In situ synchrotron X-ray diffraction and dilatometric study of austenite formation in a multi-component steel: Influence of initial microstructure and heating rate

In situ synchrotron X-ray diffraction and dilatometric study of austenite formation in a multi-component steel: Influence of initial microstructure and heating rate

The formation of austenite during both slow and fast heating (0.25-100 degree Cs-1) was investigated for different microstructures of a selected low-alloy steel. With the simultaneous use of dilatometry and high-energy X-ray diffraction, it was possible to follow not only the global progress of the...

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Bibliographic Details
Published in:Acta materialia Vol. 80; pp. 118 - 131
Main Authors: ESIN, V. A, DENAND, B, LE BIHAN, Qu, DEHMAS, M, TEIXEIRA, J, GEANDIER, G, DENIS, S, SOURMAIL, T, AEBY-GAUTIER, E
Format: Journal Article
Language:English
Published: Kidlington Elsevier 01-11-2014
Subjects:
Applied sciences
Austenitizing
Carbides
Cementite
Condensed Matter
Diffraction
Dilatometry
Exact sciences and technology
Ferrite
Materials Science
Metals. Metallurgy
Microstructure
Physics
Transformations
Austenitization
Dilatometry
Heating rate
In situ
Austenite
DICTRA
Microstructure
X ray diffraction
In situ synchrotron XRD
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Summary:The formation of austenite during both slow and fast heating (0.25-100 degree Cs-1) was investigated for different microstructures of a selected low-alloy steel. With the simultaneous use of dilatometry and high-energy X-ray diffraction, it was possible to follow not only the global progress of the austenitization, but also the individual evolutions of each phase (ferrite, cementite and retained austenite if present in the initial microstructure). The results confirm earlier published data regarding the ease of austenitization of different initial microstructures (ferrite-pearlite, bainite and tempered martensite). More importantly, two stages were clearly identified, corresponding to the simultaneous transformation of ferrite and cementite, followed by the progressive disappearance of the remaining ferrite. While this is well known for ferrite-pearlite microstructures, it is not yet documented for bainite and tempered martensite. Microstructure evolution calculations based on a diffusion-controlled mechanism helped rationalize the differences observed between the three initial microstructures. In addition, they also strongly suggested the existence of a critical carbide size beyond which the second austenitization phase would correspond to carbide dissolution instead of ferrite transformation.
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ISSN:1359-6454
1873-2453
DOI:10.1016/j.actamat.2014.07.042