Lath formation mechanisms and twinning as lath martensite substructures in an ultra low-carbon iron alloy

Lath martensite is the dominant microstructural feature in quenched low-carbon Fe-C alloys. Its formation mechanism is not clear, despite extensive research. The microstructure of an Fe-0.05 C (wt.%) alloy water-quenched at various austenitizing temperatures has been investigated using transmission...

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Bibliographic Details
Published in:Scientific reports 2018-09, Vol.8 (1), p.14264-11, Article 14264
Main Authors: Ping, D H, Guo, S Q, Imura, M, Liu, X, Ohmura, T, Ohnuma, M, Lu, X, Abe, T, Onodera, H
Format: Article
Language:English
Subjects:
Alloys
Carbon
Microstructure
Transmission electron microscopy
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Summary:Lath martensite is the dominant microstructural feature in quenched low-carbon Fe-C alloys. Its formation mechanism is not clear, despite extensive research. The microstructure of an Fe-0.05 C (wt.%) alloy water-quenched at various austenitizing temperatures has been investigated using transmission electron microscopy and a novel lath formation mechanism has been proposed. Body-centered cubic {112}〈111〉-type twin can be retained inside laths in the samples quenched at temperatures from 1050 °C to 1200 °C. The formation mechanism of laths with a twin substructure has been explained based on the twin structure as an initial product of martensitic transformation. A detailed detwinning mechanism in the auto-tempering process has also been discussed, because auto-tempering is inevitable during the quenching of low-carbon Fe-C alloys. The driving force for the detwinning is the instability of ω-Fe(C) particles, which are located only at the twinning boundary region. The twin boundary can move through the ω ↔ bcc transition in which the ω phase region represents the twin boundary.
ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-018-32679-6