Atom-probe and x-ray diffraction analysis of the composition and structure of precipitates formed on tempering of ternary iron-carbon-nitrogen martensites

Conference item

X-ray diffraction analysis showed that both alpha ''-type precipitates (as in Fe-N) and epsilon/eta-type precipitates (as in Fe-C) develop in ternary Fe-C-N martensite upon tempering below 450 K. Atom-probe analysis was used to study the distribution of the interstitial atoms on a local scale. Most of the enriched regions formed after tempering contain both nitrogen and carbon atoms, but in an enriched region one type of interstitial is dominant. The carbon-rich regions contain a significantly larger amount of total interstitial atoms than the nitrogen-rich regions. The total interstitial amounts are close to that in epsilon/eta for the carbon-rich regions and close of that in alpha '' for the nitrogen-rich regions. This suggests that upon temper ing Fe-C-N martensite nitrogen atoms reside preferentially in an alpha ''-type structure and carbon atoms reside preferentially in an epsilon/eta-type structure, but that coprecipitation of nitrogen and carbon atoms occurs to a limited extent as well.

Authors: Bottger, A; vanGenderen, M; Sijbrandij, S; Mittemeijer, E; Smith, G

• Publication status: Published
• Journal: ISIJ INTERNATIONAL
• Volume: 36
• Issue: 7
• Pages: 764-767
• Publication date: 1996-01-01
• Event title: 4th International Conference on High Nitrogen Steels (HNS 95)
• DOI: 10.2355/isijinternational.36.764
• ISSN: 0915-1559
• Keywords: X-ray diffraction; martensites; phase transformations; atom-probe analysis; tempering; Fe-C-N