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Green G, Higginson R, Hogg S, Spindler S and Hamm C, Materials Science and Technology, 2014.pdf (926.87 kB)

Evolution of sigma phase in 321 grade austenitic stainless steel parent and weld metal with duplex microstructure

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journal contribution
posted on 2015-07-30, 13:11 authored by Graham Green, Rebecca HigginsonRebecca Higginson, Simon HoggSimon Hogg, Sarah Spindler, Christopher Hamm
Samples of 321 stainless steel from both the parent and welded section of a thin section tube were subjected to accelerated ageing to simulate long term service conditions in an advanced gas cooled reactor (AGR) power plant. The initial condition of the parent metal showed a duplex microstructure with approximately 50% ferrite and 50% austenite. The weld metal showed three distinct matrix phases, austenite, delta ferrite and ferrite. This result was surprising as the initial condition of the parent metal was expected to be fully austenitic and austenite+delta ferrite in the weldment. The intermetallic sigma phase formed during the accelerated ageing was imaged using ion beam induced secondary electrons then measured using computer software which gave the particle size as a function of aging time. The measurements were used to plot particle size, area coverage against aging time and minimum particle spacing for the parent metal. During aging the amount of ferrite in the parent metal actually increased from ∼50 to ∼80% after aging for 15 000 h at 750°C. Sigma has been observed to form on the austenite/ferrite boundaries as they may provide new nucleation sites for sigma phase precipitation. This has resulted in small sigma phase particles forming on the austenite/ferrite boundaries in the parent metal as the ferrite transforms from the austenite.

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 TECHNOLOGY

Volume

30

Issue

12

Pages

1392 - 1398 (7)

Citation

GREEN, G. ... et al, 2014. Evolution of sigma phase in 321 grade austenitic stainless steel parent and weld metal with duplex microstructure. Materials Science and Technology, 30 (12), pp. 1392 - 1398.

Publisher

Maney Publishing / © Institute of Materials, Minerals and Mining

Version

  • 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

2014

Notes

This article was published in the journal, Materials Science and Technology [Maney Publishing / © Institute of Materials, Minerals and Mining] and the definitive version is available at: http://dx.doi.org/10.1179/1743284713Y.0000000452

ISSN

0267-0836

Language

  • en