Atomic scale observations of bainite transformation in a high carbon high silicon steel

A fine-scale bainitic microstructure with high strength and high toughness has been achieved by transforming austenite at 200 degrees C. X-ray diffraction analysis showed the carbon concentration of these bainitic ferrite plates to be higher than expected from para-equilibrium. Atom-probe tomography revealed that a substantial quantity of carbon was trapped at dislocations in the vicinity of the ferrite-austenite interface. These results suggest that the carbon trapping at dislocations prevents the decarburization of super-saturated bainitic ferrite and therefore alters the carbide precipitation sequence during low-temperature bainite formation. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.