Analysis of ferrite formed in a 321 grade austenitic stainless steel.pdf (984.92 kB)
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journal contribution
posted on 2015-07-30, 13:05 authored by Graham Green, Rebecca HigginsonRebecca Higginson, Simon HoggSimon Hogg, Sarah Spindler, Christopher Hamm, J. NajorkaA significant fraction of ferrite has been identified in a 321 grade austenitic stainless steel in the
solution heat treated condition. The microstructures were analysed using electron backscatter
diffraction, energy dispersive X-ray spectroscopy and X-ray diffraction (XRD) and the stability of
the ferrite investigated using heat treatments in a tube furnace, dilatometry and high temperature
XRD. The ferrite dissolved ,800uC, then formed again on cooling at temperatures under 200uC.
Thermodynamic predictions showed a significant ferrite content at room temperature under
equilibrium conditions, and the DeLong diagrams predict an austenitezmartensite microstructure
in the cast condition. Sensitivity analysis on the DeLong diagram has shown that the nitrogen
content had a large effect on the austenite stability. The instability of the austenite and the
subsequent transformation to ferrite on cooling can be attributed to low nitrogen content
measured in the as received material. It was found that thermal aging of the material caused
further transformation of austenite to ferrite as well as the formation of sigma phase that appears
higher in nitrogen than the matrix phases. The diffusion of nitrogen into sigma phase may cause
instability of the austenite, which could cause further transformation of austenite to ferrite on
cooling from the aging temperature. The transformation of austenite to ferrite is known to be
accompanied by an increase in volume, which may be of relevance to components made with
tight dimensional tolerances.
Funding
The authors would like to thank EDF Energy and Loughborough University for providing the funding and the materials for this project.
History
School
- Aeronautical, Automotive, Chemical and Materials Engineering
Department
- Materials
Published in
MATERIALS SCIENCE AND TECHNOLOGYVolume
31Issue
4Pages
418 - 425 (8)Citation
GREEN, G. ... et al, 2015. Analysis of ferrite formed in 321 grade austenitic stainless steel. Materials Science and Technology, 31 (4), pp.418-425.Publisher
Maney Publishing / © Institute of Materials, Minerals and MiningVersion
- AM (Accepted Manuscript)
Publisher statement
This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/Publication date
2015ISSN
0267-0836Publisher version
Language
- en