Paper Title:

Understanding of the Bainite Transformation in a Nano-Structured 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 123-128
DOI 10.4028/www.scientific.net/SSP.172-174.123
Citation Peter D. Hodgson et al., 2011, Solid State Phenomena, 172-174, 123
Online since June 2011
Authors Peter D. Hodgson, Ilana Timokhina, Xiang Yuan Xiong, Yoshitaka Adachi, Hossein Beladi
Keywords APT, Electron Backscatter Diffraction (EBSD), High Strength Steel (HSS), Nanostructured Bainitic Steel, TEM
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A 0.79C-1.5Si-1.98Mn-0.98Cr-0.24Mo-1.06Al-1.58Co (wt%) steel was isothermally heat treated at 200°C for 10 days to form a nano-scale bainitic microstructure consisting of nanobainitic ferrite laths with high dislocation density and retained austenite films. The crystallographic analysis using TEM and EBSD revealed that the bainitic ferrite laths are close to the Nishiyama-Wassermann orientation relationship with the parent austenite. There was only one type of packet identified in a given transformed austenite grain. Each packet consisted of two different blocks having variants with the same habit plane, but different crystallographic orientations. The presence of fine C-rich clusters and Fe-C carbides with a wide range of compositions in bainitic ferrite was revealed by Three-dimensional Atom Probe Tomography (APT). The high carbon content of bainitic ferrite compared to the para-equilibrium level of carbon in ferrite, absence of segregation of carbon to the austenite/bainitic ferrite interface and absence of partitioning of substitutional elements between the retained austenite and bainitic ferrite were also found using APT.