<abstract xml:lang="en" xmlns="http://www.w3.org/1999/xhtml">The paper presents an investigation of the carbon concentration in the residual austenite and the time required for the diffusion of carbon out of supersaturated sub-units of ferrite into the retained austenite. Experimental measurements of volume fraction of bainitic ferrite and volume of the untransformed austenite indicate that there is a necessity of carbides precipitation from austenite. A consequence of the precipitation of cementite from austenite during austempering is that the growth of bainitic ferrite can continue to larger extent and that the resulting microstructure is not an ausferrite but is a mixture of bainitic ferrite, retained austenite and carbides. Additionally, carbon concentration in the residual austenite was calculated using volume fraction data of austenite and a model developed by Bhadeshia based on the McLellan and Dunn quasi-chemical thermodynamic model. The comparison of experimental data with the <italic>T0, T0'</italic> and <italic>Ae3'</italic> phase boundaries suggests the likely mechanism of bainite reaction in cast iron is displacive rather than diffusional. The carbon concentration in retained austenite demonstrates that at the end of bainite reaction the microstructure must consist of not only ausferrite but additionally precipitated carbides.</abstract>

The paper presents an investigation of the carbon concentration in the residual austenite and the time required for the diffusion of carbon out of supersaturated sub-units of ferrite into the retained austenite. Experimental measurements of volume fraction of bainitic ferrite and volume of the untransformed austenite indicate that there is a necessity of carbides precipitation from austenite. A consequence of the precipitation of cementite from austenite during austempering is that the growth of bainitic ferrite can continue to larger extent and that the resulting microstructure is not an ausferrite but is a mixture of bainitic ferrite, retained austenite and carbides. Additionally, carbon concentration in the residual austenite was calculated using volume fraction data of austenite and a model developed by Bhadeshia based on the McLellan and Dunn quasi-chemical thermodynamic model. The comparison of experimental data with the T0, T0' and Ae3' phase boundaries suggests the likely mechanism of bainite reaction in cast iron is displacive rather than diffusional. The carbon concentration in retained austenite demonstrates that at the end of bainite reaction the microstructure must consist of not only ausferrite but additionally precipitated carbides.

Carbon Diffusion During Bainite Reaction in Austempered Ductile Iron

Department of Materials Science and Engineering, Mechanical Engineering Faculty, University of Technology and Life Sciences, Bydgoszcz, av. Kaliskiego 7, 85-796 Bydgoszcz, Poland

Advances in Materials Science

{"article-title":"Carbon Diffusion During Bainite Reaction in Austempered Ductile Iron"}

The paper presents an investigation of the carbon concentration in the residual austenite and the time required for the diffusion of carbon out of...

Carbon Diffusion During Bainite Reaction in Austempered Ductile Iron

Publié en ligne: 23 sept. 2008

Pages: 80 - 93

DOI: https://doi.org/10.2478/v10077-008-0010-9

Mots clés
carbon diffusion, decarburization, bainite, ductile iron ADI

This content is open access.

Carbon Diffusion During Bainite Reaction in Austempered Ductile Iron

Publié en ligne: 23 sept. 2008

Pages: 80 - 93

DOI: https://doi.org/10.2478/v10077-008-0010-9

Mots cléscarbon diffusion, decarburization, bainite, ductile iron ADI

This content is open access.

Mots clés
carbon diffusion, decarburization, bainite, ductile iron ADI