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

Abstract

A fine-scale bainitic microstructure with high strength and high toughness has been achieved by transforming austenite at 200 ºC. X-ray diffraction analysis showed the carbon concentration of these bainitic ferrite plates to be higher than expected from paraequilibrium. 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 supersaturated bainitic ferrite and therefore alters the carbide precipitation sequence during low temperature bainite formation