Metallurgical and Materials Transactions A

, Volume 44, Issue 11, pp 5177–5191

On the Low Temperature Strain Aging of Bainite in the TRIP Steel

  • Ilana Timokhina
  • Hossein Beladi
  • Xiang-Yuan Xiong
  • Peter D. Hodgson
Article

DOI: 10.1007/s11661-013-1864-y

Cite this article as:
Timokhina, I., Beladi, H., Xiong, X. et al. Metall and Mat Trans A (2013) 44: 5177. doi:10.1007/s11661-013-1864-y

Abstract

The aging behavior of a thermomechanically processed Mo-Al-Nb transformation-induced plasticity steel with ultrafine microstructure was investigated using transmission electron microscopy and atom probe tomography (APT). Strain aging at 73 K (200 °C) for 1800 seconds led to a significant bake-hardening response (up to 222 MPa). Moreover, aging for 1800 seconds at room temperature after 4 pct pre-strain also revealed a bake-hardening response (~60 MPa). The experimental results showed the formation of carbon Cottrell atmospheres around dislocations and the formation of carbon clusters/fine carbides in the bainitic ferrite during aging. It is proposed that this is associated with the high dislocation density of bainitic ferrite with formation of a complex dislocation substructure after pre-straining and its high average carbon content (~0.35 at. pct). The segregation of carbon and substitutional elements such as Mn and Mo to the retained austenite/bainitic ferrite interface during aging was observed by APT. This segregation is likely to be the preliminary stage for Mo-C particles’ formation. The aging after pre-straining also induced the decomposition of retained austenite with formation of ferrite and carbides.

Copyright information

© The Minerals, Metals & Materials Society and ASM International 2013

Authors and Affiliations

  • Ilana Timokhina
    • 1
  • Hossein Beladi
    • 1
  • Xiang-Yuan Xiong
    • 2
  • Peter D. Hodgson
    • 3
  1. 1.Institute for Frontier Materials, GTP Research, Geelong Technology PrecinctDeakin UniversityGeelongAustralia
  2. 2.Centre for Electron MicroscopyMonash UniversityClaytonAustralia
  3. 3.Institute for Technology Research and InnovationDeakin UniversityGeelongAustralia