support from European Coal and Steel Community (ECSC 7210-PR-345) and Spanish Ministerio de Ciencia y Tecnología (Project-2006 6 0I 029). CGM would also like to thank Spanish Ministerio de Ciencia y Tecnología for the financial support in the form of a Ramón y Cajal contract (Programa RyC 2004). Research at the Oak Ridge National Laboratory SHaRE User Facility was sponsored by the Office of Basic Energy Sciences, Division of Scientific User Facilities, U.S. Department of Energy, under contract DE-AC05-00OR22725 with UT-Battelle, LLC.
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