Three-dimensional characterization of bainitic microstructures in low-carbon high-strength low-alloy steel studied by electron backscatter diffraction

Journal Article · Wed May 15 04:00:00 EDT 2013 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2013.02.009· OSTI ID:22285046

Kang, J. S. ^[1]; Seol, Jae-Bok ^[2]; Park, C. G. ^[1]

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1. Department of Materials Science and Engineering, POSTECH, Pohang 790-784 (Korea, Republic of)
2. Max-Planck-Institut für Eisenforschung, Max-Planck-Str. 1, D-40237 Düsseldorf (Germany)

We investigated the microstructural evolution of high strength low alloy steel, Fe–2.0Mn–0.15Si–0.05C (wt.%), by varying the continuous cooling rates from 1 K/s to 50 K/s using three-dimensional electron backscatter diffraction and transmission electron microscopy. Granular bainitic microstructure was prevalent under a slow cooling rate of 1–10 K/s, while lath-type bainite was dominant at a high cooling rate of 50 K/s. The acicular ferrite that was the major microstructure under the intermediate ranges of cooling rates between 10 K/s and 30 K/s was tangled with each other, leading to a three-dimensional interwoven structure with highly misoriented grains. Because of the formation of three-dimensional structures, we propose that the terms “acicular ferrite” and “bainitic ferrite,” which are currently used in steel, be replaced by the terms “interwoven acicular bainite” and “lath bainite,” respectively. Moreover, we also confirmed that the cooling rate is an important factor in determining whether bainitic microstructures occur in the form of granular bainite, interwoven bainite, or lath bainite. - Highlights: • The morphology of bainitic grains was characterized by 3D-EBSD. • The ‘interwoven bainite’ and ‘lath bainite’ were suggested. • Interwoven bainite consisted of lenticular plates that were interlinked in 3D regime. • The packets of lath bainite were aligned in a specific direction.

• OSTI ID: 22285046
• Journal Information: Materials Characterization, Journal Name: Materials Characterization Vol. 79; ISSN 1044-5803; ISSN MACHEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BAINITE
CARBON
ELECTRON DIFFRACTION
ELECTRONS
FERRITE
LOW ALLOY STEELS
MICROSTRUCTURE
MORPHOLOGY