Paper Title:

Influence of the Austempering Temperature on the Microstructure and Crystallography of a Carbide-Free Bainitic Steel

Periodical Solid State Phenomena (Volumes 172 - 174)
Main Theme Solid-Solid Phase Transformations in Inorganic Materials
Edited by Yves Bréchet, Emmanuel Clouet, Alexis Deschamps, Alphonse Finel and Frédéric Soisson
Pages 797-802
DOI 10.4028/www.scientific.net/SSP.172-174.797
Citation Jean Christophe Hell et al., 2011, Solid State Phenomena, 172-174, 797
Online since June, 2011
Authors Jean Christophe Hell, Moukrane Dehmas, Guillaume Geandier, Nathalie Gey, Sebastien Allain, Alain Hazotte, Jean Philippe Chateau
Keywords Carbide-Free Bainite, Cell Parameter, Microstructure, Microtexture, Retained Austenite, Synchrotron Radiation (XRD), Volume Fraction
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Abstract

We elaborated two carbide-free bainitic steels with different microstructures through specific heat treatments and alloy design. EBSD analysis was used to point out major differences in these microstructures. In-situ characterizations of the bainitic transformation were performed by high energy synchrotron diffraction to go further into the study of each phase characteristics. The elaborated microstructures exhibited various phase fractions of bainitic ferrite, retained austenite and blocks of martensite and retained austenite. Moreover, the volume fraction of retained austenite increased with higher austempering temperatures. On the other hand, the austempering temperatures showed a strong influence on the kinetics of the bainitic transformation. Isothermal transformation under Ms showed a two stage transformation which led first to the formation of self-tempered martensite and then to bainitic ferrite. Furthermore, the evolution of the austenitic cell parameter showed enrichment in carbon ruled by diffusional mechanisms.