Phase transformation behavior of Grade 91 ferritic steel

The phase transformation behavior of Grade 91 steel, which is an advanced ferritic steel, has been investigated using differential thermal analysis (DTA). In our DTA experiments, disk-shaped samples were normalized at 1080 °C, and then tempered at temperatures between +10 °C and −40 °C of the ferrit...

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Bibliographic Details
Published in:Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2009-06, Vol.510, p.158-161
Main Authors: Tokunaga, T., Hasegawa, K., Masuyama, F.
Format: Article
Language:English
Subjects:
Applied sciences
Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
Cross-disciplinary physics: materials science
rheology
Differential thermal analysis
Exact sciences and technology
Ferritic steels
Hardening. Tempering
Heat treatment
Magnetic transition
Materials science
Metals. Metallurgy
Phase diagrams and microstructures developed by solidification and solid-solid phase transformations
Phase transformation
Physics
Production techniques
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Summary:The phase transformation behavior of Grade 91 steel, which is an advanced ferritic steel, has been investigated using differential thermal analysis (DTA). In our DTA experiments, disk-shaped samples were normalized at 1080 °C, and then tempered at temperatures between +10 °C and −40 °C of the ferrite to austenite transformation temperature ( A c1 temperature) determined during normalizing, at a heating and cooling rate of 30 °C/min. The DTA curves on heating during normalizing showed that a magnetic transition and the A c1 transformation temperatures occurred at 744 °C and 847 °C, respectively. Two overlapping exothermic peaks were observed in the temperature range 770–700 °C in the DTA cooling curves after tempering at temperatures between +10 °C and −30 °C from the A c1 temperature. A partial austenitization seemed to have occurred, even when holding the tempering temperature below the A c1 temperature and, thus, the high temperature peak was due to the austenite to ferrite transformation. The low temperature peak corresponded to a magnetic transition. The formation of ferrite during cooling after tempering can be considered to arise from the heat evolved from the magnetic transition, which influences the localized cooling of the sample near the Curie temperature.
ISSN:0921-5093
1873-4936
DOI:10.1016/j.msea.2008.05.059